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11-0355 Sound Women's Care.pdf Edmonds Woodway High School Edmonds School District th 23200 100Avenue West Edmonds, WA 98020 Stormwater Site Plan February 16, 2018 The information contained in this report was prepared by and under the direct supervision of the undersigned: Prepared for: LPD Engineering, PLLC DA Hogan & Associates stst 1932 1 Ave, Suite 201 119 1 Ave, Suite 110 Seattle, WA 98101 Seattle, WA 98104 Contact: Jennifer Argraves, P.E. Contact: Bob Harding (206) 725-1211 (206) 285-0400 E DMONDS W OODWAY H IGH S CHOOL S YNTHETIC T URF C ONVERSION P ROJECT S TORMWATER S ITE P LAN T ABLE OF C ONTENTS Section 1 – Project Overview ................................................................................................................................................ 1 Section 2 – Existing Conditions Summary .......................................................................................................................... 1 Section 3 – Offsite Analysis .................................................................................................................................................... 2 Section 4 – Minimum Requirements .................................................................................................................................... 4 Section 5 – Permanent Stormwater Control Plan ............................................................................................................ 7 Pre-developed Site Hydrology........................................................................................................................................... 8 Proposed Site Hydrology .................................................................................................................................................... 9 On-Site Stormwater Management (MR #5) ................................................................................................................. 10 Water Quality (MR #6)..................................................................................................................................................... 12 Flow Control System (MR #7) ........................................................................................................................................ 12 Field Detention System ..................................................................................................................................................... 12 StormTech Detention System (Tennis Court Basin) ................................................................................................ 14 Conveyance System Analysis and Design ..................................................................................................................... 16 Section 6 – Construction Stormwater Pollution Prevention Plan (SWPPP)............................................................ 17 Section 7 – Other Reports and Studies ............................................................................................................................. 17 Section 8 – Other Permits .................................................................................................................................................... 18 Section 9 – Operation and Maintenance Manual ............................................................................................................ 18 Section 10 – Bond Quantities Worksheet ....................................................................................................................... 18 F IGURES Figure 1: Vicinity Map Figure 2: Soils Map Figure 3: Downstream Drainage Map Figure 4: Proposed Conditions Target Surfaces Figure 5: Proposed Conditions Modeled Areas A PPENDICES Appendix A – Design Drawings Appendix B – Design Calculations and Supporting Information Appendix C – Construction Stormwater Pollution Prevention Plan (SWPPP) Narrative Appendix D – Operations and Maintenance Guidelines Appendix E – Draft Declaration of Covenant E DMONDS W OODWAY H IGH S CHOOL S YNTHETIC T URF C ONVERSION P ROJECT S TORMWATER S ITE P LAN F EBRUARY 16, 2018 S ECTION 1 – P ROJECT O VERVIEW This StormwaterSitePlan is for the Edmonds-Woodway Synthetic Tuff Conversion Project th located at the Edmonds-Woodway High School Campus. The site is located at 7600 212St SWin Edmonds, Washington;Section 30, Township 27 North, Range 4East, Willamette Meridian. Refer to Figure 1 –Vicinity Map for sitelocation.Thisproject will involve the conversion of the existing natural grass baseball field to synthetic turf baseball field, which will also serve as a multi- purpose field for football and soccer. A portion of two tennis courts directly north and one tennis court east of the existing baseball field will be demolished to accommodate the improvements. Four new tennis courts will be installed just south of the existing pair of courts northeast of the baseball field. Additionally, there will be pervious pavementwalkways, concrete driveway and pads, lighting improvements, and roofed batting cages southeast of the project area. Track facilities such as a javelin and discus area will be established northwest of the proposed baseball field conversion. Within the project area there are no existing unmanaged hard surfaces that will remain after project completion. This Stormwater Site Plan addresses the requirements of the 2017Edmonds Stormwater Addendum(ESA) and Chapter 18.30 of the Edmonds Municipal Code. The 2017ESA supplements the Department of Ecology (DOE) 2012 Stormwater Management Manual for Western Washington (SMMWW), amended in 2014. S ECTION 2 – E XISTING C ONDITIONS S UMMARY The schoolpropertyis located on one parcel (#27043000104800), with an area of approximately 30.0acres. The EdmondsWoodway High School campus currentlyconsists of school buildings encompassing the northeast portion of the site with the parking lots to the west and south. An existing softball field is in the northwest corner of the parcel with the track/football field south of this field. Theschoolproperty isbounded by 216thStreet SW to the south, 76thAvenue W to the east, 212thStreet SW to the north, and residential complexes to the west.The total project disturbance areais approximately221,854square feet (5.093acres). In the southwest portion of the school is the project area, consisting of an existing baseball field with compacted dirt infield and natural grass outfield.Fourtennis courts are located north of the baseball field, with the two in the northwest corner to remain. A portionof the tennis courts directly north of the field will be demolished, along with the single tennis court directly east of the field. The paved walkways along the north edges of the baseball field that extends to the east as access to the parking lotwill be demolished. The existing topography of the baseball field slopes towards the south at a slope of around 2-4%. There is a slope along the western boundary of the existing baseball field, rising 8 feet to the adjacent field. To the west of the third base line, there is a rockery and steeper grade rise to the track area above. Walkways and existing tennis court to northwest are relatively flat. According to City of Edmonds mapping, the school site is within the Hall Creek Drainage Basin. There are two stormwater discharges from the project area that are tributary to the 12-inch storm th main in 216 Street SW. The system continues east, outfalling into Hall Creek approximately ½- mile downstream of the site. See the Offsite Analysis section of the report for more information on the downstream drainage course. Based upon the Natural Resources Conservation Service Web Soil Survey,the project area is underlain with Alderwood-Urban land complex, 2%-8% slopes.A geotechnical report was preparedby Associated Earth Sciences Inc., dated May 9, 2017.Their subsurface exploration observed existing fill up to 14 feet thick with underlying Vashon Lodgement Till, consisting of dense to very dense sand with silt and gravel. Refer toFigure 2–Soils Map. S ECTION 3 – O FFSITE A NALYSIS The following is a qualitative downstream analysis, performed in accordance with the 2017 City of Edmonds Stormwater Addendum. A site visit was conducted by LPD Engineering on January 17, 2018in orderto investigate the on-site drainage systems, determine the downstream drainage paths and evaluate upstreamtributary areas to the project area. The weatherconditionsduring the site investigationwere characterized byheavy rainfall and moderately strong winds, both of which remained consistent throughout the full duration of conducting the analysis. Furthermore, the temperature was approximately 50 degrees. The site areaof this project is comprisedof the existing baseball field, which islocatedin the southernportion of the school property, and five tennis courts located to the north, northeast, and east of the baseball field. The existing field consists of a natural grass outfield and a compacted dirt infield. Additional project site structures include two dugouts; bleachers along both the first and third base lines; a storage shed; and batting cages inthe southeast corner directly adjacent to the field. Existing on-site pedestrian walkways include a concrete path stretching from the east to the northern tip of the baseball field, and a gravel path along the northwestern portion of the field. The following downstream drainage path was determined based on City of Edmonds GIS mapping, the site survey, and information gathered during the site visit (refer to Figure 3 –Downstream Drainage Map). The existing on-site drainage infrastructure for the field and tennis courts is comprised of a network of catch basins, storm drainage lines, and trench drains. Catch basins and storm drain lines are located to the east, north, and west of the baseball field, and the tennis courts have trench drain systems. Based onthe existing site topography, as well as on-site investigation of the downstream drainage structures in the site area, stormwater is collected and conveyed in the existing on-site storm drainage system, and directed south of the field to discharge into the public th storm drainage system in 216Street SW. Per online mapping and field investigation, stormwater leaves the site at two separate points, and reaches two separate points of discharge. Stormwater runoff leaving the site east of the field is LPD Engineering, PLLC Page 2 Edmonds Woodway Synthetic Turf Conversion Stormwater Site Plan, February 16, 2018 collected in a catch basin and conveyed further east to a manhole in the driveway for the school’s parking lot, southeast of the project site. From this manhole, flow is conveyed south into the public th storm drainage system in 216Street SW. Stormwater leaving the site on the west side of the field is collected in a catch basin located to the west of the field and at the southern boundary of the project parcel. Stormwater flows from this catch basin into a 12-inch concrete storm pipe that th discharges into the public storm drainage system in 216Street SW. From these two points of on- site discharge, the downstream drainage path is as follows: th 1.Stormwater flows approximately 375 feet east in 216Street SW from the western most point of discharge in a 12-inch concrete storm drain system that transitions into a 12-inch PVC storm drain system at the eastern point of discharge located at the entrance of the school’s parking lot driveway,southeast ofthe project site. th 2.This 12-inch system continues to convey flow approximately 290 feet east down 216 thth Street SW towards a manhole located at the intersection of 216Street SW and 76 Avenue W. (Please see below for a narrative detailing the alternative path for stormwater overflow at this point of conveyance). 3.At this point, stormwater flows approximately 50 feet northeast in a 12-inch concrete pipe th that connects to a catch basin on the east side of 76Avenue W. 4.Flow from this catch basin is thendirected approximately 100 feet south down the east side th of 76Avenue W within a 12-inch concrete channel that directs flow easterly through a densely vegetated area, while transitioning into a 15-inch concrete drainage channel. 5.Stormwater continues to be conveyed approximately 790 feet to the east in this 15-inch system and flows around the perimeter of the Swedish Hospital –Edmonds Campus Building. 6.When the flow in this 15-inch system reaches a manhole located at the southeastern corner of the Swedish Hospital –Edmonds Campus Building, stormwater is then conveyed approximately 155 feet north into an 18-inch HDPE piped system to a manhole on the th northern side of 216Street SW, passing the ¼-mile downstream pointfrom the site. 7.From this manhole, stormwater flow is directed approximately 620 feet east in an 18-inch thth concrete pipe down 216Street SW to a manhole located at the intersection 216Street nd SW and 72Avenue W. At this point the 18-inch system transitions into a 36-inch th concrete conveyance system that continues east in 216Street SW. 8.Within this 36-inch system, stormwater continues to flow approximately 320 feet east in thth 216Street SW, crossing Highway 99 to a manhole on the south side of 216Street SW. 9.Stormwater remains in this 36-inch conveyance system and continues to travel th approximately 575 feet east down 216Street SW until reaching a manhole that directs th stormwater flow southeast to the drainage discharge point into Hall Creek (south of 216 Street SW). Hall Creek ultimately discharges to Lake Ballinger. LPD Engineering, PLLC Page 3 Edmonds Woodway Synthetic Turf Conversion Stormwater Site Plan, February 16, 2018 The underdrain system for the new fields will continue to convey stormwater flow from the site to th the south into the public storm drainage system in 216Street SW. Thus, the downstream drainage course will not be modified by the proposed site improvements. Permanent flow control facilities will be installed, to further attenuate runoff rates from the site. Therefore, the proposed project will not adversely affect the downstream drainage course. AlternativePath for Stormwater Overflow Based on City online mapping of the stormwater infrastructure in the site area, overflow stormwater runoff from the project site is diverted onto an alternative path at the manhole located thth at the intersection of 216Street SW and 76Avenue W. From this manhole stormwater is th conveyed south in a 12-inch concrete piped system in the west side of 76Avenue W. Flow thth continues south in 76Avenue W reaching a manhole located at the intersection of 76Avenue W thth and 220 Street SW. From this point, stormwater is conveyed east down 220Street SW in a 15- th inch concrete piped system until reaching a manhole at the intersection of 220Street SW and Highway 99. Flow from this manhole is directed north into an 18-inch concrete pipe, which th transitions into a 24-inch concrete pipe that conveys flow east in 220Street SW. At this point, stormwater is conveyed north and then east again to discharge into Hall Creek. Upstream Basin Based on site survey and information found on the site visit, the appropriate drainage basins were delineated, including any upstream areas that will be tributary to their respective basins. Due to site topography, there is limited upstream area. The existing storm drainage system for the upstream grass area west of the project site remains unchanged,and is reconnected into the new storm drainage system along the westside of the project site. Allupstream area was included in the mitigated scenario for the MGS Flood model to represent the drainage in the proposed conditions. S ECTION 4 – M INIMUM R EQUIREMENTS The project classification and minimum requirements aredetermined per Figure 3.1of the Edmonds Stormwater Addendum, which applies for any project development.The project will involve more than 5,000 square feet (SF) of new plus replaced hard surfaces and is not a road- related project. Therefore,according to Figure 3.1, all minimum requirements (#1-#9) apply to the new and replaced hard surfaces and converted vegetation areas.See description of minimum requirements for further explanation. LPD Engineering, PLLC Page 4 Edmonds Woodway Synthetic Turf Conversion Stormwater Site Plan, February 16, 2018 Figure 3.1from the 2017Edmonds Stormwater Addendum Below is a list of the Category 2Minimum Requirements and a brief description of how theyare addressed in this project: Minimum Requirement #1: Preparation of Stormwater Site Plan This document is the Stormwater Site Plan. It outlines the existing and proposed site and drainage conditions, describes the flow control systems, and presents the stormwater analysis. Minimum Requirement #2: Construction Stormwater Pollution Prevention The Construction Stormwater Pollution Prevention Plan (SWPPP) is attached in Appendix LPD Engineering, PLLC Page 5 Edmonds Woodway Synthetic Turf Conversion Stormwater Site Plan, February 16, 2018 Cand addressed in Section 6 of this report. This documentation supplements the Temporary Erosion and Sediment Control (TESC) Plans, which areonsheets F-0.3 through F-0.5of Appendix A.Because the project will disturb more than one acreof land, a Construction Stormwater General Permit from the Department of Ecology will be required. The Notice of Intent (NOI) will be provided separately from this report. Minimum Requirement#3: Source Control of Pollution None of the activities listed in Volume IV of the 2014 DOE Manual are applicable to this project. The project will have to adhere to the BMPs for S411, Landscaping and Lawn/Vegetation Management, as source control for landscaped areas. Minimum Requirement #4: Preservation of Natural Drainage Systems and Outfalls The proposed improvements will not alter the existing downstream path. Stormwater will th continue to be routed to the south, to the system in 216Street SW. From here, the same downstream drainage path to Hall Creek will be maintained in the proposed conditions. It is expected that proposed stormwater improvements will attenuate runoff rates from the site. Minimum Requirement#5: Onsite Stormwater Management This project is a Category 2 project, and therefore must adhere to List No. 2 from the 2014 DOE Manual. BMP T5.13 Post-Construction Soil Quality and Depth (found in Volume V of the 2014DOE Manual) will be implemented in all disturbed pervious (landscaping/lawn)areas.The disturbed pervious areas include the restored lawn areas around the field.Permeable pavement will be utilized for the vast majority of walkways. Additionally, the underdrained turf field will act as its own on-site stormwater management BMP, functioning similarly to permeable pavement. Stormwater percolates vertically and horizontally, filtering through the base layers to the underdrain system. This filters stormwater and increases the time of concentration. For more information on the implementation of on-site stormwater management BMPs, see Section 5 of this report. Minimum Requirement#6: Runoff Treatment Runoff treatmentwill be required for theproposed syntheticturf field because it is greater than 5,000 SF of pollution-generating hard surface (PGHS). According to Edmonds City Code section 18.30.060.D.6, projects discharging to Hall Creek must provide Phosphorous Treatment. An option from the Phosphorous Treatment Menu in Volume V of the 2014 DOE Manualwas chosen; the City will allow for a StormFilter structure as an emerging technology. This StormFilter cartridge system will contain Phosphosorb media, which has DOE approval for phosphorous treatment. For more information, refer to the water quality section of this report. Minimum Requirement#7: Flow Control Flow control for the project area will be providedwith two different facilities. The field (and various run-on areas) will be managed by a flow restrictor located on the discharge point from the field underdrain system. The flow restrictor is designed to back stormwater up into the collector drain lines, lateral drain lines, and field subgrade, utilizing the voids in the field base material andthe pipe network in the field for temporary stormwater storage. LPD Engineering, PLLC Page 6 Edmonds Woodway Synthetic Turf Conversion Stormwater Site Plan, February 16, 2018 A separate StormTech detention chamber system will be installed for the east side of the project, which mitigates the proposed tennis courts and portion of the paved walkways. Eachflow restrictor is designed to meet the discharge requirements for the peak flow rates and durations for this site, comparing historical existing site conditions (forested) to proposed conditions for the new and replaced hard surfaces, as well as converted vegetation areas.MGS Flood, which is a DOE-approved continuous runoff modeling program,was used to confirm compliance with applicable standards. Minimum Requirement #8: WetlandProtection There are no wetlandswithin or adjacent to the site. Minimum Requirement#9: Operation and Maintenance An Operations and Maintenance Manual for the project has been prepared and is attached in Appendix D of this report. Additionally, a draft declaration of covenant is attached in Appendix E. S ECTION 5 – P ERMANENT S TORMWATER C ONTROL P LAN The projectwillpropose more than10,000 square feetof effective impervious surface in a threshold discharge area,andtherefore flow controlis required.Per the2017 Edmonds Stormwater Addendum,for the new and replaced hardsurface and convertedvegetationareas,the flow control facility mustbe designedsuch that the proposed discharge durations match the existing/predevelopeddischarge durations for the range of flows from 50% of the 2-year flow through the 50-year flow.Existing/predevelopedconditions are tobe modeled as forested land cover. As mentioned, flow control (minimum requirement #7) will apply to new plus replaced hard surfaces, as well as converted vegetation areas. Per previous conversations with the City of Edmonds, the restored landscaped areas around the field that implement BMP T5.13 are not considered a convertedperviousarea because compost amended soil will allow the area to retain its stormwater functions. However, half the underdrained synthetic turf field(considered 50% impervious/50% pervious)and all of the permeable pavement (modeled as 100% grass)is considered converted pervious areas because BMP T5.13is not applicable.The restored landscaped areas are considered disturbed perviousareas, which do not need to be mitigated by flow control per the minimum requirements. As noted above,the project is required to addressall minimum requirements (#1-9)fornewplus replacedhardsurfaces and converted vegetation areas.For minimum requirement #7, these surfaces are to be mitigated by flow control and are therefore designated as the “target surfaces.” Within the project area there are no existing unmanaged hard surfaces that will remain after project completion. The following tabledescribesthe target surfaces that must be mitigated.The target surfaces include the new and replacedimpervious surfaces, such as standard pavement, roofs, and track surfacing. Other surfaces that are modeled differentlyfrom a stormwater perspective, such as permeable pavement and the underdrained turf field, are still considered hard surfaces, and therefore must be LPD Engineering, PLLC Page 7 Edmonds Woodway Synthetic Turf Conversion Stormwater Site Plan, February 16, 2018 counted as part of the total target surface. Since there are two separate flow control models, there will be a target surface associated with each. Referto Figure 4–Proposed ConditionsTarget Surfacesfor more information on the proposed areas used for the stormwater model. Table 1 –Target Surfaces Square FeetAcres Synthetic Turf Field (116,969 sf total new synthetic turf area considered 58,485 1.343 as 50% Effective Impervious) Tennis Courts 26,270 0.603 (considered as 100% Effective Impervious) Standard Pavement / Track Surfacing 1,768 0.041 (considered as 100% Effective Impervious) Roof Areas 5,667 0.130 (considered as 100% Effective Impervious) Pervious Concrete 20,173 0.463 (considered as 100% Grass) Synthetic Turf Field 58,485 1.343 (other 50% of field as Grass) Total New Plus Replaced Hard Surface 170,848 3.922 (TARGET SURFACE) As shown above in Table 1and in the attached Figure 4–ProposedConditionsTarget Surfaces, the target surfaceis3.922acres,which will require flow control mitigation to historical/forest conditions.The target surface is the minimum amount of areathat is to be mitigated to the forested duration match criteria. The project proposestwo separate detention systems.One will be to utilize the field sub-surface drainage system and base permeable crushed aggregate asastormwater detention system. The other will be a StormTech chamber detention system. Each detention system will have a flow control structure, equipped with a riser (with bottom orifice and optional rectangular notch weir) to temporarily back up flow and utilize storage volume in their respective facilities. The detention basin for the field flow control structure includes the field, and some of the paved walkways directly north and east of the field. For the StormTech flow control structure, the tributary basin includes the proposed tennis courts, surrounding walkways, and batting cage roof. See Figure 5 – Proposed Conditions Modeled Areas for delineation of the two detention basins. There are also new plus replaced hard surfaces that cannot be feasibly collected and routed to detention facilities. These areas are noted as bypass areas, to be accounted for in the field detention model. Also refer to drawingF-1.3 inAppendix A, which is the storm drainage planfor this project. Pre-developed Site Hydrology Refer tothe offsite analysis section of this report for a detailed description of the existing drainage conditions. The existing field is underdrained. In general, there are two discharge points from the existing project area. There is an 18” storm line running across the existing northeast tennis courts th that convey flow south, eventually to the existing storm system in 216Street SW. There is also LPD Engineering, PLLC Page 8 Edmonds Woodway Synthetic Turf Conversion Stormwater Site Plan, February 16, 2018 another site discharge point southwest of the field, where there is another piped connection to the th storm line in 216Street SW. Proposed Site Hydrology The overall drainage patterns throughout the site are not being changedby the proposed improvements.There will be two flow control structures designed to attenuate runoff rates from the site. One flow control structure will be for the field detention basin and the other for the tennis th court basin. There will be two separate connection points to the existing storm system in 216 Street SW. Rainfalling upon the proposed synthetic turf will be collected in an underdrain system. No surface runoff is anticipated from thesesurfacesbecause of the permeable nature of the materials.The synthetic turf surface includes a tufted fiber and woven synthetic backing that is perforated to allow a minimum vertical infiltration rate of 20 inches per hour.The synthetic turf is infilled with a mixture of rounded sand particles and granulated rubber that do not interlock and are also highly permeableand has a minimum vertical infiltration rate of 20 inches per hour. Below the synthetic turf surface is a topcourse and base course permeable crushed aggregate constructed of a specially graded sand and gravel mixture that results in a permeable basebelow the field. The vertical infiltration rates through the synthetic turf are tested by an independent third-party testing agency after manufacture of the turf. Testing of the permeable aggregate occurs on site after placement and compaction. For the field drainage basin, stormwater will percolate vertically and gradually horizontally through the base crushed rock layer to the nearest drainage lateral trench. Refer to the field cross section on sheet F-2.1 inAppendix A.Once stormwater infiltrates into the drainage lateral trenches, it will be conveyed via 4-inch perforated drain lines toa12-inch main collector drain line as noted on the drainage plans, flowingnortheast to southwest.The 12-inch maincollector line will connectto a Type-2catch basin with a flow control riser pipe,located southwestof the field, outside of the field surfacing. Downstream of the flow control structure, the proposed drainage conveyance will route th to a StormFilter water quality structure and then connect to the existing system in 216Street SW. Thefieldflow restrictorisdesigned to temporarily back stormwater up into the field permeable base aggregate, the perforated sub-surface drain lines, and the collector drain line. The permeable base aggregates are assumed to have a void ratio of 30%by volume.Alimited amount of infiltration is expected tooccur beneath the field when the stormwaterisstored withinthe field base permeable aggregate.However, based upon geotechnical evaluation, it is assumed that infiltration will not be feasible for the site, and therefore no infiltration was included in the stormwater modeling. The “tennis court basin” includes drainage from the proposed tennis courts, as well as portions of the surrounding walkway. For detention, a StormTech chamber detention system will be utilized at the southeast portion of the project area. Aflow control structure will be located outside of the StormTech footprint. The control structure will have a riser with a bottom orifice and notch weir to attenuate flows and utilize the storage volume in the chambers and permeable gravel basin that the chambers sit in. The outlet from this flow control structure will convey flow south, connecting with th a storm manhole in 216Street SW. LPD Engineering, PLLC Page 9 Edmonds Woodway Synthetic Turf Conversion Stormwater Site Plan, February 16, 2018 The flow control structuresaredesigned to release stormwater at the allowable rates defined by the MGS Flood with thePuget East 36 time series, as outlined by section 2.1 of the 2017 Edmonds Stormwater Addendum.The system is designed to meet thestandardflow duration standard, comparing the predeveloped stormwater discharges to the developed discharges for the range of 50% of the 2-year peak flow up to the full 50-year peak flow. On-Site Stormwater Management (MR #5) Per section 5.5 of the 2017 Edmonds Stormwater Addendum, on-site stormwater management best management practices (BMPs) must be implemented per List #2 of the DOE manual unless infeasibility criteria (from Appendix A of the 2017 ESA) can be provided for each BMP.This project is proposing to use compost amended soil (BMP T5.13) for disturbed pervious areas and permeable pavement for the vast majority of paved walkways. The following table shows the List #2 on-site stormwater management BMPs and whether are not they will be feasible for this project. LPD Engineering, PLLC Page 10 Edmonds Woodway Synthetic Turf Conversion Stormwater Site Plan, February 16, 2018 Table 2–On-Site Stormwater Management BMP Evaluation Feasibility BMP Explanation Lawn/Landscaped Areas Post-Construction YesPost-Construction Soil Quality and Depth per BMP T5.13 will be utilized Soil Quality and for all disturbed pervious areas. Restored lawn areas on the project site Depth include the area beyond the proposed outfield fence and the area vacated by the demolished tennis courts north of the baseball field. Roofs Full Dispersion NoA 65 to 10 ratio of forested or native vegetation area to impervious area cannot be achieved. Downspout Full NoBased on geotechnical evaluation, infiltration is not recommended for this Infiltration Systems site. Soils would be slow-draining. Downspout infiltration systems would not be recommended. Bioretention / Rain NoRoof drainage from the dugouts and batting cages cannot be feasibly Gardens routed to bioretention. The dugout roofs sheet flowdirectly onto the proposed turf field surface. Batting cage roof cannot be routed via gravity to a bioretention area and still be conveyed to the detention system. Downspout NoThe dugout roofs will sheet flow onto the field surface; the batting cage Dispersion Systemsroofs do not have a vegetated area that provides positive drainage. Perforated Stub-Out NoBased on geotechnical evaluation, infiltration is not recommendedfor this Connections site. Soils would be slow-draining. Perforated stub-out connections would not be recommended. Detention Vaults and YesDetention systems are provided, though not the traditional vaults and Pipes pipes. A StormTech chamber detention system willbe used for the proposed tennis courts and surrounding areas. A sub-base field aggregate detention system will be used for the proposed field and its basin. Other Hard Surfaces Full Dispersion NoA 65 to 10 ratio of forested or native vegetation area to impervious area cannot be achieved. Permeable Pavement YesPermeable pavement will be utilized in this project for the vast majority of walkways around the tennis courts and field. The field drainage system itself does hydraulically act similarto permeable pavement. The surface materials are permeable and as water percolates vertically and horizontally to the nearest drainage lateral, thus increasing the time of concentration is significantly. Therefore, runoff rates are being reduced and the field is acting as its own on-site stormwater management BMP. Bioretention / Rain NoDue to the presence of permeable pavement and the field drainage system Gardens acting in a similar fashion, it would not be feasible to route these areas via gravity to a bioretention area as an additional BMP. Sheet Flow NoIn general, sheet flowdispersion cannot be met because positive drainage Dispersion for sheet flow cannot be achieved. The grass areas west of the project area are at higher elevation than the proposed field. Concentrated Flow NoConcentrated flow dispersion is not feasiblebecause there are no Dispersion concentrated flows as a result of the proposed project. A minimum vegetated flowpath of 50 feet cannot be met. Detention Vaults and YesDetention systems are provided, though not the traditional vaults and Pipes pipes. A StormTech chamber detention system will be used for the proposed tennis courts and surrounding areas. A sub-base field aggregate detention system will be used for the proposed field and its basin. LPD Engineering, PLLC Page 11 Edmonds Woodway Synthetic Turf Conversion Stormwater Site Plan, February 16, 2018 Water Quality (MR #6) The City of Edmonds is considering the proposed field to be a pollution-generating surface that will require water quality treatment. The field area is greater than the thresholds requiring treatment, which are 5,000 SF pollution-generating hard surface (PGHS) and ¾ acre of pollution- generating pervious surface (PGPS). Per section 18.30.060 of the Edmonds City Code, the project will require Phosphorous Treatment since the project drains to Hall Creek. Therefore, the project will select an option from the Phosphorous Treatment Menu, section 3.3 of Volume V of the DOE Manual. Per coordination with the City, it will be permissible to use a StormFilter structure for treatment, which is considered an “emerging stormwater treatment technology” by the DOE Manual.A StormFilter structure with Phosphosorb media has been proposed, which is GULD-approved (General Use Level Designation) by the Department of Ecology. The StormFilter system was designed by Contech Engineered Solutions; sizing and cost information for theStormFilter are attached in Appendix B. The treatment facility is downstream of the field detention system, and thus the 2-year release rate was used as the water quality design flow rate (section 4.1.2, Volume V of the DOE Manual). The resulting system is 3 Phosphosorb cartridges within a 48-inch manhole that will be located southwest of the proposed field. The separate flow control structure will precede this structure. Flow Control System (MR #7) Field Detention System The flow restrictor and the storage volume within the field subsurface drainage systemhave been modeled using MGS Flood.The DOE Manual does not explicitly state a method for modeling underdrained sports fields. Basedon LPD’s extensive modeling experienceandworkwith DA Hogan(field designer)on numerous field projects, the field surfacing has been modeled as 50% impervious and 50%pervious grass. The City of Edmonds has accepted this modeling approach. However, the entire field must be taken back to forested in the predeveloped condition because the field is considered a “hard surface.” Thus, it is part of the overall target surface. In the field detention basin, there will be some amount of pervious concrete, which is being used for walkway surfacing north and east of the field.According to Appendix III-C of the DOE Manual, the pervious concrete without underlying drain pipes are modeled as grass. However, the pervious concrete is still considered a new plus replaced hard surface, and therefore, must be modeled as forested in the predeveloped condition, much like the field. There are portions of new plus replaced hard surface that cannot be feasibly routed to the detention systems. However, because they are part of the target surface, they must be mitigated and counted as forested for the predeveloped condition. In the mitigated scenario, they will be placed into a bypass basin, that connects to a point of compliance downstream of the detention system. These bypass areas will be accounted for in the MGS Flood model for the field basin. Bypass areas include strip of track surfacing in the northwest corner of the project area and small amounts of pervious concrete walkway on the east side of the site. In order to get the model to accurately represent the flow of stormwater through the flow restrictor, the actual surface conditions contributing runoff to the flow restrictor has to be includedin the developed basin.As mentioned, this includes field modeled as 50% effective impervious, pervious LPD Engineering, PLLC Page 12 Edmonds Woodway Synthetic Turf Conversion Stormwater Site Plan, February 16, 2018 concrete modeled as 100% grass,and other hard surfaces modeled as 100% impervious. Any target surface (new plus replaced surface), listed in Table 1, will be considered forested in the predeveloped scenario. However, any other tributary disturbed pervious areas do not require flow control mitigation, and are therefore entered as a predeveloped grass area. A bypass basin has been modeled to represent the areasrequiring flow control which areoutside of the detention basin. The field aggregate depth and flow control structure will be designed to over-detain for the bypass area. Tables 3,4, and 5below summarize the MGS Flood modeling input. Table 3–Modeled Predeveloped Area–Field Basin Square FeetAcres Forested Area 130,454 2.995 Grass Area 52,209 1.198 Total Effective Predeveloped Area 182,663 4.193 Table 4–Modeled Mitigated Area –Field Detention Basin Square FeetAcres Impervious Area 59,327 1.362 Grass Area 121,347 2.786 Total Effective Mitigated Area 180,6734.148 Table 5–Modeled Bypass Area –Field Basin Square Feet Acres Impervious Area 1,668 0.038 Grass Area 322 0.007 Total Effective Bypass Area 1,990 0.046 Due to the unique natureof the storage volume within the field’s underdrain system, a custom stage storage spreadsheet has been createdfor implementation into MGS Flood. This Field Stage Storage Volume Spreadsheet is attached in Appendix B.This spreadsheet was used to determine the volume within the underdrain system at a given elevation, accounting for storage within the permeable basecourse section, as well as in the underdrain piping and their trenches.To create the stage storage table, a range of elevationswas input into the spreadsheet, beginning with the collector pipe outlet invert elevation as the starting stage, and continuing up to the maximum water surface elevation within the gravel base as the maximum stage. This allowed a custom stage storage table to becreated and inputinto the stage volume table ofthe MGS Flood program. The storage volume provided in the field detention facility isa maximum ofapproximately 29,887 cubic feetat the elevation of the top of the flow restrictor. Once the stage storage tablewas implemented within the MGS Flood, the control structure was manually adjusted in order to match the durationand discharge requirementsfor forested predeveloped conditions.Thefield detention systemcontrol structure will be a12-inch riser within aType-2catchbasin located west of the proposed fieldand will include a singlebottom orifice and LPD Engineering, PLLC Page 13 Edmonds Woodway Synthetic Turf Conversion Stormwater Site Plan, February 16, 2018 flat top riser.The orifice will be 0.9inchesin diameter. Theriser height was determined to be 4.56 feet, so the overflow elevation willbe 416.80based on the outlet pipe invert elevation of 412.24 The fieldsection is 15” deep,from the field surface to the top of the lateral trenches, so the riser height indicates that water will be stored up towithin6-inchesofthe field surface, allowing for a totalstormwater detention storage volume of 29,887cubicfeet to be stored within the lateral pipes, collector pipe,gravel trenches, and field basepermeable aggregate.The field section includes a 2- inch turf layer, 2-inch top course layer, and 11-inch permeable base course layer. Only 9-inches of the base course layer is being usedfor storage, to allow the 6-inch clearance from the max water surface and the field surface. Refer to the complete output from MGS Floodprovided within Appendix B. Graph 1 below shows theflow duration plot from MGS Flood.Also refer to Sheet F- 2.5which details the flow control structure for the field area. Graph 1 –FieldFlow Duration Plot StormTech Detention System (Tennis Court Basin) The StormTech chambers and gravel basin have a non-uniform change in storage volume as the stage height increases. To account for this, a stage storage spreadsheet wasused to calculate the storage within the StormTech chambers and surrounding gravel material at an interval of stage heights. A copy of this spreadsheet is included within Appendix B. The stage storage information for a single SC-740 chamberwas provided by StormTech and used to determine the total cumulative storage between the chambers and surrounding gravel material. The void space within the gravel material was assumed to be 40%, which is the industry standard. Based upon geotechnical evaluation, it was assumed that there is no infiltration into the native soils. LPD Engineering, PLLC Page 14 Edmonds Woodway Synthetic Turf Conversion Stormwater Site Plan, February 16, 2018 The modeled mitigated (postdeveloped) conditions include one basin routed to the StormTech detention system, which includes the proposed tennis courts,portions of the surrounding paved walkways, and the roofed batting cages. It will be referred to as the “tennis court basin” to differentiate it from the fields system. A small amount of tributary pervious area is entered into the modelas grass. Impervious area routed to detention includes all targethardsurfaces within this basin. In the modeled predeveloped (existing) conditions, there must be a forested area equal to the target surface(in this basin)that requires mitigation. Anytributary pervious area is not part of the target surface, and therefore is entered as a predeveloped grass area. The detention basin is outlined on Figure 5, which shows the areas that are routed to the StormTech detention system. The complete MGS Floodoutput is attached in Appendix B of this report. Table 6–Modeled Predeveloped Area –Tennis Court Basin Square FeetAcres Forested Area 40,393 0.927 Grass Area 2,809 0.065 Total Effective Predeveloped Area 43,202 0.992 Table 7–Modeled Mitigated Area –Tennis Court Detention Basin Square Feet Acres Impervious Area 31,195 0.716 Grass Area 12,0070.276 Total Effective Mitigated Area 43,202 0.992 Much like the field detention storage, due to the unique nature of the storage volume within the StormTech detention system, a custom stage storage spreadsheethas been created for implementation in to the MGS Flood model. This Stage Storage Table Spreadsheet is attached in Appendix B; the spreadsheetisused to determine the volume within the StormTech system at a given elevation. To create the stage storage table, a range of elevations was input into the spreadsheet, beginning with the bottom of the gravel basin (6-inches below bottom of chambers) and continuing up to the maximum water surface elevation where the gravel basin extends 6-inches above the top of the chambers. In the bottom and top 6-inches of the system, storage is only within the void space of the gravel. This allowed a custom stage storage table to be created and input into thestructureelement in the MGS Flood program. The storage volume provided in the proposed StormTech detention facility is approximately 18,368cubicfeet at the elevation of the top of the flow restrictor. Once the stage storage table wasimplemented into the MGS Flood model, the control structure was manually adjusted in order to match the duration and discharge requirements for forested predeveloped conditionsfor the target surfaces. The StormTech flowcontrol structure includes a single orifice on a 12-inch riserwith a rectangular notch weir. The control structure will be within a Type-2 catch basin located to the southeast of thefacility footprint. The bottom orifice will be 0.5- inchesindiameter;the rectangular notch will have a height of 18-inches (from the top of the riser) LPD Engineering, PLLC Page 15 Edmonds Woodway Synthetic Turf Conversion Stormwater Site Plan, February 16, 2018 and width of 0.25-inches. The riser height was determined to be5.71feet, corresponding with the height of the StormTech chambersystem, includingthe 6-inches of gravel cover above and below. Refer to the complete output from MGS Flood provided within Appendix B. Graph 2below shows the flow duration plot for the tennis court detention basin from MGS Flood.Also refer to Sheet F- 2.5(in Appendix A)which details the flow control structure for the StormTech system.The StormTech chamber details are on sheet F-2.4. Graph 2 –Tennis Court Basin Flow Duration Plot Conveyance System Analysis and Design An analysis of the onsite conveyance system was performed forthe 12-inch outlet from the field detention system and the 12-inchoutlet from the StormTech detention system.The 2014 DOE manual only requires analysis for the 25-year peak storm for new conveyance systems. However, each pipe analyzed will be compared to the 100-year peak runoff rate as well. These peak flows will be determined using MGS Flood with 15-minute time steps. This was compared to the full- flow capacity of the conveyance pipe, which was determined using Manning’s equation. Refer to Appendix B for the Conveyance Analysis Spreadsheetand associated MGS Flood reports. A conveyance analysis was performed for the outlet from the field detention system.The field detention basin is shown on Figure 5 –Proposed Conditions Modeled Areas, and includes the field and some surrounding walkways and landscaped areas.As previously mentioned, the underdrained turf field is modeled as 50% impervious, 50% grass and pervious concrete is modeled as 100% grass. The 12-inch pipe(n=0.012)with a slope of 1.0% has a capacity of 3.87cfs. The peak flow LPD Engineering, PLLC Page 16 Edmonds Woodway Synthetic Turf Conversion Stormwater Site Plan, February 16, 2018 from the 25-year storm eventwasfound to be 1.66cfs, and the 100-year storm peak flow is2.84 cfs. Therefore, the 12-inchpipe has sufficient conveyance capacity for the design. Conveyance analysis was alsoperformed for the StormTech outlet, which is conveying the tennis court basin as seen on Figure 5.The 12-inch pipe(n=0.012)with a minimum slope of 0.5% has a capacity of 0.93 cubic feet per second (cfs). From MGS Flood, the 25-year and 100-year peak flows were found to be 0.56 cfs and 0.88 cfs, respectively. Therefore, the 12-inch StormTech outlet has sufficient conveyance capacity. S ECTION 6 – C ONSTRUCTION S TORMWATER P OLLUTION P REVENTION P LAN (SWPPP) The SWPPP narrative for this project can be found in Appendix C.ThepreliminarySWPPP is based on Volume II of the 2014DOE Surface Water Management Manual requirements. An NPDES permit from the Washington State Department of Ecology will be required for the project because it disturbs over one (1) acre of land area. The TESC plan includes temporary sediment settling tanks.A minimum volume was calculated using the methodology fromthe 2014DOE manual, with the 2-year developed flow rate from MGS Flood. Avolume of an equivalent sediment trap was calculated to find the necessary volume for sediment tank(s)for this project. A copy of the Sediment TankSizing Calculations worksheet used for this exercise is attached in Appendix B.Stormwater runoff from theproject work area will be directed toward theinterceptor swale along thesouth and east sidesofthe project area.The swaleswill convey flow to the temporary sump pump(s) and then stormwater will be pumped to the temporary sediment settling tanklocatedto the eastof theproject area.Inaddition to the sediment settling tanks,TESC elements in the project include the following: Temporary Stabilized Construction Entrances, per BMP C105 Catch Basin Filters, per BMP C220 Silt Fence, per BMP C233 Temporary Interceptor Swale, per BMP C200 Rock Check Dam, per BMP C207 The TESC elements shown are intended to be the minimum allowable. The NPDES permit will require periodic inspection of the TESC elements to confirm they are holding up and continuing to function as intended. During construction, the contractor is responsible for upgrading these facilities as necessary. The implementation of the TESC plan and construction maintenance, replacement and upgrading of the TESC facilities are the responsibility of the contractor, per the contract documents. The TESC facilities will be constructed prior to and in conjunction with all clearing and grading activity and in a manner in which sediment or sediment laden water does not leave the project site, enter thedrainage system, or violate applicable water quality standards. S ECTION 7 – O THER R EPORTS AND S TUDIES A geotechnical report was prepared by Associated Earth Sciences, Inc., dated May 9, 2017and is under separatecover. LPD Engineering, PLLC Page 17 Edmonds Woodway Synthetic Turf Conversion Stormwater Site Plan, February 16, 2018 S ECTION 8 – O THER P ERMITS The project involves over an acre of land disturbing activity, and therefore an NPDES permit will be required. This will be permitted separately, directly with the Department of Ecology. S ECTION 9 – O PERATION AND M AINTENANCE M ANUAL The operation and maintenance guidelinesfor this project has been attached in Appendix Dof this report. This includes required maintenance activities for catch basinsandcontrol structures. S ECTION 10 – B OND Q UANTITIES W ORKSHEET A Bond Quantities Worksheet is not expected to be required since the owner is the Edmonds School District, which is a public agency. No bonding is required. LPD Engineering, PLLC Page 18 Edmonds Woodway Synthetic Turf Conversion Stormwater Site Plan, February 16, 2018 FIGURES Figure 1: Vicinity Map Figure 2: Soil Map Figure 3: Downstream Drainage Map Figure 4: Proposed Conditions Target Surfaces Figure 5: Proposed Conditions Modeled Areas 3 INTO HALL CREEK DISCHARGE INTO HALL CREEK 36" CONCRETE SD DISCHARGE DOWNSTREAM DRAINAGE MAP 24" CONCRETE SD 18" CONCRETE SD 18" HDPE SD 18" CONCRETE SD CHANNEL 15" CONCRETE 15" CONCRETE SD APPROXIMATELY 1/4 MILE DOWNSTREAM FROM SITE 12" CONCRETE SD 12" CONCRETE SD 12" PVC SD SCHOOL PROPERTY OVERFLOW ROUTE TO SOUTH DISCHARGE POINTFROM PROPERTY 12" CONCRETE SD DISCHARGE POINTFROM PROPERTY 2018 LPD Engineering PLLC APPENDIX A Design Drawings APPENDIX B Design Calculations and Supporting Information EdmondsWoodwayHSBaseballFieldStorageVolume topsurfaceoffieldatlowestPt:417.3feet<Thiselevationisthelowestelevationinthefieldthatistributarytothesubsurfacedrainagesystem TurfLayer2inches TopgravelcourseLayer2inches gravelbaseabovelateraltrenches:11inches TotalDepthofsurfacing15inches topelevationofthelowestlateraltrench:416.05feet topsurfaceofwaterstoredintrenches:416.05feet WaterSurfaceElevation 416.8 topsurfaceofwaterstoredingravelbase:416.80 depthofgravelbeneathlateralpipeinvert:2inches lateraltrenchwidth:12inches voidratiooflateraltrenchgravel:0.3 FieldArea:116969sf FieldSlope0 WaterSurfaceArea:116,969.0 squarefeet TotalVolumeStoredinTrenchesandPipes:3,569cubicfeet :26,318cubicfeet TotalVolumeStoredAboveTrenches TotalVolumeStored:29,886.6 cubicfeet MaximumDepthPondedinBaseLayer:9.00inches MainCollectorPipe(s): PipeXsectPipeXsectArea Area@@DownstreamVolumein Diameter Run#Length(in)IEupstreamIEdownstreamSlopeUpstreamEndEndPipe 143412414.41412.240.0050.7850.785340.86340.863 0.0000.0000.00 0.0000.0000.00 0.0000.0000.00 0.0000.0000.00 0.0000.0000.00 TotalVolumeinCollectorPipes: 340.86 DrainageLateralPipes:VolumeStoredinPipeVolumeStoredinLateralTrenches XsectAreaofXsectAreaof WaterDepthVolumeStored PipeXsectPipeXsectArea@StoredWaterinStoredWaterinTotalVolumeinLateralTrenchLengthof Area@@DownstreamDownstreamtrenchLateralTrench@LateralTrench@ofLateralTotalVolume(w/voidratioTrenchUsedWaterSurface VolumeinWaterDepth@ Run#LengthDiameterIEupstreamIEdownstreamSlopeUpstreamEndEndPipeUpstreamEndEndwidthUpstreamEndDownstreamEndTrenchPipeVolumeapplied)(LF)Area(SF) W1154415.39415.360.00200.0870.0871.310.8270.857120.8270.85712.611.33.415.015.00 W2304415.39415.240.00500.0870.0872.620.8270.977120.8270.97727.124.47.330.030.00 W3454415.39415.160.00510.0870.0873.930.8271.057120.8271.05742.438.411.545.045.00 W4604415.39415.090.00500.0870.0875.240.8271.127120.8271.12758.653.416.060.060.00 W51034415.39414.870.00500.0870.0878.990.8271.347120.8271.347111.9102.930.9103.0103.00 W61184415.39414.800.00500.0870.08710.300.8271.417120.8271.417132.4122.136.6118.0118.00 W71334415.39414.720.00500.0870.08711.610.8271.497120.8271.497154.5142.942.9133.0133.00 W81484415.39414.650.00500.0870.08712.920.8271.567120.8271.567177.1164.249.3148.0148.00 W91624415.39414.580.00500.0870.08714.140.8271.637120.8271.637199.5185.455.6162.0162.00 W101624415.39414.580.00500.0870.08714.140.8271.637120.8271.637199.5185.455.6162.0162.00 W111624415.39414.580.00500.0870.08714.140.8271.637120.8271.637199.5185.455.6162.0162.00 W121624415.39414.580.00500.0870.08714.140.8271.637120.8271.637199.5185.455.6162.0162.00 W131674415.39414.550.00500.0870.08714.570.8271.667120.8271.667208.2193.658.1167.0167.00 W141824415.39414.480.00500.0870.08715.880.8271.737120.8271.737233.3217.465.2182.0182.00 W151974415.39414.400.00500.0870.08717.190.8271.817120.8271.817260.4243.273.0197.0197.00 W162124415.39414.330.00500.0870.08718.500.8271.887120.8271.887287.6269.180.7212.0212.00 W172254415.39414.260.00500.0870.08719.630.8271.957120.8271.957313.1293.588.0225.0225.00 W182114415.39414.330.00500.0870.08718.410.8271.887120.8271.887286.3267.880.4211.0211.00 W191964415.39414.410.00500.0870.08717.100.8271.807120.8271.807258.1241.072.3196.0196.00 W201814415.39414.480.00500.0870.08715.800.8271.737120.8271.737232.0216.264.9181.0181.00 W211664415.39414.560.00500.0870.08714.490.8271.657120.8271.657206.1191.657.5166.0166.00 W221514415.39414.630.00500.0870.08713.180.8271.587120.8271.587182.2169.050.7151.0151.00 W231364415.39414.710.00500.0870.08711.870.8271.507120.8271.507158.7146.844.0136.0136.00 W241214415.39414.780.00500.0870.08710.560.8271.437120.8271.437136.9126.437.9121.0121.00 W251064415.39414.860.00500.0870.0879.250.8271.357120.8271.357115.7106.531.9106.0106.00 W26914415.39414.930.00510.0870.0877.940.8271.287120.8271.28796.288.226.591.091.00 W27764415.39415.010.00500.0870.0876.630.8271.207120.8271.20777.370.621.276.076.00 W28614415.39415.080.00510.0870.0875.320.8271.137120.8271.13759.954.616.461.061.00 E1154415.39415.360.00200.0870.0871.310.8270.857120.8270.85712.611.33.415.015.00 E2304415.39415.240.00500.0870.0872.620.8270.977120.8270.97727.124.47.330.030.00 E3454415.39415.160.00510.0870.0873.930.8271.057120.8271.05742.438.411.545.045.00 E4604415.39415.090.00500.0870.0875.240.8271.127120.8271.12758.653.416.060.060.00 E51034415.39414.870.00500.0870.0878.990.8271.347120.8271.347111.9102.930.9103.0103.00 E61184415.39414.800.00500.0870.08710.300.8271.417120.8271.417132.4122.136.6118.0118.00 E71334415.39414.720.00500.0870.08711.610.8271.497120.8271.497154.5142.942.9133.0133.00 E81474415.39414.650.00500.0870.08712.830.8271.567120.8271.567175.9163.148.9147.0147.00 E91624415.39414.580.00500.0870.08714.140.8271.637120.8271.637199.5185.455.6162.0162.00 E101624415.39414.580.00500.0870.08714.140.8271.637120.8271.637199.5185.455.6162.0162.00 E111624415.39414.580.00500.0870.08714.140.8271.637120.8271.637199.5185.455.6162.0162.00 E121624415.39414.580.00500.0870.08714.140.8271.637120.8271.637199.5185.455.6162.0162.00 E131674415.39414.550.00500.0870.08714.570.8271.667120.8271.667208.2193.658.1167.0167.00 E141824415.39414.480.00500.0870.08715.880.8271.737120.8271.737233.3217.465.2182.0182.00 E151974415.39414.400.00500.0870.08717.190.8271.817120.8271.817260.4243.273.0197.0197.00 E162124415.39414.330.00500.0870.08718.500.8271.887120.8271.887287.6269.180.7212.0212.00 E172234415.37414.260.00500.0870.08719.460.8471.957120.8471.957312.6293.187.9223.0223.00 E182084415.37414.330.00500.0870.08718.150.8471.887120.8471.887284.3266.179.8208.0208.00 E191934415.37414.410.00500.0870.08716.840.8471.807120.8471.807256.0239.271.8193.0193.00 E201784415.37414.480.00500.0870.08715.530.8471.737120.8471.737229.9214.464.3178.0178.00 E211634415.37414.560.00500.0870.08714.220.8471.657120.8471.657204.0189.856.9163.0163.00 E221484415.37414.630.00500.0870.08712.920.8471.587120.8471.587180.1167.250.1148.0148.00 E231334415.37414.710.00500.0870.08711.610.8471.507120.8471.507156.5144.943.5133.0133.00 E241184415.37414.780.00500.0870.08710.300.8471.437120.8471.437134.7124.437.3118.0118.00 E251034415.37414.860.00500.0870.0878.990.8471.357120.8471.357113.5104.531.3103.0103.00 E26884415.37414.930.00500.0870.0877.680.8471.287120.8471.28793.986.225.988.088.00 E27734415.37415.010.00490.0870.0876.370.8471.207120.8471.20774.968.620.673.073.00 E28584415.37415.080.00500.0870.0875.060.8471.137120.8471.13757.552.515.758.058.00 TotalVolumeinLateralPipes:656.42416.2166667TotalVolumeinLateralTrenches:2571.3 TotalAreainLateralTrenches:7522.00SF 0.172681359AC MGS FLOOD PROJECT REPORT FLOW CONTROL FIELD BASIN Program Version: MGSFlood 4.46 Program License Number: 201410003 Project Simulation Performed on: 02/13/2018 4:25 PM Report Generation Date: 02/13/2018 4:26 PM Input File Name: Field Detention-FINAL.fld Project Name: Edmonds Woodway HS Analysis Title: Flow Control Comments: field basin only PRECIPITATION INPUT Computational Time Step (Minutes): 60 Extended Precipitation Time Series Selected Climatic Region Number: 14 Full Period of Record Available used for Routing Precipitation Station : 96003605 Puget East 36 in_5min 10/01/1939-10/01/2097 Evaporation Station : 961036 Puget East 36 in MAP Evaporation Scale Factor : 0.750 HSPF Parameter Region Number: 1 HSPF Parameter Region Name : USGS Default ********** Default HSPF Parameters Used (Not Modified by User) *************** ********************** WATERSHED DEFINITION *********************** Predevelopment/Post Development Tributary Area Summary Predeveloped Post Developed Total Subbasin Area (acres) 4.193 4.193 Area of Links that Include Precip/Evap (acres) 0.000 0.000 Total (acres) 4.193 4.193 ----------------------SCENARIO: PREDEVELOPED Number of Subbasins: 1 ---------- Subbasin : Subbasin 1 ---------- -------Area (Acres) -------- Till Forest 2.995 Till Grass 1.198 ---------------------------------------------- Subbasin Total 4.193 ----------------------SCENARIO: POSTDEVELOPED Number of Subbasins: 2 ---------- Subbasin : Field Basin ---------- -------Area (Acres) -------- Till Grass 2.786 Impervious 1.362 ---------------------------------------------- Subbasin Total 4.148 ---------- Subbasin : Bypass ---------- -------Area (Acres) -------- Till Grass 0.007 Impervious 0.038 ---------------------------------------------- Subbasin Total 0.045 ************************* LINK DATA ******************************* ----------------------SCENARIO: PREDEVELOPED Number of Links: 0 ************************* LINK DATA ******************************* ----------------------SCENARIO: POSTDEVELOPED Number of Links: 2 ------------------------------------------ Link Name: Detention Link Type: Structure Downstream Link Name: New Copy Lnk2 User Specified Elevation Volume Table Used Elevation (ft) Pond Volume (cu-ft) 100.00 0. 100.30 1. 100.60 2. 100.90 3. 101.15 4. 101.45 6. 101.75 30. 102.05 67. 102.35 94. 102.65 118. 102.95 141. 103.25 167. 103.55 273. 103.85 627. 104.15 1247. 104.45 2292. 104.75 3095. 105.05 6727. 105.15 10236. 105.25 13745. 105.35 17254. 105.45 20763. 105.55 24272. 105.65 27781. 105.71 29887. 105.81 33396. Constant Infiltration Option Used Infiltration Rate (in/hr): 0.00 Riser Geometry Riser Structure Type : Circular Riser Diameter (in) : 12.00 Common Length (ft) : 0.000 Riser Crest Elevation : 105.71 ft Hydraulic Structure Geometry Number of Devices: 1 ---Device Number 1 --- Device Type : Circular Orifice Control Elevation (ft) : 100.00 Diameter (in) : 0.85 Orientation : Horizontal Elbow : No ------------------------------------------ Link Name: New Copy Lnk2 Link Type: Copy Downstream Link: None **********************FLOOD FREQUENCY AND DURATION STATISTICS******************* ----------------------SCENARIO: PREDEVELOPED Number of Subbasins: 1 Number of Links: 0 ----------------------SCENARIO: POSTDEVELOPED Number of Subbasins: 2 Number of Links: 2 ********** Subbasin: Field Basin ********** Flood Frequency Data(cfs) (Recurrence Interval Computed Using Gringorten Plotting Position) Tr (yrs) Flood Peak (cfs) ====================================== 2-Year 0.479 5-Year 0.656 10-Year 0.808 25-Year 1.111 50-Year 1.271 100-Year 1.313 200-Year 1.706 ********** Subbasin: Bypass ********** Flood Frequency Data(cfs) (Recurrence Interval Computed Using Gringorten Plotting Position) Tr (yrs) Flood Peak (cfs) ====================================== 2-Year 1.058E-02 5-Year 1.335E-02 10-Year 1.564E-02 25-Year 1.786E-02 50-Year 2.094E-02 100-Year 2.364E-02 200-Year 2.556E-02 ********** Link: Detention ********** Link Inflow Frequency Stats Flood Frequency Data(cfs) (Recurrence Interval Computed Using Gringorten Plotting Position) Tr (yrs) Flood Peak (cfs) ====================================== 2-Year 0.479 5-Year 0.656 10-Year 0.808 25-Year 1.111 50-Year 1.271 100-Year 1.313 200-Year 1.706 ********** Link: Detention ********** Link Outflow 1 Frequency Stats Flood Frequency Data(cfs) (Recurrence Interval Computed Using Gringorten Plotting Position) Tr (yrs) Flood Peak (cfs) ====================================== 2-Year 4.399E-02 5-Year 4.496E-02 10-Year 5.599E-02 25-Year 0.190 50-Year 0.220 100-Year 0.301 200-Year 0.362 ********** Link: Detention ********** Link WSEL Stats WSEL Frequency Data(ft) (Recurrence Interval Computed Using Gringorten Plotting Position) Tr (yrs) WSEL Peak (ft) ====================================== 1.05-Year 104.850 1.11-Year 104.964 1.25-Year 105.051 2.00-Year 105.207 3.33-Year 105.328 5-Year 105.438 10-Year 105.717 25-Year 105.767 50-Year 105.774 100-Year 105.793 ********** Link: New Copy Lnk2 ********** Link Inflow Frequency Stats Flood Frequency Data(cfs) (Recurrence Interval Computed Using Gringorten Plotting Position) Tr (yrs) Flood Peak (cfs) ====================================== 2-Year 5.152E-02 5-Year 5.550E-02 10-Year 6.858E-02 25-Year 0.191 50-Year 0.224 100-Year 0.306 200-Year 0.369 ***********Compliance Point Results ************* Scenario Predeveloped Compliance Subbasin: Subbasin 1 Scenario Postdeveloped Compliance Link: New Copy Lnk2 *** Point of Compliance Flow Frequency Data *** Recurrence Interval Computed Using Gringorten Plotting Position Predevelopment Runoff Postdevelopment Runoff Tr (Years) Discharge (cfs) Tr (Years) Discharge (cfs) ---------------------------------------------------------------------------------------------------------------------- 2-Year 9.501E-02 2-Year 5.152E-02 5-Year 0.183 5-Year 5.550E-02 10-Year 0.249 10-Year 6.858E-02 25-Year 0.347 25-Year 0.191 50-Year 0.442 50-Year 0.224 100-Year 0.525 100-Year 0.306 200-Year 0.710 200-Year 0.369 ** Record too Short to Compute Peak Discharge for These Recurrence Intervals **** Flow Duration Performance **** Excursion at Predeveloped 50%Q2 (Must be Less Than or Equal to 0%): -71.5% PASS Maximum Excursion from 50%Q2 to Q2 (Must be Less Than or Equal to 0%): -71.5% PASS Maximum Excursion from Q2 to Q50 (Must be less than 10%): -35.3% PASS Percent Excursion from Q2 to Q50 (Must be less than 50%): 0.0% PASS ------------------------------------------------------------------------------------------------- MEETS ALL FLOW DURATION DESIGN CRITERIA: PASS ------------------------------------------------------------------------------------------------- stageareastorage Table for MGS Flood of Btm (cfs) Through Facility Infil. ft) (ac Infiltration Rate =0in/hr (ac)Storage Area Surface Storage (CF) Cumulative Total (CF) Gravel in Volume gravel of LF) per area section(SF Cross in (CF) 740) Volume Chambers (SC Total of area Facility ƩƚǞ LF) ƦĻƩ per feet Chambers (SF sectional Cross Detention Volume for (CF) Chamber Single School (ft) wƚǞЋЉ/ŷğƒĬĻƩƭ High Spreadsheet ƦĻƩ Height System18,368cubic in Table /ŷğƒĬĻƩƭ 00.0000.000.0000.00000.0000000.0000000.000000100.0000010.0830.000.0004.882812810.1938320.0064610.000000100.0838443.30528120.1670.000.0009.755635630.1938320.0129220.000000100.1678443.40556330.2500.000 .00014.638448440.1938320.0193830.000000100.2508443.50584440.3330.000.00019.50112611260.1938320.0258440.000000100.3338443.605112650.4170.000.00024.38140714070.1938320.0323050.000000100.4178443.7051407 60.5000.000.00029.25168916890.1938320.0387660.000000100.5008443.805168970.5832.213.7353030.40175522850.1938320.0524650.000000100.5838443.905228580.6674.417.44105831.56182228810.1938320.0661310.000000 100.6678444.005288190.7506.5811.10157932.78189234720.1938320.0796980.000000100.7508444.1053472 ƚŅ 100.8338.7414.74209834.01196440610.1938320.0932330.000000100.8338444.2054061110.91710.8718.33260935.30203846470.1938320.1066690.000000100.9178444.3054647121.00012.9721.87311336.63211552280.1938320.12 00080.000000101.0008444.4055228131.08315.0425.36361038.01219558040.1938320.1332480.000000101.0838444.5055804141.16717.0828.80409939.45227863770.1938320.1463900.000000101.1678444.6056377151.25019.0932 .19458240.94236369450.1938320.1594330.000000101.2508444.7056945161.33321.0635.51505442.49245375070.1938320.1723460.000000101.3338444.8057507171.41723.0038.78552044.09254680660.1938320.1851600.0000001 01.4178444.9058066181.50024.8941.97597445.78264386170.1938320.1978100.000000101.5008445.0058617191.58326.7445.09641847.54274491620.1938320.2103300.000000101.5838445.1059162201.66728.5448.12685049.382 85197000.1938320.2226860.000000101.6678445.2059700211.75030.2951.07727051.302962102310.1938320.2348780.000000101.7508445.30510231221.83331.9953.94767853.313078107550.1938320.2469060.000000101.8338445 .40510755231.91733.6456.72807455.403198112720.1938320.2587710.000000101.9178445.50511272242.00035.2259.39845357.613326117790.1938320.2704060.000000102.0008445.60511779252.08336.7461.95881859.92346012 2770.1938320.2818450.000000102.0838445.70512277262.16738.1864.38916362.373601127640.1938320.2930220.000000102.1678445.80512764272.25039.5466.67949064.953750132390.1938320.3039370.000000102.2508445.90 513239282.33340.8068.80979267.703909137010.1938320.3145240.000000102.3338446.00513701292.41741.9870.791007570.594075141500.1938320.3248500.000000102.4178446.10514150302.50043.0672.611033473.644252145 860.1938320.3348470.000000102.5008446.20514586312.58344.0174.211056276.924441150030.1938320.3444200.000000102.5838446.30515003322.66744.8175.561075480.444644153980.1938320.3535010.000000102.6678446.4 0515398332.75045.4176.571089884.314867157660.1938320.3619270.000000102.7508446.50515766342.83345.6977.041096688.715121160870.1938320.3693050.000000102.8338446.60516087352.91745.8577.311100493.3153871 63910.1938320.3762900.000000102.9178446.70516391363.00045.9077.401101698.105664166800.1938320.3829140.000000103.0008446.80516680373.08345.9077.4011016102.985945169610.1938320.3893750.000000103.083844 6.90516961383.16745.9077.4011016107.856227172430.1938320.3958370.000000103.1678447.00517243393.25045.9077.4011016112.736508175240.1938320.4022980.000000103.2508447.10517524403.33345.9077.4011016117.6 06790178060.1938320.4087590.000000103.3338447.20517806413.41745.9077.4011016122.487071180870.1938320.4152200.000000103.4178447.30518087423.50045.9077.4011016127.357352183680.1938320.4216810.000000103 .5008447.40518368433.58345.9077.4011016132.237634186500.1938320.4281420.000000103.5838447.50518650443.66745.9077.4011016137.107915189310.1938320.4346030.000000103.6678447.60518931453.75045.9077.40110 16141.988197192130.1938320.4410640.000000103.7508447.70519213463.83345.9077.4011016146.858478194940.1938320.4475250.000000103.8338447.80519494473.91745.9077.4011016151.738760197760.1938320.4539860.00 0000103.9178447.90519776484.00045.9077.4011016156.609041200570.1938320.4604470.000000104.0008448.00520057 Woodway Volume (inches)Stage ƓǒƒĬĻƩ Storage Height Storage ƚƷğƌ Stage EdmondsStage Bottom Width of Gravel Basin58.50ftBottom Length of Gravel Basin144.33ftGravel Depth Beneath Chambers6inchesGravel Above Chambers6inchesVoid Space of Gravel40%Number of rows of Chambers12rowsChamber Length7.12feetTotal Length of Chambers142.33feet Total Stage Storage Table: MGS FLOOD PROJECT REPORT FLOW CONTROL TENNIS COURT BASIN (STORMTECH) Program Version: MGSFlood 4.46 Program License Number: 201410003 Project Simulation Performed on: 02/08/2018 1:11 PM Report Generation Date: 02/08/2018 1:18 PM Input File Name: Tennis Court Basin STORMTECH Detention-FINAL.fld Project Name: Edmonds Woodway HS Analysis Title: Flow Control Comments: tennis court basin - StormTech PRECIPITATION INPUT Computational Time Step (Minutes): 60 Extended Precipitation Time Series Selected Climatic Region Number: 14 Full Period of Record Available used for Routing Precipitation Station : 96003605 Puget East 36 in_5min 10/01/1939-10/01/2097 Evaporation Station : 961036 Puget East 36 in MAP Evaporation Scale Factor : 0.750 HSPF Parameter Region Number: 1 HSPF Parameter Region Name : USGS Default ********** Default HSPF Parameters Used (Not Modified by User) *************** ********************** WATERSHED DEFINITION *********************** Predevelopment/Post Development Tributary Area Summary Predeveloped Post Developed Total Subbasin Area (acres) 0.992 0.992 Area of Links that Include Precip/Evap (acres) 0.000 0.000 Total (acres) 0.992 0.992 ----------------------SCENARIO: PREDEVELOPED Number of Subbasins: 1 ---------- Subbasin : Subbasin 1 ---------- -------Area (Acres) -------- Till Forest 0.927 Till Grass 0.065 ---------------------------------------------- Subbasin Total 0.992 ----------------------SCENARIO: POSTDEVELOPED Number of Subbasins: 1 ---------- Subbasin : Tennis Court Basin ---------- -------Area (Acres) -------- Till Grass 0.276 Impervious 0.716 ---------------------------------------------- Subbasin Total 0.992 ************************* LINK DATA ******************************* ----------------------SCENARIO: PREDEVELOPED Number of Links: 0 ************************* LINK DATA ******************************* ----------------------SCENARIO: POSTDEVELOPED Number of Links: 1 ------------------------------------------ Link Name: Detention Link Type: Structure Downstream Link: None User Specified Elevation Volume Table Used Elevation (ft) Pond Volume (cu-ft) 100.00 0. 100.08 281. 100.17 563. 100.25 844. 100.33 1126. 100.42 1407. 100.50 1689. 100.58 2285. 100.67 2881. 100.75 3472. 100.83 4061. 100.92 4647. 101.00 5228. 101.08 5804. 101.17 6377. 101.25 6945. 101.33 7507. 101.42 8066. 101.50 8617. 101.58 9162. 101.67 9700. 101.75 10231. 101.83 10755. 101.92 11272. 102.00 11779. 102.08 12277. 102.17 12764. 102.25 13239. 102.33 13701. 102.42 14150. 102.50 14586. 102.58 15003. 102.67 15398. 102.75 15766. 102.83 16087. 102.92 16391. 103.00 16680. 103.08 16961. 103.17 17243. 103.25 17524. 103.33 17806. 103.42 18087. 103.50 18368. 103.58 18650. 103.67 18931. 103.75 19213. 103.83 19494. 103.92 19776. 104.00 20057. Constant Infiltration Option Used Infiltration Rate (in/hr): 0.00 Riser Geometry Riser Structure Type : Circular Riser Diameter (in) : 12.00 Common Length (ft) : 0.000 Riser Crest Elevation : 103.50 ft Hydraulic Structure Geometry Number of Devices: 2 ---Device Number 1 --- Device Type : Circular Orifice Control Elevation (ft) : 100.00 Diameter (in) : 0.50 Orientation : Horizontal Elbow : No --- Device Number 2 --- Device Type : Vertical Rectangular Orifice Control Elevation (ft) : 102.00 Length (in) : 0.25 Height (in) : 18.00 Orientation : Vertical Elbow : No **********************FLOOD FREQUENCY AND DURATION STATISTICS******************* ----------------------SCENARIO: PREDEVELOPED Number of Subbasins: 1 Number of Links: 0 ----------------------SCENARIO: POSTDEVELOPED Number of Subbasins: 1 Number of Links: 1 ********** Subbasin: Tennis Court Basin ********** Flood Frequency Data(cfs) (Recurrence Interval Computed Using Gringorten Plotting Position) Tr (yrs) Flood Peak (cfs) ====================================== 2-Year 0.206 5-Year 0.259 10-Year 0.309 25-Year 0.359 50-Year 0.414 100-Year 0.472 200-Year 0.526 ********** Link: Detention ********** Link Inflow Frequency Stats Flood Frequency Data(cfs) (Recurrence Interval Computed Using Gringorten Plotting Position) Tr (yrs) Flood Peak (cfs) ====================================== 2-Year 0.206 5-Year 0.259 10-Year 0.309 25-Year 0.359 50-Year 0.414 100-Year 0.472 200-Year 0.526 ********** Link: Detention ********** Link WSEL Stats WSEL Frequency Data(ft) (Recurrence Interval Computed Using Gringorten Plotting Position) Tr (yrs) WSEL Peak (ft) ====================================== 1.05-Year 100.897 1.11-Year 100.974 1.25-Year 101.091 2.00-Year 101.439 3.33-Year 101.691 5-Year 101.995 10-Year 102.442 25-Year 102.576 50-Year 102.689 100-Year 102.741 ***********Compliance Point Results ************* Scenario Predeveloped Compliance Subbasin: Subbasin 1 Scenario Postdeveloped Compliance Link: Detention *** Point of Compliance Flow Frequency Data *** Recurrence Interval Computed Using Gringorten Plotting Position Predevelopment Runoff Postdevelopment Runoff Tr (Years) Discharge (cfs) Tr (Years) Discharge (cfs) ---------------------------------------------------------------------------------------------------------------------- 2-Year 1.733E-02 2-Year 8.002E-03 5-Year 3.131E-02 5-Year 9.422E-03 10-Year 4.249E-02 10-Year 2.676E-02 25-Year 5.840E-02 25-Year 3.501E-02 50-Year 6.688E-02 50-Year 4.276E-02 100-Year 8.666E-02 100-Year 4.648E-02 200-Year 0.118 200-Year 5.246E-02 ** Record too Short to Compute Peak Discharge for These Recurrence Intervals **** Flow Duration Performance **** Excursion at Predeveloped 50%Q2 (Must be Less Than or Equal to 0%): -7.3% PASS Maximum Excursion from 50%Q2 to Q2 (Must be Less Than or Equal to 0%): -7.3% PASS Maximum Excursion from Q2 to Q50 (Must be less than 10%): -38.6% PASS Percent Excursion from Q2 to Q50 (Must be less than 50%): 0.0% PASS ------------------------------------------------------------------------------------------------- MEETS ALL FLOW DURATION DESIGN CRITERIA: PASS ------------------------------------------------------------------------------------------------- 32%88% % Full ЋΉЊЏΉЋЉЊБ ΛĭŅƭΜ Љ͵БАЎЋ͵БЌЎ Qtrib, 100-year (MGSFlood, 15 min) 21%51% % Full ΛĭŅƭΜ Љ͵ЎЏЊЊ͵ЏЎЏ Qtrib, 25-year (MGSFlood, 15 min) Љ͵ЋАЏЋ͵АБЏ ΛğĭƩĻƭΜ Tributary Pervious Area Љ͵АЊЏЊ͵ЌЏЋ ΛğĭƩĻƭΜ Tributary Impervious Area Area Љ͵ВВЋЍ͵ЊЍБ ΛğĭƩĻƭΜ Total Tributary Tributary Basins CźĻƌķ .ğƭźƓ Λ{ĻĻ CźŭǒƩĻ ЎΜ ĻƓƓźƭ /ƚǒƩƷ .ğƭźƓ Λ{ĻĻ CźŭǒƩĻ ЎΜ ΛĭŅƭΜ 2.743.24 Qfull Plan ΛŅƷΉŅƷΜ Љ͵ЉЉЎЉ͵ЉЉА Slope N Љ͵ЉЊЋЉ͵ЉЊЋ Mannings ЊЋЊЋ Size ΛźƓĭŷĻƭΜ Pipe Run {ƷƩǒĭƷǒƩĻ hǒƷƌĻƷ {ƷƚƩƒĻĭŷ hǒƷƌĻƷ CźĻƌķ CƌƚǞ /ƚƓƷƩƚƌ Edmonds Woodway HSConveyance Analysis Spreadsheet MGS FLOOD PROJECT REPORT CONVEYANCE TENNIS COURT BASIN Program Version: MGSFlood 4.46 Program License Number: 201410003 Project Simulation Performed on: 02/02/2018 2:52 PM Report Generation Date: 02/02/2018 2:52 PM Input File Name: tennis courts conveyance.fld Project Name: Edmonds Woodway HS Analysis Title: Conveyance Comments: tennis courts PRECIPITATION INPUT Computational Time Step (Minutes): 15 Extended Precipitation Time Series Selected Climatic Region Number: 14 Full Period of Record Available used for Routing Precipitation Station : 96003605 Puget East 36 in_5min 10/01/1939-10/01/2097 Evaporation Station : 961036 Puget East 36 in MAP Evaporation Scale Factor : 0.750 HSPF Parameter Region Number: 1 HSPF Parameter Region Name : USGS Default ********** Default HSPF Parameters Used (Not Modified by User) *************** ********************** WATERSHED DEFINITION *********************** Predevelopment/Post Development Tributary Area Summary Predeveloped Post Developed Total Subbasin Area (acres) 0.992 0.992 Area of Links that Include Precip/Evap (acres) 0.000 0.000 Total (acres) 0.992 0.992 ----------------------SCENARIO: PREDEVELOPED Number of Subbasins: 1 ---------- Subbasin : Subbasin 1 ---------- -------Area (Acres) -------- Till Grass 0.276 Impervious 0.716 ---------------------------------------------- Subbasin Total 0.992 ----------------------SCENARIO: POSTDEVELOPED Number of Subbasins: 1 ---------- Subbasin : tennis basin ---------- -------Area (Acres) -------- Till Grass 0.276 Impervious 0.716 ---------------------------------------------- Subbasin Total 0.992 ***********Compliance Point Results ************* Scenario Predeveloped Compliance Subbasin: Subbasin 1 Scenario Postdeveloped Compliance Subbasin: tennis basin *** Point of Compliance Flow Frequency Data *** Recurrence Interval Computed Using Gringorten Plotting Position Predevelopment Runoff Postdevelopment Runoff Tr (Years) Discharge (cfs) Tr (Years) Discharge (cfs) ---------------------------------------------------------------------------------------------------------------------- 2-Year 0.281 2-Year 0.281 5-Year 0.360 5-Year 0.360 10-Year 0.432 10-Year 0.432 25-Year 0.561 25-Year 0.561 50-Year 0.729 50-Year 0.729 100-Year 0.875 100-Year 0.875 200-Year 0.920 200-Year 0.920 ** Record too Short to Compute Peak Discharge for These Recurrence Intervals MGS FLOOD PROJECT REPORT CONVEYANCE FIELD BASIN Program Version: MGSFlood 4.46 Program License Number: 201410003 Project Simulation Performed on: 02/08/2018 2:21 PM Report Generation Date: 02/08/2018 2:21 PM Input File Name: Field Conveyance.fld Project Name: Edmonds Woodway HS Analysis Title: Conveyance Comments: Field control structure PRECIPITATION INPUT Computational Time Step (Minutes): 15 Extended Precipitation Time Series Selected Climatic Region Number: 14 Full Period of Record Available used for Routing Precipitation Station : 96003605 Puget East 36 in_5min 10/01/1939-10/01/2097 Evaporation Station : 961036 Puget East 36 in MAP Evaporation Scale Factor : 0.750 HSPF Parameter Region Number: 1 HSPF Parameter Region Name : USGS Default ********** Default HSPF Parameters Used (Not Modified by User) *************** ********************** WATERSHED DEFINITION *********************** Predevelopment/Post Development Tributary Area Summary Predeveloped Post Developed Total Subbasin Area (acres) 4.148 4.148 Area of Links that Include Precip/Evap (acres) 0.000 0.000 Total (acres) 4.148 4.148 ----------------------SCENARIO: PREDEVELOPED Number of Subbasins: 1 ---------- Subbasin : Subbasin 1 ---------- -------Area (Acres) -------- Till Grass 2.786 Impervious 1.362 ---------------------------------------------- Subbasin Total 4.148 ----------------------SCENARIO: POSTDEVELOPED Number of Subbasins: 1 ---------- Subbasin : Field Basin ---------- -------Area (Acres) -------- Till Grass 2.786 Impervious 1.362 ---------------------------------------------- Subbasin Total 4.148 ***********Compliance Point Results ************* Scenario Predeveloped Compliance Subbasin: Subbasin 1 Scenario Postdeveloped Compliance Subbasin: Field Basin *** Point of Compliance Flow Frequency Data *** Recurrence Interval Computed Using Gringorten Plotting Position Predevelopment Runoff Postdevelopment Runoff Tr (Years) Discharge (cfs) Tr (Years) Discharge (cfs) ---------------------------------------------------------------------------------------------------------------------- 2-Year 0.676 2-Year 0.676 5-Year 0.987 5-Year 0.987 10-Year 1.255 10-Year 1.255 25-Year 1.656 25-Year 1.656 50-Year 2.443 50-Year 2.443 100-Year 2.835 100-Year 2.835 200-Year 2.857 200-Year 2.857 ** Record too Short to Compute Peak Discharge for These Recurrence Intervals Sediment Facility Sizing Calculations Per Volume II of 2014 DOE Manual Project Name:Edmonds Woodway HS Required Minimum Storage Volume of Sediment Tank: SA (sf) = 2 x Q (cfs) / 0.00096 Where:Q = 2-year developed flow rate from MGS Flood with 15-minute time steps SA =Required surface area at top of riser Calculation:multiplier =2 Q =1.163cfs Divider =0.00096gpm SA =2422.9square feet Equivalent Sediment Trap Volume: To determine the minimum sediment tank volume, an equivalent sediment trap was sized based upon the required surface area. Length of Top Surface Area =100feet Width of Top Surface Area =25feet Surface Area Provided =2500square feet Side Slope =0(H:1V) Total Depth of Sediment Trap =3.5feet Bottom Length of Sediment Trap =100feet Bottom Width of Sediment Trap =25feet Total pond Volume = 8,750cubic feet 65,450gallons MGS FLOOD PROJECT REPORT TESC SEDIMENT SIZING Program Version: MGSFlood 4.46 Program License Number: 201410003 Project Simulation Performed on: 01/19/2018 12:19 PM Report Generation Date: 01/19/2018 12:20 PM Input File Name: TESC full site.fld Project Name: Edmonds Woodway HS Analysis Title: TESC Comments: full site PRECIPITATION INPUT Computational Time Step (Minutes): 15 Extended Precipitation Time Series Selected Climatic Region Number: 15 Full Period of Record Available used for Routing Precipitation Station : 96004005 Puget East 40 in_5min 10/01/1939-10/01/2097 Evaporation Station : 961040 Puget East 40 in MAP Evaporation Scale Factor : 0.750 HSPF Parameter Region Number: 1 HSPF Parameter Region Name : USGS Default ********** Default HSPF Parameters Used (Not Modified by User) *************** ********************** WATERSHED DEFINITION *********************** Predevelopment/Post Development Tributary Area Summary Predeveloped Post Developed Total Subbasin Area (acres) 5.043 5.043 Area of Links that Include Precip/Evap (acres) 0.000 0.000 Total (acres) 5.043 5.043 ----------------------SCENARIO: PREDEVELOPED Number of Subbasins: 1 ---------- Subbasin : Subbasin 1 ---------- -------Area (Acres) -------- Till Forest 2.540 Till Grass 2.503 ---------------------------------------------- Subbasin Total 5.043 ----------------------SCENARIO: POSTDEVELOPED Number of Subbasins: 1 ---------- Subbasin : Subbasin 1 ---------- -------Area (Acres) -------- Till Grass 2.503 Impervious 2.540 ---------------------------------------------- Subbasin Total 5.043 ***********Compliance Point Results ************* Scenario Predeveloped Compliance Subbasin: Subbasin 1 Scenario Postdeveloped Compliance Subbasin: Subbasin 1 *** Point of Compliance Flow Frequency Data *** Recurrence Interval Computed Using Gringorten Plotting Position Predevelopment Runoff Postdevelopment Runoff Tr (Years) Discharge (cfs) Tr (Years) Discharge (cfs) ---------------------------------------------------------------------------------------------------------------------- 2-Year 0.264 2-Year 1.163 5-Year 0.478 5-Year 1.526 10-Year 0.664 10-Year 1.869 25-Year 1.015 25-Year 2.534 50-Year 1.280 50-Year 3.220 100-Year 1.488 100-Year 3.923 200-Year 1.604 200-Year 3.998 ** Record too Short to Compute Peak Discharge for These Recurrence Intervals APPENDIX C Construction Stormwater Pollution Prevention Plan (SWPPP) Narrative Edmonds Woodway Synthetic Turf Conversion Construction SWPPP Narrative February 16, 2018 E DMONDS W OODWAY H IGH S CHOOL S YNTHETIC T URF C ONVERSION P ROJECT C ONSTRUCTION SWPPP N ARRATIVE F EBRUARY 16, 2018 The following Construction Storm Water Pollution Prevention Plan (SWPPP) narrative is for Edmonds-Woodway Synthetic Tuff Conversion Project at the Edmonds-Woodway High School th Campus. The site is located at 7600 212 Street SW in Edmonds, Washington. The narrative supplements the Temporary Erosion and Sediment Control (TESC) plan. This narrative and the drawings address the requirements of Volume II of the Department of Ecology (DOE) 2012 Stormwater Management Manual for Western Washington (SMMWW), amended in 2014. Refer to the TESC plans (Sheets C0.3) and TESC details (Sheets C0.4) for more information regarding any erosion or sedimentation control measures involved in this project. 1. C ONSTRUCTION S TORMWATER P OLLUTION P REVENTION E LEMENTS 1) Mark Clearing Limits: Clearing limits will be delineated on the TESC and Site Demolition plan. The actual limits of clearing will likely be smaller than the limit of work, but this identifies the maximum extent of the clearing limits. Areas impacted and not anticipated to be covered with final measures shall be stabilized using approved permanent TESC methods. 2) Establish Construction Access: Construction access will be provided at the existing eastern access driveway, with temporary quarry spall construction entrance (BMP C105) as necessary. The Contractor shall provide wheel wash if necessary. 3) Control Flow Rates: Stormwater flow control during construction will be mitigated by routing runoff to a 67,000-gallon temporary sediment storage facility. Refer to the Sediment Tank Sizing calculations and the associated MGS Flood output included within Appendix B of Permanent flow control facilities and a StormTech chamber detention system. 4) Install Sediment Controls: DOE approved BMPs for sediment controls are shown on the TESC plan. Sediment will be controlled using silt fence (BMP C233) and storm drain inlet protection (BMP C220). 5) Stabilize Soils: It is possible that some of the earthwork and grading may occur in wet weather conditions. The site must be stabilized and no soils will be allowed to remain stth unstabilized for more than two days between October 1 and April 30. From May 1 through September 30, install cover measures to protect disturbed areas that will remain unworked for seven days or more. By October 8, seed all areas that will remain unworked from October 1 through April 30. Mulch all seeded areas. Exposed slopes will be protected by DOE-approved coverage methods. BMPs including, but not limited to: C101, Preserving Natural Vegetation; C121, Mulching; C123, Plastic Covering; C130, Surface Roughening; C140, Dust Control; and T5.13 Post Construction Soil Amendment will be used to stabilize on-site soils during construction. Page 1 Edmonds Woodway Synthetic Turf Conversion Construction SWPPP Narrative February 16, 2018 6) Protect Slopes: The DOE-approved BMPs for slope protection will be utilized during construction. Concentrated discharges shall not be allowed to flow over the top of steep slopes. BMPs including, but not limited to C101, Preserving Natural Vegetation; C121, Mulching; C123, Plastic Covering; C130, Surface Roughening; C140, Dust Control; C208, Triangular Silt Dike; C207, Check Dams; and C233, Silt Fence are to be utilized to protect slopes during construction. 7) Protect Drain Inlets: Drainage structures in areas where no work occurs will remain and will be protected; discharge points to the public storm drain main line will also be protected. To prevent discharge of turbid water downstream, all existing catch basins located within the disturbance area and outside of the disturbance area within approximately 300 feet downstream of the site will be protected with storm drain inlet protection (BMP C220). The Contractor shall remove inlet protection at the end of the project without releasing captured sediment into the storm system. 8) Stabilize Channels and Outlets: DOE-approved BMPs for channel stabilization will be utilized during construction, including, but not limited to: C200, Interceptor Dike and Swale; and C207, Check Dams. 9) Control Pollutants: Temporary protection of the disturbed soils provides the first level of protection for pollution control, and perimeter measures downstream will mitigate the remaining pollutants. The temporary protection of disturbed soils may be mitigated with a temporary sump and pump facility to provide the second level of interception of pollutants. This collection system filters sediments prior to the pump system. The pump system will then route stormwater via force mains into the temporary sediment settling facility. Construction debris will be removed from the site. The Contractor will be responsible for managing their construction equipment per DOE-approved BMPs. If a truck wheel wash is required, truck wheel wash water and concrete truck washout water shall be collected and discharged to the public sanitary sewer (SS) system. To apply for and obtain a SS release, contact the local sewer purveyors for authorization. 10) Control De-Watering: The majority of the earthwork on the project will be constructed during the dry season, therefore it is not anticipated that groundwater will be encountered in the excavations for this project. In the event that perched groundwater is encountered during any wet season construction, the Contractor shall route it to the sediment settling facility by pumping it out of the excavation. 11) Maintain BMPs: DOE-approved standard BMP maintenance will be required in accordance with the City of Edmonds standard TESC plan notes (Sheet C0.5). 12) Manage the Project: All phases of construction will be managed by the Contractor. The site must be stabilized and no soils will be allowed to remain exposed and unworked for stth more than two days between October 1 and April 30 and for more than seven days stth between May 1 and September 30. The Contractor will provide maintenance and monitoring of TESC BMPs. Work of all contractors will be coordinated to minimize the duration of disturbance on the site. The best management practices shown on the TESC plan are minimum requirements. Failure to maintain SWPPP measures in accordance with adopted standards may result in the work being performed at the City the costs assessed as a lien against the property where such facilities are located. 13) Protect Low-Impact Development BMPs: The project proposes permeable pavement surfaces as a Low-Impact Development BMP. Erosion and introduction of sediment from Page 2 Edmonds Woodway Synthetic Turf Conversion Construction SWPPP Narrative February 16, 2018 surrounding land uses can clog void spaces in the subgrade, base material, and permeable surface. This will be controlled by preventing muddy construction equipment from driving on the base material, by directing sediment-laden runoff to the settling tank via interceptor swales, and by mulching, planting, and stabilizing exposed soil as soon as possible. Signage identifying the permeable pavement installations will also be provided. 2. P ROJECT D ESCRIPTION The proposed project includes the conversion of the existing natural grass baseball field to a multi-purpose synthetic turf field, and the installation of four new tennis courts, paved walkways, lighting improvements, and track facilities. The project proposes 92,190 square feet (2.12 acres) of new plus replaced hard surface. The total project disturbance is 221,037 square feet (5.07 acres). Flow control will be addressed with an underdrain system beneath the proposed multi-purpose field, and a below-grade StormTech system beneath the proposed tennis courts. A flow restrictor will be located on the discharge point from the underdrain system, as well as the StormTech chambers. Water quality for the synthetic field surface will be provided by a StormFilter cartridge system containing PhosphoSorb media. ter site plan for more information. Estimated earthwork quantities for the project include approximately 14,500 cubic yards of cut and fill, 1,500 cubic yards of grubbing removal, 300 cubic yards of asphalt paving, 400 cubic yards of pervious paving and base. There will be approximately 6,500 cubic yards of import aggregate for the project. These quantities are estimates only and intended for municipal permitting. These quantities shall not be used by the Contractor as a basis for any contractual information. The Contractor shall prepare their own earthwork quantities based upon the information provided in the contract documents. 3. E XISTING S ITE C ONDITIONS The Edmonds Woodway High School campus currently consists of school buildings encompassing the northeast portion of the site with the parking lots to the west and south. An existing softball field is in the northwest corner of the parcel with the track/football field south of this field. In the southwest portion of the school is the project area, consisting of an existing baseball field with compacted dirt infield and natural grass outfield and five tennis courts. The existing topography of the baseball field slopes towards the south at a slope of around 2-4%. There is a slope along the western boundary of the existing baseball field, rising 8 feet to the adjacent field. To the west of the third base line, there is a rockery and steeper grade rise to the track area above. Walkways and existing tennis court to northwest are relatively flat. According to City of Edmonds mapping, the school site is within the Hall Creek Drainage Basin. Stormwater from the site generally sheet flows to several catch basins, before exiting via two th stormwater discharges from the project area that are tributary to the 12-inch storm main in 216 Street SW. The system continues east, discharging into Hall Creek approximately ½-mile downstream of the site. Page 3 Edmonds Woodway Synthetic Turf Conversion Construction SWPPP Narrative February 16, 2018 4. A DJACENT A REAS ththth The school property is bounded by 216 Street SW to the south, 76 Avenue W to the east, 212 Street SW to the north, and residential complexes to the west. Vehicular access to the site is from ththth the north off 212 Street SW, from the west off 76 Avenue W, and from the south off 216 Street SW. 5. C RITICAL A REAS Based on City of Edmonds mapping, there are no environmentally critical areas within the project area. There are some erosion hazard areas (15%-40% slopes) along the east end of the site. 6. S OILS Based upon the Natural Resources Conservation Service Web Soil Survey, the site soils within the project site are Alderwood-Urban Land Complex with 2%-8% slopes. A geotechnical report was prepared by Associated Earth Sciences Inc., dated May 9, 2107. Their subsurface exploration observed existing fill up to 14 feet thick with underlying Vashon Lodgement Till, consisting of dense to very dense sand with silt and gravel. 7. P OTENTIAL E ROSION P ROBLEM A REAS As mentioned, the site contains several portions that are considered erosion hazard areas, and erosion hazard is expected to be moderate. Per the proposed contract documents, the contractor is to provide protection for soils to limit the exposure to erosion. The limitation of disturbance, adequate cover practices, seasonal work limitation, and runoff control are the most effective methods for reduction of turbidity in stormwater runoff. Any runoff that occurs will be directed to the temporary sump via a temporary interceptor swale, and then pumped to the proposed 67,000- gallon sediment tank. Areas that have not been permanently stabilized will be addressed using DOE-approved BMPs, per the construction documents. 8. C ONSTRUCTION P HASING The contractor is responsible for coordinating work of all subcontractors to keep the duration of site disturbance limited to the maximum extent possible. 9. C ONSTRUCTION S CHEDULE Construction of this Project is expected to begin in Summer of 2018 and be completed by Fall of 2018. stth Earthwork activities are not expected to take place in the wet season, October 1 to April 30. Should any wet weather conditions occur during construction, the contractor shall implement the de-watering procedures outlined in this SWPPP and applicable BMPs including, but not limited to C123, Plastic Covering; C121, Mulching; C122, Nets and Blankets; C126, Polyacrylamide for Soil Erosion Protection; C130, Surface Roughening. 10. F INANCIAL/O WNERSHIP R ESPONSIBILITIES This property is owned and operated by the Edmonds School District. The accepted low bidder on the project will be responsible for posting a performance and payment bond with the Edmonds School District, and thus will be the responsible party for any liability associated with erosion and Page 4 Edmonds Woodway Synthetic Turf Conversion Construction SWPPP Narrative February 16, 2018 sedimentation impact. 11. E NGINEERING C ALCULATIONS A copy of any calculations performed during design of the project and relevant storm drainage Stormwater Site Plan. Page 5 APPENDIX D Operations and Maintenance Guidelines Edmonds Woodway High School Athletic Fields Renovation Phase 1 Operations & Maintenance Manual February 16, 2018 Prepared by: LPD Engineering, PLLC st 1932 1 Avenue, Suite 201 Seattle, WA 98101 206.725.1211 Operations & Maintenance Manual Project Overview This Operations and Maintenance Manual is for the Edmonds-Woodway High School Athletic th Fields Renovation located at 7600 212 Street SW in Edmonds, Washington. The proposed project includes replacing the existing natural grass baseball field with a synthetic turf multi-purpose field, as well as the installation of four new tennis courts, paved walkways, lighting improvements, roofed batting cages, and track facilities. Stormwater System Overview The proposed conditions include an underdrain system located underneath the synthetic turf multi- use field. The surfaces are permeable and allow vertical drainage. Rainfall landing upon these surfaces will percolate vertically through the surface materials and into the permeable gravel base materials, and will be collected by the underdrain system, consisting of 4-inch perforated lateral drain lines. Runoff will be conveyed by a collector into a flow control structure at the southwest corner of the field, which will back up flows, utilizing the storage provided by the permeable base course as well as the underdrain system. The outflow from the control structure will be conveyed through a StormFilter cartridge structure for water quality treatment. The outlet from the th StormFilter manhole will connect to the existing storm system in 216 Street SW. A StormTech chamber system is proposed to mitigate the flows from the proposed tennis courts and surrounding walkways. The chamber system will be located under the southeast corner of the field, beneath the proposed underdrain system. From there, stormwater will flow east, connecting with the existing storm line in the parking lot drive aisle and continue the existing downstream drainage path. Refer to Figure A, and also the Drainage Plan Sheets F-1.3, included with this manual for a layout of the drainage system. Also refer to Sheets F-2.2, F-2.4, and F-2.5 for details of the flow control structures, StormFilter water quality structure, and the StormTech detention system. Field Underdrain System Maintenance Rainfall landing upon the synthetic turf and pervious concrete surfaces will percolate through the surface into the top course gravel layer, and then continue down into the base layers before it reaches the underdrain system. The layers of permeable aggregate material will provide filtration of the stormwater before it reaches the underdrain pipe network. Therefore little to no sedimentation is expected within the subsurface drainage system. The field drainage system will only handle rainfall that lands on the field; no upstream flows are expected to run-on to these underdrained surfaces. Maintenance (cleaning) will be done if necessary during the replacement of the synthetic turf material. The synthetic turf fields generally have an expected life cycle of approximately 8-10 years. Due to the filtration of stormwater percolating vertically through the system, the maintenance interval for the field aggregate base layers and the pipe network is expected to be greater than the life cycle of the synthetic turf field surface. Operations & Maintenance Manual Edmonds Woodway High School LPD Engineering, PLLC Page 1 February 16, 2018 In the event that one of the perforated lateral drain lines becomes plugged, flows will migrate down-gradient and be collected by the adjacent perforated lateral drain line within the system. Only in the highly unlikely event of a major failure of the underdrain system would there be a need to partially remove and replace the field surface to access the drainage system for maintenance and cleaning/repair. Flow Control Structure Maintenance The flow control structure for the field underdrain system is located within a Type-2 catch basin southwest of the field, outside of the field footprint (CB-#3 on Sheet F-1.3). Refer to the attached general maintenance guidelines from the 2014 Department of Ecology (DOE) Stormwater Management Manual for Western Washington for the flow control structure. As noted above, due to the design of the field system there is expected to be little to no sediment that could reach the flow control structure. In addition, the catch basin will be equipped with a solid locking lid, thus preventing debris from entering it. The proposed Type-2 catch basin with diameter of 4812-inch riser does not take up a significant volume of the interior space within the catch basin; the flow control riser shall have 2- foot minimum clearance from the access ladder steps. There is a shear gate proposed on the control structure, as is typical, allowing access to the downstream drain line from within the catch basin. The control structure riser pipe will be easily accessible from the surface when the solid lid is removed from the Type-2 catch basin. With the cover removed, maintenance personnel will be able to look straight down into the riser pipe to confirm it is functioning normally. Therefore there should typically be no need to physically enter the structure, as everything will be visible from the top. In addition the flow restrictor can be removed from the outlet pipe as necessary, by removing the support straps and sliding the tee structure out of the outlet pipe. In the event that sediment accumulates in the catch basin due to unforeseen conditions, vactor truck cleaning of the catch basin with the use of a small diameter hose can be performed to remove any sediment within the bottom of the structure. This will not require maintenance staff to enter the structure. StormFilter Maintenance A StormFilter media filtration system for water quality treatment will be installed at the multi-use field. The StormFilter structure will be located southwest of the field within a 48-inch diameter manhole with 3 PhosphoSorb media StormFilter cartridges. StormFilter maintenance inspection is recommended once per year at a minimum, typically before the start of the rainy season. An inspection during a rain event would also be beneficial to observe how the water is flowing through the cartridges. Inspection is to be completed by someone familiar with the StormFilter treatment unit. The manufacturer suggests the replacement interval will be about 1-3 years, depending on the pollutant concentrations. When cartridge replacement is needed, the manufacturer has a list of certified maintenance providers who are qualified to do the work they can be hired to do periodic inspections as well. Refer to the attached maintenance requirements from Table V-4.5.2(15) from the 2014 Department of Ecology (DOE) Stormwater Management Manual for the StormFilter structure. Operations & Maintenance Manual Edmonds Woodway High School LPD Engineering, PLLC Page 2 February 16, 2018 Permeable Pavement Maintenance Permeable pavement will be prevalent throughout the site, including various walkways around the field. Refer to the attached maintenance requirements from Table 4.5.2(22) from the 2014 DOE Stormwater Management Manual for permeable pavement surfaces. StormTech Detention System Maintenance The Storm Tech Detention Chamber is located beneath the field surface and its underdrain system, in the southeast corner. The isolator row will be the northernmost row, which can be accessed by a Nyloplast drain basin at the northeast corner of the facility. Refer to the StormTech inspection and maintenance procedures, as outlined by ADS pipe (manufacturer of StormTech), included with this manual. Catch Basins/Conveyance Pipes Maintenance Refer to the attached maintenance guidelines from Volume V from the 2014 DOE Stormwater Management Manual for Western Washington for catch basins and conveyance pipes. Maintenance Responsibility In order to limit the contribution of the pollutants to the storm drainage system, there shall be no use of disinfecting chemicals, cleaning products or other chemical agents used on the synthetic turf surface. Equipment used for field maintenance shall be kept in good working order, to limit leaks or spills of contaminates from machinery. Also pet/animal usage of the field should be restricted to limit any potential for any animal wastes from damaging the synthetic turf field surface and potentially polluting stormwater runoff. This Operations and Maintenance Manual shall be kept in the Edmonds-Woodway High School main office, and a copy shall be kept at the Edmonds School District office. This manual must be made readily available for inspection by City of Edmonds personnel. Edmonds School District is the responsible organization for maintenance of the on-site storm systems. The Edmonds School District department of maintenance and operations can be contacted at (425) 431-7244. The maintenance activity log shall be kept up date with the most current O&M actions by the School District, and shall be made available for inspection by the City upon request. Operations & Maintenance Manual Edmonds Woodway High School LPD Engineering, PLLC Page 3 February 16, 2018 Attachments: Exhibit A - Stormwater Facilities Site Map Drainage Plan Sheet F-1.3; Drainage Details Sheet F-2.2; Detention Details Sheet F-2.4; Operation and Maintenance Guidelines from the 2014 Department of Ecology Stormwater Management Manual for Western Washington Inspection and Maintenance procedures for StormTech detention chambers Sample Maintenance Activity Log Operations & Maintenance Manual Edmonds Woodway High School LPD Engineering, PLLC Page 4 February 16, 2018 EXHIBIT A - STORMWATER FACILITIES SITE MAP EDMONDS WOODWAY HIGH SCHOOL No. 4 –Control Structure/Flow Restrictor Maintenance DefectCondition When Maintenance is NeededResults Expected ComponentWhen Maintenance is Performed GeneralTrash and Debris Material exceeds 25% 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 is not 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 plumb).position. Connections to outlet 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 has no structure.holes other than designed holes. Cleanout GateDamaged or MissingCleanout gate is not watertight or is missing. Gate is watertight and works as designed. Gate cannot be moved up and down by one Gate moves up and maintenance person.down easily and is watertight. Chain/rod 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 PlateDamaged or MissingControl device is not working properly due to Plate is in place and missing, out of place, or bent orifice plate.works as designed. ObstructionsAny trash, debris, sediment, or vegetation Plate is free of all blocking the plate.obstructions and works as designed. Overflow PipeObstructions Any trash or debris blocking (or having the Pipe is free of all potential of blocking) the overflow pipe.obstructions and works as designed. ManholeSee “Closed See “Closed Detention Systems” (No. 3).See “Closed Detention Systems” Detention Systems” (No. 3).(No. 3). Catch BasinSee “Catch Basins” (No. 5). See “Catch Basins” See “Catch Basins” (No. 5).(No. 5). Volume V –Runoff Treatment BMPs –December 2014 4-37 No. 5 –Catch Basins Maintenance DefectConditions When Maintenance is NeededResults Expected When ComponentMaintenance is performed GeneralTrash & 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 inletting capacity of the basin by catch 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 lowest pipe. Trash or debris in any inlet or outlet pipe Inlet and outlet pipes free blocking more than 1/3 of its height.of trash or debris. Dead animals or vegetation that could No dead animals or generate odors that could cause complaints vegetation present within or dangerous gases (e.g., methane).the catch 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 lowest pipe. Structure Top slab has holes larger than 2 square Top slab is free of holes Damage to inches or cracks wider than 1/4 inchand cracks. Frame and/or (Intent is to make sure no material is running Top Slab into basin). Frame not sitting flush on top slab,i.e., Frame is sitting flush on separation of more than 3/4 inch of the frame the riser rings or top slab from the top slab. Frame not securely and firmly attached. attached Fractures or Maintenance person judges that structure is Basin replaced or repaired Cracks in unsound.to design standards. Basin Walls/ Bottom Grout fillet has separated or cracked wider Pipe is regrouted and than 1/2 inch and longer than 1 foot at the secure at basin wall. joint of any inlet/outlet pipe or any evidence of soil particles entering catch basin through cracks. Settlement/ If failure of basin has created a safety, Basin replaced or repaired Misalignmentfunction, or design problem. to design standards. Vegetation Vegetation growing across and blocking more No vegetation blocking than 10% of the basin opening.opening to basin. Vegetation growing in inlet/outlet pipe joints No vegetation or root that is more than six inches tall and less than growth present. six inches apart. Contamination See "Detention Ponds" (No. 1).No pollution present. and Pollution Volume V –Runoff Treatment BMPs –December 2014 4-38 No. 5 –Catch Basins Maintenance DefectConditions When Maintenance is NeededResults Expected When ComponentMaintenance is performed Catch Basin Cover Not in Cover is missing or only partially in place. Catch basin cover is CoverPlaceAny open catch basin requires maintenance.closed Locking Mechanism cannot be opened by one Mechanism opens with Mechanism maintenance person with proper tools.Bolts proper tools. Not Workinginto frame have less than 1/2 inch of thread. Cover Difficult One maintenance person cannot remove lid Cover can be removed by to Removeafter applying normal lifting pressure.one maintenance person. (Intent is keep cover from sealing off access to maintenance.) LadderLadder Rungs Ladder is unsafe due to missing rungs, not Ladder meets design Unsafesecurely attached to basin wall, standards and allows misalignment, rust, cracks, or sharp edges.maintenance person safe access. Metal Grates Grate opening Grate with opening wider than 7/8 inch. Grate opening meets (If Applicable)Unsafedesign standards. Trash and Trash and debris that is blocking more than Grate free of trash and Debris20% of grate surface inletting capacity.debris. Damaged or Grate missing or broken member(s) of the Grate is in place and Missing.grate.meets design standards. No. 6 –Debris Barriers (e.g.,Trash Racks) Maintenance DefectCondition When Maintenance is Results Expected When ComponentsNeededMaintenance is Performed GeneralTrash and Trash or debris that is plugging more Barrier cleared to design flow Debristhan 20% of the openings in the barrier.capacity. Metal Damaged/ Bars are bent out of shape more than 3 Bars in place with no bends more Missing inches.than 3/4 inch. Bars. Bars are missing or entire barrier Bars in place according to design. missing. Bars are loose and rust is causing 50% Barrier replaced or repaired to deterioration to any part of barrier.design standards. Barrier firmly attached to pipe Inlet/Outlet Debris barrier missing or not attached to Pipepipe Volume V –Runoff Treatment BMPs –December 2014 4-39 Maintenance Activity Log To be completed by maintenance staff and provided to the City of Edmonds upon request. Property Name/Owner: Site Address: Property Manager/Contact: Phone: Facility Type: Location on Property: Requirement met by Facility (circle all that apply): On-site Stormwater Management Treatment/Water Quality Flow Control Date Reason for Condition Observed Action Taken Initials Inspection/Action (circle one) Complaint or Problem Regular Maintenance Complaint or Problem Regular Maintenance Complaint or Problem Regular Maintenance Complaint or Problem Regular Maintenance Complaint or Problem Regular Maintenance Complaint or Problem Regular Maintenance Complaint or Problem Regular Maintenance APPENDIX E Draft Declaration of Covenant Bgufs!sfdpsejoh!sfuvso!up;! Djuz!Dmfsl! Djuz!pg!Fenpoet! 232!Gjgui!Bwfovf!Opsui! Fenpoet-!XB!:9131! ! ! ! ! ! ! ! Epdvnfou!Ujumf)t*! ! Efdmbsbujpo!pg!Dpwfobou!.!Qsjwbuf!Tupsnxbufs!Gbdjmjuz! ! Sfgfsfodf!Ovncfs)t*!pg!Sfmbufe!Epdvnfout! ! O0B! ! Hsboups)t*!)Mbtu-!Gjstu!boe!Njeemf!Jojujbm*! ! !Edmonds School District ! ! ! 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