7102 LOWER RIDGE RD 2018-07-25 - Laserfiche WebLink

z TASK 3 & 4: FIELD INSPECTION AND DESCRIPTION OF DRAINAGE SYSTEM WITH EXISTING AND PREDICTED PROBLEMS A Level 1 drainage analysis and "Off Site Analysis and Mitigation Study"meeting requirements outlined in Volume 1, Section 3.1.3 of the 2014 DOE SWWM Manual was performed. See Downstream Analysis Map. Level 1 Downstream Drainage Analysis: Section 1: Upstream Drainage Analysis: Based on the site contours there is no upstream runoff draining onto the site. A review of the upstream area indicated that there were no indications of problems observed. Section 2: On-site Drainage Considerations: All runoff from the site discharges along the east side of the site draining onto the catch basin storm systems serving Lower Ridge Road Section 3: Site to Lower Ridge Road to Pidgeon Creek#2 The runoff from the site leaves the property along the east side draining into the storm system serving Lower Ridge Road.From here it flows north in the storm system for about 200-feet before flowing into Pidgeon Creek.From here the creek flows north crossing under several streets and along the back yards of residential homes and continuing north for over 1-mile. There appeared to be no issues with the downstream drainage system or culverts. Where visible,the stream channel was well vegetated. However, nearly the entire downstream course was on private property and not accessible to inspection. TASK 5: LEVEL 1 MITIGATION OF EXISTING PROBLEMS The project proposes to mitigate the proposed site improvements through the use of LID measures including Splash Blocks requiring minimum of 50-ft flow paths through vegetation and driveway dispersal trenches. Conclusions: Based on the proposed mitigation and lack of problems noted downstream,the site development should have little if any impact on west side downstream conditions. 7102 Lower Ridge RD Full Drainage Report Revised:November 3,2017 Page 5