MPCA seeks comments on revised water quality standard for Spring Lake in Scott County

Contact: Alexis Donath, 651-757-2312

St. Paul, Minn. — The Minnesota Pollution Control Agency (MPCA) is inviting the public to comment on a revised water quality standard proposed for Spring Lake in Scott County. The proposed water quality target is specific to this lake, and is meant to address problematic levels of nutrients — specifically phosphorus — in the lake.

Spring Lake is located in the city of Prior Lake and Spring Lake Township. It is popular for recreation and fishing. However, because of its excess phosphorus levels,Spring Lake suffers from algal blooms and diminished clarity, which makes the lake less suitable for recreation.

MPCA staff are proposing a site-specific water quality target for Spring Lake because of new information about historic in-lake phosphorus concentrations dating back nearly 200 years.

The Prior Lake-Spring Lake watershed district conducted a lake sediment core study, which revealed that historic total phosphorus levels in the lake were approximately 60 micrograms per liter even prior to European settlement of the area in the mid-1800s, which led to significant changes in land use. In response to this study, MPCA staff believe it is reasonable to treat this concentration of phosphorus as a natural background condition and, therefore, the best phosphorus level that this lake could be expected to achieve.

In 2011, prior to the lake sediment core study, the U.S. Environmental Protection Agency (EPA) had approved a water quality study for Spring Lake based on the more stringent existing water quality standard for phosphorus, which is 40 micrograms per liter. This study, known as a Total Maximum Daily Load, or TMDL, calculates the maximum amount of pollutants a water body can tolerate without exceeding water quality standards.

If EPA approves this site-specific standard, the TMDL will need to be revised, since less stringent pollution load reductions will be needed for Spring Lake. However, MPCA staff conclude that if the new standard is adopted and water quality in Spring Lake meets the standard, the lake will be suitable for recreational use.

A public informational meeting to discuss the proposed standard is planned for April 14, 2015 at 6 p.m. The meeting will be held at Prior Lake City Hall, 4646 Dakota Street Southeast in Prior Lake.

More information on water quality in Spring Lake and how to submit comments the proposed site-specific standard can be found on the Spring Lake-Upper Prior Lake webpage.

To receive more information or submit comments on this proposed site-specific standard for Spring Lake, contact Chris Zadak, MPCA, 520 Lafayette Rd. N., St. Paul, MN 55155; phone 651-757-2837 or 800-657-3864; or email at All comments must be received by May 5, 2015.