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6. Downstream Analysis <br /> The downstream for this project starts with sheetflow from the northern portion <br /> of the lot entering into the 63rd Street Storm System through a Type 1 CB that <br /> is in the center of the lot. This 12" storm line runs east in 63rd <br /> There may be a small amount of sheetflow from the southern portion of the lot <br /> that sheetflows off-site to the east. Any sheetflow off-site would sheetflow east <br /> and north through neighboring lots until it is intercepted in the Olympic Drive <br /> Street drainage system. This system flows northeast to 63rd where the flow <br /> joins the flow along 63rd about 245' east of the site. The combined system <br /> flows east in 63rd about another 1,045' where it joins the street system flowing <br /> northeast in Beverly Blvd. The pipe size in Beverly changes from a 15" to an <br /> 18" culvert at this point. Flow travels about 145' NE where it turns to the east <br /> and then south in the Wetmore Ave Street Drainage system still having an 18" <br /> diameter. This is over % mile from the site. <br /> Given the potential downstream drainage impact of the small amount of flow <br /> increase from the roof the downstream drainage facilities appear to be <br /> adequate to accommodate flows from the development activity and all other <br /> upstream sources identified by the threshold discharge area on-site. <br /> The analysis does not include any proposed mitigation beyond use of LID <br /> techniques on-site as no significant drainage impacts from the development or <br /> redevelopment activities were identified in the upstream or downstream <br /> analysis. <br /> The proposed drainage facilities are designed so that stormwater enters and <br /> exits the site at the existing location(s) for entry and exit <br /> 7. Flow Control Threshold Evaluation & Developed Site Hydrology <br /> As the proposed new and redevelopment PGIS area of 1,033 Sf is less than <br /> 5,000 Sf MR6 does not apply and does not require structures for water quality <br /> treatment. LID BMP T5.12 will address flows for the PGIS. <br /> As the overall new and replacement impervious area of 3,587 is less than <br /> 5,000 Sf all impervious is to be addressed with BMP's. BMP T5.12 and BMP <br /> T5.10C were selected to direct sheetflow and roof flows to areas where flows <br /> are currently. <br /> Kravchuk Targeted Drainage Plan Page 6 <br />