County approves wastewater tunnel

September 2011, Vol. 66 No. 9

On July 14, the Johnson County, KS, Board of Commissioners authorized construction of an underground effluent pipe between the treatment plant to a discharge point on the river.

The total authorization for the Mill Creek Regional Wastewater Treatment Plant Effluent Capacity Improvements was increased by $37.8 million to $41.6 million by the board.

In a related action, the board approved a contract totaling nearly $32 million with S.J. Louis Construction of Texas to construct the effluent tunnel.

The project will span approximately 9,800 feet, almost two miles, with a concrete pipe with a 96-inch diameter. The tunnel will be buried approximately 100 to 110 feet and require boring under portions of streets and railroad tracks.

Treated plant effluent will flow by gravity through the tunnel to the Kansas River. Plant effluent currently is pumped to the same discharge location, but the pumping station does not have the capacity to pump extreme wet weather flows. The pumping station will be taken out of service after completion of the project, which includes construction of new plant piping to convey treated wastewater from the plant's final stage lagoon to the tunnel.

"What the tunnel does do is reduce our carbon footprint and operating costs since we will not need electricity to pump the effluent as we do now," John O'Neil, general manager for Johnson County Wastewater, said. He estimated the project, once completed, would save more than $200,000 annually in moving ultimate future flows.

Construction of the tunnel is expected to begin by late summer with completion by late 2013.