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BLD2018-1622 APPROVED STORMWATER REPORTSTORMWATER SITE PLAN Highway 99 Edmonds Edmonds, WASHINGTON In li�SFIONAL 16 2 - I Co-2--2— RESUB NOV 119 2019 BUI E ARTM ENT Mo S %N& PE Dp N 0' COMPLIES WITH APPLICABLE Cill M CODE a �271-�3,�I'-2,219 k7l'j STORMWATER SITE PLAN Table of Contents PROJECT SITE MAP ................................................................................................................................ 3 PROJECT OVERVIEW .............................................................................................................................. 4 DESIGNCRITERIA ............................................................................................................................... 4 SITELOCATION ................................................................................................................................... 5 CONDITIONS AND REQUIREMENTS SUMMARY ............................ i ...................................................... 6 EXISTING CONDITIONS ....................................................................................................................... 6 PRE -DEVELOPMENT STORMWATER RUNOFF .................................................................................... 7 MINIMUMREQUIREMENTS ............................................................................................................... 8 DEVELOPED CONDITIONS ................................................................................................................ 13 POST -DEVELOPMENT STORMWATER RUNOFF ............................................................................... 15 DRAINAGE SYSTEM DESCRIPTION AND PROBLEM DESCRIPTIONS .................................................. 15 MITIGATION OF EXISTING OR POTENTIAL PROBLEMS .................................................................... 15 OFF -SITE ANALYSIS REPORT ................................................................................................................ 16 UPSTREAM ANALYSIS: ...................................................................................................................... 16 DOWNSTREAM ANALYSIS: ............................................................................................................... 16 WATERSHED..................................................................................................................................... 19 PERMANENT STORMWATER CONTROL PLAN .................................................................................... 29 EXISTINGSITE HYDROLOGY ............................................................................................................. 29 DEVELOPED SITE HYDROLOGY ......................................................................................................... 29 HYDROLOGIC MODELING ................................................................................................................. 29 FLOW CONTROL SYSTEM ................................................................................................................. 29 FLOW CONTROL BMP'S .................................................................................................................... 30 WATER QUALITY TREATMENT SYSTEM ........................................................................................... 32 DETENTION VAULT MAINTENANCE ................................................................................................. 34 100-YEAR FLOOD/OVERFLOW CONDITION ..................................................................................... 36 CSWPPP ANALYSIS AND DESIGN ......................................................................................................... 37 SPECIAL REPORTS AND STUDIES ......................................................................................................... 47 OTHERPERMITS .................................................................................................................................. 47 APPENDIX: A — WWHM DATA AND OUTPUT .......................................................................... 48 B — BMP INFEASIBILITY .......................................................................................... 80 C— OPERATION AND MAINTENANCE MANUAL ................................................... 91 D — GEOTECHNICAL ENGINEERING REPORT .......................................................... 97 NAVIX Highway 99 Edmonds — Edmonds, WA Page 2 STORMWA TER SITE PLAN PROJECT SITE MAP E__ ';;'0000, pt run-on Intercept run-on Stormwater Reroute upstream detention vault run-on to existing storm system 1-/i ,9/71va 'Y99 a � IQ I Connection to existing storm system from detention system Figure 1: Project Site Map Total Project Area: 62,361 SF (1.44 acres) Total Proposed Hard Surfaces: 58,971 SF (1.35 acres) Proposed Pollution Generating Hard/impervious Surface: 1,157 SF (0.03 acres) Proposed Pollution Generating Pervious Surface: 0 SF (0.00 acres) Existing Unmanaged Hard Surfaces: 0 SF (0.00 acres) Total Disturbed Area: 62,361 SF (1.44 acres) Average Slope: 5-35% Estimated Ultimate Infiltration Rate: N/A NRCS Soil Group: Alderwood-Urban Land Complex Soils (glacial till) Please see stormwater plans for conveyance system details and geotechnical report for soil pit and infiltration test locations. NAVIX Highway 99 Edmonds — Edmonds, WA Page 3 STORMWATER SITE PLAN PROJECT OVERVIEW The proposed development includes construction of a new 192-unit apartment building located at the NW corner of Highway 99 and 234 th Street SW in Edmonds, Washington, with associated driveway access, trash enclosure pad, landscaping areas, sidewalks, and utility connections. The proposed development will also include construction of a 33,853 CF stormwater detention vault to provide flow control. DESIGN CRITERIA The stormwater management facilities have been designed in accordance with the 2017 City of Edmond's Stormwater Management Code, which utilizes the 2014 Stormwater Management Manual for Western Washington and the City of Edmonds Stormwater Addendum. Table 1 below summarizes the City of Edmonds stormwater requirements. Duration Analysis: 2-year: Reduce to Y2pre-developed duration 50-year: Match pre -developed Water Quality Volume: N/A Water Quality Flow Rate: Full 2-year release rate from the detention facility* Downstream Analysis: Xmile *MGS rainfall data in Table 4-4 from the Stormwater Code Supplement to Edmonds Community Development Code Chapter 18.30 for stormwater management design Table 1: Jurisdictional Requirements Since the project results in greater than 5,000 SF of new plus replaced hard surface, the project is a Category 2 project site and shall comply with Minimum Requirements 1-9 of the City of Edmonds Stormwater Management Code. NAVIX Highway 99 Edmonds — Edmonds, WA Page 4 STORMWA TER SITE PLAN SITE LOCATION 99 Ranch Markel ph P SVI �E ?2811, St SW 228th Si SW 2280, St sw �?9'h �i sw ?3C Z31 �i W, hl� 1� i'�' f, !av 23�111 1. V, PROJECT SITE 5. Avrora MarkLtplace Bolit" ger Playfield Ballinger Loki! Park 238th St SW 2�Zfi S, V1 Edmount Island W All .1 lik Mathay-Ballinger Burlington Park Figure 2: Project Location Location: NW corner of Highway 99 and 234 th Street SW in Edmonds, WA (Snohomish County) Section, Township, Range: SW 1/4, NE 1/4, SEC. 31, TOWNSHIP 27N, RANGE 04E, W.M. Parcel/Tax Lot: 00576700002002 Size: Approximately 1.37 acres (Full parcel); Approximately 1.44 acres (Total on- and off -site area of disturbance) City, County, State: Edmonds, Snohomish County, Washington Zoning: General Commercial (CG) NAVIX Highway 99 Edmonds — Edmonds, WA Page 5 STORM WATER SITE PLAN CONDITIONS AND REQUIREMENTS SUMMARY EXISTING CONDITIONS The proposed project is located at the NW corner of Highway 99 and 234 th Street SW in Edmonds, Washington (Snohomish County). The project site (Parcel #00576700002002) is approximately 1.37 acres and is currently undeveloped, containing full-grown evergreen trees and underbrush. Stormwater run-on from the Breve Condominiums site to the west is conveyed through existing storm drainage infrastructure across the site to the existing city storm system in Highway 99. See Figure 3 for the Existing Conditions Map. 1, - , - 1 �' � y N.F % Active storm pipe LAI 4'! t, conveys runoff from t Breve Condominiums site J, lyi, 99 77- Surface storm discharge from west Existing pipe outfall connection to existing storm main Figure 3: Existing Conditions Map Aw- Inactive storm line from north The site is bounded by 234th Street SW to the south, SR-99 (Aurora Avenue N) to the east, the Community Health Center of Snohomish County Edmonds to the north, and a parking lot for residential apartments to the west. The property slopes from west to east at a range of approximately 5%-35%. The high point of the site is at approximately elevation 430 feet along the west side of the property. The low point of the site is at approximately elevation 406 feet in the northeast corner of the property. The site contains areas of landslide and erosion hazards, per City of Edmonds GIS critical areas map (Figure 7). NAVIX Highway 99 Edmonds — Edmonds, WA Page 6 STORMWATER SITE PLAN The following soil conditions are based on the geotechnical report by Zipper Geo Associates, dated November 20, 2018 (Appendix D). The soil on site was classified as Alderwood group soils which belong to hydrologic soil group C. Findings report topsoil underlain by dense, gray -brown, silty sand with trace gravel extending to approximately 5 to 7 feet below existing site grade (weathered glacial till). Dense to very dense silty sand with variable amounts of gravel extending to 30 feet below existing grade was found below the weathered till. This soil is identified as glacial till. Other borings ranging in depths from 20 to 40 feet generally encountered similar soil conditions. Groundwater was not encountered at any depth in any of the borings completed. Please refer to the geotechnical report for more details. PRE -DEVELOPMENT STORMWATER RUNOFF An on -site field investigation was performed on November 2, 2018, to verify if there are active sewer or stormwater utilities entering the site from adjacent properties, as indicated by the project survey. The site investigation was performed by exposing existing sewer and stormwater manholes and running a utility camera upstream from the manhole structures. The site investigation determined that stormwater flows enter the subject site from the Breve Condominiums development directly west of the site. Stormwater flows were observed entering the site from an 8-inch PVC pipe, which was connected to a catch basin under the Breve Condominium's parking lot. The catch basin has been covered with pavement and is not visible at the surface. The source of the flows is unknown. Additionally, the survey indicates the presence of a 3-inch surface outfall from the Breve Condos site. This could not be located in the field due to the heavy brush. The upstream flows will be intercepted and rerouted around the proposed development. The existing 8-inch storm pipe noted on the survey from the north direction was determined to be inactive and abandoned. Surface runoff from the existing site is collected by a system of catch basins along Highway 99 to the east which connect to the existing storm line running along the highway. NAVIX Highway 99 Edmonds — Edmonds, WA Page 7 STORM WATER SITE PLAN MINIMUM REQUIREMENTS Does die project restilt in 2,000 square feet, or greater, of new plus replaced hard surface area? OR Does the land disturbing activity total 7,000 square feet or L 7caterl "Yes No I Minimum Requirements No, I through 5 apply Minimum Requirement No. 2 applies I Next QueAion Does the project add 5,000 square feet or more of new plus replaced hard surfaces.? OR Convert 0.75 acres or more of vegetation to laAn or landscaped areas? OR Convert 2.5 acres or more ofnative vegetation to pasture? I yes I Is this a road related project? All Minimum Requirements yes apply to the new and replaced hard surfaces and converted vegetation areas. All Minimum Requirements apply to die new hard Surfaces and converted veggdation. areas, No Yes Does the project add No 5,000 square feet or more of new hard surfaces? Yes Do new hard surfaces add 50% or more to the existing hard surfaces within the project limits? No Figure 4: Minimum Requirements Flowchart No additional requirements. As required by the 2017 City of Edmonds Stormwater Code, all Minimum Requirements apply to the new and replaced hard surfaces and converted vegetation areas. NAVIX Highway 99 Edmonds — Edmonds, WA Page 8 STORMWATER SITE PLAN Minimum Requirement #1: Preparation of Stormwater Site Plans The City shall require a Stormwater Site Plan from all projects meeting the thresholds in ECDC 18.30.060.C. Stormwater Site Plans shall use site -appropriate development principles to retain native vegetation and minimize impervious surfaces to the extent feasible. Stormwater Site Plans shall be prepared in accordance with Chapter 3 of Volume 1 of the SWMMWW and the requirements in the Edmonds Stormwater Addendum. Response: A stormwater site plan has been preparedfor this development. The stormwater site plan includes the design drawings and this report. The site will be landscaped to meet the City of Edmonds requirements. Site Low Impact Development (LID) techniques are notfeasible due to lack of infiltrating soils on site. Please see geotechnical report. Minimum Requirement #2: Construction Stormwater Pollution Prevention Plan (SWPPP) All development projects are responsible for preventing erosion and discharge of sediment and other pollutants into receiving waters. Compliance with this minimum requirement can be achieved for an individual site if the site is covered under Ecology's General NPIDES Permit for Stormwater Discharges Associated with Construction Activities and fully implementing the requirements of that permit. A Construction SWPPP is required for all projects which a) result in 2,000 square feet or more of new plus replaced hard surface area, b) where a structure with an exterior hard surface area of at least 2,000 square feet is being demolished, c) which disturb 7,000 square feet or more of land, or d) when the site falls within the Earth Subsidence Landslide Hazard Area, Landslide Hazard Area or steep slope critical area. Response: A Construction SWPPP has been prepared and is included in this report. A full Construction SWPPP report that will be utilized by the contractor will be submitted with this permit submittal package as a separate document. Minimum Requirement #3: Source Control of Pollution All known, available and reasonable source control BIVII)s must be required for all projects approved by the City. Source control BIAPs must be selected, designed, and maintained in accordance with Volume IV of the SWMMWW. Response: Source Control BMPs have been evaluatedfor applicability to this project. The following shall be implemented by the Owner: S402 BMPs for Commercial Animal Handling Areas Description of Pollution Sources: The project will include a small (approximately 300 SF) pet relief area on an upper level of the building. The area will include artificial gross and will drain to the storm system. Potential source of pollutants is pet waste. NAVIX Highway 99 Edmonds — Edmonds, WA Page 9 STORMINATER SITE PLAN Pollutant Control Approach: Owner will provide a pet waste bag station for tenant use. The site will be regularly cleaned area and waste will be properly disposed of as needed. A spray hose will not be used to clean in areas with potential stormwater contaminants at risk of draining to the storm system. Runofffrom the area will be filtered prior to draining to the detention voult. Filtering to be provided either by a sandfilter beneath the pet area or an equivalentfilter system. S411 BMPs for Landscaping and LawnlVegetation Management Description of Pollution Sources: Landscaping on the subject site will include planters on the elevated building structure (plaza), a small at-grode planting strip to the west of the building that will be landscaped with trees and shrubs, and a small ot-grode planter area to the southeast corner of the building, which will mostly contain utility vaults and a small amount of shrubs and plantings. Potential sources of pollutants ore use of pesticides andfertilizers. Pollutant Control Approach: Utilize nofertilizer or pesticides for the at -grade planters around the building perimeter. If fertilizers or pesticides are to be used for the on -site planters, provide on a per -plant basis and minimize the opportunityfor spills onto surfaces that drain to the storm drainage system. Clean up any spilled pesticides orfertilizers. Trash Enclosure Area Description of Pollution Sources: An outdoor, uncovered trash enclosure area will be provided for storage of tenant trash, recycling, and yard waste (e.g. compost) bins. Potential pollutants will be the waste materials from residential uses. Pollutant Control Approach: The owner will provide covered 4-yord trash and recycling bins provided by Republic Services. The trash bins will be serviced daily Monday through Friday. The bins are to be well maintained and replaced if damaged. The trash enclosure area must be cleaned of any materials thatfallfrom the containers. Signoge and instructions shall be provided to tenants by that describe what materials may and may not be accepted by each bin. Minimum Requirement #4: Preservation of Natural Drainage Systems and Outfalls Natural drainage patterns shall be maintained, and discharges from the project site shall occur at the natural location, to the maximum extent practicable. The manner by which runoff is discharged from the project site must not cause a significant adverse impact to downstream receiving waters and down gradient properties. The discharge must have an identified overflow route that is safe and certain and leads to the ultimate outfall location (such as a receiving water or municipal drainage system). All outfalls require energy dissipation. To demonstrate compliance with this core requirement, all projects shall submit an off -site qualitative analysis. If an existing problem (or potential future problem after development) is identified, mitigation will be required to prevent worsening of that problem. A quantitative analysis may be required for any project deemed to need additional information or where the project proponent or the City determines that a quantitative analysis is necessary to evaluate the off -site impacts or the capacity of the conveyance system. Per the Edmond's Stormwater Addendum, existing upstream flows must be accommodated without NAVIX Highway 99 Edmonds — Edmonds, WA Page 10 STORMWATER SITE PLAN causing erosion or flooding impacts. Upstream flows shall not be routed through the project's conveyance, treatment, or retention/detention systems, unless those systems are sized to control those flows. Upstream flows that are collected and routed through or around the site in a separate conveyance shall be dispersed at the clowngradient property line, if feasible, or discharged at a project outfall (or outfalls) in a manner that does not violate the criteria below or cause the capacity of a conveyance system to be exceeded. Response: Natural drainage systems and outfalls will be maintained with the development of this site. Roof drainage will be routed via roof drain leaders to the detention vault. The vault will discharge to the existing drainage system located in Highway 99. Proposed grades allowfor runoff from non -roof areas to flow to the existing outfall of the project site. Upstream flows will be routed around the proposed building into the existing storm system in 234 th Street SW, which connects to the storm system in Highway 99, where the upstream flows currently connect. Please see Developed Conditions section of this report for more detail. Minimum Requirement #5: On -Site Stormwater Management On -site Stormwater Management BMPs are required in accordance with the following project thresholds, standards, and lists to infiltrate, disperse, and retain stormwater runoff on -site to the extent feasible without causing flooding or erosion impacts. Category 2 project sites that discharge directly or indirectly to the City's MS4 shall use On -Site Stormwater BMPs from List No.2 for all new plus replaced hard surfaces and land disturbed. Response: On -site stormwater management BMPs have been evaluated in accordance with the City of Edmonds stormwater code requirements. According to the project geotechnical report, the existing on -site soils are glacial till soils and are not suitable for infiltration. Please refer to Appendix B for BMP infeasibility. Roof drainage will be collected and routed through a detention vault located below the parking garage prior to discharge to the existing storm drainage system located in Highway 99. Sidewalk improvements in the right of way along Highway 99 cannot be mitigated with On -Site Stormwater Management BMPs due to the inability to infiltrate below the sidewalk and inability to route runofffrom these areas to the detention vault, since these areas are located below the vault riser. The landscape areas will be compost amended in accordance with Stormwater Manual requirements. Minimum Requirement #6: Runoff Treatment The following require construction of stormwater treatment facilities: • Projects in which the total of pollution -generating hard surface (PGHS) is 5,000 square feet or more in a threshold discharge area of the project, or • Projects in which the total of pollution -generating pervious surfaces (PGPS) — not including permeable pavements — is 0.75 acres or more in a threshold discharge area, and from which there will be a surface discharge in a natural or man-made conveyance system from the site. • Phosphorus treatment shall be required for projects draining to Hall Creek and Lake Ballinger. NAVIX Highway 99 Edmonds — Edmonds, WA Page 11 STORMWATER SITE PLAN Response: The proposed onsite Pollution Generating Impervious Surfaces (PGIS) will be 1, 117 SF of trash enclosure and driveway area. A total offsite area of 4,958 SF of pollution generating impervious surface and 100 SF of non -pollution generating impervious surface will be collected. These surfaces will be routed to a DOE approved water quality treatment facility that will provide basic plus phosphorus treatment. Flow will then be routed to the proposed stormwater detention vaultfor eventual discharge to the City's stormwater system. All roof coverings, including pavers, planters, guardrails, pergola, aggregate, waterproofing at the courtyard will be non -pollution generating. All mechanical units to include internal spill containment devices. Minimum Requirement #7: Flow Control Flow control is required on projects meeting the thresholds summarized below to reduce the impacts of stormwater runoff from hard surfaces and land cover conversions. Standard Flow Control Requirement (applies to discharges directly or indirectly to the City's MS4, except for projects that meet the direct discharge requirements outlined in "a" above): Stormwater discharges shall match developed discharge durations to pre -developed durations for the range of pre - developed discharge rates from 50 percent of the 2-year peak flow up to the full 50-year peak flow. The pre -developed condition to be matched shall be a forested land cover. Response: Flow control will be provided by utilizing a detention vault located below the parking level. On -site roof drainage will be collected and routed to the detention vault prior to discharge to the storm drainage system located below Highway 99. Approximately 0.11 acres of impervious area and 0. 09 acres of pervious area will bypass the vault. These areas will be offset by 0. 11 acres of offsite impervious area and 0.09 acres of pervious area that will be routed to the vault. See the Developed Condition section, below, forfurther discussion. The detention vault is sized to meet discharge requirements for the entire redevelopment area in accordance with the 2014 Stormwater Management Manualfor Western Washington requirements utilizing continuous modelling with WWHM2012. Minimum Requirement #8: Wetlands Protection The requirements below apply only to projects whose stormwater discharges into a wetland, either directly or indirectly through a conveyance system. Response: This project does not discharge into a wetland. Minimum Requirement #9: Operation and Maintenance An operation and maintenance manual that is consistent with the provisions in Volume I and Volume V of the SWMMWW is required for proposed Stormwater Treatment and Flow Control BMPs/facilities. The party (or parties) responsible for maintenance and operation shall be identified in the operation and maintenance manual. For private facilities approved by the City, a copy of the operation and maintenance manual shall be retained on -site or within reasonable access to the site and shall be transferred with the property to the new owner. For public facilities, a copy of the operation and maintenance manual shall be retained in the appropriate department. A log of maintenance activity that indicates what actions were taken shall be kept and be available for inspection. NAVIX Highway 99 Edmonds — Edmonds, WA Page 12 STORM WATER SITE PLAN Response: See Appendix Cfor the Operation and Maintenance and the Permanent Stormwater Control Plan for detention vault maintenance. See the Detention Vault Maintenance section of the report under Flow Control BMPs for a detailed discussion for how the detention vault maintenance will be provided. A brief summary is provided below: The detention vault will be located below the P1 parking level, and will be inaccessible to typically - sized vactor trucks through the vehicle garoge access from 234th Street SW. The detention vault will be inspected annuallyfor a maintenance check and cleaned as needed to maintain performance. The vault will be cleaned by a voctor truck that will be parked outside the building, eitherfrom Highway 99 orfrom the Community Health parking lot to the north. The vactor trucks are equipped with300- at hoses that will be routed through a man door from Highway 99, up a short staircase, fo and through the vault top from the P1 level. The maintenance program described here was coordinated with Bravo Environmental, a firm that provides stormwater vault maintenance. DEVELOPED CONDITIONS The proposed development includes construction of a new 192-unit apartment building located at the NW corner of Highway 99 and 234 th Street SW in Edmonds, Washington, with associated driveway access, trash enclosure pad, landscaping areas, sidewalks, and utility connections. The proposed development will also include construction of a 33,853 CF stormwater detention vault to provide flow control. The total area of disturbance is 1.44 acres, comprised of 1.11 acres of roof area draining to detention, 0.10 pervious acres draining to detention, and 0.03 non -roof impervious acres draining to detention. There will be 0.09 acres of pervious area bypassing detention and 0.11 impervious acres bypassing detention. The 1.44 acres contributing to detention includes 0.11 acres off offsite impervious runoff collected from 234 th Street SW and 0.09 acres of pervious run-on area from the neighboring Breve Condos project to the west to serve as an area swap with on -site areas that bypass detention. The areas that bypass detention include sidewalk and planters in the right of way along Highway 99 that are located below the detention vault, the driveway ramp from 234 th Street SW, and the curb ramp at the intersection. See Figure 5 for a map of the proposed site areas for the developed condition. A trench drain is located along the property line at the top of the driveway ramp to collect trash enclosure and driveway runoff. Area drains are located along the building's west side to collect runoff from the pervious planter area between the building and the Breve Condo site. Note that a portion of the Breve Condo landscaped area adjacent to the property slopes toward the site and will be collected on site as mentioned in the paragraph above. The Pollution Generating Impervious Surfaces (PGIS) collected onsite will be 1,117 SF of trash enclosure and driveway area. Please see the Water Quality Treatment Section, under the Permanent Storm Water Control Plan section, below, for more information on the areas routed to water quality. NAVIX Highway 99 Edmonds — Edmonds, WA Page 13 STORMWATER SITE PLAN An approximately 300 SF pet relief area located on the building plaza area is considered PGIS and will be filtered prior to discharge to the detention tank. See Figure 5 for the Proposed Conditions Map. I FIQ ' LU VERIFIED PIPED RUN ON POTENTIAL PIPED RUN-ON PROPOSED STORM MAIN TOINTERCEPT RUN ON 'A9171v I- _�"5 4/ a .k 99 STORMWATER DETENTION VAULT OUTFALL To PUBLIC STORM ROOF TO DETENTION ISYSTEM i.11 AC PERMLIS TO DETENTION 0.10 AC IMPERVIOUS TO DETENTION 0.03 AC PERMUS BYPASS 0.09 AC IMPERVIOUS BYPASS 0.11 AC EPERVIOUS OFFSITE AREA TO DETENTION l 0.09 AC IMPERVIOUS OFFSITE AREA TO DETENTION F7 0.11 AC Figure 5: Proposed Conditions Map Table 2 below documents discharge areas for the proposed project. NAVIX Highway 99 Edmonds — Edmonds, WA Page 14 STORMWATER SITE PLAN Table 2: Threshold Discharge Areas Threshold Discharge Area Existing Impervious Surface Existing Surface Area (AC) 0.06 Proposed Surface Area (AC) Existing Pervious Surface 1.38 Proposed Roof Area 1.11 Proposed Impervious Site Area to Detention 0.03 Proposed Pervious Site Area to Detention 0.10 Proposed Impervious Bypass 0.11 Proposed Pervious Bypass 0.09 Impervious Offsite Area to Detention 0.11 Pervious Offsite Area to Detention 0.09 Total Disturbed Area 1.44 1.44 POST -DEVELOPMENT STORMWATER RUNOFF The proposed system will include an approximately 33,853 CF detention vault located below the building's lowest level of parking, Level P1. The detention vault will include a control structure that will restrict flows off site from the vault to pre -historic forested conditions, in accordance with stormwater requirements. Rainfall on site will generally fall on roof structures and will be routed to the detention vault via roof drain leaders. Underground garage drainage will be collected by sanitary sewer catch basins and connected to sanitary sewer. A site investigation showed that an 8" PVC pipe currently carries run-on from Breve Condos to the west across the site to the city storm system in Highway 99. Because this existing pipe would conflict with the proposed building run-on will be intercepted west of the building and rerouted south via tightline pipe to the city storm main. See the Upstream Analysis section under Off -Site Analysis Report for a further discussion of upstream flows. Floor drains located within the parking garage will be connected to the sanitary sewer system. Floor drains will not be connected to the detention vault or storm drainage system. DRAINAGE SYSTEM DESCRIPTION AND PROBLEM DESCRIPTIONS There are no known problems with the drainage paths around the site. No downstream impacts from the proposed project are anticipated. MITIGATION OF EXISTING OR POTENTIAL PROBLEMS No existing or potential problems were identified as discussed above; therefore, mitigation is not warranted. NAVIX Highway 99 Edmonds — Edmonds, WA Page 15 STORM WATER SITE PLAN OFF -SITE ANALYSIS REPORT UPSTREAM ANALYSIS: A site investigation determined that stormwater flows enter the subject site from the Breve Condominiums development directly west of the site via an 8" PVC pipe connected to a catch basin under the Breve Condominium's parking lot. This catch basin has been covered with pavement and is not visible at the surface. The source of flows is not certain but appears to be roof and parking lot runoff from the Breve Condos development. In the existing condition this 8" PVC pipe travels across the subject site to the existing city storm system in Highway 99. In the developed condition these upstream flows will be intercepted west of the proposed building and rerouted south via tightline pipe around the proposed development. in addition, another existing 8-inch storm pipe to the north that is shown in the survey as running south to northeast has been determined to be inactive and abandoned. This pipe will be removed with the proposed development. DOWNSTREAM ANALYSIS: A formal downstream analysis has been completed in accordance with the City of Edmond's 2017 Stormwater Addendum. The downstream was completed on November 13, 2018. The temperature was approximately 50 degrees and sunny. The project site consists of one drainage sub -basin. Flows from the existing site are collected by a system of catch basins along Highway 99 to the east which connect to the existing storm line running along the highway that ultimately flows to an outfall on Lake Ballinger. The % mile location was on private property. Please see Figure 6 below. NAVIX Highway 99 Edmonds — Edmonds, WA Page 16 STORMWATER SITE PLAN _7 7i X mile downstream location 11WWW-7— 1vMMQvWP�- -- Figure 6: Downstream Analysis Path I qW �'. The downstream storm drainage system within % mile of the project site did not contain critical areas, per the City of Edmond's critical area map. Please refer to Figure 7 below. NAVIX Highway 99 Edmonds — Edmonds, WA Page 17 STORMWATER SITE PLAN RA.Afcc Ir fit fl on *M 00 U. > t, - - �] f =;, - L-L Figure 7: Critical Areas Map NAVIX Highway 99 Edmonds — Edmonds, WA Page 18 STORMWATER SITE PLAN WATERSHED The projects site is located within the Halls Creek Watershed. Jpf� I I I.- L Z7 -- I-Ir_- r 'w6stqate Pond W L L L 1 —1 pew#4 T- 1, jr 1-1-11114411,' '11 -7 - -1 -, PROJECT SITE Lake Halls Cree�k ---------- Figure 8: Watershed Map Yp i IT —7- NAVIX Highway 99 Edmonds — Edmonds, WA Page 19 STORMWATER SITE PLAN I # � Photo I Description I w4LAON 2 r7ll View from the entrance to Breve Condominiums on 234'h St SW looking east. Existing storm water system conveys easterly down 234 th St SW. View from southeastern corner of project site looking east. Drainage is conveyed to a closed -grate catch basin located in the western -most drive aisle in Highway 99 at its intersection with 234 1h St SW. NAVIX Highway 99 Edmonds — Edmonds, WA Page 20 STORMWA TER SITE PLAN Is View from the project site's frontage with Highway 99 looking northeast. Drainage is conveyed northeasterly in the western -most drive aisle for the full length of the site's frontage with Highway 99 through a series of closed - grate catch basins. View from the curb cut at the frontage of Highway 99 looking northeast. Drainage is conveyed northeasterly through a closed -grate catch basin adjacent to the curb cut located at the frontage of Highway 99. At this location, there is an existing curb cut to allow surface water from the project site into the open -grate catch basins located in the shoulder of Highway 99. NAVIX Highway 99 Edmonds — Edmonds, WA Page 21 STORMWATER SITE PLAN MIMA Is 90� View from the west side of Highway 99 adjacent to the Edmonds Community Health Clinic (CHC). Drainage is conveyed to a closed -grate catch basin located in the western -most drive aisle of Highway 99 adjacent to the Edmonds CHC. View from the east side of Highway 99 looking southeast. Drainage conveys easterly across Highway 99 to a closed -grate catch basin located in the eastern -most drive aisle of Highway 99 just north of the entrance to Pacific Park Apartment Homes. NAVIX Highway 99 Edmonds — Edmonds, WA Page 22 STORMWATER SITE PLAN I I M NAVIX Highway 99 Edmonds — Edmonds, WA View looking south from the northeast corner of the Pacific Park Apartment Homes parking lot and Another Castle Video Games. Drainage is conveyed southeasterly to an open - grate catch basin located in a landscape area behind Another Castle Video Games. View from 7811234 1h St SW looking south. Drainage is conveyed southerly through private property to an open -grate catch basin located on the northern side of 234 th St SW. Page 23 STORM WATER SITE PLAN View looking south from the south side of 234th St SW looking south. Drainage is conveyed southerly through private property from 234t' St SW to 236 th St SW. The X mile downstream location is on this length of pipe. .7 View looking south on north side of 236 th St. Drainage is conveyed southerly, past the % mile 10 downstream location, to a solid -lid manhole located in the entrance to the parking lot for North Haven Manor Apartments. NAVIX Highway 99 Edmonds — Edmonds, WA Page 24 STORMWATER SITE PLAN LM 12 View from 236 1h St SW looking east. Drainage is conveyed southerly to a solid -lid manhole located in the center of 236th St SW at the entrance to the parking lot of North Haven Manor Apartments. View from north side of 236 th St SW looking east. Drainage is conveyed easterly to an open -grate catch basin located at 7731 236 th St SW. NAVIX Highway 99 Edmonds — Edmonds, WA Page 25 STORMWATER SITE PLAN *a[ I Mik AN&AL . j rip fowl IN 14 View from the intersection of 76 th Ave W and 236 th St SW. Drainage is conveyed easterly to a solid -lid manhole located in the intersection of 76 th Ave W and 236 th St SW. View from 23439 76 th Ave W looking east. Drainage is conveyed northerly to a solid -lid manhole located in the bike lane of 76 1h Ave W across the street from 23439 76 th Ave W. NAVIX Highway 99 Edmonds — Edmonds, WA Page 26 STORMWATER SITE PLAN 15 16 View from west side of 75 th Ave W looking east. Drainage is conveyed across private property to an open - Open -grate grate catch basin located at catch basin 2345675 th Ave W. From here, drainage is conveyed th easterly across 75 Ave W through residential area. View from west side of 74" Ave W looking east. Drainage is conveyed to an open -grate catch basin th located at 23510 74 Ave W NAVIX Highway 99 Edmonds — Edmonds, WA Page 27 STORMWATER SITE PLAN 17 View from east side of 74 1h Ave W looking east toward Lake Ballinger. Drainage travels through residential area and outfalls to Lake Ballinger. NAVIX Highway 99 Edmonds — Edmonds, WA Page 28 STORM WATER SITE PLAN PERMANENT STORMWATER CONTROL PLAN EXISTING SITE HYDROLOGY The following table summarizes the surface area of the existing site conditions as input into WWHM. Total site area is indicative of the contributing area to the proposed vault. Table 3: Pre -Developed Conditions 1.44 1 Soil Type C, Forest I Moderate DEVELOPED SITE HYDROLOGY The following table summarizes the surface area of the proposed site conditions as input to WWHM. Table 4: Developed Conditions 0.19 Soil Type C, Lawn Flat 1.11 Rooftops Flat 0.14 Sidewalks/Driveway Flat HYDROLOGIC MODELING The hydrologic analysis for this project was performed using Western Washington Hydrology Model (WWHM2012), based on matching flow durations. MGS rainfall data was used to model the site runoff and size the stormwater facility. FLOW CONTROL SYSTEM The proposed flow control facility was designed in accordance with the 2012 DOE stormwater manual. Pre -developed conditions are modeled as forested for all areas within the limits of disturbance. WWHM 2012 was used for flow control calculations. The proposed detention vault will have a live storage depth of 5.75 feet, a width of 39.25 feet, and a length of 150 feet. The basin data and results from the WWHM 2012 model are provided in Appendix A. Precleveloped and developed flows are shown in Table 5 below. Table 5: Predeveloped and Developed Flows lbqlWty 2 year Predeveloped Flow -IFKAitigated (CFS) 0.0245 Flow (CFS) 0.0123 10 year 0.0500 0.0265 25 year 0.0596 0.0379 50 year 0.0654 0.0488 100 year 0.0702 0.0624 NAVIX Highway 99 Edmonds — Edmonds, WA Page 29 STORMWATER SITE PLAN The 100-year unmitigated developed flow is 0.7456 CFS, which is the minimum flow capacity that should be provided in the piped network downstream from the detention system. The proposed outfall pipe is a 12-inch diameter ductile iron pipe with 1.86% slope to the main. To verify capacity, a 12-inch pipe at 0.5% slope was checked for adequacy. As shown in Figure 8 below, the 12-inch pipe at 0.5% slope can provide conveyance capacity up to 2.70 CFS flowing near full at 0.5%., which exceeds the 100-year unmitigated flow from the site of 0.7456 CFS. Therefore, the proposed outfall provides adequate capacity to handle the 100-year, 24- hour uncletained peak flow from the developed site. MI.ve For For FF]cyw rSolve 9ow,rate gow'rate cfs Pipe Shape- Circular Slope ft/ft Select 14anning s n 10.0130 Select Depth of Row In 11 1.5&N [liametei In 112.&DN Select Plot elocih, fps 3.48a5 outp Area ft2 0. 7&54 Critic�al Penmeter in 37,Ga9l Wetted Area ft2 0.7742 Rating Wetted Perimeter in 32.7655 F-05 t4yclraulic Radiuc in 3.4025 Cancel Percern f'u" 95.8-333 Help Figure 9: Manning's Calculation for 12-Inch Pipe FLOW CONTROL BMP'S A BMP feasibility investigation was conducted per City of Edmond's Stormwater Addendum, Appendix A — On -Site Stormwater Management BMP Infeasibility Criteria with reference to the 2014 Stormwater Management Manual for Western Washington (SWMMWW). This investigation was performed to assess on -site soil condition and infiltration feasibility. NAVIX Highway 99 Edmonds — Edmonds, WA Page 30 STORMWATER SITE PLAN A geotechnical engineering report has been prepared for the proposed apartment complex, conducted by Zipper Geo Associates, LLC (Appendix D). This report describes geotechnical engineering recommendations for this site based on the surface and subsurface conditions. Borings found dense glacial till soils with low infiltration rates of depths 31-40 feet below existing grade, and ZGA concludes that infiltration is infeasible. Each stormwater BMP provided in the City of Edmond's Stormwater Addendum has been evaluated for applicability to this project site (Appendix B). It has been determined that a stormwater detention vault is required for on -site stormwater flow control. A vault has been sized using the Western Washington Hydrology Model (WWHM) per City of Edmonds requirements (using WSDOT data) and a report has been generated through the software (Appendix C). The full evaluation of Flow Control BMP's is located in Appendix B. An abbreviated version is included below for reference. v"& Post- Yes On -site disturbed areas that are not covered by Construction Soil structure will be amended with compost or Quality and replaced with topsoil meeting Post -Construction Depth Soil Quality and Depth requirements. Full Dispersion No A minimum flow path cannot be met due to the zero -lot line development project. Downspout Full No The project site contains dense till soils that have Infiltration been determined to be impermeable by the project Systems geotechnical engineer's investigation. According to the geotechnical report (Appendix A), the on -site borings indicated very dense glacial till to the depth of about 31-40 feet below existing site grade. Proposed final grades will not allow for 3 feet or more of permeable soil. Bioretention or No Geotechnical investigation has determined that on - Rain Gardens site soils are impermeable, with measured rates well below the 0.3 inches/hour minimum rate required. Downspout No The minimum flowpath required is not available at Dispersion this site due to the nature of a zero -lot line Systems development. Additionally, on -site soils have been determined to be impermeable by the geotechnical engineer's on -site soils investigation. NAVIX Highway 99 Edmonds — Edmonds, WA Page 31 STORMWATER SITE PLAN Perforated Stub- No Geotechnical investigation shows no permeable Out Connections soils on site. Detention Vaults Yes A detention vault has been sized using WWHM and Pipes 2012 to account for the lack of other On -Site Stormwater Management BMPs (Appendix A). Full Dispersion No Geotechnical investigation shows no permeable soils on site. BMP Feasible? Yes/No Reason(s) for Infeasibility Permeable AilL No Refer to geotechnical report, Appendix D. Pavement Geotechnical investigation reports soils with low soil infiltration rate of .05-.15 inches per hour. Bioretention or No The impermeable nature of the soils would lead to Rain Gardens flooding and erosion concerns on site. Sheet Flow No The required vegetated buffer is not available at Dispersion this site. Sheet flow dispersion would lead to flooding and erosion concerns due to the impermeable nature of the existing soils. Concentrated No The required flowpaths cannot be provided at this Flow Dispersion site. Runoff will not be able to drain into the dense till soil. Detention Vaults Yes A detention vault has been sized using WWHM and Pipes 2012 to account for the lack of other On -Site Stormwater Management BMPs (Appendix A). WATER QUALITY TREATMENT SYSTEM The proposed water quality facilities were designed in accordance with the City of Edmond's stormwater code and the 2014 DOE stormwater manual. As summarized in the Minimum Requirements Section of this report, above, phosphorus control is required for this project. A proprietary filter system was selected to provide water quality treatment for the site in a single manhole. Runoff will be routed to a StormlFilter single cartridge system which can treat approximately 0.24 acres total. A detail for the StormFilter has been provided in Appendix F. The WWHM inputs for the system are as shown: NAVIX Highway 99 Edmonds — Edmonds, WA Page 32 STORMWATER SITE PLAN Basin 1 Bypass: No GroundWater: No Pervious Land Use acre A B, Lawn, Mod 0.09 Pervious Total 0.09 Impervious Land Use acre ROADS MOD 0.05 DRIVEWAYS MOD 0.09 SIDEWALKS MOD 0.01 Impervious Total 0.15 Basin Total 0.24 The following results from WWHM were utilized to size the appropriate StormFilter System: Water Quality 24 hour Volume (ac-ft) Standard Flow Rate Ws) F050-2-7-21 M-Line BMP Standard Flow Rate (cfs) The WWHM results show an on-line target flow rate of 0.0152 CFS (6.82 gpm). The proposed StormFilter system with one cartridge treats 0.019 CFS (8.53 gpm). Refer to Appendix F for detail drawings of the Stormfilter System. NAVIX Highway 99 Edmonds — Edmonds, WA Page 33 STORM WATER SITE PLAN DETENTION VAULT MAINTENANCE The proposed development will include an approximately 33,853 CF cast -in -place detention vault below the lowest parking level. The parking slab will have a finished grade of 409.84 and will be accessible through a man -door and half -floor stairway from the Highway 99 building frontage. The detention vault will not likely accumulate appreciable amounts of material because the vast majority of runoff collected and stored will be from clean roof surfaces. However, periodic maintenance may be required, including cleaning with a vactor truck. A typical vactor truck will not be able to access the vault through the vehicle entry from 234 th Street SW due to limited height restriction. The proposed maintenance of the vault will occur as necessary by parking the vactor truck outside the building and running the vactor hose to the vault through the building man -door on Highway 99. Per discussions with Bravo Environmental Services, the vactor trucks can perform cleaning operations by extending the hose up to 300 feet. The vactor hose is flexible and can be run through the man -door and half -floor stairway with no issues. The vactor truck may park in one of two locations: a. Option 1: Along Highway 99 This location will require a temporary 1-lane closure and permits from WSDOT and will be done during off-peak traffic hours. The vactor truck will park in the southbound lane nearest the man -door that leads into the building stairwell. The hose from the vactor truck will be extended through the man -door and up the half -floor stairway to the parking garage. From here, the hose will be directed towards the stormwater detention vault and enter through the 5' x 10' access lid. At a maximum, 250 feet of vactor hose will be utilized to service the furthest corner of the detention vault. See Figure 10. b. Option 2: In the Community Health parking lot The location will require approval from Community Health and will be done during off-peak or closure hours. The vactor truck will park in the parking spaces closest to the existing trash enclosure located on the southern side of the south -most driveway of the Community Health building. The vactor hose will be run around the northeast building corner and through the same man -door as Option 1. At a maximum, 290 feet of vactor hose will be required to service the furthest corner of the detention vault. See Figure 10. GRE 234 1h LLC' the project owner, must obtain approval from Community Health to allow this method. NAVIX Highway 99 Edmonds — Edmonds, WA Page 34 + . ~ ' w - ---�`m STORM WATER SITE PLAN 100-YEAR FLOOD/OVERFLOW CONDITION The stormwater conveyance system for this project has been designed to address all storm events, including thelOO-vear, 24'hourstornn,inaccondancevvithcononnonindusLrypnactices.P|easesee FIRM map shown below. The project site is in ZoneX, which isoutside the 500'yearf|uodp|ein. Figure 11: FIRM Map NAV|X Highway 93Edmonds — Edmonds, \NA Page36 STORMWA TER SITE PLAN CSWPPP ANALYSIS AND DESIGN All erosion and sediment control measures shall be governed by the requirements of the City of Edmonds. A temporary erosion and sedimentation control plan will be prepared to assist the contractor in complying with these requirements. The Erosion and Sediment Control (ESC) plan will be included with the construction plans. Element 1: Preserve Vegetation/Mark Clearing Limits • Before beginning land disturbing activities, including clearing and grading, clearly mark all clearing limits, sensitive areas and their buffers, and trees that are to be preserved within the construction area. • Retain the cluff layer, native top soil, and natural vegetation in an undisturbed state to the maximum degree practical. • Plastic, metal, or fabric fence may be used to mark the clearing limits. [Note: the difference between the practical use and proper installation of silt fencing and the proper use of clearing boundary fencing.] • If it is not practical to retain the cluff layer in place, then stockpile it on -site, cover it to prevent erosion, and replace it immediately when you finish disturbing the site. Element 2: Establish Construction Access • Limit construction vehicle access and exit to one route, if possible. • Stabilize access points with a pad of quarry spalls, crushed rock, or other equivalent BMPs, to minimize tracking sediment onto roads. • Locate wheel wash or tire baths on site, if the stabilized construction entrance is 2014 Stormwater Management Manual for Western Washington Volume 11 - Chapter 3 - Page 237 not effective in preventing tracking sediment onto roads. • If sediment is tracked off site, clean the affected roadway thoroughly at the end of each day, or more frequently as necessary (for example, during wet weather). Remove sediment from roads by shoveling, sweeping, or pick up and transport the sediment to a controlled sediment disposal area. • Conduct street washing only after sediment is removed in accordance with the above bullet. • Control street wash wastewater by pumping back on site or otherwise preventing it from discharging into systems tributary to waters of the State. • Minimize construction site access points along linear projects, such as roadways. Street washing may require local jurisdiction approval. Element 3: Control Flow Rates Protect properties and waterways downstream of development sites from erosion and the associated discharge of turbid waters due to increases in the velocity and peak volumetric flow rate of stormwater runoff from the project site, as required by local plan approval authority. NAVIX Highway 99 Edmonds — Edmonds, WA Page 37 STORM WATER SITE PLAN • Where necessary to comply with the bullet above, construct stormwater retention or detention facilities as one of the first steps in grading. Assure that detention facilities function properly before constructing site improvements (e.g. impervious surfaces). • If permanent infiltration ponds are used for flow control during construction, protect these facilities from siltation during the construction phase. • Conduct downstream analysis if changes in off -site flows could impair or alter conveyance systems, streambanks, bed sediment, or aquatic habitat. • Even gently sloped areas need flow controls such as straw wattles or other energy dissipation / filtration structures. Place dissipation facilities closer together on steeper slopes. These methods prevent water from building higher velocities as it flows downstream within the construction site. • Outlet structures designed for permanent detention ponds are not appropriate for use during construction without modification. If used during construction, install an outlet structure that will allow for long-term storage of runoff and enable sediment to settle. Verify that the pond is sized appropriately for this purpose. Restore ponds to their original design dimensions, remove sediment, and install a final outlet structure at completion of the project. • Erosion has the potential to occur because of increases in the volume, velocity, and peak flow rate of stormwater runoff from the project site. The local permitting agency may require pond designs that provide additional or different stormwater flow control. These requirements may be necessary to address local conditions or to protect properties and waterways downstream. • Sites that must implement flow control for the developed site condition must also control stormwater release rates during construction. Construction site stormwater discharges shall not exceed the discharge durations of the pre -developed condition for the range of pre - developed discharge rates from Y2of the 2-year flow through the 10-year flow as predicted by an approved continuous runoff model. The pre -developed condition to be matched shall be the land cover condition immediately prior to the development project. This restriction on release rates can affect the size of the storage pond and treatment cells Element 4: Install Sediment Controls The Permittee must design, install and maintain effective erosion controls and sediment controls to minimize the discharge of pollutants. At a minimum, the Permittee must design, install and maintain such controls to: o Construct sediment control BMPs (sediment ponds, traps, filters, etc,) as one of the first steps in grading. These BIVIPs shall be functional before other land disturbing activities take place. • Minimize sediment discharges from the site. The design, installation and maintenance of erosion and sediment controls must address factors such as the amount, frequency, intensity and duration of precipitation, the nature of resulting stormwater runoff, and soil characteristics, including the range of soil particle sizes expected to be present on the site. • Direct stormwater runoff from disturbed areas through a sediment pond or other appropriate sediment removal BMP before the runoff leaves a construction site or NAVIX Highway 99 Edmonds — Edmonds, WA Page 38 STORMWATER SITE PLAN before discharge to an infiltration facility. Runoff from fully stabilized areas may be discharged without a sediment removal BMP but must meet the flow control performance standard in Element #3, bullet #1. • Locate BMPs intended to trap sediment on site in a manner to avoid interference with the movement of juvenile salmonids attempting to enter off -channel areas or drainages. • Provide and maintain natural buffers around surface waters, direct stormwater to vegetated areas to increase sediment removal, and maximize stormwater infiltration, unless infeasible. o Where feasible, design outlet structures that withdraw impounded stormwater from the surface to avoid discharging sediment that is still suspended lower in the water column. • Outlet structures that withdraw impounded stormwater from the surface to avoid discharging sediment that is still suspended lower in the water column are for the construction period only. If the pond using the construction outlet control is used for permanent stormwater controls, the appropriate outlet structure must be installed after the soil disturbance has ended. • Seed and mulch earthen structures such as dams, dikes, and diversions according to the timing indicated in Element #5. • Full stabilization includes concrete or asphalt paving; quarry spalls used as ditch lining; or the use of rolled erosion products, a bonded fiber matrix product, or vegetative cover in a manner that will fully prevent soil erosion. • The Local Permitting Authority may inspect and approve areas fully stabilized by means other than pavement or quarry spalls. • If installing a floating pump structure, include a stopper to prevent the pump basket from hitting the bottom of the pond. Element 5: Stabilize Soils • Stabilize exposed and unworked soils by application of effective BMPs that prevent erosion. Applicable BMPs include but are not limited to: temporary and permanent seeding, sodding, mulching, plastic covering, erosion control fabrics and matting, soil application of polyacrylamide (PAM), the early application of gravel base early on areas to be paved, and dust control. Control stormwater volume and velocity within the site to minimize soil erosion. • Control stormwater discharges, including both peak flow rates and total stormwater volume, to minimize erosion at outlets and to minimize downstream channel and stream bank erosion. • Soils must not remain exposed and unworked for more than the time periods set forth below to prevent erosion. • During the dry season (May 1 - Sept. 30): 7 days. • During the wet season (October 1 - April 30): 2 days. Stabilize soils at the end of the shift before a holiday or weekend if needed based on the weather forecast. NAVIX Highway 99 Edmonds — Edmonds, WA Page 39 STORMWATER SITE PLAN • Stabilize soil stockpiles from erosion, protect with sediment trapping measures, and where possible, be located away from storm drain inlets, waterways, and drainage channels. • Minimize the amount of soil exposed during construction activity. • Minimize the disturbance of steep slopes. • Minimize soil compaction and, unless infeasible, preserve topsoil. • Soils must not remain exposed and unworked for more than the time periods set forth above to prevent erosion for linear projects. • Soil stabilization measures should be appropriate for the time of year, site conditions, estimated duration of use, and potential water quality impacts that stabilization agents may have on downstream waters or ground water. Ensure that gravel base used for stabilization is clean and does not contain fines or sediment. Element 6: Protect Slopes • Design and construct cut -and -fill slopes in a manner to minimize erosion. Applicable practices include, but are not limited to, reducing continuous length of slope with terracing and diversions, reducing slope steepness, and roughening slope surfaces (for example, track walking). • Divert off -site stormwater (run-on) or ground water away from slopes and disturbed areas with interceptor dikes, pipes, and/or swales. Off -site stormwater should be managed separately from stormwater generated on the site. • At the top of slopes, collect drainage in pipe slope drains or protected channels to prevent erosion. o Temporary pipe slope drains must handle the peak volumetric flow rate calculated using a 10-minute time step from a Type 1A, 10-year, 24-hour frequency storm for the developed condition. Alternatively, the 10-year, 1-hour flow rate predicted by an approved continuous runoff model, increased by a factor of 1.6, may be used. The hydrologic analysis must use the existing land cover condition for predicting flow rates from tributary areas outside the project limits. For tributary areas on the project site, the analysis must use the temporary or permanent project land cover condition, whichever will produce the highest flow rates. If using the Western Washington Hydrology Model (WWHM) to predict flows, bare soil areas should be modeled as "landscaped" area. • Place excavated material on the uphill side of trenches, consistent with safety and space considerations. • Place check dams at regular intervals within constructed channels that are cut down a slope. • Where 15-minute time steps are available in an approved continuous runoff model, they may be used directly without a correction factor. • Consider soil type and its potential for erosion. • Stabilize soils on slopes, as specified in Element #5. • BMP combinations are the most effective method of protecting slopes with disturbed soils. For example, use both mulching and straw erosion control blankets in combination. NAVIX Highway 99 Edmonds — Edmonds, WA Page 40 STORMWATER SITE PLAN Element 7: Protect Permanent Drain Inlets • Protect all storm drain inlets made operable during construction so that stormwater runoff does not enter the conveyance system without first being filtered or treated to remove sediment. • Clean or remove and replace inlet protection devices when sediment has filled one-third of the available storage (unless a different standard is specified by the product manufacturer). • Where possible, protect all existing storm drain inlets so that stormwater runoff does not enter the conveyance system without first being filtered or treated to remove sediment. • Keep all approach roads clean. Do not allow sediment and street wash water to enter storm drains without prior and adequate treatment unless treatment is provided before the storm drain discharges to waters of the State. • Inlets should be inspected weekly at a minimum and daily during storm events. Element 8: Stabilize Channels and Outlets • Design, construct, and stabilize all on -site conveyance channels to prevent erosion from the following expected peak flows: o Channels must handle the peak volumetric flow rate calculated using a 10- minute time step from a Type 1A, 10-year, 24-hour frequency storm for the developed condition. Alternatively, the 10-year, 1-hour flow rate indicated by an approved continuous runoff model, increased by a factor of 1.6, may be used. The hydrologic analysis must use the existing land cover condition for predicting flow rates from tributary areas outside the project limits. For tributary areas on the project site, the analysis must use the temporary or permanent project land cover condition, whichever will produce the highest flow rates. If using the Western Washington Hydrology Model (WWHM) to predict flows, bare soil areas should be modeled as "landscaped area." • Provide stabilization, including armoring material, adequate to prevent erosion of outlets, adjacent streambanks, slopes, and downstream reaches at the outlets of all conveyance systems. • The best method for stabilizing channels is to completely line the channel with a blanket product first, then add check dams as necessaryto function as an anchorand to slow the flow of water. Element 9: Control Pollutants • Design, install, implement and maintain effective pollution prevention measures to minimize the discharge of pollutants. • Handle and dispose of all pollutants, including waste materials and demolition debris that occur on -site in a manner that does not cause contamination of stormwater. • Provide cover, containment, and protection from vandalism for all chemicals, liquid products, petroleum products, and other materials that have the potential to pose a threat to human health or the environment. On -site fueling tanks must include secondary containment. Secondary containment means placing tanks or containers within an NAVIX Highway 99 Edmonds — Edmonds, WA Page 41 STORM WATER SITE PLAN impervious structure capable of containing 110% of the volume contained in the largest tank within the containment structure. Double -walled tanks do not require additional secondary containment. • Conduct maintenance, fueling, and repair of heavy equipment and vehicles using spill prevention and control measures. Clean contaminated surfaces immediately following any spill incident. • Discharge wheel wash or tire bath wastewater to a separate on -site treatment system that prevents discharge to surface water, such as closed -loop recirculation or upland land application, or to the sanitary sewer, with local sewer district approval. • Apply fertilizers and pesticides in a manner and at application rates that will not result in loss of chemical to stormwater runoff. Follow manufacturers' label requirements for application rates and procedures. • Use BIVIPs to prevent contamination of stormwater runoff by pH -modifying sources. The sources for this contamination include, but are not limited to: bulk cement, cement kiln dust, fly ash, new concrete washing and curing waters, waste streams generated from concrete grinding and sawing, exposed aggregate processes, dewatering concrete vaults, concrete pumping and mixer washout waters. • Adjust the pH of stormwater if necessary to prevent violations of the water quality standards. • Assure that washout of concrete trucks is performed off -site or in designated concrete washout areas only. Do not wash out concrete trucks onto the ground, or into storm drains, open ditches, streets, or streams. Do not dump excess concrete on site, except in designated concrete washout areas. Concrete spillage or concrete discharge to surface waters of the State is prohibited. Obtain written approval from Ecology before using chemical treatment other than CO2 or dry ice to adjust pH. Element 10: Control De -Watering • Discharge foundation, vault, and trench dewatering water, which have characteristics similar to stormwater runoff at the site, into a controlled conveyance system before discharge to a sediment trap or sediment pond. • Discharge clean, non -turbid cle-watering water, such as well -point ground water, to systems tributary to, or directly into surface waters of the State, as specified in Element #8, provided the de -watering flow does not cause erosion or flooding of receiving waters or interfere with the operation of the system. Do not route clean clewatering water through stormwater sediment ponds. Note that "surface waters of the State" may exist on a construction site as well as off site; for example, a creek running through a site. • Handle highly turbid or contaminated clewatering water separately from stormwater. Other treatment or disposal options may include: o Infiltration. o Transport off -site in a vehicle, such as a vacuum flush truck, for legal disposal in a manner that does not pollute state waters. o Ecology -approved on -site chemical treatment or other suitable treatment technologies. NAVIX Highway 99 Edmonds — Edmonds, WA Page 42 STORMWATER SITE PLAN • Sanitary or combined sewer discharge with local sewer district approval if there is no other option. • Use of a sedimentation bag with outfall to a ditch or swale for small volumes of localized clewatering. • Channels must be stabilized, as specified in Element #8. • Construction equipment operation, clarnshell digging, concrete tremie pour, or work inside a cofferdam can create highly turbid or contaminated clewatering water. • Discharging sediment -laden (muddy) water into waters of the State likely constitutes violation of water quality standards for turbidity. The easiest way to avoid discharging muddy water is through infiltration and preserving vegetation. Element 11: Maintain BMPs • Maintain and repair all temporary and permanent erosion and sediment control BMPs as needed to assure continued performance of their intended function in accordance with BMP specifications. • Remove all temporary erosion and sediment control BMPs within 30 days after achieving final site stabilization or after the temporary BMPs are no longer needed. • Note: Some temporary erosion and sediment control BMPs are bio-clegraclable and designed to remain in place following construction such as compost socks. • Provide protection to all BMPs installed for the permanent control of stormwater from sediment and compaction. All BMPs that are to remain in place following completion of construction shall be examined and placed in full operating conditions. If sediment enters the BMPs during construction, it shall be removed, and the facility shall be returned to the conditions specified in the construction documents. • Remove or stabilize trapped sediment on site. Permanently stabilize disturbed soil resulting from removal of BMPs or vegetation. Element 12: Manage the Project Phase development projects to the maximum degree practicable and consider seasonal work limits. • Inspection and monitoring — Inspect, maintain, and repair all BMPs as needed to assure continued performance of their intended function. Conduct site inspections and monitoring in accordance with the Construction Stormwater General Permit or local plan approval authority. • Maintaining an updated construction SWPPP — Maintain, update, and implement the SWPPP in accordance with the Construction Stormwater General Permit. • Projects that disturb one or more acres must have, site inspections conducted by a Certified Erosion and Sediment Control Lead (CESCL). Project sites less than one acre (not part of a larger common plan of development or sale) may have a person without CESCL certification conduct inspections. By the initiation of construction, the SWPPP must identify the CESCL or inspector, who shall be present on -site or on -call at all times. • The CESCL or inspector (project sites less than one acre) must have the skills to assess the: u Site conditions and construction activities that could impact the quality of stormwater. NAVIX Highway 99 Edmonds — Edmonds, WA Page 43 STORM WATER SITE PLAN o Effectiveness of erosion and sediment control measures used to control the quality of stormwater discharges. • The CESCL or inspector must examine stormwater visually for the presence of suspended sediment, turbidity, discoloration, and oil sheen. They must evaluate the effectiveness of BMPs and determine if it is necessary to install, maintain, or repair BMPs to improve the quality of stormwater discharges. Based on the results of the inspection, construction site operators must correct the problems identified by: • Reviewing the SWPPP for compliance with the 13 construction SWPPP elements and making appropriate revisions within 7 days of the inspection. • Immediately beginning the process of fully implementing and maintaining appropriate source control and/or treatment BMPs as soon as possible, addressing the problems no later than within 10 days of the inspection. If installation of necessary treatment BMPs is not feasible within 10 days, the construction site operator may request an extension within the initial 10-day response period. • Documenting BMP implementation and maintenance in the site log book (applies only to sites that have coverage under the Construction Stormwater General Permit). • The CESCL or inspector must inspect all areas disturbed by construction activities, all BMPs, and all stormwater discharge points at least once every calendar week and within 24 hours of any discharge from the site. (For purposes of this condition, individual discharge events that last more than one day do not require daily inspections. For example, if a stormwater pond discharges continuously over the course of a week, only one inspection is required that week.) The CESCL or inspector may reduce the inspection frequency for temporary stabilized, inactive sites to once every calendar month 0 Phasing of Construction. o Phase development projects where feasible in order to prevent soil erosion and, to the maximum extent practical, and prevent transporting sediment from the site during construction. Revegetate exposed areas and maintain that vegetation as an integral part of the clearing activities for any phase. o Clearing and grading activities for developments shall be permitted only if conducted using an approved site development plan (e.g., subdivision approval) that establishes permitted areas of clearing, grading, cutting, and filling. Minimize removing trees and disturbing or compacting native soils when establishing permitted clearing and grading areas. Show on the site plans and the development site permitted clearing and grading areas and any other areas required to preserve critical or sensitive areas, buffers, native growth protection easements, or tree retention areas as may be required by local jurisdictions. 0 Seasonal Work Limitations o From October 1 through April 30, clearing, grading, and other soil disturbing activities is permitted only if shown to the satisfaction of the local permitting authority that the site operator will prevent silt -laden runoff from leaving the site through a combination of the following: 2 Site conditions including existing vegetative coverage, slope, soil type, and proximity to receiving waters. Limit activities and the extent of disturbed areas. NAVIX Highway 99 Edmonds — Edmonds, WA Page 44 STORMWATER SITE PLAN 0 Proposed erosion and sediment control measures. Based on the information provided and/or local weather conditions, the local permitting authority may expand or restrict the seasonal limitation on site disturbance. The local permitting authority has the authority to take enforcement action —such as a notice of violation, administrative order, penalty, or stop -work order under the following circumstances: • If, during the course of any construction activity or soil disturbance during the seasonal limitation period, sediment leaves the construction site causing a violation of the surface water quality standard; or • If clearing and grading limits or erosion and sediment control measures shown in the approved plan are not maintained. • The following activities are exempt from the seasonal clearing and grading limitations: () Routine maintenance and necessary repair of erosion and sediment control BMPs; o Routine maintenance of public facilities or existing utility structures that do not expose the soil or result in the removal of the vegetative cover to soil. c, Activities where there is one hundred percent infiltration of surface water runoff within the site in approved and installed erosion and sediment control facilities. • Coordination with Utilities and Other Contractors c) The primary project proponent shall evaluate, with input from utilities and other contractors, the stormwater management requirements for the entire project, including the utilities, when preparing the Construction SWPPP. Inspection and Monitoring o All BMPs must be inspected, maintained, and repaired as needed to assure continued performance of their intended function. Site inspections must be conducted by a person knowledgeable in the principles and practices of erosion and sediment control. The person must have the skills to 1) assess the site conditions and construction activities that could impact the quality of stormwater ' and 2) assess the effectiveness of erosion and sediment control measures used to control the quality of stormwater discharges. o For construction sites one acre or larger that discharge stormwater to surface waters of the state, a CESCL must be identified in the construction SWPPP; this person must be on -site or on -call at all times. Certification must be obtained through an approved training program that meets the erosion and sediment control training standards established by Ecology. n Appropriate BMPs or design changes shall be implemented as soon as possible whenever inspection and/or monitoring reveals that the BMPs identified in the Construction SWPPP are inadequate, due to the actual discharge of /or potential to discharge a significant amount of any pollutant. Maintaining an Updated Construction SWPPP Retain the Construction SWPPP on -site or within reasonable access to the site. Modify the SWPPP whenever there is a change in the design, construction, operation, or maintenance at the construction site that has, or could have, a significant effect on the discharge of pollutants to waters of the state. NAVIX Highway 99 Edmonds — Edmonds, WA Page 45 STORM WATER SITE PLAN The SWPPP must be modified if, during inspections or investigations conducted by the owner/operator, or the applicable local or state regulatory authority, it is determined that the SWPPP is ineffective in eliminating or significantly minimizing pollutants in stormwater discharges from the site. Modify the SWPPP as necessary to include additional or modified BMPs designed to correct problems identified. Complete revisions to the SWPPP within seven (7) days following the inspection. Element 13: Protect Low Impact Development BIVIPs Protect all Bioretention and Rain Garden BMPs from sedimentation through installation and maintenance of erosion and sediment control BMPs on portions of the site that drain into the Bioretention and/or Rain Garden BMPs. Restore the BMPs to their fully functioning condition if they accumulate sediment during construction. Restoring the BMP must include removal of sediment and any sediment -laden Bioretention/rain garden soils, and replacing the removed soils with soils meeting the design specification. • Prevent compacting Bioretention and rain garden BMPs by excluding construction equipment and foot traffic. Protect completed lawn and landscaped areas from compaction due to construction equipment. • Control erosion and avoid introducing sediment from surrounding land uses onto permeable pavements. Do not allow muddy construction equipment on the base material or pavement. Do not allow sediment -laden runoff onto permeable pavements. • Pavements fouled with sediments or no longer passing an initial infiltration test must be cleaned using procedures from the local stormwater manual or the manufacturer's procedures. • Keep all heavy equipment off existing soils under LID facilities that have been excavated to final grade to retain the infiltration rate of the soils. • See Chapter 5: Precision Site Preparation, Construction & Inspection of LID Facilities in the LID Technical Guidance Manual for Puget Sound (2012) for more detail on protecting LID integrated management practices. • Note that the LID Technical Guidance Manual for Puget Sound (2012) is for additional informational purposes only. You must follow the guidance within this manual if there are any discrepancies between this manual and the LID Technical Guidance Manual for Puget Sound(2012). NAVIX Highway 99 Edmonds — Edmonds, WA Page 46 STORM WATER SITE PLAN SPECIAL REPORTS AND STUDIES Special reports and studies for this property include the following: 0 Geotechnical Engineering Report prepared by Zipper Geo Associates, LLC, dated November 20,2018 o Report provided in Appendix D. On -Site Investigation prepared by Navix Engineering, dated November 2, 2018 o Navix visited the site to investigate existing on -site storm drainage and sanitary sewer infrastructure and to determine the depth and locations of pipes entering the site on the west and north frontages. Utility interception points are shown per the field location of existing utilities. OTHER PERMITS Other permits required for this project include the following: 0 Building permit; City of Edmonds • Olympic View Water and Sewer District Developer's Extension Agreement • NPDES General Construction Stormwater Discharge Permit; Department of Ecology NAVIX Highway 99 Edmonds — Edmonds, WA Page 47 STORMWATER SITE PLAN APPENDIX A WWHM DATA AND OUTPUT NAVIX Highway 99 Edmonds — Edmonds, WA Page 48 WWHM2012 PROJECT REPORT General Model Information Project Name: Hwy 99—Vault Site Name.- Highway 99 Apartments Site Address: 234th St SW & Highway 99 City: Edmonds, WA Report Date: 7/25/2019 MGS Region: Puget East Data Start: 1901/10/1 Data End: 2058/09/30 Timestep: Hourly DOT Data Number03 Version Date: 2018/10/10 Version: 4.2.16 POC Thresholds Low Flow Threshold for POC1: 50 Percent of the 2 Year High Flow Threshold for POC1 -. 50 Year Hwy 99—Vault 7/25/2019 4:12:47 PM Page 2 Landuse Basin Data Predeveloped Land Use Basin 1 Bypass: No GroundWater-. No Pervious Land Use acre C, Forest, Mod 1.44 Pervious Total 1.44 Impervious Land Use acre Impervious Total 0 Basin Total 1.44 Element Flows To: Surface Interflow Groundwater Hwy 99_Vault 7/25/2019 4:12:47 PM Page 3 Mitigated Land Use Basin 1 Bypass: No GroundWater: No Pervious Land Use acre C, Lawn, Flat 0.19 Pervious Total 0.19 Impervious Land Use acre ROOF TOPS FLAT 1.11 DRIVEWAYS FLAT 0.14 Impervious Total 1.25 Basin Total 1.44 Element Flows To: Surface Vault 1 Interflow Vault 1 Groundwater Hwy 99—Vault 7/25/2019 4:12:47 PM Page 4 Routing Elements Predeveloped Routing Hwy 99_Vault 7/25/2019 4:12:47 PM Page 5 Mitigated Routing Vault 1 Width: Length: Depth: Discharge Structure Riser Height: Riser Diameter: Notch Type: Notch Width: Notch Height: Orifice 1 Diameter: Element Flows To: Outlet 1 39.25 ft. 150 ft. 5.75 ft. 5.25 ft. 18 in. Rectangular 0.010 ft. 1.750 ft. 0.5 in. Elevation:O ft. Outlet 2 Vault Hydraulic Table Stageffeet) 0.0000 0.0639 0.1278 0.1917 0.2556 0.3194 0.3833 0.4472 0.5111 0.5750 0.6389 0.7028 0.7667 0.8306 0.8944 0.9583 1.0222 1.0861 1.1500 1.2139 1.2778 1.3417 1.4056 1.4694 1.5333 1.5972 1.6611 1.7250 1.7889 1.8528 1.9167 1.9806 2.0444 2.1083 2,1722 2.2361 2.3000 Area(ac.) 0.135 0.135 0.135 0.135 0.135 0.135 0.135 0.135 0.135 0.135 0.135 0.135 0.135 0.135 0.135 0.135 0.135 0.135 0.135 0.135 0.135 0.135 0.135 0.135 0.135 0.135 0.135 0.135 0.135 0.135 0.135 0.135 0.135 0.135 0.135 0.135 0,135 Volume(ac-ft.) 0.000 0.008 0.017 0.025 0,034 0.043 0.051 0.060 0.069 0.077 0.086 0.095 0.103 0.112 0.120 0,129 0.138 0.146 0.155 0.164 0.172 0.181 0.190 0.198 0.207 0.215 0.224 0.233 0.241 0.250 0.259 0.267 0.276 0.285 0.293 0.302 0.310 Discharge(cfs) 0.000 0.001 0.002 0.003 0.003 0.003 0.004 0.004 0.004 0.005 0.005 0.005 0.005 0.006 0.006 0.006 0.006 0.007 0.007 0.007 0.007 0.007 0,008 0.008 0.008 0.008 0.008 0.008 0.009 0.009 0.009 0.009 0.009 0.009 0.010 0.010 0.010 Infilt(cfs) 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0,000 0.000 Hwy 99_Vault 7/25/2019 4:12:47 PM Page 6 2.3639 0.135 0.319 0.010 0.000 2.4278 0.135 0.328 0.010 0.000 2.4917 0.135 0.336 0.010 0.000 2.5556 0.135 0.345 0.010 0.000 2.6194 0.135 0.354 0.011 0.000 2.6833 0.135 0.362 0.011 0.000 2.7472 0.135 0.371 0.011 0.000 2.8111 0.135 0.379 0.011 0.000 2.8750 0.135 0.388 0.011 0.000 2.9389 0.135 0.397 0.011 0.000 3.0028 0.135 0.405 0.011 0.000 3.0667 0.135 0.414 0.011 0.000 3.1306 0.135 0.423 0.012 0.000 3.1944 0.135 0.431 0,012 0.000 3.2583 0.135 0.440 0.012 0.000 3.3222 0.135 0.449 0.012 0.000 3.3861 0.135 0.457 0.012 0.000 3.4500 0.135 0.466 0.012 0.000 3.5139 0.135 0.474 0.012 0.000 3.5778 0.135 0.483 0.013 0.000 3.6417 0.135 0.492 0.014 0.000 3.7056 0.135 0.500 0.016 0.000 3.7694 0.135 0.509 0.017 0.000 3.8333 0.135 0.518 0.019 0.000 3.8972 0.135 0.526 0.021 0.000 3.9611 0.135 0.535 0.023 0.000 4.0250 0.135 0.544 0.024 0.000 4.0889 0.135 0.552 0.027 0.000 4.1528 0.135 0.561 0.029 0.000 4.2167 0.135 0.569 0.031 0.000 4.2806 0.135 0.578 0.033 0.000 4.3444 0.135 0.587 0.035 0.000 4.4083 0.135 0.595 0.037 0.000 4.4722 0.135 0.604 0.040 0.000 4.5361 0.135 0.613 0.042 0.000 4.6000 0.135 0.621 0.045 0.000 4.6639 0.135 0.630 0.048 0.000 4.7278 0.135 0.639 0.051 0.000 4.7917 0.135 0.647 0.054 0.000 4.8556 0.135 0.656 0.057 0.000 4.9194 0.135 0.664 0.074 0.000 4.9833 0.135 0.673 0.078 0.000 5.0472 0.135 0.682 0.082 0.000 5.1111 0.135 0.690 0.087 0.000 5.1750 0.135 0.699 0.091 0.000 5.2389 0.135 0.708 0.096 0.000 5.3028 0.135 0.716 0.289 0.000 5.3667 0.135 0.725 0.729 0.000 5.4306 0.135 0.734 1.306 0.000 5.4944 0.135 0.742 1.974 0.000 5.5583 0.135 0.751 2.693 0.000 5.6222 0.135 0.759 3.421 0.000 5.6861 0.135 0.768 4.115 0.000 5.7500 0.135 0.777 4.736 0.000 5.8139 0.129 0.656 5.256 0.000 Hwy 99_Vault 7/25/2019 4:12:47 PM Page 7 Analysis Results POC I 0 Oz 0.05 0 J L 0.03 0.01 + Predeveloped Predeveloped Landuse Totals for POC #1 10 10 01 .1 0� 2 5 10 20 30 50 70 80 90 95 W 99 "5 x Mitigated Total Pervious Area: 1.44 Total Impervious Area: 0 Mitigated Landuse Totals for POC #1 Total Pervious Area: 0.19 Total Impervious Area: 1.25 Flow Frequency Method: Log Pearson Type III 17B Flow Frequency Return Periods for Predeveloped. POC #1 Return Period Flow(cfs) 2 year 0.024565 5 year 0.040787 10 year 0.049992 25 year 0.059592 50 year 0.065395 100 year 0.070218 Flow Frequency Return Periods for Mitigated. POC #1 Return Period Flow(cfs) 2 year 0.012329 5 year 0.019703 10 year 0.026505 25 year 0.037889 50 year 0.048849 100 year 0.062378 AnnualPeaks Annual Peaks for Predeveloped and Mitigated. POC #1 Year Predeveloped Mitigated 1902 0.034 0.011 1903 0.011 0.008 1904 0.030 0.010 1905 0.013 0.012 1906 0.005 0.008 1907 0.038 0.011 1908 0.024 0.009 1909 0.026 0.011 1910 0.045 0.011 1911 0.021 0.010 Hwy 99—Vault 7/25/2019 4:12:47 PM Page 8 1912 0.093 0.013 1913 0.036 0.017 1914 0.008 0.009 1915 0.012 0.013 1916 0.020 0.011 1917 0.009 0.010 1918 0.024 0.029 1919 0.017 0.010 1920 0.022 0.010 1921 0.022 0.012 1922 0.025 0.011 1923 0.022 0.012 1924 0.011 0.009 1925 0.011 0.009 1926 0.020 0.010 1927 0.027 0.010 1928 0.017 0.011 1929 0.043 0.013 1930 0.022 0.011 1931 0.022 0.012 1932 0.017 0.012 1933 0.019 0.012 1934 0.058 0.056 1935 0.019 0.017 1936 0.031 0.012 1937 0.029 0.010 1938 0.026 0.012 1939 0.001 0.009 1940 0.020 0.012 1941 0.021 0.010 1942 0.031 0.043 1943 0.010 0.011 1944 0.032 0.017 1945 0.022 0.013 1946 0.021 0.011 1947 0.015 0.009 1948 0.049 0.011 1949 0.042 0.022 1950 0.021 0.011 1951 0.026 0.012 1952 0.084 0.021 1911, 0.068 0.046 1954 0.019 0.011 1955 0.016 0.010 1956 0.010 0.009 1957 0.028 0.013 1958 0.068 0.064 1959 0.041 0.051 1960 0.014 0.010 1961 0.041 0.042 1962 0.021 0.012 1963 0.009 0.009 1964 0.019 0.009 1965 0.049 0.044 1966 0.009 0.010 1967 0.019 0.009 1968 0.025 0.012 1969 0.017 0.011 Hwy 99. Vault 7/25/2019 4:13:11 PM Page 9 1970 0.031 0.011 1971 0.052 0.031 1972 0.033 0.012 1973 0.039 0.021 1974 0.026 0.011 1975 0.061 0.052 1976 0.025 0.011 1977 0.014 0.010 1978 0.047 0.045 1979 0.012 0.010 1980 0.023 0.011 1981 0.023 0.011 1982 0.016 0.011 1983 0.039 0.012 1984 0.010 0.010 1985 0.023 0.010 1986 0.018 0.012 1987 0.040 0.029 1988 0.028 0.018 1989 0.023 0.010 1990 0.029 0.011 1991 0.022 0.012 1992 0.034 0.032 1993 0.028 0.012 1994 0.049 0.012 1995 0.012 0.010 1996 0.057 0.048 1997 0.025 0.012 1998 0.024 0.011 1999 0.000 0.007 2000 0.017 0.012 2001 0.012 0.009 2002 0.047 0.011 2003 0.026 0.012 2004 0.029 0.012 2005 0.042 0.012 2006 0.016 0.011 2007 0.018 0.011 2008 0.024 0.011 2009 0.015 0.010 2010 0.012 0.013 2011 0.015 0.011 2012 0.021 0.010 2013 0.018 0.010 2014 0.012 0.009 2015 0,054 0.010 2016 0.007 0.010 2017 0.043 0.020 2018 0.077 0.064 2019 0.082 0.051 2020 0.028 0.010 2021 0.032 0.026 2022 0.011 0.010 2023 0.026 0.012 2024 0.104 0.011 2025 0.021 0.011 2026 0.037 0.014 2027 0.016 0.010 Hwy 99-Vault 7/25/2019 4:13:11 PM Page 10 2028 0.008 0.008 2029 0.026 0.020 2030 0.056 0.014 2031 0.014 0.009 2032 0.011 0.008 2033 0.012 0.009 2034 0.014 0.009 2035 0.059 0.054 2036 0.032 0.012 2037 0.005 0.009 2038 0.036 0.014 2039 0.002 0.007 2040 0.011 0.010 2041 0.016 0.009 2042 0.064 0.040 2043 0.027 0.019 2044 0.037 0.018 2045 0.023 0.013 2046 0.027 0.042 2047 0.017 0.013 2048 0.023 0.011 20AQ 0.023 0.011 2050 0.014 0.011 2051 0.024 0.011 2052 0.014 0.012 2053 0.024 0.043 2054 0.046 0.016 2055 0.009 0.009 2056 0.009 0.009 2057 0.015 0.012 2058 0.019 0.015 Ranked Annual Peaks Ranked Annual Peaks for Precleveloped and Mitigated. POC #1 Rank Predeveloped Mitigated 1 0.1036 0.0644 2 0.0925 0.0638 3 0.0844 0.0555 4 0.0821 0.0540 5 0.0770 0.0523 6 0.0682 0.0511 7 0.0678 0.0506 8 0.0639 0.0485 9 0.0613 0.0464 10 0.0591 0.0449 11 0.0582 0.0441 12 0.0573 0.0431 13 0.0557 0.0426 14 0.0540 0.0424 15 0.0516 0.0418 16 0.0495 0.0396 17 0.0491 0.0324 18 0.0489 0.0315 19 0.0468 0.0294 20 0.0467 0.0290 21 0.0456 0.0260 22 0.0448 0.0216 23 0.0429 0.0213 Hwy 99_ Vault 7/25/2019 4:13:11 PM Page 11 24 0.0425 0.0207 25 0.0424 0.0205 26 0.0416 0.0199 27 0.0406 0.0194 28 0.0405 0.0184 29 0.0397 0.0178 30 0.0391 0.0173 31 0.0388 0.0171 32 0.0383 0.0170 33 0.0375 0.0160 34 0.0371 0.0145 35 0.0361 0.0144 36 0.0358 0.0141 37 0.0338 0.0141 38 0,0336 0.0133 39 0.0335 0.0127 40 0.0323 0.0127 41 0.0323 0.0126 42 0.0318 0.0126 43 0.0314 0.0126 44 0.0314 0.0125 45 0.0310 0.0125 46 0,0297 0.0124 47 0,0294 0.0123 48 0,0290 0.0123 49 0,0288 0.0123 50 0,0285 0.0122 51 0,0281 0.0122 52 0,0279 0.0122 53 0.0277 0.0122 54 0.0269 0.0121 55 0.0269 0.0121 56 0.0266 0.0121 57 0.0264 0.0120 58 0.0262 0.0120 59 0.0261 0.0119 60 0.0259 0.0119 61 0.0258 0.0118 62 0.0257 0.0118 63 0.0256 0.0118 64 0.0254 0.0118 65 0.0252 0.0117 66 0.0249 0.0116 67 0.0246 0.0116 68 0.0244 0.0116 69 0.0240 0.0116 70 0.0238 0.0115 71 0.0237 0.0115 72 0.0236 0.0115 73 0.0235 0.0115 74 0.0234 0.0115 75 0.0233 0.0115 76 0.0232 0.0114 77 0.0228 0.0114 78 0.0227 0.0114 79 0.0226 0.0112 80 0.0226 0.0112 81 0.0225 0.0112 Hwy 99_Vault 7/25/2019 4:13:11 PM Page 12 82 0.0224 0.0111 83 0.0223 0.0111 84 0.0223 0.0111 85 0.0223 0.0110 86 0.0221 0.0110 87 0.0219 0.0109 88 0.0215 0.0109 89 0.0214 0.0109 90 0.0214 0.0109 91 0.0212 0.0109 92 0.0210 0.0109 93 0.0208 0.0108 94 0.0205 0.0108 95 0.0202 0.0108 96 0.0202 0,0108 97 0.0196 0.0107 98 0.0192 0.0107 99 0.0192 0.0107 100 0.0190 0.0107 101 0.0189 0.0107 102 0.0187 0.0106 103 0.0186 0.0106 104 0.0184 0.0106 105 0.0182 0.0105 106 0.0182 0.0105 107 0.0175 0.0104 108 0.0174 0.0104 109 0.0172 0.0104 110 0.0171 0.0104 ill 0.0168 0.0103 112 0.0167 0.0103 113 0.0164 0.0103 114 0.0163 0.0103 115 0.0159 0.0100 116 0.0158 0.0100 117 0.0157 0.0100 118 0.0153 0.0099 119 0.0151 0.0099 120 0.0150 0.0098 121 0.0147 0.0098 122 0.0144 0.0098 123 0.0143 0.0098 124 0.0142 0.0098 125 0.0141 0.0098 126 0.0139 0.0097 127 0.0139 0.0097 128 0.0130 0.0096 129 0.0124 0.0096 130 0.0123 0.0096 131 0.0122 0.0095 132 0.0119 0.0095 133 0.0118 0.0095 134 0.0117 0.0095 135 0.0116 0.0094 136 0.0115 0.0094 137 0.0111 0.0094 138 0.0109 0.0094 139 0.0109 0.0093 Hwy 99-Vault 7/25/2019 4:13:11 PM Page 13 140 0.0107 0.0092 141 0.0107 0.0091 142 0.0104 0.0091 143 0.0100 0.0090 144 0.0099 0.0090 145 0.0094 0.0089 146 0.0093 0.0088 147 0.0092 0.0087 148 0.0091 0.0087 149 0.0086 0.0086 150 0.0083 0.0086 151 0.0077 0.0085 152 0.0066 0.0083 153 0.0050 0.0083 154 0.0050 0.0082 155 0.0020 0.0078 156 0.0012 0.0072 157 0.0003 0.0071 Hwy 99-Vault 7/25/2019 4:13:11 PM Page 14 Duration Flows The Facility PASSED Flow(cfs) Predev mit Percentage Pass/Fail 0.0123 12746 12630 99 Pass 0.0128 11591 7302 62 Pass 0.0134 10532 6351 60 Pass 0.0139 9598 5760 60 Pass 0.0144 8792 5299 60 Pass 0.0150 8070 4921 60 Pass 0.0155 7430 4550 61 Pass 0.0160 6852 4228 61 Pass 0.0166 6298 3946 62 Pass 0.0171 5809 3666 63 Pass 0.0176 5332 3417 64 Pass 0.0182 4901 3187 65 Pass 0.0187 4509 2966 65 Pass 0.0193 4171 2787 66 Pass 0.0198 3845 2608 67 Pass 0.0203 3548 2451 69 Pass 0.0209 3274 2298 70 Pass 0.0214 3026 2172 71 Pass 0.0219 2809 2071 73 Pass 0.0225 2615 1956 74 Pass 0.0230 2443 1859 76 Pass 0.0235 2290 1773 77 Pass 0.0241 2118 1691 79 Pass 0.0246 1985 1612 81 Pass 0.0252 1869 1541 82 Pass 0.0257 1762 1464 83 Pass 0.0262 1652 1389 84 Pass 0.0268 1562 1321 84 Pass 0.0273 1478 1245 84 Pass 0.0278 1393 1180 84 Pass 0.0284 1324 1126 85 Pass 0.0289 1243 1069 86 Pass 0.0295 1172 1002 85 Pass 0.0300 1120 962 85 Pass 0.0305 1053 919 87 Pass 0.0311 1000 877 87 Pass 0.0316 953 842 88 Pass 0.0321 901 806 89 Pass 0.0327 868 770 88 Pass 0.0332 833 738 88 Pass 0.0337 799 701 87 Pass 0.0343 774 662 85 Pass 0.0348 740 629 85 Pass 0.0354 717 597 83 Pass 0.0359 688 567 82 Pass 0.0364 658 542 82 Pass 0.0370 630 509 80 Pass 0.0375 598 481 80 Pass 0.0380 564 446 79 Pass 0.0386 538 416 77 Pass 0.0391 511 384 75 Pass 0.0396 487 353 72 Pass 0.0402 465 328 70 Pass Hwy 99-Vault 7/25/2019 4:13:11 PM Page 15 0.0407 447 299 66 Pass 0.0413 434 274 63 Pass 0.0418 412 249 60 Pass 0.0423 399 227 56 Pass 0.0429 375 210 56 Pass 0.0434 360 191 53 Pass 0.0439 343 175 51 Pass 0.0445 326 158 48 Pass 0.0450 309 144 46 Pass 0.0455 292 134 45 Pass 0.0461 279 126 45 Pass 0.0466 264 117 44 Pass 0.0472 254 105 41 Pass 0.0477 237 95 40 Pass 0.0482 225 86 38 Pass 0.0488 214 70 32 Pass 0.0493 203 67 33 Pass 0.0498 185 61 32 Pass 0.0504 176 52 29 Pass 0,0509 166 45 27 Pass 0.0514 156 41 26 Pass 0.0520 139 35 25 Pass 0.0525 128 33 25 Pass 0.0531 120 29 24 Pass 0.0536 112 27 24 Pass 0.0541 99 24 24 Pass 0.0547 95 21 22 Pass 0.0552 84 19 22 Pass 0.0557 79 16 20 Pass 0.0563 78 14 17 Pass 0.0568 73 12 16 Pass 0.0573 66 12 18 Pass 0.0579 61 10 16 Pass 0.0584 53 10 18 Pass 0.0590 47 10 21 Pass 0.0595 43 8 18 Pass 0.0600 39 6 15 Pass 0.0606 36 6 16 Pass 0.0611 34 6 17 Pass 0.0616 31 5 16 Pass 0.0622 29 5 17 Pass 0.0627 27 4 14 Pass 0.0632 27 4 14 Pass 0.0638 25 2 8 Pass 0.0643 21 1 4 Pass 0.0649 21 0 0 Pass 0.0654 19 0 0 Pass Hwy 99-Vault 7/25/2019 4:13:11 PM Page 16 Water Quality Water Quality BMP Flow and Volume for POC #1 On-line facility volume: 0 acre-feet On-line facility target flow: 0 cfs. Adjusted for 15 min: 0 cfs. Off-line facility target flow: 0 cfs. Adjusted for 15 min: 0 cfs. Hwy 99—Vault 7/25/2019 4:13:11 PM Page 17 LID Report LID Technique Used for Total Volume Volume Infiltration Cumulative Percent Water Quality Percent Comment Treatment ? Needs Through Volume Volume Volume Water Quality Treatment Facility (ac-ft) Infiltration Infiltrated Treated (ac-ft) (a c-ft) Credit Vault 1 POC 13 458.88 Q 0.00 Total Volume Infiltrated 458.881 0.00 0.00 0.001 0-00 0% No, Treat Credit Compliance with LID Duration Standard 8% of 2-yr to 50% of Analysis 2-yr Result Failed Hwy 99—Vault 7/25/2019 4:13:11 PM Page 18 Model Default Modifications Total of 0 changes have been made. PERLND Changes No PERLND changes have been made. IMPLND Changes No IMPLND changes have been made. Hwy 99—Vault 7/25/2019 4:13:27 PM Page 19 Appendix Predeveloped Schematic Basin 1.44ac Hwy 99—Vault 7/25/2019 4:13:27 PM Page 20 Mitigated Schematic Basin 1.44ac Sl ault 1 Hwy 99_Vault 7/25/2019 4:13:30 PM Page 21 JPJ redeveloped UCI File RUN GLOBAL WWHM4 model simulation START 1901 10 01 END RUN INTERP OUTPUT LEVEL 3 0 RESUME 0 RUN 1 END GLOBAL FILES <File> <Un#> < ----------- File Nam <-ID-> WDM 26 Hwy 99 Vault.wdm MESSU 25 PreHwy 99-Vault.MES 27 PreHwy 99-Vault.L61 28 PreHwy 99-Vault.L62 30 POCHwy 99-Vaultl.dat END FILES 2058 09 30 OPN SEQUENCE UNIT SYSTEM 1 e------------------------------ INGRP INDELT 00:60 PERLND 11 COPY 501 DISPLY 1 END INGRP END OPN SEQUENCE DISPLY DISPLY-INFO1 # - #< ---------- Title ----------- >***TRAN PIVL DIG1 FIL1 1 Basin 1 MAX END DISPLY-INFOl END DISPLY COPY TIMESERIES # - # NPT NMN 1 1 1 501 1 1 END TIMESERIES END COPY GENER OPCODE # # OPCD END OPCODE PARM # # K END PARM END GENER PERLND GEN-INFO <PLS >< ------- Name ------- >NBLKS Unit -systems Printer # - # User t-series Engl Metr in out 11 C, Forest, Mod 1 1 1 1 27 0 END GEN-INFO *** Section PWATER*** PYR DIG2 FIL2 YRND 1 2 30 9 ACTIVITY <PLS > Active Sections # - # ATMP SNOW PWAT SED PST PWG PQAL MSTL PEST NITR PHOS TRAC 11 0 0 1 0 0 0 0 0 0 0 0 0 END ACTIVITY PRINT -INFO <PLS > Print -flags PIVL PYR # - # ATMP SNOW PWAT SED PST PWG PQAL MSTL PEST NITR PHOS TRAC ********* 11 0 0 4 0 0 0 0 0 0 0 0 0 1 9 END PRINT -INFO Hwy 99-Vault 7/25/2019 4:13:33 PM Page 22 PWAT-PARM1 <PLS > PWATER variable monthly parameter value flags # - # CSNO RTOP UZFG VCS VUZ VNN VIFW VIRC VLE INFC HWT 11 0 0 0 0 0 0 0 0 0 0 0 END PWAT-PARMI PWAT-PARM2 <PLS > PWATER input info: Part 2 # - # ***FOREST LZSN INFILT LSUR SLSUR KVARY AGWRC 11 0 4.5 0.08 400 0.1 0.5 0,996 END PWAT-PARM2 PWAT-PARM3 <PLS > PWATER input info: Part 3 # - # ***PETMAX PETMIN INFEXP INFILD DEEPFR BASETP AGWETP 11 0 0 2 2 0 0 0 END PWAT-PARM3 PWAT-PARM4 <PLS > PWATER input info: Part 4 # - # CEPSC UZSN NSUR INTFW IRC LZETP 11 0.2 0.5 0.35 6 0.5 0.7 END PWAT-PARM4 PWAT-STATE1 <PLS > Initial conditions at start of simulation ran from 1990 to end of 1992 (pat 1-11-95) RUN 21 # - # CEPS SURS UzS IFWS LZS AGWS GWVS 11 0 0 0 0 2.5 1 0 END PWAT-STATE1 END PERLND IMPLND GEN-INFO <PLS >< ------- Name ------- > Unit -systems Printer # - # User t-series Engl Metr in out END GEN-INFO Section IWATER*** ACTIVITY <PLS > Active Sections # - # ATMP SNOW IWAT SLD IWG IQAL END ACTIVITY PRINT -INFO <ILS > ******** Print -flags ******** PIVL PYR # - # ATMP SNOW IWAT SLD IWG IQAL END PRINT -INFO IWAT-PARM1 <PLS > IWATER variable monthly parameter value flags # - # CSNO RTOP VRS VNN RTLI END IWAT-PARM1 IWAT-PARM2 <PLS > IWATER input info: Part 2 # - # *** LSUR SLSUR NSUR RETSC END IWAT-PARM2 IWAT-PARM3 <PLS > IWATER input info: Part 3 # - # ***PETMAX PETMIN END IWAT-PARM3 IWAT-STATE1 <PLS > Initial conditions at start of simulation # - # RETS SURS END IWAT-STATEl Hwy 99—Vault 7/25/2019 4:13:33 PM Page 23 � 4 END IMPLND SCHEMATIC <-Source-> <Name> # Basin 1*** PERLND 11 PERLND 11 ******Routing****** END SCHEMATIC <--Area--> <-Target-> MBLK <-factor-> <Name> # Tbl# 1.44 COPY Sol 12 1.44 COPY 501 13 NETWORK <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Target vols> <-Grp> <-Member-> <Name> # <Name> # #<-factor->strg <Name> # # <Name> # # COPY 501 OUTPUT MEAN 1 1 12.1 DISPLY 1 INPUT TIMSER 1 <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Target vols> <-Grp> <-Member-> <Name> # <Name> # #<-factor->strg <Name> # # <Name> # # END NETWORK RCHRES GEN-INFO RCHRES Name Nexits Unit Systems Printer # - #< ------------------ ><--- > User T-series Engl Metr LKFG in out END GEN-INFO *** Section RCHRES*** ACTIVITY <PLS > Active Sections # - # HYFG ADFG CNFG HTFG SDFG GQFG OXFG NUFG PKFG PHFG END ACTIVITY PRINT -INFO <PLS > Print -flags PIVL PYR # - # HYDR ADCA CONS HEAT SED GQL OXRX NUTR PLNK PHCB PIVL PYR END PRINT -INFO HYDR-PARM1 RCHRES Flags for each HYDR Section VC Al A2 A3 ODFVFG for each ODGTFG for each FUNCT for each FG FG FG FG possible exit possible exit possible exit END HYDR-PARM1 HYDR-PARM2 # - # FTABNO LEN DELTH STCOR KS DB50 < ------ >< -------- >< >< >< >< >< > END HYDR-PARM2 HYDR-INIT RCHRES Initial conditions for each HYDR section # VOL Initial value of COLIND Initial value of OUTDGT *** ac-ft for each possible exit for each possible exit < >< -------- > < >< >< >< >< > < >< >< >< >< > END HYDR-INIT END RCHRES SPEC -ACTIONS END SPEC -ACTIONS FTABLES END FTABLES EXT SOURCES <-Volume-> <Member> SsysSgap<--Mult-->Tran <-Target vols> <-Grp> <-Member-> <Name> 4 <Name> # tem strg<-factor->strg <Name> # # <Name> # # WDM 2 PREC ENGL 1 PERLND 1 999 EXTNL PREC WDM 2 PREC ENGL 1 IMPLND 1 999 EXTNL PREC Hwy 99_Vault 7/25/2019 4:13:33 PM Page 24 WDM 1 EVAP ENGL 0.76 PERLND 1 999 EXTNL PETINP WDM 1 EVAP ENGL 0.76 IMPLND 1 999 EXTNL PETINP END EXT SOURCES EXT TARGETS <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Volume-> <Member> Tsys Tgap Amd <Name> # <Name> # #<-factor->strg <Name> # <Name> tem strg strg*** COPY 501 OUTPUT MEAN 1 1 12.1 WDM 501 FLOW ENGL REPL END EXT TARGETS MASS -LINK <Volume> <-Grp> <-Member-><--Mult--> <Target> <-Grp> <-Member->*** <Name> <Name> # #<-factor-> <Name> <Name> # #*** MASS -LINK 12 PERLND PWATER SURO 0.083333 COPY INPUT MEAN END MASS -LINK 12 MASS -LINK 13 PERLND PWATER TFWO 0.083333 COPY INPUT MEAN END MASS -LINK 13 END MASS -LINK END RUN Hwy 99—Vault —4 7/25/2019 4:13:33 PM Page 25 Mitigated UCI File RUN GLOBAL WWHM4 model simulation START 1901 10 01 END RUN INTERP OUTPUT LEVEL 3 0 RESUME 0 RUN 1 END GLOBAL FILES <File> <Un#> < ----------- File Nam <-ID-> WDM 26 Hwy 99 - Vault.wdm MESSU 2S MitHwy 99-Vault.MES 27 MitHwy 99-Vault.L61 28 MitHwy 99-Vault.L62 30 POCHwy 99-Vaultl.dat END FILES 2058 09 30 OPN SEQUENCE UNIT SYSTEM 1 e------------------------------ PRINT-INFO <PLS > Print -flags PIVL PYR Hwy 99-Vault 7/25/2019 4:13:33 PM Page 26 INGRP INDELT 00:60 PERLND 16 IMPLND 4 IMPLND 5 RCHRES 1 COPY 1 COPY Sol DISPLY 1 END INGRP END OPN SEQUENCE DISPLY DISPLY-INFOl # - #< ---------- Title ----------- >***TRAN PIVL DIG1 FILl 1 Vault 1 MAX END DISPLY-INFOl END DISPLY COPY TIMESERIES # - # NPT NMN 1 1 1 501 1 1 END TIMESERIES END COPY GENER OPCODE # # OPCD END OPCODE PARM # # K END PARM END GENER PERLND GEN-INFO <PLS >< ------- Name ------- >NBLKS Unit -systems Printer # - # User t-series Engl Metr in out 16 C, Lawn, Flat 1 1 1 1 27 0 END GEN-INFO *** Section PWATER*** PYR DIG2 FIL2 YRND 1 2 30 9 ACTIVITY <PLS > Active Sections # - # ATMP SNOW PWAT SED PST PWG PQAL MSTL PEST NITR PHOS TRAC 16 0 0 1 0 0 0 0 0 0 0 0 0 END ACTIVITY ATMP SNOW PWAT SED PST PWG PQAL MSTL PEST NITR PHOS TRAC 16 0 0 4 0 0 0 0 0 0 0 0 0 1 9 END PRINT -INFO PWAT-PARM1 <PLS > PWATER variable monthly parameter value flags # - # CSNO RTOP UZFG VCS VUZ VNN VIFW VIRC VLE INFC HWT 16 0 0 0 0 0 0 0 0 0 0 0 END PWAT-PARM1 PWAT-PARM2 <PLS > PWATER input info: Part 2 # - # ***FOREST LZSN INFILT LSUR SLSUR KVARY AGWRC 16 0 4.5 0.03 400 0.05 0.5 0.996 END PWAT-PARM2 PWAT-PARM3 <PLS > PWATER input info: Part 3 # - # ***PETMAX PETMIN INFEXP INFILD DEEPFR BASETP AGWETP 16 0 0 2 2 0 0 0 END PWAT-PARM3 PWAT-PARM4 <PLS > PWATER input info: Part 4 # - # CEPSC UZSN NSUR INTFW IRC LZETP 16 0.1 0.25 0.25 6 0.5 0.25 END PWAT-PARM4 PWAT-STATE1 <PLS > Initial conditions at start of simulation ran from 1990 to end of 1992 (pat 1-11-95) RUN 21 # - # CEPS SURS UzS IFWS LZS AGWS GWVS 16 0 0 0 0 2.S 1 0 END PWAT-STATE1 END PERLND IMPLND GEN-INFO <PLS >< ------- Name ------- > Unit -systems Printer # - # User t-series Engl Metr in out 4 ROOF TOPS/FLAT 1 1 1 27 0 5 DRIVEWAYS/FLAT 1 1 1 27 0 END GEN-INFO Section IWATER*** ACTIVITY <PLS > Active Sections # - # ATMP SNOW IWAT SLD IWG IQAL 4 0 0 1 0 0 0 5 0 0 1 0 0 0 END ACTIVITY PRINT -INFO <ILS > ******** Print -flags ******** PIVL PYR # ATMP SNOW IWAT SLD IWG IQAL 4 0 0 4 0 0 0 1 9 5 0 0 4 0 0 0 1 9 END PRINT -INFO IWAT-PARM1 <PLS > IWATER variable monthly parameter value flags # - # CSNO RTOP VRS VNN RTLI 4 0 0 0 0 0 5 0 0 0 0 0 END IWAT-PARM1 IWAT-PARM2 <PLS > IWATER input info: Part 2 # - # *** LSUR SLSUR NSUR RETSC Hwy 99-Vault 7/25/2019 4:13:33 PM Page 27 4 400 0.01 0.1 0.1 s 400 0.01 0.1 0.1 END IWAT-PARM2 IWAT-PARM3 <PLS > IWATER input info: Part 3 # - # ***PETMAX PETMIN 4 0 0 s 0 0 END IWAT-PARM3 IWAT-STATE1 <PLS > Initial conditions at start of simulation # - # RETS SURS 4 0 0 5 0 0 END IWAT-STATE1 END IMPLND SCHEMATIC <-Source-> <--Area--> <-Target-> MBLK <Name> # <-factor-> <Name> # Tbl# Basin 1*** PERLND 16 0.19 RCHRES 1 2 PERLND 16 0.19 RCHRES 1 3 IMPLND 4 1.11 RCHRES 1 5 IMPLND 5 0.14 RCHRES 1 5 ******Routing****** PERLND 16 0.19 COPY 1 12 IMPLND 4 1.11 COPY 1 15 IMPLND 5 0.14 COPY 1 is PERLND 16 0.19 COPY 1 13 RCHRES 1 1 COPY 501 16 END SCHEMATIC NETWORK <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Target vols> <-Grp> <-Member-> <Name> # <Name> # #<-factor->strg <Name> 4 4 <Name> # # COPY S01 OUTPUT MEAN 1 1 12.1 DISPLY 1 INPUT TIMSER 1 <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Target vols> <-Grp> <-Member-> <Name> # <Name> # #<-factor->strg <Name> # # <Name> # # END NETWORK RCHRES GEN-INFO RCHRES Name Nexits Unit Systems Printer # - #< ------------------ ><--- > User T-series Engl Metr LKFG in out 1 Vault 1 1 1 1 1 28 0 1 END GEN-INFO *** Section RCHRES*** ACTIVITY <PLS > Active Sections # HYFG ADFG CNFG HTFG SDFG GQFG OXFG NUFG PKFG PHFG 1 1 0 0 0 0 0 0 0 0 0 END ACTIVITY PRINT -INFO <PLS > Print -flags PIVL PYR # - # HYDR ADCA CONS HEAT SED GQL OXRX NUTR PLNK PHCB PIVL PYR 1 4 0 0 0 0 0 0 0 0 0 1 9 END PRINT -INFO HYDR-PARM1 Hwy 99_Vault 7/25/2019 4:13:33 PM Page 28 RCHRES Flags for each HYDR Section # - # VC Al A2 A3 ODFVFG for each ODGTFG for each FUNCT for each FG FG FG FG possible exit possible exit possible exit 0 1 0 0 4 0 0 0 0 0 0 0 0 0 2 2 2 2 2 END HYDR-PARM1 HYDR-PARM2 # - # FTABNO LEN DELTH STCOR KS DB50 < >< >< -------- >< -------- >< -------- >< -------- >< -------- > 1 0.03 0.0 0.0 0.5 0.0 END HYDR-PARM2 HYDR-INIT RCHRES Initial conditions for each HYDR section # - # VOL Initial value of COLIND Initial value of OUTDGT *** ac-ft for each possible exit for each possible exit < >< -------- > < --- >< --- >< --- >< --- >< > < --- >< --- >< --- >< --- >< > 0 4.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 END HYDR-INIT END RCHRES SPEC -ACTIONS END SPEC -ACTIONS FTABLES FTABLE 1 91 4 Depth Area Volume Outflowl Velocity Travel Time*** (ft) (acres) (acre-ft) (cfs) (ft/sec) (Minutes)*** 0.000000 0.135158 0.000000 0.000000 0.063889 0.135158 0.008635 0.00171S 0.127778 0.135158 0.017270 0.002425 0.191667 0.135158 0.025905 0.002970 0.255556 0.135158 0.034540 0.003430 0.319444 0.135158 0.043176 0.003834 0.383333 0.135158 0.051811 0.004200 0.447222 0.135158 0.060446 0.004537 0.511111 0.135158 0.069081 0.004850 O.S75000 0.135158 0.077716 0.005144 0.638889 0.135158 0.086351 0.005423 0.702778 0.135158 0.094986 0.005687 0.766667 0.13SlS8 0.103621 0.005940 0.830556 0.135158 0.1122S7 0.006183 0.894444 0.135158 0.120892 0.006416 0.958333 0.13SlS8 0.129527 0.006641 1.022222 0.135158 0.138162 0.006859 1.086111 0.135158 0.146797 0.007070 1.150000 0.135158 0.155432 0.007275 1.213889 0.1351S8 0.164067 0.007475 1.277778 0.1351S8 0.172702 0.007669 1.341667 0.135158 0.181338 0.007858 1.405556 0.13SlS8 0.189973 0.008043 1.469444 0.135158 0.198608 0.008224 1.533333 0.1351S8 0.207243 0.008401 1.597222 0.135158 0.21S878 0.008574 1.661111 0.135158 0.224513 0.008744 1.725000 0.135158 0.233148 0.008910 1.788889 0.135158 0.241783 0.009074 1.852778 0.1351S8 0.250418 0.009234 1.916667 0.135158 0.2S9054 0.009392 1.980556 0.13SlS8 0.267689 0.009548 2.044444 0.13S158 0.276324 0.009700 2.108333 0.135158 0.284959 0.009851 2.172222 0.13S158 0.293594 0.009999 2.236111 0.135158 0.302229 0.01014S 2.300000 0.135158 0.310864 0.010289 2.363889 0.135158 0.319499 0.010431 2.427778 0.135158 0.328135 0.01OS71 2.491667 0.135158 0.336770 0.010709 2.555S56 0.1351S8 0.345405 0.010845 2.619444 0.1351S8 0.354040 0.010980 Hwy 99_Vault 7/25/2019 4:13:33 PM I �h Page 29 2.683333 0.135158 0.362675 0.011113 2.747222 0.1351S8 0.371310 0.011245 2.811111 0.135158 0.379945 0.011375 2.875000 0.135158 0.388580 0.011503 2.938889 0.135158 0.397216 0.011630 3.002778 0.1351S8 0.405851 0.011756 3.066667 0.135158 0.414486 0.011880 3.130556 0.135158 0.423121 0.012004 3.194444 0.13S158 0.431756 0.012125 3.258333 0.135158 0.440391 0.012246 3.322222 0.135158 0.449026 0.012366 3.386111 0.135158 0.457661 0.012484 3.4SO000 0.135158 0.466296 0.012601 3.513889 0.135158 0.474932 0.012772 3.577778 0.135158 0.483S67 0.013543 3.641667 0.1351S8 0.492202 0.014672 3.7OS556 0.1351S8 0.500837 0.016035 3.769444 0.135158 0.509472 0.017578 3.833333 0.135158 0.518107 0.019264 3.897222 0.13SlS8 O.S26742 0.021067 3.961111 0.135158 0.535377 0.022968 4.02SO00 0.135158 0.544013 0.024948 4.088889 0.135158 O.SS2648 0.026994 4.1S2778 0.1351S8 0.561283 0.029095 4.216667 0.13SlS8 0.569918 0.031238 4.280556 0.135158 0.S785S3 0.033415 4.344444 0.1351S8 0.587188 0.035617 4.408333 0.13S158 0.595823 0.037835 4.472222 0.135158 0.6044S8 0.040062 4.S36111 0.13S158 0.613094 0.04254S 4.600000 0.135158 0.621729 0.04S285 4.663889 0.1351S8 0.630364 0.048102 4.727778 0.1351S8 0.638999 O.OS0993 4.791667 0.13S158 0.647634 O.OS3958 4.8SS5S6 0.13SlS8 0.656269 0.056994 4.919444 0.135158 0.664904 0.074S26 4 . 983333 0.135158 0.673539 0.078684 5.047222 0.13SlS8 0.682174 0.082930 5.111111 0.135158 0.690810 0.087261 5.175000 0.135158 0.699445 0.091677 S.238889 0.135158 0.708080 0.096176 5.302778 0.13S158 0.716715 0.289907 5.366667 0.13SlS8 0.725350 0.729357 5.430556 0.135158 0.733985 1.306089 S.494444 0.135158 0.742620 1.974634 S.558333 0.135158 0.751255 2.693872 5.622222 0.135158 0.759891 3.421531 S.686111 0.135158 0.768526 4.115337 5.750000 0.135158 0.777161 4.736782 END FTABLE 1 END FTABLES EXT SOURCES <-Volume-> <Member> SsysSgap<--Mult-->Tran <-Target vols> <-Grp> <-Member-> <Name> # <Name> # tem strg<-factor->strg <Name> # # <Name> WDM 2 PREC ENGL I PERLND 1 999 EXTNL PREC WDM 2 PREC ENGL 1 IMPLND 1 999 EXTNL PREC WDM I EVAP ENGL 0.76 PERLND 1 999 EXTNL PETINP WDM I EVAP ENGL 0.76 IMPLND 1 999 EXTNL PETINP END EXT SOURCES EXT TARGETS <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Volume-> <Member> Tsys Tgap Amd <Name> # <Name> # #<-factor->strg <Name> # <Name> tem strg strg*** RCHRES 1 HYDR RO 1 1 1 WDM 1000 FLOW ENGL REPL RCHRES 1 HYDR STAGE 1 1 1 WDM 1001 STAG ENGL REPL COPY 1 OUTPUT MEAN 1 1 12.1 WDM 701 FLOW ENGL REPL COPY 501 OUTPUT MEAN 1 1 12.1 WDM 801 FLOW ENGL REPL END EXT TARGETS Hwy 99-Vault 7/25/2019 4:13:33 PM Page 30 KASS-LINK <Volume> <-Grp> <-Member-><--Mult--> <Name> <Name> # #<-factor-> MASS -LINK 2 PERLND PWATER SURO 0.083333 END MASS -LINK 2 MASS -LINK 3 PERLND PWATER IFWO 0.083333 END MASS -LINK 3 MASS -LINK 5 IMPLND IWATER SURO 0.083333 END MASS -LINK 5 MASS -LINK 12 PERLND PWATER SURO 0.083333 END MASS -LINK 12 MASS -LINK 13 PERLND PWATER IFWO 0.083333 END MASS -LINK 13 MASS -LINK 15 IMPLND IWATER SURO 0.083333 END MASS -LINK 15 MASS -LINK 16 RCHRES ROFLOW END MASS -LINK 16 END MASS -LINK END RUN <Target> <-Grp> <-Member->*** <Name> <Name> # RCHRES INFLOW IVOL RCHRES INFLOW IVOL RCHRES COPY COPY COPY COPY INFLOW IVOL INPUT MEAN INPUT MEAN INPUT MEAN INPUT MEAN Hwy 99_Vault 7/25/2019 4:13:33 PM Page 31 11:11 redeveloped HSPF Message File Hwy 99_Vault 7/25/2019 4:13:33 PM Page 32 Mitigated HSPF Message File I ERROR/WARNING ID: 238 1 The continuity error reported below is greater than 1 part in 1000 and is therefore considered high. Did you specify any "special actions"? If so, they could account for it. Relevant data are: DATE/TIME: 1929/ 8/31 24: 0 RCHRES : 1 RELERR STORS STOR MATIN MATDIF -0.00447 0.00000 O.00OOE+00 0.00000 -6.098E-08 Where: RELERR is the relative error (ERROR/REFVAL). ERROR is (STOR-STORS) - MATDIF. REFVAL is the reference value (STORS+MATIN). STOR is the storage of material in the processing unit (land -segment or reach/reservior) at the end of the present interval. STORS is the storage of material in the pu at the start of the present printout reporting period. MATIN is the total inflow of material to the pu during the present printout reporting period. MATDIF is the net inflow (inflow -outflow) of material to the pu during the present printout reporting period. ERROR/WARNING ID: 238 1 The continuity error reported below is greater than 1 part in 1000 and is therefore considered high. Did you specify any "special actions"? If so, they could account for it. Relevant data are: DATE/TIME: 1955/ 9/30 24: 0 RCHRES : 1 RELERR STORS STOR MATIN MATDIF -1.066E-03 0.00000 O.00OOE+00 0.00000 -2.542E-07 Where: RELERR is the relative error (ERROR/REFVAL). ERROR is (STOR-STORS) - MATDIF. REFVAL is the reference value (STORS+MATIN). STOR is the storage of material in the processing unit (land -segment or reach/reservior) at the end of the present interval. STORS is the storage of material in the pu at the start of the present printout reporting period. MATIN is the total inflow of material to the pu during the present printout reporting period. MATDIF is the net inflow (inflow -outflow) of material to the pu during the present printout reporting period. ERROR/WARNING ID: 238 1 The continuity error reported below is greater than 1 part in 1000 and is therefore considered high. Did you specify any "special actions"? If so, they could account for it. Relevant data are: Hwy 99-Vault 7/25/2019 4:13:33 PM Page 33 DATE/TIME: 1960/ 8/31 24: 0 RCHRES 1 RELERR STORS STOR MATIN MATDIF -6.849E-03 0.00000 O.00OOE+00 0.00000 -3.969E-08 Where: RELERR is the relative error (ERROR/REFVAL). ERROR is (STOR-STORS) - MATDIF. REFVAL is the reference value (STORS+MATIN). STOR is the storage of material in the processing unit (land -segment or reach/reservior) at the end of the present interval. STORS is the storage of material in the pu at the start of the present printout reporting period. MATIN is the total inflow of material to the pu during the present printout reporting period. MATDIF is the net inflow (inflow -outflow) of material to the pu during the present printout reporting period. ERROR/WARNING ID: 238 1 The continuity error reported below is greater than 1 part in 1000 and is therefore considered high. Did you specify any "special actions"? If so, they could account for it. Relevant data are: DATE/TIME: 1964/ 9/30 24: 0 RCHRES 1 RELERR STORS STOR MATIN MATDIF -2.777E-01 0.00000 O.00OOE+00 0.00000 -7.029E-10 Where: RELERR is the relative error (ERROR/REFVAL). ERROR is (STOR-STORS) - MATDIF. REFVAL is the reference value (STORS+MATIN). STOR is the storage of material in the processing unit (land -segment or reach/reservior) at the end of the present interval. STORS is the storage of material in the pu at the start of the present printout reporting period. MATIN is the total inflow of material to the pu during the present printout reporting period. MATDIF is the net inflow (inflow -outflow) of material to the pu during the present printout reporting period. ERROR/WARNING ID: 238 1 The continuity error reported below is greater than I part in 1000 and is therefore considered high. Did you specify any "special actions"? If so, they could account for it. Relevant data are: DATE/TIME: 1966/ 8/31 24: 0 RCHRES 1 RELERR STORS STOR MATIN MATDIF -1.499E-01 0.00000 O.00OOE+00 0.00000 -l.S60E-09 Where: RELERR is the relative error (ERROR/REFVAL). ERROR is (STOR-STORS) - MATDIF. Hwy 99-Vault 7/25/2019 4:13:33 PM Page 34 REFVAL is the reference value (STORS+MATIN). STOR is the storage of material in the processing unit (land -segment or reach/reservior) at the end of the present interval. STORS is the storage of material in the pu at the start of the present printout reporting period. MATIN is the total inflow of material to the pu during the present printout reporting period. MATDIF is the net inflow (inflow -outflow) of material to the pu during the present printout reporting period. The count for the WARNING printed above has reached its maximum. If the condition is encountered again the message will not be repeated. Hwy 99_Vault 7/25/2019 4:13:33 PM Page 35 Disclaimer Legal Notice This program and accompanying documentation are provided 'as-is'without warranty of any kind. The entire risk regarding the performance and results of this program is assumed by End User. Clear Creek Solutions Inc. and the governmental licensee or sublicensees disclaim all warranties, either expressed or implied, including but not limited to implied warranties of program and accompanying documentation. In no event shall Clear Creek Solutions Inc. be liable for any damages whatsoever (including without limitation to damages for loss of business profits, loss of business information, business interruption, and the like) arising out of the use of, or inability to use this program even if Clear Creek Solutions Inc. or their authorized representatives have been advised of the possibility of such damages. Software Copyright@ by: Clear Creek Solutions, Inc. 2005-2019; All Rights Reserved. Clear Creek Solutions, Inc. 6200 Capitol Blvd. Ste F Olympia, WA. 98501 Toll Free 1(866)943-0304 Local (360)943-0304 www.clearcreeksolutions.com Hwy 99_Vault 7/25/2019 4:13:33 PM Page 36 STORMWATER SITE PLAN APPENDIX B BMP INFEASIBILITY STUDY NAVIX Highway 99 Edmonds — Edmonds, WA Page 49 STORM WATER SITE PLAN BIVIP IhIlk- Post- Construction Soil Quality and Depth Infeasibility Criteria Lawn and landscape area is on till slopes greater than 33 percent Feasible? Yes/No Yes Reason(s) Infeasibility On -site disturbed areas that are not covered by structure will be amended with compost or replaced with topsoil meeting Post - Construction Soil Quality and Depth requirements. Full Dispersion * Where the dispersion area is within the North Edmonds No A minimum flow path Earth Subsidence and Landslide Hazard Area (ESLHA). cannot be met due to the * The flow path or dispersal area is within the buffer of the zero -lot line development ESLHA (minimum buffer equal to the height of the steep slope project. or 50 feet, whichever is greater) unless a geotechnical assessment and soils report is prepared addressing the potential impact of the proposed system. e The slope of the flow path or dispersal area is steeper than 15 percent for any 20-foot reach of the flow path, or steeper than 33 percent if a level spreader is used upstream and vegetation is established. a The flow path or dispersal area is within 50 feet of the top of slopes greater than 15 percent (unless a geotechnical assessment and soils report is prepared addressing the potential impact of the proposed system). * A 65 to 10 ratio of forested or native vegetation area to impervious area cannot be achieved. * A minimum forested or native vegetation flow path length of 100 feet (25 feet for sheet flow from a nonnative pervious surface) cannot be achieved. * The flow path cannot be located on site or in a reserved offsite tract or easement area. * The flow path cannot be located between the dispersion device and any downstream drainage feature such as a pipe, ditch, stream, river, pond, lake, or wetland. * Flow paths for adjacent dispersion devices cannot be sufficiently spaced to prevent overlap of flows in the flow path areas e For sites with onsite or adjacent septic systems, the discharge point must be at least 30 feet upgradient, or 10 feet downgradient, of the drain field primary and reserve areas (per WAC 246-272A-0210). This requirement can be modified by the City if site topography will clearly prohibit flows from intersecting the drain field or where site conditions (soil permeability, distance between systems, etc.) indicate that this is unnecessary. 9 The dispersion area is within the buffer of a Category 1 or Category 2 wetland. NAVIX Highway 99 Edmonds — Edmonds, WA Page 50 STORMWATER SITE PLAN e The dispersion area is within the buffer of a Category 3 or Category 4 wetland, except for the outer 25 percent of the buffer. : The dispersion of runoff would create flooding or erosion impacts Downspout * Where the infiltration system is within the North Edmonds No The project site contains Full Infiltration Earth Subsidence and Landslide Hazard Area (ESLHA). dense till soils that have Systems * Within the buffer of the ESLHA (minimum buffer equal to been determined to be the height of the steep slope or 50 feet, whichever is greater) impermeable by the unless a geotechnical assessment and soils report is prepared addressing the potential impact of the proposed system. project geotechnical * Within 50 feet of the top of slopes greater than 15 percent engineer's investigation. (unless a geotechnical assessment and soils report is prepared addressing the potential impact of the proposed system). According to the 9 The lot(s) or site does not have outwash or loam soils. * geotechnical report There is not at least 3 feet or more of permeable soil from the (Appendix A), the on -site proposed final grade to the seasonal high groundwater table borings indicated very or other impermeable layer. dense glacial till to the * There is not at least 1 foot or more of permeable soil from depth of about 31-40 feet the proposed bottom of the infiltration system to the seasonal high groundwater table or other impermeable layer. below existing site grade. • Within 5 feet from any property lines and easements. Proposed final grades will • If the contributing area is less than 5,000 square feet, within not allow for 3 feet or 5 feet from a structure without a basement and 10 feet for a more of permeable soil. structure with a basement. * If the contributing area is greater than or equal to 5,000 square feet, within a lHorizontal:lVertical slope line from the bottom edge of the facility to a structure. (Minimum clearance 5 feet from a structure with a basement and 10 feet for a structure with a basement.) * For sites with onsite or adjacent septic systems, the discharge point must be at least 30 feet upgradient, or 10 feet downgradient, of the drain field primary and reserve areas (per WAC 246-272A-0210). This requirement can be modified by the City if site topography will clearly prohibit flows from intersecting the drain field or where site conditions (soil permeability, distance between systems, etc.) indicate that this is unnecessary. 9 If placed in fill material, the measured infiltration rate is less than 8 inches per hour. * If placed under pavement, overflow cannot be sited at least 1 foot below the pavement (i.e., to prevent saturation of the pavement if system falls). • Within the buffer of a Category 1 or Category 2 wetland. • Within the buffer of a Category 3 or Category 4 wetland, except for the outer 25 percent of the buffer. Bioretention Note: Criteria with setback distances are as measured from No Geotechnical investigation or Rain the bottom edge of the bioretention soil mix. Citation of any has determined that on - Gardens of the following infeasibility criteria must be based on an site soils are evaluation of site -specific conditions and a written impermeable, with NAVIX Highway 99 Edmonds — Edmonds, WA Page 51 STORMWATER SITE PLAN recommendation from an appropriate licensed professional measured rates well (e.g., engineer, geologist, hydrogeologist): below the 0.3 inches/hour * Where professional geotechnical evaluation recommends minimum rate required. infiltration not be used due to reasonable concerns about erosion, slope failure, or downgradient flooding. * Where the only area available for siting would threaten the safety or reliability of pre-existing underground utilities, pre- existing underground storage tanks, pre-existing structures, or pre-existing road or parking lot surfaces. o Where the only area available for siting does not allow for a safe overflow pathway to stormwater drainage system or private storm sewer system. e Where there is a lack of usable space for bioretention/rain garden areas at development sites, or where there is insufficient space within the existing public right-of-way on public road projects. * Where infiltrating water would threaten shoreline structures such as bulkheads. The following criteria can be cited as reasons for infeasibility without further justification (though some require professional services to make the observation): 9 Where the system is within the North Edmonds Earth Subsidence and Landslide Hazard Area (ESLHA). * Within the buffer of the ESLHA (minimum buffer equal to the height of the steep slope or 50 feet, whichever is greater) unless a geotechnical assessment and soils report is prepared addressing the potential impact of the proposed system. * Within 50 feet of the top of slopes greater than 15 percent (unless a geotechnical assessment and soils report is prepared addressing the potential impact of the proposed system). 9 Where they are not compatible with surrounding drainage system as determined by the City (e.g., project drains to an existing stormwater collection system whose elevation or location precludes connection to a properly functioning bioretention/rain garden area). 9 Where the site cannot be reasonably designed to locate bioretention/rain garden areas on slopes less than 8 percent. o Properties with known soil or groundwater contamination (typically federal Superfund sites or state cleanup sites under the Model Toxics Control Act [MTCA]): o Within 100 feet of an area known to have deep soil contamination. o Where groundwater modeling indicates infiltration will likely increase or change the direction of the migration of pollutants in the groundwater. o Wherever surface soils have been found to be contaminated unless those soils are removed within 10 horizontal feet from the infiltration area. o Any area where these facilities are prohibited by an approved cleanup plan under the state Model Toxics Control Act or Federal Superfund Law, or an environmental covenant under Chapter 64.70 RCW. NAVIX Highway 99 Edmonds — Edmonds, WA Page 52 STORMWATER SITE PLAN * For sites with onsite or adjacent septic systems, the discharge point must be at least 30 feet upgradient, or 10 feet clowngradient, of the drainfield primary and reserve areas (per WAC 246-272A-0210). This requirement can be modified by the City if site topography will clearly prohibit flows from intersecting the drain field or where site conditions (soil permeability, distance between systems, etc.) indicate that this is unnecessary. * Within 10 feet of an underground storage tank and connecting underground pipes when the capacity of the tank and pipe system is 1,100 gallons or less. As used in these criteria, an underground storage tank means any tank used to store petroleum products, chemicals, or liquid hazardous wastes of which 10 percent or more of the storage volume (including volume in the connecting piping system) is beneath the ground surface. * Within 100 feet of an underground storage tank and connecting underground pipes when the capacity of the tank and pipe system is greater than 1,100 gallons. * Where field testing indicates potential bioretention/rain garden sites have a measured (a.k.a., initial) native soil saturated hydraulic conductivity less than 0.30 inches per hour. A small-scale or large-scale PIT in accordance with Appendix B shall be used to demonstrate infeasibility. If the measured native soil infiltration rate is less than 0.30 in/hour, bioretention/rain garden BMPs are not required to be evaluated as an option in List No. 1 or List No. 2. In these slow draining soils, a bioretention area with an underdrain may be used to treat pollution -generating surfaces to help meet Minimum Requirement No. 6. If the underdrain is elevated within a base course of gravel, it will also provide some modest flow reduction benefit that will help achieve Minimum Requirement No. 7. * Where the minimum vertical separation of 3 feet to the seasonal high groundwater elevation or other impermeable layer would not be achieved below bioretention that would serve a drainage area that exceeds the following thresholds (and cannot reasonably be broken down into amounts smaller than indicated): o 5,000 square feet of poll ution-generati ng impervious surface (PGIS) o 10,000 square feet of impervious area o 0.75 acres of lawn and landscape. Where the minimum vertical separation of I foot to the seasonal high groundwater or other impermeable layer would not be achieved below bioretention that would serve a drainage area less than the above thresholds. * If the contributing area is less than 5,000 square feet, within 5 feet from a structure without a basement and 10 feet for a structure with a basement. NAVIX Highway 99 Edmonds — Edmonds, WA Page 53 STORMWATER SITE PLAN e If the contributing area is greater than or equal to 5,000 square feet, within a lHorizontal:lVertical slope line from the bottom edge of the facility to a structure. (Minimum clearance 5 feet from a structure with a basement and 10 feet for a structure with a basement.) * Within 5 feet from any property lines and easements. • Within the buffer of a Category 1 or Category 2 wetland. • Within the buffer of a Category 3 or Category 4 wetland, except for the outer 25 percent of the buffer. Downspout e Where dispersion area is within the North Edmonds Earth No The minimum flow path Dispersion Subsidence and Landslide Hazard Area (ESLHA). required is not available at Systems * Within the buffer of the ESLHA (minimum buffer equal to this site due to the nature the height of the steep slope or 50 feet, whichever is greater) of a zero -lot line unless a geotechnical assessment and soils report is prepared addressing the potential impact of the proposed system. development. * For splashblocks, a vegetated flowpath at least 50 feet in Additionally, on -site soils length from the downspout to the downstream property line, have been determined to structure, stream, wetland, slope over 15 percent (unless a be impermeable by the geotechnical assessment and soils report is prepared geotechnical engineer's addressing the potential impact of the proposed system), or on -site soils investigation. other impervious surface is not feasible. * For trenches, a vegetated flowpath of at least 25 feet in between the outlet of the trench and any property line, structure, stream, wetland, or impervious surface is not feasible. A minimum vegetated flowpath of at least 50 feet between the outlet of the trench and any slope steeper than 15 percent is not feasible (unless a geotechnical assessment and soils report is prepared addressing the potential impact of the proposed system). * For trenches, a trench width of at least 10 feet is not feasible. * Flowpaths for adjacent dispersion devices cannot be sufficiently spaced to prevent overlap of flows in the flowpath areas. * For trenches within 5 feet from any property lines and easements. 9 For sites with onsite or adjacent septic systems, the discharge point must be at least 30 feet upgradient, or 10 feet clowngradient, of the drainfield primary and reserve areas (per WAC 246-272A-0210). This requirement can be modified by the City if site topography will clearly prohibit flows from intersecting the drainfield or where site conditions (soil permeability, distance between systems, etc.) indicate that this is unnecessary. • Within the buffer of a Category I or Category 2 wetland. • Within the buffer of a Category 3 or Category 4 wetland, except for the outer 25 percent of the buffer. Perforated * Where the system is within the North Edmonds Earth No Geotechnical investigation Stub -Out Subsidence and Landslide Hazard Area (ESLHA). shows no permeable soils Connections * Within the buffer of the ESLHA (minimum buffer equal to on site. the height of the steep slope or 50 feet, whichever is greater) NAVIX Highway 99 Edmonds — Edmonds, WA Page 54 STORMWA TER SITE PLAN unless a geotechnical assessment and soils report is prepared addressing the potential impact of the proposed system. * Within 50 feet of the top of slopes greater than 15 percent (unless a geotechnical assessment and soils report is prepared addressing the potential impact of the proposed system). * There is not at least I foot of permeable soil from the proposed bottom of the perforated stub -out connection trench to the highest estimated groundwater table or other impermeable layer. 9 The only location available for the perforated stub -out connection is under impervious or heavily compacted soils. * For sites with onsite or adjacent septic systems, the discharge point must be at least 30 feet upgradient, or 10 feet clowngradient, of the drainfield primary and reserve areas (per WAC 246-272A-0210). This requirement can be modified by the City if site topography will clearly prohibit flows from intersecting the drain field or where site conditions (soil permeability, distance between systems, etc.) indicate that this is unnecessary. • Within the buffer of a Category I or Category 2 wetland. • Within the buffer of a Category 3 or Category 4 wetland, except for the outer 25 percent of the buffer Detention Subject to review and approval by the City; infeasibility may be Yes A detention vault has Vaults and determined when a project meets any of the following been sized using WWHM Pipes infeasibility criteria: 2012 to account for the * Where the downstream analysis in Minimum Requirement lack of other On -Site No. 4, or available City data, indicate that peak flow control from the site is not beneficial. Stormwater Management * Where there is less than 1,000 square feet of contributing BMPs (Appendix A). site impervious surfaces that are not proposed to be managed by other On -Site Stormwater Management BMPs. (This includes combining of areas from multiple types of surfaces listed under the list options for Minimum Requirement No. 5, e.g., roofs and other hard surfaces.) 9 Where there is not a downstream drainage system that allows for connection to the City storm system or an appropriate dispersion and overflow path. Full Dispersion * See Full Dispersion under "Roofs" section above. No Geotechnical investigation shows no permeable soils on site. Permeable Citation of any of the following infeasibility criteria must be No Refer to geotechnical Pavement based on an evaluation of site -specific conditions and a report, Appendix D. written recommendation from an appropriate licensed professional (e.g., engineer, geologist, hydrogeologist): Geotechnical investigation e Where professional geotechnical evaluation recommends reports soils with low soil infiltration not be used due to reasonable concerns about infiltration rate of .05-.15 erosion, slope failure, or clowngradient flooding. * Where infiltrating and poncled water below the new inches per hour. permeable pavement area would compromise adjacent impervious pavements. NAVIX Highway 99 Edmonds — Edmonds, WA Page 55 STORM WATER SITE PLAN e Where infiltrating water below a new permeable pavement area would threaten existing below grade basements. 9 Where infiltrating water would threaten shoreline structures such as bulkheads. 9 Down slope of steep, erosion prone areas that are likely to deliver sediment. 9 Where fill soils are used that can become unstable when saturated. a Excessively steep slopes where water within the aggregate base layer or at the subgrade surface cannot be controlled by detention structures and may cause erosion and structural failure, or where surface runoff velocities may preclude adequate infiltration at the pavement surface. * Where permeable pavements cannot provide sufficient strength to support heavy loads at industrial facilities such as ports. 9 Where installation of permeable pavement would threaten the safety or reliability of pre-existing underground utilities, pre-existing underground storage tanks, or pre-existing road subgrades. The following criteria can be cited as reasons for infeasibility without further justification (though some require professional services to make the observation): ;Where the permeable pavement is within the North dmonds Earth Subsidence and Landslide Hazard Area (ESLHA). 9 Within the buffer of the ESLHA (minimum buffer equal to the height of the steep slope or 50 feet, whichever is greater) unless a geotechnical assessment and soils report is prepared addressing the potential impact of the proposed system. * Within 50 feet of the top of slopes greater than 15 percent (unless a geotechnical assessment and soils report is prepared addressing the potential impact of the proposed system). * For sites with onsite or adjacent septic systems, the discharge point must be at least 30 feet upgradient, or 10 feet downgradient, of the drain field primary and reserve areas (per WAC 246-272A-0210). This requirement can be modified by the City if site topography will clearly prohibit flows from intersecting the drain field or where site conditions (soil permeability, distance between systems, etc.) indicate that this is unnecessary. 0 Within 10 feet of any underground storage tank and connecting underground pipes, regardless of tank size. As used in these criteria, an underground storage tank means any tank used to store petroleum products, chemicals, or liquid hazardous wastes of which 10 percent or more of the storage volume (including volume in the connecting piping system) is beneath the ground surface. e At multi -level parking garages, and over culverts and bridges. NAVIX Highway 99 Edmonds — Edmonds, WA Page 56 STORMWATER SITE PLAN * Where the site design cannot avoid putting pavement in areas likely to have long-term excessive sediment deposition after construction (e.g., construction and landscaping material yards). * Where the site cannot reasonably be designed to have a porous asphalt surface at less than 5 percent slope, or a pervious concrete surface at less than 10 percent slope, or a permeable interlocking concrete pavement surface (where appropriate) at less than 12 percent slope. Grid systems upper slope limit can range from 6 to 12 percent; check with manufacturer and local supplier. * Where the subgrade soils below a poll ution-generati ng permeable pavement (e.g., road or parking lot) do not meet the soil suitability criteria for providing treatment. See soil suitability criteria for treatment in SWMMWW, Volume 111, Section 3.3.7. Note: In these instances, the City may approve installation of a 6-inch sand filter layer meeting City specifications for treatment as a condition of construction. * Where underlying soils are unsuitable for supporting traffic loads when saturated. Soils meeting a California Bearing Ratio of 5 percent are considered suitable for residential access roads. * Where appropriate field testing indicates soils have a measured (a.k.a., initial) subgrade soil saturated hydraulic conductivity less than 0.3 inches per hour. A small-scale or large-scale PIT in accordance with Appendix B shall be used to demonstrate infeasibility. (Note: In these instances, unless other infeasibility restrictions apply, roads and parking lots may be built with an underdrain, preferably elevated within the base course, if flow control benefits are desired.) a Roads that receive more than very low traffic volumes, and areas having more than very low truck traffic. Roads with a projected average daily traffic volume of 400 vehicles or less are very low volume roads (AASHTO 2001) (U.S. Department of Transportation 2013). Areas with very low truck traffic volumes are roads and other areas not subject to through truck traffic but may receive up to weekly use by utility trucks (e.g., garbage, recycling), daily school bus use, and multiple daily use by pick-up trucks, mail/parcel delivery trucks, and maintenance vehicles. Note: This infeasibility criterion does not extend to sidewalks and other non -traffic bearing surfaces associated with the collector or arterial. * Where replacing existing impervious surfaces unless the existing surface is a non -pollution generating surface over an outwash soil with a saturated hydraulic conductivity of 4 inches per hour or greater. * At sites defined as "high -use sites." For more information on high -use sites, refer to the Glossary in SWMMWW, Volume 1. * In areas with "industrial activity" as identified in 40 CFR 122.26(b)(14). NAVIX Highway 99 Edmonds — Edmonds, WA Page 57 STORM WATER SITE PLAN * Where the risk of concentrated pollutant spills is more likely such as gas stations, truck stops, and industrial chemical storage sites. * Where routine, heavy applications of sand occur in frequent snow zones to maintain traction during weeks of snow and ice accumulation. 9 Where the seasonal high groundwater or an underlying impermeable/low permeable layer would create saturated conditions within 1 foot of the bottom of the lowest gravel base course. • Within the buffer of a Category I or Category 2 wetland. • Within the buffer of a Category 3 or Category 4 wetland, except for the outer 25 percent of the buffer. Bioretention * See Bioretention or Rain Gardens under "Roofs" section No The impermeable nature or Rain above. of the soils would lead to Gardens flooding and erosion concerns on site. Sheet Flow Where the dispersion area is within the North Edmonds No The required vegetated Dispersion Earth Subsidence and Landslide Hazard Area (ESLHA). buffer is not available at a Within the buffer of the ESLHA (minimum buffer equal to this site. Sheet flow the height of the steep slope or 50 feet, whichever is greater) dispersion would lead to unless a geotechnical assessment and soils report is prepared addressing the potential impact of the proposed system. flooding and erosion e Where the dispersion area is within 50 feet of the top of concerns due to the slopes greater than 15 percent (unless a geotechnical impermeable nature of assessment and soils report is prepared addressing the the existing soils. potential impact of the proposed system). • Positive drainage for sheet flow runoff cannot be achieved. • Area to be dispersed (e.g., driveway, patio) cannot be graded to have less than a 15 percent slope. * For flat to moderately sloped areas, at least a 10-foot-wide vegetation buffer for dispersion of the adjacent 20 feet of contributing surface cannot be achieved. For variably sloped areas, at least a 25-foot vegetated flow path between berms cannot be achieved. * The dispersion of runoff would create flooding or erosion impacts. * For sites with onsite or adjacent septic systems, the discharge point must be at least 30 feet upgradient, or 10 feet downgradient, of the drain field primary and reserve areas (per WAC 246-272A-0210). This requirement can be modified by the City if site topography will clearly prohibit flows from intersecting the drain field or where site conditions (soil permeability, distance between systems, etc.) indicate that this is unnecessary. * The dispersion area is within the buffer of a Category 1 or Category 2 wetland. NAVIX Highway 99 Edmonds — Edmonds, WA Page 58 STORMWATER SITE PLAN e The dispersion area is within the buffer of a Category 3 or Category 4 wetland, except for the outer 25 percent of the buffer. Concentrated * Where the dispersion area is within the North Edmonds No The required flow paths Flow Earth Subsidence and Landslide Hazard Area (ESLHA). cannot be provided at this Dispersion * Within the buffer of the ESLHA (minimum buffer equal to site. the height of the steep slope or 50 feet, whichever is greater) unless a geotechnical assessment and soils report is prepared Runoff will not be able to addressing the potential impact of the proposed system. drain into the dense till * A minimum vegetated flow path of 50 feet between the discharge point and the top of slopes greater than 15 percent soil. is not feasible (unless a geotechnical assessment and soils report is prepared addressing the potential impact of the proposed system). * A minimum 3-foot length of rock pad and 50-foot flow path OR a dispersion trench and 25-foot flow path for every 700 sq. ft. of drainage area (within applicable setbacks) cannot be achieved. 9 More than 700 square feet drainage area drains to any dispersion device. * The dispersion of runoff would create flooding or erosion impacts. * A minimum vegetated flow path of 50 feet (if using rock pads) or 25 feet (if using dispersion trenches) between the discharge point and any property line, structure, stream, lake, wetland, or other impervious surface is not feasible. e For sites with onsite or adjacent septic systems, the discharge point must be at least 30 feet upgradient, or 10 feet downgradient, of the drain field primary and reserve areas (per WAC 246-272A-0210). This requirement can be modified by the City if site topography will clearly prohibit flows from intersecting the drain field or where site conditions (soil permeability, distance between systems, etc.) indicate that this is unnecessary. * The dispersion area is within the buffer of a Category 1 or Category 2 wetland. e The dispersion area is within the buffer of a Category 3 or Category 4 wetland, except for the outer 25 percent of the buffer. Detention See Detention Vaults and Pipes under "Roofs" section above Yes A detention vault has Vaults and been sized using WWHM Pipes 2012 to account for the lack of other On -Site Stormwater Management BMPs (Appendix A). NAVIX Highway 99 Edmonds — Edmonds, WA Page 59 STORMWATER SITE PLAN rT" I a a: 10 - 11 YAWO OPERATIONS AND MAINTENANCE MANUAL NAVIX Highway 99 Edmonds — Edmonds, WA Page 60 STORM WATER SITE PLAN No. 3 - Closed Detention Systems (Tanks/Vaults) Maintenance Detect Conditions When MaIntenance is Needed Resuits Expected Component When Maintenance Is Performed Storage Area Plugged Air Vents One-half of the cross secibon of a vent is Vents open and blocked at any point or the vent is damaged. functioning, Debris and Sediment Accumulated sediment depth exceeds 10% All sediment and of the diameter of the storage area for 112 debris removed from length of storage vault or any point depth storage area. exceeds 15% of diameler. (Example: 72-inch storage tank would require cleaning when sedirrient reaches depth of 7 inches for more than 1/2 length of tank.) Joints Between Any open ings or voids allowi ng material to All joint between TankPipe Section be transported into facility. tankipipe sections (Will require engtneenng analysis to are sealed. determine structural stability). Tank Pipe Bent Out Any part of lankdpipe is bent out of shape Tankipipe repaired or of Shape more than 10% of its design shape. (Review replaced to design. required by engineer to determine structural stability). Vault Structure Cracks wider than 1/2-inch and any Vault replaced or Includes Cracks in evidence of soil particles entering the repaired to desig n Wall, Bottom, structure through the cracks- or specifications and is Damage to Frame mainlenance/inspeclion personnel structurally sound. arid�or Top Slab determines that the vault vs not structurally sou nd. Cracks wider than 112-inch at the joint of any No cracks more than inleVoutlel pi�pe or any evidence of soil 1114-inuh wide at the particles entering the vau It through the walls. joint of the inlevoutlet pipe. Manhole Cover Not in Place Cover is missing or only partially in place. Manhole is closed. Any open mantiole requires malritenance. Locking Mechanism Mechanism cannot be opened by one Mechanism opens Not Working mainlena nee person with proper tools. Bolts with proper tools. into frame have less than 1/2 inch of thread (may not apply to self-locking lids). Cover Difficult to One maintenance person cannot remove lid Cover can be Remove after applying normal lifting pressure. Intent removed and is to keep cover from sealing off access to reinstalled by one mainleriance. mainlenance person. Ladder Rungs Unsafe Ladder is unsafe due to missing rungs, Ladder meets design misalignment, not securely attached to standards. Allows structure wall, rust, or cracks. maintenance person safe access - Catch Basins See "Catch Basins' See "Catch Basins' (No. 5). See 'Catch Basins' (No. 5) (No. 5). NAVIX Highway 99 Edmonds — Edmonds, WA Page 61 STORM WATER SITE PLAN No. 4 - Control Structure/Flow Restrictor Maintenance Defect Condition When Maintenance Is Needed Results Expected Component When Maintenance Is Performed General Trash and Debris Material exceeds 251Y. of sump depth or 1 Control structure (includes Sediment) foot below orifice plate. orifice is not blocked. All trash and debris removed. Structural Damage Structure isnot securely attached to Structure securely manhole wall. attached to wall and outlet pipe� Structure is not in upright position (allow up Structure in correct to 10% from plum b). position. Connections to ouiltet pipe are not watertight Connections to outlet and show signs of rust. pipe are water tight: structure repaired or replaced and works as designed. Any holes --other than designed holes —in the structure. Structure has no holes other than designed holes. Cleanout Gale Damaged or Missing Cleanout gate is not watertight or is missing- Gate is watertight and works as designed. Gate cannot be moved up and do%yn by one Gate moves up and maintenance person. down easily and is watertight. Chainfrod leading to gate is missing or Chain is in place and damaged. works as designed. Gate �is rusted over 50% of its surface area. Gate is repaired or replaced to meet design standards. Orifice Plate Damaged or Missing ControJ dewce is not working properly due to missing, out of place, or bent orifice plate. Piate is in place and works as desogned. Obstructions Any trash, debris, sediment. or vegetation Plate is free of all blocking theplate. obstructions and works as designed. Overflow Pipe Obstructions Any trash or debris blocking (or having the PLpe is free of all potential of blocking) the overflow pipe- obstructions and works as designed. Manhole See "Closed See "Closed Detention Systems" (No. 3). See "Closed Detention Systems' Detention Systems' (No. 3). (No. 3)_ Catch Basin See "Catch Basins' See 'Catch Basins" (No. 5). See "Catch Basins" (No. 5). (No� 6)_ NAVIX Highway 99 Edmonds — Edmonds, WA Page 62 STORMWATER SITE PLAN No. 5 — Catch Basins Maintenance Defect Conditions When Maintenance Is Needed Results Expected Whm Component MaIntenance Is performed General Trash & Trash or debris which is located immediately No Trash or debris located Debris in front of the catch basin opening or is immediately in front of blocking infetting capacity of the basin by cat& basin or on grate more than 10%. opening. Trash or debris (in the basin) that exceeds 60 No trash or debris in the percent of the sump depth as measured from catch basin. the bottom of basin to invert of the lowest pipe into or out of the basin, but in no case less than a minimum of six inches clearance from the debris surface to the invert of the [Mest pipe. Trash or debris in any inlet or outlet pipe Inlet and outlet pipes free blocking more than U3 of its height. of trash or debris. Dead animaks or vegetation that could No dead animals or generate odors that could cause complaints or dangerous gases (e.g., melhane)- vegetation present within the cat& basin. Sediment Sediment (in the basin) that exceeds 60 No sediment in the catch percent of the sump depth as measured from basin the bottom of basin to invert of the lowest pipe into or out of the -basin, but in no case less than a minimum of 6 inches clearance from the sediment surface to the invert of the towest pipe. Structure Damage to Top sLat) has holes larger than 2 square inches or cracks wider than 114 inch Top slab is free of holes and cracks. Frame andfor Top Slab (Intent is to make sure no material is running into besin). Frame not silting flush on top slab, i.e., Frame is sitting flush on separalban of rnare than 314 inch of the ftame the riser rings or top slab from the top slab. Frame not securely and firm ly allachad. allached Fractures or Maintenance person judges that structure is, Basin repLaced or repaired Cracks in unsound. to design standards. Basin Wall&/ Bottom Grout fillet has separated or cracked wider Pipe is regrouted and than 112 inch and longer than I foot at the secure at basin wall. loint of any inletloullet pipe or any evidence of ,Oil particles entering cat& basin through cracks. SelfiemenlY If failure of basin has created a safety, Basin replaced or repaired Misalignment function. or design problem. to design standards. Vogelal, on Vegetation growing across and blocking more than 10% of the basin opening. No vegetation blocking opening to basin. Vegetation grovAng in inletloutlet pipe joints No vegetation or root that is more than six inches tall and less than growth present - six inches a,RarL I I Contaminabon I See "Detention Ponds" (No. 1). I No pol-lutton present. and Pollution NAVIX Highway 99 Edmonds — Edmonds, WA Page 63 STORM WATER SITE PLAN No. S - Catch Basins Maintenance Defect Conditions When Maintenance Is Needed 'ResultsExpected When component "nionance Is performed Catch Basin Cover Not in Cover is missing or only partially in place. Catch basin cover is Cover Place Any open catch basin requires maintenance. closed Locking IvIecftanism cannot be opened by one Mechanism opens with Mechanism maintenance person with proper tools. Bolts proper tools. Not Working into frame haveless than 112 inch of thread. Cover Difficult One maintenance person cannot remove lid, Cover can be removed by to Remove after applying normal lifting pressure- one maintenance person. (Intent is keep cover from sealing off access to maintenance.) Ladder Ladder Rungs Ladder is unsafe due to missing rungs, not Ladder meets design Unsafe securely attached to basin wall, standards and allows misalignment, rust- cracks, or sharp edges. maintenance person safe acciess. Metal Grates (If Applicable) Grate opening Unsafe Grate with opening wider than 718 inch. Grate opening meets design standards. Trash and Trash and debris that is blocking more than Grate free of trash and Debris 20% of grate surface intetting capacity. debris. Damaged or Grate mssing or broken membeqs) of the Grate is in place and Missing. grate. meets design standards. NAVIX Highway 99 Edmonds - Edmonds, WA Page 64 STORMWATER SITE PLAN No. 18 — Catchbasin Inserts Maintenance Defect Conditions Whan Maintanarme is Results Expected When Component Needed Maintenance Is Performed Gene,al Sediment When sediment forms a cap over the No sediment cap on the insert Accumulation insert media of the insert and?or u n it- media and its unit - Trash and Trash and debris accumulates on insert Trash and debris removed Debris unit creating a blockageftestriction.. ftorn insert unit. Runoff freely Accumulation flows into catch basin. Media Insert Not Effluent water from media insert has a Effluent water from media Removing Oil visible sheen- insert is free of oils and has no visible sheen. Media Insert Catch basin insert is saturated with water Remove and replace media Water Saturated and no longer has the capacity to insert absorb. Media Insert-00 Media oil saturated due to petroleum split Remove and replace media Saturated that drains into cat& basin. insert. Media Insert Use Beyond Normal Media has been used beyond the typical average life of media insert product. Remove and replace media at regular intervals, depending on Product Life I insert product. NAVIX Highway 99 Edmonds — Edmonds, WA Page 65 STORMWA TER SITE PLAN APPENDIX D GEOTECHNICAL ENGINEERING REPORT NAVIX Highway 99 Edmonds — Edmonds, WA Page 66 GEOTECHNICAL ENGINEERING REPORT Proposed Edmonds Apartments 23326 Highway 99 Edmonds, Washington Project No. 1948.02 November 20, 2018 Prepared for: Goodman Real Estate Prepared by: Zipper Geo Associates, LLQ Geotechnical and Environmental Consultants 19019 36th Avenue West, Suite E Lynnwood, WA 9803 ZipperGeo Geoprofessional Consultants Project No. 1948.02 November 20, 2018 Goodman Real Estate 2801 Alaska Way, #310 Seattle, WA 98121 Attention: Mr. Tim Dickerson Subject: Geotechnical Engineering Report Proposed Edmonds Apartments 23326 Highway 99 Edmonds, Washington Dear Dickerson, in accordance with your request and written authorization, Zipper Geo Associates, LLC (ZGA) has completed the subsurface explorations and geotechnical engineering report for the proposed Edmonds Apartments project. This report presents the findings of the subsurface exploration and geotechnical recommendations for the project. Our work was completed in general accordance with our Proposol for Geotechnical Services (Proposal No. P1948.01) dated October 15, 2018. Written authorization to proceed was provided you on January 2, 2018. We appreciate the opportunity to be of service to you on this project. If you have any questions concerning this report, or if we may be of further service, please contact us. Sincerelx/ I Zipper Geo Associates, LL 17M'X�kv Robert A. Ross, P.E. Principal Geotechnical Er Copies: Addressee (1) Studio Meng Strazzara (1) Cary Kopczynski & Company (1) Navix Engineering (1) 1901936 1h Avenue West, Suite E Lynnwood, WA 98036 (425) 582-9928 TABLE OF CONTENTS Page INTRODUCTION........................................................................................................................................... I PROJECTUNDERSTANDING ..................................................................................................................... 1 SURFACECONDITIONS ............................................................................................................................. 2 SUBSURFACECONDITIONS ...................................................................................................................... 2 SoilConditions ................................................................................................................................................. 2 GroundwaterConditions ................................................................................................................................. 3 Summaryof Laboratory Testing ...................................................................................................................... 3 CONCLUSIONS AND RECOMMENDATIONS ............................................................................................ 4 General.......................................................................................................................................................... 4 GeologicallyHazardous Ares ........................................................................................................................... 4 Seismic Design Considerations ........................................................................................................................ 4 SitePreparation ............................................................................................................................................... 6 Structural Fill Materials and Preparation ........................................................................................................ 7 UndergroundUtilities .................................................................................................................................... 10 Temporary and Permanent Slopes ................................................................................................................ 11 TemporaryShoring ........................................................................................................................................ 12 TemporaryShoring Monitoring ..................................................................................................................... 13 BuildingFoundations ..................................................................................................................................... 14 PermanentFoundation Walls ........................................................................................................................ 15 StormwaterDetention Vault ......................................................................................................................... 16 Stormwater Infiltration Feasibility ................................................................................................................ 16 On -Grade Concrete Slabs .............................................................................................................................. 17 Permanent Drainage Considerations ............................................................................................................ 18 CLOSURE................................................................................................................................................... 18 FIGURES Figure I —Site and Exploration Plan Figure 2 — Lateral Earth Pressures APPENDICES Appendix A — Subsurface Exploration Procedures and Logs Appendix B — Laboratory Testing Procedures and Results GEOTECHNICAL ENGINEERING REPORT PROPOSED EDMONDS APARTMENTS 23326 HIGHWAY 99 EDMONDS, WASHINGTON Project No. 1948.02 November 20, 2018 INTRODUCTION This report documents the surface and subsurface conditions encountered at the site and our geotechnical engineering recommendations for the proposed Edmonds Apartments project. Our geotechnical engineering scope of services for the project included a literature review, site reconnaissance, subsurface exploration, laboratory testing, geotechnical engineering analysis, and preparation of this report. The observations and conclusions summarized herein are based in part upon conditions observed in our subsurface explorations, site observations, and proposed project plans at the time this report was prepared. In the event that site conditions or proposed plans change, it may be necessary to modify the conclusions and recommendations presented in this report. This report is an instrument of service and has been prepared in general accordance with locally accepted geotechnical engineering practice. This report has been prepared for the exclusive use of Goodman Real Estate, and its agents, for specific application to the subject property and stated purpose. PROJECT UNDERSTANDING Based on our review of progress drawings provided by the project architect (Studio Meng Strazzara) and the project civil engineer (Navix Engineering), we understand the project will consist of design and construction of a new multi -story apartment building on a 1.4 acre property located at 23326 Highway 99 in Edmonds, Washington. The lower two levels of the building will be utilized mostly for vehicular parking while the upper levels will contain living space. Finished floor elevations of the lower -most level are currently planned at about 405.5 to 409.75 feet. The building will generally daylight to the east and be buried to the west. Grading for the building is expected to consist mostly of cuts ranging from a minimum of about 1 to 2 feet near the northeast property corner to a maximum estimated depth of about 23 feet along the west property boundary. Stormwater control for the project will occur through an underground detention vault located below the lower parking level in the northeast portion of the building. The bottom elevation of the vault is currently proposed at elevation 402 feet. The project will also include related site improvements including relocation of existing underground utilities, new underground utilities, and frontage improvements along the east side of the site abutting Highway 99. Existing topography and a plan view of the proposed building is shown on the attached Figure 1, Site and Exploration Plan. Page 1 ZipperGeo SURFACE CONDITIONS Proposed Edmonds Apartments Project No. 1948.02 November 20, 2018 The project site consists of a 1.4 acre, roughly trapezoidal -shaped, raw land site located 23326 Highway 99 in Edmonds, Washington. The site is bordered to the north by developed commercial property; to the south by 234 th Street SW; to the east by Highway 99; and to the west by a developed multi -family site. The site is undeveloped with the exception of existing underground utilities including sanitary and storm sewer piping. Topographically, the site generally occurs as an east -facing hillside. The site generally slopes gently to moderately downward to the east. A short (approximately 10 feet tall) steep slope is located along the south half of the west property boundary. This slope descends from about elevation 430 to 420 at an angle of about 23 degrees (43 percent grade). Remaining slopes on the property are generally inclined down to the east at about 10 to 17 percent grade. Total vertical relief from the west to east property boundaries is about 20 feet. Ground cover and vegetation across a majority of the site consists dense deciduous brush and moderately dense deciduous and coniferous trees. No springs or groundwater seepage were observed on the property at the time our subsurface explorations were completed. The site along with the proposed building location are shown on the attached Site and Exploration Plan, Figure 1. SUBSURFACE CONDITIONS Mapped Geology We reviewed published geologic mapping of the site vicinity through the Washington State Department of Natural Resource's web -based mapping application Washington Geologic Information Portal (https://geologyportal.dnr.wa.gov/). The published mapping indicates the site is underlain by Vashon Till. The mapping describes Vashon Till as a nonsorted mixture of clay, silt, sand, pebbles, cobbles, and boulders, all in variable amounts. The mapping further describes the Till as " It typically is hard lodgement till and often is referred to as "hardpan." The "hardpan" is largely a result of compaction caused by the great weight of the overriding ice, hundreds of meters thick." Soil Conservation Service Hydrologic Soil Group Classification We reviewed Soil Conservation Service (SCS) mapping of the site vicinity through USDA NRCS's Web Soil Survey application (https://websoilsurvey.sc.egov.usda.gov/App/WebSoilSurvey.aspx). The mapping indicates the site is underlain by Alderwood-Urban Land Complex soils. Soil Conditions Soil conditions at the site were evaluated through the completion of 5 geotechnical test borings (13-1 to 13- 5). The borings were advanced to a depths ranging from about 21 to 39 feet below existing site grades. The approximate boring locations are shown on the attached Site and Exploration Plan, Figure 1. Soils were visually classified in general accordance with the Unified Soil Classification System. Descriptive logs of the subsurface explorations and the procedures utilized in the subsurface exploration program are presented in Appendix A. A generalized description of soil conditions encountered in the borings is Page 2 ZipperGeo Proposed Edmonds Apartments Project No. 1948.02 November 20, 2018 presented below. Detailed descriptions of soils encountered are provided on the descriptive logs in Appendix A. Surficial soils conditions observed in the borings generally consisted of about 7 to 9 inches of forest cluff and topsoil. Below the forest duff and topsoil, soil conditions observed in borings B-1, B-4, and B-5 generally consisted of about 5 to 7 feet of loose to medium dense, silty sand with variable gravel content interpreted as weathered glacial till. Below the weathered glacial till, these borings encountered dense to very dense, silty sand with variable gravel content interpreted as glacial till to the completion depths of about 21 to 30 feet below existing site grades. Drilling action in these borings indicated localized cobbles and boulders may be present within the very dense glacial till unit. Below the forest duff and topsoil, soil conditions observed in borings B-2 and B-3 generally consisted of about 5 to 12 feet of loose to dense, silty sand with variable gravel content interpreted to be fill soils. Below the fill soils, these borings encountered dense to very dense, silty sand with variable gravel content interpreted to be glacial till to the completion depths of about 31 to 40 feet below existing site grade. Drilling action in these borings indicated localized cobbles and boulders may be present within the very dense glacial till unit. Groundwater Conditions Groundwater seepage was not observed in any of the borings completed as part of our work. Perched groundwater may develop at the contact between the upper medium dense soils and lower dense to very dense soils during the wetter months of the year. Fluctuations in groundwater levels will likely occur due to seasonal variations in the amount of rainfall, runoff and other factors not evident at the time the explorations were performed. Therefore, groundwater levels during construction or at other times in the life of the structure may be higher than indicated on the logs. The possibility of groundwater level fluctuations should be considered when developing the design and construction plans for the project. Summary of Laboratory Testing Laboratory testing was completed on select soil samples obtained from the explorations. Moisture content testing of soil samples obtained within the upper 17 feet of existing site grade ranged from about 5 to 20 percent with an average of about 10 percent. Grain size analysis were completed on select samples obtained from the borings. The grain size analysis indicated fines contents (silt and clay sized soil particles) as follows: Boring Number Sample Number Sample Depth (feet) Fines Content B-2 S-2 5 41% B-2 S-4 15 15% B-3 S-2 5 24% B-4 S-3 10 32% B-5 Composite S-4, S-5, & S-6 12.5 to 17.5 33% Page 3 ZipperGeo CONCLUSIONS AND RECOMMENDATIONS General Proposed Edmonds Apartments Project No. 1948.02 November 20, 2018 Based on our subsurface exploration program and associated research, we conclude that the proposed development is geotechnically feasible, contingent on proper design and construction practices and implementation of the recommendations presented in this report. Our recommendations are presented in the following sections. The recommendations contained in this report are based upon the results of field and laboratory testing (which are presented in Appendices A and B), engineering analyses, and our current understanding of the proposed project. ASTM and Washington State Department of Transportation (WSDOT) specification codes cited herein respectively refer to the current manual published by the American Society for Testing & Materials and the current edition of the WSDOT Standard Specifications for Road, Bridge, and Municipal Construction, (M41-10). Geologically Hazardous Ares As part of our services, we evaluated the presence of regulated geologically hazardous areas (GHAs) at the site. Chapter 23.80 of the Edmonds Municipal Code (the Code) designates GHAs as Erosion Hazard, Landslide Hazard, and Seismic Hazard. The reader is referred to the Code for definitions of GHAs. Based on soil conditions observed in our explorations and site slopes, the site is underlain by Alderwood soils with areas of slopes ranging from 10 to 43 percent grade, and therefore contains Erosion Hazard GHAs. For mitigation of erosion hazards at the site, we recommend the following: • A proper temporary erosion and sediment control plan should be prepared in accordance with local standards by the project civil engineer. • All areas disturbed by construction and not permanently covered with hard surfaces should be adequately stabilized through permanent landscaping. • Design and construct the project in accordance with the recommendations presented in this report. Provided that the above -recommended mitigation measures are implemented, it is our opinion that the potential for erosion and off -site sediment transport will be minimized. Based on soil conditions observed in our explorations and existing site topography, it is our opinion that no areas on the site meet the Code -defined criteria for a Landslide Hazard or Seismic Hazard Area. Seismic Design Considerations The tectonic setting of western Washington is dominated by the Cascadia Subduction Zone formed by the Juan cle Fuca plate subducting beneath the North American Plate. This setting leads to intraplate, crustal, Page 4 ZipperGeo Proposed Edmonds Apartments Project No. 1948.02 November 20, 2018 and interplate earthquake sources. Seismic hazards relate to risks of injury to people and damage to property resulting from these three principle earthquake sources. The seismic performance of the development was evaluated relative to seismic hazards resulting from ground shaking associated with a design seismic event with a 2,475 year return period determined in accordance with the 2015 International Building Code (IBC). Conformance to the above criteria for seismic excitation does not constitute any kind of guarantee or assurance that significant structural damage or ground failure will not occur if a maximum level earthquake occurs. The primary goal of the IBC seismic design procedure is to protect life and not to avoid all damage, since such design may be economically prohibitive. Following a major earthquake, a building may be damaged beyond repair, yet not collapse. IBC Seismic Design Parameters: Based on site location and soil conditions, the values provided below are recommended for seismic design. The values provided below are based on the 2015 IBC as the building code reference document. Description Value 2015 1 BC Site Classification ' C 1 S, Spectra I Acceleration for a Short Period 1.263 g (Site Class B) S, Spectral Acceleration for a 1-Second Period 0.493 g (site Class 13) Sms Maximum considered spectral response 1.263 g (Site Class C) acceleration for a Short Period Sm, Maximum considered spectral response 0.645 g (Site Class C) acceleration for a 1-Second Period SDs Five -percent damped design spectral response 0.852 g (Site Class C) acceleration for a Short Period SD1 Five -percent damped design spectral response 0.430 g (Site Class C) acceleration for a 1-Second Period 1. In general accordance with the 2015 International Building Code, Table 1613.5.2. IBC Site Class is based on the average characteristics of the upper 100 feet of the subsurface profile. 2. The borings completed for this study extended to a maximum depth of 40 feet below grade. ZGA therefore determined the Site Class assuming that similar density soils extend to 100 feet as suggested by published geologic maps for the project area. Ground Surface Rupture: Based on our review of the USGS Quaternary age fault database for Washington State, a strand of the Southern Whidbey island Fault Zone is located approximately 1500 feet northeast of the project site. As the fault does not appear to cross the site, it is our opinion that the risk of ground surface rupture at the site is low. Page 5 ZipperGeo Proposed Edmonds Apartments Project No. 1948.02 November 20, 2018 Landsliding: Based on subsurface soil and groundwater conditions observed in our explorations and the gently to moderately sloping topography of the site and surrounding vicinity, it is our opinion that the risk of earthquake -induced landslicling is low. Soil Liquefaction: Liquefaction is a phenomenon wherein cohesionless soils below the groundwater table build up excess pore water pressures during earthquake loading. Liquefaction typically occurs in loose, cohesionless soils, but may occur in denser soils if the ground shaking is sufficiently strong. The potential hazardous impacts of liquefaction include liquefaction -induced settlement and lateral spreading. Soil conditions observed in our explorations generally consisted of dense to very dense, glacially overridden soils with no groundwater. The glacially overridden soils observed in our explorations are not susceptible to liquefaction. Site Preparation Erosion Control Measures: Stripped surfaces and soil stockpiles are typically a source of runoff sediments. We recommend that silt fences, berms, and/or swales be installed around the clownslope side of stripped areas and stockpiles in order to capture runoff water and sediment. If earthwork occurs during wet weather, we recommend that all stripped surfaces be covered with straw to reduce runoff erosion, whereas soil stockpiles should be protected with anchored plastic sheeting. Temporary Drainage: Stripping, excavation, grading, and subgrade preparation should be performed in a manner and sequence that will provide drainage at all times and provide proper control of erosion. The site should be graded to prevent water from poncling in construction areas and/or flowing into and/or over excavations. Exposed grades should be crowned, sloped, and smooth -drum rolled at the end of each day to facilitate drainage if inclement weather is forecasted. Accumulated water must be removed from subgrades and work areas immediately and prior to performing further work in the area. Equipment access may be limited and the amount of soil rendered unfit for use as structural fill may be greatly increased if drainage efforts are not accomplished in a timely manner. Clearing, Stripping, and Existing Utility Abandonment: Once TESC measures are installed, we expect site preparation to continue with clearing and grubbing brush and trees, stripping of organic rich topsoil, an abandonment of existing underground utilities. We recommend all tree stumps and roots larger than Y2 inch in diameter be cleared and grubbed from the areas planned for improvement. Based on our explorations, stripping depths to remove topsoil is estimated to range from about 7 to 10 inches. Stripping depths maybe greater near trees and brush to fully remove root systems. All clearing and stripping debris should be wasted off site or, if approved, used for topsoil in landscape areas. For utility abandonment, we recommend all existing underground utilities be completely removed and wasted off site. Excavations for utility abandonment should be backfilled with compacted structural fill placed in accordance with this report. Alternatively, existing underground utility piping could be abandoned in -place by fully grouting the conduits. Page 6 ZipperGeo Proposed Edmonds Apartments Project No. 1948.02 November 20, 2018 Subgrade Preparation: Once site preparation is complete, all areas that are at design subgrade elevation or areas that will receive new structural fill should be moisture conditioned to a moisture content within plus or minus two percent of optimum moisture content for compaction. The subgrade should then be compacted to a firm and unyielding condition. The existing site soils consist of silty sand at or somewhat above optimum moisture content for compaction. During wet weather, achieving a moisture content adequate for compaction will be impossible. Therefore, we recommend subgrade preparation and earthwork, in general, be completed during drier periods of the year when the soil moisture content can be controlled by aeration and drying. if earthwork or construction activities take place during extended periods of wet weather, or if the in situ moisture conditions are elevated above the optimum moisture content, the soils will become unstable and not compactable. In the event the exposed subgrade becomes unstable, yielding, or unable to be compacted due to high moisture conditions, we recommend that the materials be removed to a sufficient depth in order to develop stable subgrade soils that can be compacted to the minimum recommended levels. The severity of construction problems will be dependent, in part, on the precautions that are taken by the contractor to protect the subgrade soils. Once compacted, subgrades should be evaluated through density testing and proof rolling with a loaded dump truck or heavy rubber -tired construction equipment weighing at least 20 tons to assess the subgrade adequacy and to detect soft and/or yielding soils. In the event that compaction fails to meet the specified criteria, the upper 12 inches of subgrade should be scarified and moisture conditioned as necessary to obtain at least 95 percent of the maximum laboratory density (per ASTIVI D1557). Those soils which are soft, yielding, or unable to be compacted to the specified criteria should be over -excavated and replaced with suitable material as recommended in the Structural Fill section of this report. As an alternate to subgrade compaction during wet site conditions or wet weather, the upper 12 inches of subgrade should be overexcavated to a firm, non -yielding and undisturbed condition and backfilled with compacted imported structural fill consisting of free -draining Gravel Borrow or crushed rock. Freezing Conditions: If earthwork takes place during freezing conditions, all exposed subgrades should be allowed to thaw and then be compacted prior to placing subsequent lifts of structural fill. Alternatively, the frozen material could be stripped from the subgrade to expose unfrozen soil prior to placing subsequent lifts of fill or foundation components. The frozen soil should not be reused as structural fill until allowed to thaw and adjusted to the proper moisture content, which may not be possible during winter months. Structural Fill Materials and Preparation Structural fill includes any material placed below foundations and pavement sections, within utility trenches, to construct embankments, and behind retaining walls. Prior to the placement of structural fill, all surfaces to receive fill should be prepared as previously recommended in the Site Preparation section of this report. Page 7 I ZipperGeo Proposed Edmonds Apartments Project No. 1948.02 November 20, 2018 Laboratory Testing: Representative samples of on -site and imported soils to be used as structural fill should be submitted for laboratory testing at least 4 days in advance of its intended use in order to complete the necessary Proctor tests. Reuse of Site Soils as Structural Fill: Mass grading for the building is expected to consist mostly of cuts with the excavation spoils hauled off site. However, we expect the reuse of site soils as structural fill will be desirable for underground utilities and for backfill around the proposed stormwater detention vault. The suitability for reuse of site soils as structural fill depends on the composition and moisture content of the soil. Soils encountered in excavations at the site are expected to consist of sands with a significant fines content (15 to over 30 percent). As the amount of fines increases, the soil becomes increasingly sensitive to small changes in moisture content. Soils containing more than about 5 percent fines cannot be consistently compacted to the appropriate levels when the moisture content is more than approximately 2 percent above or below the optimum moisture content (per ASTM D1557). Optimum moisture content is that moisture content which results in the greatest compacted dry density with a specified compactive effort. Laboratory testing of select soil samples indicates the in -place moisture content of site soils ranges from about 5 to 20 percent with an average of about 10 percent. Optimum moisture content of site soils is estimated at about 6 to 10 percent. Therefore, site soils appear at or slightly above optimum moisture content for compaction. Site soils will only be s9itable for reuse as structural fill during dry weather. During wet weather, site soil will quickly become too wet for reuse as structural fill. During wet weather, the project team and bidding contractors should expect that site soils will not be suitable for reuse as structural fill and imported fill with little to no fines content will be required. We recommend that site soils used as structural fill have less than 4 percent organics by weight and have no woody debris greater than Y2 inch in diameter. We recommend that all pieces of organic material greater than Y2 inch in diameter be picked out of the fill before it is compacted. Any organic -rich soil derived from earthwork activities should be utilized in landscape areas or wasted off site. Imported Structural Fill: If backfilling of underground utilities and the stormwater detention vault occurs during wet weather, imported structural fill may be required. The appropriate type of imported structural fill will depend on weather conditions. During extended periods of dry weather, we recommend imported fill, at a minimum, meet the requirements of Common Borrow as specified in Section 9-03.14(3) of the most current version of the Washington State Department of Transportation, Standard Specifications for Road, Bridge, and Municipal Construction (WSDOT Standard Specifications). During wet weather, higher - quality structural fill might be required, as Common Borrow may contain sufficient fines to be moisture sensitive. During wet weather we recommend that imported structural fill meet the requirements of Gravel Borrow as specified in Section 9-03.14(l) of the WSDOT Standard Specifications. Prior to importing Page 8 ZipperGeo Proposed Edmonds Apartments Project No. 1948.02 November 20, 2018 structural fi I I for genera I use in raising site grades, we recommend we be provided a sample of the materia I to evaluate its suitability for use as structural fill. Retaining Wall Backfill: Cast -in -place concrete foundation retaining walls should include a drainage fill zone extending at least 2 feet back from the back face of wall for the entire wall height. The drainage fill should meet the requirements of Gravel Backfill for Walls as specified in Section 9-03.12(2) of the WSDOT Standard Specifications. Compaction Criteria: Our recommendations for soil compaction are summarized in the following table. Structural fill for roadways and utility trenches in municipal rights -of -way should be placed and compacted in accordance with the jurisdiction codes and standards. We recommend that a geotechnical engineer be present during grading so that an adequate number of density tests may be conducted as structural fill placement occurs. In this way, the adequacy of the earthwork may be evaluated as it proceeds. RECOMMENDED SOIL COMPACTION LEVELS Location Minimum Percent Compaction* All fill below building floor slabs and foundations 95 Upper 2 feet of fill below pavements 95 Pavement fill below 2 feet 92 Retaining wall backfill less 3 feet from back of wall face 92** Upper 2 feet of utility trench backfill 95 Utility trenches below 2 feet 92 Landscape Areas 90 * ASTM D1557 Modified Proctor Maximum Dry Density "Core must be taken not to over -compact retaining wall backfill as over -compaction can induce stresses in excess of design stresses. Moisture Content: Structural fill should be placed at a moisture content within plus or minus two percent of optimum moisture content as determined by the ASTM D-1557 test method (modified proctor). Imported structural fill should be delivered to the site at the recommended moisture content for compaction. Structural fill with a moisture content greater than two percent above optimum should be moisture conditioned by windrowing and drying or wasted off site. Structural fill with a moisture content less than two percent below optimum should be blended with water to achieve the recommended moisture content. Fill Placement: Structural fill should be placed in horizontal lifts with a loose lift thickness appropriate for the material and energy of the compaction equipment used. if lift loose lift thickness greater than 12 inches are desired, the contractor should be required to demonstrate that the combination of fill material and compaction equipment can compact the entire lift thickness to the specified levels. Each lift of fill Page 9 Proposed Edmonds Apartments ZipperGeo Project No. 1948.02 November 20, 2018 should be compacted to the minimum levels recommended above based on the maximum laboratory dry density as determined by the ASTM D1557 Modified Proctor Compaction Test. Underground Utilities We recommend that utility trenching conform to all applicable federal, state, and local regulations, such as OSHA and WISHA, for open excavations. Trench excavation safety guidelines are presented in WAC Chapter 296-155 and WISHA RCW Chapter 49.17. Utility Subgrade Preparation: We recommend that all utility subgrades be firm and unyielding and free of all soils that are loose, disturbed, or pumping. Such soils should be removed and replaced, if necessary. All structural fill used to replace over -excavated soils should be compacted as recommended in the Structural Fill section of this report. If utility foundation soils are soft, we recommend that they be over - excavated 12 inches and replaced with crushed rock. Structures such as manholes and catch basins which extend into soft soils should be underlain by at least 12 inches of crushed gravel fill compacted to at least 90 percent of the modified Proctor maximum dry density. This granular material could consist of crushed rock, quarry spalls, or coarse crushed concrete. Alternatively, quarry spalls or pea gravel could be used until above the water level. It may be necessary to place a geotextile fabric over the native subgrade soils if they are too soft, to provide a separation between the bedding and subgrade soils. Bedding: We recommend that a minimum of 4 inches of bedding material be placed above and below all utilities or in general accordance with the utility manufacturer's recommendations and local ordinances. We recommend that pipe bedding consist of Gravel Backfill for Pipe Zone Bedding as specified in Section 9-03.12(3) of the WSDOT Standard Specifications. All trenches should be wide enough to allow for compaction around the haunches of the pipe, or material such as pea gravel should be used below the spring line of the pipes to eliminate the need for mechanical compaction in this portion of the trenches. If water is encountered in the excavations, it should be removed prior to fill placement. Trench Backfill: Materials, placement, and compaction of utility trench backfill should be in accordance with the recommendations presented in the Structural Fill section of this report. In our opinion, the initial lift thickness should not exceed 1 foot unless recommended by the manufacturer to protect utilities from damage by compacting equipment. Light, hand operated compaction equipment may be utilized directly above utilities if damage resulting from heavier compaction equipment is of concern. Underground Utility Construction Sequencing: Based on our review of plans provided by the project civil engineer, new underground utilities are proposed along the outside of the building perimeter on the west side of the site. As discussed subsequently, temporary shoring will likely be required to construct the building. Installation of these utilities may conflict with temporary shoring elements. Additionally, access to the utility alignments could be difficult after temporary shoring is constructed. Construction Page 10 ZipperGecl Proposed Edmonds Apartments Project No. 1948.02 November 20, 2018 sequencing for construction of underground utilities and other aspects of the project should be thoroughly evaluated by the project team to identify and avoid potential conflicts. Temporary and Permanent Slopes Temporary excavation slope stability is a function of many factors, including: 0 The presence and abundance of groundwater; • The type and density of the various soil strata; • The depth of cut; • Surcharge loadings adjacent to the excavation; and • The length of time the excavation remains open. As the cut is deepened, or as the length of time an excavation is open, the likelihood of bank failure increases; therefore, maintenance of safe slopes and worker safety should remain the responsibility of the contractor, who is present at the site, able to observe changes in the soil conditions, and monitor the performance of the excavation. It is exceedingly difficult under the variable circumstances to pre -establish a safe and "maintenance -free" temporary cut slope angle. Therefore, it should be the responsibility of the contractor to maintain safe temporary slope configurations since the contractor is continuously at the job site, able to observe the nature and condition of the cut slopes, and able to monitor the subsurface materials and groundwater conditions encountered. Unsupported vertical slopes or cuts deeper than 4 feet are not recommended if worker access is necessary. The cuts should be adequately sloped, shored, or supported to prevent injury to personnel from local sloughing and spalling. The excavation should conform to applicable Federal, State, and Local regulations. According to Chapter 296-155, Part N of the Washington Administrative Code (WAC), the contractor should make a determination of excavation side slopes based on classification of soils encountered at the time of excavation. For planning purposes, we recommend temporary excavations within the upper 10 feet of existing site grades be planned no steeper than 1.5H:1V (horizontal to vertical). Temporary excavations completed in the very dense glacial till soils observed in our explorations (typically observed below 10 feet from existing site grades) should be planned not steeper than 0.75H:IV. Temporary cuts may need to be constructed at flatter angles based upon the soil moisture and groundwater conditions at the time of construction. Adjustments to the slope angles should be determined by the contractor at that time. Temporary excavations that extend below the groundwater table will not be adequately stable unless clewatered. Groundwater levels should be maintained a minimum of two feet below the bottom of temporary excavations. We recommend that all permanent cut or fill slopes (excluding stormwater ponds) constructed in native soils or with imported structural fill be designed at a 2H:1V (Horizontal:Vertical) inclination or flatter. All Page 11 ZipperGeo Proposed Edmonds Apartments Project No. 1948.02 November 20, 2018 permanent cut and fill slopes should be adequately protected from erosion both temporarily and permanently. We do not expect stormwater ponds for this project. If the slopes are exposed to prolonged rainfall before vegetation becomes established, the surficial soils will be prone to erosion and possible shallow sloughing. We recommend covering permanent slopes with a rolled erosion protection material, such as composite straw or coir matting or Curlex 11, if vegetation has not been established by the regional wet season (typically November through May). Temporary Shoring Based on our analysis, it appears sloped temporary excavations to construct the building along the north, west, and portions of the south property line are not feasible as they would extend beyond the property line. As such, it appears that temporary shoring will be required. In order to determine the limits of required temporary shoring, we recommend the project civil engineer develop a temporary excavation grading plan using the planning criteria for temporary cut slope inclinations provided above in the Temporary and Permanent Slopes section of this report. For the expected shoring heights, we have identified two alternatives for temporary shoring: 1.) anchored and cantilever soldier pile retaining walls or 2.) soil nail retaining walls. Soil nail Unsuppoftil Cul walls are typically more economical as compared to anchored soldier pile retaining walls. Based on subsurface soil and groundwater conditions, it is our opinion soil nailing is feasible for temporary shoring. The process of soil nailing consists of making short (typically 5 feet or less) vertical cuts, installing horizontal elements (soil nails) extending into the cut, and then placing a thin layer (typically 4 inches) of reinforced shotcrete (pneumatically placed concrete) on the soil cut face. Soil nails are typically installed at horizontal and vertical spacings of about 4 to 6 feet on Mat, Step 1. Excav-alh Mal Lift Tendon (Rout S* Drain Stop 3 Instai; and Grout No (Wwkides Smp Drain InsWkWon) 2 Final Gradt- ............ 5100 5. Con6vuetion of Sube"uent LeAft Stop 2. Drill Noll We Initial Facing EIDrain ZIln"11Z. Stop 4. Place Indial Foong Jincludes shakraft. "Awem"ni, BwAng PlAtd. WYM#W and Hex Nut inal8lak1w) Fol ----IlllllllllMft Facing Foal SNO G. Plato Final Facing OneJudge Building of Foot Dnkln) center. The length of soil nails is typically about 0.7 times the wall height and installed at about 15 to 20 degrees from horizontal. The process is repeated until the bottom of the excavation is reached. Soil nail walls are most favorable in soils that show a significant stand up time when cut vertical. However, alternative methods can be utilized Page 12 ZipperGeo Proposed Edmonds Apartments Project No. 1948.02 November 20, 2018 in less -stable soils such as stabilization berms, vertical elements, or shotcrete flash coating. The typical sequence of soil nailing is shown in the figure above. It should be noted that soil nails may extend beyond property lines therefore requiring temporary underground construction easements from adjacent property owners. Additionally, soil nails may conflict with existing or proposed underground utilities. These conflicts should be evaluated by the shoring designer. For design of soil nail shoring walls, we recommend the following design parameters. The shoring designer should refer to the boring logs provided in Appendix A for soil unit depth limits. Soil Unit Moist Soil Soil Friction Angle Soil Cohesion Ultimate Unit Weight (degrees) (psf) Ground/Grout Bond (pcf) (kips/ft)* Fill & Weathered Till 125 34 0 6 Till 135 40 500 10 *Assumes 6-inch minimum drill hole diameter Design of soil nail walls should be completed in accordance with the methodologies presented in the Federal Highway Administration Report Number FHWA-IF-03-017, Geotechnical Engineering Circular No. 7, Soil Nail Walls (allowable stress design). Construction of soil nail walls should be in accordance with Section 6-15 of the 2015 Washington State Department of Transportation Standard Specifications for Road, Bridge and Municipal Construction. We recommend that a minimum of two sacrificial, 200 percent verification tests be performed in each soil type to be nailed in order to evaluate the ultimate soil friction capacity and the load deformation performance of the soil nail. Verification testing should be accomplished as soon as each soil type is encountered and prior to installation of production nails. The location of the verification tests should be selected by the contractor and approved by the engineer of record. The drilling method, hole diameter, and depth of soil nail should be identical to the production soil nails. Additionally, 5 percent of production soil nails should be proof tested to 150 percent of design load to confirm the design capacity and appropriate construction methods. Zipper Geo Associates has extensive design experience with soil nail shoring walls. We are available to provide shoring design upon request. If the project team prefers anchored and cantilever solider pile shoring, we should be consulted to provide additional recommendations. Temporary Shoring Monitoring Any time an excavation is made below the level of existing buildings, utilities, or other structures, there is risk of damage even if a well -designed shoring system has been planned. Therefore, we recommend that Page 13 ZipperGeo Proposed Edmonds Apartments Project No. 1948.02 November 20, 2018 a monitoring program be conducted on adjacent facilities and structures. The monitoring program should include measurements of the horizontal and vertical movements of the adjacent structures and the shoring system itself. At least two reference lines should be established adjacent to the excavation at horizontal distances back from the excavation space of about 1/31-1 and H, where H is the final excavation height. Monitoring of the shoring system should include measurements of horizontal and vertical movements. If local wet areas are noted within the excavation, additional monitoring points may be recommended by ZGA. The measuring system used for shoring monitoring should have an accuracy of at least 0.01 foot. All reference points should be installed and readings taken prior to commencing the excavation. All reference points should be read prior to and during critical stages of construction. The frequency of readings will depend on the results of previous readings and the rate of construction. As a minimum, readings should be taken about once a week throughout construction until the basement walls are completed. All readings should be reviewed by ZGA. In order to limit the potential for construction damage claims on adjacent properties, we recommend the condition of existing off -site improvements be carefully documented. We recommend making a complete inspection and evaluation of pavements, structures, utilities, and other facilities located a maximum distance of two times the maximum shoring retained height. This inspection should focus on detecting any existing signs of existing damage. We recommend the observations be documented by pictures, notes, survey drawings, or other means of verification. If existing cracks are noted, consideration should be given to installing crack monitoring gauges to detect and document slight movements. Pre - construction condition assessments should be conducted in coordination with appropriate contractors, the owner, and shoring designer. Building Foundations Based on our analyses, conventional, shallow spread footings appear feasible for support of building foundation loads provided that the foundation subgrades are prepared in accordance with this report. Recommendations for shallow spread footings are provided below. General Footing Subgrade Preparation Soils encountered at footing subgrade elevation are expected to consist of two distinct conditions. Where footings are located less than about 10 feet below existing site grades (generally in the east half of the building), soil conditions expected at footing subgrade elevations are expected to consist of medium dense to dense, weathered glacial till. Footing subgrade preparation in these areas should consist of compacting the footing subgrade to a firm and unyielding condition. Where footing subgrades are located greater than about 10 feet below existing site grades (generally in the west half of the building), soil conditions expected at footing subgrade elevation are expected to Page 14 ZipperGeo Proposed Edmonds Apartments Project No. 1948.02 November 20, 2018 consist of very dense, glacial till soils. In these areas, we do not expect any special footing subgrade preparation will be required. if wet weather is predicted, prepared footing subgrades should be protected through placement of a thin layer of controlled density fill (CDF). Shallow Foundation Allowable Bearing Pressure For footings founded less than 10 feet below existing site grade, we recommended an allowable bearing pressure of 3,000 psf. For footings founded greater than 10 feet below existing site grade, we recommend an allowable bearing pressure of 7,000 psf. A one-third increase of the bearing pressure recommended above may be used for short-term transient loads such as wind and seismic forces. Shallow Foundation Depth and Width For frost protection, the bottom of all exterior footings should bear at least 18 inches below the lowest adjacent outside grade, whereas the bottoms of interior footings should bear at least 12 inches below the surrounding slab surface level. We recommend that all continuous wall and isolated column footings be at least 12 and 24 inches wide, respectively. Lateral Resistance Resistance to lateral loads can be calculated assuming an ultimate soil passive resistance of 450 pcf equivalent fluid pressure (triangular distribution) and an ultimate base friction coefficient of 0.50. An appropriate safety factor (or load/resistance factors) should be included for calculating resistance to lateral loads. For allowable stress design, we recommend a minimum 1.5 safety factor. We recommend that passive resistance be neglected in the upper 18 inches of embedment. The a bove-reco rn mended soil passive resistance assumes any structural fill used to backfill footing excavations is placed and compacted in accordance with the recommendations presented in this report. Estimated Foundation Settlements Total settlement of footings for service load conditions founded on a subgrade prepared as recommended in this report are estimated to be less than I inch. Differential settlement is estimated to be about Y2 inch or less in 40 feet. The above estimated foundation settlements should be considered preliminary. ZGA should be provided an opportunity to review foundation plans for the building to confirm or revise our estimated foundation settlements. Permanent Foundation Walls Recommended lateral earth pressures for design of permanent foundation walls are provided graphically in the attached Figure 2. Figure 2 provides recommendations for both static and seismic lateral earth pressures assuming an active condition. Lateral earth pressures were estimated in general accordance with generalized limit equilibrium (GLE) methodologies as described in Part 3 of the 2009 NEHRP Recommended Seismic Provisions for New Buildings and Other Structures (2009 NEHRP). Per Section Page 15 Proposed Edmonds Apartments Project No. 1948.02 ZipperGeo November 20, 2018 11.8.3 Commentary of the 2009 NEHRP, 2/3 of the PGAm was used for the design horizontal ground acceleration, kh. From the ASCE 7 seismic design maps web -based application, PGArn was determined to be 0.51g. Therefore a kh value of 0.34g was used. For the seismic component, limits of the seismic active earth pressure wedge were constrained to match that of the static wedge per recommendations presented in Tsai and Newman, 2014 (Wedge Size Issues On Calculating Seismically Induced Lateral Earth Pressure For Retaining Structures — An Overview And A New Simple Approach, Journal of GeoEngineering, Vol. 9, No. 2, pp. 45-53, August 2014). For lateral resistance, parameters provided above in the Building Foundations section of this report may be used. The recommendations for lateral earth pressures presented in Figure 2 for the west building line foundation wall assume that this wall will be cast neat against a temporary shoring wall. If the west building line foundation wall will be backfilled, we should be consulted for revised earth pressures. The earth pressures presented in Figure 2 assume an active earth pressure condition will prevail. If any permanent foundation walls will be braced prior to backfilling, an at -rest earth pressure condition will prevail and we should be consulted for revised earth pressures. Stormwater Detention Vault Current plans indicate an approximate 31,500 cubic foot underground detention vault will be constructed in the northeast portion of the site. The bottom elevation of the vault is currently proposed at elevation 402 feet. For lateral earth pressures, Figure 2 may be used for design of the vault. For bearing pressure and lateral resistance values, information provided above in the Building Foundations section of this report may be used. Footings for the building may impose a surcharge on the vault walls. If possible, we recommend building footings near the vault be planned such that they do not impose a surcharge on the vault walls by locating them in such a manner that a 1H:1V line projected from the bottom edge of a footing does not intersect vault walls. We should be consulted for surcharge recommendations if the footings cannot be located below this 1H:1V plane. Stormwater Infiltration Feasibility Borings B-4 and B-5 were completed in the vicinity of the proposed stormwater vault. At the proposed vault bottom elevation of 402 feet, the borings indicate site soil conditions consist of very dense glacial till (hardpan). Stormwater design in the City of Edmonds is regulated by the DOE's 2014 Stormwater Management Manual for Western Washington (2014 SWMM) and the City of Edmonds June 8, 2017 Stormwater Addendum. Appendix A of the June 2017 Edmonds Stormwater Addendum (ESA) outlines infeasibility criteria for various stormwater management BMPs. For infiltration systems, the ESA requires at least 1 foot of permeable soil from the bottom of the infiltration system to the seasonal high groundwater table or other impermeable layer. The 2014 SWMIVI defines permeable soil as "Soil materials with a sufficiently Page 16 ZipperGeo Proposed Edmonds Apartments Project No. 1948.02 November 20, 2018 rapid infiltration rate so as to greatly reduce or eliminate surface and stormwater runoff. These soils are generally classified as SCS hydrologic soil types A and B." As indicated above, SCS mapping indicates the site is underlain by the Alderwood group of soils. The 2014 SWMM classifies the Alderwood group soils as hydrologic soil group C. The 2014 SWMM defines hydrologic soil group as: "Soils having low infiltration rates when thoroughly wetted and consist chiefly of soils with a layer that impedes downward movement of water and soils with moderately fine to fine textures. These soils have a low rate of water transmission (0.05-0.15 in/hr.)." Additionally, in many areas, the 2014 SWMM generally refers to hardpan or glacial till as an impermeable layer as related to stormwater infiltration. We agree with the DOE's classification of till as an impermeable soil as related to stormwater infiltration. Additionally, the till at this site is extremely dense and contains fines contents generally in excess of 30 percent fines further supporting the generally impermeable nature of the till at this site. As such, it is our opinion that stormwater infiltration at the currently proposed vault location and elevation is infeasible due to the impermeable nature of till soils at this site. Based on proposed site grades and soils encountered in other borings, it is further our opinion that stormwater infiltration at other locations on the site is infeasible. On -Grade Concrete Slabs The following sections provide recommendations for on -grade floor slabs. Subgrade Preparation and Modulus of Subgrade Rea tion Subgrades; for on -grade slabs should be prepared in accordance with the Site Preparation and Structural Fill sections of this report. For slab subgrades prepared in accordance with this report, a modulus of vertical subgrade reaction of 250 pounds per cubic inch (pci) may be used for design. Capillary Break To provide a capillary break, uniform slab bearing surface, and a minimum subgrade modulus of 150 pci, we recommend the on -grade slabs be underlain by a 6-inch thick layer of compacted, granular fill contain less than 5 percent fines, based on that soil fraction passing the U.S. No. 4 sieve. A clean angular gravel such as No. 7 aggregate per WSDOT: 9-03.1(4)C could be used for this purpose. Alternative capillary break materials should be submitted to the geotechnical engineer for review and approval before use. Vapor Retarder The use of a vapor retarder should be considered beneath concrete slabs on grade that will be covered with wood, tile, carpet or other moisture sensitive or impervious coverings, or when the slab will support equipment sensitive to moisture or is otherwise considered moisture -sensitive. When conditions warrant the use of a vapor retarder, the slab designer and contractor should refer to ACI 302 and/or ACI 360 for procedures and cautions regarding the use and placement of a vapor retarder. Page 17 Proposed Edmonds Apartments Project No. 1948.02 ZipperGeo November 20, 2018 Permanent Drainage Considerations Surface Drainage Final site grades should be sloped to carry surface water away from buildings and other drainage -sensitive areas. Additionally, site grades should be designed such that concentrated runoff on softscape surfaces is avoided. Any surface runoff directed towards softscaped slopes should be collected at the top of the slope and routed to the bottom of the slope and discharged in a manner that prevents erosion. Permanent Foundation Wall Drainage While groundwater was not encountered within our borings, surface water and coarse -grained zones within the Glacial Till create the potential for hydrostatic buildup behind the below -grade portions of the structure. Adequate drainage measures must be installed to collect and direct subsurface water away from subgrade walls. All backfilled walls should include a drainage aggregate zone extending a minimum of two feet from the back of wall for the full height of the wall and wide enough at the base of the wall to allow seepage to flow to the footing drain. The drainage aggregate should consist of material meeting the requirements of WSDOT 9-03.12(2), Gravel Backfill for Walls. A minimum 4-inch diameter, perforated PVC drain pipe should be provided at the base of backfilled walls to collect and direct subsurface water to an appropriate discharge point. We recommend placing a non -woven geotextile, such as Mirafi 140N, or equivalent, around the free draining backfill material. For permanent building walls cast directly against temporary soil nail shoring walls, we recommend a minimum 1-foot wide prefabricated drainage matting (such as Miradrain or J-Drain 400) be placed for the full height of the shoring wall between each column of soil nails. The drainage matting could be attached to the soil cut prior to placement of the temporary shotcrete facing. Near the bottom of the wall, centered in each drainage mat, a prefabricated connector (such as Drain Grate) should be connected to the drainage matting. The connector should be fitted with a 3-inch minimum diameter weep hole pipe that will extend through the face of the permanent foundation wall. The weep hole pipe should be connected to a tightline system leading to a suitable discharge. In addition to the a bove-reconn mended drainage measures, additional water proofing measures should be considered between the soil nail wall face and the back of permanent foundation walls such as Volclay panels. The project team should consult a waterproofing expert for additional waterproofing recommendations. CLOSURE The analysis and recommendations presented in this report are based, in part, on the explorations completed for this study. The number, location, and depth of the explorations were completed within the constraints of budget and site access so as to yield the information to formulate our recommendations. Project plans were in the preliminary stage at the time this report was prepared. We therefore recommend Zipper Geo Associates, LLC be provided an opportunity to review the final plans and specifications when they become available in order to assess that the recommendations and design Page 18 ZipperGeo Proposed Edmonds Apartments Project No. 1948.02 November 20, 2018 considerations presented in this report have been properly interpreted and implemented into the project design. The performance of earthwork, structural fill, foundations, and pavements depend greatly on proper site preparation and construction procedures. We recommend that Zipper Geo Associates, LLC be retained to provide geotechnical engineering services during the earthwork -related construction phases of the project. If variations in subsurface conditions are observed at that time, a qualified geotechnical engineer could provide additional geotechnical recommendations to the contractor and design team in a timely manner as the project construction progresses. This report has been prepared for the exclusive use of Goodman Real Estate and their agents, for specific application to the project discussed and has been prepared in accordance with generally accepted geotechnical engineering practices. No warranties, either express or implied, are intended or made. Site safety, excavation support, and clewatering requirements are the responsibility of others. In the event that changes in the nature, design, or location of the project as outlined in this report are planned, the conclusions and recommendations contained in this report shall not be considered valid unless Zipper Geo Associates, LLC reviews the changes and either verifies or modifies the conclusions of this report in writing. Page 19 J x 405.21 77/7777717,77W, 1.9 -3 CB #4 RIM — 427.1 405.30 ,2�0% 12" IE 423.10 (S) j 1�,O�5.38: STORM WA TE`R',DETENTI OJNl'V-AU LT BELOW PARKING 'SLAB' B-5 A PPROX,31'tO'Q CF LI\lE STOR-AGE -TOP 6F LID = 409.75 TOP OF RISER =','--_�408.5 '4,6- w OUTLET IE. 2.5 BOTTOM OF �,AULT ±462.0 BOTTOM Of7_ .. SUMP ±398.5 28 LF 12" SEE SHEET,C5.ib,FOR VAULT DETAILS 95 LF 12 D.I. @ 1.00% SDMI4 #1 �vt 'TYPE'll RIM = 42&76 - 406.'34 NEW 12" IE 422.15 (N) EX. 12" IE 417.57 (W) NEW 12" IE 417.57 (S) FROM )PERTY NOTE 1 00 f: ERTY — 110 TYP V". 5 l: 407.39 9L B-2 B-4 Pa = 10.41-11 (PLF) 20.8H (PSF) Pae = 19.41-1 (PSF) Pae = 4.91-1 (PSF) Pae = 12.2 STATIC ACTIVE EARTH PRESSURE SEISMIC ACTIVE EARTH PRESSURE WEST BUILDING LINE FOUNDATION WALL - LATERAL EARTH PRESSURE DIAGRAMS ASSUMES PERMANENT WALL WILL BE CAST NEAT AGAINST SHORING NOTE: THE EARTH PRESSURES ABOVE ARE FOR PERMANENT FOUNDATION WALLS AND THE PROPOSED STORMWATER VAULT WALLS. THE EARTH PRESSURES DO NOT INCLUDE THE AFFECT OF SURCHARGES. FOR VEHICULAR LIVE LOAD TRAFFIC SURCHARGES, 2 FT OF ADDITIONAL SOIL ABOVE FINISHED GRADE MAY BE ASSUMED. FOR THE SEISMIC CONDITION, LIVE LOAD TRAFFIC SURCHARGES MAY BE IGNORED. THE EARTH PRESSURES ABOVE ASSUME ACTIVE CONDITIONS WILL PREVAIL AND THAT THE WEST BUILDING LINE FOUNDATION WALL WILL BE CAST NEAT AGAINST TEMPORARY SHORING. IF THE WEST WALL WILL BE BACKFILLED OR IF WALLS WILL BE BRACED PRIOR TO BACKFILLING, ZGA SHOULD BE CONSULTED FOR REVISED LATERAL EARTH PRESSURE RECOMMENDATIONS. NO PR -1 APPENDIX A SUBSURFACE EXPLORATION PROCEDURES & LOGS APPENDIX A SUBSURFACE EXPLORATION PROCEDURES AND LOGS Field Exploration Description Our field exploration for this project included 5 test borings completed on 1/16/18. The approximate exploration locations are shown on the Site and Exploration Plan, Figure 1. Exploration locations were determined by measuring off of existing site features shown on a site plan completed by the project civil engineer. The approximate ground surface elevation at the exploration locations was determined by interpolating from topographic information shown on the above -referenced site plan. As such, the exploration locations and elevations should be considered accurate only to the degree implied by the means and methods used to define them. Boring Procedures Our exploratory borings were advanced with a hollow stem auger, using a track -mounted drill rig operated by an independent drilling firm working under subcontract to our firm. An engineer from our firm continuously observed the borings, logged the subsurface conditions encountered, and obtained representative soil samples. All samples were stored in moisture -tight containers and transported to our laboratory for further visual classification and testing. After each boring was completed, the borehole was backfilled with bentonite clay. Throughout the drilling operation, soil samples were obtained at 2.5- to 5-foot depth intervals by means of the Standard Penetration Test (ASTM: D-1586). This testing and sampling procedure consists of driving a standard 2- inch outside diameter steel split spoon sampler 18 inches into the soil with a 140-pound hammer free falling 30 inches. The number of blows required to drive the sampler through each 6-inch interval is recorded, and the total number of blows struck during the final 12 inches is recorded as the Standard Penetration Resistance, or "blow count" (N value). If a total of 50 blows is struck within any 6-inch interval, the driving is stopped and the blow count is recorded as 50 blows for the actual penetration distance, The resulting Standard Penetration Resistance values indicate the relative density of granular soils and the relative consistency of cohesive soils. The enclosed boring logs describe the vertical sequence of soils and materials encountered in each boring, based primarily upon our field classifications and supported by our subsequent laboratory examination and testing. Where a soil contact was observed to be gradational, our logs indicate the average contact depth. Where a soil type changed between sample intervals, we inferred the contact depth. Our logs also graphically indicate the blow count, sample type, sample number, and approximate depth of each soil sample obtained from the boring, as well as any laboratory tests performed on these soil samples. if any groundwater was encountered in a borehole, the approximate groundwater depth, and date of observation, is depicted on the log. Groundwater depth estimates are typically based on the moisture content of soil samples, the wetted portion of the drilling rods, the water level measured in the borehole after the auger has been extracted, or through the use of an observation well. The boring logs presented in this appendix are based upon the drilling action, observation of the samples secured, laboratory test results, and field logs. The various types of soils are indicated as well as the depth where the soils or characteristics of the soils changed. It should be noted that these changes may have been gradual, and if the changes occurred between samples intervals, they were inferred. See Figure 1, Site and Exploration Plan 419' 1/16/2018 SOIL DESCRIPTION Z� :E The stratification lines represent the approximate boundaries between soil types. The transition may be gradual. Refer to report text and appendices for additional information. 0- 7 inches of topsoil over loose, moist, brown, silty SAND, trace — gravel ------------------------------------------- Dense, moist, gray, silty SAND, some gravel (Weathered Till) F------- ----------------------------------- Medium dense, wet, light gray, silty SAND, some to trace 5 gravel (Weathered Till) ------------------------------------------- Very dense, moist, light gray, silty SAND, some to trace gravel (Till) 110 1 151 grades to with silt 120 at 21.0 feet possible cobbles 25 1 SAMPLELEGEND GROUNDWATER LEGEND 2-inch O.D, split spoon sample Clean Sand 3-inch I.D. Shelby tube sample Bentonite Grout/Concrete Pl Screened Casing TESTING KEY � Blank Casing GSA = Grain Size Analysis V Groundwater level at time of drilling (ATD) or 20OW = 200 Wash Analysis on date of Consol. = Consolidation Test measurement. Att. = Atterberg Limits Drilling Company: Holocene Drilling Bore Hole Dia.: 7" Drilling Method: Hollow Stem Auger Hammer Type: Auto Drill Riq� D50 Lqgged by_ TLW PENETRATION RESISTANCE (blows/foot) E L.0 A Standard Penetration Test U C . -i Z a 0 Hammer Weight and Drop: C C E < M co 0 - (D 0 20 40 60 11111 1111 1 NINON 11 1 1" all 1 111111 11111 �-N 13�11 ME 0) 1C 0 % Fines (<0.075 mm) 0 % Water (Moisture) Content Plastic Limit i E) —1 Liquid Limit Natural Water Content Edmonds Apartments 23326 Hwy 99 Edmonds, WA Date: Jan. 2018 Project No.: 1948.01 Zipper Geo Associates BORING B-1 19019 36th Ave. W, Suite E LOG: Lynnwood, WA Page 1 of 2 See Figure 1, Site and Exploration Plan 419' 1/16/2018 SOIL DESCRIPTION i�� :5 The stratification lines represent the approximate boundaries CL between soil types. The transition may be gradual. Refer to report text and appendices for additional information. 25 ' I Very Dense, moist, light gray, SAND, with silt and gravel at 29.0 feet possible cobbles to boulders -30- - Boring completed at approximately 30 feet on 1/16/18. — No groundwater observed ATD. �35 140 [45 50 1 SAMPLELEGEND GROUNDWATER LEGEND 2-inch O.D. split spoon sample Clean Sand 3-inch I.D, Shelby tube sample Bentonite Grout/concrete Screened Casing TESTING KEY Blank Casing GSA = Grain Size Analysis Groundwater level at time of drilling (ATD) or 20OW = 200 Wash Analysis Q on date of Consol. = Consolidation Test measurement. Att� = Atterberg Limits Drilling Company: Holocene Drilling Bore Hole Dia.� 7" Drilling Method: Hollow Stem Auger Hammer Type: Auto B-1 Drill Rig: D50 L2g_qed bL TLW PENETRATION RESISTANCE (blows/foot) 4; U) E LLJ CU C Standard Penetration Test 0) Z -j a > 0 0 Hammer Weight and Drop: E < M U) U) 0 0 0 0 20 40 60 M 2�111111111111111iwimm ----- --- UKIM 0 % Fines (<0.075 mm) 0 % Water (Moisture) Content Plastic Limit I e -� Liquid Limit Natural Water Content Edmonds Apartments 23326 Hwy 99 Edmonds, WA Date: Jan. 2018 Project No.: 1948.01 Zipper Geo Associates BORING B-1 19019 36th Ave. W, Suite E LOG: Lynnwood, WA Page 2 of 2 See Figure 1, Site and Exploration Plan 430' 1/16/2018 SOIL DESCRIPTION The stratification lines represent the approximate boundaries CL (D between soil types. The transition may be gradual. Refer to 0 report text and appendices for additional information. 0 ' 8 inches of topsoil over medium dense, moist, brown, silty SAND, trace gravel (Possible Fill) 5 j ------------------------------------------- Dense, moist, light brown, silty SAND, some gravel (Possible Fill) 1 1 grades to loose and wet from 10.0 feet to 12.0 feet ------------------------------------------- Very dense, moist, light gray, gravelly SAND, with silt (Till) 115 120 25 1 SAMPLELEGEND GROUNDWATER LEGEND 2-inch O.D. split spoon sample clean sand 3-inch I.D. Shelby tube sample Bentonite Grout/Concrete Screened Casing TESTING KEY Blank Casing GSA = Grain Size Analysis V Groundwater level at time of drilling (ATD) or 20OW = 200 Wash Analysis zt Q on date of Consol. = Consolidation Test measurement. Att. = Atterberg Limits Drillinq Company: Holocene Drilling Bore Hole Dia.: 7" Drillinq Method: Hollow Stem Auger Hammer Type: Auto B-2 Drill Rig: D50 Lqqged by_ TLW PENETRATION RESISTANCE (blows/foot) E LLi i�' U) C A Standard Penetration Test _j Z 8 0 Hammer Weight and Drop: E 0 C/) 0 Fn 0 0 20 40 60 ------------ 0 %Fines (<0.075 mm) 0 % Water (Moisture) Content Plastic Limit i E) --I Liquid Limit Natural Water Content Edmonds Apartments 23326 Hwy 99 Edmonds, WA Date: Jan. 2018 Project No.: 1948.01 Zipper Geo Associates BORING B-2 19019 36th Ave. W, Suite E LOG: Lynnwood, WA Page 1 of 2 Borinq Location: See Figure 1, Site and Exploration Plan Drilling CompaM. Holocene Drilling Bore Hole Dia.: 7" Top Elevation: 430' Drilling Method: Hollow Stem Auger Hammer Type: Auto Date Drilled: 1/16/2018 Drill Rig: D50 Lqgged by TLW SOIL DESCRIPTION - PENETRATION RESISTANCE (blows/foot) Z5 U) E W n Q Standard Penetration Test :E The stratification lines represent the approximate boundaries -j Z 0 > 0 c Hammer Weight and Drop: C (D between soil types. The transition may be gradual. Refer to E < report text and appendices for additional information. M U) 2 c (D 6 20 40 60 25. Very dense, moist, light gray, silty SAND, trace to some gravel (Till) grades to with gravel S-6 = 2" % — r 1 1 S-7 1 12" 135� 1 S-8 1 4" at 39.0 feet possible cobbles to boulders .40. S-9 X 4" - Boring completed at approximately 40 feet on 1/16/18. — No groundwater observed ATD. 145 50 1 SAMPLELEGEND GROUNDWATER LEGEND 2-inch O.D. split spoon sample Clean Sand 3-inch I.D. Shelby tube sample Bentonite Grout/Concrete Screened Casing TESTING KEY F-1 Blank Casing GSA = Grain Size Analysis Groundwater level at time of drilling (ATD) or 20OW = 200 Wash Analysis on date of Consol. = Consolidation Test measurement. Att. = Atterberg Limits 50/6 5014 50/4 0 %Fines (<0.075 mm) 0 % Water (Moisture) Content Plastic Limit i E) -1 Liquid Limit Natural Water Content Edmonds Apartments 23326 Hwy 99 Edmonds, WA Date: Jan. 2018 Project No.: 1948.01 Zipper Geo Associates BORING B-2 19019 36th Ave. W, Suite E LOG: Lynnwood, WA — Page 2 of 2 See Figure 1, Site and Exploration Plan 427' 1/16/2018 SOIL DESCRIPTION :5 The stratification lines represent the approximate boundaries between soil types. The transition may be gradual. Refer to report text and appendices for additional information. 7 inches of topsoil over loose, moist, gray -brown, silty SAND, trace gravel (Possible Fill) 5 j ------------- ----------------------------- Dense, moist, gray, SAND, with gravel and silt (Weathered Till) ------------------------------------------- Very dense, moist, light gray, silty SAND, some gravel (Till) 110 115 Pgrades to with silt at 21.0 feet possible cobbles to boulders 25 1 SAMPLIELEGEND GROUNDWATER LEGEND 2-inch 0. D. split spoon sample Clean Sand 3-inch I.D. Shelby tube sample Bentonite Grout/concrete Screened Casing TESTING KEY Lj Blank Casing GSA = Grain Size Analysis V Groundwater level at — time of drilling (ATD) or 20OW = 200 Wash Analysis zt Q on date of Consol. = Consolidation Test measurement. Att. = Atterberg Limits Drilling Company: Holocene Drilling Bore Hole Dia.: 7" Drilling Method: Hollow Stem Auger Hammer Type: Auto B-3 Drill Rio: D50 Lqgged by_ TLW PENETRATION RESISTANCE (blows/foot) Z5 C/) M W E CU A Standard Penetration Test ?: , _1 Z > 8 0 'a Hammer Weight and Drop: E < M co En 0 .2 - M (D 0 20 40 60 S-1 0.7 I IN S-2 1.5 I III 1 111111111 111111 HE 11 0 %Fines (<0.075 mm) 0 % Water (Moisture) Content Plastic Limit i E) —] Liquid Limit Natural Water Content Edmonds Apartments 23326 Hwy 99 Edmonds, WA Date: Jan. 2018 Project No.: 1948.01 Zipper Geo Associates BORING B-3 19019 36th Ave. W, Suite E LOG: Lynnwood, WA Page 1 of 2 See Figure 1, Site and Exploration Plan 427' 1/16/2018 SOIL DESCRIPTION :E The stratification lines represent the approximate boundaries CL between soil types. The transition may be gradual. Refer to report text and appendices for additional information. 25 Very Dense, moist, light gray, silty SAND, some gravel (Till) 130 Boring completed at approximately 31 feet on 1/16/18. No groundwater observed ATD. 135 W 50 1 SAMPLELEGEND GROUNDWATER LEGEND 2-inch O.D. split spoon sample Clean Sand 3-inch I.D. Shelby tube sample Bentonite Grout/Concrete Screened Casing TESTING KEY Blank Casing GSA = Grain Size Analysis V Groundwater level at — time of drilling (ATD) or 20OW = 200 Wash Analysis ct t�? on date of Consol. = Consolidation Test i�5 measurement. Att� = Atterberg Limits Drilling Company: Holocene Drilling Bore Hole Dia.: 7" Drilling Method: Hollow Stem Auger Hammer Type: Auto B-3 Drill Rig: D50 LMged_by_ TLW PENETRATION RESISTANCE (blows/foot) E LLJ co C Standard Penetration Test n 0) D --1 Z Q 0 Hammer Weight and Drop: E :C a) M 0 0 2 (D 0 20 40 60 Fn 0 %Fines (<0,075 mm) 0 % Water (Moisture) Content Plastic Limit i E) —� Liquid Limit Natural Water Content Edmonds Apartments 23326 Hwy 99 Edmonds, WA Date: Jan. 2018 Project No,: 1948.01 Zipper Geo Associates BORING B-3 19019 36th Ave. W, Suite E LOG: Lynnwood, WA Page 2 of 2 Boring Location: See Figure 1, Site and Exploration Plan Drilling Company: Holocene Drilling Bore Hole Dia.: 7" Top Elevation: 413' Drilling Method: Hollow Stem Auger Hammer Type: Auto B-4 Date Drilled: 1/16/2018 Drill Riq� D50 LqgqLd by_ TLW SOIL DESCRIPTION PENETRATION RESISTANCE (blows/foot) �5 U) n uu E U) A Standard Penetration Test The stratification lines represent the approximate boundaries _1 Z 0 a) - 0 0 Hammer Weight and Drop: C) C a) between soil types. The transition may be gradual. Refer to -a 2 a') E < W 3: repoil text and appendices for additional information. M 0 0 0 Fn 0 0 20 40 60 0 7 inches of topsoil over medium dense, moist, light brown to brown, silty SAND, trace gravel (Weathered Till) - --------------------------------------------- S-1 7" -5- Medium dense, moist, light gray -brown, silty SAND (Weathered Till) S-2 181, ------------------------------------------- Very dense, moist, light gray, silty SAND, with gravel (Till) S-3 1 18.1 Pgrades to with silt I S-4 1 181, .20. grades to ilty S-5 1 91, Boring completed at approximately 21 feet on 1/16/18. No groundwater observed ATD. 25 1 SAMPLELEGEND GROUNDWATER LEGEND 2-inch O.D. split spoon sample '-f-I clean sand 3-inch I.D. Shelby tube sample Bentonite Grout/Concrete Screened Casing TESTING KEY Blank Casing GSA = Grain Size Analysis V Groundwater level at time of drilling (ATD) or 20OW = 200 Wash Analysis on date of Consol. = Consolidation Test measurement. Att. = Atterberg Limits 17 23 56 74 50/3 0 % Fines (<0.075 mm) 0 % Water (Moisture) Content Plastic Limit i e —1 Liquid Limit Natural Water Content Edmonds Apartments 23326 Hwy 99 Edmonds, WA Date: Jan. 2018 Project No.: 1948.01 Zipper Geo Associates BORING B-4 19019 36th Ave. W, Suite E LOG: Lynnwood, WA Page 1 of 1 Boring Location: See Figure 1, Site and Exploration Plan Drilling Company� Holocene Drilling Bore Hole Dia.: 7" Top Elevation: 412' Drilling Method: Hollow Stem Auger Hammer Type: Auto B-5 Date Drilled: 1/16/2018 Drill Rig: D50 Lgqged by. TLW SOIL DESCRIPTION PENETRATION RESISTANCE (blows/foot) �5 U) � w E C Standard Penetration Test :E CL The stratification lines represent the approximate boundaries _.j Z a- 0 8 0 Hammer Weight and Drop: U a) between soil types. The transition may be gradual. Refer to 2 a W F= < af :3 a) report text and appendices for additional information. 0 - 0 — 0 0 20 40 60 9" of topsoil over dense, light gray -brown, silty SAND, trace gravel (Weathered Till) S-1 181, -5 ---------------------------------------------- Dense, wet, light gray, silty SAND, trace gravel (Till) S-2 at 6.0 feet possible cobbles grades to very dense and moist .10- grades to with gravel S-3 18" SA T [15 ] I S-5 1 8" grades to some gravel I S-6 :[ T .20- S-7 8" at 21.0 feet possible cobbles to boulders S-8 7" 25 1 SAMPLELEGEND GROUNDWATER LEGEND 2-inch 0. D. split spoon sample Clean Sand 3-inch I.D. Shelby tube sample Bentonite Grout/concrete Screened Casing TESTING KEY F-1 Blank Casing GSA = Grain Size Analysis V Groundwater level at time of drilling (ATD) or 20OW = 200 Wash Analysis Q on date of Consol. = Consolidation Test Z measurement. Att. = Atterberg Limits 45 35 5014 5016 5014 50/4 50/6 50/4 0 % Fines (<0.075 mm) 0 % Water (Moisture) Content Plastic Limit ! 8 —� Liquid Limit Natural Water Content Edmonds Apartments 23326 Hwy 99 Edmonds, WA Date: Jan. 2018 Project No.: 1948.01 Zipper Geo, Associates BORING B-5 19019 36th Ave. W, Suite E LOG: Lynnwood, WA — Page 1 of See Figure 1, Site and Exploration Plan 412' 1/16/2018 SOIL DESCRIPTION :F The stratification lines represent the approximate boundaries CL a) between soil types. The transition may be gradual. Refer to 0 report text and appendices for additional information. 25 ' I very dense, moist, light gray, silty SAND, some gravel hgra es to with silt 30 Boring completed at approximately 30 feet on 1/16/18. 135 140 145 50 1 SAMPLELEGEND GROUNDWATER LEGEND 2-inch 0. D. split spoon sample clean sand 3-inch I.D. Shelby tube sample Bentonite Grout/Concrete Screened Casing TESTING KEY F Blank Casing GSA = Grain Size Analysis V Groundwater level at time of drilling (ATD) or 20OW = 200 Wash Analysis on date of Consol. = Consolidation Test measurement. Att. = Atterberg Limits Drilling Company: Holocene Drilling Bore Hole Dia.: 7" Drilling Method: Hollow Stem Auger Hammer Type: Auto B-5 Drill Rig: D50 Lqgged bL TLW PENETRATION RESISTANCE (blows/foot) U) E LU 2" (n Standard Penetration Test Z 0 0 Hammer Weight and Drop: E < 0 0 co 0 0 20 40 60 --- 111-0—Mill --- 1111-01111111�11 ---- 0 %Fines (<0.075 mm) 0 % Water (Moisture) Content Plastic Limit i E) —j Liquid Limit Natural Water Content Edmonds Apartments 23326 Hwy 99 Edmonds, WA Date: Jan. 2018 Project No.: 1948.01 Zipper Geo Associates BORING B-5 19019 36th Ave. W, Suite E LOG: Lynnwood, WA Page 2 of 2 APPENDIX B LABORATORY TESTING PROCEDURES & RESULTS APPENDIX B LABORATORY TESTING PROCEDURES AND RESULTS A series of laboratory tests were performed by ZGA and a subcontract testing laboratory during the course of this study to evaluate the index and geotechnical engineering properties of the subsurface soils. Descriptions of the types of tests performed are given below. Visual Classification Samples recovered from the exploration locations were visually classified in the field during the exploration program. Representative portions of the samples were carefully packaged in moisture tight containers and transported to our laboratory where the field classifications were verified or modified as required. Visual classification was generally done in accordance with ASTM D2488. Visual soil classification includes evaluation of color, relative moisture content, soil type based upon grain size, and accessory soil types included in the sample. Soil classifications are presented on the exploration logs in Appendix A. Moisture Content Determinations Moisture content determinations were performed on representative samples obtained from the explorations in order to aid in identification and correlation of soil types. The determinations were made in general accordance with the test procedures described in ASTM D 2216. Moisture contents are presented on the exploration logs in Appendix A. Grain Size Analysis A grain size analysis indicates the range in diameter of soil particles included in a particular sample. Grain size analyses were performed on representative samples in general accordance with ASTM: D-2487. The results of the grain size determinations for the samples were used in classification of the soils, and are presented in this appendix. GRAIN SIZE ANALYSIS Test Results Summary ASTM D 422 100 Ef 80 70 ca W 60 LU z 50 z w 40 LU 0. 30 20 10 0 1000.000 100.000 10.000 1.000 0.100 0,010 0.001 PARTICLE SIZE IN MILLIMETERS -a'se LGRAVEL Fine Coarse I Medium Fine it Clay BOULDERS COBBLES SAND FINE GRAINED Comments: Exploratio Sample Depth (feet) Moisture Fines (%) Description B-2 S2 5 ft. 7.7 41.2 Silty SAND, some gravel Project No.: 1948.01 PROJECT NAME: Zipper Geo Associates, LLC Geotechnical and Environmental Consultants DATEOFTESTING: 1/19/2018 Edmonds Apartments GRAIN SIZE ANALYSIS Test Results Summary ASTM D 422 100 9XI t— 80 X 0 W 70 00 W 60 W z 50 z W U W 40 W (L 30 20 10 0 1000.000 100.000 10.000 1.000 0.100 0.010 0.001 PARTICLE SIZE IN MILLIMETERS BOULDERS COBBLES Coarse Fi..__ --,-a I Medium Fine Silt Clay GRAVEL SAND FINE GRAINED Comments: Explorati Sample Depth (feet) Moisture (%) Fines (%) Description B-2 S4 t 15 ft. 5.2 14.5 Gravelly SAND, with silt Project No.: 1948.01 PROJECT NAME: Zipper Geo Associates, LLC Geotechnical and Environmental Consultants DATECIFTESTING: 1/19/2018 Edmonds Apartments GRAIN SIZE ANALYSIS Test Results Summary ASTM D 422 100 100111 80 W 70 M W 60 W z LL 50 z LU 0 X 40 LU 0. 30 20 10 0 1000.000 100.000 10.000 1.000 0.100 0.010 0.001 PARTICLE SIZE IN MILLIMETERS ..'se Fine Coarse I Medium Fine Silt Clay BOULDERS COBBLES LGRAVEL SAND FINE GRAINED Comments: Exploratio Sample Depth (feet) Moisture(%) Fines (%) D scription B-3 S2 5 ft. 7.7 24.0 Silty SAND, with gravel Project No.: 1948.01 PROJECT NAME: Zipper Geo Associates, LLC Geotechnical and Environmental Consultants DATEOFTESTING: 1/19/2018 Edmonds Apartments GRAIN SIZE ANALYSIS Test Results Summary ASTM D 422 100 M 1-- 80 X 0 W ;t 70 M W 60 W z 50 z LU 40 W a. 30 20 10 0 1000.000 I off a IIIIIIIII a a a .. I PARTICLE SIZE IN MILLIMETERS Coarse I Fine oa'se I Medium Fine Silt Clay BOULDERS COBBLES GRAVEL :::: LSAND FINE GRAINED Comments: Explorati Sample Depth (feet) Moisture (%) Fines (%) Description B-4 S3 loft. 7.9 31.7 Silty SAND, with gravel Project No.: 1948.01 PROJECT NAME: Zipper Geo Associates, LLC Geotechnical and Environmental Consultants DATEOFTESTING: 1/19/2018 Edmonds Apartments GRAIN SIZE ANALYSIS Test Results Summary ASTM D 422 100 ce 80 70 ca W 60 W z 50 z W 0 W 40 W (L 30 20 10 0 1000.000 1 111111111 a . . V.� PARTICLE SIZE IN MILLIMETERS BOULDERS COBBLES Fine aNs. Medium Fine Silt Clay L.Rarse AVEL G :::E SA D FINE GRAINED Comments: Exploration Sample Depth (feet) Moisture Fines (%) Description B-5 t S4-S6 12.5 to 17.5 ft. 6.6 33.4 Silty SAND, with gravel Project No.: 1948.01 PROJECT NAME: Zipper Geo Associates, LLC Geotechnical and Environmental Consultants DATEOFTESTING: 1/19/2018 Edmonds Apartments STORMWATER SITE PLAN APPENDIX E SOURCE CONTROL GUIDE SHEETS NAVIX Highway 99 Edmonds — Edmonds, WA Page 67 S402 BMPs for Commercial Animal Handling Areas Description of Pollutant Sources: Animals at racetracks, kennels, fenced pens, veterinarians, and businesses that provide boarding services for horses, dogs, cats, etc., can generate pollutants from the following activities: manure deposits, animal washing, grazing, and any other animal handling activity that could contaminate stormwater. Pollutants can include coliform bacteria, nutrients, and total suspended solids. Individual Stormwater Permits covering commercial animal handling facilities include additional applicable source controls. Pollutant Control Approach: To prevent, to the maximum extent practicable, the discharge of contaminated stormwater from animal handling and keeping areas. Applicable Operational BMPs • Regularly sweep and clean animal keeping areas to collect and properly dispose of droppings, uneaten food, and other potential stormwater contaminants. • Do not hose down areas that contain potential stormwater contaminants where they drain to storm drains or to receiving waters. • Do not discharge any washwater to storm drains or to receiving waters without proper treatment. • If the operator keeps animals in unpaved and uncovered areas, the ground must have either vegetative cover or some other type of ground cover such as mulch. • Surround the area where animals are kept with a fence or other means to prevent animals from moving away from the controlled area where BMPs are used. S403 BMPs for Commercial Composting Description of Pollutant Sources: Commercial composting facilities, operating outside without cover, require large areas to decompose wastes and other feedstocks. Design these facilities to separate stormwater from leachate (i.e., industrial wastewater) to the greatest extent possible. When stormwater contacts any active composting areas, including waste receiving and processing areas, it becomes leachate. Pollutants in leachate include nutrients, biochemical oxygen demand (BOD), organics, coliform bacteria, acidic pH, color, and suspended solids. Stormwater at composting facilities include runoff from areas not associated with active processing and curing, such as product storage areas, vehicle maintenance areas, and access roads. Volume IV - Source Control BMPs — December 2014 2-10 �1 Applicable Operational BMPs: • Eliminate unpermitted wastewater discharges to storm sewer, ground water, or surface water. • Convey unpermitted discharges to a sanitary sewer if allowed by the local sewer authority, or to other approved treatment. • Obtain appropriate state and local permits for these discharges. Recommended Additional Operational BMPs: At commercial and industrial facilities, conduct a survey of wastewater discharge coni-lections to storm drains and to surface water as follows: 0 Conduct a field survey of buildings, particularly older buildings, and other industrial areas to locate storm drains from buildings and paved surfaces. Note where these join the public storm drain(s). During non-stormwater conditions inspect each storm drain for non- stormwater discharges. Record the locations of all non-stormwater discharges. Include all permitted discharges. If useful, prepare a map of each area. Show on the map the known location of storm sewers, sanitary sewers, and permitted and unpermitted discharges. Aerial photos may be useful. Check records such as piping schematics to identify known side sewer connections and show these on the map. Consider using smoke, dye, or chemical analysis tests to detect connections between two conveyance systems (e.g., process water and stormwater). If desirable, conduct TV inspections of the storm drains and record the footage on videotape. Compare the observed locations of connections with the information on the map and revise the map accordingly. Note suspect connections that are inconsistent with the field survey. Identify all connections to storm sewers or to surface water and take the actions specified above as applicable BMPs. S411 BMPs for Landscaping and Lawn/ Vegetation Management Description of Pollutant Sources: Landscaping can include grading, soil transfer, vegetation removal, pesticide and fertilizer applications, and watering. Stormwater contaminants include toxic organic compounds, heavy metals, oils, total suspended solids, coliform bacteria, fertilizers, and pesticides. Lawn and vegetation management can include control of objectionable weeds, insects, mold, bacteria, and other pests with pesticides. Examples include weed control on golf course lawns, access roads, and utility corridors and during landscaping; sap stain and insect control on lumber and logs; rooftop moss removal; killing nuisance rodents; fungicide application to patio decks, and residential lawn/plant care. It is possible to Volutne IV - Source Control BMPs — Deceniber 2014 2-21 release toxic pesticides such as pentachlorophenol, carbarnates, and organometallics to the environment by leaching and dripping from treated parts, container leaks, product misuse, and outside storage of pesticide contaminated materials and equipment. Poor management of the vegetation and poor application of pesticides or fertilizers can cause appreciable stormwater contamination. Pollutant Control Approach: Control of fertilizer and pesticide applications, soil erosion, and site debris to prevent contamination of stormwater. Develop and implement an Integrated Pest Management Plan (IPM) and use pesticides only as a last resort. Carefully apply pesticides/ herbicides, in accordance with label instructions. Maintain appropriate vegetation, with proper fertilizer application where practicable, to control erosion and the discharge of stormwater pollutants. Where practicable grow plant species appropriate for the site, or adjust the soil properties of the subject site to grow desired plant species. Applicable Operational BMPs for Landscaping: • Install engineered soil/landscape systems to improve the infiltration and regulation of stormwater in landscaped areas. • Do not dispose of collected vegetation into waterways or storm sewer systems. Recommended Additional Operational BN[Ps for Landscaping: • Conduct mulch -mowing whenever practicable • Dispose of grass clippings, leaves, sticks, or other collected vegetation, by composting, if feasible. • Use mulch or other erosion control measures on soils exposed for more than one week during the dry season or two days during the rainy season. • Store and maintain appropriate oil and chemical spill cleanup materials in readily accessible locations when using oil or other chemicals. Ensure that employees are familiar with proper spill cleanup procedures. • Till fertilizers into the soil rather than dumping or broadcasting onto the surface. Determine the proper fertilizer application rate for the types of soil and vegetation encountered. • Till a topsoil mix or composted organic material into the soil to create a well -mixed transition layer that encourages deeper root systems and drought -resistant plants. • Use manual and/or mechanical methods of vegetation removal rather than applying herbicides, where practical. Volume IV - Source Control BMPs -- December 2014 2-22 STORM WATER SITE PLAN APPENDIX F STORIVIFILTER DESIGN DETAILS NAVIX Highway 99 Edmonds — Edmonds, WA Page 68 "0 OUTLET SUMP A o -��lv - INLET OUTLET TOP SLAB ACCESS SEE FRAME AND—/ 04'-0" [01219 mml I.D. GRATE DETAIL MANHOLESTRUCTURE (04'-10" [01473 mm]) O.D. PLAN VIEW STANDARD OUTLET RISER FLOWKIT: 40A CONTRACTOR TO GROUT TO FINISHED GRADE GRADE RING/RISERS 4 �d FLOATABLES BAFFLE —j X (L uj E LLI E 0 > (n cli INLET PIPE Li co D 0 [L I /I I o F V —,o 4 L STORMFILTER _y/ CARTRIDGE! 7 \— OUTLET HDPE OUTLET RISER FLOW KIT OUTLET SUMP SECTION A -A C The Stormwater Manageime �t3 StormFiltere I IS PRODUCT MAY BE PROTECTED BY ONE OR MORE OF THE FOLLOWING U.S. PATENTS: 5,32.2,629; 5,524,576; 5,707,527; 5,985,157; 6,027,639: 6.649,048; RELATED FOREIGN PATENTS , OR OTHER PATENTS PENDING.