The primary reasons for a permittee to perform monitoring of receiving waters are to (a) evaluate the impact of TMDL implementation strategies enacted throughout the watershed, and (b) evaluate impairment status to determine if the impaired waterbody can be removed (i.e., delisted) from the 303(d) Impaired Waters List. The following subsections outline the basics of developing a monitoring program to meet goals established within the Guidance Manual for Assessing Quality of Minnesota Surface Waters for Determination of Impairment: 305(b) Report and 303(d) List (MPCA, 2018a), and developing a monitoring protocol standard operating procedure (SOP). Specifically, the Establishing a Monitoring Program section provides guidance on when, where, and what to sample, while the Establishing a Monitoring Protocol section provides guidance on how to sample (i.e., sampling SOP).
Before developing or implementing a lake monitoring program, the applicable TMDL(s) should be reviewed to determine (a) if an ongoing water quality monitoring program exists or will be implemented and (b) what organization(s) are responsible for water quality monitoring (e.g., individual permitteess, the applicable Watershed District or Watershed Management Organization (WMO), etc.). Review of ongoing and planned water quality monitoring programs can help a permittee optimize sampling procedures to supplement ongoing monitoring efforts and help identify potential partnering opportunities with other organizations (e.g., WDs, WMOs, Citizen-Assisted Monitoring Program (CAMP), Soil and Water Conservation Districts (SWCDs), Metropolitan Council, etc.). To encourage statewide water quality monitoring efforts, the MPCA offers Surface Water Assessment Grants (SWAG) to eligible partners, including MS4s. More information on SWAG requirements and grant application can be found on the MPCA’s Surface Water Assessment Grants webpage.
In addition to review of planned or ongoing monitoring programs, the applicable TMDL(s) should be reviewed to determine the specific water quality standard(s) that apply to the impaired waterbody. Water quality standards applicable to the impaired waterbody are specific to the pollutant (e.g., chloride), the water body type (e.g., lake), and the water use classification (e.g., Class 2A).
The following subsections outline specific lake monitoring program requirements related to each of the four (4) pollutants discussed on this page: total suspended solids (TSS), total phosphorus (TP), bacteria, and chloride.
Lake eutrophication water quality standards established in the Minnesota Rule, Chapter 7050 (MINN. R. 7050, 2018) require paired observations of TP, chlorophyll-a, and Secchi disk transparency during the summer period (June 1 through September 30) of the monitoring year. From Part 7050.0222, Subp. 2a:
Eutrophication standards for lakes and reservoirs are compared to summer-average data. Exceedance of the total phosphorus and either the chlorophyll-a or Secchi disk transparency standard is required to indicate a polluted condition.
The numeric standards for TP, chlorophyll-a, and Secchi disk transparency vary by use classification (e.g., Class 2B), ecoregion (e.g., North Central Hardwood Forests), and by lake classification (e.g., trout lake, shallow lake, etc.). The applicable water quality standards for the impaired waterbody are outlined in the applicable TMDL report. Based on Minnesota lake eutrophication standards and specific impairment assessment and delisting requirements for lake eutrophication, the following list outlines specific recommendations to develop a lake eutrophication monitoring program. Specific monitoring protocol recommendations are discussed here.
Lake Eutrophication Monitoring Program Recommendations
As of the 2018 Minnesota Impaired Waters List (MPCA, 2018b) there are no lakes listed as impaired for Escherichia coli (E. coli). For more information regarding establishing an E. coli monitoring program for streams, link here.
Chloride water quality standards within Minnesota Rule, Chapter 7050 (MINN. R. 7050, 2018) are consistent for all Minnesota waters (i.e., all use classifications). Specifically, Minnesota Rules define a chronic toxicity-based chloride water quality standard of 230 mg/L (i.e., chronic standard), and an acute toxicity standard of 860 mg/L (i.e., maximum standard). Specific data requirements for evaluation of impairment condition for both the chronic and maximum chloride water quality standard established in the Guidance Manual for Assessing the Quality of Minnesota Surface Waters for Determination of Impairment: 305(b) Report and 303(d) List (MPAC, 2014) are outlined below.
The MPCA has published several Statewide Chloride Resources, including the Draft Statewide Chloride Management Plan (MPCA, 2019) and specific protocols related to stream and lake chloride monitoring.
Based on review of chloride standards, statewide guidance documents, and specific impairment assessment and delisting requirements for chloride impairment, the following list outlines specific recommendations for developing a lake chloride monitoring program. Specific monitoring protocol recommendations are discussed here.
Chloride Monitoring Program Recommendations