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Published byArron Gyles Hardy Modified over 9 years ago
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Critique of North Branch of Sunrise River TMDL Nate Topie and Taylor Hoffman
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Background East Central MN, tributary of Sunrise River and part of larger St. Croix River Basin Most of river basin has high or very high aquifer sensitivity to pollution Land use TypePercentage Agriculture58.1 Forest8.3 Open Water5.3 Forested Wetland17.7 Non-Forested Wetland8.0 Barren0.1
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Background Ctd. Listed as impaired water under 303d of Clean Water Act due to Fecal Coliform Impaired for swimming & other primary contact recreation Fecal Coliform: bacteria present in intestines of warm- blooded animals Indicator for contamination by feces Indicator for presence of waterborne pathogens, viruses, protozoa
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Water Quality Standards Standard Part 1: Monthly geometric mean should not exceed 200 organisms/100 mL Must have 5 samples per month Standard Part 2: No more than 10% of samples taken during a month can exceed 2000 organisms/100 mL Standards only apply between April and October Focused on geometric mean because less subject to random variation
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Sunrise Water Quality Data Data was collected from August-September in 1997, May- July in 1998, April-October in 2002-2003 Didn’t include 1997 data or previous data Little data for 2002-2003 seasons Sampled at sites SUN-15 and SUN-5 Continuous flow data taken at SUN-5 and flow at other sites assumed to be proportional Data for 2002-2003 were grouped together if from the same month
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Sunrise Water Quality Data
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Used month of June to calculate desired reduction because the month had the highest number of geometric mean exceedances 52% reduction=((geometric mean-standard)/geometric mean) Seen as protective guideline But three out of five sample sites had less than 5 samples, what was required by standard Not mentioned how many ‘wet’ or how many ‘dry’ samples were taken 2002 had a wet summer; 2003 had a wet spring Two seasons of data aren’t very representative of system; no dry or very wet years present
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Source Assessment
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TMDL and Allocations Followed process developed by “Revised Regional TMDL Evaluation of Fecal Coliform Bacterial Impairments in Lower Mississippi River Basin in Minnesota” WLA North Branch Wastewater Treatment Plant MS4 Determined from TMDL-WLA WWTP -MOS, which was divided between non- point and MS4 based on land percentages Leaking septic systems; illegal straight pipes assumed to be zero LA Non-point: livestock, septic systems, wildlife, pets outside of MS4 Remaining 68% after WLA WWTP, MOS, and WLA MS4 were subtracted from TMDL
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Margin of Safety and Reserve Capacity MOS given by difference between the central and lowest value for each zone Used this method because the allocations are direct functions of daily flows MOS will account for flow variability Reserve Capacity assumed equal to zero As growth increases, assumed that fecal coliform will decrease Sewer systems with disinfection will take the place of livestock populations
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TMDL and Sources
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Public Participation Included organizations/persons such as: Minnesota DNR, MPCA, Chisago SWCD, North Branch City Council, Wild River State Park, U of M Extension, volunteer stream monitors, landowners, and interested citizens. Included a steering committee, public information meetings, and publications in local press
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Monitoring Plan Test specifically for E. coli instead of broadly fecal coliform Monitor at same sites Samples taken 5 times per month April through October At least two seasons
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Implementation Focus on reducing top 3 sources (top 80%): unregulated livestock facilities, pasture near streams, and dangerous septic systems Numerous financial incentives for landowners Time frame: 5-10 years
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Goals of Implementation Reduce fecal coliform load from unregulated livestock facilities. Store waste, vegetative buffer strips, move fences, clean lot Reduce load from pastures near streams Move livestock, rotational grazing Reduce load from septic systems Bring into compliance, switch to city sewer Surface applied manure, pets, wildlife
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Summary Calculation of the components of the TMDL were valid (WLA, LA, MOS, Reserve Capacity) 52% reduction seems reasonable Top three goals in implementation make sense Valid to focus on those sources for implementation since they were derived from more reliable calculations Would be easier to pinpoint and decrease (vs. wildlife fecal contamination) The sources of those goals produced high amounts of fecal coliform during wet and dry periods
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Summary Could use more data Not enough grab samples in between two seasons Below requirement of 5 samples per month Would make the geometric mean and therefore reduction goal more accurate if more samples were taken Only two years used for data collection Though they compared to 1998, could be helpful to include more years of data Also, mentioned in beginning of report that there was close to 20 years of data; where is it/can it be used? TMDL calculation was roughly approximated for some sources; however this couldn’t really have been improved
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