Lake Pepin Legacy Alliance About Us

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What is the Clean Water Act (CWA)?
What does the CWA require of states?
What is TMDL?
How are TMDLs calculated?
What is the role of the public in the TMDL process?
Why is Lake Pepin on the 2004 impaired waters list?
When and how did Lake Pepin become impaired?
What is the current status of Lake Pepin?

What is the Clean Water Act?

The Clean Water Act (CWA) is the cornerstone of surface water quality protection in the United States. The statute employs a variety of regulatory and non-regulatory tools to sharply reduce direct pollutant discharges into waterways, finance municipal wastewater treatment facilities, and manage polluted runoff. These tools are employed to achieve the broader goal of restoring and maintaining the chemical, physical, and biological integrity of the nation's waters so that they can support "the protection and propagation of fish, shellfish, and wildlife and recreation in and on the water."

What does the CWA require of the States?

      ~establish Water Quality Standards (WQS) for its waters
     ~monitor the conditions of its waters
     ~list water bodies [303 (d) list] that do not meet WQSs
      ~set priority rankings for the waterbodies listed.
     ~establish TMDLs that meet WQS for each listed waterbody
     ~solicit public comment
      ~submit 303(d) list and TMDLs to Environmental Protection Agency (EPA) for approval
      ~incorporate TMDLs into the State's Continuing Planning Process

What is TMDL?

A TMDL (Total Maximum Daily Load) establishes the maximum amount of an impairing substance or stressor that a waterbody can assimilate and still meet WQSs and allocates that load among pollution contributors. TMDLs are a tool for implementing State WQSs. They are based on the relationship between pollution sources and in-stream water quality conditions. A TMDL addresses a single pollutant or stressor for each waterbody.

How are TMDLs calculated?

A TMDL is the sum of the allowed pollutant loads for point sources, non-point sources, projected growth and a margin of safety.
      TMDL = Point Sources + Nonpoint Sources + Projected Growth + Margin of Safety
Point sources are discharges from a specific, identifiable source. Nonpoint sources are nutrients and pollution sources not discharged form a single point: e.g., runoff from agricultural fields or feedlots. Load allocations are determined through the review of monitoring data and watershed modeling. The tools used depends upon the complexity of the problem.

What role does the public play in the TMDL Process?

Once work on a specific TMDL begins, local governments, identified interested parties, and appropriate dischargers in that watershed will be consulted during key stages of development. Introductory TMDL briefings may be provided upon request. A second round of more in-depth briefings will be provided to those who request more detail. The public is invited to become involved in the listing process. After a draft TMDL has been developed, a formal public notice and comment period will be provided prior to the TMDL's submission to EPA. When a TMDL is approved, stakeholders will participate in determining how the TMDL should be implemented to reach allowable loading levels.

Why is Lake Pepin placed on the 2004 Impaired Waters List?

Lake Pepin has been placed on the 2004 Impaired Waters List for two types of water quality problems. As a lake, it is impaired by excess nutrients (euthropication) that cause algae blooms, particularly severe during lower-flow periods. Eutrophication is the aging process by which lakes are fertilized with nutrients. Natural eutrophication will very gradually change the character of a lake. Cultural eutrophication is the accelerated aging of a lake as a result of human activities. As part of the Mississippi River reach extending from the St. Croix River to the Chippewa River, Lake Pepin is also turbidity impaired. Turbidity measures particles in the water, such as sediment and algae, related to the depth sunlight can penetrate into the water. Higher turbidities reduce the penetration of sunlight in the water and can affect species of aquatic life that survive in the waterbody.
A Total Maximum Daily Load (TMDL) defines the maximum amount of a pollutant that a waterbody can carry without violating water quality standards.

When and how did Lake Pepin become impaired?

This didn't happen overnight! One hundred and fifty years ago, the Upper Mississippi River was made up of naturally occuring channels, sandbars and wooded islands. In the spring, the river flowed rapidly, creating new channels and sandbars. In summer, it was so shallow in places that a person could walk across it. The river was too dangerous for commercial boat traffic so in 1866, the 4-foot channel project was begun - the first of several channel improvements projects by the Army Corp of Engineers that eventually resulted in the building of the locks and dams in the 1930s to maintain a 9-foot shipping channel. The system transformed the free flowing river into a series of navigation pools, maintaining high and relatively stable water levels in the lower portion of the pools, which ensured the passage of tows and barges even in the middle of summer. For several decades, these pools supported a wealth of fish, wildlife and aquatic habitats.

However, the high water levels made the islands in the lower portion of the pools more vulnerable to erosion from waves and many of them disappeared . Materials carried by the river and soil washed from the nearby eroding islands gradually filled in channels and deep holes. Aquatic plants that grew in the shallow water bordering the islands were affected by these changes and many formerly lush plant beds either decreased in size or disappeared completely . These plants are part of the foundation for the web of life in the river providing food and shelter for fish and wildlife. With the relatively stable water levels created by the navigation pools, plant beds that were eliminated over time had little change to become reestablished.

What is the current status of Lake Pepin?

Lake Pepin is at the downstream endpoint of the most polluted reach of the Mississippi River in the state. It is no accident that this reach begins at the confluence with the Minnesota River. The Minnesota supplies most of the sediment that makes the Mississippi constantly muddied, and threatens to fill upper Lake Pepin with mud before the present century is past. Suspended solids from the Minnesota River make the Mississippi incapable of supporting the rich rooted vegetation that once made the river and Lake Pepin a haven for ducks and swans.

Nuisance algae blooms during hot, dry summers are another threat to water quality in Lake Pepin. Metropolitan wastewater treatment facilities have drastically reduced their phosphorus discharges, the result of a successful campaign to protect Lake Pepin following disastrous algae blooms in 1988. However, demographers expect an additional million people to settle in the Twin Cities over the next couple of decades, a trend which threatens to reverse recent progress in wastewater quality. Moreover, continuing high phosphorus loads from the Minnesota River pose an ongoing threat to Lake Pepin. Phosphorus concentrations are so high in the Mississippi, at 150 to 200 parts per billion, that a warm, calm dry spell in any summer could quickly trigger unsightly algae bloom.

The Minnesota Pollution Control Agency will soon complete a Total Maximum Daily Load (TMDL) study that will prescribe reduced loads of sediment and phosphorus from upstream sources, particularly the Minnesota River and Metropolitan Area wastewater treatment facilities. While the MPCA has regulatory authority over wastewater discharge, agriculture, the source of much phosphorus and sediment in the Minnesota River, is largely unregulated.

Who are we?

The Lake Pepin Legacy Alliance is a multi-state non-profit organization established in 2009 by an ad hoc committee determined to preserve and restore Lake Pepin as an integral part of the Upper Mississippi River System.

What is our mission?

We are dedicated to slowing and reversing the current trend of sediment and nutrient flow to Lake Pepin. We bring a professional approach for public involvement in present and future watershed restoration activities that elevate the importance of implementation of the recommendations and "best practices" that science and reason dictate. Leading with the tools of education and information we will protect the natural heritage of Lake Pepin.

Why does Lake Pepin need our protection?

Lake Pepin is a natural lake on the Mississippi River. It is located near Lake City, Minnesota. It has a surface area of about 40 square miles and an average depth of 18 feet. Its watershed is about 48,634 square miles (approximately half of Minnesota’s total land area plus a small portion of Wisconsin), including the Upper Mississippi, St. Croix and Minnesota Rivers.

Lake Pepin is at the downstream endpoint of the most polluted reach of the Mississippi River in the state. It is no accident that this reach begins at the confluence with the Minnesota River. The Minnesota supplies most of the sediment that makes the Mississippi constantly muddied, and threatens to fill upper Lake Pepin with mud before the present century is past. Suspended solids from the Minnesota River make the Mississippi incapable of supporting the rich rooted vegetation that once made the river and Lake Pepin a haven for ducks and swans