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APPROVED STM BLD2022-0439+Storm_Drainage_Report+2.24.2023_10.13.30_AM+3386882Meadowview Estates - Angle Residence RESUB Drainage Report Feb 27 2023 CITY OF EDMONDS DEVELOPMENT SERVICES Prepared for: DEPARTMENT CAST Architecture 115-C North 36`h St BLD2022-0439 Seattle, WA 98103 Contact: Forrest Murphy, LEED BD+C (206) 256-9886 Prepared by: LDC: ICK. 20210 142"d Ave NE Woodinville, WA 98072 (425) 806-1869 COMPLIES WITH APPLICABLE CITY STORM CODE 03/06/2023 Revised February 2023 Job No: C21-164 TABLE OF CONTENTS Section Title 1 Purpose and Site Narrative 1-1 Appendix 1: Project Overview 2 Temporary Erosion and Sediment Control Analysis 2-1 and Design 3 Downstream Analysis Appendix 3: Resource Review 3-1 4 Flow Control Analysis and Design 4-1 Appendix 4: Flow Control Analysis and Design 5 Conveyance Analysis and Design 5-1 Appendix 5: Conveyance Analysis Data 6 Operations and Maintenance Manual 6-1 7 Special Reports and Studies 7-1 1.0 PURPOSE AND SITE NARRATIVE The proposed Meadowdale Estates- Angle Residence project is located at 15724 72nd Ave W, Edmonds, WA 98026 consisting of tax parcel #0513100002601. The project proposes development of one single-family home with patio and associated driveway approach. EXISTING SITE The existing site is within tax parcel #00513100002601, totaling approximately 0.69 acres. In the existing condition, the site is undeveloped with land coverage consisting primarily of moderate forest and vegetation growth. Existing slopes range from moderate to steep across the site generally increasing towards the west. The site is located within a landslide hazard area and will need to adhere to the City of Edmond's minimum landslide hazard area requirements. According to the NRCS Soil Survey, site soils are primarily characterized as Alderwood- Urban land complex with 2 to 8 percent slopes and Alderwood -Everett gravelly sandy loams with 25 to 70 percent slopes. PROPOSED DEVELOPMENT The Meadowdale Estates Angle Residence project will contain a single-family home along with associated accesses and utilities on a 0.69-acre site. Access to the developed site from 72nd Ave W will be located at the eastern boundary of the site. Construction activities will disturb approximately 0.44 AC and improvements add 0.12 AC of new impervious area associated with onsite development and proposed frontage improvements. This project is subject to the 2017 City of Edmonds Stormwater Management Code (ECDC 18.30) and the Edmonds Stormwater Addendum. See Section 4.0 for additional discussion regarding basin delineation. Drainage Report 1-1 Job No.: C21-164 PROPOSED DRAINAGE SYSTEM Disturbed areas associated with the developed site are contained within one threshold discharge area. The Onsite Basin contains all onsite flow associated with the Onsite Basin will be collected and routed via closed pipe conveyance to the existing storm system with outfall at Puget Sound. A portion of flow from the Upstream Basin to the south will be collected and routed to the outfall via the proposed storm system. A portion of developed roof and landscape runoff will also be released to the west to match historic runoff rates. A Drainage Report for the Meadowview Estates subdivision dated March 12, 2014 is referenced in this report, as this proposed development will tie into the existing stormwater system for the Meadowview Estates subdivision. As this project triggers Minimum Requirements 1-9, the use of LID techniques was considered in accordance with List #2 requirements for stormwater management (Volume I, Chapter 2.5.5). An assessment of each applicable BMP, along with conclusions regarding feasibility, is provided in Section 4.0. EROSION/SEDIMENTATION CONTROL Erosion control measures that will be utilized during construction will include a combination of silt fence, storm drain inlet protection, interceptor swales, and a temporary sediment pond. See Section 2.0 for discussion of how SWPPP Elements are addressed. MINIMUM REQUIREMENTS Per the 2017 City of Edmonds Stormwater Management Code, Edmonds Stormwater Addendum, and 2014 Stormwater Management Manual for Western Washington (SWMMWW), Minimum Requirements 1-9 apply to the proposed development. Drainage Report 1-2 Job No.: C21-164 Minimum Requirement #1: Preparation of Stormwater Site Plans: This Report, along with the Construction Plans, satisfies this minimum requirement. Minimum Requirement #2: Construction Stormwater Pollution Prevention: See Section 2 of this Report for the SWPPP BMP Elements, and the SWPPP (submitted as a separate document) for a complete discussion of erosion control BMP's and their use specific to the site. Minimum Requirement #3: Source Control of Pollution: Permanent source control BMPs are not applicable for the subject site since the associated activities for the new residence do not fall within the types of facilities listed within Volume IV of the Drainage Manual (Residential developments are not required to implement source control BMP's). BMPs for erosion and sedimentation control are specified in the Construction Plans and the SWPPP. Minimum Requirement #4: Preservation of Natural Drainage Systems and Outfalls: Existing drainage flows primarily westward across the site, into Puget Sound to the west and downhill of the site. Developed flow will follow the same general direction of flow conveying runoff from the site through the private storm system located to the north of the property and reaching the outfall at Puget Sound. Minimum Requirement #5: Onsite Stormwater Management: As the project discharges directly to Puget Sound through the City's MS4, LID Performance Standards are not required. However, several BMPs must be implemented per ECDC 18.30. See Appendix 4 for the list of required On -site Stormwater Management BMPs. Minimum Requirement #6: Runoff Treatment: A Contech Stormfilter catch basin will provide runoff treatment for the site. The proposed onsite stormwater system will be conveyed through the private stormwater system for the Meadowview Estates project and the City's MS4 before directly discharging into Puget Sound. Drainage Report 1-3 Job No.: C21-164 Minimum Requirement #7: Flow Control: This requirement does not apply as runoff from the site discharges directly, through the City of Edmonds' municipal stormwater system, to Puget Sound. Minimum Requirement #8: Wetlands Protection: There are no wetlands within a quarter mile downstream of the site. See Wetland Map from City of Edmonds GIS data in Appendix 3. Minimum Requirement #9: Operation and Maintenance: See Operations and Maintenance Manual in Section 6.0 of this report. Drainage Report 1-4 Job No.: C21-164 Appendix 1: Project Overview 1. Figure 1.0 - Vicinity Map 2. Figure 2.0 - Existing Conditions Drainage Report 1-5 Job No.: C21-164 �---�e stl!M r\ I l 1Z I l PUGET SOUND PROJECT 0 NCD o�oF 60-. 6 5 4 L �3 J CL S H I VICINITYMAP SCALE: 1" =2000' Drawing: P:\Cv1\2021\C21-164 Meadowview Lot 4 — Angle Residence\Drawings\Exhibits\C21164E—EX—VM.dwg Platted: Dec 05, 2021 — 0:11pnn Surveying CAST ARCHITECTURE LDC1 En g i n ee r i n g Planning MEADOWVIEW LOT 4 Woodinville — Kent ANGLE RESIDENCE 20210 142nd Avenue NE 1851 Central PI S, #101 Woodinville, WA 98072 Kent, WA 98030 T425.806.1869 www.LDCcorp.com F425.482.2893 VICINITY MAP C21-164-Existing Conditions.mxd I MOD: 11/23/2021 1 fcavada INJ VJ C Omr"�G)�zrn C >��mGt�z ��'waoAzm �v _ �m Sw ANGLE r�r� rrl 0Ory >><>.-o ym Z= m> MEAD0WVIEW ESTATES- M:E O a Z D > D ' D Z O o N D > 2 tl A x z 0 O ANGLE RESIDENCE = EXISTING CONDITIONS Surveying LDC Engineering Planning Woodinville Kent 20210 142nd Avenue NE 1851 Central PI S, #101 Woodinville, WA 98072 Kent, WA 98030 T 425.806.1869 ....Loccorp.com F 425.482.2893 SOURCE SOURCE AGENCY INFORMATION DESCRIPTION SNOHOMISH COUNTY GIS PARCEL BOUNDARY SNOHOMISH COUNTY GIS CONTOURS GENERATED FROM BARE EARTH UDAR (SNOHOMISH COUNTY). THIS DATA HAS A STATED VERTICAL ACCURACY OF APPROXIMATELY 1 FOOT. 2.0 TEMPORARY EROSION AND SEDIMENT CONTROL ANALYSIS AND DESIGN Temporary Erosion and Sediment Control A Stormwater Pollution Prevention Plan (SWPPP) will be provided prior to construction. The SWPPP report is modeled under the guidelines of 2021 SCDM. Construction SWPPP Elements #1 through #13 are addressed below. Element #1 - Mark Clearing Limits: All clearing limits will be delineated with high visibility plastic fence or silt fence. See sheets ER-01 of the construction plans for locations and details. Element #2 - Establish Construction Access: Stabilized construction access will be installed as shown on the construction plans. See sheets ER-01 and ER-02 of the construction plans for locations and details (BMP C105). Element #3 - Control Flow Rates: Flow control for construction period runoff will be accomplished using a system of interceptor swales and check dams which will route flows to a temporary sediment pond located on the south side of the site, east of the steep slope buffer. See ER-01 of the preliminary plans for location and details of the temporary sediment pond and other flow and sediment control BMP's. Element #4 - Install Sediment Controls: Silt fence, catch basin protection, and a temporary sediment pond will be utilized to contain sediments within the project's clearing limits. See sheets ER-01 and ER-02 of the plans for locations and details. Element #5 - Stabilize Soils: Exposed soils will be stabilized as specified in the Grading and Erosion Control Notes. See sheet ER-02 of the construction plans for notes. Element #6 - Protect Slopes: Slopes range from moderate to steep across the site per NRCS soil survey. The site is located within a Landslide Hazard Area. Slopes shall be protected as specified under Element #5. Drainage Report 2-1 Job No.: C21-164 Element #7 - Protect Drain Inlets: Storm drain inlet protection will be utilized to contain sediments within the project's clearing limits. See sheets ER-01 of the construction plans for locations and details. Element #8 - Stabilize Channels and Outlets: Temporary interceptor swales will be stabilized using a series of check dams. See sheet ER-02 of the construction plans. Element #9 - Control Pollutants: Pollutants shall be controlled as specified in the Pollutant Control Notes. See sheet ER-02 of the construction plans for notes. Element #10 - Control De -Watering: Disposal options for de -watering water are as specified in the De -Watering Control Notes. See sheet ER-02 of the construction plans for notes. Element #11 - Maintain BMPs: Maintenance of the BMPs is specified within the Construction Sequence and Grading and Erosion Control Notes. See sheets ER-01 and ER- 02 of the construction plans for the Construction Sequence and notes. Element #12: Manage the Project: The Grading and Erosion Control Notes specify seasonal work limitations. Maintenance of the BMPs is specified within the Construction Sequence and Grading and Erosion Control Notes. See sheets ER-01 and ER-02 of the construction plans for the Construction Sequence and notes. Element #13: Protect Low Impact Development BMPs: Clearing limits, along with associated sediment controls, shall be implemented as indicated on the erosion control plans in order to limit sedimentation. Drainage Report 2-2 Job No.: C21-164 3.0 DOWNSTREAM ANALYSIS REPORT Task 1. Study Area Definition and Maps Snohomish County Bare Earth LiDAR, survey, and 2012 aerial photography were the best topographical references available for the area containing the site. The limits of the downstream analysis extend roughly 0.25 miles beyond the subject property's natural discharge location (See Figure 2.0, Downstream Map). Task 2. Resource Review All of the resources below have been reviewed for existing and potential issues near the project site: ■ Drainage Basin This site is located within the "Puget Sound Piped" sub -basin of the Cedar- Sammamish Watershed. Runoff from the proposed development will discharge into Puget Sound. ■ Floodplain / Floodway (FEMA) maps According to FEMA floodplain mapping, the subject property is not within a floodplain. Reference the FEMA FIS study map 53061C1305F. ■ Critical Areas Map Snohomish County and City of Edmonds critical areas mapping indicates a steep slope hazard area on site or adjacent to the site. ■ Drainage Complaints No drainage complaints for the site have been found. ■ Road Drainage Problems No road drainage problems were observed during the downstream site investigation. Drainage Report 4-1 Job No.: C21-164 ■ USDA Soil Survey According to the NRCS Soil Survey, site soils are primarily characterized as 42.9% Alderwood-Urban land complex with 2 to 8 percent slopes and 57.1 Alderwood -Everett gravelly sandy loam with 25 to 70 percent slopes. ■ Wetland Inventory Maps There are no wetlands within the site. There is a wetland approximately 0.13 miles upstream that is not expected to be impacted by the proposed development. See Wetland Map from City of Edmonds GIS, included in Appendix 3. ■ Migrating River Studies Migrating River Studies are not applicable to the proposed site development. ■ Section 303d List of Polluted Waters Washington State Department of Ecology's Water Quality Assessment does not include any Category 5 303d listings within 0.25 miles of the site. However, a compilation of all Category 5 listings in the receiving waterbody is included in Appendix 3. ■ Water Quality Problems No water quality impairments driven by pollutants were found in receiving waters within 0.25 miles of the site. ■ Stormwater Compliance Plans Not applicable to the proposed project. Drainage Report 4-2 Job No.: C21-164 Task 3. Field Inspection/Downstream Analysis (See Figure 3.0, Appendix 3-A) On August 24th, 2021, a Downstream Analysis was performed at the site. The weather conditions were 77°F and clear skies. The following observations were verified during the visit. Upstream Area: There is an upstream flow from southeast from the properties at the end of the road. Upstream flow from the north is collected by storm structures along 72nd Ave W. Downstream Flow: The site slopes to the west with a steep slope condition in the western half of the property. Flow from the site continues into the adjacent properties to the west and southwest and is conveyed by stormwater structures along 751h PL W. In addition, there is a yard drain system connecting the property to the to the adjacent properties. Flow conveyed through the yard drains runs down the bluff, ties back into the storm system on 751h Pt W and is then discharged into Puget Sound. The receiving waterbody is within the quarter -mile zone for this Downstream Analysis. Task 5. Mitigation of Existing or Potential Drainage Problems (not applicable for Level 1 Analysis) Upon downstream site investigation, there are no foreseen drainage problems that will require additional mitigation post development of the project. Drainage Report 4-3 Job No.: C21-164 Appendix 3: Resource Review 1. Downstream Analysis Images 2. Figure 3.0 - Downstream Analysis Map 3. Wetland Map from City of Edmonds GIS 4. FEMA Floodplain Maps 5. NRCS Soils Mapping 6. NRCS Soils Description Drainage Report 4-4 Job No.: C21-164 Downstream Analysis ,es Image 1: Yard drain location on property routing flow to the adjacent property to the north. Image 2: Yard drain on adjacent property. Flow is routed down the hill towards 75t" pl W. Drainage Report 4-5 Job No.: C21-164 Image 3: View from 751" Pl W looking up at site from the west. Approximate site location shown in red cloud, obstructed by trees and vegetation. Image 4: Facing to the west towards Puget Sound where flow discharges. Drainage Report 4-6 Job No.: C21-164 C21-164-Base.mxd I MOD: 11/23/2021 1 fcavada In _ ^ Cm WO CWoyoo`� OD.y D OD D w G mA O D zZc) m G�) Om W< czzo!n rnz D m-z>D0N< z ANGLE oZ,fD zo m�>n MEADOWVIEW ESTATES- OzD O D D rn x Z o ,p $ z ANGLE RESIDENCE I O = DOWNSTREAM ANALYSIS MAP LDC Surveying Engineering Planning Woodinville Kent 20210142nd Avenue NE 1851 Central PI S, #101 Woodinville, WA 98072 Kent, WA 98030 4 .869 ­LDCcorp.com F425.482.2893 SOURCE SOURCE AGENCY INFORMATION DESCRIPTION SNOHOMISH COUNTY GIS PARCEL BOUNDARY SNOHOMISH COUNTY GIS CONTOURS GENERATED FROM BARE EARTH UDAR (SNOHOMISH COUNTY). THIS DATA HAS A STATED VERTICAL ACCURACY OF APPROXIMATELY 1 FOOT. City of Edmonds Wetlands 15500 N LY--d I 1552 - 721 • � 550 LI 1S � Legend 15602 11 I 9WWetlands 7222 15602 F7121 � � I I �7� 1560C I 1 15604 712 71� 15 I 15716 15712 14;7, I5620 1 I 1 � I I 15700 15722 15715 15702 _ 15712 I 15706�� 15724 15 7r �15714� 15728 � 15724 l jWd 157 1�--172 9 15734 r . — 11732 15730 . r i 15806 i� ii 7400 1 L 7324 15806 III 15800 1 5808 �� + 7 li ■ 15911 l � �+I�5625� i ii r 11115908 15915 � 15605 a 59250 0 1590C li I ' III � !! 15910 ` 15910 ` • ± i ii1592 15902 k15917f115912�r74.------_-1 ,1:3,031 D� Notes 0 252.60 505.2 Feet 4,514 376.2 This ma is a user generated static output from an Internet mapping site and is for p B p pp B WGS_1984_Web-Mercator _Auxiliary -Sphere reference only. Data layers that appear on this map may or may not be accurate, current, or otherwise reliable. © City of Edmonds THIS MAP IS NOT TO BE USED FOR DESIGN OR CONSTRUCTION National Flood Hazard Layer FIRMette FEMA 1221207W 47°51'29"N 0 250 500 1,000 1,500 2,000 Basemap: USGS National Map: Orthoimagery. Data refreshed October, 2020 Legend SEE FIS REPORT FOR DETAILED LEGEND AND INDEX MAP FOR FIRM PANEL LAYOUT Without Base Flood Elevation (BFE) Zone A, V, A99 SPECIAL FLOOD With BFE or Depth Zone AE, AO, AH, VE, AR HAZARD AREAS Regulatory Floodway 0.2% Annual Chance Flood Hazard, Areas of 1% annual chance flood with average depth less than one foot or with drainage areas of less than one square mile Zone x Future Conditions 1% Annual Chance Flood Hazard zone Area with Reduced Flood Risk due to OTHER AREAS OF Levee. See Notes. zone FLOOD HAZARD I " Area with Flood Risk due to Leveezone D NOSCREEN Area of Minimal Flood Hazard zonex Effective LOMRs OTHER AREAS Area of Undetermined Flood Hazard zone D GENERAL - — - - Channel, Culvert, or Storm Sewer STRUCTURES IIIIIII Levee, Dike, or Floodwall Cross Sections with 1%Annual Chance j7•s Water Surface Elevation s - - - Coastal Transect - 513— Base Flood Elevation Line (BFE) Limit of Study Jurisdiction Boundary — --- Coastal Transect Baseline OTHER _ Profile Baseline FEATURES Hydrographic Feature Digital Data Available N No Digital Data Available MAP PANELS Unmapped The pin displayed on the map is an approximate point selected by the user and does not represent an authoritative property location. This map complies with FEMA's standards for the use of digital flood maps if it is not void as described below. The basemap shown complies with FEMA's basemap accuracy standards The flood hazard information is derived directly from the authoritative NFHL web services provided by FEMA. This map was exported on 8/25/2021 at 5:03 PM and does not reflect changes or amendments subsequent to this date and time. The NFHL and effective information may change or become superseded by new data over time. This map image is void if the one or more of the following map elements do not appear: basemap imagery, flood zone labels, legend, scale bar, map creation date, community identifiers, FIRM panel number, and FIRM effective date. Map images for unmapped and unmodernized areas cannot be used for regulatory purposes. Soil Map —Snohomish County Area, Washington L6 M 549930 549940 549950 549960 549970 549980 549990 550000 550M10 47' 51'23" N 17 validSoil Map may not be at I I I I I ... 47' 51'20" N 549940 549950 5499M 549970 549980 549990 550000 550010 Map Scale: 1:625 fi printed on A landscape (11" x 8.5") sheet. Meters N 0 5 10 20 30 0 30 60 120 180 Feet A Map projection: Web Mercator Comer coordinates: WGS84 Edge tics: LF­M Zone 1ON WGS84 usi)A Natural Resources Web Soil Survey Conservation Service National Cooperative Soil Survey 47' 51'23" N of- 47' 51'20" N 550020 550030 550040 550050 550060 3: b 8/25/2021 Page 1 of 3 MAP LEGEND Area of Interest (AOI) Area of Interest (AOI) Soils 0 Soil Map Unit Polygons 0,0 Soil Map Unit Lines C Soil Map Unit Points Special Point Features V Blowout Borrow Pit Clay Spot Closed Depression Gravel Pit Gravelly Spot O Landfill ALava Flow Marsh or swamp j* Mine or Quarry OMiscellaneous Water OPerennial Water V Rock Outcrop + Saline Spot Sandy Spot _ Severely Eroded Spot Q Sinkhole Slide or Slip 0o Sodic Spot Soil Map —Snohomish County Area, Washington MAP INFORMATION ® Spoil Area The soil surveys that comprise your AOI were mapped at 1:24,000. Q Stony Spot Very Stony Spot Warning: Soil Map may not be valid at this scale. Wet Spot Enlargement of maps beyond the scale of mapping can cause misunderstanding of the detail of mapping and accuracy of soil Other line placement. The maps do not show the small areas of Special Line Features contrasting soils that could have been shown at a more detailed scale. Water Features Streams and Canals Please rely on the bar scale on each map sheet for map measurements. Transportation .+. Rails Source of Map: Natural Resources Conservation Service Web Soil Survey URL: ..� Interstate Highways Coordinate System: Web Mercator (EPSG:3857) US Routes Maps from the Web Soil Survey are based on the Web Mercator Major Roads projection, which preserves direction and shape but distorts distance and area. A projection that preserves area, such as the Local Roads Albers equal-area conic projection, should be used if more accurate calculations of distance or area are required. Background Aerial Photography This product is generated from the USDA-NRCS certified data as of the version date(s) listed below. Soil Survey Area: Snohomish County Area, Washington Survey Area Data: Version 22, Jun 4, 2020 Soil map units are labeled (as space allows) for map scales 1:50,000 or larger. Date(s) aerial images were photographed: Sep 2, 2018—Sep 25, 2018 The orthophoto or other base map on which the soil lines were compiled and digitized probably differs from the background imagery displayed on these maps. As a result, some minor shifting of map unit boundaries may be evident. uSDA Natural Resources Web Soil Survey 8/25/2021 Conservation Service National Cooperative Soil Survey Page 2 of 3 Soil Map —Snohomish County Area, Washington Map Unit Legend Map Unit Symbol Map Unit Name Acres in AOI Percent of AOI IL 4 Alderwood-Everett gravelly 0.4 57.1% sandy loams, 25 to 70 percent slopes 5 Alderwood-Urban land 0.3 42.9% complex, 2 to 8 percent slopes Totals for Area of Interest 0.7 100.0% USDA Natural Resources Web Soil Survey 8/25/2021 Conservation Service National Cooperative Soil Survey Page 3 of 3 4.0 FLOW CONTROL ANALYSIS AND DESIGN 4.1 Pre -Developed Hydrology/Land Cover Flow control and water quality requirements are controlled by the 2017 City of Edmonds Stormwater Management Code. The pre -developed and developed conditions were modeled in WWHM2012 for the purpose of detention sizing and flow -duration control. Based on the site location, WWHM2012 used the Everett Gage and a Precipitation Scale factor of 0.8. As the existing structures within the project boundaries do not total 35% or greater impervious land cover, the project is considered new development. The pre - developed condition (forested) is applied to all the area of the Onsite and Offsite Basins. Total developed project area is approximately 0.69 AC. For visual representation of the following basins, see Figures 3.0 "Predeveloped Hydrology Map" in Appendix 4. Predeveloped areas and ground coverages associated with the Onsite and Upstream Basins are modeled in WWHM2012 are as follows: Existing Onsite Basin: Onsite Basin GROUND COVER AREA (acre) Forested, Mod 0.20 Forested, Steep 0.49 TOTAL 0.69 Upstream Basin: Upstream Basin GROUND COVER AREA (acre) Forested, Mod 1.74 TOTAL 1.74 Drainage Report 4-7 Job No.: C21-164 4.2 Developed Site Hydrology In compliance with the 2017 City of Edmonds Stormwater Management Code, runoff from onsite developed/disturbed surfaces will be collected, treated, and mitigated to the extent feasible. Project development has been divided into two basins in the developed condition. The Onsite and Upstream Basins consist of all areas routed to the existing private stormwater system of the subdivision. Pervious Land Cover Pervious land cover in each developed basin has been modeled as pasture, with the exception of the 0.19 acres of forested land cover in the protected steep slope portion of the property. In Section 7.2 of the 2014 Low Impact Development Technical Guidance Manual for Puget Sound (LID Manual), referenced in Appendix III-C of the 2014 DOE manual, it is prescribed that if landscaped areas are underlain with BMP T5.13 soils, the area may be modeled as pasture. These landscaped areas will be underlain with BMP T5.13 soil mixtures in the developed condition and thus have been modeled as pasture land cover in WWHM. Onsite Basin: The Onsite Basin is 0.69 acres in the developed condition and is comprised of a single- family home, drive access, and landscaping. This area will be collected and routed through a system of closed pipes to the existing Meadowview Estates private stormwater system at the northwestern portion of the developed site. For visual representation of the following developed conditions see Figure 4.0, "Developed Hydrology Map". In the developed condition, the Onsite Basin has been modeled using WWHM2012 with the following areas and ground cover designations: Drainage Report 4-8 Job No.: C21-164 Onsite Basin GROUND COVER AREA (acre) Rooftops, Flat 0.04 Driveways, Steep 0.04 Sidewalk, Mod 0.02 Pasture, Mod 0.40 Forested, Steep 0.19 TOTAL 0.69 Upstream Basin: Development of the upstream basin is not included within the scope of the project. For WWHM2012 modeling purposes, the 1.74 acres of the basin will remain as forested cover in the developed condition. Upstream Basin GROUND COVER AREA (acre) Forested, Mod 1.74 TOTAL 1.74 Modeled Flow Rates: Using WWHM2012, the following flow rates were determined for the outflow from the site: Storm Event 501- Predeveloped Rate (cfs) 801- Developed Rate (cfs) 2-year 0.0017 0.0378 10-year 0.0021 0.0597 50-year 0.0023 0.0824 100-year 0.0023 0.0931 4.3 Onsite Stormwater Management (Minimum Requirement #5) Because the project drains directly to Puget Sound through the municipal storm system and because of the existing steep slope condition, onsite LID BMPs are not feasible. However, the ECDC 18.30 and Edmonds Stormwater Addendum require the implementation of BMP T5.13 (Post -Construction Soil Quality and Depth). Drainage Report 4-9 Job No.: C21-164 4.4 Water Quality Treatment Water quality requirements are controlled by the City of Edmonds Stormwater Management Code. Water quality for this project will be achieved through media filtration via Contech Storm Filters within the existing private stormwater system. Due to the small increase in flow and minimal increase in pollution generating impervious surfaces, the existing filters are not expected to be significantly impacted. Further information can be found in Section 5 of the Drainage Report for Meadowview Estates from July 16, 2013. Drainage Report 4-10 Job No.: C21-164 Appendix 4: Flow Control and Water Quality Analysis 1. WWHM2012 Data 2. Figure 4.0 - Predeveloped Hydrology Map 3. Figure 5.0 - Developed Hydrology Map 4. Contech Stormfilter Detail Drainage Report 4-11 Job No.: C21-164 WWHM2012 PROJECT REPORT Project Name: 202301223 Angle Residence Site Name: Site Address: City Report Date: 1/23/2023 Gage : Everett Data Start : 1948/10/01 Data End : 2009/09/30 Precip Scale: 0.80 Version Date: 2021/08/18 Version : 4.2.18 Low Flow Threshold for POC 1 : 50 Percent of the 2 Year High Flow Threshold for POC 1: 50 year PREDEVELOPED LAND USE Name : Onsite Basin Bypass: No GroundWater: No Pervious Land Use acre A B, Forest, Mod .2 A B, Forest, Steep .49 Pervious Total 0.69 Impervious Land Use acre Impervious Total 0 Basin Total 0.69 Element Flows To: Surface Interflow Name : Upstream Basin Bypass: No GroundWater: No Pervious Land Use acre Groundwater A B, Forest, Mod 1.74 Pervious Total 1.74 Impervious Land Use acre Impervious Total 0 Basin Total 1.74 Element Flows To: Surface Interflow MITIGATED LAND USE Name : Onsite Basin Bypass: No GroundWater: No Pervious Land Use acre A B, Forest, Steep .19 A B, Pasture, Mod .39 Pervious Total 0.58 Impervious Land Use acre ROOF TOPS FLAT 0.06 DRIVEWAYS STEEP 0.04 SIDEWALKS MOD 0.01 Impervious Total 0.11 Basin Total 0.69 Element Flows To: Surface Interflow Name : Upstream Basin Bypass: No GroundWater: No Pervious Land Use A B, Forest, Mod acre 1.74 Groundwater Groundwater Pervious Total 1.74 Impervious Land Use acre Impervious Total 0 Basin Total 1.74 Element Flows To: Surface Interflow Groundwater ANALYSIS RESULTS Stream Protection Duration Predeveloped Landuse Totals for POC #1 Total Pervious Area:2.43 Total Impervious Area:O Mitigated Landuse Totals for POC #1 Total Pervious Area:2.32 Total Impervious Area:0.11 Flow Frequency Return Periods for Predeveloped. POC #1 Return Period Flow(cfs) 2 year 0.001713 5 year 0.001983 10 year 0.002104 25 year 0.002214 50 year 0.002274 100 year 0.002321 Flow Frequency Return Periods for Mitigated. POC #1 Return Period Flow(cfs) 2 year 0.037771 5 year 0.050495 10 year 0.059713 25 year 0.072299 50 year 0.082377 100 year 0.093076 Stream Protection Duration Annual Peaks for Predeveloped and Mitigated. POC #1 Year Predeveloped Mitigated 1949 0.001 0.038 1950 0.002 0.041 1951 0.002 0.047 1952 0.002 0.037 1953 0.002 0.045 1954 0.002 0.058 1955 0.002 0.046 1956 0.002 0.021 1957 0.002 0.032 1958 0.001 0.083 1959 0.002 0.034 1960 0.002 0.034 1961 0.002 0.104 1962 0.001 0.043 1963 0.002 0.044 1964 0.002 0.026 1965 0.001 0.032 1966 0.001 0.032 1967 0.002 0.071 1968 0.002 0.037 1969 0.002 0.073 1970 0.001 0.031 1971 0.002 0.040 1972 0.002 0.052 1973 0.002 0.042 1974 0.002 0.050 1975 0.002 0.041 1976 0.002 0.030 1977 0.001 0.030 1978 0.002 0.022 1979 0.001 0.046 1980 0.002 0.039 1981 0.002 0.030 1982 0.002 0.033 1983 0.002 0.039 1984 0.002 0.036 1985 0.002 0.049 1986 0.002 0.049 1987 0.002 0.044 1988 0.002 0.038 1989 0.002 0.034 1990 0.002 0.029 1991 0.002 0.038 1992 0.002 0.036 1993 0.002 0.029 1994 0.001 0.031 1995 0.001 0.029 1996 0.002 0.046 1997 0.002 0.040 1998 0.002 0.048 1999 0.001 0.021 2000 0.002 0.082 2001 0.000 0.025 2002 0.002 0.026 2003 0.002 0.034 2004 0.001 0.068 2005 0.001 0.030 2006 0.002 0.041 2007 0.002 0.039 2008 0.002 0.033 2009 0.001 0.030 Stream Protection Duration Ranked Annual Peaks for Predeveloped and Mitigated. POC #1 Rank Predeveloped Mitigated 1 0.0020 0.1038 2 0.0019 0.0834 3 0.0019 0.0821 4 0.0019 0.0727 5 0.0019 0.0709 6 0.0019 0.0676 7 0.0019 0.0576 8 0.0019 0.0517 9 0.0019 0.0501 10 0.0019 0.0495 11 0.0019 0.0486 12 0.0019 0.0480 13 0.0019 0.0470 14 0.0019 0.0462 15 0.0019 0.0460 16 0.0019 0.0458 17 0.0019 0.0450 18 0.0019 0.0444 19 0.0019 0.0440 20 0.0019 0.0426 21 0.0018 0.0424 22 0.0018 0.0410 23 0.0018 0.0406 24 0.0018 0.0406 25 0.0018 0.0398 26 0.0018 0.0396 27 0.0018 0.0394 28 0.0018 0.0388 29 0.0018 0.0386 30 0.0018 0.0384 31 0.0018 0.0378 32 0.0017 0.0378 33 0.0017 0.0371 34 0.0017 0.0366 35 0.0017 0.0359 36 0.0017 0.0358 37 0.0017 0.0345 38 0.0017 0.0341 39 0.0017 0.0340 40 0.0017 0.0340 41 0.0017 0.0330 42 0.0016 0.0325 43 0.0016 0.0323 44 0.0016 0.0323 45 0.0016 0.0318 46 0.0015 0.0310 47 0.0015 0.0309 48 0.0015 0.0304 49 0.0014 0.0301 50 0.0014 0.0298 51 0.0014 0.0296 52 0.0014 0.0295 53 0.0014 0.0292 54 0.0014 0.0289 55 0.0013 0.0286 56 0.0013 0.0263 57 0.0013 0.0258 58 0.0012 0.0249 59 0.0012 0.0218 60 0.0012 0.0214 61 0.0005 0.0212 Stream Protection Duration POC #1 The Facility FAILED Facility FAILED duration standard for 1+ flows. Flow(cfs) Predev Mit Percentage Pass/Fail 0.0009 883 150363 17028 Fail 0.0009 863 148909 17254 Fail 0.0009 835 147476 17661 Fail 0.0009 807 146192 18115 Fail 0.0009 775 144866 18692 Fail 0.0009 756 143497 18981 Fail 0.0009 728 142321 19549 Fail 0.0010 695 141145 20308 Fail 0.0010 679 139947 20610 Fail 0.0010 650 138920 21372 Fail 0.0010 627 137808 21978 Fail 0.0010 600 136696 22782 Fail 0.0010 579 135669 23431 Fail 0.0010 566 134664 23792 Fail 0.0011 546 133616 24471 Fail 0.0011 522 132525 25387 Fail 0.0011 500 131584 26316 Fail 0.0011 481 130643 27160 Fail 0.0011 461 129595 28111 Fail 0.0011 444 128718 28990 Fail 0.0011 427 127755 29919 Fail 0.0012 404 126771 31378 Fail 0.0012 389 125894 32363 Fail 0.0012 378 125018 33073 Fail 0.0012 362 124055 34269 Fail 0.0012 353 123221 34906 Fail 0.0012 344 122387 35577 Fail 0.0012 330 121531 36827 Fail 0.0013 317 120654 38061 Fail 0.0013 305 119799 39278 Fail 0.0013 294 118922 40449 Fail 0.0013 283 118130 41742 Fail 0.0013 270 117318 43451 Fail 0.0013 257 116526 45340 Fail 0.0013 246 115671 47020 Fail 0.0014 240 114879 47866 Fail 0.0014 229 114109 49829 Fail 0.0014 219 113296 51733 Fail 0.0014 212 112591 53108 Fail 0.0014 208 111778 53739 Fail 0.0014 199 110944 55750 Fail 0.0014 192 110216 57404 Fail 0.0015 185 109446 59159 Fail 0.0015 182 108655 59700 Fail 0.0015 173 107864 62349 Fail 0.0015 171 107115 62640 Fail 0.0015 159 106367 66897 Fail 0.0015 154 105597 68569 Fail 0.0015 149 104869 70381 Fail 0.0016 142 104078 73294 Fail 0.0016 139 103372 74368 Fail 0.0016 131 102623 78338 Fail 0.0016 121 101875 84194 Fail 0.0016 119 101148 84998 Fail 0.0016 112 100463 89699 Fail 0.0016 105 99715 94966 Fail 0.0017 100 99009 99009 Fail 0.0017 96 98346 102443 Fail 0.0017 88 97683 111003 Fail 0.0017 85 96998 114115 Fail 0.0017 76 96314 126728 Fail 0.0017 72 95651 132848 Fail 0.0017 65 94966 146101 Fail 0.0018 60 94325 157208 Fail 0.0018 57 93662 164319 Fail 0.0018 51 93020 182392 Fail 0.0018 47 92421 196640 Fail 0.0018 40 91801 229502 Fail 0.0018 39 91159 233741 Fail 0.0018 35 90603 258865 Fail 0.0019 31 90004 290335 Fail 0.0019 29 89362 308144 Fail 0.0019 21 88764 422685 Fail 0.0019 15 88207 588046 Fail 0.0019 13 87566 673584 Fail 0.0019 8 87010 1087625Fail 0.0019 1 86475 8647500Fail 0.0020 0 85919 n/a Fail 0.0020 0 85405 n/a Fail 0.0020 0 84892 n/a Fail 0.0020 0 84400 n/a Fail 0.0020 0 83887 n/a Fail 0.0020 0 83416 n/a Fail 0.0020 0 82946 n/a Fail 0.0021 0 82411 n/a Fail 0.0021 0 81962 n/a Fail 0.0021 0 81513 n/a Fail 0.0021 0 81021 n/a Fail 0.0021 0 80572 n/a Fail 0.0021 0 80101 n/a Fail 0.0021 0 79652 n/a Fail 0.0022 0 79203 n/a Fail 0.0022 0 78732 n/a Fail 0.0022 0 78262 n/a Fail 0.0022 0 77791 n/a Fail 0.0022 0 77363 n/a Fail 0.0022 0 76914 n/a Fail 0.0022 0 76486 n/a Fail 0.0023 0 76080 n/a Fail 0.0023 0 75609 n/a Fail The development has an increase in flow durations from 1/2 Predeveloped 2 year flow to the 2 year flow or more than a 10% increase from the 2 year to the 50 year flow. The development has an increase in flow durations for more than 50% of the flows for the range of the duration analysis. Water Quality BMP Flow and Volume for POC #1 On-line facility volume: 0.0082 acre-feet On-line facility target flow: 0.0138 cfs. Adjusted for 15 min: 0.0138 cfs. Off-line facility target flow: 0.0078 cfs. Adjusted for 15 min: 0.0078 cfs. LID Report LID Technique Used for Total Volume Percent Water Quality Percent Comment Treatment? Needs Volume Water Quality Treatment Infiltrated Treated (ac-ft Total Volume Infiltrated 0.00 0.00 0% No Treat. Credit Compliance with LID Standard 8 Duration Analysis Result = Failed Perind and Impind Changes No changes have been made. Volume Infiltration Cumulative Through Volume Facility (ac-ft.) (ac-ft) 0.00 0.00 Volume Infiltration Credit 0.00 This program and accompanying documentation are provided 'as -is' without warranty of any kind. The entire risk regarding the performance and results of this program is assumed by End User. Clear Creek Solutions Inc. and the governmental licensee or sublicensees disclaim all warranties, either expressed or implied, including but not limited to implied warranties of program and accompanying documentation. In no event shall Clear Creek Solutions Inc. be liable for any damages whatsoever (including without limitation to damages for loss of business profits, loss of business information, business interruption, and the like) arising out of the use of, or inability to use this program even if Clear Creek Solutions Inc. or their authorized representatives have been advised of the possibility of such damages. Software Copyright © by : Clear Creek Solutions, Inc. 2005-2023; All Rights Reserved. eo c uo d c c �Em< _R E V 3 z � 3 e < � 9 V _ N 8 C O O R3 W J z Q y W o i 0 C.4) _ CL W ►1 uj 0 Z Ix W Q a z NAD 1983 HARN STATEPLANE WASHINGTON REVISION: JOB NUMBER: C21-164 DRAWING NAME: C21-164-4.0 DESIGNER: FCAVADA DRAWING BY: FCAVADA DATE: 11/30/2021 SCALE: AS SHOWN JURISDICTION: EDMONDS FIGURE: 4.0 0 VICINITY MAP LEGEND Subject Property Parcel Boundary Watercourse Contours (LiDAR) i v 10 Foot Contour 2 Foot Contour Scale: 1 "=100' A _ DEVELOPED BASIN AREAS ONSITE TOTAL = 0.69 AC FORESTED TOTAL = 0.19 AC ROOFTOPS TOTAL = 0.04 AC DRIVEWAYS TOTAL = 0.04 AC SIDEWALK TOTAL = 0.02 AC PASTURE TOTAL = 0.40 AC UPSTREAM TOTAL = 1.74 AC FORESTED s Upstream Basin TOTAL = 1.74 AC c E _ C Y E Z ^ 3 v � < IiT�V/Alll � � a ai W UJ QVG 0 � Z cn W N N LLJ 0 ct L J fn 0 W W o Q ��a Wo a �'JJ � W rn NAD 1983 HARN STATEPLANE WASHINGTON 0 - •. M REVISION: JOB NUMBER: C21-164 DRAWING DES GN R: F AVADA 164-6.0 DRAWING BY: FCAVADA DATE:11/30/2021 SCALE: AS SHOWN M JURISDICTION: EDMONDS FIGURE: M 5.0 ACCESS COVER CONCRETE COLLAR AND REBAR TO MEET a HS20 IF APPLICABLE BY CONTRACTOR { ✓� ��� a� ddd w 1 No I ., I. VANED INLET GRATE ° (SOLID COVER OPTIONAL) INSIDE RIM INSIDE RIM 1' 0" 4'-83/4" COLLAR OUTSIDE RIM STORMFILTER CARTRIDGE PERMANENT POOL ELEVATION CARTRIDGE SUPPORT FLOW KIT CATCHBASIN FOOT (TYP. OF 4) PLAN VIEW STORMFILTER STEEL CATCHBASIN DESIGN NOTES STORMFILTER TREATMENT CAPACITY IS A FUNCTION OF THE CARTRIDGE SELECTION AND THE NUMBER OF CARTRIDGES. 1 CARTRIDGE CATCHBASIN HAS A MAXIMUM OF ONE CARTRIDGE. SYSTEM IS SHOWN WITH A 27" CARTRIDGE, AND IS ALSO AVAILABLE WITH AN 18" CARTRIDGE. STORMFILTER CATCHBASIN CONFIGURATIONS ARE AVAILABLE WITH A DRY INLET BAY FOR VECTOR CONTROL. PEAK HYDRAULIC CAPACITY PER TABLE BELOW. IF THE SITE CONDITIONS EXCEED PEAK HYDRAULIC CAPACITY, AN UPSTREAM BYPASS STRUCTURE IS REQUIRED. CARTRIDGE SELECTION CARTRIDGE HEIGHT 27" 1 18" 18" DEEP RECOMMENDED HYDRAULIC DROP (H) 3.05' 3.3' SPECIFIC FLOW RATE (gpm/sf) 2 gpm/sf 1.67* gpm/sf 1 gpm/sf 2 gpm/sf 1.67* gpm/sf 1 gpm/sf 2 gpm/sf 1.67* gpm/sf 1 gpm/sf CARTRIDGE FLOW RATE (gpm) 22.5 1 18.79 11.25 15 12.53 7.5 15 12.53 7.5 PEAK HYDRAULIC CAPACITY 1.0 1.0 1.8 INLET PERMANENT POOL LEVEL (A) V-0" 1'-0" 2'-0" OVERALL STRUCTURE HEIGHT (B) 4'-9" 3'-9" 1 4'-9" * 1.67 gpm/sf SPECIFIC FLOW RATE IS APPROVED WITH PHOSPHOSORBO (PSORB) MEDIA ONLY GENERALNOTES 1. CONTECH TO PROVIDE ALL MATERIALS UNLESS NOTED OTHERWISE. 2. FOR SITE SPECIFIC DRAWINGS WITH DETAILED STORMFILTER CATCHBASIN STRUCTURE DIMENSIONS AND WEIGHTS, PLEASE CONTACT YOUR CONTECH ENGINEERED SOLUTIONS LLC REPRESENTATIVE. www.contechES.com 3. STORMFILTER CATCHBASIN WATER QUALITY STRUCTURE SHALL BE IN ACCORDANCE WITH ALL DESIGN DATA AND INFORMATION CONTAINED IN THIS DRAWING. 4. INLET SHOULD NOT BE LOWER THAN OUTLET. INLET (IF APPLICABLE) AND OUTLET PIPING TO BE SPECIFIED BY ENGINEER AND PROVIDED BY CONTRACTOR. 5. MANUFACTURER TO APPLY A SURFACE BEAD WELD IN THE SHAPE OF THE LETTER "O" ABOVE THE OUTLET PIPE STUB ON THE EXTERIOR SURFACE OF THE STEEL SFCB. 6. STORMFILTER CATCHBASIN EQUIPPED WITH 4 INCH (APPROXIMATE) LONG STUBS FOR INLET (IF APPLICABLE) AND OUTLET PIPING. STANDARD OUTLET STUB IS 8 INCHES IN DIAMETER. MAXIMUM OUTLET STUB IS 15 INCHES IN DIAMETER. CONNECTION TO COLLECTION PIPING CAN BE MADE USING FLEXIBLE COUPLING BY CONTRACTOR. 7. STEEL STRUCTURE TO BE MANUFACTURED OF 1/4 INCH STEEL PLATE. CASTINGS SHALL MEET AASHTO M306 LOAD RATING. TO MEET HS20 LOAD RATING ON STRUCTURE, A CONCRETE COLLAR IS REQUIRED. WHEN REQUIRED, CONCRETE COLLAR WITH #4 REINFORCING BARS TO BE PROVIDED BY CONTRACTOR. 8. FILTER CARTRIDGES SHALL BE MEDIA -FILLED, PASSIVE, SIPHON ACTUATED, RADIAL FLOW, AND SELF CLEANING. RADIAL MEDIA DEPTH SHALL BE 7-INCHES. FILTER MEDIA CONTACT TIME SHALL BE AT LEAST 38 SECONDS. 9. SPECIFIC FLOW RATE IS EQUAL TO THE FILTER TREATMENT CAPACITY (gpm) DIVIDED BY THE FILTER CONTACT SURFACE AREA (sq ft). INSTALLATION NOTES A. ANY SUB -BASE, BACKFILL DEPTH, AND/OR ANTI -FLOTATION PROVISIONS ARE SITE -SPECIFIC DESIGN CONSIDERATIONS AND SHALL BE SPECIFIED BY ENGINEER OF RECORD. B. CONTRACTOR TO PROVIDE EQUIPMENT WITH SUFFICIENT LIFTING AND REACH CAPACITY TO LIFT AND SET THE CATCHBASIN (LIFTING CLUTCHES PROVIDED). C. CONTRACTOR TO TAKE APPROPRIATE MEASURES TO PROTECT CARTRIDGES FROM CONSTRUCTION -RELATED EROSION RUNOFF. 4'-43/4" OPTIONAL FLOATABLES 2'-a'—,-4„ SLOPED LID BAFFLE 2 B PERMANENT POOL ELEVATION FINISHED GRADE B — SECTION A -A FILTRATION BAY INLET FILTRATION BAY m INLET INLET STUB INLET STUB (OPTIONAL) (OPTIONAL) CLEANOUT ACCESS PLUG ON WEIR WALL The Stormwater Management StormFilter® L 2 -0„ INSIDE 2'-0Y2" OUTSIDE SECTION B-B LIFTING EYE 1 (TYP. OF 4) 1 WEIR WALL = — 5" — 5" FLOW OUTLET STUB OUTLET PIPE FROM FLOWKIT CATCHBASIN FOOT (TYP. OF 4) C NTECH® ENGINEERED SOLUTIONS LLC www.contechES.com 9025 Centre Pointe Dr., Suite 400, West Chester, OH 45069 1-CARTRIDGE CATCHBASIN STORMFILTER DATA STRUCTUREID XXX WATER QUALITY FLOW RATE cfs X.XX PEAK FLOW RATE (<1 cfs) X.XX RETURN PERIOD OF PEAK FLOW (yrs) XXX CARTRIDGE HEIGHT (27", 18", 18" DEEP) XX CARTRIDGE FLOW RATE (gpm) XX MEDIA TYPE (PERLITE, ZPG, PSORB) XXXXX RIM ELEVATION XXX.XX' PIPE DATA: I I.E. IDIAMETER INLET STUB XXX.XX' I XX" OUTLET STUB XXX.XX' I XX" CONFIGURATION OUTLET OUTLET INLET INLET INLET INLET SLOPED LID YES\NO SOLID COVER YES\NO NOTES/SPECIAL REQUIREMENTS: 1 CARTRIDGE CATCHBASIN STORMFILTER STANDARD DETAIL 800-526-3999 513-645-7000 513-645-7993 FAX 5.0: CONVEYANCE ANALYSIS AND DESIGN The Rational Method verify the capacity of the proposed on -site stormwater system. The smallest diameter pipe (6") with the shallowest pipe slope (0.50%) was assessed against the 100-year developed flow from WWHM2012. The following table summarizes the results of the Manning's Analysis calculations. The full open channel flow calculations can be found in Appendix 5. Pipe Diameter: 6" Min. Slope 0.50% Pipe Capacity 0.40 cfs 100-year Peak Flow 0.09 cfs Evaluation System Adequate Drainage Report 5-1 Job No.: C21-164 Appendix 5: Conveyance Analysis Data 1. Open Channel Flow Calculations Open Channel Flow Calculator Land Development Consultants, Inc. For Circular Pipes 14201 NE 200th St. Ste. 100 Tel: (425) 806-1869 Woodinville, WA 98072 Fax: (425) 482-2893 Project Name Description: Meadowview Lot 4- Angle Residence Conveyance Pipe Diameter (D) = 6 in Pipe Slope (S) = 0.50 Flow Depth (y) = 0.50 ft Flowrate (Q) = 0.40 cfs Mannings Coeff. (n) = 0.013 Theta Angle (0) = 6.28 rad Wetted Area (A) = 0.20 ft2 Wet. Perimeter (P) = 1.57 ft Hydraulic Radius (R) = 0.13 ft Top Width (T) = 0.00 ft Flow Velocity = 2.03 fps 119MI Formulas: Theta Angle (0): If y > r : 9 = 2;T — 2a cos( Y — r) r < r —Y If y_ r: B= 2 a cos( ) r Wetted Area (A): A = 8 (9 — sin O)d2 Wetted Perimeter (P): P = 1 Od 2 Hydraulic Radius (R): R = A P Top Width (T): T = sin lu / Project No.: C21-164 Date: 11/30/2021 Calc. By: FGC where: r = Pipe Radius where: r = Pipe Radius SECTION 6.0: OPERATIONS AND MAINTENANCE MANUAL The proposed storm drainage system consists of buried pipes and catch basins. These facilities will require periodic maintenance and inspection. Inspection and maintenance procedures are contained on the following pages. Drainage Report 6-1 Job No.: C21-164 CATCH BASINS Maintenanc Defect Conditions When Maintenance is Needed Results Expected When e Maintenance is performed Component General Trash & Debris Trash or debris of more than 1/2 cubic foot which is No Trash or debris located (Includes Sediment) located immediately in front of the catch basin opening immediately in front of catch basin or is blocking capacity of the basin by more than 10% opening. Trash or debris (in the basin) that exceeds 1/3 the depth No trash or debris in the catch from the bottom of basin to invert the lowest pipe into or basin. out of the basin. Trash or debris in any inlet or outlet pipe blocking more Inlet and outlet pipes free of trash or than 1/3 of its height. debris. Dead animals or vegetation that could generate odors No dead animals or vegetation that could cause complaints or dangerous gases (e.g., present within the catch basin. methane). Deposits of garbage exceeding 1 cubic foot in volume No condition present which would attract or support the breeding of insects or rodents. Structure Damage to Corner of frame extends more than 3/4 inch past curb Frame is even with curb. Frame and/or Top face into the street (If applicable). Slab Top slab has holes larger than 2 square inches or Top slab is free of holes and cracks. cracks wider than 1/4 inch (intent is to make sure all material is running into basin). Frame not sitting flush on top slab, i.e., separation of Frame is sitting flush on top slab. more than 3/4 inch of the frame from the top slab. Cracks in Basin Cracks wider than 1/2 inch and longer than 3 feet, any Basin replaced or repaired to design Walls/ Bottom evidence of soil particles entering catch basin through standards. cracks, or maintenance person judges that structure is unsound. Cracks wider than 1/2 inch and longer than 1 foot at the No cracks more than 1/4 inch wide joint of any inlet/ outlet pipe or any evidence of soil at the joint of inlet/outlet pipe. particles entering catch basin through cracks. Sediment/ Basin has settled more than 1 inch or has rotated more Basin replaced or repaired to design Misalignment than 2 inches out of alignment. standards. Fire Hazard Presence of chemicals such as natural gas, oil and No flammable chemicals present. gasoline. Vegetation Vegetation growing across and blocking more than 10% No vegetation blocking opening to of the basin opening. basin. Vegetation growing in inlet/outlet pipe joints that is more No vegetation or root growth than six inches tall and less than six inches apart. present. Pollution Nonflammable chemicals of more than 1/2 cubic foot per No pollution present other than three feet of basin length. surface film. Catch Basin Cover Not in Place Cover is missing or only partially in place. Any open Catch basin cover is closed Cover catch basin requires maintenance. Locking Mechanism Mechanism cannot be opened by on maintenance Mechanism opens with proper tools. Not Working person with proper tools. Bolts into frame have less than 1/2 inch of thread. Cover Difficult to One maintenance person cannot remove lid after Cover can be removed by one Remove applying 80 lbs. of lift; intent is keep cover from sealing maintenance person. off access to maintenance. Ladder Ladder Rungs Ladder is unsafe due to missing rungs, misalignment, Ladder meets design standards and Unsafe rust, cracks, or sharp edges. allows maintenance person safe access. Metal Grates Grate with opening wider than 7/8 inch. Grate opening meets design (If standards. Applicable) Trash and Debris Trash and debris that is blocking more than 20% of Grate free of trash and debris. rate surface. Damaged or Grate missing or broken member(s) of the grate. Grate is in place and meets design Missing. standards. Drainage Report 6-2 Job No.: C21-164 CONVEYANCE SYSTEMS (PIPES & DITCHES) Maintenance Defect Conditions When Maintenance is Needed Results Expected When Component Maintenance is Performed Pipes Sediment & Debris Accumulated sediment that exceeds 20% of the Pipe cleaned of all sediment and diameter of the pipe. debris. Vegetation Vegetation that reduces free movement of water All vegetation removed so water throu h i es. flows free)y through pipes. Damaged Protective coating is damaged; rust is causing Pipe repaired or replaced. more than 50% deterioration to any part of pipe. Any dent that decreases the cross section area of Pipe repaired or replaced. i e b more than 20%. Open Ditches Trash & Debris Trash and debris exceeds 1 cubic foot per 1,000 Trash and debris cleared from square feet of ditch and slopes. ditches. Sediment Accumulated sediment that exceeds 20 % of the Ditch cleaned/ flushed of all design depth. sediment and debris so that it matches design. Vegetation Vegetation that reduces free movement of water Water flows freely through through ditches. ditches. Erosion Damage to See 'Ponds" Standard No. 1 See "Ponds" Standard No. 1 Slopes Rock Lining Out of Place Maintenance person can see native soil beneath Replace rocks to design or Missing If Applicable). the rock lining. standards. Catch Basins See "Catch Basins: Standard No. 5 See "Catch Basins" Standard No. 5 Debris Barriers See "Debris Barriers" Standard No.6 See "Debris Barriers" Standard (e.g., Trash Rack No. 6 Drainage Report 6-3 Job No.: C21-164 SECTION 7.0: SPECIAL REPORTS AND STUDIES The following report is referenced in this project: • Meadowview Estates Large Site Storm Drainage Report, LDC Corp., dated March 1412014 Drainage Report 7-1 Job No.: C21-164