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© 2014 HDR, Inc., all rights reserved.
TMDL Purgatory: Stuck Between Compliance and Futility
City of Winston-Salem Stormwater/Erosion Control Division
APWA Stormwater Conference September 15, 2014
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01 Salem Creek TMDL Background
02 Case Study on Structural BMPs
03 Hurdles to Implementation
04 Final Thoughts
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01
Salem Creek TMDL Background
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303d listed stream for biological impaired TMDL approved in September 2006 by EPA 11.7 stream miles of Salem Creek Watershed land use Dry and wet weather exceedences of 400 cfu/100 mL instantaneous standard
The ‘Purity’ of Salem Creek
Forested, 30%
Residential (1/3 to 1/4 acre), 13%
Industrial, 11%
Open Space, 10%
Commercial , 7%
Salem Creek Watershed Land Use, Year 2011
Source: City of Winston-Salem Watershed Masterplan
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MS4 Waste Load Allocation
WLA NPDES WLA MS4 LA MOS TOTAL
Existing Load (cfu/day) 4.54x1011 4.22x1012 1.07x1012 NA 5.74x1012
Load Allocation (cfu/day)
4.54x1011
2.95x1011 7.37x1010 9.14x1010 9.14x1011
Percent Reduction 0% 93.0% 93.1% NA 84.1%
Load Reduction (cfu/day) - 3.93x1012 9.96x1011 - 4.83x1012
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Wildlife – most prevalent isolate source within watershed
Pets – 1 pet (dog or cat) per every 2 people in US
Sources: ASPCA and U.S. Census Bureau, 2012
Human – a dominant source during baseflow conditions
Source: NCDWQ, 2006
Livestock – greater contributor during high flow conditions
Source: NCDWQ, 2006
Fecal Coliform Sources
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Numerical ‘Sins’ of the Past
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Locate and prioritize fecal coliform pollutant ‘hot spots’
Expand current pollutant reduction strategies
Explore innovative methods of nonstructural BMP measures to actual WLA reduction
Document and track pollutant reductions
Hierarchy of appropriate BMPs for implementation
‘TIP’ to Salvation
Site-specific,
structural BMPs
Additional or expanded BMPs (nonstructural or
structural)
Broad, appropriate nonstructural BMPs
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02
Case Study on Structural BMPs
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Short Term o Fecal coliform impairment o Prioritize water quality capital projects and opportunities o Evolve existing water quality modeling (XP-SWMM) and
field efforts (BMP retrofit reconnaissance) Long Term o Impairments for other emerging urban pollutants o Address source controls or non-structural BMPs o Tool for tracking existing controls and load reductions
Water Quality Modeling Needs
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• Populated with GIS and spatial data • Based on EPA SWMM and other
accepted water quality simulations • More intuitive BMP parameterization • Integrated cost-efficiency optimization tool
Why we selected EPA SUSTAIN model?
Source: EPA SUSTAIN Training Documentation, Tetra Tech 2009
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Explicit, Relative Approach o Structural BMP opportunities screened to
analysis subset • 45 opportunities > 11 feasible site
o Goal to identify most cost effective structural BMPs
o Optimize size per site by 75-125%
A Twist on SUSTAIN
SUSTAIN Model
Optimized BMP Configuration
Data
BMP Placement, Types, Number, and Configurations
BMP/LID Optimization
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Specifics of our Approach o Detention or infiltration BMP o Designed per State BMP guidance o Simulated average annual hydrologic
conditions o Modeled 12 constituents o Set cost indices for
• Excavated volume • Filter media
How we used SUSTAIN
Source: EPA SUSTAIN Training Documentation, Tetra Tech 2009
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Load Reduction Cost Effectiveness o Structural BMPs as engineer specified o Structural BMPs optimized by SUSTAIN
Anticipated Results
Source: Introductory Webcast on SUSTAIN, EPA 2010
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Salem Creek Results
2.4
2.5
2.6
2.7
2.8
$7,000,000 $7,500,000 $8,000,000 $8,500,000 $9,000,000 $9,500,000
Perc
ent R
educ
tion
(%)
BMP Construction Cost
Total Cost($) 273_FC_AAL_1 BIORETENTION WETPOND 136_Length 275_Length 127_Length
8400087.01 97.3 2162560.505 6237526.5 214 208 424
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Prioritized Water Quality Capital Improvements
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Watershed/Site Characteristics
o 135 acres o 34.5% impervious o 1.1 x 1013 cfu/year o < 1 acre wetland footprint
Benefits
o Repurposing of lightly used park o Flood control o Water quality improvement
Evolution of an Opportunity
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Structural BMPs may have a limited role as a cost-effective solution o 11 structural BMPs produced 1.9% reduction at a cost of $7-8 million
Model simulations validate early processes and engineering judgment o Screening process was effective at identifying appropriate scale and location for BMPs
Wet ponds (detention) were more cost effective than bioretention (infiltration) o Despite higher efficiency for bioretention, wet ponds
were aided by lower start-up costs and ability to handle more volume
Conclusions from the Winston-Salem Case Study
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03
Hurdles to Implementation
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More emphasis to be placed source control and behavioral changes
Structural BMPs - Most Measurable, But Likely Cost-Prohibitive For Implementation
ID
Proposed BMP Performance
Approximate Size (acres)
Removal Efficiency (%)
Load Removed (cfu/day) Cost ($)
BR-03 0.7 79.7 3.3E+09 $317,036
BR-05 3.2 72.4 4.1E+10 $1,732,271
97.2 97.2 97.3 97.3 97.4 97.4 97.5 97.5 97.6 97.6 97.7
$6,500,000 $7,000,000 $7,500,000 $8,000,000 $8,500,000 $9,000,000 $9,500,000
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o Aspects of Frameworks • Create credits for multi-objective benefits • Individual (innovating) measures versus universally accepted practices • Confidence rating (ease level and detail of monitoring)
» Applicability » Data scope and depth » Data quality » Study factors
• Review Committees and Expert Panels (Chesapeake Bay Urban Nutrient Management Expert Panel)
• Technology and Information Exchanges (Environmental Information Exchange Network, International Stormwater BMP Database)
How To Determine Effectiveness Of Measures
Source: Chesapeake Bay Urban Nutrient Management Expert Panel
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Require shift to integrated planning with stormwater and wastewater entities
Success For Bacteria & Nutrient TMDL Implementation
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Develop monitoring strategy to answer questions more so than hope for trends
Random Monitoring Produces Random Results And Is Not Cost Effective
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Frequency Occurrence from Antibiotic Resistance Analysis
Strategic Planning – Holistic Methodology for Appropriate BMPs
Source Percentage (%)
Wildlife 35
Pets 32
Human 18
Livestock 15
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04
Final Thoughts
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Thank you!
Contact information o Andy Allen, City of Winston-Salem, [email protected] o Patrick Blandford, HDR, [email protected]
Questions