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Multi Lake Water and Sewer Authority Wastewater Treatment Plant (Dexter, Washtenaw County)

Disclaimer: Web content may not be routinely updated on this page.

Please contact the Site Lead for the most up-to-date status of this site.

Disclaimer: Public and private municipal wastewater treatment plants do not produce or use PFAS.

These plants receive residential, commercial, and sometimes industrial wastewater that may contain PFAS. Conventional wastewater treatment plants are not designed to treat for PFAS, therefore PFAS may pass through the treatment system to surface waters (i.e., lakes, rivers, etc.) and groundwater. EGLE is actively working with these wastewater treatment plants to address PFAS. 

For more information, please see the Wastewater Workgroup page.

EGLE site lead

Sydney Ruhala, or 517-599-5356.


The Multi Lake Water and Sewer Authority Wastewater Treatment Plant (WWTP), located at 12088 North Territorial Road, accepts residential and some commercial wastewater, and discharges treated wastewater to the groundwater under a State Groundwater Discharge Permit issued to the Multi Lake Water and Sewer Authority. Wastewater is treated using an oxidation ditch process and the final treated effluent is discharged to the groundwater onsite via rapid infiltration basins (i.e., sand beds). As part of a compliance strategy for addressing PFAS from public and private municipal groundwater discharges, EGLE sampled the WWTP's influent, effluent, and three downgradient groundwater monitoring wells for PFAS on October 31, 2022. PFOA was detected in all three monitoring wells above criteria. The highest result was 22.2 ppt PFOA (compared to 8 ppt).

Estimated groundwater flow direction near the rapid infiltration basins is generally to the east/southeast, however on the north side of the rapid infiltration basins estimated groundwater flow direction is to the north/northwest.

Content posted June 2023.

Site map

See an aerial view of the location of the site.

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Drinking water

On February 21, 2023, the Multi Lake Water and Sewer Authority sampled one Type III drinking water well on the south side of the WWTP property. PFAS was not detected in the well. In April 2023, 3 downgradient test wells and one residential well were sampled. PFAS was detected in all 3 test wells below criteria. PFAS was not detected in the residential well.

EGLE, DHHS, and local health will be conducting an initial phase of residential well sampling in Summer 2023. Selected residents will receive access agreements in the mail. Residential well sampling will be expanded in a phased approach if determined to be necessary.

Anticipated activities

EGLE will continue to work with the Multi Lake Water and Sewer Authority to determine the extent of PFAS contamination in groundwater and work to identify, and reduce where possible, potential sources of PFAS to the WWTP.