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C. Floodplain/Floodway(FEMA Maps):Does not appear to be located within the flood plain of <br /> the stream as determined by the FEMA maps. <br /> D. Other Off-Site Analysis Issues: None Noted <br /> TASK 3 & 4: FIELD INSPECTION AND DESCRIPTION OF DRAINAGE SYSTEM WITH <br /> EXISTING AND PREDICTED PROBLEMS <br /> A Level 1 drainage analysis and"Off Site Analysis and Mitigation Study"meeting requirements outlined <br /> in Section 3.2.0 was performed.See Downstream Analysis Map. <br /> Level 1 Downstream Drainage Analysis: <br /> Section 1: Upstream Drainage Analysis: <br /> Based on the site contours all upstream off-site runoff is intercepted by Rainer Drive.Therefore,the <br /> upstream runoff entering the site is minimal and limited to the site itself.. <br /> A review of the upstream area indicated that there were no indications of problems observed. <br /> Section 2: On-site Drainage Considerations: <br /> All runoff from the site discharges along the west side of the property into the existing drainage ditch. <br /> Section 3: Site to Hwy 99 <br /> The runoff from the site leaves the lot along the west side and discharges existing drainage ditch. <br /> From here it flows north and crosses under 75th Street SE in an 18"culvert. From here the drainage <br /> is on private property but appears to flow north,then turns and flow the east in a storm pipe system <br /> into the drainage system on Hwy 99,and continues flowing north 3/4 of a mile. <br /> There appeared to be no issues with the downstream drainage system or culvert. However,most of <br /> the downstream course was on private property and not accessible to inspection. <br /> With the small size of the project at just under a total of 5,000 sf,and the use of proposed LID <br /> measures using a dispersal trench,the proposed site improvements should have little if any impact on <br /> downstream conditions. <br /> TASK 5: LEVEL 1 MITIGATION OF EXISTING PROBLEMS <br /> Dispersal trench through vegetation. <br /> Water Quality Requirements: <br /> With less than 5,000 sf of PGIS area,water quality is not proposed for the site improvements. <br /> However, stormwater from the site and driveway will be dispersed via permeable pavement. <br /> Conclusions: <br /> Based on the existing mitigation and lack of problems noted downstream,the site development should <br /> have little if any impact on downstream conditions.. <br /> Kymera 2-Lot SP Full Drainage Report <br /> Revised:April 21,2018 Page 5 <br />