2801 35TH AVE NE 2025-04-07 - Laserfiche WebLink

STORMWATER SITE PLAN 8/18/2023 SOUTHWEST STORAGE YARD 4 then north to a tide gate that controls the flow through the dike and discharges to the Snohomish River system.The local ditches provide for storage when high tides prevent the release of water through the tide gate. The Snohomish River is a 'flow control exempt'water and a 'basic water quality receiving' water body. MR 5: ON-SITE STORMWATER MANAGEMENT As the site is in the City of Everett and will be required to meet MR#1-9.The site also discharges to a Flow Control Exempt waterbody. As such, it can meet the LID Standard or use List#3. List#3 is proposed as described below: Runoff from the different site areas will be managed as follows: LAWN AND LANDSCAPED AREAS: BMP T5.13 Post Construction Soil Quality and Depth will be implemented on disturbed and landscaped areas. It is expected that most disturbed soil will be covered with new impervious. Imported topsoil will be used for those small areas where pervious surfaces need restoration. ROOF AREAS: No roof is proposed. PAVEMENT AREAS: Item#1: Sheet flow Dispersion/Concentrated Flow Dispersion There are no vegetated areas in which to disperse runoff. Immediately downstream of the site are the local ditches that provide for storage in conjunction with the tide gate system.This is infeasible. MR 6: RUNOFF TREATMENT REQUIREMENTS The site (non frontage) is proposed to have 30,600 sf of new impervious. In the future that will be a mixture of pavement and gravel.At this stage it will be an access up the slope of pavement with the balance of the site gravel.With more than 5,000 SF of pollution generating impervious surface the site requires runoff treatment. For the general site: Oil Control: The site does not meet the threshold of 100 vehicles per day/1,000 sf of building area. It will not store 25 or more vehicles over 10 tons and thus oil control is not required. Phosphorous Control: We have reviewed the 303d listings and Possession Sound has a Category 5 listing for Bacteria.The site will not be a source of Phosphorous pollution. Enhanced Treatment:The Snohomish River system is listed as a Basic Water Quality receiving water.Therefore, enhanced treatment will not be required. Therefore,the site will require Basic treatment levels. The site has been subdivided into two basins to account for flows to each direction of current flow. Storm water treatment of the site runoff will be accomplished using cartridge filter treatment systems by Contech Stormwater P.\work\Projccts\zozl\zl 162 sea con\CE\o06\ST0RMwATER SITE PLAN SMALL.docx