404 14TH ST BASE FILE 2024-12-09

2. PROJECT DESCRIPTION 2.1. EXISTING CONDITIONS The existing fuel tanks scheduled for replacement are located in an underground concrete vault underneath asphalt parking stalls and drive lanes, (Location A).The tanks are located between an existing upland boat storage facility and the Milltown Sailing Association building.The site is mostly covered by asphalt and gravel with some nearby landscape areas between parking stalls.The site generally drains to the southwest to an existing catch basin and underground conveyance system,which discharges through an existing outfall on the west end of the site to the Snohomish River. The fuel tanks are being reconstructed in a new location (Location B),approximately 250-feet south of the existing tanks,closer to the 14,h Street bulkhead.Location B is in an existing asphalt parking area for marina tenants.This area drains to an existing catch basin and underground conveyance system, discharging to the south into the Central Marina (Snohomish River). Per the site geotechnical report,the project soil conditions consist of sand,silty sand,and sandy silt,refer to Appendix D for the geotechnical report. Groundwater conditions at the site are known to be tidally influenced. Groundwater is anticipated to be between 3-5 feet below the existing ground surface. 2.2. PROPOSED CONDITIONS The proposed conditions at the end of this Marina Fuel tank project represent an interim condition for the larger Waterfront Place Central (WPC) development.The phasing of the WPC project and this Marina Fuel tank project is such that the future roadway construction of Millwright Loop,Sawyer Street and Woonerf Street within the WPC development will provide the new stormwater conveyance and treatment systems in compliance with the 2019 SWMMW W.The finished condition after the Fuel Tank replacement project will be restored to an interim condition where the public can still access the site before the WPC project constructs the proposed development and site improvements.A description of the proposed interim conditions are as follows: At Location A,6,077 square feet of existing asphalt will be removed and replaced with gravel for continued vehicular access around the Port and parking after this project is complete. The existing asphalt parking areas will be restored with gravel until the WPC development repurposes this area. At Location B,719 square feet of asphalt will be removed and replaced with new asphalt to facilitate the piping and electrical connections from the new fuel tanks to the fuel dock. 12,068 square feet of asphalt will be removed and replaced with gravel in the vicinity of the fuel tanks.The grade around the fuel tanks is being raised approximately 2'-3'to account for the future roadway and parking lot grades in the WPC project. 3. CONSTRUCTION STORMWATER POLLUTION PREVENTION PLAN A construction stormwater pollution prevention plan (SWPPP) has been prepared for this project and is included in Appendix B.The SWPPP is prepared following the guidelines in the SWMMWW Volume II. Execution of the SWPPP during construction will be the responsibility of the Contractor. 4. HYDROLOGY Currently,the site is covered with mostly impervious surfaces (gravel and asphalt).The total area within the project limits is 1.34 acres and the total disturbed area is 0.43 acres.Location A and B are located within 1 TDA,bust separate sub drainage basins discharging to separate existing conveyance systems.The proposed ® ® 0