7030 LOWER RIDGE RD 2018-07-25 - Laserfiche WebLink

x r 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. WEST SUB-BASIN 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 west side of the site draining onto the adjacent property Section 3: Site to Sievers Deucy Blvd to 60th Street SW The runoff from the site leaves the property along the west side draining onto the adjacent property. It then turns north flowing through an industrial vacant property and appears to flow under Sievers Deucy Blvd and through a gravel operation for a total distance of over 6,000 sf. There appeared to be no issues with the downstream drainage system or culvert. 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. 7030 Lower Ridge RD Full Drainage Report Revised:November 3,2017 Page 5