The Beaver Bay, Minn., water treatment plant—on the north shore of Lake Superior—was in need of remediation work in order to resolve a nearly 17-year-long issue related to the leakage of approximately 500 gallons of fuel oil from an on-site tank, which subsequently made its way into the plant wet well. Prior attempts to isolate the wet well contamination had been ineffective, with residual fuel oil continuing to infiltrate the well and treatment plant— a facility not designed to remove petroleum hydrocarbons.
When the file for the case was most recently re-opened by the Minnesota Pollution Control Agency (MPCA), MSA worked to engineer a new and lasting solution. The goal was to eliminate drinking water impacts to the City of Beaver Bay municipal water supply by preventing contact between drinking water acquired from Lake Superior with the residual soil and groundwater contamination existing beneath the water treatment plant—specifically concentrated around the existing wet well.
MSA completed site investigation work including the advancement of several soil borings and the collection of soil, groundwater and drinking water samples to help define the extent of contamination at the site. Once the site investigation was completed, a Conceptual Corrective Action Design (CCAD) report was prepared, delineating the following project tasks:
- Construction of an access road to the proposed wet well pump house.
- Installation of a new, pre-fabricated Minnesota Department of Health (MDH)-approved wet well tank.
- Construction of an associated pump house near the isolation valve location.
- Installation of a new, insulated water line from the pump house to the water treatment facility.
- Sealing of the existing wet well and intake line to the location of the isolation valve.
- Water monitoring of the Beaver Bay water treatment plant water to evaluate the effectiveness of the new system.
Quality solutions, quality water.
Replacement of the wet well, piping and filter media reached the desired outcome, eliminating the petroleum impacts that had long been an issue at the treatment plant. The property is now considered remediated, a status that eliminates the potential for future petroleum contamination and confidently provides the citizens of Beaver Bay with dependable, high-quality drinking water for generations to come.
City of Beaver Bay
Beaver Bay, MN
Jeff Anderson, PE
Environmental Team Leader