Updates and Progress in Restoring the St. Croix River

This Labor Day weekend, morning found me racking my bike in a transition area and gearing up for the start of the St. Croix Valley Triathlon.

As the sun rose over Lakefront Park in Hudson, WI, I followed other participants down to the beach and prepared to dive into the St. Croix River for a 1.5K swim. During the next half hour I spent swimming the double-loop course across the river and back, I had ample time to consider efforts underway to improve the lower 25 miles of the river, known also as Lake St. Croix.  

The St. Croix River is nearly 160 miles long and forms a significant portion of the border between Minnesota and Wisconsin. Protected by the National Wild and Scenic Rivers Act since 1968 (upper river) and 1972 (lower river), the St. Croix has none-the-less suffered from the effects of land-use and development within the 7,760 square miles that drain to the river.

Both Minnesota and Wisconsin have classified Lake St. Croix as officially impaired for excess phosphorus, which contributes to nuisance algal growth that sometimes make recreational activities like boating or swimming in a triathlon unpleasant or even dangerous.

On August 8, 2012, a multijurisdictional collaborative known as the St. Croix Basin Team achieved an important milestone in their efforts to restore the St. Croix River when the TMDL (Total Maximum Daily Load) Plan was approved by the U.S. Environmental Protection Agency. For those not familiar with the term, a TMDL Plan is a regulatory tool that identifies the sources of pollution to a body of water and reductions needed to reach an established water quality goal.

After years of studying the river, its tributaries, and land-uses within the greater watershed basin, the St. Croix Basin Team concluded that a reduction in annual phosphorus loading to the river equivalent to 123 metric tons per year would be needed to drop concentrations of total phosphorus in Lake St. Croix from 51μg/L to 40μg/L. Doing so will limit the frequency of nuisance algal conditions and switch the lake from a planktic state, in which algae are free-floating in the water, to a more desirable benthic state, in which algae are bottom-dwelling.

According to the Lake St. Croix TMDL Plan, most of the phosphorus polluting the St. Croix River is the result of “human alterations of the landscape, such as agriculture and urban development.”

It was fitting then that the second stage of my triathlon, a 40k bike ride through the rolling countryside of western Wisconsin, brought me away from the water and into the St. Croix’s watershed, where the vast majority of work needed to restore the river will take place.

The second stage in the race to save the St. Croix is the TMDL Implementation Plan, currently in draft format, which outlines strategies that will be used to reduce phosphorus from various sectors within the basin, including regulated sources like wastewater treatment plants and MS4s (communities that manage their own Municipal Separate Storm Sewer Systems), and unregulated sources like agriculture, forestry, and non-MS4 communities. Here is a snapshot of what is contained within the Implementation Plan:

• Reduce phosphorus, by 18 metric tons per year, from the 55 wastewater treatment plants that discharge to the St. Croix River and its tributaries, which will achieve 15% of the total TMDL goal. Already these plants have significantly improved the effectiveness of their facilities and many have permits that are actually more restrictive than the St. Croix TMDL plan.

• Reduce phosphorus, by 4 metric tons per year, from the 25 MS4 communities in the basin (3% of the TMDL goal). This will be accomplished by incorporating low impact development practices for new development and redevelopment, targeting best management practices such as raingardens in critical locations, and working with residents and businesses to reduce widespread, small sources of phosphorus such as leaves and grass clippings in the streets.  

• Reduce phosphorus, by 100 metric tons per year, from unregulated sources of pollution such as shoreline and riparian properties, agriculture, forestry, and urban and rural residential runoff. Importantly, this unregulated portion of the TMDL Implementation Plan comprises 80% of the phosphorus reduction goal, which means that civic engagement, education and outreach, and voluntary conservation efforts such as planting shoreline buffers, using cover crops during the winter, and careful planning of forest management activities will be critical.

In addition to outlining phosphorus reduction strategies, the Implementation Plan also assigns goals for each of the Minnesota and Wisconsin counties that drain to the St. Croix River. Washington County, which represents 3.6% of the land within the St. Croix Basin, has a goal of reducing phosphorus loading to the St. Croix by 15,728 lbs/year (6.8% of the total load reduction goal). Even Ramsey County shares a tiny portion of the load, with a reduction goal of 61 lbs/year from the portion of North St. Paul within the Valley Branch Watershed District.

Unlike my Labor Day weekend race, the effort to restore the St. Croix River is more like an ultra-decathlon than an Olympic triathlon. Once the TMDL Implementation Plan is approved, the hard work of implementing projects and practices to reduce phosphorus pollution across the 7,760 square mile basin will begin.

Water-quality monitoring, underway for more than 30 years, will continue to measure the overall health of the river and its tributaries, as well as the success of various phosphorus reduction strategies. Data from these monitoring efforts will help the St. Croix Basin Team to fine-tune their implementation strategies and revise the TMDL plans as needed.

At the finish line is cleaner water for Lake St. Croix and countless wetlands, ponds, lakes, streams and rivers within the St. Croix Basin, and better health for the people and other living things that call this basin home.

Find the Lake St. Croix TMDL Plan and other supporting documents on the MPCA website.