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5 � <br /> EAST SUB-BASIN <br /> Level 1 Downstream Drainage Analysis: <br /> Section 1: Upstream Drainage Analysis: <br /> Based on the site contours there is no upstream runoff draining onto the site. <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 east side of the site draining onto the catch basin storm <br /> systems serving Lower Ridge Road <br /> Section 3: Site to Lower Ridge Road to Pidgeon Creek#2 <br /> The runofffrom the site leaves the property along the east side draining into the catch basing located at <br /> the south-west corner of the site on Lower Ridge Road. From here storm pipe crosses the roadway and <br /> continues east in the storm pipe for about 200 feet before flowing into Pidgeon Creek. From here the <br /> creek flows north crossing under several streets and along the back yards of residential homes and <br /> continuing north for over 1-mile. <br /> There appeared to be no issues with the downstream drainage system or culverts. Where visible,the <br /> stream channel was well vegetated. However,nearly the entire downstream course was on private <br /> property and not accessible to inspection. <br /> TASK 5: LEVEL 1 MITIGATION OF EXISTING PROBLEMS <br /> The project proposes to mitigate the proposed site improvements through the use of LID measures <br /> including Splash Blocks requiring minimum of 50-ft flow paths through vegetation and driveway <br /> dispersal trenches. <br /> Conclusions: <br /> Based on the proposed mitigation and lack of problems noted downstream,the site development should <br /> have little if any impact on west side downstream conditions. <br /> 7030 Lower Ridge RD Full Drainage Report <br /> Revised:November 3,2017 Page 7 <br />