A plan for cleaning up the Minnesota River

As reported in our December 2004 issue, the Minnesota Pollution Control Agency (MPCA) conducted a study in 2004 to measure phosphorus pollution and set reduction goals on the lower Minnesota River — the last 22 miles, from Shakopee to the confluence with the Mississippi.

Now, in a bold new plan, it’s proposing specific ways to counter this pollution.

Over the last 20 or 30 years, the Minnesota has cleaned up its act considerably. (See sidebar article featuring the MPCA’s Mike Tibbetts.) While last year's study focused on phosphorus, other water quality problems remain. “Some problems are spread around the state,” says the MPCA’s Larry Gunderson, study co-author. “Some things we should be concerned with include bacteria from farms and wildlife, as well as individual homes or communities without proper sewage treatment that are straight-piping their waste through a tile line. In the mid-‘90s there were about 40 such incorporated communities, while now there are only 13. Still, it may be awhile before all these communities have effective treatment facilities.”

Last year’s MPCA study, authored by Gunderson and Jim Klang, gives a broad overview of the pollution problem in the river. One of the chief symptoms of the problem is low dissolved oxygen (DO) during occasional late-summer low flow periods. Occurring on average every 10 years, these low flows represent a diminution of oxygen so severe that fish and other higher life forms may be threatened.

That’s because upstream pollutants such as phosphorus produce algae blooms, and as bacteria in the water decompose the algae they leave less oxygen available to other and higher forms of aquatic life.

The MPCA’s new plan proposes to limit the decrease the phosphorus in the river from wastewater discharges, improperly treated sewage, and urban stormwater runoff. The plan also suggests Best Management Practices (BMPs) for agriculture, which will keep more water on the land and allow less run-off.

To measure pollutants and devise corrective clean-up action, the plan uses a process called Total Maximum Daily Load (TMDL), which was first spelled out in the federal Clean Water Act of 1973. In the words of the MPCA report,

A TMDL Report establishes the allowable loading of pollutants for a water body based on the relationship between pollutant sources and water quality conditions. The development of a TMDL Report provides states a basis for determining the pollutant reductions necessary to restore and maintain the quality of their water resources. The MPCA requires an implementation plan within one year following EPA approval of a TMDL Report.

Since the EPA approved the 2004 report last fall, the MPCA is obligated to publish its implementation plan this fall. After meeting with concerned parties this last year, the MPCA has published online a draft of this year’s new implementation plan. (The executive summary, at the start, gives a good overview.) The draft plan suggests specific measures on how to reduce phosphorus and other undesirable materials and so to decrease pollution and increase oxygen in the lower Minnesota. As a start, it identifies four sources of pollution:

1. Agriculture
2. Stormwater
3. Raw sewage
4. Wastewater treatment plant effluent

And it suggests specific remedial actions for all sources, especially wastewater plants because during low-flow periods wastewater treatment plants are the largest source of phosphorus.

The 40 biggest industrial and municipal wastewater treatment plants outside the metro area are required to reduce phosphorus drastically, as the following chart shows:

Blue Lake and Seneca, the two wastewater treatment facilities on the Lower Minnesota River, have upgraded treatment processes to diminish contributions to the dissolved oxygen problem.

Stormwater discharge must be cleaner too. Communities and other “permitted entities” like industry and construction will need to submit plans to the MPCA that spell out how they will reduce pollution. Communities without permits will be required to conduct education and other voluntary means to cut down on pollution.

The raw sewage problem will be addressed by several measures, says the plan:

• County and city staffs will locate direct discharges of sewage and fix them.
• Unsewered communities and homeowners can seek loans and construct new treatment systems through the MPCA's Clean Water Partnership (CWP) program and other sources.

• wetland restoration
• conservation tillage
• buffer strips

All these BMPs will help hold water back “during high or medium flow periods so that it filters into the soil and becomes part of the groundwater. Then, during periods of low flow, the water will seep back into the river and have the effect of shortening the low-flow period.”

MPCA stakeholders such as treatment plants, communities, and farmers will be working with the agency to implement the plan, making regular reports and perhaps meeting annually to review progress. The stakeholders will help the agency monitor the Minnesota River and track phosphorus reduction goals.