Total Maximum Daily Load & Impaired Waters List

Transcription

1 Nine Mile Creek Watershed Chloride Total Maximum Daily Load Kevin Bigalke Nine Mile Creek Watershed District 2010 Road Salt Symposium

2 Total Maximum Daily Load & Impaired Waters List Nine Mile Creek Watershed Stakeholder Process Technical Advisory Committee Cities, Hennepin Co., MnDOT, Private Citizen Advisory Committee Development of the Chloride TMDL Report during 2009 TMDL Report Submitted to MPCA in December, 2009

3 Nine Mile Creek Chloride TMDL Recap Monitoring Data Comparison to WQ standard Proposed Allocations Performance-based measures Reduction percentages for sources

4 Data collection NMCWD (since 2004) Water quality monitoring at three WOMPtype stations on Nine Mile Creek: North Fork at Metro Blvd., Edina South Fork at West 77 th St., Bloomington Main Stem at 98 th St., Bloomington Met. Council WOMP station at 106 th Street (Harrison Park) Continuous flow and Harrison Park, Bloomington site during 2008

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6 Chloride Impairment 230 mg/l chronic standard (four-day average), no more than one sample exceedance within 3-year period 860 mg/l maximum standard

7 Impact of Chlorides Chlorides remain in the system Does not settle out in stormwater treatment systems Decreased dissolved oxygen levels Interfere with plant growth Reduces diversity of organisms Impairs reproduction Affects invertebrates

8 Chloride -- continuous conductivity relationships

9 Chloride -- continuous conductivity

10 Chloride -- continuous conductivity

11 Chloride -- continuous conductivity

12 Chloride -- continuous conductivity

13 Approach for wasteload allocations uniform reduction percentage Road Salt Application Rates Total MS4 Road Miles (tons/yr) (tons/mile/yr) Bloomington Eden Prairie Edina Hopkins Minnetonka Richfield Hennepin County* * MnDOT Composite Rate 10.8

14 TMDL Loading Capacity A TMDL Study must complete this pollution load allocation formula for critical conditions: LA(s) + WLA(s) + Margin of Safety + Reserve Capacity = Total Maximum Daily Load Where: LA = Load allocations from nonpoint sources WLA = Waste load allocations from point (permitted) sources Margin of Safety = to account for potential scientific error Reserve capacity = set aside for future development

15 Approach for wasteload allocations performance based measures Designed to meet 61% reduction Application rates for municipal and highway operations are based on: Road Manual application guidelines 31 deicing events w/ typical pavement and weather conditions Our compiled lane mileage Balance TMDL equation difference assigned to private/commercial sector paved areas w/ implicit margin of safety

16 Lane miles by MS4 in NMCWD MS4 Lane Miles Percentage Bloomington % Eden Prairie 86 7% Edina % Hopkins 55 5% Minnetonka 78 7% Richfield 11 1% Hennepin County 110 9% MNDOT %

17 Proposed allocations

18 Approach for wasteload allocations uniform reduction percentage Road Salt Application Rates Total MS4 Road Miles (tons/yr) (tons/mile/yr) Bloomington Eden Prairie Edina Hopkins Minnetonka Richfield Hennepin County* * MnDOT Composite Rate 10.8

19 Next steps--chloride Chloride TMDL Report has been submitted to MPCA Finalizing TMDL Report to submit to EPA Implementation Planning Development of performance-based measures Use Technical Advisory Committee to help Phased Approach Sub-watershed Pilot Study, Anti-icing, cost-share equipment retrofits, education, training MS4s starting to make changes

20 Questions??

21 What does this mean? Reduce to 250 lbs./lane mile Cities need to reduce to 4.2 tons/mile/year MNDOT & Hennepin County need to reduce to 5.05 tons/mile/year