The MPCA, in partnership with Carver County and the Environmental Protection Agency (U.S. EPA), conducted research on the ground water impacts at two compost sites.
The MPCA provided funding for the county to install monitoring wells and funding for a contractor to collect samples. The EPA provided lab services and analysis of the data collected. Carver County was involved in operating the compost sites and participated in the study design and implementation over the course of the project.
One of the compost sites accepts exclusively yard waste such as leaves, grass clippings and brush. The second site accepts source-separated organic material (SSOM), which includes food scraps and compostable products in addition to yard waste.
The information collected through this and past partnerships with Carver County has been used to inform the MPCA’s rules regulating compost sites. It has also helped the agency and industry refine testing requirements in place at compost sites.
Monitoring wells were placed adjacent to both compost sites and sampling was conducted quarterly from June 2017 through the end of 2018. A wide array of potential pollutants were evaluated, including pesticides & herbicides, SVOCs & VOAs, PFAS, BOD, Nitrate, TKN, Phosphorous, metals, total coliforms and E. coli.
The project's quality assurance project plan (QAPP) provides additional background and procedures that were in place to ensure reliable information was collected. The collected data is summarized in the memo for the Carver County Groundwater Sampling Results.
Next steps
Additional data are needed to better understand potential groundwater impacts at compost sites. Composters are likely to have different impacts on groundwater depending on the feedstocks they accept, their volumes, site operations, or site conditions (soils, pad types, depth to groundwater, etc.).
The agency hopes additional compost sites around the nation will conduct groundwater monitoring efforts to help gather this data. Future research may take place in Minnesota (at these sites or other sites) if funding is available or if partners gather the data.
For more information
Contact Tim Farnan, MPCA, 651-757-2348