Notice of Availability of the Draft Spring Lake Site-Specific Standard and Request for Comment
Public Comment Period Begins: April 6, 2015
Public Comment Period Ends: May 5, 2015
Public Hearing: April 14 (PLSLWD Board Meeting, Prior Lake City Hall, 6pm)
The Minnesota Pollution Control Agency (MPCA) is requesting comments on a proposed site-specific water quality standard for Spring Lake (Lake ID 70-0054-00) in Scott County. Information pertaining to the site-specific standard is available for review at: http://www.pca.state.mn.us/index.php/view-document.html?gid=22531.
Written comments on the proposed site-specific standard must be sent to the MPCA contact person listed below by 4:30 P.M., on May 5, 2015.
Spring Lake is 642 acre lake located in the southern part of the Twin Cities Metropolitan Area in the City of Prior Lake and Spring Lake Township. The MPCA included this lake on the 303(d) impaired waters list for Minnesota in 2002 due to excess nutrient (phosphorus) concentrations. Elevated phosphorus levels lead to excess algae growth and thereby adversely impacts aquatic recreation. As the basis for restoring this waterbody the MPCA staff completed a Total Maximum Daily Load (TMDL) study for Spring Lake which was approved by U.S Environmental Protection Agency (EPA) in September of 2011. That TMDL was based on the existing water quality standard for phosphorus, 40 micrograms/liter (μg/L). The Prior Lake-Spring Lake Watershed District has since done a technical study that has established that a site-specific standard of 60 μg/L would be more appropriate for this lake. Should this site-specific standard be approved by EPA the TMDL will need to be revised. This revision will affect the allowable pollutant load allocations which will ultimately mean less stringent load reductions will be needed for Spring Lake.
Site-Specific Standard Background
Minnesota Rule Chapter 7050 provides water quality standards for waterbodies as well as the legal basis for consideration and adoption of site-specific water quality standards (https://www.revisor.leg.state.mn.us/rules/?id=7050.0222). Per this rule, lakes are assigned eutrophication standards for three parameters: total phosphorus, chlorophyll-a (the main pigment in algae) and Secchi disk depth (a measure of water clarity). The MPCA proposes changing the total phosphorus target for Spring Lake from 40 μg/L to 60 μg/L and the chlorophyll-a target from 14 μg/L to 20 μg/L. The current Secchi disk standard of 1.4 meters is not being proposed to change. The rationale for this proposal is that:
- Lake sediment cores were collected and analyzed to estimate historic in-lake concentrations of total phosphorus dating back more than two hundred years and thereby determine natural background levels. The methodology that was employed revealed that prior to European settlement of the area (believed to be from about 1850 to 1880) when land use began to change (i.e., farming began to take hold) total phosphorus was approximately 60 μg/L. It is reasonable to consider this a natural background condition and, therefore, the best phosphorus level that this lake could be expected to achieve.
- The lake sediment cores could not be used to provide historic chlorophyll-a levels. Instead to determine an appropriate target for that parameter the MPCA used a statistical approach to relate the response of chlorophyll-a to total phosphorus concentrations. A statewide lakes dataset was used for this analysis and revealed that 20 μg/L is an appropriate target for Spring Lake.
- For the Secchi disk target setting a method similar to chlorophyll-a was used. This analysis indicated that 1.4 meters, the current Secchi disk standard, remains an appropriate target for Spring Lake.
- Through this analysis MPCA staff concluded that the beneficial use of aquatic recreation will be protected if the proposed site-specific standard is adopted and attained.
For further detail and explanation regarding this proposal, see the supporting technical document entitled “Spring Lake Site-Specific Eutrophication Criteria Justification” at: http://www.pca.state.mn.us/mvri9d0 This document is also available at the MPCA office at the address listed below.
Preliminary Determination on the draft Site-Specific Standard: The MPCA Commissioner has made a preliminary determination to submit this site-specific standard to the EPA for final approval. Comments on the proposed site-specific eutrophication standard will be considered before the proposal is sent to the EPA for approval.
Written Comments: You may submit written comments on the proposed site-specific eutrophication standard for Spring Lake or on the Commissioner’s preliminary determination.
Written comments must include the following:
- A statement of your interest in the proposed site-specific standard;
- A statement of the action you wish the MPCA to take, including specific references to sections of the proposed site-specific standard that you believe should be changed; and
- The reasons supporting your position, stated with sufficient specificity as to allow the Commissioner to investigate the merits of your position.
Public Information Meeting: A public informational meeting is will be held by the MPCA in cooperation with the Prior Lake-Spring Lake Watershed District. This will be an informal meeting to solicit public comment and to help clarify and resolve issues. The meeting will be held on April 14, 2015, at 6:00 p.m. It will be held at:
Prior Lake City Hall
4646 Dakota Street Southeast
Prior Lake, Minnesota
Request for an MPCA Citizens’ Board Information Item request: A request for an MPCA Citizens’ Board Information Item must include the following:
- A statement identifying the matter of concern;
- A statement of the reasons the MPCA should hold a Citizens’ Board Information Item; and
- The issues that you would like the MPCA to address at the Citizens’ Board Information Item.
The need for an MPCA Citizens’ Board Information Item will be considered by the Commissioner. Should the Commissioner determine that an MPCA Citizens’ Board Information is not warranted, the requesting party will receive written notification of such.
Agency Contact Person: Written comments and requests for more information should be directed to:
Minnesota Pollution Control Agency
Watershed Division – Watershed Section
520 Lafayette Road North
St. Paul, MN 55155-4194
Phone: 651-757-2837 (direct)
Minnesota Toll Free: 1-800-657-3864
TTY users may call the MPCA teletypewriter at 651-282-5332 or 1-800-657-3864.