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2014 SWMMWW MINIMUM REQUIREMENTS SUMMARY <br /> MR : MINIMUM REQUIREMENT <br /> SSP : STORMWATER SITE PLAN <br /> MR#1 PREPARATION OF STORMWATER SITE PLAN: <br /> Stormwater site plan follows 2014 Stormwater Management Manual for Western <br /> Washington. <br /> MR#2 CONSTRUCTION OF STORMWATER POLLUTION PREVENTION <br /> PLAN (SWPPP): A SWPPP is provided under Section IV. <br /> MR#3 SOURCE CONTROL OF POLLUTION: N/A. No source control pollutants <br /> pertains to the proposed project,therefore no BMP's are required for the proposed project. <br /> MR#4 PRESERVATION OF NATURAL DRAINAGE SYSTEMS AND <br /> OUTFALLS: The developed site drainage will be discharged to the east of the site to <br /> follow the natural drainage course of the site. <br /> MR#5 ONSITE STORMWATER MANAGEMENT: Per Minimum Requirement#5 <br /> (Section I-2.5.5 of the SWMMWW),Post-Construction Soil Quality and Depth BMP <br /> T.5.13 is proposed to provide onsite stormwater management for the lawn and landscaped <br /> areas of the site. The following NPGIS BMP's shall be applied for roof to provide onsite <br /> stormwater management and must be considered in the following order per List#2: Full <br /> Dispersion, Bioretention, Downspout Dispersion, and then Perforated Stub-Out <br /> Connections. Full Dispersion is infeasible because the required native vegetation <br /> preservation could not be achieved for the nature of the project. Bioretention is not feasible <br /> because of the poor quality of the soil. Downspout Dispersion is not feasible because the <br /> required vegetated flow path required by the BMP could not be met. Perforated stub-out is <br /> also not possible because of the steep slopes. Therefore the roof drains will be connected <br /> directly to the onsite detention system. The following BMP's shall be applied to the other <br /> hard surfaces: Full dispersion,Permeable Pavement,Bioretention, and then Dispersion. <br /> Full dispersion,permeable pavement and Bioretention are not feasible because the onsite <br /> soils that contain"low infiltration capacity". Basic Dispersion is not feasible because the <br /> required vegetated flow path could not be met. The yard and roof drains will be connected <br /> towards an on-site detention system. <br /> MR#6 RUNOFF TREATMENT: Runoff treatment would be obtained by an <br /> underground Biopod Biofilter manufactured by Oldcastle Infrastructure located <br /> downstream of detention to provide enhanced water quality treatment for the commercial <br /> project. Oil Control treatment is not applicable for this project as this is not a high use site, <br /> average daily traffic (ADT)is less than 100 per 1,000 SF of gross building area and has <br /> less than 25 vehicles that are over 10 tons gross weight(trucks,buses, trains,heavy <br /> equipment, etc.). The Japanese Gulch creek is not even listed under 305(b) assessment list. <br /> Hence Phosphorus Control is exempt. <br /> Insight Engineering Co. -Stormwater Site Plan 11/27/18 <br /> -5- <br />