Laserfiche WebLink
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 will be provided for under Section IV. <br /> MR#3 SOURCE CONTROL OF POLLUTION: Onsite BMP's will be used to <br /> minimize the source pollutant sources that include parts/vehicle cleaning, spills/leaks of <br /> fuel and other liquids, replacement of liquids, outdoor storage of batteries/liquids/parts, and <br /> vehicle parking. <br /> MR#4 PRESERVATION OF NATURAL DRIANAGE AND OUTFALLS: Runoff <br /> treatment will be obtained by a wetvault. <br /> MR#5 ONSITE STORMWATER MANAGEMENT: Per Minimum Requirement#5 <br /> (Section 1-2.5.5 of the SWMMWW), the following NPGIS BMP's shall be applied to <br /> provide onsite stormwater management and must be considered in the following order per <br /> List#2: Full Dispersion, Infiltration, Bioretention, Basic Dispersion, and then Perforated <br /> Stub-Out Connections. Full Dispersion is infeasible because of the steep slopes. Full <br /> Infiltration is cannot be achieved because of the steep slope of the site. Basic Dispersion is <br /> not feasible because the required vegetated flow path required by the BMP could not be <br /> met. Perforated stub-out is also not possible because of the steep slopes. Therefore, the roof <br /> drains will be connected directly to the onsite detention system. The following BMP's <br /> shall be applied to the other hard surfaces: Full dispersion, Permeable Pavement, <br /> Bioretention, and then Dispersion. Full dispersion, permeable pavement and Bioretention <br /> are not feasible because site contains steep slopes; the required setback could not be <br /> obtained. Basic Dispersion is not feasible because the required vegetated flow path could <br /> not be met. Post-Construction Soil Quality and Depth BMP T.5.13 is proposed to provide <br /> onsite stormwater management for the pervious areas of the site. The yard and roof drains <br /> will be connected towards an on-site detention system. <br /> MR#6 RUNOFF TREATMENT: Runoff treatment would be obtained by wetvault. <br /> MR#7 FLOW CONTROL: A 108'x 29.50'x 14' wetvault located underneath the open <br /> space near the central portion of the site is proposed to meet the flow control requirements <br /> conforming to the City of Everett requirements. The wetvault will have a detention depth of <br /> 9.50-ft, 3.50-ft of wetpool depth and 1-ft of sediment storage. The wetvault was sized using <br /> Western Washington Hydrology Model V 4.2.13 (WWHM). The roof and the yard drains <br /> will be connected to the onsite detention system. The outflow from the wetvault will be <br /> discharged to the east via a closed pipe system to a stilling basin for energy dissipation and <br /> Insight Engineering Co. -Stormwater Site Plan 07/03/2019 <br /> -4- <br />