1 Options for Estimating BMP Performance (Load Reductions)
1
Options for Estimating BMP Performance
(Load Reductions)
Presentation Overview
Informed implementation
Quantifying load reduction associated with management strategies
BMP evaluation Sources of BMP effectiveness information Determining which BMPs are appropriate
Tools that can be used to support the process
Informed Implementation Determine load reduction necessary to meet objectives Identify opportunities for implementation Review design standards/ordinances that will dictate
techniques Identify and narrow down BMP options based on
objectives Identify scale for comparative analysis of
alternatives/scenarios Quantify BMP options
spreadsheet-based watershed/site-scale model
Evaluate scenarios and select management strategy
Be Sure Objectives Have Been Clearly Defined
Example Objectives: Meets NPDES Phase 1 & 2 stormwater
regulations Protect sensitive species Protect water quality by addressing 303(d)
listing concerns Address detention for the control of
stormwater volume and peaks
Quantifying Load Reduction to Meet Objectives
Sources of load quantification data Watershed modeling/load quantification results
(previously described), TMDL reports, etc. Source and spatial targets for implementation
Table 5-4. Nutrient and BOD baseline and allocation loads by contributing subwatershed for impaired waters of the Cedar Creek watershed (daily averages based on the 2001-2003 meteorological regime).
BOD TN TP Reach ID/Subwatershed Baseline
(lb/day) TMDL
(lb/day) Percent
Reduction Baseline (lb/day)
TMDL (lb/day)
Percent Reduction
Baseline (lb/day)
TMDL (lb/day)
Percent Reduction
1, Lower Cedar Creek 24.74 14.12 43% 31.49 17.51 44% 1.54 0.85 44%
2, Slaughter Creek 4.44 2.74 38% 4.74 2.74 42% 0.20 0.12 41%
3, Slaughter Creek 15.16 9.03 40% 23.76 13.31 44% 0.87 0.49 43%
4, Slaughter Creek 61.40 35.49 42% 97.83 54.47 44% 3.65 2.05 44%
5, Slaughter Creek 17.54 9.98 43% 30.81 17.09 45% 1.12 0.62 44%
6, Slaughter Creek 34.70 23.42 33% 34.38 20.68 40% 1.28 0.76 40%
7, Slaughter Creek 31.19 18.67 40% 47.92 26.91 44% 1.87 1.04 44%
8, Slaughter Creek 52.48 32.26 39% 77.65 43.68 44% 2.99 1.69 43%
Identify Opportunities for Implementation
Impervious analysis
Political constraints and priorities
Physical constraints
Environmental constraints
Review Design Standards/Ordinances, if applicable
Zoning ordinances Subdivision ordinances Sedimentation and erosion ordinances Stormwater/water quality management
ordinances
Examples Minimize the total volume of surface water runoff that flows from any specific site during and following development, in order to replicate pre-development hydrology to the maximum extent practicable
Achieve average annual 85% Total Suspended Solids (TSS) removal for the developed area of a site. Areas designated as open space that are not developed do not require stormwater treatment. All sites must employ Low Impact Development (LID) practices to control and treat runoff from the first inch of rainfall.
0
5
10
15
20
25
11:00 AM 12:00 PM 1:00 PM 2:00 PM
Time (hours)
Str
eam
Flo
w (
ff3 /s
) Developed site hydrograph
BMP influence on hydrograph
Identify BMP Options
Where can I Access Information on BMPs? National Menu of Stormwater Best Management Practices:
http://cfpub.epa.gov/npdes/stormwater/menuofbmps/index.cfm International Stormwater Best Management Practices (BMP)
Database: http://www.bmpdatabase.org/
Feedlots DPRA Inc.1986. An evaluation of the cost effectiveness of agricultural best
management practices and publicly owned treatment works in controlling phosphorus pollution in the Great Lakes basin. Prepared for U.S. Environmental Protection Agency, Washington, DC.
Edwards, W.M., L.B. Owens, and R.K. White. 1983. Managing runoff from a small, paved beef feedlot. Journal of Environmental Quality 12(2).
Edwards, W.M., L.B. Owens, R.K. White, and N.R. Fausey. 1986. Managing feedlot runoff with a settling basin plus tiled infiltration bed. Transactions of the ASAE 29(1):243-247.
Forest Seyedbagheri, K. A. 1996. Idaho forestry best management practices: Compilation
of research on their effectiveness. General Technical Report INT-GTR-339. USDA Forest Service, Intermountain Research Station, Ogden, Utah.
Cropland U.S. Environmental Protection Agency (EPA). 1993. Guidance specifying
management measures for sources of nonpoint pollution in coastal waters. EPA-840-B-92-002. Office of Water, Washington, DC.
Urban Athayde, D.N., P.E. Shelly, E.D. Driscoll, D. Gaboury, and G. Boyd. 1983. Results
of the nationwide urban runoff program - volume I - final report. U.S. Environmental Protection Agency, Washington, DC.
Leeds, R., L.C. Brown, M.R. Sulc, and L.VanLieshout. 1994. Vegetative filter strips: Application, installation and maintenance. AEX-467-94. Ohio State University Extension, Columbus, Ohio. http://ohioline.osu.edu/aex-fact/0467.html
MDEQ (Michigan Department of Environmental Quality). 1999. Pollutants controlled: Calculation and documentation for section 319 watersheds training manual. Michigan Department of Environmental Quality, Lansing, Michigan, USA.
Northeastern Illinois Planning Commission (NIPC). 1994. Model best management practice selection methodology & Lake County decision-making framework. NIPC, Chicago, Illinois.
Schueler, T.R. 1987. Controlling urban runoff: A practical manual for planning and designing urban BMPs. Document No. 87703. Metropolitan Washington Council of Governments, Washington, DC.
Davis, A.P., Shokouhian, M., Sharma, H. and C. Minami. 2001. Laboratory study of biological retention for urban stormwater management. Water Environment Research 73:5-14
Maryland Prince George's County and the U.S. Environmental Protection Agency. 1999. Low-Impact Development Design Strategies: An Integrated Design Approach. http://www.epa.gov/owow/nps/lid/lidnatl.pdf
Where can I Access Information on BMPs?
Identify Specific BMP Options
Narrow Down BMPs Based on Objectives
Quantify BMP Options at a Subwatershed or Watershed Scale
Goals Quantify selected BMP strategies (i.e., individual
BMPs or BMP pairings) Watershed scale Local scale
Compare potential load reductions to target Determine optimal strategy considering
environmental benefits and $$
Available Tools Spreadsheet tools Watershed/site-scale models
What Tool Should I Select? Has a model already been used for load
quantification? What scale is important? Is an annual load reduction estimate sufficient? Should individual storms be evaluated?
Spreadsheet tools Normally good for annual/overall reductions Usually at a watershed scale – sometimes at the site
scale Watershed models
Allow for continuous/long-term simulation Often can be used for storm evaluation Ability to function at all scales – site and watershed
Example Spreadsheet Tool for Evaluation of Agricultural BMPs
Field study of BMP performance determines 75% reduction of pollutant load for a 120 acre site
Watershed loading model determined annual loading rates for multiple sites
Spreadsheet can be used to determine BMP load reductions at all sites
Using Watershed Models to Evaluate BMP Performance
Some watershed models are capable of directly evaluating management strategies Agricultural practices: SWAT, AGNPS, GWLF Urban practices: P8-UCM, SWMM Mixed land use: HSPF
Techniques vary by model Assumed BMP removal efficiencies Simulation of storage and pollutant routing
Pollutant losses (e.g., decay, settling) Volume losses (e.g., infiltration, evaporation)
Example Watershed Model BMP Simulation - GWLF
Often used to estimate existing loads
Different BMPs represented using general model functions
Considerations: Universal Soil Loss
Equation parameters Curve #s Manure/fertilizer
application Septic loads User-specified
removal rates
Example Watershed Model BMP Simulation - SWMM
Often used to estimate existing loads
Different BMP scenarios modeled to determine load reductions
Considerations Street sweeping Flow detention and
pollutant removal Varying hydrologic
and pollutant loading assumptions
Summary of Management Practice Simulation Techniques in Selected Models
Additional Models for Detailed BMP Simulation
Detailed site-scale analysis
Specialize in particular types of BMPs
Example: Prince
George’s County (MD) BMP-DSS
Clinton River Watershed Site Evaluation Tool
BMP Optimization
What is optimum? Minimize cost Maximize pollutant flow and/or load reduction Combination of the above
How does one measure optimum? Minimum cost, long-term flows, and/or
pollutant load Best-fit multi-storm curve with pre-developed
condition
Find optimum BMP placement and selection strategies based on pre-selected potential sites and applicable BMP types
9%
11%
13%
15%
17%
19%
21%
23%
$0 $200,000 $400,000 $600,000 $800,000 $1,000,000 $1,200,000
Cost ($)
Ru
no
ff V
olu
me
Red
uct
ion
(%
fro
m E
xist
ing
Co
nd
itio
n)
Trad
e-O
ff C
urve
Optimal Solution
Initial Run
Identify Optimal SolutionExample of BMP-DSS Multiple Run Output
Clinton River Watershed Site Evaluation Tool
Evaluate potential benefits of BMPs at the site development scale
Inputs Site characteristics BMP
characteristics Outputs
Peak discharge Annual runoff Pollutant Loads
Nitrogen Rate
Target
0.00
2.00
4.00
6.00
8.00
10.00
12.00
14.00
16.00
18.00
1-yr 24-hr storm
0123
4567
11:00 AM 12:00 P M 1:00 P M
cfs
P ost, no BM P s
Existing
P ost, with BM P s
Why Site Evaluation Tool?
Evaluate flow and water quality impact of proposed residential and commercial development
Identify most cost-effective suite of BMPs Support decision-making activities
Tool used in combination with other data/information to make final management decisions at the site scale
Promote consistency Help with Phase 2 reporting requirements
Who Will Use the Site Evaluation Tool?
Local planning review agencies Help with the evaluation of proposed
projects
Potentially could ask developers to use the tool, too
Example Example
Areal Loading RatesExistingLanduse
Designwithout BMPs
Designwith BMPs Target
Meets Goal?
Total Nitrogen (lb/ac/yr) 0.66 9.56 7.17 6.00 NO!Total Phosphorus (lb/ac/yr) 0.11 1.53 0.92 1.33 YesSediment (ton/ac/yr) 0.011 0.120 0.018
Site is located in Urban Residential Nutrient ZoneTN loading rate is higher than the buy-down range of 3.6 to 6 lb/ac/yr
Nitrogen Rate
Target
0.00
2.00
4.00
6.00
8.00
10.00
12.00
Phosphorus Rate
Target
0.00
0.50
1.00
1.50
2.00
Sediment Rate
0.000
0.020
0.040
0.060
0.080
0.100
0.120
0.140
Areal Loading RatesExistingLanduse
Designwithout BMPs
Designwith BMPs Target
Meets Goal?
Total Nitrogen (lb/ac/yr) 0.66 9.56 3.26 6.00 YesTotal Phosphorus (lb/ac/yr) 0.11 1.53 0.30 1.33 YesSediment (ton/ac/yr) 0.011 0.120 0.001
Site is located in Urban Residential Nutrient ZoneTN loading rate is below the buy-down range of 3.6 to 6 lb/ac/yr
Nitrogen Rate
Target
0.00
2.00
4.00
6.00
8.00
10.00
12.00
Phosphorus Rate
Target
0.00
0.50
1.00
1.50
2.00
Sediment Rate
0.000
0.020
0.040
0.060
0.080
0.100
0.120
0.140
Conclusions Quantifying potential impacts from BMPs is
critical to watershed planning Provides a guide toward achieving load reduction goal Informs selection of a management strategy
Spreadsheet and modeling tools are available Spreadsheet tools
Most useful for watershed-scale analysis Operate on a large time step
Watershed/site-scale models Useful for local scale, as well as watershed-scale Can operate on a short time-step (including individual
storms) Provide a key first step for engineering design
Again, one size doesn’t fit all!