3620 36TH PL NE 2023-06-22 - Laserfiche WebLink

Stormwater Pollution Prevention Plan 2.0 Site Description 2.1 Existing Conditions The majority of the site is open grassed areas with scattered shrubs and small trees. A private drive (36th PINE) bisects the site to provide access to Cedar Grove Composting. An existing Iconcrete batch plant operated by Concrete Norhwest is located on parcel number 29050500400200. Union Slough is located along the northern edge of the property. An existing drainage ditch along the south property line drains west and discharges into Steamboat Slough. The site is relatively flat with the majority of stormwater infiltrating into the soil. Excess runoff north of 36th PI NE drains north through a drainage swale into Union Slough. Runoff from the south portion of the site enters the existing drainage ditch and flow west to Steamboat Slough. Runoff from the site ultimately discharges into the Possession Sound via the Steamboat and Union Sloughs. 2.2 Proposed Construction Activities The proposed project involves the grading and filling of the parcels for future development. The proposed construction will occur in phases to accommodate operation of the existing facilities and to minimize the potential for water quality impacts. Phase 1 will place fill along the north property line and extending south along the west side of the BNSF ROW to 36th P1 NE. Fill will also be placed along the southern edge of the property. Fill placed at these locations will create berms that will enable the construction of the Mitigation areas. It will also create a contained work area inside of the berms that will minimize potential for erosion. A culvert will be extended from the existing 24-inch culvert with tide gate and will provide drainage from inside the facility through the berm to the existing discharge location into Union Slough. Material from an existing stockpile in the southeast corner of the site shall be used for fill during Phase 1. Compost/mulch (BMP C 121) and seeded mixes (BMP C 120) will be placed on all outer slopes. Upon establishment of vegetation, the wetland mitigation plan shall be implemented. Phase 2 will place fill within the interior of the site both north and south of 36th PINE. A type II catch basin will be installed at the end of the culvert to be installed in phase 1. A temporary culvert extendingfrom thetype II catch basin to the Concrete Northwest plant shall be installed to allow storm drainage to flow from the existing concrete plant. A temporary access road will be constructed north of the existing drive in preparation for Phase 3. Phase 3 will remove the existing drive and place fill to the finished grade elevation. Watermain casings under the future tracks and extensions of the watermain valves and hydrants will occur at this time. SWPPP Page 3 Smith Island Terminal—Site Grading March 2017