Opti-Tool for Stormwater and Nutrient ManagementMark Voorhees, US Environmental Protection Agency, Region 1 ([email protected])
What is Opti-Tool?Opti-Tool (Stormwater Management Optimization Tool) is a spreadsheet-based optimization tool that provides both a planning level and implementation level analysis. The tool helps planners determine the best mix of BMPs to provide the greatest benefit for achieving water resources goals while balancing costs.
The Planning Level Analysis provides maximum possible load reduction for all feasible BMP opportunities or cost-effective single solution that meets the numeric load reduction target. The Implementation Level Analysis provides optimal combination of different BMP types, sizes and spatial locations or cost-effective solutions for a range of load reduction targets.
Benefits of Opti-Tool Accessible to all users with Microsoft Excel 2013 software;
Represents actual regional precipitation conditions;
Incorporates best available information on stormwater urban
runoff nutrient quality;
Incorporates best available information for estimating long-term
cumulative nutrient load and runoff volume reduction
performances for 11 categories of structural stormwater controls;
Incorporates representative stormwater control units cost
information with scaling function to account for specific site
conditions and development density;
Includes flexibility to conduct either watershed planning level or
detailed site specific design-level analyses; and
Performs optimization analyses to determine most cost-effective
selection of structural stormwater controls for achieving
pollutant loading and runoff flow related reduction targets.
Regional Specific DataMultiple datasets required as input for Opti-tool were customized for EPA Region 1.
1.Regionally calibrated BMP performance curves were developed based on University of New Hampshire Stormwater Center (UNHSC) BMP monitoring data. The BMP data was utilized to calibrate BMPs.
2.Charlies River Watershed Association and the UNHSC provided BMP cost estimates.
3.Compared weather stations from major urban areas across the New England states to determine Boston Logan Airport station is a representative precipitation data set for Region.
4.Long-term pollutant runoff time series for typical land uses in the region were updated. Storm water monitoring data was used to calibrate the buildup and washoff processes on impervious cover.
Landuse TypeImpervious/
PerviousAgriculture ImperviousForest ImperviousHighway ImperviousIndustrial ImperviousCommercial ImperviousHigh Density Residential ImperviousMedium Density Residential ImperviousLow Density Residential ImperviousOpen Land ImperviousAgriculture PerviousForest PerviousDeveloped A PerviousDeveloped B PerviousDeveloped C PerviousDeveloped C/D PerviousDeveloped D Pervious
Planning Level AnalysisThe required information is separated into four different sections: management objective, optimization target, watershed information, and BMP information.
The Run Single Scenario analysis can estimate the BMP Storage Capacity for any given runoff treatment depth from the BMP impervious drainage areas. The RunOptimize button will begin the performance optimization process. The optimization analyses are performed through Excel Solver.
The different scenario approaches calculates the BMP storage capacity (ft3), BMP cost ($), treated impervious area (ac), annual operation and maintenance hours (hr), and pollutant load reduction (lbs) for the BMP defined with drainage area, from the BMP information step.
Implementation Level AnalysisThe Implementation Level Analysis allows users to enter watershed and BMP design information through a series of customized forms and tables. The steps are tabled in order on the Implementation Level analysis interface.
Target Reduction (%)
Solution Total
Cost (Million $)
Solution Reduction
(%)
52.1% 84.53 52.10%
BMP ID BMP Type BMP Area (ft^2)BMP Storage Depth
(ft)
Treated Impervious Area
(ac)Annual Maintenance (hours) Cost ($)
BMP1 INFILTRATIONBASIN 690000 2.0005 653.85 NOT ASSESSED 17,226,706
BMP2 INFILTRATIONBASIN 580000 2.0005 586.58 NOT ASSESSED 14,480,419
BMP3 INFILTRATIONBASIN 76000 2.0005 62.92 NOT ASSESSED 1,897,434
BMP4 BIORETENTION 432 1.768 0.22 4.55 23,616
BMP5 BIORETENTION 52360 1.768 33.12 685.58 2,862,341
BMP6 BIORETENTION 600000 1.768 495.3 10252.71 32,799,936
BMP7 BIORETENTION 60000 1.768 96.02 1987.61 3,279,994
BMP8 ENHANCEDBIORETENTION 100800 2.28 89.08 NOT ASSESSED 7,175,105
BMP9 SUBSURFACEGRAVELWETLAND 85200 3.2 107.58 2334.49 4,787,558
The user is responsible for defining the number of subbasins, junctions, land uses, BMPs, and pollutants under Watershed Information step. Then, throughout the step by step process, the user defines characteristics of each component.
The View Results option allows users to provide a target value, and Opti-Tool searches for the nearest solution and provides the solution reduction percentage and the total cost. It also provides the BMP information for the BMPs defined in the project. The BMP information includes: BMP Type, BMP Area (ft2), BMP Storage Depth (ft), Treated Impervious Area (ac), Annual Maintenance (hours), and BMP Cost($).
The Cost-Effectiveness curve references the output files and provides the user an opportunity to have a meaningful interaction with the simulation results. Implementation level analysis yields a graph of all solutions and identification of the “best” solutions in a cost vs. % reduction graph.
Cost saving of $47.5 million (56%) by lowering 10% of the numeric target (42.1%).
S T O R M W A T E R is a leading cause of poor water quality. Rain or melted snow runs down driveways, sidewalks and streets carrying oil, dirt and other pollutants into nearby waterways. Polluted runoff, which can cause erosion and flooding, runs into waterways and degrades plants, f ish, shellf ish and other wildlife. In water used for recreation, the runoff can lead to illness, and people who eat contaminated fish can also become sick. Untreated stormwater can also contaminate drinking
water sources.
U . S . E P A | S T O R M W A T E R O U T R E A C H I N M A S S A C H U S E T T S
t printed on 100% recycled paper, with a minimum of 50% post-consumer waste, using vegetable-based inks
March 2016
cont inued >
This summer, EPA Region 1 will complete work on Opti-Tool. Opti-Tool is a spreadsheet-based stormwater best management practices optimization tool. Opti-Tool is designed for use by municipal SW managers and their consultants to assist in developing technically sound and optimized cost-effective SW management plans.
Controlling and treating discharges of SW runoff, especially from highly developed urban areas, can be technically difficult and costly. Opti-Tool is designed to help SW managers navigate and overcome the planning and assessment challenges associated with retrofitting SW controls into existing developed landscapes. These SW controls are for the dual purposes of reducing pollutant loads of nutrients (TP, TN), sediments (TSS), and zinc (a surrogate for metals most commonly found in SW runoff), as well as addressing hydrologic imbalances.
Benefits of the tool• Accessible to all users with Microsoft Excel 2013 software.
• Represents actual regional precipitation conditions (long-term hourly data, 1992-2014).
• Incorporates best available information on SW runoff nutrient quality, including build-up/wash off processes, especially important in New England where storms are predominantly small events (e.g., 50% < 0.3 in.; 70% < 0.6 in.; 80% < 0.8 in.; and 90% < 1.2 in.).
• Incorporates best available information for estimating long-term cumulative nutrient load and runoff volume reduction performances for 11 categories of structural SW controls - UNHSC is one of the best sources of data.
• Uses information which is being shared with other regional tool developers to promote the use of consistent and high quality data.
• Incorporates representative SW control units cost information with scaling function to account for site specific conditions and development density.
• Includes flexibility to conduct either watershed planning level or detailed site specific design-level analyses.
• Performs optimization analyses to determine most cost-effective selection of structural SW controls for achieving pollutant loading and runoff flow related reduction targets.
Stormwater Managementwith Opti-Tool
• Provides results consistent with phosphorus source load rates and SW control reduction values in EPA Region 1’s new small MS4 general permits.
What a User needs to doThe user defines the targeted geographic area, land use distribution by impervious and pervious cover, pollutants of concern (or runoff volume), and follows user-friendly screen prompts for choices on characterizing watershed study area, soil, BMP types and hydraulic network/conduit information.
Results After a given scenario simulation has run successfully, results are provided depending on the user’s selection of a cost-effectiveness curve or a flow duration curve. Planning level scenarios yield “optimal solution” tables of different BMP types/sizes/O&M
costs/and corresponding load reduction. Implementation level analysis yields a graph of all solutions and identification of the “best” solutions in a cost vs. % reduction graph.
Coming Soon: A separate but compatible BMP Tracking and Accounting Tool (BATT) is being designed for use by small MS4 permittees for accounting, tracking and reporting on nutrient load reductions associated with BMP SW controls implemented and to demonstrate compliance with nutrient reduction requirements in EPA Region 1’s new stormwater permits for Massachusetts and New Hampshire.
Microsoft Mention of commercial products, services or organizationsdoes not constitute an endorsement by the U.S. EPA
TetraTech, Inc. Developed by TetraTech, Inc. for the U.S. EPA under contract.
Historical OverviewCharles River P TMDLs,
(Lower 2002–2007
Upper/Middle 2006-2011)
Residual
Designation
Petition,~2007
Sustainable
Funding Study
&
EPA Updated
Optimization
Analysis, 2010-11
Draft
Residual
Designation
Permit, ~2010
SW Control
Performance
Analyses
2007-10
Accounting System
Phosphorus Source
Loads & Credible
SW Control
Reduction Credits
~2010-16
Low Cost SW
Control
Performance
Analyses
~2013
MS4 Permits
with TMDL
Related
Reductions
Requirements
MA Final (2016)
NH Draft
(2013,15)
BMP Performance Curve: Gravel Wetland
Land Use: Commercial
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2
Depth of Runoff Treated (inches)
Po
llu
tan
t R
em
oval
TSS TP Zn
Stormwater
Management
Optimization
Analysis, 2010-11
Permitting Tools: Stormwater Management Optimization Tool “Opti-Tool”
(2013-16), and BMP Accounting and Tracking Tool “BATT” (2015-2016)
SW Management in Developed Landscapes: Technical & Economic Feasibility Challenges/Opportunities
CONCEPTS
• Comprehensive watershed planning vs. project by project
• Credible best estimates: • IC source loadings
• SW Control cumulative reductions (all sizes)
• Costs
• Accounting System for planning & compliance
• Every little bit counts
• Optimization analyses
Stormwater Phosphorus & Nitrogen
Phosphorus Highly associated with
very fine particles ~ 40 microns
Fine particles readily washed from impervious surfaces with smallamounts of rainfall
Stormwater controls must have filtration component to be effective
Nitrogen N Oxides are readily
washed off in early portion of rain events
Organic nitrogen can be a significant part of N load
High removals of SW nitrogen may require de-nitrification
Mass loading for DRO, Zn, NO3, TSS as a function of normalized storm volume for two storms: (a) a large 2.3 in rainfall over 1685 minutes; (b) a smaller 0.6 in storm depth over 490 minute. DRO=diesel range organics, Zn= zinc, NO3= nitrate, TSS= total suspended solids
(Source: Dr. James Houle, UNHSC)
4
90% of DIN mass
in first 0.2 in
runoff or 20% of
WQV
VISR/WQV =0.2
100% of DIN mass
in first 0.1 in
runoff or 10% of
WQV
VISR/WQV =0.1
New England Region- Cumulative Precipitation, Runoff Volume, Total Nitrogen Load Delivery from Impervious Cover
5
0%
16.2%
29.1%
55.7%
74.6%
95.0%
0%
28.4%
45.1%
75.9%
97.3% 98.0%
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
0.0 0.5 1.0 1.5 2.0 2.5
Cu
mu
lati
ve P
erc
en
t (%
)
Runoff Depth from Impervious Cover (IC), inchesRunoff volumes calculated by assuming initial abstraction of 0.1 inch of rainfall depth per event
Estimated Cumulative Percent (%) Runoff Volume and Total Nitrogen Load Delivery from Impervious Cover (IC)
Based on Hourly Precipitation Data - Boston, MA (1992-2014) and Median TN EMC data for Commercial/Industrial from NSQD - Rainfall Regions 1 & 2 (Pi
cumulative % average annual runoff from IC
cumulative % average annual TN Load from IC
Importance of Impervious Area (IA) in SW Pollutant Loading
• Impervious cover (IC) generates much greater runoff volume than pervious areas, therefore in developed landscapes IC is typically the most significant contributor of overall SW pollutant loading and retrofits should focus on IC
Calculated annual phosphorus load export rates (PLER) based on various hydrologic conditions for a range of stormwater total phosphorus (TP) concentrations
Watershed surface
DescriptionAnnual Runoff
Yield, MG/ha/yr
Annual Phosphorus Load Export (PLE), kg/ha/yr
Flow weighted SW TP conc., mg/L ----->
0.10 0.20 0.30 0.40 0.50 1.00
Impervious surface impervious surface 2.59 0.98 1.96 2.94 3.92 4.90 9.79
Pervious area HSG A well drained soils 0.07 0.03 0.05 0.08 0.10 0.13 0.25
Pervious area HSG Bmoderately drained
soils0.21 0.08 0.16 0.24 0.32 0.40 0.79
Pervious area HSG C limited permeability 0.41 0.15 0.31 0.46 0.62 0.77 1.54
Pervious area HSG D poorly drained soils 0.69 0.26 0.52 0.78 1.04 1.30 2.60
Annual Runoff yield by SWMM for hourly rainfall - Boston MA (1998-2002), Flow-weighted SW TP conc. = total annual P load divided by total annual runoff volume.
HSG= Hydrologic Soil Group, MG= million gallons, ha = hectare (1 ha= 2.47 acres)
Typical range of urban
SW TP concentrations
EPA Region 1’s Proposed Phosphorus Load Export Rates for use in Stormwater Permitting Process
Table 1: Average Annual Phosphorus Load Export Rates for use in the MA MS4 Permit
Phosphorus Source Category by Land Use
Land Surface CoverPhosphorus Load
Export Rate, Kg/ha/yr
Comments
Commercial (Com) and Industrial (Ind)
Directly connected impervious 2.0 Derived using a combination of the Lower Charles USGS Loads study and NSWQ
dataset. This PLER is approximately 75% of the HDR PLER and reflects the difference in the distributions of SW TP EMCs between Commercial/Industrial and Residential.
PerviousSee* DevPERV
Multi-Family (MFR) and High-Density Residential (HDR)
Directly connected impervious 2.6 Largely based on loading information from Charles USGS loads, SWMM HRU modeling, and NSWQ data setPervious See* DevPERV
Medium -Density Residential (MDR)Directly connected impervious 2.2 Largely based on loading information from Charles USGS loads, SWMM HRU modeling,
and NSWQ data setPervious See* DevPERV
Low Density Residential (LDR) - "Rural"
Directly connected impervious 1.7 Derived in part from Mattson Issac, HRU modeling, lawn runoff TP quality information from Chesapeake Bay and subsequent modeling to estimate PLER for DCIA (Table 14) to approximate literature reported composite rate 0.3 kg/ha/yr.
PerviousSee* DevPERV
Highway (HWY)
Directly connected impervious 1.5 Largely based on USGS highway runoff data, HRU modeling, information from Shaver et al and subsequent modeling to estimate PLER for DCIA for literature reported composite rate 0.9 kg/ha/yr.
Pervious See* DevPERV
Forest (For)
Directly connected impervious 1.7 Derived from Mattson & Issac and subsequent modeling to estimate PLER for DCIA that corresponds with the literature reported composite rate of 0.13 kg/ha/yr (Table 14) Pervious 0.13
Open Land (Open)
Directly connected impervious 1.7 Derived in part from Mattson Issac, HRU modeling, lawn runoff TP quality information from Chesapeake Bay and subsequent modeling to estimate PLER for DCIA (Table 14) to approximate literature reported composite rate 0.3 kg/ha/yr.
PerviousSee* DevPERV
Agriculture (Ag)
Directly connected impervious 1.7 Derived from Budd, L.F. and D.W. Meals and subsequent modeling to estimate PLER for DCIA to approximate reported composite PLER of 0.5 kg/ha/yr.Pervious 0.5
*Developed Land Pervious (DevPERV)-Hydrologic Soil Group A
Pervious0.03
Derived from SWMM and P8 - Curve Number continuous simulation HRU modeling with assumed TP concentration of 0.2 mg/L for pervious runoff from developed lands. TP of 0.2 mg/L is based on TB-9 (CSN, 2011), and other PLER literature and assumes unfertilized condition due to the upcoming MA phosphorus fertilizer control legislation.
*Developed Land Pervious (DevPERV)-Hydrologic Soil Group B
Pervious0.13
*Developed Land Pervious (DevPERV) -Hydrologic Soil Group C
Pervious
0.24
*Developed Land Pervious (DevPERV) -Hydrologic Soil Group C/D
Pervious0.33
*Developed Land Pervious (DevPERV) -Hydrologic Soil Group D
Pervious
0.41
Accounted for in Opti-
Tool
SW Control Long-term Cumulative Performance Curve Concept
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2
Ru
no
ff V
olu
me
Re
du
cti
on
Cu
mu
lati
ve
Ph
os
ph
oru
s L
oa
d R
em
ova
l
Physical Storage Design Capacity, Impervious Surface Runoff Depth (inches)
SW Control Performance Curves Surface Infiltration Practices
rain gardens, swales, basins, etc.(Saturated Soil Infiltration Rate 0.52 in/hr)
TP Volume
Small Rain Garden http://www.flickr.com/photos/cdwilliams1/2915660835/
Larger Stormwater Basin http://www.flickr.com/photos/leonizzy/6232922661/
Accounted for in Opti-
Tool
Unit Cost information for Various SW Controls
SW Control TypeCost ($/ft3) –2016 dollar
Bioretention $ 14.63
Dry Pond $ 6.44
Enhanced Bioretention $ 14.77
Infiltration Basin $ 5.91
Infiltration Chamber $ 60.4
Infiltration Trench $ 11.82
Porous Pavement (Asphalt) $ 5.03
Porous Pavement (Concrete) $ 17.1
Sand Filter $ 16.97
Subsurface Gravel Wetland $ 8.31
Wet Pond $ 6.44
SW Control Development TypeCost
Adjustment Factor
New BMP in Undeveloped Area 1.00
New BMP in Partially Developed Area 1.50
New BMP in Developed Area 2.00
Difficult Installation in Highly Urban Settings 3.00
9
Unit cost is based on control’s storage capacity (ft3) to hold water (e.g., pond volume
+ void space volume) making it straight forward to integrate cost and performance
information, (e.g., $ per pound of P removed).
Accounted for in Opti-
Tool
Estimates of hours of level of effort for Operation
& Maintenance (O&M) has been estimated for each
of the SW control types.
Demonstration Project: Optimization Analysis for 3 Upper Charles Towns
• Conducted by Tetra Tech to evaluate broad SW Management Strategies to inform Permit Development
• Big Picture Key Findings:• The range in estimated costs for implementation of SW controls watershed-wide to achieve a
set phosphorus reduction target is HUGE
• Standardize sizing of controls (one size fits all) will be much more expensive (administrative ease may be unaffordable and unwise)
• Comprehensive optimization process will help identify the best combination of controls, design capacities and locations to achieve required load reduction at least cost
Demonstration Project: Optimization Analysis for 3 Upper Charles Towns
Example Results
0
20
40
60
80
100
120
140
0.00% 10.00% 20.00% 30.00% 40.00% 50.00% 60.00% 70.00% 80.00%
Annual average TP load reduction
To
tal c
os
t (m
illio
n $
)All scenarios evaluated
52%, 26.08
52%, $98 Million
52%, $26 Million
10/25/2016 12
$193,788,094
$151,722,468
$114,715,944
$104,004,002
$97,826,021$85,902,399
$50,000,000
$100,000,000
$150,000,000
$200,000,000
$250,000,000
60% 70% 80% 90% 100%
Esti
mat
ed
Co
nst
ruct
ion
Co
st, $
incl
ud
es
a 3
5%
fo
r e
ngi
ne
eri
ng
and
co
nti
nge
nci
es
Percentage of Impervious Area Treated in Charles River Watershed of Milford, Bellingham & Franklin, MA
Estimated Construction Costs for Structural Stormwater Controls to Achieve a 40 % Reduction in Phosphorus Load form the Charles River Watershed in
Milford, Bellingham & Franklin based on Amount of Impervious Area Treated
10/25/2016 13
1.40
0.91
0.68
0.470.43 0.39
0.29
0.00
0.20
0.40
0.60
0.80
1.00
1.20
1.40
1.60
50% 60% 70% 80% 90% 100%
We
igh
ted
ave
rage
cap
acit
y o
f st
ruct
ura
l co
ntr
ols
–in
che
s o
f ru
no
ff f
rom
imp
erv
iou
s co
ver
Percentage of Impervious Area Treated in CRW of Milford, Bellingham, & Franklin MA
Average Capacity of structural controls needed to achieve a phosphorus load reduction of 40% in the Charles River Watershed of Milford, Bellingham &
Franklin, MA based on the treatment of varying amounts of impervious area
10/25/2016 14
1277
14291516
1624
1848
2034 2040
0
400
800
1200
1600
2000
2400
2800
60% 65% 70% 75% 80% 85% 90% 95% 100%
An
nu
al r
un
off
vo
lum
e r
ech
arge
d b
y In
filt
rati
on
pra
ctic
es
M
G/y
r
Percentage of impervious area treated in CRW of Milford, Bellingham & Franklin MA
Estimated annual stormwater recharge volume by infiltration practices for varying amounts of impervious area treated associated with achieving a 40% phosphorus
load reduction from the Charles River Watershed within Milford, Bellingham & Franklin, MA
2548 MG/yr -Average annual potable water consumption for Milford, Bellingham and Franklin, MA
Opti-Tool: IntroductionOverview of the planning and implementation options
Khalid AlviEnvironmental EngineerTetra Tech, Incorporated
Fairfax, Virginia
Project Background
• Small MS4 General Permit for MA and NH• Phosphorus reduction requirement to meet the Waste Load Allocations for
the impaired watershed
• Phosphorus Control Plan (PCP) • To measure compliance with its phosphorus reduction requirement under
the permit
• Opti-Tool• A tool to facilitate storm water engineers to developing Nutrient
Management Plans such as PCP.
16
Project Background – cont.
• Proven benefits of optimization techniques in stormwater management • Charles River watershed study
• Practical needs by stormwater practitioners• BMP simulation
• BMP optimization
• Independent of ArcGIS
• Simple to use
17
Opti-Tool• A spreadsheet-based
BMP optimization tool• Planning Level Analysis
(EPA Region 1 BMP Performance Curves)
• Implementation Level Analysis (EPA SUSTAIN BMP Simulation and Optimization Engine)
• Customized for EPA Region 1
18
Excel Inputs
Planning Level Input:
Target pollutant load reduction
Watershed land use area
BMP drainage area
Optimization method
Implementation Level Input:
Watershed, land use, pollutants
Potential BMPs representation
BMP treated area
Management objective
Output Postprocessor:
Cost-effectiveness solution
Optimal management options• BMP size and cost
• Treated impervious area
Output Postprocessor:
Cost-effectiveness curve
Optimal management options
• BMP type, size, and cost
Excel Outputs
Excel Solver
SUSTAIN Optimization
Engine
InputText File
BMP Performance
Curve
Opti-Tool: Planning and Implementation Options
Opti-Tool: Example Applications
• Planning Level Analysis• Maximum possible load reduction for all feasible BMP opportunities
• Watershed scale and/or site scale
• Aggregated BMP representation (grouping same BMP types as one unit)
• No BMP nesting (parallel BMPs)
• Cost-effective single solution meeting the numeric target
• Implementation Level Analysis• Optimal combination of different BMP types, sizes, and spatial locations
• Watershed scale and/or site scale
• Aggregated and/or distributed BMP representation
• simple to complex BMP routing network (BMPs in parallel and/or in series)
• Cost-effective solutions (CE-curve) for a range of load reduction targets
Opti-Tool: Region Specific Data
• Precipitation Representation• Long-term hourly data at Logan airport (1992 – 2014)
• Land Representation• Stormwater monitoring data to calibrate the buildup & washoff processes on
impervious cover
• Long-term landuse specific annual average load export rates
• BMP Representation• University of New Hampshire Stormwater Center (UNHSC) BMP monitoring
data to calibrate flow and pollutant loss mechanism in BMPs
• Representative BMP cost information with scaling function
21
Opti-Tool: Precipitation Analysis
• Data Used • 12 weather stations from major urban areas
• Represents climate regions in New England states
• NCDC hourly weather records
• Summary Results• Average annual precipitation varies from 34 in.
to 46 in. with average value of 42.3 in.
• Similar precipitation frequency distribution• 48 percent of the events are < 0.1 inch
• 45 percent of the events are 0.1 to 1.0 inch
• 7 percent are > 1.0 inch
• Boston Logan Airport station is representative22
Opti-Tool: Buildup & Washoff Calibration
• Data Used • National Stormwater Quality Database (NSQD)
• Massachusetts and New Hampshire sites
• 100% impervious drainage areas
• Storm events smaller or equal than 1 inch
• Pollutants (TP and TN)
• Buildup & Washoff Parameterization• Developed computer codes using GA algorithms to identify the parameter
pattern that best fit the observed data
• Calibrated 21 sets of parameters representing different initial conditions
• Performed sensitivity analysis to identify the robust set of parameters
23
Buildup/Washoff: Calibration Plots for TP
24Reference: Technical Memos.pdf
Opti-Tool: HRU Timeseries Development
• Data Used• Selected robust set of pollutant buildup & washoff parameters in
calibrated SWMM model
• Regional representative landuse-based annual average pollutant load export rates (kg/ha/yr)
• Hourly precipitation and PET timeseries (1992 to 2014)
• Summary Results• Adjusted buildup parameters to match the simulated long-term
annual average pollutant loading rate (kg/ha/yr)
• Compared the simulated EMC distribution against the observed EMC distribution for impervious land use types
• Developed HRU hourly timeseries for flow, TP, TN, and TSS 25
26Reference: Technical Memos.pdf
Opti-Tool: HRU Types
27
1. Commercial/Industrial
2. High-Density Residential
3. Medium-Density Residential
4. Low Density Residential
5. Highway
6. Open Land
7. Forest
8. Agriculture
9. Forest Pervious10. Agriculture Pervious11. Developed Land Pervious –
Hydrologic Soil Group A12. Developed Land Pervious –
Hydrologic Soil Group B13. Developed Land Pervious –
Hydrologic Soil Group C14. Developed Land Pervious –
Hydrologic Soil Group C/D15. Developed Land Pervious –
Hydrologic Soil Group D
Opti-Tool: BMP Calibration
• Data Used • BMP design specifications (from the UNHSC)
• BMP monitoring data: flow and water quality (from the UNHSC)
• BMP Parameterization• Developed SUSTAIN models
• Calibrated water quality parameters (1st order decay and underdrain removal rate)
• Compared simulated BMP hydrograph and water quality performance against the observed BMP hydrograph and observed BMP efficiency
• Calibrated structural stormwater BMPs for flow, TP, TN, and TSS
28
Bioretention: Hydrology Calibration
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Time
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w (
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Generated inflow to bio-retention area
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Calibrated BMPDSS outflow
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23
:40
0:0
0
0:2
0
0:4
0
1:0
0
1:2
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Time
Flo
w (
gp
m)
Observed inflow
Generated inflow to bio-retention area
Observed outflow
Calibrated BMPDSS outflow
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Opti-Tool: BMP Performance Curve
• Data Used • Calibrated SUSTAIN model• Calibrated hourly HRUs timeseries (1992 to 2014)
• BMP Simulation• Run BMP scenarios for a range of storage capacity and estimated the
pollutant load reductions• Developed BMP performance curve (pollutant load reduction vs storage
capacity)
• Developed long-term cumulative pollutant load and runoff volume reduction performances for several categories of structural stormwater controls
30
31
Opti-Tool: BMP Types
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1. Bio-filtration
2. Enhanced Bio-filtration with Internal Storage Reservoir3. Dry Pond
4. Grass Swale5. Gravel Wetland6. Infiltration Basin7. Infiltration Chambers8. Infiltration Trench9. Porous Pavement10. Sand Filter11. Wet Pond
Opti-Tool: BMP Cost Function
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• Combination of the Charles River Watershed Association and UNHSC costs estimates
• Modified capital cost assessment (includes a fixed percentage for Design and Contingency Costs)
• Maintenance hours (from the UNHSC)
Reference: Technical Memos.pdf
BMP Type Cost ($/ft3) – 2016
Bioretention $ 15.46
Dry Pond $ 6.8
Enhanced Bioretention $ 15.61
Infiltration Basin $ 6.24
Infiltration Chamber $ 67.85
Infiltration Trench $ 12.49
Porous Pavement (Porous Asphalt Pavement) $ 5.32
Porous Pavement (Pervious Concrete) $ 18.07
Sand Filter $ 17.94
Subsurface Gravel Wetland $ 8.78
Wet Pond $ 6.8
Opti-Tool: Interfaces
Planning Level: Two Approaches
• BMP Storage Capacity • Evaluate the BMP performance for a design criterion (e.g., capture 1 inch
storm size)• Evaluate the changes in water quality benefits as the BMP sizes are changed • Identify the most cost-effective BMP storage capacity that meets the target
pollutant load reduction
• BMP Drainage Area• Determine how much impervious drainage area would require treatment if
specified BMP design capacities were selected• Identify the extent of impervious area to be treated that can provide the
target pollutant load reduction• In this approach, both the BMP storage capacity and BMP cost are fixed.
Opti-Tool: Planning Level
Opti-Tool: Interfaces
Opti-Tool: Implementation Level
38
Opti-Tool: Model Results
• Cost $84.53 million to meet 52.1% average annual TP load reduction target
• Cost saving of $47.5 million (56%) by lowering 10% of the numeric target (42.1%)
0
20
40
60
80
100
120
140
160
0% 10% 20% 30% 40% 50% 60%
Co
st (
Mill
ion
$)
% ReductionAnnual Average Load
All Solutions Best Solutions Target Solution
Target Reduction (%)
Solution Total
Cost (Million $)
Solution Reduction
(%)
52.1% 84.53 52.10%
BMP ID BMP Type BMP Area (ft^2)BMP Storage Depth
(ft)
Treated Impervious Area
(ac)Annual Maintenance (hours) Cost ($)
BMP1 INFILTRATIONBASIN 690000 2.0005 653.85 NOT ASSESSED 17,226,706
BMP2 INFILTRATIONBASIN 580000 2.0005 586.58 NOT ASSESSED 14,480,419
BMP3 INFILTRATIONBASIN 76000 2.0005 62.92 NOT ASSESSED 1,897,434
BMP4 BIORETENTION 432 1.768 0.22 4.55 23,616
BMP5 BIORETENTION 52360 1.768 33.12 685.58 2,862,341
BMP6 BIORETENTION 600000 1.768 495.3 10252.71 32,799,936
BMP7 BIORETENTION 60000 1.768 96.02 1987.61 3,279,994
BMP8 ENHANCEDBIORETENTION 100800 2.28 89.08 NOT ASSESSED 7,175,105
BMP9 SUBSURFACEGRAVELWETLAND 85200 3.2 107.58 2334.49 4,787,558
Benefits of Opti-Tool
• Accessible to all users with Microsoft Excel 2013 software
• Represents actual regional precipitation conditions
• Incorporates best available information on stormwater urban runoff nutrient quality
• Incorporates best available information for estimating long-term cumulative nutrient load and runoff volume reduction performances for 11 categories of structural stormwater controls
• Uses Information which is being shared with other regional tool developers to promote the use of consistent and high quality data
Benefits of Opti-Tool – cont.
• Incorporates representative stormwater control units cost information with scaling function to account for specific conditions and development density
• Includes flexibility to conduct either watershed planning level or detailed site specific design-level analyses
• Performs optimization analyses to determine most cost-effective selection of structural stormwater controls for achieving pollutant loading and runoff flow related reduction targets
Flexible to Adapt for Other EPA Regions
• Develop local weather data• Hourly precipitation
• Daily temperature (min and max)
• Run SWMM model (provided in the installation package)• Local weather data input
• SWMM hourly HRU timeseries output
• Run HRU utility tool (provided in the installation package)• SWMM hourly HRU timeseries input
• Opti-Tool hourly HRU timeseries output
• Update default data (provided in the installation package)• HRU timeseries and local BMP cost function (optional)
Feedback and Other Presentations
• Questions or comments?• Mark Voorhees ([email protected])
• Links to other presentations• https://www.epa.gov/npdes/npdes-stormwater-webcasts