In the second phase of extensive wastewater system upgrades in Plainfield Charter Township, Mich., five pump stations were to be either rehabilitated or replaced. In addition to the pump station upgrades, the Scott Creek Trunk Sewer was to be replaced or rehabilitated from West River Drive to Pine Island Drive. Plainfield Charter Township is a large and growing community just north of Grand Rapids, Mich. It was imperative that these improvements were done quickly and efficiently to provide as little disruption to the surrounding community as possible.
The Problem
The existing trunk sewer line was a reinforced concrete pipeline with an increasing amount of infiltration and some sag in the pipe. The original U.S. 131 crossing also had significant pipe sag in it, causing velocities below design conditions that required it be replaced. A trunk sewer serves as the main artery for the wastewater collection system, and it is imperative for the entire system that the trunk line be able to collect and convey wastewater from numerous main sewer lines to a water quality treatment center without fail.
The Solution
Plainfield Charter Township used Contech Engineered Solutions’ gasketed PVC Truss Pipe for this replacement. Truss Pipe provides a semi-rigid wall design and quality in-ground performance. Given that Truss Pipe can withstand heights of cover greater than 40 ft yet also provide H-20 live loading with less than 1 ft of cover, Plainfield was reassured that this was a suitable solution and product for their particular project and site constraints. Not only that, but the newly installed Truss Pipe also provided a glossy smooth interior with a Manning’s “n” value of 0.009 that would reduce internal flow resistance and provide the hydraulic velocities required by the original design conditions.
The most significant element of this project was the crossing under U.S. 131 north of Grand Rapids. Each bore was completed from the wide median and was approximately 160 ft. The dewatering process for the bores was a concern for Michigan Department of Transportation (MDOT) due to the length and depth, so this required groundwater level monitoring. The polymer manhole in the median was 19.1 ft deep, and cover over the Truss Pipe at the deepest end of the casing was approximately 23 ft.
The Results
The project was a success in that the crossing was completed on grade with no settlement to the U.S. 131 pavement.
“The Scott Creek Trunk crossing under U.S. 131 was a success story for all parties involved: the township, the contractor and MDOT,” said Rick Solle, Plainfield Charter Township engineer. “MDOT had apprehension at the beginning of the project and required monitoring throughout the project of both the pavement elevation and the groundwater levels. The cooperation between the owner, contractor and MDOT throughout this process made a difficult project a huge success. Contech’s Truss Pipe offers us a premium sanitary sewer product to address all the concerns with deep interceptor installations. The pipe strength, joint quality [and] characteristics of PVC virtually eliminate all the long-term issues found with pipe options historically used in these applications.”
