South Washington County Waste Water Treatment Plant
Cottage Grove, Minnesota
Black & Veatch
20,000 sq. ft.
Located on the bluffs above the Mississippi River, the new South Washington County Wastewater Treatment Plant was a study in careful planning. Because of land constraints, the new plant had to be constructed in tight quarters and on the same site as the existing facility. Adding to the challenge: the old plant had to remain in operation until the new plant came on line.
The first phase of the project involved construction of a new liquid train treatment process right next to the existing plant. Once it was complete and all processing equipment was installed, the new facility went on line. The old facility was then demolished and construction of phase two began, including new operations, maintenance buildings and a new solids handling facility.
To meet the demands of community growth, the Metropolitan Council knew it needed to replace its 2 million gallons per day wastewater treatment plant. The new facility can process 10 million gallons per day and consists of several large, open, reinforced concrete tanks requiring more than 12,000 cubic yards of concrete.
An interesting aspect of the project was the installation of an “outfall” line extending from the top of the river bluff out into the Mississippi River. The outfall brings the treated water from the plant to the river and included the installation of a 70-foot vertical shaft down to river level, a 400-foot tunnel to the river’s edge and the installation of more than 1,500 feet of piping installed below the river bed and out into the navigational channel.