Sewer Shenanigans: A Deep Dive into Wichita’s 78-in. Interceptor Relocation

In 1964, a segment of Interstate 135 (I-135) in Wichita, Kansas, was constructed directly over an existing 78-in. and 60-in. sanitary sewer serving Wastewater Treatment Plant No. 1 (WWTP No. 1). Rather than adjusting the sanitary sewer manholes to grade at the travel lanes and shoulder along I-135, the manholes were altered to offset designs, making access difficult and dangerous for City of Wichita (City) staff. Consequently, various alternatives were analyzed to reroute the interceptor from WWTP No. 1 to Blake Street. The selected alignment faced challenges with an existing drainage system and required tunneling through granular material. The interceptor crossed the Kansas Department of Transportation (KDOT) right-of-way between drilled piers and a KDOT-maintained drainage system. Since the drainage system could not be relocated, a siphon was designed to maintain wastewater flow. This paper will go over the alignment alternatives, trenchless considerations, siphon, and air jumper design.