Lakeshore Natural Resource Partnership (LNRP), Stantec Consulting Services, and the University of Wisconsin – Stevens Point (UWSP) are working on a design for water quality treatment along Pine Creek, a direct tributary to Carstens Lake. The project was initiated as a result of a three-year study, conducted by the Manitowoc County Lakes Association (MCLA) between 2012-2014, which identified high levels (>40 ppb) of phosphorus in Carstens Lake.

LNRP secured a DNR Lake Management Planning grant to provide the necessary framework for water quality improvement projects in Carstens Lake – a 21 acre seepage lake in a 767 acre watershed. Improvements to land use practices to reduce phosphorus and other nonpoint source pollutant inputs are underway; however, additional work was needed to improve Carstens Lake water quality. Carstens Lake remains among the most impaired waters in Manitowoc County due to excessive phosphorus levels and anoxic (oxygen-deprived) conditions.

The subsequent 2018 Carstens Lake Comprehensive Management Plan recommended several structures adjacent to Pine Creek for water quality treatment to mitigate phosphorus loading in Carstens Lake. Our team recommended both adjacent wetland structures and a sedimentation basin that could capture peak flows of water carrying sediment and phosphorus. Working with the landowner, Hillside Dairy, construction of wetland scrapes commenced in late September 2023 and was completed in October 2023 by Madson Tiling & Excavating. Wetland scrapes are a series of shallow pools that help improve habitat quality. Stantec installed a cover crop (oats and annual ryegrass) directly following construction and native seed was planted during the dormant season. Native plant plugs will be installed in June.

Construction of the sedimentation basin adjacent to the creek is planned for late summer 2024. This will reduce high stream flows and allow suspended solids and nutrients to settle in the basin. Secondary treatment will be provided by implementing sorption technology in the outlet berm that will capture phosphorus prior to it reaching Pine Creek and eventually Carstens Lake.  The sorption technology, developed by Professor Kyle Herrman at UWSP, uses small porous bags with a sorption medium to remove dissolved phosphorus from the water stream.

The sorption medium was initially proposed to be industrial slag but UWSP shifted to Phosflow in late 2023. This product was developed in partnership with the US Environmental Protection Agency to create a medium that would permanently bind available phosphorus to improve water quality. Made from naturally occurring and sustainable mineral materials, the sorptive material is non-hazardous, insoluble in water, and non-toxic to aquatic plants and wildlife.

Water from Pine Creek will flow through the basin installed with porous bags that are lightweight (1 bag = 6 lbs), and have a very short contact time of just minutes to capture soluble phosphorus. The cost is moderate at approximately $700 for the 20 bags that will be installed. The DNR approved a field application at Lost Creek for June 2024 that will provide additional data and information for the Carstens Lake Water Quality Improvement Project.

With positive testing results, this project could introduce a low-cost tool that will provide additional phosphorus removal for Carstens Lake and has the potential to help other lakes in Manitowoc County.