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STORMWATER SITE PLAN <br />NOVEMBER 7, 2019 <br />COMPASS HEALTH SUPPORTIVE HOUSING <br />MR 3: WATER POLLUTION SOURCE CONTROL <br />CONSTRUCTION STORMWATER BMPs <br />Construction BMP's will follow the Storm Water Pollution Prevention Plan. <br />PERMANENT SOURCE CONTROL BMPs <br />Applicable permanent source controls will be as follows: <br />• Container storage of wastes. The containers shall be covered and maintained to prevent <br />storm water from entering and leaks from occurring. <br />• Vegetative maintenance. The planter areas shall be kept clean of debris. <br />• Storm system maintenance. <br />MR 4: PRESERVATION OF NATURAL DRAINAGE <br />The site is in the Combined Sewer area of Everett. A separate connection will be made to the <br />sewer system for the storm line for future connection to a separate storm system. <br />MR 5: ON -SITE STORMWATER MANAGEMENT <br />As the site is located in the Everett UGA and will be required to meet MR's #1-9, therefore it is <br />required to use List #2 or meet the Low Impact Development Performance Standard. List #2 is <br />the proposed method of meeting MR #5. Runoff from the different site areas will be managed <br />as follows: <br />Pavement Areas: <br />Full Dispersion: Is infeasible due to previous development. <br />Pervious Pavement: The project lies in Till soils of which the geotech report says "the glacial till <br />that underlies the site is very dense, has substantial silt content, and is essentially <br />impervious. For these reasons it is not feasible to utilize stormwater infiltration for this <br />project". The building will have cuts of up to 14 feet into the Till for the basement/daylight <br />level. Access walks to the sidewalk along Lombard Avenue will be right above this cut. Any <br />water infiltrated is going to end up in the footing drains and flow uncontrolled to the <br />combined sewer system. The same is true for the courtyard area which will be constructed <br />at the first floor elevation on fill materials. Any infiltration will again appear in the footing <br />drains and into the combined sewer uncontrolled. For these reasons it is felt that pervious <br />pavement for the walks and courtyard is unwarranted. <br />Bioretention: See the text for pervious pavement above. The same reasoning applies to <br />bioretention. <br />Sheetflow dispersion and Concentrated Flow Dispersion: There is no native growth area in <br />which to disperse runoff. <br />PAGE 9 <br />P:\Work\P:ro,jects\2017\17-125 Environmental Works\CE\DOCS\Final SSP 17-125.doc <br />