9900 19TH AVE SE WINCO FOODS 2025-03-27

Brandon Johnson From: Brandon Johnson Sent: Wednesday, January 5, 202212:56 PM To: 'Enk Emerson' Cc: 'Heather Griffin' Subject RE: [EXTERNAL] RE: WinCo drainage report Aft chments: 116.003-UT-EXH-Layout1.pd1:, 200271-T-24x36-1SA MARKUP.pdf Erik / Heather, I hope the Holidays treated you well I We have been diligently working behind the scenes on the stormwater Issue since we met. We have CM'd the lines that we were capable of [[Wing, completed some survey, then completed some more survey and recreated a high-level stormwater model of the entire system. Here is a quick recap of what we've found so far. • Construction Issue No. 1: The lower pond overflow was set above the rim of one of the CB's in 16v' Avenue. The result is when that pond hits capacity, which is fairly frequently due to previous design standards, stormwater bubbles out of the 16" Avenue structures before it enters the overflow system. • Construction Issue No.2: The upper pond overflow was set above the east end of the concrete retaining wall along 10& Avenue. The result is that when the pond hits capacity, which again is fairly frequently, the stormwater does not utilize the Intended pond overflow but rather runs down to 16" and further Inundates the lower pond. • Construction Issue No.3: The outfall in the NW corner of the site was installed 4' above the original design elevation, which obviously greatly limits the outlet capacity of the system. • Design Issue: Based on our initial high-level stormwater modeling, the enti re outfall system appears to be undersized (even if it would have been installed correctly). With the HGL of the system pushing water out of the system via the lowest CB's in the Boy Scouts parking lot. I've attached a markup of the survey showing these issues In a graphic as well as an exhibit we prepared showing the profiles of the existing system. My hope is you could take sometime to review these documents/this email and then we could set up a time to meet virtually or in -person to discuss further. Thankyoul Brandon Johnson, PE I Principal JSA I CIVIL 6945 Littlerock Road SW, Suite A Tumwater, WA 98512 m. 360.269.6346 brandon.johnson@jsa-civil.com