1
Stormwater Elements of Conservation Design for Huntsville
Industrial Park and the Use of Decision Analysis to Select
Appropriate Control Programs
Robert PittDepartment of Civil and Environmental Engineering
The University of AlabamaTuscaloosa, AL 35487
Stormwater Control Categories in the International Stormwater “BMP” Database:
Structural Controls:•Detention ponds•Grass filter strips•Infiltration basins•Media filters•Porous pavement•Retention ponds•Percolation trenches/wells•Wetland basins•Wetland channels/swales•Hydrodynamic devices
Non-Structural Controls:•Education practice•Recycling practice•Maintenance practice•Source controls
WinSLAMM Treatment PracticesInfiltration Trenches
Biofiltrat-ion/Rain Gardens
Cisterns/ rain
barrels
Wet detention
pond
Grass Drainage
Swale
Street Cleaning
Catch-basins
Porous Pavement
Drainage Discon-nection
RoofPaved parking/storageUnpaved parking/storagePlaygrounds
Drivew ays
Sidew alks/w alks
Streets/alleys
Undeveloped areasSmall landscaped areasOther pervious areasOther impervious areasFreew ay lanes/shouldersLarge turf areas
Large landscaped areas
Drainage system
Outfall
Plus, we now have upflow filters and hydrodynamic devices, and are working on other media filters and combination controls
WinSLAMM Summary Data Outputs• Runoff Volume (ft3, percent reduction; and Rv, runoff coefficient), particulate solids (lbs and mg/L), for:- source area total without controls- total before drainage system- total after drainage system-total after outfall controls
• Total control practice costs:- capital costs- land cost- annual maintenance cost- present value of all costs-annualized value of all costs
• Receiving water impacts due to stormwater runoff:- calculated Rv with and without controls- approximate biological condition of receiving water (good, fair, or poor)- flow duration curves (probabilities of flow rates for current model run and without controls)
2
Detailed Data Outputs for Each Event
Runoff Volume (ft3), source area contributions, particulate solids (lbs and mg/L), pollutants (lbs and mg/L)- by source area for each rain event- land use total- summary for all rains- total for land use and for each event- outfall summary, before and after drainage system and before and after outfall controls- Rv (runoff volume only)- total losses (runoff volume only)- calculated CN (runoff volume only)
3
Additional Details Available for Each Event (with summaries)
rain duration (hours), rain interevent period (days), runoff duration (hours), rain depth (inches), runoff volume (ft3), Rv, average flow (cfs), peak flow (cfs), suspended solids (lbs and mg/L)
The WinSLAMM batch editor can be used to automatically run a large number of files, usually for integration into a GIS-based map.
N
Stormwater Investigation City of Racine, Wisconsin
November, 2002
Critical Loading Rates
43247
RR07000
RR13000
NL03001
NL03002Nonreg
Nonreg
NL02000
NL03000
NL03003NL03004
NL03006
IW01000
NL03005
NL01000
NL05000NL08019
NL04000
NL06001
NL08018
NL08023
NL06002NL06003
NL06000
NL06004
NL08017
NL08015NL07000NL07001
NL08016
Nonreg
NL08000
NL08001
NL08004
NL08021
NL08022NL08020
NL08002
RR06000
RR03000
NL08006
NL08003
Nonreg
RR01000
RR06000 NL09000
NL08007 NL08005
NL08014
RR02000
NL08008
NL10002NL10001
NL10000
NL10003RR04000
NL08010NL08011
NL08009
RR46003
NL08012
RR46002
RR47002NL08013
RR47001
RR46004
RR53000
RR47000
NonregRR61000
RR08000
RR50000RR46001
RR22000
RR09000 NL11000
RR10000RR48000
RR46000
RR49000
RR51000
RR11000RR12003
RR15012RR12000
RR22001
RR15014
RR45000
RR44000RR57000RR21000
RR59000
SL12000RR12002
RR15013
RR58000RR14000
RR56000
RR16000
SL13000
RR55000
RR15005
RR52000RR43000
Nonreg
RR33000RR12001RR34000RR23000RR15000
RR17000
SL14000
RR54000
RR15006
RR15000
RR15010
RR24000
RR15011
RR25000
RR32000RR15001
RR18000RR15004 SL15000RR15002
RR15008RR35000
RR26000 SL16000
RR36000
RR15003 RR31000RR27000
RR19000
SL17000
RR15007
RR20000
RR36001RR20001RR15016
RR28000
RR15009
RR29000
RR38000RR30000
RR37001
RR15017
RR60000
RR41000
RR40000
SL17001RR42000
RR37002RR39000RR37000
RR37003
RR36002RR37004
SL17002
RR37005RR37006
RR37007RR37008
SL19005
RR40001RR37009
RR37010
SL19003
RR37011 SL25000
SL18000
RR37012
RR37013
SL19002
RR37014
RR37030
SL19004
RR37015 SL19000
RR37016SL19001
SL19006
RR37017
SL23019
RR37018RR37019
PR12000
Nonreg
RR37021
SL20000
SL23004
SL22001SL23016 SL23015 SL21000
RR37022
SL23032RR37023
RR37024
RR37025
SL23035
PR08001
SL23033
SL23017RR37026
PR07000
SL23018
PR08001SL23028
RR37027
RR37028
SL22000
SL23002PR08002 SL23002
SL23000
SL23005
PR08000
SL23034SL23002PR08003
SL23013
SL23036
SL23029 SL23006SL23030
SL23014
SL23008
RR37029
SL23007
SL23012 SL23003
SL23001
SL23020SL23021SL23001
SL23011SL23027
SL23010SL23011
SL23023
SL23024
SL23025
PR02000
SL23022
SL23023
SL23024SL23024SL23026
PR01000
SL24001
PR06004PR06004
PR03000
PR06003
PR06000
SL23024
PR06001
PR06004
PR09000
Nonreg
Nonreg
PR06002PR10000
PR11000PR05000
PR04000
Nonreg
1600 0 1600 3200 4800 Feet
Corporate LimitsWaterSubbasins
Critical Loading RatesHighMHModerateMLLow
$ 8.7444%1810829145306855501704215207843193328Cost Example - P 50 percent
$ 8.7418%7243325812234220681686307614425257Cost Example - P 20 percent
$ 1.2440%2325151865891000119109223413136146Cost Example - G
n/a0%00000374135246545Cost Example -Base Case No Controls
Cost per lb
Sediment Reduced
% Part.
Solids Reduc.
Sub Basin Total
Present Value Cost
Sub Basin Total
Annual Cost
Sub Basin Maint. Cost
Sub Basin Land Cost
Sub Basin
Capital Cost
Partic. Solids Yield (lbs)
Runoff Volume
(cf)
File Name
WinSLAMM can also calculate life-cycle costs and compare different control programs to obtain unit removal costs with the batch processor: Decision Analysis
• With so much data available, and so many options that can be analyzed, how does one select the “best” stormwater control program?
• The least costly that meets the objective?
4
Possible, if only have one numeric standard:
If 80% SS reduction goal, the least costly would be wet detention. In this example, grass swales, street cleaning, and catchbasins cannot reach this level of control. If 40% SS reduction goal, then grass swales wins.
If multiple goals, then possibly not as clear and need a more flexible approach. Consider the following example (a conservation design industrial park in Huntsville, AL):
Conservation Design Elements for Huntsville Industrial Park
• Grass filtering and swale drainages• Wet detention ponds• Bioretention and site infiltration devices• Critical source area controls• Pollution prevention through material
selection
Grass Filtering of Stormwater Sediment
5
Runoff from Pervious/
impervious area
Trapping of sedimentsand associated pollutantsReducing velocity of
runoff
Infiltration
Reduced volume and treated runoff
Sedimentparticles
Particulate Removal in Shallow Flowing Grass Swales and in Grass Filters
WinSLAMM Input Screens for Grass Swales
Typical stable grass swales (wide and shallow) Grass Swales Designed to Infiltrate Large Fractions of Runoff (AL and OR).
Also incorporate grass filtering before infiltration
6
Swales can be both interesting and fit site development objectives.
WI DNR photo
Conventional curbs with inlets directed to site swales
Head (0ft)
2 ft
25 ft
6 ft
3 ft
116 ft75 ft
Test Date: 10/11/2004
Zoysia grass swale
Blue grass
0
200
400
600
800
1000
1200
0 1 2 3 4 5 6distance (ft)
Tota
l Sus
pend
ed S
olid
s(m
g/L)
1%_10gm1%_15gm1%_20gm3%_10gm3%_15gm3%_20gm5%_10gm5%_15gm5%_20gm
Head works
7
PSD 11-11-04
0
10
20
30
40
50
60
70
80
90
100
0.1 1 10 100 1000
Particle size (um)
Volu
me
(%)
0ft 2ft3ft6ft25ft75ft116ft
TSS: 153 mg/L (head)
Decreasing particle sizes with flow distance
Particulate trapping in grass filters (high initial concentrations and shallow flows)
Wet Detention Ponds
3.0 (approximate maximum pond elevation, or as determined based on flood flow analysis). Additional storage and emergency spillway may be needed to accommodate flows in excess of the design flood flow.
9
2.5 (invert elevation of flood flow broad-crested weir). Normal maximum elevation during one and two year rains.
8271.56
1.0 (normal pool elevation, and invert elevation of 30o v-notch weir)
50.7540.530.2520.151
Full-Sized Pond Area (acres)
Pond Elevation
(ft)
Wet Detention Pond to Treat Runoff from Area
8
Suspended Solids Control at Monroe St. Detention Pond, Madison, WI (USGS and WI DNR data)
Consistently high TSS removals for all influent concentrations (but better at higher concentrations, as expected)
Infiltration/Biofiltration
• Infiltration trenches• Infiltrating swales• Infiltration ponds• Porous pavement• Percolation ponds• Biofiltration areas (rain gardens, etc.)
9
Porous paver blocks have been used in many locations to reduce runoff to combined systems, reducing overflow frequency and volumes (Germany, Sweden, and WI).
Small depressions graded near parking lots or buildings for infiltration (older method, using regular turf grass) (MD and WI).
Parking lot medians easily modified for bioretention (OR and MD).
WinSLAMM Input Screen for Biofilters
10
Parking lot bioretention areas for roof runoff and paved area runoff reduction (Portland, OR).
Bioretention area overflow directed to conventional storm drainage system.
Groundwater ContaminationThe potential for groundwater contamination associated
with stormwater infiltration is often asked.
Book published by Ann Arbor Press/CRC, 219 pages. 1996, based on EPA research and NRC committee work.
Road cut showing direct recharge of Edwards Aquifer, Austin, TX
http://civil.eng.ua.edu/~rpitt/Publications/BooksandReports/Groundwater%20EPA%20report.pdf
Infiltration Rates in Disturbed Urban Soils (AL tests)
Sandy Soils Clayey Soils
Field measurements have shown that the infiltration rates of urban soils are strongly influenced by compacted, probably more than by moisture levels.
11
Soil Modifications and Rain Gardens
Proper design will minimize groundwater contamination potential
Critical Source Area Control
Multi-Chambered Treatment Train for large critical source area control Pilot-Scale MCTT Test
Results
12
Wisconsin Full-Scale MCTT Test Results
>75 (<0.2 µg/L)98 (<0.05 µg/L)Pyrene
>65 (<0.2 µg/L)99 (<0.05 µg/L)Phenanthrene
>75 <0.1 µg/L)>95 (<0.1 µg/L)Benzo (b) fluoranthene
90 (15 µg/L)91 (<20 µg/L)Zinc
nd (<3 µg/L)96 (1.8 µg/L)Lead
65 (15 µg/L)90 (3 µg/L)Copper
>80 (<0.1 mg/L)88 (0.02 mg/L)Phosphorus
85 (10 mg/L)98 (<5 mg/L)Suspended Solids
Minocqua (7 events)
Milwaukee (15 events)
(median % reductions and median effluent quality)
Upflow filter insert for catchbasins
Able to remove particulates and targeted pollutants at small critical source areas. Also traps coarse material and floatables in sump and away from flow path.
Upflow FilterTM patent pending
Pelletized Peat, Activated Carbon, and Fine Sand
y = 2.0238x0.8516
R2 = 0.9714
0
5
10
15
20
25
0 5 10 15 20
Headloss (inches)
Flow
(gpm
)
Pollution Prevention through Substitution of Building Materials
• Pavement• Treated wood• Roofing materials
13
Total: 12,200
Dissolved: 11,900
Total: 302Dissolved:
35
Not given Rusty galvanized roof
< 17< 17Total: 166Dissolved:
128
Built-up roof (plywood + roofing paper/tar)
LeadZincCopper
Roof Runoff Concentrations
(µg/L)
The Source Loading and Management Model (WinSLAMM)
• Developed during past 25 years during EPA, state, and Canadian funded research.
• Identifies pollutant sources during different rain and climatic conditions.
• Prioritizes subwatersheds and critical source areas.
• Evaluates alternative development scenarios, pollution prevention, and combinations of source area and outfall control options.
A lot of stormwater flow and quality data has been collected during past several decades
It is straight-forward and important to compare these observations with model assumptions
14
Major Stormwater Controls Currently Available with WinSLAMM (in addition
to development options)• Public works practices (street and catchbasin
cleaning, grass swales)• Biofiltration (french drains, infiltration
trenches, bioretention, rain gardens, percolation ponds, etc.)
• Sedimentation (hydrodynamic devices, wet detention ponds, etc.)
• Beneficial uses (rain barrels, cisterns, and pond storage for irrigation or other use)
Additional Controls and Processes being Added Based on Recent and On-
going Research• Treatment trains• Media filtration (both upflow and conventional
filters)• Multiple ponds• Grass filters• Evapotranspiration and multiple soil layers• Interfacing with SWMM (replacement of
RUNOFF block) for detailed drainage system hydraulics
Huntsville Industrial Park Main Drainage Subareas
• Roofs (directly connected): 18.4 acres• Paved parking (directly connected): 2.3 acres• Streets (1.27 curb-miles): 3.1 acres • Small landscaped areas (B or sandy-loam soils, but assumed silty soils due to compaction): 10.0 acres• Large undeveloped area (B or sandy-loam soils, but assumed silty soils due to compaction): 60.2 acres• Isolated areas (sinkholes): 4.6 acres
Subarea A site characteristics:
15
On-site bioretention swales:
These small drainages collect the on-site water from the paved parking and roofs and direct it to the large natural swales. These were assumed to have the following general characteristics: 200 ft long, with 10 ft bottom widths, 3 to 1 (H to V) side slopes (or less), and 2 inches per hour infiltration rates. One of these will be used at each of the 6 sites on the eastern edge of this subarea.These swales will end at the back property lines with level spreaders (broad crested weirs) to create sheetflow towards the large drainage swale, if possible.
Large regional drainage swale:
There is one long regional drainage swale in this subarea that collects the sheetflows from the bioretention swales from each site and directs the excess water to the ponds on the southern property edge. This swale is about 1700 feet long, on about a 2.6% slope, and will be 50 ft wide. It will also have 3 to 1 (H to V) side slopes, or less, and have 1 inch per hour infiltration rates. The bottom of the swale will be deep vibratory cultivated during proper moisture conditions to increase the infiltration rate, if compacted. This swale will also have limestone check dams every 100 ft to add alkalinity to the water and to encourage infiltration. The vegetation in the drainage should be native grasses having deep roots and be mowed to a height of about 6 inches, or longer. Any cut grass should be left in place to act as a mulch which will help preserve infiltration rates. The swale should have a natural buffer on each side at least 50 ft wide. Any road or walkway crossings over the grassed waterway areas should be on confined to a narrow width.
Wet detention pond:
A wet detention pond will be located across the main road next to the southern property boundary. The runoff from the totally connected and curb and gutter drained industrial area in the southwest corner of the site will enter the pond directly opposite from the discharge point. The regional swale will also direct excess water into the pond far from the discharge point.
Calculated Performance of Stormwater Options using Typical Rain Year (1976): Subarea A Example
2,230 (97)191.85 x 106 (72%)Pond, swale, and site bioretention
4,500 (95)371.97 x 106 (65%)Small pond, swale, and site bioretention
3,030 (96)182.69 x 106 (52%)Pond and swale
35,100 (59)1902.93 x 106 (48%)Swale only
5,740 (93)332.81 x 106 (47%)Small pond and swale
70,600 (18)2704.17 x 106 (24%)Site bioretention only
7,640 (91)235.34 x 106 (5%)Pond only
86,3002505.60 x 106Base conditions (no controls)
Particulate Solids Yield (lbs/year) (% reduction compared to base conditions)
Particulate Solids Concentration (mg/L)
Runoff Volume (ft3/year) (% reduction compared to base conditions)
Stormwater Control Options
16
11 x 106 (56%)25 x 106Total site
5.8 x 106 (50%)11 x 106Off-site pond, swale, and site bioretention
D (including off site area)
0.83 x 106 (68%)2.5 x 106Pond and swaleC
1.7 x 106 (69%)5.4 x 106Small pond and swaleB
2.5 x 106 (61%)6.3 x 106Pond, swale, and site bioretention
A
With ControlsBase Conditions
Proposed Stormwater Components
Drainage Area
Runoff Volume (ft3/year)
26180Total site
26160Off-site pond, swale, and site bioretention
D (including off site area)
8120Pond and swaleC
37160Small pond and swaleB
28250Pond, swale, and site bioretention
A
With Controls
Base Conditions
Proposed Stormwater Components
Drainage Area
Particulate Solids Concentration
(mg/L)
19,000 (93%)
290,000Total site
9,250 (92%)
120,000Off-site pond, swale, and site bioretention
D (including off site area)
1,200 (94%)
19,000Pond and swaleC
3,800 (93%)
54,000Small pond and swaleB
4,400 (96%)
98,000Pond, swale, and site bioretention
A
With Controls
Base Conditions
Proposed Stormwater Components
Drainage Area
Particulate Solids Discharge (lb/year)
Sediment Reductions
Volume Reductions
17
1) Specific criteria or limits that must be met.
It is possible to simply filter out (remove) the options that do not meet all of the absolutely required criteria. If the options remaining are too few, or otherwise not very satisfying, continue to explore additional options. The above examples only considered combinations of 3 types of stormwater control devices, for example. There are many others that can also be explored. If the options that meet the absolute criteria look interesting and encouraging, then continue.
Decision Analysis Approaches
2Yes9445,698Option 8Small pond, reg. swale and biofilter
1Yes9040,217Option 7Small pond and reg. swale
4Yes9754,622Option 6Pond, reg. swale and biofilter
3Yes9449,142Option 5Pond and reg. swale
n/aNo7374,439Option 4Half-sized pond
n/aNo169,710Option 3Site Biofilter
n/aNo5530,008Option 2Regional Swale
5Yes8683,364Option 1Pond
Rank based on annual
cost
Meet 80% particulate solids reduction goal?
Reduction in SS Yield (%)
Total Annual Cost ($/yr)
Stormwater Treatment Option
Control Options Meeting 80% SS Reduction Requirement, Ranked by Cost
2) Goals that are not absolute (based on methods developed by Keeney, R.L. and H. Raiffa. 1976. Decision Analysis with Multiple Conflicting Objectives. John Wiley & Sons. New York.)
Utility curves and tradeoffs can be developed for the remaining attributes, after all the absolutely required goals are met. Theabove example includes attributes of several different types:
- costs- land requirements- runoff volume (volumes, habitat responses, andrates)
- particulate solids (reductions, yields and concentrations)
- particulate phosphorus (reductions, yields and concentrations)
- total zinc (reductions, yields and concentrations) Sum = 1.0
0.1245.5 to 25 lbs/yrPart. Phosphorus yield (lbs/yr)
0.0762,183 to 10,192 lbs/yr
Particulate solids yield (lbs/yr)
0.1830 to 0.05 %% of time flow >10 cfs0.0570.5 to 4 %% of time flow >1 cfs0.3010.06 to 0.29Rv 0.0852.3 to 4.5 acresLand needs (acres)
0.202$40,217 to 83,364Total annual cost ($/year)
Trade-offs between
remaining attributes
Attribute ranks for selection
(after absolute goals are met)
Range of attribute value for acceptable
options
Attribute
Attribute Value Ranges, plus Example Ranks and Trade-offs(ranks and trade-offs could vary for different interested parties)
18
• Volumetric runoff coefficient (Rv) as an indicator of habitat quality and aquatic biology stress:
Attribute Expected UtilityValue Habitat Value
Condition
<0.1 Good 1.00.1 to 0.25 Fair 0.750.26 to 0.50 Poor 0.250.51 to 1.0 Really lousy 0
Utility Curves for Different Attributes (technically based, would not vary for different interested parties)
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
1 10 100
Directly Connected Imperv Area (%)
Rv
(san
dy s
oils
)
Relationship Between Directly Connecting Impervious Area (%) and the Calculated Rv for Each
Soil Type
00.10.20.30.40.50.60.70.80.9
1
1 10 100Directly Connected Impervious Area (%)
Rv
Sandy Soil Rv Silty Soil Rv Clayey Soil Rv
GoodFair
Poor
• Total annual cost: straight line, with $83,364 = 0 and $40,217 = 1.0.
• % of time flow >10 cfs Utility value
<0.05 1.00.05 - 1 0.751.1 – 2.5 0.25>2.5 0
Example Utility Values for Other Attributes:
19
• Part. Phosphorus yield (lbs/yr): straight line, with 25 lbs/yr = 0 and 5.5 lbs/yr = 1.0
• Land needs (acres): straight line, with 4.5 acres = 0 and 2.3 acres = 1.0
• Particulate solids yield (lbs/yr): straight line, with 10,192 lbs/yr = 0 and 2,183 lbs/yr = 1.0
• % of time flow >1 cfs Utility value<1 1.01 – 3 0.753.1 – 10 0.25
>10 0
Example Utility Values for Other Attributes (cont):
0.77100.764,12512.30.8745,698Option 8Small pond, reg. swale and biofilter
0.41170.416,93712.3140,217Option 7Small pond and reg. swale
1.05.51.02,18304.50.6754,622Option 6Pond, reg. swale and biofilter
0.77100.764,13304.50.7949,142Option 5Pond and reg. swale
025010,19204.5083,364Option 1Pond
0.120.070.080.20Tradeoff Value
Phos.utility
Part. Phos. Yield
(lbs/yr)
Part. Solids utility
Part. Solids Yield
(lbs/yr)
Land utility
Land Needs for SW
mgt (acres)
Cost utility
Total Annual
Cost ($/yr)
Stormwater Control Option
Attribute Values and Associated Utilities for Example
1.001.00.81.00.07Option 8Small pond, reg. swale and biofilter
0.750.050.7520.750.15Option 7Small pond and reg. swale
1.001.00.51.00.06Option 6Pond, reg. swale and biofilter
1.000.7520.750.15Option 5Pond and reg. swale
0.750.050.2540.250.29Option 1Pond
0.180.050.30Tradeoff Value
High flow utility
% of time flow >10
cfs
Mod flow
utility
% of time
flow >1 cfs
Rv utilityVolumetric Runoff
Coefficient (Rv)
Stormwater Control Option
Attribute Values and Associated Utilities for Example (cont.)
0.0920.770.0530.760.0810.1740.87Option 8Small pond, reg.
swale and biofilter
0.0490.410.0290.410.0810.201Option 7Small pond and
reg. swale
0.121.00.071.0000.1340.67Option 6Pond, reg. swale
and biofilter
0.0920.770.0530.76000.1580.79Option 5Pond and reg.
swale
00000000Option 1Pond
0.120.070.080.20Tradeoff Value
Phosfactor
Phos. utility
Part. factor
Part. utility
Land factor
Land utility
Cost factor
Cost utility
Stormwater Control Option
Calculation of Factors for Each Option(Attribute Utility times Attribute Trade-off)
20
10.92900.181.00.051.00.301.0Option 8Small pond, reg. swale and biofilter
30.75550.1350.750.03750.750.2250.75Option 7Small pond and reg. swale
20.85400.181.00.051.00.301.0Option 6Pond, reg. swale and biofilter
4 0.74550.181.00.03750.750.2250.75Option 5Pond and reg. swale
50.22250.1350.750.01250.250.0750.25Option 1Pond
0.180.050.30Tradeoff Value
Over-all
Rank
Sum of factors
High flow
factor
High flow
utility
Mod flow
factor
Mod flow
utility
Rv factor
Rv utility
Stormwater Control Option
Calculation of Factors for Each Option (cont.), Sum of Factors, and Overall Rank Conclusions
• Calibrated and verified stormwater models can be used to develop a great deal of information concerning many different stormwater management options.
• Regulations and criteria also need to have different formats to acknowledge site specific problems and objectives.
• The use of clear and flexible decision analysis techniques, as outlined in this presentation, is therefore important when selecting the most appropriate stormwater control program for a site.
Pitt, et al. (2000)
• Smallest storms should be captured on-site for reuse, or infiltrated
• Design controls to treat runoff that cannot be infiltrated on site
• Provide controls to reduce energy of large events that would otherwise affect habitat
• Provide conventional flood and drainage controls
Combinations of Controls Needed to Meet Many Stormwater Management Objectives Acknowledgements
The authors would like to acknowledge the support of the Tennessee Valley Authority (TVA), Economic Development Technical Services, and the Center for Economic Development and Resource Stewardship (CEDARS) of Nashville, TN, which has allowed us to develop extensions to WinSLAMM to enable the use of a decision analysis framework in evaluating alternative stormwater management options. The Stormwater Management Authority of Jefferson County, AL, is also acknowledged for their recent support that enabled the cost analyses to be added to WinSLAMM
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