WLSSD, Duluth, MN – Secondary Clarifier Rehabilitation

Project: Secondary Clarifier Rehabilitation

Owner: Western Lake Superior Sanitary District (WLSSD)

Value: $3.9 million | 6-month, accelerated schedule

Scope of Work: WLSSD treats wastewater for more than 140,000 people, making it the single largest source of discharge on the U.S. side of Lake Superior. With an average daily flow of 40 million gallons into a river that feeds Lake Superior, WLSSD wanted assurances the project would be done right the first time. Lakehead hired an outside contractor to provide full-time inspection, testing and construction monitoring to ensure work was performed to the exacting standards outlined in the project documents.

Work began in June of 2019 and was substantially completed by December 2019. The accelerated schedule was necessary to prevent freezing and upheaval of the structure, as well as to minimize the time WLSSD would have 25 percent of its secondary clarification taken out of service. Scope of work included, but was not limited to: demolition of existing concrete launder troughs, water blasting and shotcrete resurfacing of interior walls, reshaping of exterior grades, and installation of new stainless steel launders, weirs, scum baffles and drip flashings. In all, approximately 15,000 sq feet of shotcrete was applied at an average thickness of 3 inches to the clarifier’s 19-foot-high sidewalls.