redwood river tmdl critique
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Redwood River TMDL Critique
David De Paz, Alana Bartolai, Lydia Karlheim
IntroductionRedwood River
• The Redwood River is impaired for both aquatic life and aquatic recreation due to fecal coliform and turbidity.
• Our critique is on the TMDL for bacteria.
• 8 reaches of the Redwood River fail to meet the water quality standard for bacteria (E. coli).
[MPCA]
Watershed CharacteristicsRedwood River
Area: 705 sq. mileTributary to the Minnesota River
The impaired reaches are classified as:
2B
2C
3B7
2B
2C
Recreation of all kind/aquatic life
Aquatic life support and recreation
stringent
Less stringent
General industrial purposes
Limited resource value
Note: Class 7 streams had not been assessed in this draftreport but will be in 2010.
Land UseRedwood River
• Land Use– 85.5% Agriculture– 2.5% urban/Residential
• Artificial drainage
BacteriaRedwood River
Causes in the watershed: • failing septic systems -there are 1,948 subsurface
sewage treatment systems. 1,051 are deemed “failing”, 334 are deemed “threats to public health”
• wastewater treatment plant bypasses and flushes (there are 8 WWTP)
• unsewered communities • livestock waste from feedlots• land applied manure (98% of total)• Domestic pets and wildlife
Standard only valid
April -October
Class 2B/2C(organisms/
100mLs)
Class 7(organisms/
100mLs)
E. coli 126 630
Fecal coliform 200 1000
[wolfenotes.com]
Sampling SitesRedwood River
[USEPA, 2011]
‘99
‘03-’06
‘99
‘99
’99-’06‘99
’99-’06
’99-’06
‘74-’06
Sites sampled by the MPCA and the Redwood-Cottonwood Rivers Control Area (RCRCA)
Fecal Coliform Redwood River
[MPCA]
Time Period: 1997-2006
(geometric mean by reach)
TMDLs were calculated for each of the 8 reaches at each flow condition (helpful for BMP implementation).
TMDL= ∑ (WLAs + ∑ LAs + MOS + RC)
TMDL DevelopmentRedwood River
point sources
nonpoint sources
accounts for uncertainty
future development
Waste load Allocations (WLAs)- • NPDES permits= 0 (Livestock facilities that have been issued NPDES permits are assigned
a zero WLA)• WWTF: assumed to be discharging the maximum of 200 orgs/100 mLs => overestimated• MS4(storm sewer systems): => MS4 + LA• The rest is assumed to be LA
Load Allocation (LA)- non-point sources not subject to NPDES permit (except land applied manure)
TMDL Allocation WLA & LARedwood River
Likely non-point sources
Land-applied manure
inadequate human WW treatment
Non-permitted municipal stormwater systems
Pets/wildlife
Reserve Capacity (RC)- • Total RC== 0 because the watershed shows trends of decreasing population and stagnant
animal numbers. Note: The MPCA will reopen the TMDLs covered in this report if adjustments are required
Margin of Safety (MOS)- • calculated per flow zone since allocations = (flow)
x conversion factors => load
• Implicit MOS: used when dry and low flow zone calculations used a concentration-based limit. In these conditions, flow is primarily GW fed and very little E. coli is conveyed.
TMDL Allocation MOS & RC Redwood River
TMDL AllocationsWest line to Threemile Creek
[MPCA]
Land use :• 82.3 %cultivated• 10.9 % urban• 4.2 % grass• 2.0 % forest• 0.5% water/wetlands• 1 WWTF with MS4 permit covering
2.86 % of the entire watershed • No feedlots with NPDES permits • 5472 animal units without permits• 140 SSTS units with 56 are failing.
TMDL AllocationsWest line to Threemile Creek
[MPCA]
TMDL Required ReductionWest line to Threemile Creek
[MPCA]
58.42%
69.65%
60.32% 60.55%
0%Inadequate
dataInadequate
data
Load Duration CurveWest line to Threemile
[MPCA]
Implementation and BMPsRedwood River
[MPCA]
BMPs:CRP buffers
alternative tile intakes
grassed waterways
livestock exclusion
sediment basins
nutrient management plans
wetland restorations
streambank stabilization
Goal:Achieve water quality standards for fecal coliform bacteria within 10 years by educating, training, and providing monetary incentives.
Note: Specific implementation plan will be made after TMDL gets approved
Critiques & Assumptions:Fecal Coliform/ E.coli
Unknowns of Fecal Coliform:
• Survival rates
• Fecal coliform may be higher when stream bed is aggravated (i.e. scouring events, runoff) [Davis et al. ,2005]
[http://www.shardcore.org]
Critiques & Assumptions:Fecal Coliform
Fecal Coliform vs. E.Coli• Standard is normalized based on comparison studies by MPCA showing that 63% of fecal
coliform will be E.Coli.
• E. coli samples converted using 179 E. coli = 200 cfu meaning that 89.5% of fecal coliform will be E. Coli.
• Substantiated using 35 sample pairs from the same Watersheds between 1985-2006
[MPCA]
Standard only valid
April -October
Class 2B/2C(organisms/
100mLs)
Class 7(organisms/
100mLs)
E. coli 126 630
Fecal coliform 200 1000
Critiques & Assumptions:Flow
• Several reaches don’t have sufficient flow monitoring data• USGS gage stations were used to find missing flow data
• Duration of monitoring data varies between stations
[USEPA, 2011]
‘99
‘03-’06
‘99
‘99
’99-’06‘99
’99-’06
’99-’06
‘74-’06
Critiques & AssumptionsImplementation
BMPs:
CRP buffers
alternative tile intakes
Grassed waterways
livestock exclusion
sediment basins
nutrient management plans
wetland restorations
streambank stabilization
Livestock manure has environmental and economic benefits:• Less prone to erosion• Reduces commercial fertilizer
Wetland restorations• affects farmers
Streambank stabilization• Can be expensive
Livestock exclusions• Requires fencing and more management
Strength Required ReductionWest line to Threemile Creek- site with largest reduction
[MPCA]
58.42%
69.65%
60.32% 60.55%
0%Inadequate
dataInadequate
data
Strengths• TMDL broken up by flow and reach
• 4 of the 8 reaches analyzed were not yet on the 303d list, but were included for thoroughness
• Entire portion of report focuses on understanding E. coli sources
• Willingness to reevaluate plan if/when changes occur ( i.e. population growth)
[MPCA]
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