Minnesota's Impaired Waters and TMDLs

TMDL Project: Lake Pepin — Excess Nutrients

Lake Pepin is a natural lake on the Mississippi River and is part of the Zumbro River watershed and the Mississippi River - Lake Pepin watershed in the Lower Mississippi River Basin. It is located near Lake City, Minnesota. It has a surface area of about 40 square miles and an average depth of 18 feet. 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, drains into the Lake Pepin watershed.

The lake is on the 2004 Impaired Waters List. A Total Maximum Daily Load (TMDL) defines the maximum amount of a pollutant that a waterbody can carry without violating water quality standards.

Lake Pepin TMDL project

Lake Pepin is impaired by excess nutrients and is also affected by the turbidity impairment in the south metro Mississippi River. These pollutants are distinct but inter-related, and will be addressed in separate TMDL reports. The Lake Pepin Watershed TMDL project is unique in its size and scope due to the amount of land area included in the watershed as well as the fact that it overlaps state boundaries.

At the recommendation of the project’s Science Advisory Panel, the MPCA has suspended the draft project report until the agency develops nutrient standards for rivers. In March 2011, the MPCA published the Lake Pepin Site Specific Eutrophication Criteria (wq-s6-10) .

Based on research, the MPCA plans to propose the following site specific standard for Lake Pepin:

• 100 micrograms per liter for total phosphorus; and
• 28 micrograms per liter for chlorophyll-a.

The MPCA believes these criteria will provide protection of aquatic recreational uses for Lake Pepin and the downstream pools, and should be applicable over the range of flows for which the criteria were developed.

For comparison purposes, the mean level of total phosphorus in Lake Pepin from 2000-2009 was 171 micrograms per liter and the mean of chlorophyll-a for the same time period was 30 micrograms per liter.

Achieving this standard for Lake Pepin will mean reducing phosphorus and chlorophyll in specific upstream watersheds, such as the Lower Minnesota River, Crow River and Sauk River. To quote the Executive Summary of the criteria document, “The proposed Lake Pepin criteria should not be used in isolation to imply that phosphorus reductions anywhere upstream of the lake will have the desired impact. The main biological activity affecting Lake Pepin trophic status is not taking place in the lake, but upstream of it.”

In particular, reductions upstream of the Minneapolis-St. Paul wastewater treatment plants will be needed to achieve the desired standards.

The Lake Pepin criteria are not stand-alone goals to be pursued in isolation. Rather, they are part of the goals for the Mississippi River system, which, if pursued systematically in unison, will achieve the desired results.

The MPCA anticipates the Lake Pepin site specific standard will be ready for public comment in 2012-13.

In a related effort, the MPCA is also proposing nutrient standards for Mississippi River Pools 1-8. See the criteria, Mississippi River Pools 1 through 8: Developing River, Pool, and Lake Pepin Eutrophication Criteria, on the Water Quality Standards page.

More specific information about Lake Pepin impairments and this project is available in the following factsheet:

• Lake Pepin Watershed TMDL Project Overview

Project schedule and work products

• Project Schedule
• Lake Pepin TMDL Work Plan #2, July 2006 
• Upper Mississippi River — Lake Pepin Water Quality Model: Development, Calibration, and Application
  • Table of Contents
  • Executive Summary
  • Introduction
  • Model Development
  • Upper Mississippi River Data Summary
  • UMR-LP Model Hydrodynamics and Sediment Transport Calibration/Confirmation
  • UMR-LP Model Water Quality Calibration/Confirmation
  • UMR-LP Model Application
  • Recommendations for TMDL Year 4
  • References
  • Summary of Water Quality Data Collected in Support of Lake Pepin Modeling Activities

Stakeholder advisory meetings: Selected presentations

August 20, 2009 - Stakeholder Advisory Committee Meeting, St. Paul

• Water Quality Standards and Site Specific Standards: Mark Tomasek, MPCA
• Meeting Site-Specific Standards for the Mississippi River and Lake Pepin: Dennis Wasley, MPCA

Events

• 3rd Annual Lake Pepin Forum - Impacts of a Cleaner Mississippi: What matters to residents of the Lake Pepin watershed
  • Thursday, June 4, 2009, Red Wing, MN
  • Presentations from the 2009 Forum (please note that you may need to adjust your printer settings to minimize ink use if printing these files):
    • Opening Remarks: Trevor Russell, Friends of the Mississippi River
    • What’s New with the Lake Pepin TMDL: Norman Senjem, MPCA
    • Explaining a Watershed Approach: Gaylen Reetz, MPCA
    • A Locally Anchored System for River Restoration: Laura Jester, Dakota County
    • Clear Water, Aquatic Vegetation and Fish: Tim Schlagenhaft, Minnesota DNR
    • Introducing the Lake Pepin Legacy Alliance: Mike McKay, Watershed Resident
    • Wastewater and Stormwater: Marco Graziani and Mike Trojan, MPCA
    • Using 21st Century Technology to Target Critical Areas: John Nieber, University of Minnesota
    • 21st Century Cropping Solutions for Critical Areas: Linda Meschke, Rural Advantage
    • Engaging Agriculture in Environmental Problem-Solving: Warren Formo, MAWRC
    • Providing Reasonable Assurance of Nonpoint Source Implementation: Kris Sigford, MCEA

Related links

• South Metro Mississippi - Turbidity: TMDL Project
• EPA Office of Water: Total Maximum Daily Load (TMDL) Program
• USGS Home Page
• Upper Mississippi Basin Stakeholder Network
• Basin Alliance for the Lower Mississippi in Minnesota
• Minnesota River TMDL
• Mississippi Makeover

Contact information

For information about the Lake Pepin TMDL Project, contact:

• Catherine Rofshus, 507-206-2608
• Bob Finley, 507-344-5247, robert.finley@state.mn.us