1 / 26

Elm Creek Watershed TMDL E. coli TMDL – Review of Preliminary Findings

This presentation outlines the review of E. coli standards, monitoring data assessment, load duration curve development, and source identification assumptions in the Elm Creek Watershed. It covers the main issues related to human ingestion of bacteria, applicable standards, steps in developing load duration curves, and allocations among different pollutant sources. The presentation also details the assessment of livestock, septic systems, wildlife, and urban stormwater as potential sources of bacteria concentrations.

sabo
Download Presentation

Elm Creek Watershed TMDL E. coli TMDL – Review of Preliminary Findings

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Elm Creek Watershed TMDLE. coli TMDL – Review of Preliminary Findings Elm Creek Watershed Management Commission Technical Advisory Committee Meeting June 12. 2013

  2. Outline of Presentation • Review of E. coli Standards • Overview of monitoring data • Review preliminary load duration curves, allocations for 3 of 4 listed reaches (excluding Elm Creek mainstem) • Review/feedback on key assumptions in source identification

  3. Bacteria Impairments • Main issue is human ingestion of bacteria typically found in digestive tract of warm-blooded animals, causing sickness and even death • Most streams and rivers in MN designated by law to support full or partial body contact recreation.

  4. E. Coli Bacteria Standard • Standard applies between April 1 and October 1 • Reach impaired if one or more monthly geomean values exceed 126 organisms/100 ml OR • More than 10% of all samples during a month can exceed 1260 organisms /100 ml

  5. Overview of Bacteria Data by Impaired Reach

  6. Steps in Developing Load Duration Curve (LDC) • Develop flow duration curve (FDC) for 10-year period of record at bottom of impaired reach • Multiply flows in FDC by standard of 126 cfu/100 ml to get load duration curve • Use median value in each of 5 flow regimes to develop allowable load (“loading capacity” or LC) • Subtract 5% of LC as explicit Margin of Safety (MOS)

  7. Developing Allocations • Allocate remaining load (after MOS) among: • Permitted wastewater dischargers • Construction and Industrial stormwater • Municipal Separate Storm Sewer Systems (MS4s) • Non-permitted sources (i.e. all areas not draining through a permitted MS4 stormwater conveyance system)

  8. Developing Allocations (con’t) • Allocations made proportionate to area in contributing watershed • No waste load allocation = not permitted to discharge • MnDOT and Hennepin County road ROW • Assigned as part of WLA if within 2010 urbanized area • Assigned as part of LA if outside 2010 urbanized area

  9. Load Duration Curve (LDC) for Diamond Creek E. coli

  10. Proposed boundary conditions for Diamond Creek E. coli allocations

  11. Diamond Creek Allocation Table (E. coli)

  12. Percent Reductions Needed To Reach Standard-Diamond Creek • Note: Table corrected after 6-12-13 TAC meeting

  13. Load Duration Curve (LDC) for Rush Creek Mainstem E. coli

  14. Rush Creek Mainstem Allocation Table (E. coli)

  15. Percent Reductions Needed To Reach Standard-Rush Cr. Mainstem • Note: Table corrected after 6-12-13 TAC meeting

  16. Load Duration Curve (LDC) for Rush Creek-South Fk. E. coli

  17. Rush Creek-South Fk. Allocation Table (E. coli)

  18. Percent Reductions Needed To Reach Standard-Rush Cr. –South Fk. • Note: Table corrected after 6-12-13 TAC meeting

  19. Source Assessment • Purpose – To identify potential sources of elevated bacteria concentrations • Detailed monitoring data provides basis for identifying priority areas of watershed • Components • Exceedances by season and flow regime • Source Inventory

  20. Exceedances by Flow Regime (Diamond Creek)

  21. Source Inventory • Basic approach developed for Southeast MN bacteria TMDL (MPCA 2002) • Purpose: To compare number of bacteria generated by major known sources in the project area • Known sources include: • Livestock (manure application, feedlots, pastures) • Septic Systems • Wildlife • Urban Stormwater Runoff

  22. Livestock Data

  23. Key assumptions (Source Inventory) (con’t) • Livestock – • GIS analysis to determine number/type of livestock in pastures/feedlots within 300’ of streams • Assume 25% available from pastures/feedlots within 300’, 5% if more than 300’ • Manure spreading • Define livestock confinement period (4 months/year?) • Assume manure produced is spread on cropland, no incorporation • Same availability assumptions as for pasture/feedlots

  24. Key assumptions (Source Inventory) (con’t) • Septic Systems – Use population estimates based for un-sewered areas based on 2010 census, assume 50% available • Assume 0% available from populations served by sanitary sewer/WWTP

  25. Key assumptions (Source Inventory) (con’t) • Wildlife – Assume 30 deer/sq. mile, 20 geese/sq. mi. based on TRPD and MDNR wildlife manager estimates, 100% delivery • Urban Stormwater – Assume 0.58 dogs per household, 0.73 cats per household in urban areas, 10% delivery

  26. Final Product (Source Inventory) • Tables and/or charts for each subwatershed showing “bacteria for delivery”

More Related