Northwest Interceptor Sewer Relocation
The reconstruction of the intersection at K-18 highway and US-77 Highway fell under these new regulations. Due to very large sewers laid at minimal grade, the project involved very deep tunneling, casing and excavation in order to meet the requirements of several agencies.
In order to meet regulations of the Kansas Department of Health and Environment, minimum sewer grades for various line sizes were required to meet minimum sewer flows. This required installation of a very deep sewer using tunneling operations in areas where normal excavation equipment couldn’t be used. That depth also led to issues with groundwater and stringent EPA standards.
We started with an overall topographical survey of the project area with the proposed interchange improvements superimposed on top of it. With this, we prepared preliminary alignments that would meet the requirements of KDOT and KDHE.
During the construction phase, groundwater was encountered that was not found during our geotechnical work. The groundwork required various means of handling to meet the discharge requirements of the EPA. The construction process involved a method that is not normally used in this area. During the construction, the contractor and our field engineers were continually engaged in addressing situations that came up during the process.
The final design yielded a construction project that would require contractors to use special equipment that would be able to tunnel through areas where the depth would exceed 80 to 100 feet. The depths would not allow the use of normal excavation equipment, so Kaw Valley Engineering provided in our design documents additional geotechnical work to define the soil, rock or shale strata that the tunneling operation would be in.
After some creative methods were developed, the contractor was able to successfully complete the tunneling operation at several locations. The additional capacity created by the larger pipe was more than enough to maintain the gravity flow without a major extension or pump station, and the reroute has successfully avoided influencing the interchange.
