Relief Well Systems Evaluations Mark Changes for Kansas City, MissouriPosted on Wednesday, March 13th, 2019 by Jason Davis
In Federal Services, Stormwater, tagged in Tags: relief wells, underseepage memo, usace
The City of Kansas City, Missouri’s Water Services Department (KCWS) asked Affinis to evaluate four relief wells that were part of the East Bottoms Relief Well System. Originally, KCWS requested relief well replacement design. However, after initial review Affinis determined the relief wells could be abandoned. This saved the city a few hundred thousand dollars in new replacement wells, as well as the cost for perpetual relief well maintenance.
We were familiar with this levee, because we had recently performed the Levee Periodic Inspection (PI) for East Bottoms. Our experience with the site helped us determine conditions had changed since the relief wells were installed. During the PI process, we researched the levee design documents and as-built plans to become familiar with the levee system. As part of this research, we noticed that over the years several feet of fill had been added during construction of the KCP&L plant. Essentially, an underseepage berm had been constructed that helped control the underseepage risk. We obtained a topographic survey to confirm the additional fill was placed. We then performed an underseepage analysis using the United States Army Corps of Engineers’s (USACE) new underseepage memo and determined the relief wells could be abandoned.
It was during the initial evaluation that we found the wells were no longer required. By comparing the existing elevations to the 1970’s as-builts, we could see significant fill had been placed over the years. That analysis was reviewed by the USACE-KC. They agreed with our analysis, which translates to a large cost savings for the city. They saved on not only the replacement, but also the ongoing maintenance.
Our review also determined the KCP&L recycle canal needed to increase the water surface elevation during flood events. Affinis created an Interim Risk Reduction Measure (IRRM) plan that includes step-by-step details and trigger elevations, along with the required material and equipment lists. It allows Kansas City, Missouri to quickly implement the “Big Bag” system during a flood event. The Big Bag system is a large sandbag versus the small traditional sandbags. The advantage of the Big Bag system is that equipment can place fewer large bags versus many small sandbags placed by hand, which is labor and time intensive.