Legislative Report: Detailed Assessment of Phosphorus Sources to Minnesota Watersheds

2007 Update

• Detailed Assessment of Phosphorus Sources to Minnesota Watersheds - Atmospheric Deposition: 2007 Update (file size = 4.7 MB)
  The purpose of this memorandum is to provide an updated discussion about Atmospheric Deposition as a source of phosphorus to Minnesota watersheds. This discussion builds upon an analysis conducted in 2003 for the Minnesota Pollution Control Agency (MPCA) and is based on a review of the available literature, consideration of monitoring data and other available support data, and includes the results of phosphorus loading computations for each of Minnesota’s ten major watershed basins.

Background

In 2003, concerns about the phosphorus content of automatic dishwashing detergents prompted the passage of legislation requiring a comprehensive study of all of the sources and amounts of phosphorus entering publicly-owned treatment works and, ultimately, Minnesota surface waters. The assessment, funded by the Legislative Commission on Minnesota Resources and conducted for the MPCA by a consulting firm, is the first scientific study of just how much phosphorus enters Minnesota's lakes, wetlands, rivers and streams, and where it comes from in each of the state's 10 major watersheds.

The study found that statewide, automatic dishwashing detergents contribute about three percent of the total phosphorus load to state waters. Under normal water flow conditions, roughly two-thirds of the total load comes from nonpoint sources, with runoff from cropland and pasture supplying most of the load and lesser amounts coming from streambank erosion, urban runoff and atmospheric deposition. Approximately 31 percent of the phosphorus load comes from point sources such as wastewater treatment facilities and industrial treatment facilities.

The complete report is contained in the files below. Due to the size of the report - more than 800 pages - it has been broken up into smaller sections. Questions, comments and requests for additional information can be directed to Dennis Wasley at the MPCA, 651-757-2809, toll-free at 1-800-657-3864, or by e-mail at dennis.wasley@state.mn.us.

Legislative Report: Detailed Assessment of Phosphorus Sources to Minnesota Watersheds

• Cover Letter to Legislature
• Cover Page, Acknowledgements and Table of Contents (file size=1.4 MB)
• Executive Summary (file size=4.9 MB)
• Section 1: Introduction (file size=1.1 MB)
• Section 2: Methods (file size=584 KB)
• Section 3: Results and Discussion (this section is broken into sections due to large file sizes)
  • Section 3.1: Basin Hydrology (file size=5.1 MB)
  • Section 3.2: Estimated Basin Total Phosphorus Amounts Contributed to POTWs and Surface Waters (by Source) (file size=781 KB)
  • Section 3.3: Summary of Phosphorus Loadings by Basin (file size=2.2 MB)
  • Section 3.4: Phosphorus Sources and Estimated Amounts Contributed to Surface Waters (by Basin, Total and Bioavailable) (file size=3.0 MB)
  • Section 3.5: Comparison of Total Phosphorus Loadings from All Sources with Monitored Loadings in Minnesota and Upper Mississippi River Basins (file size=56 KB)
  • Section 3.6: Effluent Total Phosphorus Reduction Efforts by Wastewater Treatment Plants (file size=102 KB)
• Section 4: Recommendations (file size=176 KB)
• Section 5: Overall Conclusions (file size=60 KB)
• References (file size=238 KB)
• Appendices Cover Page (file size=1.3 MB)
• Appendix A: Basin Hydrology Technical Memorandum (file size=6.1 MB)
• Appendix B: Point Sources Technical Memorandum (file size=2.2 MB)
  • Appendix to Appendix B (file size=327 KB)
• Appendix C: Cropland and Pasture Runoff Technical Paper (file size=376 KB)
  • Appendix C Figures 1-14 (file size = 6.3 MB)
  • Appendix C Figures 15-25 (file size = 6.8 MB)
• Appendix D: Feedlot Runoff Technical Memorandum (file size=574 KB)
• Appendix E: Atmospheric Deposition Technical Memorandum (file size=1.7 MB)
• Appendix F: Deicing Agents Technical Memorandum (file size=1.2 MB)
• Appendix G: Streambank Erosion Technical Memorandum (file size=860 KB)
• Appendix H: Individual Sewage Treatment Systems (ISTS)/Unsewered Communities Technical Memorandum (file size=575 KB)
• Appendix I: Non-Agricultural Rural Runoff Technical Memorandum (file size=4.3 MB)
• Appendix J: Urban Runoff Technical Memorandum (file size=1.2 MB)
• Appendix K: Bioavailable Phosphorus Technical Memorandum (file size=480 KB)
• Appendix L: Effluent Total Phosphorus Reduction Efforts by WWTPs Technical Memorandum (file size=198 KB)
  Note: Some of the PDF files listed above are large and may take a few minutes to open in your browser. The larger files may not open on some computers with low memory. If you are unable to open a file, contact Mary Osborn at mary.osborn@state.mn.us or if you prefer at 651-757-2069 or 1-800-657-3864 to receive the report on a CD. Printed copies of the Executive Summary are also available upon request. Technical inquiries on the study can be directed to Dennis Wasley at the MPCA, 651-757-2809, toll-free at 1-800-657-3864, or by e-mail at dennis.wasley@state.mn.us.