PRELIMINARY STORM DRAINAGE REPORT

Transcription

1 PRELIMINARY STORM DRAINAGE REPORT DRURY LANE DEVELOPMENT 704 1ST STREET SULTAN, WA PARCEL # AUDITOR S FILE NO CITY OF SULTAN SNOHOMISH COUNTY, WASHINGTON PREPARED FOR: STACY MACGREGOR PO BOX 80 GOLD BAR, WA PREPARED BY: MICHAEL GIESEKE Date: January 5 th, 2018 RAIN CITY DEVELOPMENT DRURY LANE DEVELOPMENT PROJECT NO. RCD # NE 45 TH ST, SEATTLE, WA (425)

2 PRELIMINARY STORM DRAINAGE REPORT DRURY LANE DEVELOPMENT 704 1ST STREET SULTAN, WA PARCEL # AUDITOR S FILE NO CITY OF SULTAN SNOHOMISH COUNTY, WASHINGTON PREPARED FOR: STACY MACGREGOR PO BOX 80 GOLD BAR, WA PREPARED BY: MICHAEL GIESEKE Date: January 5 th, 2018 RAIN CITY DEVELOPMENT DRURY LANE DEVELOPMENT PROJECT NO. RCD # NE 45 TH ST, SEATTLE, WA (425)

3 Table of Contents 1) Project Overview:... 3 Analysis of Minimum Requirements:... 3 Minimum Requirement #1: Targeted Stormwater Site Plan... 3 Minimum Requirement #2: SWPPP Narrative:... 4 Minimum Requirements #3: Water Pollution Source Control for New Development:... 4 Minimum Requirements #4: Preservation of natural drainage systems and outfalls and provisions of off-site mitigation:... 4 Minimum Requirements #5: On-site Stormwater Management... 4 Minimum Requirements #6: Run-off Treatment Requirements... 5 Minimum Requirements #7: Flow control... 5 Minimum Requirements #8: Wetlands Protection... 5 Minimum Requirements #9: Operations and Maintenance Manual ) Vicinity Map: ) Existing Conditions Exhibits... 8 Assessor Map / SCOPI GIS... 8 USGS Soil Map... 9 Sensitive Area Map...10 FEMA...11 Existing Conditions Exhibit ) Existing Conditions Overview ) Areas of Site Limitation ) Off-Site Analysis...15 Targeted Drainage Report ) Drainage Design...17 Developed Conditions Exhibit ) SWPPP ) Permanent Stormwater Control Plan...20 Preliminary Conveyance Calculations:...20 Curve Number Calculation Exhibits...21 Manning s Pipe Sizing Equation Spreadsheets...21 Preliminary Infiltration Basin Calculations:...22 Preliminary Water Quality Calculations:...22 Preliminary Biofiltration Swale Calculations:...22 Preliminary Upstream Pre Treatmeant / Filtration Vault Calculations: ) Special Reports...23 Geotechnical Engineering Report...23 Environmental Study: ) Other Reports and Approvals ) Operations and Maintenance Manual ) Bond Quantity Worksheet...27 RCD # January, 2018 Drury Lane Development

4 1) Project Overview: The development name is the Drury Lane Development. The subject property address is 704 1st Street, in the City of Sultan, WA , PARCEL # , Auditor s File No The project consists of 1 existing parcel and 9-new parcels: One existing singlefamily residence will remain separate from the development within the existing parcel, 1 storm and recreation tract, and 8 new single-family residential lots will be constructed as part of the development. The stormwater from the existing property infiltrates onsite with overflows and groundwater leading to the existing stream west of the property. Other work will include a private roadway, driveways, a tight-lined conveyance system and an overall conveyance system. The project proposes to utilize the infiltrative nature of the existing soils and route the storm runoff to the existing low point onsite. The conveyance systems will route the stormwater runoff from the site for pre-treatment/water quality treatment upstream of the final stormwater permutation through an infiltration basin. Excess overflows will be routed to the existing city s stormwater conveyance system. Analysis of Minimum Requirements: Minimum Requirement #1: Targeted Stormwater Site Plan Drainage Plan Description: Once developed, runoff from the proposed new single family residences roof and footing drains, driveways, yards, and roadway will be collected and tight lined through a series of individual lot pipes systems conveyed to the roadway catch basin and storm pipes conveyance system that will convey the overall site flow to the proposed infiltration basin located in a proposed Storm Tract 999 on the southwest portion of the property. The infiltration basin will be sized per SCC 30.63A.550 so that discharges match the required range of pre-developed discharge rates. This will be accomplished by sizing the infiltration basin to fully infiltrate onsite. An emergency overflow system is proposed to tie into the existing City of Sultan Conveyance System. The WWHM 2012 Stormwater Program is used to size the stormwater system. Manning s equation and a backflow analysis will be used to size the onsite conveyance system. Proposed Water Quality Measures: Water quality treatment will be provided via storm-filter cartridges which will be located directly upstream of the infiltration basin. Existing and Proposed Drainage Basins: The project contains a single drainage basin onsite with existing stormwater infiltrating onsite. The storm runoff will be collected and treated prior to infiltration within the Storm Tract 999. The runoff in the existing condition spreads over the pervious surfaces as it sheet flows to the existing low point onsite and infiltrates. For further details, please see the Existing Conditions Exhibit located in Section 3 of this report, and the offsite analysis, in section 6 of this report. The runoff in the proposed conditions will drain from tight lined roof systems into the proposed closed conveyance systems consisting of standard catch basin and piped conveyance. The RCD # January, 2018 Drury Lane Development

5 runoff from the short plat is proposed to infiltrate onsite and be contained within the Storm Tract 999. Any overflows will be designed to spill into the existing City of Sultan roadway conveyance system. Proposed Drainage System: The proposed drainage system will consist of a series of catch basins, swales and ditches, storm pipes to collect and convey developed runoff to the water quality facilities andinfiltration basin onsite. The system will utilize water quality swale / pre-treatment basin / filtration vault facilities upstream of the infiltration system for water quality. Upstream Drainage Analysis: The project is bounded to the west by curb and gutter and adjacent properties on all other sides. Each adjacent property is graded to drain into the City of Sultan s roadway conveyance system with only minor shared area infiltrating onsite at the shared low point. There are small areas from adjacent lawns that drain to the onsite low point, but there are no significant upstream basin areas to the property and are assumed to have no contributions. Minimum Requirement #2: SWPPP Narrative: This will be completed following the Preliminary Plat Application. Element #1: Preserve Vegetation / Mark Clearing Limits: Element #2: Establish Construction Access: Element #3: Control Flow Rates: Element #4: Install Sediment Controls: Element #5: Stabilize Soils: Element #6: Protect Slopes: Element #7: Protect Permanent Drain Inlets: Element #8: Stabilize Channels and Outlets Element #9: Control Pollutants: Element #10: Control Dewatering: Element #11: Maintain BMP s: Element #12: Manage the Project: Minimum Requirements #3: Water Pollution Source Control for New Development: There are no identified source control activities that will need to be addressed as a part of this residential development. Minimum Requirements #4: Preservation of natural drainage systems and outfalls and provisions of off-site mitigation: The entire project site drains to the mid-site low point. The drainage onsite will be maintained so that runoff will continue to flow to the low point. Minimum Requirements #5: On-site Stormwater Management Stormwater management is required to be implemented in accordance with SCC 30.63A.525. The code states that BMP requirements are to be implemented to the maximum extent feasible without causing flooding or erosion impacts. The on-site gravelly and sandy soils are such that infiltration is feasible and recommended, per the geotechnical report, later contained within this cover. The on-site soils are classified as Hydrologic Soil Group A. Additionally, the project will RCD # January, 2018 Drury Lane Development

6 implement post-construction soil amendment and perforated stub-out connections to satisfy any additional LID requirements. Minimum Requirements #6: Run-off Treatment Requirements All on-site runoff will be treated using basic water quality measures. On-site water quality measures are proposed to be met with a pre-treatment basin or storm filter filtration facilities upstream of the infiltration basin. Please refer to Section 7 of this report for more details. Minimum Requirements #7: Flow control The proposed drainage system will consist of a series of catch basins and storm pipes to collect and convey the runoff to the infiltration basin on site and discharge any emergency overflows to the existing City of Sultan conveyance system. Please see the WWHM2012 calculations in Section 7 for infiltration basin sizing. Minimum Requirements #8: Wetlands Protection There are no wetlands located on site therefore no wetland protection is necessary for this project. Minimum Requirements #9: Operations and Maintenance Manual Operations and Maintenance manuals will be provided for the infiltration basin and water quality facilities in section 12 of this report. RCD # January, 2018 Drury Lane Development

7 Attachment B: Report summary: Drainage Information Summary Note: This section will be completed following preliminary plat submittal. RCD # January, 2018 Drury Lane Development

8 2) Vicinity Map: RCD # January, 2018 Drury Lane Development

9 3) Existing Conditions Exhibits Assessor Map / SCOPI GIS RCD # January, 2018 Drury Lane Development

10 USGS Soil Map RCD # January, 2018 Drury Lane Development

11 Sensitive Area Map Snohomish County Lidar Folio. FEMA Flood Plain Map available on the following page. RCD # January, 2018 Drury Lane Development

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14 4) Existing Conditions Overview The subject property is rectangular east to west, is approximately 2.02 Acres (per Snohomish County Scopi). The property abuts 1 st Street, and is on the east side of the road. The frontage is approximately 180-ft north to south, and the property is approximately 490-ft east to west. There is an existing single-family resident on the southeast corner of the property. The property is mostly vegetation with a cluster of trees in the center portion of the property. Single family residences border the property on all sides except the western portion of the property which is accessed from 1 st Street. The project is generally level, with gentle slopes in towards the center third of the property with an approximate drop of 4-6 feet in the low spot from the general elevation of the subject property. Per the Snohomish County SnoScape (see geotechnical report in Section 10 of this report), there are no steep slopes onsite. Additionally, per the environmental review, there are no flood plains or wetlands on or adjacent to the site within 200-ft of the subject property. See special reports study, section 10 of this report for more information. Per the geotechnical report, the topsoil is loose organic sandy silt (top soil) and native mediumstiff non-plastic sandy silt (alluvium) extend to 3-4ft below the surface. Underlying these soils were medium-dense, gravelly sand and slightly silty sand (Alluvium) that generally extend to the maximum explored depth test pits. See the geotechnical report for more information, in Section 10 of this report. The topography of the site slopes to the low point in the middle-westerly portion of the site. The onsite vegetation is mostly second growth trees and vegetation. For drainage purposes, the site will be modeled as outwash-forest in its entirety. This project consists of one existing tax parcel with the following parcel number: The existing home will be partitioned into its own parcel separate from the developer as part of the residential project. RCD # January, 2018 Drury Lane Development

15 5) Areas of Site Limitation The site contains a low spot on the central-westerly portion of the site. This portion of the site will require special care during construction as to not compact the soils and adversely affect the permeability of the soils for future water quality and stormwater infiltration. Additionally this area will be required for in-situ onsite testing (PIT Test) to determine infiltration rates following the preliminary plat application submittal. RCD # January, 2018 Drury Lane Development

16 6) Off-Site Analysis The project abuts an existing City of Sultan stormwater conveyance system on High Street and 1st Street. The subject property does not drain off site and percolates into groundwater and infiltrates onsite combining with the City of Sultan stormwater conveyance system downstream. The subject property does not have any natural features in its downstream drainage path for any unforeseen flows that do overflow offsite. There are no known flooding issues within the subject property. The existing off-site conveyance system drains and outfalls to Skykomish River, more than a quarter-mile downstream of the site. A more in depth off-site analysis will be conducted following the preliminary plat review upon City requirement. Targeted Drainage Report The Targeted Drainage Report is included on the following page. RCD # January, 2018 Drury Lane Development

17 Targeted Drainage Report THIS PAGE INTENTIONALLY LEFT BLANK REPLACE PDF PAGE WITH TDR REPORT RCD # January, 2018 Drury Lane Development

18 7) Drainage Design The project consists of maintaining an existing single-family residence, a storm tract and 8 single-family residential detached dwelling units. This work includes a public road and will include minor frontage improvements and ROW dedication along 1st Street. Along with the frontage improvements, a storm drainage runoff collection system will be installed to capture runoff from the developed surfaces and conveyed to the onsite facilities for pre-treatment / water quality treatment and final dispersion through infiltration on site. Emergency overflow runoff will be designed to flow to the 1 st Street roadway containing the existing City of Sultan conveyance system. Please see the Developed Conditions Exhibit on the following page for more information. RCD # January, 2018 Drury Lane Development

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20 8) SWPPP The SWPPP will be prepared in accordance with the Snohomish County and Department of Ecology NPDES regulations and will be submitted separate from this report. Temporary Sediment Pond Sizing Calculations to be included in the final Storm Drainage Report. RCD # January, 2018 Drury Lane Development

21 9) Permanent Stormwater Control Plan Stormwater runoff will be collected by a combination of tight lined individual lot conveyance systems with LID perf-pipe/infiltration trenches with overflows into the project roadway conveyance system consisting of a series of catch basins and pipes. The roadway conveyance system will convey the stormwater runoff to a water quality swale / pretreatment basin / filtration facility upstream of the proposed infiltration facility. The stormwater runoff is proposed to fully infiltrate onsite. Any emergency overflow will be routed to the City of Sultan existing stormwater conveyance system off 1 st Street and High Street. Preliminary Conveyance Calculations: The onsite conveyance system will be sized using the rational method and Manning s formula sized for the 50-year storm event. The backwater conveyance calculations will be attached and exhibits provided following the preliminary plat application submittal. The preliminary sizing is provided on the following pages using basic pipe slope and manning equations for each conveyance system RCD # January, 2018 Drury Lane Development

22 Project Sultan 9 Lot Short Plat Date 9/4/2017 Description: Individual Lot - Roof and Footing Conveyance System C-Value (1-Lot, roof tightline conveyance) Type of Land Cover Dense Forest Light Forest Pasture Lawns Heavy Soil (Flat) Lawns Heavy Soil (Rolling) Playgrounds Gravel Areas Pavements and Roofs Open Water (pond, lakes, wetlands) Total C-Value Area IR - Peak Rainfall Intensity La Storm Event PR AR BR TC IR Total Precipitation Coefficient Coefficient Time of Concentration 25-year year Rational Method Storm Event C IR A QR 25-year year

23 Project Sultan 9 Lot Short Plat Date 9/4/2017 Description: Individual Lot - Yard Conveyance System Type of Land Cover Dense Forest Light Forest Pasture Lawns Heavy Soil (Flat) Lawns Heavy Soil (Rolling) Playgrounds Gravel Areas Pavements and Roofs C-Value (1-Lot, conveyance) Open Water (pond, lakes, wetlands) Total C-Value Area IR - Peak Rainfall Intensity Storm Event PR AR BR TC IR Total Precipitation Coefficient Coefficient Time of Concentration 25-year year Rational Method Storm Event C IR A QR 25-year year

24 Project Sultan 9 Lot Short Plat Date 9/4/2017 Description: 3-Lots - Yard Conveyance System Type of Land Cover Dense Forest Light Forest Pasture Lawns Heavy Soil (Flat) Lawns Heavy Soil (Rolling) Playgrounds Gravel Areas Pavements and Roofs C-Value (3-Lot conveyance) Open Water (pond, lakes, wetlands) Total C-Value Area IR - Peak Rainfall Intensity Storm Event PR AR BR TC IR Total Precipitation Coefficient Coefficient Time of Concentration 25-year year Rational Method Storm Event C IR A QR 25-year year

25 Project Sultan 9 Lot Short Plat Date 9/4/2017 Description: Roadway Conveyance System - Total basin area tributary to pond, not including storm tract Type of Land Cover Dense Forest Light Forest Pasture Lawns Heavy Soil (Flat) Lawns Heavy Soil (Rolling) Playgrounds Gravel Areas Pavements and Roofs C-Value (Roadway conveyance) Open Water (pond, lakes, wetlands) Total C-Value Area IR - Peak Rainfall Intensity Storm Event PR AR BR TC IR Total Precipitation Coefficient Coefficient Time of Concentration 25-year year Rational Method Storm Event C IR A QR 25-year year

26 Project Sultan 9 Lot Short Plat Date 9/4/2017 Description: Total Site Area Type of Land Cover Dense Forest Light Forest Pasture C-Value (Total Project Conveyance) Lawns Heavy Soil (Flat) Lawns Heavy Soil (Rolling) Playgrounds Gravel Areas Pavements and Roofs Open Water (pond, lakes, wetlands) Total C-Value Area IR - Peak Rainfall Intensity Storm Event PR AR BR TC IR Total Precipitation Coefficient Coefficient Time of Concentration 25-year year Rational Method Storm Event C IR A QR 25-year year

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34 Preliminary Infiltration Basin Calculations: The project contains a single drainage basin onsite with existing stormwater infiltrating onsite. The runoff in the existing condition spreads over the pervious surfaces as it sheet flows to the existing low point onsite and infiltrates. For further details, please see the Existing Conditions Exhibit located in Section 3 of this report, and the offsite analysis, in section 6 of this report. The proposed infiltration basin is designed to accommodate all runoff from the proposed roadway, driveways, yards, roof and footing drains for the developed properties. The runoff will be collected and conveyed through a series of individual lot tightline conveyance systems to the roadway conveyance system consisting of catch basin and storm pipes to upstream water quality measures. Water quality treatment will be provided by a swale or filter-vault which will be located directly upstream of the infiltration basin. Further water quality measures can be found later in this section. Following the upstream water quality measures, the final infiltration basin will be located in the proposed Storm Tract 999 on the southwest portion of the property. The infiltration basin will be sized per SCC 30.63A.550 so that discharges match developed discharge durations to pre-developed durations for the range of pre-developed discharge rates from 50-percent of the two-year peak flow up to the full 50-year peak flow. The preliminary sizing has a target to infiltrate on flows onsite, with any unforeseen emergency overflows out letting to the City of Sultan existing conveyance system downstream of the project site. The WWHM 2012 Stormwater Program was used to size the stormwater basin. The WWHM calculations can be found at the end of this section. Preliminary Water Quality Calculations: All on-site PGIS runoff will be treated using basic water quality measures. Preliminary Biofiltration Swale Calculations: The preliminary water quality rates were calculated using the 15-min water-quality flow rate as determined upstream of the infiltration basin in Storm Tract 999. The Water Quality Flow rate was determined by WWHM to be cfs. Water quality will be treated with basic measures upstream of the infiltration basin with a pre-settling basin, vault or stormfilter cartridges or other means. Water quality measures will be finalized following the preliminary plat submittal. Preliminary Upstream Pre Treatmeant / Filtration Vault Calculations: If a filtration vault / oil water separator is allowed and / or required, it will be designed following the preliminary plat submittal. RCD # January, 2018 Drury Lane Development

35 WWHM2012 PROJECT REPORT Project Name: RCD S9L-FOS-3.0-Rock Site Name: Stacy MacGregor 9 Lot Short Plat Site Address: 1st Street City : Sultan Report Date: 12/11/2017 Gage : Everett Data Start : 1948/10/01 Data End : 2009/09/30 Precip Scale: 1.40 Version Date: 2017/04/14 Version : Low Flow Threshold for POC 1 : 50 Percent of the 2 Year High Flow Threshold for POC 1: 50 year PREDEVELOPED LAND USE Name : Basin 1 Bypass: No GroundWater: No Pervious Land Use acre A B, Forest, Flat Pervious Total Impervious Land Use acre Impervious Total 0 Basin Total Element Flows To: Surface Interflow Groundwater MITIGATED LAND USE Name : Lot 1 Bypass: No GroundWater: No

36 Pervious Land Use acre A B, Lawn, Flat.12 A B, Lawn, Mod.004 Pervious Total Impervious Land Use acre ROOF TOPS FLAT 0.1 DRIVEWAYS FLAT Impervious Total Basin Total Element Flows To: Surface Interflow Groundwater Bottom of Pond InfiltrBottom of Pond Infiltr Name : InfilTrnch 2 Bottom Length: ft. Bottom Width: 2.00 ft. Trench bottom slope 1: 0 To 1 Trench Left side slope 0: 0 To 1 Trench right side slope 2: 0 To 1 Material thickness of first layer: 3 Pour Space of material for first layer: 0.33 Material thickness of second layer: 1.5 Pour Space of material for second layer: 0.1 Material thickness of third layer: 0 Pour Space of material for third layer: 0 Discharge Structure Riser Height: 2.5 ft. Riser Diameter: 12 in. Element Flows To: Outlet 1 Outlet 2 Bottom of Pond Infiltr Gravel Trench Bed Hydraulic Table Stage(feet) Area(ac.) Volume(ac-ft.) Discharge(cfs) Infilt(cfs)

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38 Name : Lot 2 Bypass: No GroundWater: No Pervious Land Use acre A B, Lawn, Flat.03 A B, Lawn, Mod.003 Pervious Total Impervious Land Use acre ROOF TOPS FLAT 0.04 DRIVEWAYS FLAT 0.01 Impervious Total 0.05 Basin Total Element Flows To: Surface Interflow Groundwater InfilTrnch 2 InfilTrnch 2 Name : Lot 3 Bypass: No

39 GroundWater: No Pervious Land Use acre A B, Lawn, Flat.03 A B, Lawn, Mod.003 Pervious Total Impervious Land Use acre ROOF TOPS FLAT 0.04 DRIVEWAYS FLAT 0.01 Impervious Total 0.05 Basin Total Element Flows To: Surface Interflow Groundwater InfilTrnch 3 InfilTrnch 3 Name : Lot 4 Bypass: No GroundWater: No Pervious Land Use acre A B, Lawn, Flat.03 A B, Lawn, Mod.003 Pervious Total Impervious Land Use acre ROOF TOPS FLAT 0.04 DRIVEWAYS FLAT 0.01 Impervious Total 0.05 Basin Total Element Flows To: Surface Interflow Groundwater InfilTrnch 4 InfilTrnch 4 Name : InfilTrnch 3 Bottom Length: ft. Bottom Width: 2.00 ft.

40 Trench bottom slope 1: 0 To 1 Trench Left side slope 0: 0 To 1 Trench right side slope 2: 0 To 1 Material thickness of first layer: 3 Pour Space of material for first layer: 0.33 Material thickness of second layer: 1.5 Pour Space of material for second layer: 0.1 Material thickness of third layer: 0 Pour Space of material for third layer: 0 Discharge Structure Riser Height: 2.5 ft. Riser Diameter: 12 in. Element Flows To: Outlet 1 Outlet 2 Bottom of Pond Infiltr Gravel Trench Bed Hydraulic Table Stage(feet) Area(ac.) Volume(ac-ft.) Discharge(cfs) Infilt(cfs)

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42 Name : InfilTrnch 4 Bottom Length: ft. Bottom Width: 2.00 ft. Trench bottom slope 1: 0 To 1 Trench Left side slope 0: 0 To 1 Trench right side slope 2: 0 To 1 Material thickness of first layer: 3 Pour Space of material for first layer: 0.33 Material thickness of second layer: 1.5 Pour Space of material for second layer: 0.1 Material thickness of third layer: 0 Pour Space of material for third layer: 0 Discharge Structure Riser Height: 2.5 ft. Riser Diameter: 12 in. Element Flows To: Outlet 1 Outlet 2 Bottom of Pond Infiltr Gravel Trench Bed Hydraulic Table Stage(feet) Area(ac.) Volume(ac-ft.) Discharge(cfs) Infilt(cfs)

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44 Name : Lot 5 Bypass: No GroundWater: No Pervious Land Use acre A B, Lawn, Flat.06 A B, Lawn, Mod.008 Pervious Total Impervious Land Use acre ROOF TOPS FLAT 0.08 DRIVEWAYS FLAT Impervious Total Basin Total Element Flows To: Surface Interflow Groundwater InfilTrnch 5 InfilTrnch 5 Name : InfilTrnch 5 Bottom Length: ft. Bottom Width: 2.00 ft. Trench bottom slope 1: 0 To 1 Trench Left side slope 0: 0 To 1 Trench right side slope 2: 0 To 1 Material thickness of first layer: 3 Pour Space of material for first layer: 0.33 Material thickness of second layer: 1.5 Pour Space of material for second layer: 0.1 Material thickness of third layer: 0 Pour Space of material for third layer: 0 Discharge Structure Riser Height: 2.5 ft. Riser Diameter: 12 in. Element Flows To: Outlet 1 Outlet 2 Bottom of Pond Infiltr Gravel Trench Bed Hydraulic Table

45 Stage(feet) Area(ac.) Volume(ac-ft.) Discharge(cfs) Infilt(cfs)

46 Name : Lot 6 Bypass: No GroundWater: No Pervious Land Use acre A B, Lawn, Flat.06 A B, Lawn, Mod.005 Pervious Total Impervious Land Use acre ROOF TOPS FLAT 0.08 DRIVEWAYS FLAT Impervious Total Basin Total 0.161

47 Element Flows To: Surface Interflow Groundwater InfilTrnch 6 InfilTrnch 6 Name : InfilTrnch 6 Bottom Length: ft. Bottom Width: 2.00 ft. Trench bottom slope 1: 0 To 1 Trench Left side slope 0: 0 To 1 Trench right side slope 2: 0 To 1 Material thickness of first layer: 3 Pour Space of material for first layer: 0.33 Material thickness of second layer: 1.5 Pour Space of material for second layer: 0.1 Material thickness of third layer: 0 Pour Space of material for third layer: 0 Discharge Structure Riser Height: 2.5 ft. Riser Diameter: 12 in. Element Flows To: Outlet 1 Outlet 2 Bottom of Pond Infiltr Gravel Trench Bed Hydraulic Table Stage(feet) Area(ac.) Volume(ac-ft.) Discharge(cfs) Infilt(cfs)

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49 Name : Lot 7 Bypass: No GroundWater: No Pervious Land Use acre A B, Lawn, Flat.08 A B, Lawn, Mod.017 Pervious Total Impervious Land Use acre ROOF TOPS FLAT 0.06 DRIVEWAYS FLAT Impervious Total Basin Total Element Flows To: Surface Interflow Groundwater InfilTrnch 7 InfilTrnch 7 Name : InfilTrnch 7 Bottom Length: ft. Bottom Width: 2.00 ft. Trench bottom slope 1: 0 To 1 Trench Left side slope 0: 0 To 1 Trench right side slope 2: 0 To 1 Material thickness of first layer: 3 Pour Space of material for first layer: 0.33 Material thickness of second layer: 1.5 Pour Space of material for second layer: 0.1 Material thickness of third layer: 0 Pour Space of material for third layer: 0 Discharge Structure Riser Height: 2.5 ft. Riser Diameter: 12 in. Element Flows To:

50 Outlet 1 Outlet 2 InfilTrnch 6 Gravel Trench Bed Hydraulic Table Stage(feet) Area(ac.) Volume(ac-ft.) Discharge(cfs) Infilt(cfs)

51 Name : InfilTrnch 8 Bottom Length: ft. Bottom Width: 2.00 ft. Trench bottom slope 1: 0 To 1 Trench Left side slope 0: 0 To 1 Trench right side slope 2: 0 To 1 Material thickness of first layer: 3 Pour Space of material for first layer: 0.33 Material thickness of second layer: 1.5 Pour Space of material for second layer: 0.1 Material thickness of third layer: 0 Pour Space of material for third layer: 0 Discharge Structure

52 Riser Height: 2.5 ft. Riser Diameter: 12 in. Element Flows To: Outlet 1 Outlet 2 Bottom of Pond Infiltr Gravel Trench Bed Hydraulic Table Stage(feet) Area(ac.) Volume(ac-ft.) Discharge(cfs) Infilt(cfs)

53 Name : InfilTrnch 9 Bottom Length: ft. Bottom Width: 2.00 ft. Trench bottom slope 1: 0 To 1 Trench Left side slope 0: 0 To 1 Trench right side slope 2: 0 To 1 Material thickness of first layer: 3 Pour Space of material for first layer: 0.33 Material thickness of second layer: 1.5

54 Pour Space of material for second layer: 0.1 Material thickness of third layer: 0 Pour Space of material for third layer: 0 Discharge Structure Riser Height: 2.5 ft. Riser Diameter: 12 in. Element Flows To: Outlet 1 Outlet 2 InfilTrnch 8 Gravel Trench Bed Hydraulic Table Stage(feet) Area(ac.) Volume(ac-ft.) Discharge(cfs) Infilt(cfs)

55 Name : Lot 8 Bypass: No GroundWater: No

56 Pervious Land Use acre A B, Lawn, Flat.04 A B, Lawn, Mod.018 Pervious Total Impervious Land Use acre ROOF TOPS FLAT 0.03 DRIVEWAYS FLAT Impervious Total Basin Total Element Flows To: Surface Interflow Groundwater InfilTrnch 8 InfilTrnch 8 Name : Lot 9 Bypass: No GroundWater: No Pervious Land Use acre A B, Lawn, Flat.04 A B, Lawn, Mod.012 Pervious Total Impervious Land Use acre ROOF TOPS FLAT 0.03 DRIVEWAYS FLAT Impervious Total Basin Total Element Flows To: Surface Interflow Groundwater InfilTrnch 9 InfilTrnch 9 Name : ROW-US-Trench Bypass: No GroundWater: No Pervious Land Use acre

57 A B, Lawn, Flat.007 A B, Lawn, Mod.004 Pervious Total Impervious Land Use acre ROADS FLAT 0.15 Impervious Total 0.15 Basin Total Element Flows To: Surface Interflow Groundwater Bottom of Pond InfiltrBottom of Pond Infiltr Name : Storm Tract Bypass: No GroundWater: No Pervious Land Use acre A B, Lawn, Flat.12 A B, Lawn, Mod.005 Pervious Total Impervious Land Use acre DRIVEWAYS MOD 0.07 POND 0.03 Impervious Total 0.1 Basin Total Element Flows To: Surface Interflow Groundwater Bottom of Pond InfiltrBottom of Pond Infiltr Name : ROW-DS-Trenc Bypass: No GroundWater: No Pervious Land Use acre A B, Lawn, Flat.007 A B, Lawn, Mod.003

58 Pervious Total 0.01 Impervious Land Use acre ROADS FLAT Impervious Total Basin Total Element Flows To: Surface Interflow Groundwater Bottom of Pond InfiltrBottom of Pond Infiltr Name : Bottom of Pond Infiltration Gallery Bottom Length: ft. Bottom Width: ft. Trench bottom slope 1: 0 To 1 Trench Left side slope 0: 0 To 1 Trench right side slope 2: 0 To 1 Material thickness of first layer: 4 Pour Space of material for first layer: 0.33 Material thickness of second layer: 0 Pour Space of material for second layer: 0 Material thickness of third layer: 0 Pour Space of material for third layer: 0 Infiltration On Infiltration rate: 12 Infiltration safety factor: Total Volume Infiltrated (ac-ft.): Total Volume Through Riser (ac-ft.): Total Volume Through Facility (ac-ft.): Percent Infiltrated: 100 Total Precip Applied to Facility: 0 Total Evap From Facility: Discharge Structure Riser Height: 3.5 ft. Riser Diameter: 5040 in. Element Flows To: Outlet 1 Outlet 2 Gravel Trench Bed Hydraulic Table Stage(feet) Area(ac.) Volume(ac-ft.) Discharge(cfs) Infilt(cfs)

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60 ANALYSIS RESULTS Stream Protection Duration Predeveloped Landuse Totals for POC #1 Total Pervious Area:1.906 Total Impervious Area:0 Mitigated Landuse Totals for POC #1 Total Pervious Area:0.437 Total Impervious Area:0.837 Flow Frequency Return Periods for Predeveloped. POC #1 Return Period Flow(cfs) 2 year year year year year

61 100 year Flow Frequency Return Periods for Mitigated. POC #1 Return Period Flow(cfs) 2 year 0 5 year 0 10 year 0 25 year 0 50 year year 0 Stream Protection Duration Annual Peaks for Predeveloped and Mitigated. POC #1 Year Predeveloped Mitigated

62 Stream Protection Duration Ranked Annual Peaks for Predeveloped and Mitigated. POC #1 Rank Predeveloped Mitigated

63 Stream Protection Duration POC #1 The Facility PASSED The Facility PASSED. Flow(cfs) Predev Mit Percentage Pass/Fail Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass

64 Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass

65 Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Water Quality BMP Flow and Volume for POC #1 On-line facility volume: acre-feet On-line facility target flow: cfs. Adjusted for 15 min: cfs. Off-line facility target flow: cfs. Adjusted for 15 min: cfs. LID Report LID Technique Used for Total Volumn Volumn Infiltration Cumulative Percent Water Quality Percent Comment Treatment? Needs Through Volumn Volumn Volumn Water Quality Treatment Facility (ac-ft.) Infiltration Infiltrated Treated (ac-ft) (ac-ft) Credit Bottom of Pond Infiltration Ga N N InfilTrnch 2 N N 0.00 InfilTrnch 3 N N 0.00 InfilTrnch 4 N N 0.00 InfilTrnch 5 N N 0.00 Total Volume Infiltrated % No Treat. Credit Compliance with LID Standard 8 Duration Analysis Result = Passed Perlnd and Implnd Changes No changes have been made.

66 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 ; All Rights Reserved.

67 10) Special Reports The following special reports have been prepared for this project: Geotechnical Engineering Report: Onsite Analysis of Soils Prepared by: Geotest: Date: June 16, 2017 Summary: Infiltration feasible. Design rate 12 in/hr Recommended. (Pit test recommended for final design rate). Use Import Structural fill for foundation soils. Native re-use OK for lawn/other fill. Footing Drains 12 below floor slab grade. Road Section: Light Duty: 2-1/2 HMA over 6 CSBC(or 2 CSTC & 10 Gravel borrow) Heavy Duty: 4 HMA over 8 CSBC(or 2 CSTC & 12 Gravel borrow) Stormwater Pollutant Treatment: Near-surface soils suitable for onsite pollutant treatment. (poor infiltration in WQ soils). The full Geotechnical report can be found on the following page. RCD # January, 2018 Drury Lane Development

68 GEOTECHNICAL REPORT THIS PAGE INTENTIONALLY LEFT BLANK REPLACE THIS PAGE IN PDF WITH FULL GETECHNICAL REPORT RCD # January, 2018 Drury Lane Development

69 Environmental Study: Wetland Delineation Prepared by: Blue Heron Services Date: April 25 th, 2017 Summary: No wetlands onsite. RCD # January, 2018 Drury Lane Development

70 Blue Heron Services Blue Heron Services Inc PO 393 Index WA (phone) On site review Prepared for Stacy MacGregor 704 First Street, Sultan Tax # Property Description SEC 32 TWP 28 RGE 08 BEG SE COR N1/2 SW1/4 NW1/4 SW1/4 TH W 180FT TPB TH N 180FT TH W 290FT M/L TH N 150FT M/L TO N LN SUB TH W 20FT TH S 150FT TH W 160FTTO W LN SUB TH S 180FT TO SW COR SD SUB TH EALG S LN SD SUB TO TPB LESS RDS & LESS R/W TO CITY OF SULTAN PER QCD AFN Size (gross) 2.02 To whom this may concern, On April 16, 2017 I visited the site at st Street in Sultan with the landowner to check for the presence of wetland identifying conditions. The site is an existing single family home with portions of the lot set aside for grazing in addition to the home and yard area. The site has a unique feature, defined in this topo map (below) from the Snohomish County map folio. An old historical swale in the center of the lot runs north to south with an elevation change of about 4 or 5 feet at the north line but only a few inches at the south. This preliminary site assessment included soil pits in areas of possible wetland conditions (hydric soils) based on the visual topography and vegetation. In this site the swale what attracts the first attention is the dense vegetation of buttercup (ranunculus repens). While the overall vegetation is FAC and FAC+ the soils do not bear any of the identifying criteria required for a wetland soil determination. Stacy MacGregor Sultan WA 1

71 The soils pits were dug in three locations, at the bottom of the swale, from north to south. There were no reducing features, concretions or the other features which would indicate anaerobic soil conditions required to define a wetland. Soil pit #1 near the North lot line 10YR 5/2, 4/2 to a depth of 14 Soils were sandy loam to silty loam Vegetation was limited to Ranunculus repens, Rubus armeniacus (an invasive species rooting throughout the swale) a Acer circinatum, a dead Alnus rubra, and a holly (Ilex ssp) which are found in within the lot also. Soil pit #2 mid lot near a debris pile 10YR 2/2, 3/1 to a depth of 14 No redox or reducing conditions were noted of any shade or color The matrix was consistent and even colored Vegetation did include a small shrub: Symphoricarpos albus, Prunus laurocerasus (invasive), holly (Ilex ssp)invasive. Also an Alnus rubra and Oemleria cerasiformis. No water was noted standing anywhere in the swale and the rains of the last days, weeks months have been record breaking throughout the winter. Soil pit #3 south lot line area / swale is less defined 2.5YR 3/1, 4/2 to a depth of 14 Consistent silty loam, dry and loose This south half of the lot had more native trees then the rest of the lot as well as several orchard trees. Pseudotsuga menziesii, Tsuga heterophylla, Thuja plicata were all trees present in the general area (though none rooting in the base of the swale. The main issues with this lot will be the elevation change and required grading to fill the site. It does not appear this has been an active flood channel at any time in modern history, and the soils are very well draining. Sultan City Code: Critical area study content requirements for streams or wetlands. This code defines the delineation of a wetland to be that system which identifies the edge of the wetland based on the State Manual for Identifying and Delineating Jurisdictional Wetlands. As such this site does not meet the criteria for a wetland. Stacy MacGregor Sultan WA 2

72 As added information This map indicates the low laying feature, while not 100% accurately mapped, this does portray the elevation change on the lot. NWI data Site: Off-site wetland related to the Sultan River to the west. Stacy MacGregor Sultan WA 3

73 Flood Hazard Data Snohomish County Lidar folio Site If you have any questions please feel free to contact me Kim Peterson Blue Heron Services Inc. PO 393 Index WA (o) (c ) bheron@seanet.com Stacy MacGregor Sultan WA 4