Appendix A 

Summary of State Construction and Development 

Requirements 
A-1 

Appendix A: Summary of state construction and development requirements 

State requirements—SUMMARY 

State 

Sediment basin storage volume 

(ft3/acre drained) Sediment basin (design parameters) Sediment basin—notes/references Numeric standard 

Alabama 1,800 (EPA 2007) 

(1) 8-hour detention time for sites > 5 acres (EPA 2007) (2) 67 cy/acre (1,809 ft3) - (Alabama Handbook for Erosion 

Control, Sediment Control and Stormwater Management on Construction Sites and Urban Areas June 2003, Revised 1-06) 

The 2004 TDD Section 7 notes: a sediment basin storage volume of 3,600 ft3/acre 

drained, and sediment basin requirements for drainage areas > 10 acres. 

Statewide standard varies wbackground, < 50 NephelomTurbidity Units (NTUs) abovbackground. The EPA literanoted “None.” The 2002 TDAppendix A notes: Turbidity NTU. Turbidity limits as set the Alabama Department of Environmental ManagemenNTUs above background foAlabama waterbody with a FWildlife classification (AlabaDepartment of EnvironmentManagement 2001). PG Environmental (PG) determthe Alabama Department of Environmental ManagemenDivision Water Quality Prog(2006) states in its specific wquality criteria Section 335-6that there shall be no turbidithan natural origin and that case shall turbidity exceed 5above background. 

Alaska 3,600 (2004 TDD Section 7) 

The EPA 2007 literature referenced the CGP and noted a sediment basin volume of 1,800 ft3/acre plus 1.5 ft for sediment accumulation - generally designed to remove medium silt (62 microns) particles. 

The 2004 TDD Section 7 notes sediment basin requirements for drainage areas > 10 

acres. 2002 water quality standards specify that all stormwater treatment devices shall be designed based on the 2-year, 6-hour rain event (assume runoff), and the Best Management Practice (BMP) must also be capable of removing particles greater than 20-microns during such an event. 

The 2002 TDD Appendix A total suspended solids (TSSmicrons. The EPA 2007 liternotes “None.” 

Arizona 

3,600 (EPA 2007; 2004 TDD Section 7) 

Sizing based on a 2-year, 24-hour event (EPA 2007) 

The 2004 TDD Section 7 notes sediment basin drainage requirements for drainage areas > 10 acres. 

None (EPA 2007) 
A-2 

State requirements—SUMMARY 

State 

Sediment basin storage volume 

(ft3/acre drained) Sediment basin (design parameters) Sediment basin—notes/references Numeric standard 

Arkansas 

3,600 (EPA 2007; 2004 TDD Section 7) 

Temporary or permanent sediment basins shall be based on either the smaller of 3,600 ft3/acre, or a size based on the 

runoff volume of a 10-year, 24-hour storm event (EPA 2007). 

The 2004 TDD Section 7 notes sediment basin requirements for drainage areas > 10 

acres. 

PG estimated post-construcstandard only. A goal of 80 removal of TSS from these (e.g., stormwater detention structures-including wet ponwhich exceed predevelopmeshould be used in designing installing, where practicable 2007; state literature). 

California 

3,600 (EPA 2007; 2004 TDD Section 7) 

Other design standards include a settling velocity approach, where the precipitation intensity for a 10-year, 6-hour rain event is used (EPA 2007). 

The 2004 TDD Section 7 notes sediment basin requirements for drainage areas > 10 

acres. 

California’s draft CGP includturbidity effluent levels of 1,0If Active Treatment Systems used, the daily flow-weighteaverage is 10 NTU and the maximum for any single samNTU. 

Colorado 1,800 general/3,600 transportation N/A 

The 2004 TDD Section 7 notes sediment basin requirements of 1,800 ft3/acre drained. 

The EPA 2007 literature notes sediment basin sizing of 3,600 ft3/acre for Colorado 

Department of Transportation (CDOT). 

None (EPA 2007) 
A-3 

State requirements—SUMMARY 

State 

Sediment basin storage volume 

(ft3/acre drained) Sediment basin (design parameters) Sediment basin—notes/references Numeric standard 

Connecticut 3,600 (EPA 2007) The EPA 2007 literature notes basin sizing of 3,600 ft3/acre. 

The 2004 TDD Section 7 notes a sediment basin storage volume of 1,800 ft3/acre 

drained. The EPA, 2007 literature noted that sediment basins required for sites greater than 2 acres. 

PG estimated no numeric stfor active construction sites review of state literature. Th2007 literature notes 80% T2004 Connecticut StormwatQuality Manual, Chapter 6 sThe State of Connecticut haadopted the 80 percent TSS goal based on EPA guidancwidespread use as a target quality performance standar2004 Connecticut ConstructGeneral Permit for Stormwadischarges noted that the 80 TSS removal was for postconstruction. The 2002 TDD Appendix A notes an 80 perreduction. 

Delaware 

3,600 (EPA 2007; 2004 TDD Section 7) 

N/A 

The 2004 TDD Section 7 notes sediment basin drainage requirements for drainage areas > 10 acres. 

PG estimated no numeric stThe EPA 2007 literature sta“None.” The 2002 TDD Appnotes an 80 percent TSS rehowever, PG determined froliterature that this was a posconstruction standard. 

Florida 

3,600 (EPA 2007; 2004 TDD Section 7) 

N/A 

The 2004 TDD Section 7 notes sediment basin drainage requirements for drainage areas > 10 acres. 

PG estimated no statewide standard. The EPA 2007 litestates “None.” The 2002 TDAppendix A notes some stafor specific regions, but no srequirements. 

Florida, DEP, Northern District (only applies in NW Florida) 

The 2002 TDD Appendix A 80 percent TSS reduction. 
A-4 

State requirements—SUMMARY 

State 

Sediment basin storage volume 

(ft3/acre drained) Sediment basin (design parameters) Sediment basin—notes/references Numeric standard 

Florida, South Florida Water Management District (General, Standard General, Noticed General and Individual Permits) Florida, Southwest Florida Water Management District Florida, St. Johns River Water Management District 

The 2002 TDD Appendix A turbidity less than 29 NTU. 

Florida, Suwannee River Water Management District 

The 2002 TDD Appendix A 80 percent TSS reduction. 

Georgia 

1,800 (EPA 2007; 2004 TDD Section 7) 

The 2002 TDD Appendix A notes water runoff from 25-year, 24-hour storm event shall be treated for water quality management. PG assumed the 25-year storm event is for the emergency spillway per the 2004 TDD (“Typical return periods vary between 25 and 100 years, with 25 years recommended by the USDOT”). 

Statewide standard varies wbackground. Cannot increasturbidity by more than 25 NTwarm waters and 10 NTU in water trout streams. Allowabturbidity in effluent varies basite size and receiving streadrainage area (EPA 2007). TDD Appendix A notes turbto 25 NTUs. 

Hawaii 3,600 (EPA 2007) 

Basin sizing for a 2-year, 24-hour storm event for drainage areas > 10 acres (EPA 

2007). 

No numeric requirements fostormwater pollutant removabeen established at the statbut regional and municipal regulations are in place (EP

Idaho 

3,600 (EPA 2007; 2004 TDD Section 7) 

Basin sizing for a 2-year, 24-hour storm event for drainage areas > 10 acres (EPA 2007). 

The 2004 TDD Section 7 notes sediment basin drainage requirements for drainage areas > 10 acres. 

None. None listed in EPA 202002 TDD Appendix A. 
A-5 

State requirements—SUMMARY 

State 

Sediment basin storage volume 

(ft3/acre drained) Sediment basin (design parameters) Sediment basin—notes/references Numeric standard 

Illinois 3,600 (2002 TDD Appendix A) No sizing criteria in permit (EPA 2007). The 2002 TDD Appendix A notes 3,600 ft3/acre. 

The 2002 Illinois Urban Manual states that the basin requirements shall be based on a 2-year, 24-hour storm or 134 cubic yards/acre (i.e., 3,600 ft3/acre)—whichever is greater (EPA 2007). General NPDES Permit No. ILR10 5/30/2003 notes that “The management practices, controls and other provisions contained in the stormwater pollution prevention plan must be at least as protective as the requirements contained in Illinois Environmental Protection Agency’s Illinois Urban Manual, 2002.” 

None (EPA 2007) 

Indiana 1,800 (2004 TDD Section 7) 

No sizing criteria in permit (EPA 2007). The 2004 TDD Section 7 states that for a state program that did not note a sediment basin size, EPA assumed based on best professional judgment (BPJ) that the baseline size was 1,800 ft3/acre. 

Sediment basin requirements exist for some areas in State (EPA 2007). 

Only in certain parts of India80 percent of TSS removal County). (EPA 2007). 

Iowa 

3,600 (EPA 2007; 2004 TDD Section 7) 

The 2002 permit states that a sediment basin shall be installed for drainage area more than 10 acres disturbed. (Flows from upland areas that are undisturbed may be diverted around the basin) (EPA 2007). 

The 2004 TDD Section 7 notes sediment basin drainage requirements for drainage areas > 10 acres. The EPA 2007 literature 

notes: The 2006 Iowa Construction Site Erosion Control Manual states that the size of the sediment basin, is as measured from the bottom of the basin to the principal spillway and should provide at least 3,600 ft3 of 

storage per acre of drainage. This provides storage equal to 1 inch of runoff per acre. Likewise, 1,800 ft3 amounts to 1/2 inch of 

sediment storage per acre. The basin should be cleaned when the volume of sediment reaches 900 ft3/acre. At this time, the cleanout 

shall be performed to restore the original design capacity of the basin. At no time should the sediment level be permitted to build higher than 1 foot below the principal outlet. 

PG estimated no numeric stThe EPA 2007 literature sta“None.” The 2002 TDD Appnotes an 80 percent TSS rehowever, PG could not confthis standard was for active construction sites. 
A-6 

State requirements—SUMMARY 

State 

Sediment basin storage volume 

(ft3/acre drained) Sediment basin (design parameters) Sediment basin—notes/references Numeric standard 

Kansas 

3,600 (EPA 2007; 2004 TDD Section 7) 

Kansas 1/30/07 CGP Definitions and Acronyms pages states, “Sediment Basin Design Criteria requires sedimentation structures that receive runoff from 10 acres or more of disturbed area to provide at least 3,600 ft3 of storage per acre of 

area drained into the sediment basin. KDHE may approve alternate storage volumes if significant portions of undisturbed area drain to the sediment basin.” 

The 2004 TDD Section 7 notes sediment basin drainage requirements for drainage areas > 10 acres. The EPA 2007 literature 

notes that the 2007 permit requires a storage capacity of 3,600 ft3/acre and the Sediment 

Basin Design Criteria in the permit states, “rational method or other equivalent runoff calculations based on storage of a 2.6 inch rainfall event with a minimum runoff coefficient of 0.77 for disturbed acreage and appropriate runoff coefficients for undisturbed acreage must be provided to determine the revised storage volume requirement.” The field guide for Missouri and Kansas says that for drainage areas of 20 acres or less, the sediment storage shall be 1,800 ft3/acre with 

a detention time of at least 24 hours (EPA 2007). 

None (EPA 2007) 

Kentucky 

3,600 (EPA 2007; 2004 TDD Section 7) 

The 2002 permit requires a basin sizing of 3,600 ft3/acre for drainage locations >10 

acres (EPA 2007). The EPA 2007 literature notes in the 2007 Draft Kentucky BMP Manual requires basin sizing of 3,600 ft3/acre, not to exceed 10 acre-feet for areas 5 to 120 acres with the goal to provide a detention time of 24 to 48 hours and 80 percent TSS reduction for the 10-year, 24-hour storm. 

The 2004 TDD Section 7 notes sediment basin drainage requirements for drainage areas > 10 acres. 

PG noted that there was onnumeric standard requiremeJefferson County and no stastandard. 80% TSS removaJefferson (EPA 2007). The 2Appendix A notes a goal of percent TSS reduction (compre-construction levels). A gpercent removal of TSS from that exceed predevelopmen(2002 General KPDES PermStormwater Point Source Discharges, Construction Acpage IV-2). 
A-7 

State requirements—SUMMARY 

State 

Sediment basin storage volume 

(ft3/acre drained) Sediment basin (design parameters) Sediment basin—notes/references Numeric standard 

Louisiana 

3,600 (EPA 2007; 2004 TDD Section 7) 

For 10 or more disturbed acres, either the smaller of 3,600 ft3/acre or a 2-year, 24-

hour storm. This does not apply to flows from off-site areas and flows from on-site areas that are either undisturbed of have undergone final stabilization where such flows are diverted around the sediment basin (EPA 2007). 

The 2004 TDD Section 7 notes sediment basin drainage requirements for drainage areas > 10 acres. For drainage locations 

serving less than 10 acres, smaller sediment basins and/or sediment traps should be used. At a minimum, silt fences, vegetative buffer strips, or equivalent sediment controls are required for all downslope boundaries of the construction area unless a sediment basin providing storage for a calculated volume of runoff from a 2-year, 24-hour storm or 3,600 ft3 of storage per acre drained is provided 

(EPA 2007). 

Not directly applicable. Therstandards for permitted supactivities related to a construsite (cement and concrete fahot mix asphalt/asphaltic cofacilities, stockpiles of sand gravel, and non-process arestormwater from cement, coand asphalt facilities). They monthly monitoring requiremdischarge limitations for flow (parameters - TSS, TOC, OGrease, and allowable rang(EPA 2007). 

Maine 3,600 (2004 TDD Section 7) No sizing criteria in permit (EPA 2007). 

The 2004 TDD Section 7 notes sediment basin drainage requirements for drainage areas > 10 acres. The EPA 2007 literature 

states in the 2003 Erosion and Sediment Control BMPs Manual that the capacity of the sediment basin shall be equal to the stormwater volume to be detained plus the volume of sediment expected to be trapped. Periodic removal of sediment will be necessary to maintain basin’s capacity. Temporary basins having drainage areas of 5 acres or less and a total embankment height of 5 feet or less may be designed with less conservative criteria. Any excavated pond with a drainage area in excess of 5 acres, or spring flow in excess of 100 gallons per minute must be designed in accordance with embankment pond criteria. Excavated ponds must be designed to be drained within a 10-day period. 

None (EPA 2007). The 2002 Appendix A states: 40 to 80 TSS reduction. PG could no2002 TDD Appendix A, and no numeric standard. 

Maryland 3,600 (EPA 2007) N/A EPA 2007 (minimum of 3,600 ft3/acre). 

PG estimated no numeric stNone (EPA 2007). The 2002 Appendix A states an 80 peTSS reduction based on the annual TSS loading from all events less than or equal to year/24-hour storm; howevecould not confirm for active construction sites. 
A-8 

State requirements—SUMMARY 

State 

Sediment basin storage volume 

(ft3/acre drained) Sediment basin (design parameters) Sediment basin—notes/references Numeric standard 

Massachusetts 

3,600 (2004 TDD Section 7) 

Basin size based on the runoff volume of a 2-year, 24-hour storm event (2002 TDD Appendix A). 

The 2004 TDD Section 7 notes sediment basin drainage requirements for drainage areas > 10 acres. In the EPA 2007 literature, 

it is noted that EPA issues permit. 

PG estimated no numeric stNone (EPA 2007). The 2002 Appendix A notes an 80 perreduction; however, PG couconfirm for active constructi

Michigan 

3,600 (2004 TDD Section 7; 2002 TDD Appendix A) 

N/A 

The 2002 TDD Appendix A notes sites > 10 acres require an on-site temporary sediment basin. The 2004 TDD Section 7 also notes sediment basin drainage requirements for drainage areas > 10 acres. The EPA 2007 

literature notes that the 1998 Guidebook for Best Management Practices for Michigan Watersheds provides sediment basin design recommendations (see longer write-up for details) (EPA 2007). The 1998 Guidebook for Best Management Practices for Michigan Watersheds provides sediment basin design recommendations. A straightforward method requires a storage volume that is equal to 1/2 inch of runoff from the contributing watershed. (For residential areas, 1/2 inch of runoff would be about a 1-year rainfall event in Michigan). For the high percentage of particulate pollutant removal, the detention basin should be designed so that it will take at least 24 hours to drain the entire volume stored. (For more information, see chapter 3 of the guidebook). 

None (EPA 2007). 

Minnesota 

3,600 (EPA 2007; 2004 TDD Section 7) 

For 10 or more disturbed acres; (1) The basins must provide storage below the outlet pipe for a calculated volume of runoff from a 2-year, 24-hour storm from each acre drained to the basin, except that in no case shall the basin provide less than 1,800 ft3 of storage below the 

outlet pipe from each acre drained to the basin, (2) Where no such calculation has been performed, a temporary (or permanent) sediment basin providing 3,600 ft3 of storage below the outlet pipe 

per acre drained to the basin shall be provided where attainable until final stabilization of the site (EPA 2007). 

The 2004 TDD Section 7 also noted sediment basin drainage requirements for drainage areas > 10 acres. 

None; however, where an alternative, innovative treatmsystem is proposed and demonstrated by calculationor other independent methoachieve 80 percent TSS remyear monitoring plan to samfrom the proposed method msubmitted (EPA 2007). 
A-9 

State requirements—SUMMARY 

State 

Sediment basin storage volume 

(ft3/acre drained) Sediment basin (design parameters) Sediment basin—notes/references Numeric standard 

Mississippi 

3,600 (EPA 2007; 2004 TDD Section 7) 

The Planning and Design Manual states that the maximum allowable drainage area into the basin shall be 25 acres. The design capacity of the basin must be at least 67 yd3/acre (1809 ft3/acre). The 

capacity of the basin may be estimated by 40% x Height x Surface Area. The basin spillway shall be designed to handle peak flow from a 10-year, 24-hour storm event. If a principal spillway is used in conjunction with an emergency spillway, the principal spillway shall have a minimum capacity of 0.2 cfs per acre of drainage area when the water surface is at the crest of the emergency spillway. The embankment of the sediment basin shall be temporarily seeded within 15 days after its completion. The basin should be designed according the following data sheet (see more detailed summaries in the manual) (EPA 2007). 

The 2004 TDD Section 7 notes sediment basin drainage requirements for drainage areas > 10 acres. 

None (EPA 2007). 

Missouri 3,600 (EPA 2007) 

The 2007 permit states that basins are needed for 10 acres or more, with a basin sizing at least 3,600 ft3/acre. In valuable 

water resource areas, the sediment basin needs to contain 1/2 inch of sediment from the drainage and withstand the 2-year, 24-hour storm (EPA 2007). PG noted that the 2007 permit 2-year, 24-hour storm event was not a statewide requirement (applies to valuable water resource areas). 

The 2004 TDD Section 7 notes a sediment basin storage volume of 1,800 ft3/acre 

drained. The EPA 2007 literature notes that in the 1995 Erosion and Sediment Manual the contributing area is recommended to be 20 acres or less and sized to store a minimum of 1,800 ft3 per disturbed acre with a detention of 

at least 24 hours. The site should be vegetated and stabilized immediately after construction. 

The 2002 TDD Appendix A that settleable solids less thml/L per hour for normal landisturbance, and 0.5 ml/L pefor land disturbance within sareas. The EPA 2007 literatthat per the Missouri State OPermit General Permit MO-3/8/2002: Construction site discharges shall not violate Code of State Regulations GWater Quality Standards 10 7.031(3) or exceed a maximsettleable solids concentratiml/L per hour for each stormoutfall. If the disturbed area Valuable Resources Water solids may not exceed 0.5 mhour. 
A-10 

State requirements—SUMMARY 

State 

Sediment basin storage volume 

(ft3/acre drained) Sediment basin (design parameters) Sediment basin—notes/references Numeric standard 

Montana 1,800 (2004 TDD Section 7) 

No sizing criteria in permit (EPA 2007). The 2004 TDD Section 7 states that for a state program that did not note a sediment basin size, EPA assumed based on BPJ that the baseline size was 1,800 ft3/acre. The 2002 TDD Appendix A notes 

a basin size based on the runoff volume of a 2-year, 24-hour storm event. PG could not verify the 2-year, 24-hour storm event. 

In the EPA literature, it notes in the Erosion and Sediment Control Manual stating that desilting basins are appropriate for areas of disturbed soil between 5 acres and 10 acres in size. Desilting basins shall be designed to have a capacity equivalent to 100 m3 (1500 

ft3) of storage (as measured from the top of 

the basin to the principal outlet,) per hectare (acre) of contributory area. This design is less than that required to capture 0.01 mm (0.0004 in) particle size, but larger than that required to capture particles 0.02 mm (0.0008 in) or larger. The depth must be no less than 1 m (3 ft) nor greater than 1.5 m (5 ft). Basins shall be designed to drain within 72 hours following storm events. 

The EPA 2007 literature notBMPs must minimize or pre“significant sediment” (as dePart VI of the General Permfrom leaving the constructioSignificant sediment means sediment, solids, or other wdischarged from constructioa facility or activity regulated the General Permit which ex1.0 cubic foot in volume in aof 100 square feet that may state surface water or a drathat leads directly to state suwater. 

Nebraska 1,800 (2004 TDD Section 7) 

No sizing criteria in permit (EPA 2007). The EPA 2007 literature also noted that sediment basins required for 5 acres or more in size. Where slopes are equal to or steeper than 3:1, sediment basins may be required for smaller drainage areas. The 2004 TDD Section 7 states that for a state program that did not note a sediment basin size, EPA assumed based on BPJ that the baseline size was 1,800 ft3/acre. 

 None (EPA 2007). 

Nevada 

3,600 (EPA 2007; 2004 TDD Section 7) 

The EPA 2007 literature notes in the 2002 permit states that basin requirements for drainage areas > 10 acres shall provided storage of 3,600 ft3/acre or for a 2-year, 24-hour storm event for each disturbed acre. For a drainage location that serves 10 or more acres disturbed at one time and where a temporary sediment basin or equivalent controls is not attainable, smaller sediment basins and/or sediment traps should be used. 

The 2004 TDD Section 7 notes sediment basin drainage requirements for drainage areas > 10 acres. The EPA 2007 literature 

notes to see design specifications from the Department of Conservation and Natural Resources (DCNR) and 1994 BMP manual. 

None (EPA 2007). 
A-11 

State requirements—SUMMARY 

State 

Sediment basin storage volume 

(ft3/acre drained) Sediment basin (design parameters) Sediment basin—notes/references Numeric standard 

New Hampshire 

3,600 (EPA 2007; 2004 TDD Section 7) 

The EPA 2007 literature references the CGP which specifies 3,600 ft3/acre or 2-

year, 24-hour runoff event. 

The 2004 TDD Section 7 notes sediment basin drainage requirements for drainage areas > 10 acres. The EPA 2007 literature 

notes that EPA’s CGP applies, and to see the design specifications from the 1992 Erosion and Sediment Control Handbook. 

PG estimated no numeric stThe standard referenced is relevant to stormwater, only excavation dewatering. The 2007 literature states, must uncontaminated excavation dewatering discharges to reTSS and turbidity. TSS musmonthly average and maximTSS limitations of 50 mg/L amg/L, respectively. 

New Jersey 1,800 (2004 TDD Section 7) 

The 2004 TDD Section 7 states that for a state program that did not note a sediment basin size, EPA assumed based on BPJ that the baseline size was 1,800 ft3/acre. 

New Jersey Erosion and Sediment Control and Stormwater Management Requirements state that Sediment Control Tanks shall be sized accordingly: 1 ft3 of storage for each 

gallon per minute of pump discharge capacity. Tanks may be connected in series to increase effectiveness (EPA 2007). 

None, standards are for posconstruction (EPA 2007). 

New Mexico 

3,600 (EPA 2007; 2004 TDD Section 7) 

EPA Region 6 issues permit—the 2003 general permit states that for 10 or more disturbed acres at one time, a temporary (or permanent) sediment basin providing at least 3,600 ft3/acre drained shall be 

provided until final stabilization of the site. For drainage locations which serve 10 or more disturbed acres at one time and where a temporary sediment basin or equivalent controls is not attainable, smaller sediment basins and/or sediment traps should be used. For drainage locations serving less than 10 acres, smaller sediment basins and/or sediment traps should be used. At a minimum, silt fences, vegetative buffer strips, or equivalent sediment controls are required for all down slope boundaries (and for those side slope boundaries deemed appropriate as dictated by individual site conditions) of the construction area unless a sediment basin providing storage for a calculated volume of runoff from a 2-year, 24-hour storm or 3,600 ft3 of storage per 

acre drained is provided. 

The 2004 TDD Section 7 notes sediment basin drainage requirements for drainage areas > 10 acres. The EPA 2007 literature 

notes that EPA Region 6 issues permit. 

None (EPA 2007). 
A-12 

State requirements—SUMMARY 

State 

Sediment basin storage volume 

(ft3/acre drained) Sediment basin (design parameters) Sediment basin—notes/references Numeric standard 

New York 

3,600 (2004 TDD Section 7). For alternate size standards, see New York’s Standards and Specifications for Erosion and Sediment Control (August 2005). 

The New York August 2005 Standards and Specification for Sediment and Erosion Control states that the minimum sediment storage volume of the basin, as measured from the bottom of the basin to the elevation of the crest of the principal spillway shall be at least 3,600 ft3/acre 

draining to the basin. This 3,600 ft3 is 

equivalent to one inch of sediment per acre of drainage area. The entire drainage area is used for this computation, rather than the disturbed area above, to maximize trapping efficiency. The length to width ratio shall be greater than 2:1, where length is the distance between the inlet and outlet. A wedge shape shall be used with the inlet at the narrow end. 

The 2004 TDD Section 7 notes sediment basin drainage requirements for drainage areas > 10 acres. The EPA 2007 literature 

notes to see details in New York’s Standards and Specifications for Erosion and Sediment Control (August 2005). 

None (EPA 2007). 

North Carolina 

1,800 (EPA 2007; 2004 TDD Section 7) 

The 2006 Erosion and Sediment Control Planning and Design Manual states that the sediment storage volume of the basin, as measured to the elevation of the crest of the principal spillway, is at least 1,800 ft3/acre for the disturbed area draining into 

the basin (1,800 ft3 is equivalent to a 1/2 inch of sediment per acre of basin drainage area) for a maximum of 100 acres. See more details on basin design provided in manual (EPA 2007). 

The EPA 2007 literature notes a sediment basin storage volume of 1,800 ft3/acre 

drained. 

None. None listed in EPA 202002 TDD Appendix A. 

North Dakota 3,600 (EPA 2007) 

The 2004 permit states that (for 10 or more acres) the basins shall be sized to provide 3,600 ft3 of storage below the 

outlet pipe per acre drained to the basin. Alterative designs may be used which provide storage below the outlet for a calculated volume of runoff from a 2-year, 24-hour storm and provides not less than 1,800 ft3 of storage below the outlet pipe 

from each acre drained to the basin. (EPA 2007). 

The 2004 TDD Section 7 notes a sediment basin storage volume of 1,800 ft3/acre 

drained. 

None (EPA 2007). 

Ohio 

1,800 (EPA 2007; 2004 TDD Section 7) 

N/A 

The 2006 Rainwater and Land Development Manual states that for areas less than 100 acres, the volume of the dewatering zone shall be a minimum of 1,800 ft3/acre of 

drainage (66.7 yd3/acre) (EPA 2007). 

None (EPA 2007). 
A-13 

State requirements—SUMMARY 

State 

Sediment basin storage volume 

(ft3/acre drained) Sediment basin (design parameters) Sediment basin—notes/references Numeric standard 

Oklahoma 

3,600 (EPA 2007; 2004 TDD Section 7) 

The EPA 2007 literature notes that the 2002 general permit states that for 10 or more acres drained the basin shall provide storage for a 2-year, 24-hour storm event or 3,600 ft3 of storage per 

acre. The 2002 TDD Appendix A notes 3,600 ft3/acre. 

The 2004 TDD Section 7 notes sediment basin drainage requirements for drainage areas > 10 acres. 

None (EPA 2007). 

Oregon 3,600 (EPA 2007) N/A 

Per the Oregon Erosion and Sediment Control Manual (April 2005), basin size shall be 3,600 ft3/acre and be designed by a professional engineer. The 2004 TDD Section 7 notes a sediment basin storage volume of 1,800 ft3/acre drained. 

If discharging to a 303(d) liswaterbody or a waterbody wTMDL for sediment and turbsampling for turbidity is requmeet a 160 NTU benchmarkunable to meet benchmark, Plan using a BMP such as wtreatment using electro-coagchemical flocculation or filtrabe implemented. (OR CGP) 

Pennsylvania 5,000 (EPA 2007) 

The EPA 2007 literature notes that the 2005 permit states that (1) A sediment storage zone of 1,000 ft3 per disturbed 

acre within the watershed of the basin is required; (2) A dewatering zone of 5,000 ft3 for each acre tributary to the basin is to 

be provided. Reductions in the dewatering zone are allowed unless the basins is in a HQ or EV watershed, however the minimum required dewatering zone is at least 3,600 ft3/acre. (3,600 to 6,000 

ft3/acre + 1,800 ft3/acre = 4,800 to 6,000 ft3/acre, assumed 5,000 ft3/acre). The 2002 TDD Appendix A notes a 5-year runoff event for water quality treatment. 

The 2004 TDD Section 7 notes sediment basin drainage requirements for drainage areas > 10 acres. The 2002 TDD Appendix A 

states that basins volumes should drain no quicker than 4 days and no longer than 7 days. 

None (EPA 2007). 

Rhode Island 1,800 (2004 TDD Section 7) 

The 2004 TDD Section 7 states that for a state program that did not note a sediment basin size, EPA assumed based on BPJ that the baseline size was 1,800 ft3/acre. The EPA 2007 literature notes no 

sizing criteria in permit. The 2002 TDD Appendix A notes a 10-year runoff event for water quality treatment. 

The Stormwater Design and Installation Standards Manual and the Soil Erosion and Sediment Control Handbook were not reviewed. 

PG estimated no numeric stNone (EPA 2007). The 2002 Appendix A notes 80 to 90 pTSS reduction; however, PG not confirm for active constrrunoff. 
A-14 

State requirements—SUMMARY 

State 

Sediment basin storage volume 

(ft3/acre drained) Sediment basin (design parameters) Sediment basin—notes/references Numeric standard 

South Carolina 

3,600 (EPA 2007; 2004 TDD Section 7) 

The EPA 2007 literature notes basin sizing requirements for 10 or more acres provide storage for a 10-year, 24-hour storm event or at least 3,600 ft3/acre. (10–

year, 24-hour Soil Conservation Service (SCS) Type II, or Type III (coastal zone) storm event). The 2002 TDD Appendix A notes 3,600 ft3/acre. 

The 2004 TDD Section 7 notes sediment basin drainage requirements for drainage areas > 10 acres. 

PG estimated no numeric stThe EPA 2007 literature notpercent of TSS removal for areas > 5 acres. The 2002 TAppendix A notes 80 percenreduction; however, PG couconfirm for active constructi

South Dakota 

3,600 (EPA 2007; 2004 TDD Section 7) 

The 2002 TDD Appendix A notes a 5-year runoff event for water quality treatment. (PG could not find reference for this). 

The 2004 TDD Section 7 notes sediment basin drainage requirements for drainage areas > 10 acres. 

None (EPA 2007). 

Tennessee 

3,600 (EPA 2007; 2004 TDD Section 7) 

The EPA 2007 literature notes that the 2005 permit states to design for a 2-year, 24-hour storm for 10 or more acres. Also, the 2002 Erosion and Sediment Control Handbook states that the total storage volume of the basin at the spillway should be at least 134 cubic yards (3,618 ft3) per 

acre of drainage area. The volume of the permanent pool must be at least 67 cubic yards (1,809 ft3) per acre of drainage area 

and the volume of dry storage must be at least an additional 67 cubic yards (1,809 ft3) per acre of drainage area. The 

emergency spillway should be able to handle a 2-year or 5-year, 24-hour storm event. The outlets for the basin should pass the peak runoff expected from the contributing drainage area for a 25-year, 24-hour storm. 

The 2004 TDD Section 7 notes sediment basin drainage requirements for drainage areas > 10 acres. 

None (EPA 2007). 
A-15 

State requirements—SUMMARY 

State 

Sediment basin storage volume 

(ft3/acre drained) Sediment basin (design parameters) Sediment basin—notes/references Numeric standard 

Texas 

3,600 (EPA 2007; 2004 TDD Section 7) 

The EPA 2007 literature notes that the 2003 Permit states that sediment basins are required where feasible for common drainage locations that serve an area with 10 or more acres disturbed at one time. The temporary (or permanent) sediment basin should provide storage for a calculated volume of runoff from a 2-year, 24-hour storm from each disturbed acre drained. Where rainfall data is not available or a calculation cannot be performed, a sediment basin providing 3,600 ft3 of storage per acre drained is 

required where attainable until final stabilization of the site. The 2002 TDD Appendix A notes 3,600 ft3/acre. 

The 2004 TDD Section 7 notes sediment basin drainage requirements for drainage areas > 10 acres. 

None, except for concrete bplants (EPA 2007) 

Utah 

3,600 (EPA 2007; 2004 TDD Section 7) 

The EPA 2007 literature notes that the 2002 permit says for 10 or more acres basin storage shall provide for a 10-year, 24-hour storm event, or 3,600 ft3/acre. 

Permit No.: UTRI00000 (10/31/200) states “...sediment basin that provides storage for a 10-year, 24-hour storm event, a calculated volume of runoff for disturbed acres drained, or equivalent control measures, until final stabilization of the site. Where calculations are not performed, a sediment basin providing 3,600 ft3 of storage per acre drained (a 1 

inch storm event)” 

The 2004 TDD Section 7 notes sediment basin drainage requirements for drainage areas > 10 acres. 

None (EPA 2007). 

Vermont 1,800 (2004 TDD Section 7) 

The EPA 2007 literature notes basin sizing of 3,600 ft3/acre for moderate risk 

only, and no sizing criteria in permit. The 2004 TDD Section 7 states that for a state program that did not note a sediment basin size, EPA assumed based on BPJ that the baseline size was 1,800 ft3/acre. 

EPA 2007 literature found no sizing criteria and found 3,600 ft3/acre for moderate risk 

only; therefore, assumed 1,800 per BPJ from 2004 TDD Section 7. 

Vermont’s CGP issued Febr2008 contains a numeric acof 25 NTU for moderate-risk 
A-16 

State requirements—SUMMARY 

State 

Sediment basin storage volume 

(ft3/acre drained) Sediment basin (design parameters) Sediment basin—notes/references Numeric standard 

Virginia 

3,600 (EPA 2007; 2004 TDD Section 7) 

The EPA 2007 literature notes that the Virginia Erosion and Sediment Control regulations state that sediment traps and sediment basins shall be designed and constructed based on the total drainage area to be served by the trap or basin. Surface runoff from disturbed areas that is comprised of flow from drainage areas greater than or equal to three acres shall be controlled by a sediment basin. The minimum storage capacity of a sediment basin shall be 134 cubic yards per acre (3,618 ft3) of drainage area. The outfall 

system shall, at a minimum, maintain the structural integrity of the basin during a 25-year, 24-hour duration storm event. Runoff coefficients used in runoff calculations shall correspond to a bare earth condition or those conditions expected to exist while the sediment basin is used. The 2002 TDD Appendix A notes that sediment basins required for sites of 10 acres or more (except those with final stabilization); for sites less than 10 acres, same units required but only for sideslope and downslope boundaries of construction sites. 

The 2004 TDD Section 7 notes sediment basin drainage requirements for drainage areas > 10 acres. 

None (EPA 2007) 

Washington 

3,600 (eastern WA only). For alternate size standards, see WA BMP C241. 

The 2002 TDD Appendix A notes a 24-hour/6-month storm for water quality treatment. 2-year (or 10-year peak if warranted) OR Rational Method See Eastern Washington BMP C241 (http://www.ecy.wa.gov/pubs/0410076/7.pdf). Western Washington has the same storm events but does not specifically mention 3,600 ft3/acre. 

The EPA 2007 literature notes basin requirements are different for western and eastern parts of State—see manuals. The 2004 TDD Section 7 notes a sediment basin storage volume of 1,800 ft3/acre drained. 

Statewide standard varies wbackground. PG noted that t173-201A-030 has been repthe WAC 173-201A-200 Fresdesignated uses and criteria 2006). Table 200 (1) (e) contupdated aquatic life turbidity The EPA 2007 literature statthe Water Quality Standards Surface Waters of the State Washington WAC 173-201A(vi) states that turbidity shall exceed 5 NTU over backgroturbidity when the backgrounturbidity is 50 NTU or less, o

more than a 10 percent increturbidity when the backgrounturbidity is more than 50 NTU
A-17 

State requirements—SUMMARY 

State 

Sediment basin storage volume 

(ft3/acre drained) Sediment basin (design parameters) Sediment basin—notes/references Numeric standard 

Washington, Small Parcel 

The 2002 TDD Appendix A notes a 24-hour/6-month storm for water quality treatment. 

West Virginia 

3,600 (EPA 2007; 2004 TDD Section 7) 

The EPA 2007 literature notes that the 2002 permit states sediment basins and traps will be installed with 3,600 ft3 of 

storage, measured from the bottom elevation of the structure to the top of the riser or weir, per acre of drainage and will have draw down times of 48 to 72 hours. The 2002 TDD Appendix A notes runoff from a 2-year storm required for water quality treatment (PG could not confirm with state literature). 

The 2004 TDD Section 7 notes sediment basin drainage requirements for drainage areas > 10 acres. 

None (EPA 2007). 

Wisconsin 

1,800 (2004 TDD Section 7). For alternate size standards, see WI DNR Conservation Practice Standard 1064. 

The EPA 2007 literature notes in the Technical Standards document that basins shall be used for greater than 5 to 100 acres. The sizing criteria for determining treatment surface area of a sediment basin are based on the soil texture and peak outflow during the 1-year, 24-hour design storm. The overflow spillway should be designed to carry the peak rate of runoff expected from a 10-year, 24-hour design storm. The 2004 TDD Section 7 states that for a state program that did not note a sediment basin size, EPA assumed based on BPJ that the baseline size was 1,800 ft3/acre. 

The EPA 2007 literature notthe current standard in Wisc(NR 151.11 pg 409) requireconstruction sites to implemerosion and sediment controreduce to the maximum extepracticable 80 percent of the sediment load carried in runannual basis, compared to a baseline of no sediment or econtrols. 
A-18 

State requirements—SUMMARY 

State 

Sediment basin storage volume 

(ft3/acre drained) Sediment basin (design parameters) Sediment basin—notes/references Numeric standard 

Wyoming 1,800 (2004 TDD Section 7) 

The EPA 2007 literature notes No sizing criteria in the permit, and the 1999 Urban Best Management Practice (BMP) manual says use basins for 5 to 100 acres. The 2004 TDD Section 7 states that for a state program that did not note a sediment basin size, EPA assumed based on BPJ that the baseline size was 1,800 ft3/acre. 

1,800 ft3/acre based on 2004 TDD Section 7. 

Standard varies with backgrThe EPA 2007 literature notfor cold water fisheries and water supplies turbidity leveincreases must be less than NTUs; for warm water /nongfisheries turbidity level incremust be less than 15 NTUs. However, an exception shalthe North Platte River from GDam to the Nebraska line duannual “silt run” from GuernThe 2002 TDD Appendix A turbidity levels must be less to 15 NTUs. 

Puerto Rico District of Columbia 

3,600 (EPA 2007; 2004 TDD Section 7) 

Basin sizing for 2-year, 24-hour storm (EPA 2007). 

The 2004 TDD Section 7 notes sediment basin drainage requirements for drainage areas > 10 acres. 

None (EPA 2007) 
A-19 

State requirements: Environmental Protection Agency (EPA) 2007 

Soil stabilization 

State 

Sediment basin general 

requirements 

Sediment basins notes/other 

requirements Notes/other requirements Days Numeric standard 

Alabama Basin sizing of 1,800 ft3/acre. 8-hour detention time for sites greater than 5 acres. 13 No 

There the mthat dprovidstoragbe at predeminimerosio

Alaska 

Basin sizing of 1,800 ft3/acre plus 

1.5 ft for sediment accumulation—generally designed to remove medium silt (62 microns) particles. 

Construction General Permit (CGP) CGP No None 

Arizona Basin sizing of 3,600 ft3/acre or 2- year, 24-hour. 14 No None Arkansas Basin sizing of 3,600 ft3/acre or 10- year, 24-hour. 14 80 percent removal of TSS from flows exceeding predevelopment levels, where practicable. None California 

Several standards exist, including a basin sizing of 3,600 ft3/acre as well 

as a settling velocity approach 

 Not specified 

California’s draft CGP includes turbidity effluent levels of 1,000 NTU. If Active Treatment Systems are used, the daily flow-weighted average is 10 NTU and the maximum for any single sample is 20 NTU. 

85 pefrom scateginfiltraStandMitiga

Colorado 

Colorado Department of Transportation (CDOT) specifies 3,600 ft3/acre sediment basin sizing. 

Colorado requires preparation of a stormwater pollution prevention plan (SWPPP) but does not specify specific sizing for BMPs. No statewide erosion and sediment control manual exists. Extensive requirements exist at the local level. Specifically, Douglas County requires that disturbed areas be drill 

seeded, crimped and mulched, or permanently landscaped within 30 days from the start of land disturbance activities or within 7 days of the substantial completion of grading and topsoiling operations, whichever duration is shorter. 

Douglas County requires that disturbed areas be drill seeded and crimp mulched, or permanently landscaped, within 30 days from the start of land disturbance activities or within 7 days of the substantial completion of grading and topsoiling operations, whichever duration is shorter. 

see notes No None 
A-20 

State requirements: Environmental Protection Agency (EPA) 2007 

Soil stabilization 

State 

Sediment basin general 

requirements 

Sediment basins notes/other 

requirements Notes/other requirements Days Numeric standard 

Connecticut Basin sizing of 3,600 ft3/acre. Required for sites greater than 2 acres. 

Where construction activities have permanently ceased or have temporarily been suspended for more than 7 days, or when final grades are reached in any portion of the site, stabilization practices shall be implemented within three days. Areas that will remain disturbed but inactive for at least 30 days shall receive temporary seeding. Areas that will remain disturbed beyond the planting season, shall receive long-term, nonvegetative stabilization sufficient to protect the site through the winter. 

3 

80% TSS [A goal of 80 percent removal of TSS - 2004 Connecticut Stormwater Quality Manual, Chapter 6.] 

[Requinch, wpercerunoff

Delaware Basin sizing of 3,600 ft3/acre. 14 No 

[Recovolumrainfarunoffperceload, constr

Florida Basin sizing of 3,600 ft3/acre. 7 No 

Requiregionthat 0runoff treatm

Florida, DEP, Northern District (only applies in NW Florida) Florida, South Florida Water Management District (General, Standard General, Noticed General and Individual Permits) 
A-21 

State requirements: Environmental Protection Agency (EPA) 2007 

Soil stabilization 

State 

Sediment basin general 

requirements 

Sediment basins notes/other 

requirements Notes/other requirements Days Numeric standard 

Florida, Southwest Florida Water Management District Florida, St. Johns River Water Management District Florida, Suwannee River Water Management District Georgia Basin sizing of 1,800 ft3/acre. 14 

 Receiving water turbidity standard—cannot increase turbidity by more than 25 NTU in warm waters and 10 NTU in cold water trout streams. Allowable turbidity in effluent varies based on site size and receiving stream drainage area. 

Requipercewhich storm 

Hawaii 

Basin sizing of 3,600 ft3/acre or 2-

year, 24-hour for drainage areas >

10 or more acres. 

 30 

ReducTSS lbased annuaall stoto the stormdeveloTSS sannuagreatepredeTo the maintpeak averathat aprededesign develorate ashould year/2
A-22 

State requirements: Environmental Protection Agency (EPA) 2007 

Soil stabilization 

State 

Sediment basin general 

requirements 

Sediment basins notes/other 

requirements Notes/other requirements Days Numeric standard 

Idaho 

Basin sizing of 3,600 ft3/acre or 2-

year, 24-hour for drainage areas >

10 or more acres. 

 14 
A-23 

State requirements: Environmental Protection Agency (EPA) 2007 

Soil stabilization 

State 

Sediment basin general 

requirements 

Sediment basins notes/other 

requirements Notes/other requirements Days Numeric standard 

Illinois No sizing criteria in permit. 

The 2002 Illinois Urban Manual states that the basin requirements shall be based on a 2-year, 24-hour storm or 134 cubic yards/acre (i.e., 3,600 ft3/acre)—

whichever is greater. 

Stabilization within 14 days (unless covered with snow or construction will resume within 21 days). 

14 No 

Indiana No sizing criteria in permit. Exist for some areas in the state. 15 

Not applicable. Only in certain parts of Indiana (e.g., 80 percent of TSS removal in Marion County) (EPA 2007). 

Iowa 

Basin sizing of 3,600 ft3/acre. The 

2002 permit states that a sediment basin shall be installed for drainage area more than 10 acres disturbed. (Flows from upland areas that are undisturbed may be diverted around the basin). 

The 2006 Iowa Construction Site Erosion Control Manual states that the size of the sediment basin, is as measured from the bottom of the basin to the principal spillway and should provide at least 3,600 ft3 of storage per acre of drainage. This 

provides storage equal to 1 inch of runoff per acre. Likewise, 1,800 ft3 amounts to 

1/2 inch of sediment storage per acre. The basin should be cleaned when the volume of sediment reaches 900 ft3/acre. 

At this time, the cleanout shall be performed to restore the original design capacity of the basin. At no time should the sediment level be permitted to build higher than 1 ft below the principal outlet. 

Stabilization within 14 days (unless covered with snow or construction will resume within 21 days). 

14 No 

Kansas 

The 2007 permit requires a storage capacity of 3,600 ft3/acre and the 

Sediment Basin Design Criteria in the permit states, “rational method or other equivalent runoff calculations based on storage of a 2.6-inch rainfall event with a minimum runoff coefficient of 0.77 for disturbed acreage and appropriate runoff coefficients for undisturbed acreage must be provided to determine the revised storage volume requirement.” 

The field guide for Missouri and Kansas says that for drainage areas of 20 acres or less, the sediment storage shall be 1,800 ft3/acre with a detention time of at 

least 24 hours. 

None specified; state that “time should be minimized.” N/A No 

Kentucky 

The 2002 permit requires a basin sizing of 3,600 ft3/acre for drainage 

locations >10 acres. 

The 2007 Draft Kentucky BMP Manual requires basin sizing of 3,600 ft3/acre, not 

to exceed 10 acre-feet for areas 5 to 120 acres. The goal is to reduce TSS by 80 percent for the 10-year, 24-hour storm, or provide a detention time of 24 to 48 hours for the 10-year, 24-hour storm. 

Stabilization within 14 days (unless covered with snow or construction will resume within 21 days). 

14 

80% TSS (EPA 2007). A goal of 80 percent removal of TSS from flows that exceed predevelopment levels (2002 General KPDES Permit for Stormwater Point Source Discharges, Construction Activity, page IV-2) 
A-24 

State requirements: Environmental Protection Agency (EPA) 2007 

Soil stabilization 

State 

Sediment basin general 

requirements 

Sediment basins notes/other 

requirements Notes/other requirements Days Numeric standard 

Louisiana 

For 10 or more disturbed acres either the smaller of 3,600 ft3/acre or a 2-

year, 24-hour storm. This does not apply to flows from off-site areas and flows from on-site areas that are either undisturbed of have undergone final stabilization where such flows are diverted around the sediment basin. For drainage locations serving less than 10 acres, smaller sediment basins and/or sediment traps should be used. At a minimum, silt fences, vegetative buffer strips, or equivalent sediment controls are required for all downslope boundaries of the construction area unless a sediment basin providing storage for a calculated volume of runoff from a 2-year, 24-hour storm or 3,600 ft3 of 

storage per acre drained is provided. 

 14 

There are standards for permitted support activities related to a construction site (cement and concrete facilities, hot mix asphalt/asphaltic concrete facilities, stockpiles of sand and gravel, and non-process area stormwater from cement, concrete, and asphalt facilities). They establish monthly monitoring requirements and discharge limitations for flow (parameters: TSS, TOC, Oil & Grease, and allowable ranges of pH). 

Maine No sizing criteria in permit. 

The 2003 Erosion and Sediment Control BMPs Manual states that the capacity of the sediment basin shall be equal to the stormwater volume to be detained plus the volume of sediment expected to be trapped. Periodic removal of sediment will be necessary to maintain basin’s capacity. Temporary basins having drainage areas of 5 acres or less and a total embankment height of 5 feet or less may be designed with less conservative criteria. Any excavated pond with a drainage area in excess of 5 acres, or spring flow in excess of 100 gallons per minute must be designed in accordance with embankment pond criteria. Excavated ponds must be designed to be drained within a 10-day period. 

Operators must stabilize with mulch, or other non-erodible cover, any exposed soils that will not be worked for more than 7 days. They must stabilize areas within 75 feet of a wetland or waterbody within 48 hours of the initial disturbance of the soil or before any storm event, whichever comes first. They are also required to remove any temporary control measures, such as silt fences, within 30 days after permanent stabilization is attained. 

14 No 
A-25 

State requirements: Environmental Protection Agency (EPA) 2007 

Soil stabilization 

State 

Sediment basin general 

requirements 

Sediment basins notes/other 

requirements Notes/other requirements Days Numeric standard 

Maryland 

The 1994 Erosion and Sediment Control requirements states that the minimum storage volume for sediment basins is 3,600 ft3/acre of contributing drainage 

area, equally divided between wet storage and dry storage. The specified drawdown time from the crest of the basin to the permanent pool level is 10 hours (minimum). The state standards do not specify minimum site sizes where sediment basins are required, but it is assumed based on the sediment trap applicability criteria that sediment basins are required for contributing drainage areas of 10 or more acres. 

Stabilization is 14 days (7 days for steep slopes). 14 No 

Massachusetts EPA issues permit. 

The 2003 Erosion and Sediment Control guidelines says the drainage area for the sediment basin should be no more than 100 acres with a life span of 3 years unless it is designed as a permanent structure. The sediment basin should have a minimum volume based on 1⁄2 

inch of storage for each acre of drainage area. This volume equates to 1,800 ft3 of 

storage or 67 cubic yards for each acre of drainage area. The sediment basin should have a total spill way capacity for a 10-year peak flow with a 1-foot freeboard. Freeboard is the difference between the design flow elevation in the emergency spillway and the top elevation of the embankment. 

CGP reference. 14 No 
A-26 

State requirements: Environmental Protection Agency (EPA) 2007 

Soil stabilization 

State 

Sediment basin general 

requirements 

Sediment basins notes/other 

requirements Notes/other requirements Days Numeric standard 

Michigan 

1998 Guidebook for Best Management Practices for Michigan Watersheds provides sediment basin design recommendations (see longer write-up for details). The 1998 Guidebook for Best Management Practices for Michigan Watersheds provides sediment basin design recommendations. A straightforward method requires a storage volume that is equal to one-half inch of runoff from the contributing watershed. (For residential areas, 1/2 inch of runoff would be about a 1-year rainfall event in Michigan). For the high percentage of particulate pollutant removal, the detention basin should be designed so that it will take at least 24 hours to drain the entire volume stored. (For more information, see chapter 3 of the guidebook.) 

Stabilization within 15 calendar days after final grading or the final earth change has been completed. 

15 No 

Minnesota 

For 10 or more disturbed acres; (1) The basins must provide storage below the outlet pipe for a calculated volume of runoff from a 2-year, 24-hour storm from each acre drained to the basin, except that in no case shall the basin provide less than 1,800 ft3 of storage below the 

outlet pipe from each acre drained to the basin, (2) Where no such calculation has been performed, a temporary (or permanent) sediment basin providing 3,600 ft3 of storage 

below the outlet pipe per acre drained to the basin shall be provided where attainable until final stabilization of the site. 

Steeper than 3:1, 7 days, 10:1 to 3:1, 14 days, flatter than 10:1, 21 days 

7, 14 or 21 (see notes) 

No - Where an alternative, innovative treatment system is proposed and demonstrated by calculation, design or other independent methods to achieve 80 percent TSS removal a 2-year monitoring plan to sample runoff from the proposed method must be submitted. 
A-27 

State requirements: Environmental Protection Agency (EPA) 2007 

Soil stabilization 

State 

Sediment basin general 

requirements 

Sediment basins notes/other 

requirements Notes/other requirements Days Numeric standard 

Mississippi 

The 2005 general permit states that for 10 or more acres disturbed at one time, a temporary (or permanent) sediment basin providing at least 3,600 ft3/acre 

drained shall be provided until final stabilization of the site. 

The Planning and Design Manual states that the maximum allowable drainage area into the basin shall be 25 acres. The design capacity of the basin must be at least 67 yd3/acre (1809 ft3/acre). The 

capacity of the basin may be estimated by 40% x Height x Surface Area. The basin spillway shall be designed to handle peak flow from a 10-year, 24-hour storm event. If a principal spillway is used in conjunction with an emergency spillway, the principal spillway shall have a minimum capacity of 0.2 cfs per acre of drainage area when the water surface is at the crest of the emergency spillway. The embankment of the sediment basin shall be temporarily seeded within 15 days after its completion. The basin should be designed according the following data sheet (see more detailed summaries in the manual). 

Within 7 calendar days when a disturbed area will be left undisturbed for 30 days or more. 

7 No 

Missouri 

The 2007 permit states that basins are needed for 10 acres or more, with a basin sizing at least 3,600 ft3/acre. In valuable water resource 

areas the sediment basin needs to contain 1/2 inch of sediment from the drainage and withstand the 2-year, 24-hour storm. The basin spillway or embankment requires stabilization to minimize potential for erosion. 

The 1995 Erosion and Sediment Manual says the contributing area is recommended to be 20 acres or less and sized to store a minimum of 1,800 ft3 per 

disturbed acre with a detention of at least 24 hours. The site should be vegetated and stabilized immediately after construction. 

Stabilization at 14 days; however if the slope of the area is greater than 3:1 (3 feet horizontal to 1 foot vertical) or if the slope is greater than 3 percent and greater than 150 feet in length, then interim stabilization within 7 days of ceasing operations on that part of the site is required. 

7 or 14 (see notes) 

Per the Missouri State Operating Permit General Permit MOR109000 3/8/2002: Construction site discharges shall not violate Missouri Code of State Regulations General Water Quality Standards 10 CSR 20 7.031(3) or exceed a maximum settleable solids concentration of 2.5 ml/L per hour for each stormwater outfall. If the disturbed area is near a Valuable Resources Water, settleable solids may not exceed 0.5 ml/L per hour. 
A-28 

State requirements: Environmental Protection Agency (EPA) 2007 

Soil stabilization 

State 

Sediment basin general 

requirements 

Sediment basins notes/other 

requirements Notes/other requirements Days Numeric standard 

Montana No sizing criteria in permit. 

The Erosion and Sediment Control Manual states that desilting basins are appropriate for areas of disturbed soil between 5 acres and 10 acres in size. Desilting basins shall be designed to have a capacity equivalent to 100 m3 (1500 ft3) 

of storage (as measured from the top of the basin to the principal outlet,) per hectare (acre) of contributory area. This design is less than that required to capture 0.01 mm (0.0004 in) particle size, but larger than that required to capture particles 0.02 mm (0.0008 in) or larger. The depth must be no less than 1 m (3 ft) nor greater than 1.5 m (5 ft). Basins shall be designed to drain within 72 hours following storm events. 

 N/A 

BMPs must minimize or prevent significant sediment (as defined in Part VI of the General Permit p. 28) from leaving the construction site. Significant sediment means sediment, solids, or other wastes discharged from construction site, or a facility or activity regulated under the General Permit that exceeds 1.0 cubic foot in volume in any area of 100 square feet that may enter state surface water or a drainage that leads directly to state surface water. 

Nebraska 

Sediment basins required for 5 acres or more in size. Where slopes are equal to or steeper than 3:1, sediment basins may be required for smaller drainage areas. 

None 

Temporary or permanent seeding shall be established as soon as possible after grading and clearing activities are completed, and during interim periods on areas that are not being actively worked. Whenever exposed soils are not to be graded for 30 days or more, temporary or permanent seeding needs to be initiated, unless other stabilization methods are used or such need can be justified as unnecessary because of mitigating conditions present at the site. 

30 (see notes) No 

Nevada 

The 2002 permit states that basin requirements for drainage areas >

10 acres shall provided storage of 3,600 ft3/acre or for a 2-year, 24-

hour storm event for each disturbed acre. For a drainage location which serves ten or more acres disturbed at one time and where a temporary sediment basin or equivalent controls is not attainable, smaller sediment basins and/or sediment traps should be used. 

See design specifications from the Department of Conservation and Natural Resources (DCNR) and 1994 BMP manual. 

14 No 
A-29 

State requirements: Environmental Protection Agency (EPA) 2007 

Soil stabilization 

State 

Sediment basin general 

requirements 

Sediment basins notes/other 

requirements Notes/other requirements Days Numeric standard 

New Hampshire EPA’s CGP applies. 

See the design specifications from the 1992 Erosion and Sediment Control Handbook. 

 14 

Yes, see monitoring. Must treat any uncontaminated excavation dewatering discharges to remove TSS and turbidity. Must sample at a location before mixing with stormwater at least once per week during weeks when discharges occur. TSS must meet monthly average and maximum daily TSS limitations of 50 mg/L and 100 mg/L, respectively. Records of any sampling and analysis must be maintained and kept with the SWPPP for at least 3 years after final site stabilization. Applicable only to certain size sites. 

New Jersey 

New Jersey Erosion and Sediment Control and Stormwater Management Requirements state that Sediment Control Tanks shall be sized accordingly: 1 cubic foot of storage for each gallon per minute of pump discharge capacity. Tanks may be connected in series to increase effectiveness. 

None N/A 

A major development project that creates at least 0.25 acres of new or additional impervious surface must include stormwater management measures that reduce the average annual TSS load in the development site’s post-construction runoff by 80 percent. In addition, these stormwater management measures must reduce the average annual nutrient load in the post-construction runoff by the maximum extent feasible. For various BMPs for more detailed TSS and nutrient removal rates, see Chapter 4 of the New Jersey Stormwater Best Management Practices Manual. 
A-30 

State requirements: Environmental Protection Agency (EPA) 2007 

Soil stabilization 

State 

Sediment basin general 

requirements 

Sediment basins notes/other 

requirements Notes/other requirements Days Numeric standard 

New Mexico 

EPA Region 6 issues permit—the 2003 general permit states that for 10 or more disturbed acres at one time, a temporary (or permanent) sediment basin providing at least 3,600 ft3/acre drained shall be 

provided until final stabilization of the site. For drainage locations which serve 10 or more disturbed acres at one time and where a temporary sediment basin or equivalent controls is not attainable, smaller sediment basins and/or sediment traps should be used. For drainage locations serving less than 10 acres, smaller sediment basins and/or sediment traps should be used. At a minimum, silt fences, vegetative buffer strips, or equivalent sediment controls are required for all down slope boundaries (and for those side slope boundaries deemed appropriate as dictated by individual site conditions) 

of the construction area unless a sediment basin providing storage for a calculated volume of runoff from a 2-year, 24-hour storm or 3,600 ft3 of 

storage per acre drained is provided. 

 14 No 

New York 

See details in New York’s Standards and Specifications for Erosion and Sediment Control (August 2005). 

 14 No 

North Carolina 

The 2006 Erosion and Sediment Control Planning and Design Manual states that the sediment storage volume of the basin, as measured to the elevation of the crest of the principal spillway, is at least 1,800 ft3/acre for the disturbed area draining into 

the basin (1,800 ft3 is equivalent to a 1/2 

inch of sediment per acre of basin drainage area) for a maximum of 100 acres. See more details on basin design provided in manual. 

 N/A 
A-31 

State requirements: Environmental Protection Agency (EPA) 2007 

Soil stabilization 

State 

Sediment basin general 

requirements 

Sediment basins notes/other 

requirements Notes/other requirements Days Numeric standard 

North Dakota 

The 2004 permit states that (for 10 or more acres) the basins shall be sized to provide 3,600 ft3 of storage 

below the outlet pipe per acre drained to the basin. Alterative designs may be used which provide storage below the outlet for a calculated volume of runoff from a 2-year, 24-hour storm and provides not less than 1,800 ft3 of storage 

below the outlet pipe from each acre drained to the basin. 

 None N/A No 

Ohio 

The 2003 permit states that a sediment settling pond shall be sized to provide at least 67 cubic yards of storage per acre or 1809 ft3/acre. 

The 2006 Rainwater and Land Development Manual states that for areas less than 100 acres, the volume of the dewatering zone shall be a minimum of 1,800 ft3/acre of drainage (66.7 yd3/acre). 

Stabilization in 7 days, or 2 days if near stream. 

2 or 7 (see notes) 

No 

Oklahoma 

The 2002 general permit states that for 10 or more acres drained the basin shall provide storage for a 2-year, 24-hour storm event or 3,600 ft3 of storage per acre. 

 14 No 

Oregon Basin sizing of 3,600 ft3/acre. 

Apply temporary or permanent soil stabilization measures immediately on all disturbed areas as grading progresses. 

1 (see notes) No 

Pennsylvania 

The 2005 permit states that (1) A sediment storage zone of 1,000 ft3

per disturbed acre within the watershed of the basin is required; (2) A dewatering zone of 5,000 ft3

for each acre tributary to the basin is to be provided. Reductions in the dewatering zone are allowed unless the basins is in a HQ or EV watershed, however the minimum required dewatering zone is at least 3,600 ft3/acre. 

 None N/A No 

Rhode Island No sizing criteria in permit. 

The Stormwater Design and Installation Standards Manual and the Soil Erosion and Sediment Control Handbook were not reviewed. 

14 No 
A-32 

State requirements: Environmental Protection Agency (EPA) 2007 

Soil stabilization 

State 

Sediment basin general 

requirements 

Sediment basins notes/other 

requirements Notes/other requirements Days Numeric standard 

South Carolina 

Basin sizing requirements for 10 or more acres provide storage for a 10-year, 24-hour storm event or at least 3,600 ft3/acre (10-year 24-hour Soil 

Conservation Service (SCS) Type II, or Type III (coastal zone) storm event). 

As soon as possible, but no later than 14 days. 14 80 percent of TSS removal for drainage areas > 5 acres. 

South Dakota Basin sizing of 3,600 ft3/acre. 14 No Tennessee 

The 2005 permit states to design for a 2-year, 24-hour storm for 10 or more acres. 

The 2002 Erosion and Sediment Control Handbook states that the total storage volume of the basin at the spillway should be at least 134 cubic yards (3,618 ft3) per 

acre of drainage area. The volume of the permanent pool must be at least 67 cubic yards (1,809 ft3) per acre of drainage area 

and the volume of dry storage must be at least an additional 67 cubic yards (1,809 ft3) per acre of drainage area. The 

emergency spillway should be able to handle a 2-year or 5-year, 24-hour storm event. The outlets for the basin should pass the peak runoff expected from the contributing drainage area for a 25-year, 24-hour storm. 

Preconstruction vegetative ground cover shall not be destroyed, removed or disturbed more than 10 days before grading or earth moving unless the area is seeded and/or mulched or other temporary cover is installed. Construction must be phased for projects in which more than 50 acres of soil will be disturbed. No more than 50 acres of active soil disturbance is allowed at any time during the construction project. 

15 No 

Texas 

The 2003 Permit states that sediment basins are required where feasible for common drainage locations that serve an area with 10 or more acres disturbed at one time. The temporary (or permanent) sediment basin should provide storage for a calculated volume of runoff from a 2-year, 24-hour storm from each disturbed acre drained. Where rainfall data is not available or a calculation cannot be performed, a sediment basin providing 3,600 ft3 of storage per 

acre drained is required where attainable until final stabilization of the site. 

 14 For Concrete Batch plants only. 

Utah 

The 2002 permit says for 10 or more acres basin storage shall provide for a 10-year, 24-hour storm event, or 3,600 ft3/acre. 

14 No 
A-33 

State requirements: Environmental Protection Agency (EPA) 2007 

Soil stabilization 

State 

Sediment basin general 

requirements 

Sediment basins notes/other 

requirements Notes/other requirements Days Numeric standard 

Vermont No sizing criteria in permit. Basin sizing of 3,600 ft3/acre for moderate risk only. For low or moderate risk activities only. 21 (see notes) No Virginia 

For common drainage locations that serve an area with 3 or more acres disturbed at one time, a temporary (or permanent) sediment basin providing 3,618 ft3 of storage per 

acre drained, or equivalent control measures, shall be provided where attainable until final stabilization of the site. 

The Virginia Erosion and Sediment Control regulations state that sediment traps and sediment basins shall be designed and constructed based on the total drainage area to be served by the trap or basin. The minimum storage capacity of a sediment trap shall be 134 cubic yards per acre of drainage area (3,618 ft3) and the trap shall only control 

drainage areas less than 3 acres. Surface runoff from disturbed areas that is composed of flow from drainage areas greater than or equal to three acres shall be controlled by a sediment basin. The minimum storage capacity of a sediment basin shall be 134 cubic yards per acre of drainage area. The outfall system shall, at a minimum, maintain the structural integrity of the basin during a 25-year, 24-hour duration storm event. Runoff coefficients used in runoff calculations shall correspond to a bare earth condition or those conditions expected to exist while the sediment basin is used. 

 7 No 

Washington 

Basin requirements are different for western and eastern parts of state—see manuals. 

Varies by time of year and location in state. West of the Cascade Mountains Crest: During the dry season (May 1–Sept. 30): 7 days; during the wet season (October 1–April 30): 2 days. 

2 or 7 (see notes) 

The Water Quality Standards for Surface Waters of the State of Washington WAC 173-201A-030 (1) (vi) states that turbidity shall not exceed 5 NTU over background turbidity when the background turbidity is 50 NTU or less, or has more than a 10 percent increase in turbidity when the background turbidity is more than 50 NTU. 

Washington, Small Parcel 
A-34 

State requirements: Environmental Protection Agency (EPA) 2007 

Soil stabilization 

State 

Sediment basin general 

requirements 

Sediment basins notes/other 

requirements Notes/other requirements Days Numeric standard 

West Virginia 

The 2002 permit states that sediment basins and traps will be installed with 3,600 ft3 of storage, 

measured from the bottom elevation of the structure to the top of the riser or weir, per acre of drainage and will have draw down times of 48 to 72 hours. For locations on a site that have a drainage area of 5 acres or less, a sediment trap which provides a storage volume equal to 3,600 ft3/acre of drainage area shall be 

installed. Half of the volume of the trap will be in a permanent pool and half will be dry storage. 

 7 No 

Wisconsin 

The Technical Standards document states that basins shall be used for greater than 5 to 100 acres. The sizing criteria for determining treatment surface area of a sediment basin are based on the soil texture and peak outflow during the 1-year, 24-hour design storm. The overflow spillway should be designed to carry the peak rate of runoff expected from a 10-year, 24-hour design storm. 

Not specified. N/A 

The current standard in Wisconsin (NR 151.11 pg 409) requires construction sites to implement erosion and sediment controls to reduce to the maximum extent practicable 80 percent of the sediment load carried in runoff on an annual basis, compared to a baseline of no sediment or erosion controls. 
A-35 

State requirements: Environmental Protection Agency (EPA) 2007 

Soil stabilization 

State 

Sediment basin general 

requirements 

Sediment basins notes/other 

requirements Notes/other requirements Days Numeric standard 

Wyoming No sizing criteria in permit. 

The 1999 Urban Best Management Practice (BMP) manual says use basins for 5 to 100 acres. 

Temporary stabilization (such as cover crop plantings, mulching or erosion controls blankets, surface roughening, etc.) for exposed soil areas where activities have permanently or temporarily ceased should be installed whenever practicable in areas where further work is not expected for 28 days or more. 

28 (see notes) 

Wyoming water quality regulations (Section 23, Page 1-20) require that discharge of substances attributable to or influenced by the activities of man shall not be present in quantities which would result in a turbidity increase for cold water fisheries and drinking water supplies (classes 1, 2AB, 2A, and 2B), shall not result in a turbidity increase of more than ten (10) nephelometric turbidity units (NTUs). In all warm water or nongame fisheries (classes 1, 2AB, 2B and 2C), the discharge of substances attributable to or influenced by the activities of man shall not be present in quantities which would result in a turbidity increase of more than 15 NTUs. An exception to shall apply to the North Platte River from Guernsey Dam to the Nebraska line during the annual silt run from Guernsey Dam. 

Puerto Rico District of Columbia 

Basin sizing for 2-year, 24-hour storm or 3,600 ft3/acre. 

Sediment basin requirements for drainage areas of 10 or more acres. 14 No 

For paand hrunoff for pouse is sidewareas0.3 in
A-36 

State requirements: 2004 Technical Development Document (TDD) Section 7 

State 

Sediment basin storage volumes (ft3/acre 

drained) 

Sediment basin requirements for 

drainage areas > 10 acres 

Seeding 

Alabama 3,600 Yes Alaska 3,600 Yes Arizona 3,600 Yes Arkansas 3,600 Yes California 3,600 Yes Colorado 1,800 No Connecticut 1,800 No Delaware 3,600 Yes Florida 3,600 Yes Florida, DEP, Northern District (applies only in NW Florida) Florida, South Florida Water Management District (General, Standard General, Noticed General and Individual Permits) Florida, Southwest Florida Water Management District Florida, St. Johns River Water Management District Florida, Suwannee River Water Management District Georgia 1,800 No Hawaii 1,800 No Idaho 3,600 Yes Illinois 1,800 No Indiana 1,800 No Iowa 3,600 Yes Kansas 3,600 Yes Kentucky 3,600 Yes Louisiana 3,600 Yes Maine 3,600 Yes Maryland 1,800 No Massachusetts 3,600 Yes Michigan 3,600 Yes 
A-37 

State requirements: 2004 Technical Development Document (TDD) Section 7 

State 

Sediment basin storage volumes (ft3/acre 

drained) 

Sediment basin requirements for 

drainage areas > 10 acres 

Seeding 

Minnesota 3,600 Yes Mississippi 3,600 Yes Missouri 1,800 No Montana 1,800 No Nebraska 1,800 No Nevada 3,600 Yes New Hampshire 3,600 Yes New Jersey 1,800 No New Mexico 3,600 Yes New York 3,600 Yes North Carolina 3,600 Yes North Dakota 1,800 No Ohio 1,800 No Oklahoma 3,600 Yes Oregon 1,800 No Pennsylvania 3,600 Yes Rhode Island 1,800 No South Carolina 3,600 Yes South Dakota 3,600 Yes Tennessee 3,600 Yes Texas 3,600 Yes Utah 3,600 Yes Vermont 1,800 No Virginia 3,600 Yes Washington 1,800 No Washington, Small Parcel West Virginia 3,600 Yes Wisconsin 1,800 No Wyoming 1,800 No Puerto Rico District of Columbia 3,600 Yes 
A-38 

State Requirements: 2002 Technical Development Document (TDD) Appendix A 

State 

Numeric standard or 

pollutant reduction 

requirements 

Minimum depth of runoff or 

storm return frequency to 

treat for water quality 

management (per acre) 

Maximum allowed 

denuded acreage or 

soil stabilization 

requirement No

Alabama Turbidity < 50 NTU. Alaska Total Suspended Solids greater than 20 microns. 2 year/6 hour An inspector must be qualified 

discharger. 

Arizona Arkansas 10 year/24 hour 

Developers must submit erosiand SWPPP before filing a nothan or equal to 10 acres muspermanent sediment basin. Simplement sediment traps and 

California 2 year/24 hour 

Inspections will be performed events, during extended storm events, and at least once eacextended storm events to idenimplement repairs or design cdepending on field conditions. responsible for inspecting and private roads for sediment. Counder the jurisdiction of the CaTransportation (CALTRANS) hregulations. 

Colorado 

Stormwater management plan for a 10-day review, as well as determined: A certification verManagement Plan (SWMP) is to state 10 days before beginnwell as being retained on site 

The SWMP shall be prepared engineering, hydrologic and p

Connecticut 80 percent TSS reduction. Delaware 80 percent TSS reduction. 0.5 inch Florida Florida , DEP, Northern District (only applies in NW Florida) 

80 percent TSS reduction. 0.5 inch *> 100 acres, 1 inch rainfall; < 
A-39 

State Requirements: 2002 Technical Development Document (TDD) Appendix A 

State 

Numeric standard or 

pollutant reduction 

requirements 

Minimum depth of runoff or 

storm return frequency to 

treat for water quality 

management (per acre) 

Maximum allowed 

denuded acreage or 

soil stabilization 

requirement No

Florida, South Florida Water Management District (General, Standard General, Noticed General and Individual Permits) 

 1 inch 

Florida, Southwest Florida Water Management District 0.5 inch Florida, St. Johns River Water Management District Turbidity less than 29 NTU. Florida, Suwannee River Water Management District 80 percent TSS reduction. 1 inch Georgia Turbidity less than 10 to 25 NTUs. 25 year/24 hour Turbidity < 25 NTUs for water

fisheries, or <10 NTUs for wat

Hawaii 

Construction shall be phased must be stabilized before anomaximum from removal of pretemporary stabilization. 

Idaho Illinois 3,600 ft3/acre Indiana Iowa 80 percent TSS reduction. Kansas Kentucky 

Goal of 80 percent TSS reduction (compared to preconstruction levels). 

Louisiana Maine 40 to 80 percent TSS reduction 2 year Maryland 

80 percent TSS reduction based on the average annual TSS loading from all storm events less than or equal to the 2-year/24-hour storm. 

2 year/24 hour 

Massachusetts 80 percent TSS reduction 2 year/24 hour Michigan 3,600 ft3/acre Sites greater than 10 acres re

sediment basin. 
A-40 

State Requirements: 2002 Technical Development Document (TDD) Appendix A 

State 

Numeric standard or 

pollutant reduction 

requirements 

Minimum depth of runoff or 

storm return frequency to 

treat for water quality 

management (per acre) 

Maximum allowed 

denuded acreage or 

soil stabilization 

requirement No

Minnesota 0.5 inch Mississippi Missouri Settleable Solids < 0.5 to 2.5 ml/L per hour. Settleable solids less than 2.5 

disturbance, and 0.5 ml/L per within sensitive areas. 

Montana 2 year/24 hour 

Dischargers must submit with stormwater erosion control plaEPA’s construction site SWPPonly when Montana Departmereviews and approves the SWbe conducted everyday during snowmelt periods. A registereprepare the SWESCP if the siAlso regulate down to 1 acre iwithin 100 feet of a surface wasediment and erosion control standard use BMPs. If other Bbe submitted with SWECP to slopes steeper than 3:1 and gsurface roughening is requiredused on drainage areas >1 acused only on drainage areas > sediment ponds should be use

10 acres. 

Nebraska Nevada New Hampshire New Jersey New Mexico New York 0.5 inch North Carolina 

20 acres of total disturbance at any given time for areas discharging to highquality waters. 

North Dakota Ohio 
A-41 

State Requirements: 2002 Technical Development Document (TDD) Appendix A 

State 

Numeric standard or 

pollutant reduction 

requirements 

Minimum depth of runoff or 

storm return frequency to 

treat for water quality 

management (per acre) 

Maximum allowed 

denuded acreage or 

soil stabilization 

requirement No

Oklahoma 3,600 ft3/acre 

A vegetated buffer zone of at retained or successfully estabdisturbed during construction intermittent streams on or adja

A vegetated buffer zone at learetained or established betweconstruction and all ephemeraTreatment volume is the lesse

volume of a 2-year, 24-hour s

Oregon 

If the site is greater than 20 accontrol plan must be prepared or Registered Landscape ArchProfessional in Erosion and Smust be submitted 90 days be

permittees must submit an OrStatement if they do not alreaOregon Department of Enviro

Pennsylvania 5 year Basins volumes should drain n

no longer than 7 days. 

Rhode Island 80 to 90 percent TSS reduction. 10 year South Carolina 80 percent TSS reduction. 3,600 ft3/acre 

Sediment trapping efficiency irequirement for any BMPs. Thstormwater control plans are aand location of BMPs, construdisturbed areas, property line standard notes, grassing specrequired volume for water qua

for a disturbed area of more thsediment basin of 3,600 ft3 an

than 10 acres, sediment trapsmeasures are needed for sideboundaries for the constructioinch rainfall runoff in a 24-houcoastal counties only. 

South Dakota 5 year Tennessee The permittee shall maintain r

maintenance. 

Texas 3,600 ft3/acre 
A-42 

State Requirements: 2002 Technical Development Document (TDD) Appendix A 

State 

Numeric standard or 

pollutant reduction 

requirements 

Minimum depth of runoff or 

storm return frequency to 

treat for water quality 

management (per acre) 

Maximum allowed 

denuded acreage or 

soil stabilization 

requirement No

Utah 1 inch or 24-hour storm event 

Where sites have been finally when runoff is unlikely becausduring seasonal arid periods iareas inspections shall be con30 days. Runoff volume from event for 10 or more disturbed water quality. For areas less tcalculations for the volume of not performed, a sediment ba

storage per acre drained or eqshall be provided. (1) Where tmeasures by the 14th day aftetemporary or permanently ceacover or frozen ground conditishall be initiated as soon as psemiarid areas, and areas expinitiation stabilization measureconstruction activity has tempis precluded by seasonal arid measures shall be initiated as 

Vermont Virginia 3,600 ft3/acre 

Sediment basins required for (except those with final stabilizacres, the same units are requand downslope boundaries of 

Washington, Large Parcel 24 hour/6 month 

2 days between October 1 and April 30 (i.e., the wet season); 7 days between May 1 to September 30 (dry season) 

Washington, Small Parcel 24 hour/6 month 

2 days between October 1 and April 30 (i.e., the wet season); 7 days between May 1 to September 30 (dry season) 

West Virginia 2 year Wisconsin 
A-43 

State Requirements: 2002 Technical Development Document (TDD) Appendix A 

State 

Numeric standard or 

pollutant reduction 

requirements 

Minimum depth of runoff or 

storm return frequency to 

treat for water quality 

management (per acre) 

Maximum allowed 

denuded acreage or 

soil stabilization 

requirement No

Wyoming Turbidity less than 10 to 15 NTUs. Puerto Rico District of Columbia 
Appendix B 

Literature Search Annotated Bibliography 
Appendix B: Literature Search Annotated Bibliography 

B-1 

Author(s): Peter T. Weiss,1

 John S. Gulliver,2 and Andrew J. Erickson3 

Date: 2007 

Title: Cost and Pollutant Removal of Stormwater Treatment Practices 

Organization: 1 Valparaiso University 

2, 3 University of Minnesota 

Source: Journal of Water Resources Planning and Management 

Volume 133, Issue 3, pp. 218-2229 (May/June 2007) 

Abstract: Six stormwater best management practices (BMPs) for treating urban rainwater 

runoff were evaluated for cost and effectiveness in removing suspended 

sediments and total phosphorus. Construction and annual operating and 

maintenance (O and M) cost data were collected and analyzed for dry extended 

detention basins, wet basins, sand filters, constructed wetlands, bioretention 

filters, and infiltration trenches using literature that reported on existing 

stormwater BMP sites across the United States. After statistical analysis on 

historical values of inflation and bond yields, the annual O and M costs were 

converted to a present worth based on a 20-year life and added to the 

construction cost. The total present cost of each stormwater BMP with the 67% 

confidence interval was reported as a function of water quality design volume, 

again with a 67% confidence interval. Finally, the mass of TSS and total 

phosphorus removed over the 20-year life was estimated as a function of the 

water quality volume. For the six stormwater BMPs investigated, results show 

that, ignoring land costs, constructed wetlands have been the least expensive to 

construct and maintain if appropriate land is available. However, since wetlands 

typically require more land area to be effective, land acquisition costs may result 

in wetlands being significantly more expensive than other stormwater BMPs 

that require less area. The results can be used by planners and designers to 

estimate both the total cost of installing a stormwater BMP and the 

corresponding total suspended solids and total phosphorus removal 

Comments: Summarizes recent cost work and presents best fit curves and 67 percent 

confidence intervals as ranges. The presentation of total capital costs assumes 

construction costs plus the present worth of 20 years of operating and 

maintenance costs. Paper was reviewed as part of EPA’s review of costs for 

permanent sedimentation ponds and sand filters. 

It also summarizes removal efficiencies for TSS and Phosphorus by BMP. 

Author(s): P. Kaini, K. Artita, and J. W. Nicklow 

Date: 2007 

Title: Evaluating Optimal Detention Pond Locations at a Watershed Scale 

Organization: Department of Civil and Environmental Engineering, Southern Illinois 

University 

Source: World Environmental and Water Resources Congress 2007 

Abstract: Structural BMPs like stormwater basins (detention and retention basins), 

wetlands, filter strips and grassland swales are extensively used as stormwater 

runoff controls. BMPs are often designed for peak flow reduction or pollution 
Appendix B: Literature Search Annotated Bibliography 

B-2 

control or can be considered for dual purpose in that they provide both water 

quality and quantity benefits by relying upon storage allocation and key 

mechanisms of setting filtration, sorption, biodegradation and 

evapotranspiration. In spite of previous studies, there exists neither a 

methodology nor a generalized model for selecting, placing, and sizing BMP 

combinations that cost-effectively promotes achievement of treatment goals at 

larger spatial scales. This paper presents part of an ongoing research effort to 

develop a new, comprehensive decision support tool for watershed-scale BMP 

design. The current model is designed to identify detention pond sizes that best 

achieve target peak flow reduction criteria. It is developed by coupling the 

U.S. Department of Agriculture’s (USDA) Soil and Water Assessment Tool 

(SWAT) and a genetic algorithm. The model is applied to Silver Creek 

watershed, a subbasin of the larger Lower Kaskaskia watershed in Illinois. The 

results show that detention ponds can be designed at a holistic, watershed scale 

to more effectively achieve peak flow reduction goals. Future work will focus 

on expansion of the model, which will also be disseminated through outreach 

workshops in portions of Illinois and surrounding states. 

Comments: Basin-wide design does not yet appear to be a viable option. The paper notes, 

“Despite these efforts [previous studies], there exists neither a methodology 

nor a generalized model for selecting, placing, and sizing BMP combinations 

that cost effectively promote achievement of treatment goals at the watershed 

scale. This paper presents ongoing research to develop a new, comprehensive 

decision support tool for watershed-scale BMP design.” 

Author(s): Fu-hsiung Lai, Jenny Zhen, John Riverson, and Leslie Shoemaker 

Date: 2006 

Title: SUSTAIN—An Evaluation and Cost-Optimization Tool for Placement of 

BMPs 

Organization: Tetra Tech, Fairfax, VA 

Source: World Environmental and Water Resources Congress 2006 

Abstract: To assist stormwater management professionals in planning for best 

management practices (BMPs) implementation, the U.S. Environmental 

Protection Agency (EPA) is developing a decision-support system for 

placement of BMPs at strategic locations in urban watersheds. This tool will 

help develop, evaluate, select, and place BMP options based on cost and 

effectiveness. The system was formerly called the Integrated Stormwater 

Management Decision Support Framework (ISMDSF), but will be tentatively 

called the System for Urban Stormwater Treatment and Analysis INtegration 

(SUSTAIN). SUSTAIN, a generic public domain framework, will provide a 

means for objective analysis of management alternatives among multiple 

interacting and competing factors. The desired outcome from the system 

application is a thorough, practical, and informative assessment considering 

economic, environmental, and engineering factors. SUSTAIN has seven key 

components: framework manager, ArcGIS interface, watershed model, BMP 
Appendix B: Literature Search Annotated Bibliography 

B-3 

model, optimization model, post-processor, and Microsoft Access database. 

They are integrated under a common ArcGIS platform. SUSTAIN supports 

evaluation of BMP placement at multiple scales from a few city blocks to 

large watersheds. 

Comments: Basin-wide design does not yet appear to be a viable option. EPA is 

developing a decision-support system for placement of BMPs at strategic 

locations in urban watersheds. This tool will help develop, evaluate, select, 

and place BMP options on the basis of cost and effectiveness. 

Author(s): Yuan Cheng, Ph.D., P.E. 

Date: 2006 

Title: Extended Analysis for Sediment Pond Design 

Organization: Benatec Associates, Inc. 

Source: World Environmental and Water Resources Congress 2006 

Abstract: An example of extended analysis for sediment pond design is presented. The 

sediment pond is designed to trap the suspended sediment carried by surface 

runoff from a construction site. Extended analysis can show dynamic changes 

of the velocity field in a pond as well as suspended sediment distribution from 

the pond inlet to the outlet. Results from the analysis can be used by designers 

to adjust pond size and shape for more effective reduction of sediment 

discharge that varies with time at the pond outlet. 

Comments: Presents site-specific two-dimensional finite analysis approach for designing 

pond shape and size. 

Author(s): Michael E. Barrett 

Date: 2003 

Title: Performance, Cost, and Maintenance Requirements of Austin Sand 

Filters 

Organization: Center for Research in Water Resources, University of Texas, Austin, TX 

Source: Journal of Water Resources Planning and Management 

Volume 129, Issue 3, pp. 234-242 (May/June 2003) 

Abstract: Five Austin-style sand filters were constructed by the California Department 

of Transportation (Caltrans) as retrofit projects for maintenance yards and 

park-and-ride facilities in the Los Angeles and San Diego metropolitan areas. 

Each of these filter systems included stormwater monitoring equipment for 

collection of flow weighted composite samples. In addition, detailed records 

were compiled of the design elements, construction costs, and type and 

amount of maintenance required at each of the sites. The construction costs 

were relatively high because of the retrofit nature of the project and the 

integration of the Caltrans storm-drain system with those of the adjoining 

metropolitan areas, which eliminated any opportunities for economies of scale. 

An analysis of performance using linear-regression techniques indicated that 

for sediment and almost all particle associated constituents, effluent 

concentration was independent of influent concentration. For instance, the 
Appendix B: Literature Search Annotated Bibliography 

B-4 

average suspended solids concentration in treated runoff was 7.8±1.2 mg/L (at 

the 90% confidence level) regardless of observed influent concentration. The 

constant effluent quality produced for the particulate constituents indicates that 

the calculation of a percent reduction is more indicative of the influent 

concentration rather than the performance of the filter itself. Rejuvenation of 

the filter bed was required at three sites after 3 years of operation when the 

solids loading to the system was between 5 and 7.5 kg/m2 of filter area. 

However, the clogging may have been accelerated by problems with the 

pumps that resulted in standing water on the filter for extended periods. Other 

maintenance activities consisted mainly of inspections, pump repair, and 

activities to reduce mosquito breeding. The main impediment to widespread 

implementation is the initial construction cost; however, modifications of the 

filter configuration and media may reduce these costs and increase 

effectiveness, thereby making the technology more attractive. 

Comments: Warrants further review if EPA evaluates use of sand filtration in meeting 

numerical standards. The article notes that it is difficult to determine the 

validity of the 1993 construction costs (“Guidance specifying management 

measures for sources of nonpoint pollution in coastal waters”). Note that the 

any use of the costs and removals from this study would need to consider that 

the site selection in this study was limited to relatively small, impervious 

watersheds. “The most important consideration was the extent to which runoff 

from unstabilized areas would be able to enter the filter. The biggest threat to 

the long-term successful operation of any filter is the introduction of excessive 

amounts of sediment that cause premature clogging of the filter media. For this 

reason, site selection was limited to relatively small, impervious watersheds 

(park-and-ride areas and maintenance stations).” 

Author(s): R. M. Hozalski, A. Erickson, and J. S. Gulliver 

Date: 2007 

Title: A New Approach for Assessing the Performance of Stormwater Best 

Management Practices 

Organization: University of Minnesota, Department of Civil Engineering 

Source: Proceedings of the World Environmental and Water Resources Congress 

2007 

Abstract: One approach for improving the quality of stormwater runoff before it enters 

the receiving water is to install stormwater BMPs. Stormwater BMPs include a 

wide range of systems (rain gardens, ponds, wetlands, underground 

proprietary sediment removal devices, etc.) used to reduce stormwater runoff 

quantity or improve stormwater quality, or both. No standard methodology for 

assessment of stormwater BMPs is available. Therefore, we propose a tiered 

approach to stormwater BMP assessment that is termed the “Four levels of 

assessment” (Table 1), that are numbered in order of increasing difficulty 

and cost. Developers of an assessment program should consider each of four 

levels of assessment in order, and consider advancing to next level only when 

requirements of the assessment program have not been satisfied. All 
Appendix B: Literature Search Annotated Bibliography 

B-5 

stormwater BMP assessment programs should include regularly scheduled (at 

least annual) visual inspections (level 1). In addition to visual inspections, 

capacity testing (level 2) and/or simulated runoff testing (level 3), if 

warranted, should be included in stormwater BMP assessment programs at 

regular intervals to determine the performance of a BMP immediately after 

installation and to determine how performance of a stormwater BMP is 

changing with respect to time, changes in the watershed, or both. If the goals 

of the assessment program cannot be met by capacity testing or simulated 

runoff testing, or these techniques are not feasible, then monitoring (level 4) 

should be implemented as part of the assessment program. 

Comments: Describes performance assessment of BMPs through visual inspections, 

capacity testing, simulated runoff testing, and/or monitoring. 

Author(s): J. M. Hathaway, W.F. Hunt, R.A. Smith, and K.L. Bass 

Date: 2007 

Title: Innovative Stormwater Treatment Practices in the Neuse and TarPamlico Basins 

Organization: North Carolina State University, Biological and Agricultural Engineering 

Department 

Source: Proceedings of the World Environmental and Water Resources Congress 

2007 

Abstract: Urbanization within North Carolina’s watersheds and the need for proactive 

mitigation led to the establishment of the North Carolina Ecosystem 

Enhancement Program (EEP) in July 2003. The EEP is responsible for the 

majority of mitigation efforts throughout the state. These efforts include the 

restoration, enhancement, and preservation of streams and wetlands, as well as 

the creation of stormwater best management practices (BMPs) for the purpose 

of maintaining and improving water quality and riparian habitats across the 

state. 

This project involves a partnership between EEP and the Biological and 

Agricultural Engineering Department (BAE) at North Carolina State 

University for the purpose of locating, designing, and monitoring stormwater 

BMPs. In addition, local governments and the North Carolina Cooperative 

Extension Service assist in project site selection and development. 

Two large river basins in North Carolina, Neuse and Tar-Pamlico, have 

historic, significant degradation to water quality partially because of 

urbanization and agricultural practices. Primary pollutants within these basins 

include nitrogen and phosphorous. To change the trend of degradation, the 

State of North Carolina enacted regulations for nitrogen and phosphorous 

removal specifically for these basins. These regulations provided for the 

funding of the EEP Nutrient Reduction Program by authorizing impact fees. 

Comments: Provides “an example of how academic institutions and state governments can 

work together to develop programs to identify design, and build retrofit 

stormwater BMPs.” 
Appendix B: Literature Search Annotated Bibliography 

B-6 

Author(s): Kelly A. Collins, William F. Hunt, and Jon M. Hathaway 

Date: 2007 

Title: Evaluation of Various Types of Permeable Pavements with Respect to 

Water Quality Improvement and Flood Control 

Organization: North Carolina State University, Biological and Agricultural Engineering 

Department 

Source: Proceedings of the World Environmental and Water Resources Congress 

2007 

Abstract: In many U.S. states, different permeable pavement types are considered to 

have the same capabilities in reducing runoff, and they are not credited with 

improving water quality. To test various permeable pavement designs, a 

parking lot consisting of four different types of permeable pavements and 

standard asphalt was constructed in Kinston, NC. The permeable pavement 

sections consist of pervious concrete (PC), permeable interlocking concrete 

pavers (PICP) with 8.5 % void space, PICP with 12.9 % void space, and 

concrete grid pavers (CGP), each covering a 1200 sq. ft. area with a 10 in. 

gravel storage layer. The purpose of this study is to evaluate and compare the 

effects of each pavement type on water quality and runoff reduction. Site 

analyses on every rainfall event began in March, 2006, and will continue 

through March, 2007. Preliminary results indicate significant (p<0.05) peak 

flow and volume reductions from all permeable pavements. Additionally, there 

has been little to no runoff observed from any of the pervious sections. 

Pollutant removal performance by the pavements has widely varied. As a 

result of this study, it is expected that the state of North Carolina will make a 

judgment on how much pollutant removal credit permeable pavement types 

should receive. Also, this study may be used to determine whether or not 

stormwater credit should vary based on pavement type. 

Comments: Evaluates parking lot runoff from various permeable pavement designs. 

Author(s): Ben Urbonas,1

 and Jim Wulliman2 

Date: 2007 

Title: Stormwater Runoff Control Using Full Spectrum Detention 

Organization: 1 Urban Drainage and Flood Control District, Denver, CO 

2 Muller Engineering Company, Lakewood, CO

Source: Proceedings of the World Environmental and Water Resources Congress 

2007 

Abstract: The goal of controlling peak flow rates at individual sites to pre-developed 

levels can be met using detention basins for design storms from 2- to 100-year 

return periods. However control of peak storm runoff flows along receiving 

streams by multiple detention basins operating simultaneously within larger 

urban catchments are much more difficult to achieve. The latter topic was 

studied in the past by several investigators, but the findings were very limited 

in scope and were focused primarily on larger runoff events such as the 10-

year to 100-year flows. At the same time, there is evidence that stream 
Appendix B: Literature Search Annotated Bibliography 

B-7 

geometry, water quality and aquatic habitat are impacted significantly whether 

this type of detention is used, or not, as areas urbanize. The profound 

hydrologic and geomorphic changes caused by urbanization require more 

robust control of the frequently occurring, smaller, runoff events. In response 

to this, different approaches toward designing stormwater detention were 

investigated and modeled by the authors. This testing was first done using 

design storm protocols employed by the Urban Drainage & Flood Control 

District for the Denver area of Colorado and then followed up using the EPA 

SWMM 5.0 model calibrated to 15-years of recorded 5-minute rainfall (5 

gages) and runoff (2 gages) data for a 3.1 square mile watershed. This paper 

presents the findings most applicable for the Denver region and other locations 

having similar precipitation patterns; however, the underlying principles used 

to develop this concept can be used to develop design protocols for other 

hydrologic regions of the USA and other countries. 

Comments: Describes a watershed-wide approach for minimizing the excess urban runoff 

volume (difference between urban and pre-development), including smaller 

rain events such as the 2-year storm. 

Author(s): Dianna M. Hogan1, 2 and Mark Walbridge3 

Date: 2007 

Title: Best Management Practices for Nutrient and Sediment Retention in 

Urban Stormwater Runoff 

Organization: 1

Department of Environmental Science and Policy, George Mason University, 

Fairfax, VA 

2

Eastern Geographic Science Center, U.S. Geological Survey, Reston, VA 

3

Department of Biology, West Virginia University, Morgantown, WV 

Source: Journal of Environmental Quality 

Abstract: Stormwater management infrastructure is used in urban areas to alleviate 

flooding caused by decreased landscape permeability from increased 

impervious surface cover (ISC) construction. In this study, we examined two 

types of stormwater detention basins, SDB-BMPs (stormwater detention 

basin-best management practice), and SDB-FCs (stormwater detention basin–

flood control). Both are constructed to retain peak stormwater flows for flood 

mitigation. However, the SDB-BMPs are also designed using basin 

topography and wetland vegetation to provide water quality improvement 

(nutrient and sediment removal and retention). The objective of this study was 

to compare SDB (both SDB-BMP and SDB-FC) surface soil P concentrations, 

P saturation, and Fe chemistry with natural riparian wetlands (RWs), using 

sites in Fairfax County, Virginia as a model system. 

Comments: Study compares nutrient and sediment retention in urban stormwater runoff for 

stormwater detention basin BMPs and stormwater detention basin flood 

control. 
Appendix B: Literature Search Annotated Bibliography 

B-8 

Author(s): Arvind Narayanan and Robert Pitt 

Date: 2006 

Title: Cost of Urban Stormwater Control Practices 

Organization: University of Alabama 

Source: This report is a consolidated and summary of information obtained from the 

following major reports on costs of stormwater controls, plus additional 

specialized references: 

 Costs of Urban Nonpoint Source Water Pollution Control Measures

prepared by Southeastern Wisconsin Regional Planning Commission 

1991 

 Costs of Urban Stormwater Control by Heaney, Sample, and Wright for 

USEPA 2002 

 BMP Retrofit Pilot Program prepared by CALTRANS 2001 

Abstract: This research presents a method to determine the costs of several types of 

stormwater control practices including the costs of conventional drainage 

system. Several published literature sources were reviewed that contained 

costs of control practices. Standard unit cost data used in developing the 

conventional conveyance drainage system costs were obtained from RS 

Means. The cost data were transformed into equations and used to develop the 

cost module for the Source Loading and Management Model WinSLAMM). 

An Excel spreadsheet model was also developed to estimate the costs of 

conventional stormwater drainage systems based on the published unit cost 

data. In an example, the costs estimated by the spreadsheet model were 

compared to the costs associated with the stormwater control practices as 

estimated by WinSLAMM for a 250-acre industrial site in Huntsville, AL. The 

costs of site biofiltration, large-scale grass swales, and a wet detention pond 

were compared to the costs for the conventional drainage system. The cost 

information available from published literature sources and other references 

were in the form of tables and equations. The cost information gathered 

provided regional cost estimates for the control practices for a specific year. 

Cost indices published by the Engineering News-Record were used to estimate 

the present costs from historical cost information and at locations where cost 

information is unavailable. These cost indices, from 1978 to 2005, were 

incorporated into WinSLAMM and the spreadsheet model. Based on the cost 

data obtained form Southeastern Wisconsin Regional Planning Commission 

(1991), the component(s) that affected the control practice cost the most were 

also analyzed 

Comments: References previously used documents for sedimentation basins (1976 EPA, 

Cost Estimating Manual—Combined Sewer Overflow Storage and Treatment, 

referenced in subsequent EPA documents (1993 and 1999)) and detention 

ponds (Young et al. 1996, the out-of-date 1986 equations referenced in 

Schueler 2000). 

Sand filter information references CALTRANS 2004, which was included in 

EPA’s review of sand filters. 
Appendix B: Literature Search Annotated Bibliography 

B-9 

Author(s): Dennis Jurrie, P.E. 

Date: Unknown 

Title: Flocculation of Construction Site Runoff in Oregon 

Organization: Sisul Engineering 

Source: Unknown 

Abstract: 

Comments: Describes flocculation for treating stormwater runoff from construction sites. 

Includes sampling results for Sumalchlor 50 (a Polyaluminum Chloride) at a 

corporate park construction site in Oregon. Provides a cost to treat and 

flocculate stormwater runoff of $0.08 per gallon of water treated. Warrants 

additional review as part of the evaluation of numerical standards.

Author(s): Eric Woodhouse and Tiffany Leop 

Date: 2007 

Title: Temporary Slope Protection: Cost Versus Effectiveness 

Organization: Landscape Development, Inc. 

Source: StormCon 2007 

Abstract: Landscape Development, Inc., conducted a study in Santa Clarita, CA. Eight 

products and applications were tested on 1000 square foot, 2:1 slope panels 

during the heavy rain season of 2004-2005. The rains in this area accumulated 

to over 40 inches between October and May. The products and applications 

tested include straw blanket, blown straw with organic binder-tackifier, 

straw/coco blanket, coconut blanket, jute netting, wood fiber mulch and 

organic binder, a preblended stabilized fiber matrix (SFM) with two stabilizer 

components (a tackifier and cross link binder), and another stabilized fiber 

matrix (SFM) with one stabilizing component consisting of wood fiber mulch 

with polyacrylimide stabilizer. Four soil loss samples were taken over the 

course of the study. The weight of the soil lost was accumulated and used in 

comparing the performance of the varying products and applications. The 

blanket products performed better, overall, for retaining the soil on the slope 

face when compared for amount of soil lost per inch of rainfall. The cost 

comparison for all the products and applications showed comparable pricing 

when extended over the duration of the product/application’s effective lifeline. 

Cost comparisons for the various applications in regards to lifespan and price 

per square foot are presented in this paper. 

Comments: Provides a comparison of soil loss, price per square foot, and lifespan for 

various erosion controls (straw blanket, blown straw with organic bindertackifier, straw/coco blanket, coconut blanket, jute netting, wood fiber mulch 

and organic binder, a preblended stabilized fiber matrix (SFM) with two 

stabilizer components (a tackifier and cross link binder), and another stabilized 

fiber matrix (SFM) with one stabilizing component consisting of wood fiber 

mulch with polyacrylimide stabilizer). The study notes, “It can be seen that 

cost is directly correlated with the lifespan of the application as well as the 

effectiveness in minimizing soil loss.” The article might be useful for 

inclusion in the updated technical development document. 
Appendix B: Literature Search Annotated Bibliography 

B-10 

Author(s): David Wachal 

Date: 2007 

Title: BMP Selection for Land Disturbance: A Methodology Based on 

Efficiency, Cost, and Site Management Goals 

Organization: City of Denton, Texas 

Source: StormCon 2007 

Abstract: This paper presents a methodology for developing a BMP selection tool for 

disturbed hillslopes based on BMP efficiency, BMP implementation costs, and 

site management goals. To demonstrate how the methodology was developed 

and applied, a case study focusing on Natural Gas Exploration and Production 

(NGE&P) sites is presented. Version 2 of the Revised Universal Soil Loss 

Equation (RUSLE2) was used to evaluate sediment yields for several 

combinations of BMPs, slopes, and soil types, and based on the modeling 

results, BMP efficiency values were computed for each possible combination. 

Efficiency values for the various slope and soil combinations revealed that 

both slope and soil type influences the effectiveness of the BMPs. The 

efficiency values were incorporated into a selection tool that also included 

estimated BMP implementation costs. While this paper focuses on NGE&P 

sites, the methodology presented is easily adaptable to other types of disturbed 

site conditions. 

Comments: Project evaluated BMP efficiencies and costs for BMPs (seeding, mulching, 

erosion blanket, silt fence, and vegetated filter strip) and BMP combinations 

for disturbed hillsides in Natural Gas Exploration and Production. The method 

uses RUSLE2 (for possible combinations of three soil types and three slope 

profiles) as an erosion prediction tool. The methodology then uses the Best 

Management Practices Assessment Tool (BMPSAT) to evaluate efficiencies 

and costs on the basis of soil and slope combinations. The article states that 

BMPSAT is an Excel spreadsheet that could be modified for additional 

evaluations of BMPs or site characteristics and that the flexibility of RUSLE2 

allows BMPSAT to be easily customized for complex or simple slopes, 

specific site characteristics, and to include additional BMPs. 

Costs for the BMPs included in the analysis are from EPA-842-B-02-003 

(National management measures to control nonpoint source pollution from 

urban areas – draft). The modeling methodology could be of interest for soil 

modeling. 

Author(s): Autumn DeWoody 

Date: 2007 

Title: Cost-Effectiveness of Stormwater Infiltration BMPs in Los Angeles 

County 

Organization: University of California, Riverside 

Source: StormCon 2007 
Appendix B: Literature Search Annotated Bibliography 

B-11 

Abstract: Current stormwater regulations require infiltration and/or treatment of the 

runoff generated by a minimum rain depth or flow rate at new developments 

or redevelopments above a threshold size, but most existing facilities in Los 

Angeles are not required to mitigate their onsite runoff. Available information 

on stormwater infiltration BMP costs is often vague or inadequate and 

outdated, and there is little data on urban Southern California BMP costs. This 

research aims to provide clarity to decision makers on parcel-level strategies 

that comply with stormwater regulations and boost groundwater supply. It 

focuses on the retrofit of existing nonresidential parcels with stormwater 

infiltration BMPs. The research begins with five cost/benefit case studies, then 

follows with a BMP cost analysis using local area BMP data, and then 

presents a cost-benefit analysis of parcel-level infiltration across a wide 

variety of land uses, parcel sizes, and infiltration rates. 

Comments: On the basis of a Los Angeles and San Gabriel Rivers Watershed Council 

study evaluating the potential to retrofit typical urban neighborhoods to 

promote infiltration, this paper evaluates the costs and benefits of retrofits to 

determine whether the benefit of increased groundwater recharge justified the 

expense of a BMP system. The cost/benefit analysis uses the actual capital 

costs for the retrofit sites; the source costs were not presented. 

Author(s): Jason Ziemer 

Date: 2007 

Title: Complying with NPDES Phase II Requirements on a Major Highway 

Construction Project with the Implementation of an Emerging BMP 

Organization: Clear Water Compliance Services, Inc. 

Source: StormCon 2007 

Abstract: The Washington State Department of Transportation (WSDOT) and their 

general contractors began a $126.3M construction project along 3.5 miles of 

State Route (SR) 18 in Maple Valley, Washington in September, 2003. The 

project included 15 new bridges, over 40 retaining walls and required more 

than 850,000 cubic yards of earth moving. Initial stormwater engineering and 

planning focused primarily on post construction stormwater considerations 

included drainage improvements, construction of 14 stormwater storage and 

treatment ponds, and the enhancement of 49 acres of wetlands. Planning for 

construction-phase stormwater focused almost entirely on implementation and 

maintenance of BMPs and was absent of specific considerations for meeting 

water quality standards. This lack of planning eventual caused serious 

problems and project delays. During the spring of 2004, WSDOT discovered 

the general contractor had filled a wetland with woody debris without a 

permit. Immediate action was taken by WSDOT, the U.S. Army Corps of 

Engineers and the Washington State Department of Ecology (Ecology). This 

paper presents the aggressive implementation of BMPs, including the use of 

erosion control practices that had to be taken for the project to be in 

compliance. Issues of turbidity were also discussed. 
Appendix B: Literature Search Annotated Bibliography 

B-12 

Comments: Example of a highway project in Washington State using a Chitosan-enhanced 

sand filtration system to meet state requirement of <= 5 NTU above 

background. Project specifications required treating 700 gpm with a 

continuous effluent turbidity of less than 10 NTU. Article reports nearly 

40,000 turbidity data points show an average turbidity of 236 NTU, 42.4 NTU 

after pretreatment, and 1.04 NTU average discharge. The average cost per 

gallon treated for the project was $0.017 per gallon. Warrants additional 

review as part of the evaluation of numerical standards. 

Author(s): Neil Myers and Ted Blahnik 

Date: 2007 

Title: The Development Paradigm Shift: A Case Study 

Organization: Williams Creek Consulting 

Source: StormCon 2007 

Abstract: This paper presents a case study from Williams Creek Consulting, a firm 

specializing in LID and sustainable natural system designs for construction 

stormwater management. Because of increased regulatory acceptance, 

development companies are now using more sustainable and lower impact 

development solutions to provide for regulatory compliance, improve 

marketability, increase profit and improve overall quality of life for the 

community. A prime example of acceptance for sustainable sites engineering 

for natural resource and stormwater management solutions is at a 1,700 acre 

mixed-use development in the Midwest. This site is among the national 

developer’s first attempt at using the more sustainable, lower impact systems 

on a large scale and challenged the traditional design and construction delivery 

methods within the Midwest. As the site begins to be developed, significant 

cost savings are being realized during construction. BMPs planned for this 

project included constructed wetlands, vegetated swales, bioretention and rain 

gardens, wetland fringe along ponds, linear dry landscaped basins, and more. 

Comments: Might be useful for benefits analysis. Case study provides detailed cost 

savings from low-impact development (vegetated swale, bioretention and rain 

gardens, wetland fringe pond, and dry landscaped basins), reducing costs for 

reinforced concrete storm pipes, storm structures, and site fill. 

Author(s): Jamie Weist and Don Alexander 

Date: 2007 

Title: Saving Time and Money on Construction-Site SWPPPs 

Organization: Woolpert, Inc. 

Source: StormCon 2007 
Appendix B: Literature Search Annotated Bibliography 

B-13 

Abstract: Designed for contractors who must comply with federal, state, and local 

stormwater, erosion, and sediment control regulations, this presentation shows 

how to reduce the likelihood of fines due to noncompliance. A methodology 

and automated process have been developed to help prepare stormwater 

pollution prevention plans and comply with permit requirements, particularly 

for contractors who are dealing with multiple construction sites. 

Comments: The full text of the article is not available. 
Appendix C 

Analysis of Construction Industry Trends Using 

Notice of Intent Records 
Appendix C: Analysis of Construction Industry Trends Using Notice of Intent Records 

C-1 

As described in the Economic Analysis for the Final Rule, the long-term trend analysis provides 

an estimate of total acreage for the 2008 trend year. To develop the baseline profile of acreage 

activity by state and construction activity sector, the U.S. Environmental Protection Agency 

(EPA) distributed the approximately 853,000 acres in proportion to the value of construction 

estimated to occur in each state/activity sector. The percentage of the value of construction for 

each state and activity sector was based on the percentage of firms, within each revenue range 

category, that perform work in that state/activity sector combination. For more information, see 

Chapter 4 of Economic Analysis for Final Effluent Guidelines and Standards for the 

Construction and Development Category (USEPA 2009). 

The baseline analysis develops the estimate of total activity, in terms of acres of construction, 

and apportions this acreage out among the state and activity sectors, but it does not account for 

the number of acres developed in different project configurations, which can vary across a 

variety of factors but most especially with respect to project size and duration. To accurately 

characterize the heterogeneity in construction project size and duration, EPA relied on projectspecific information in Notice of Intent (NOI) records. To obtain required coverage under a 

construction general permit, a discharger submits to the permitting authority an NOI to be 

covered under the general permit. By submitting the NOI, the discharger acknowledges that it is 

eligible for coverage under the general permit and agrees to the conditions in the published 

general permit. 

The information required under an NOI varies from state to state, and state permitting authorities 

are not required to submit their NOI information to EPA. However, some states have voluntarily 

submitted their NOI data to the Agency. Table C-1 lists the 37 states from which EPA was able 

to obtain NOI data. These data sets varied widely in the number of years covered, the 

information collected, and the completeness of the records. Of the 11 states that report both 

disturbed acreage and project duration (Arizona, California, Delaware, Minnesota, New York, 

Oklahoma, South Carolina, South Dakota, Tennessee, Vermont, Virginia) only California, New 

York, and South Carolina categorized project by construction type (i.e., residential, 

transportation). That information was necessary for developing distributions of project size and 

duration for each of the activity sectors. 

Table C-1. State NOI data assessed for the C&D rulemaking 

State Disturbed area Project duration Record count 

Alabama* No No 13,276 

Alaska No Yes 1,233 

Arkansas No No 1,958 

Arizona* Yes Yes 13,591 

California* Yes Yes 20,756 

Colorado* No No 4,057 

Connecticut* No No 4,019 

Delaware Yes Yes 2,904 

Georgia Yes No 21,914 

Florida* No No 22,662 

Idaho* No Yes 2,203 

Illinois No Yes 4,457 

Indiana Yes No 9,825 

Louisiana* No No 1,441 

Maine* No No 1,410 
C-2 

State Disturbed area Project duration Record count 

Maryland Yes No 12,542 

Massachusetts No Yes 2,826 

Michigan* No No 13,016 

Minnesota* Yes Yes 21,191 

Mississippi* No No 1,624 

Nebraska* Yes No 1,232 

New Hampshire No Yes 1,957 

New Jersey No No 42 

New Mexico No Yes 3,673 

New York* Yes Yes 6,972 

North Dakota* No No 2,151 

Ohio No Yes 9,181 

Oklahoma* Yes Yes 1,965 

South Carolina Yes Yes 12,576 

South Dakota* Yes Yes 1,381 

Tennessee Yes Yes 8,851 

Vermont* Yes Yes 1,225 

Virginia Yes Yes 9,032 

Washington* No No 1,800 

West Virginia Yes No 1,219 

Wisconsin* Yes No 11,190 

Wyoming* No No 2,099 

* These states also had some additional NOI records that were covered under the EPA General 

Permit. However, none of the NOI information gathered under the EPA Construction General 

Permit reports disturbed acreage. 

Because state NOI data were not gathered for the purpose of deriving distributions, EPA had to 

scrutinize the records to ensure that the distributions would reflect accurate and comparable data 

sets. EPA inspected the data and removed records that it considered inappropriate for developing 

size and duration distributions. For each of the three states, EPA performed the following steps: 

 Removed all records where the project began before 2003. EPA did this to ensure that 

the data represented years in which projects less than 5 but greater than 1 acre were 

covered. Before 2003, some states did not require projects less than 5 acres to file for 

permit coverage. 

 Removed records that were blank for either disturbed acreage, construction start date, 

or construction end date. 

 Removed records with duration values that were one day or shorter, or that were 

longer than 4 years because those were considered to have a high potential for 

containing an erroneous start or end date. 

 Removed all records where disturbed acres was less than one acre. 

 Several records in California appeared to have excessively high values for disturbed 

acreage. The project addresses for those records were checked using satellite imagery. 

If the record appeared to reflect the square footage for the site rather than acreage, the 

value was adjusted accordingly. If EPA could not determine what the correct acreage 

was for the site, the record was removed. Approximately 11 of the California records 

were either adjusted or removed. 
C-3 

 Removed files that had a high potential for being a duplicate record because they 

shared project names, owner names, addresses, disturbed acreage, and activity dates 

with another record. 

To reflect differences in regional development patterns, geography, and demographic trends, 

EPA used the distribution from each state to represent the region of the country in which it is 

located. New York is considered representative of the Northeastern and Great Lake states, 

California is considered representative of the West Coast and the Southwestern states, while 

South Carolina is considered representative of the Southeastern states. That left several of the 

Midwestern and Rocky Mountain States unrepresented. To develop a representative distribution 

for those states, EPA performed the same six steps as performed on the other three state data 

sets. The Agency then reviewed each of the remaining 1,159 records and assigned each project 

into either residential, nonresidential, or transportation according to the project name and 

description of activity fields. That allowed EPA to develop a fourth regional distribution. Table 

C-2 identifies which states are assigned to each of the regionally representative project 

distributions. 

Table C-2. Assignment of regionally representative project distributions 

according to NOI data from four states 

States with regionally 

representative NOI data 

States assigned regionally representative project 

distribution 

California Arizona Oregon 

Colorado Texas 

Nevada Utah 

New Mexico Washington 

New York Connecticut Michigan 

Delaware Minnesota 

Dist. of Columbia New Hampshire 

Hawaii New Jersey 

Illinois Ohio 

Indiana Pennsylvania 

Maine Rhode Island 

Maryland Vermont 

Massachusetts Wisconsin 

South Carolina Arkansas Missouri 

Florida North Carolina 

Georgia Oklahoma 

Kentucky Tennessee 

Louisiana Virginia 

Mississippi West Virginia 

South Dakota Alaska Montana 

Idaho Nebraska 

Iowa North Dakota 

Kansas Wyoming 

Reference 

USEPA (U.S. Environmental Protection Agency). 2009. Economic Analysis for Final Effluent 

Guidelines and Standards for the Construction and Development Category (EPA-821-R-09-

011). U.S. Environmental Protection Agency, Office of Water, Washington, DC. 
Appendix D 

Precipitation Data Representative of Major 

U.S. Metropolitan Areas
Appendix D: Precipitation Data Representative of Major U.S. Metropolitan Areas 

D-1 

Overview 

The U.S. Environmental Protection Agency (EPA) used precipitation data to estimate costs and 

pollutant load reductions for regulatory options. EPA developed a series of regional pollutant 

load models using data from 11 indicator cities for the loadings analysis. These indicator cities 

are shown in Table D-1. For the costing analysis, EPA used rainfall data for one indicator city in 

each state. EPA used the same 11 indicator cities for the states described in Table D-1. For the 

remaining states, a major urban area was chosen as the indicator; which in most cases was the 

capital city. Precipitation data was acquired for each city using the National Oceanic and 

Atmospheric Administration (NOAA) National Weather Service (NWS) Precipitation Frequency 

Data Server (PFDS). The Hydrometeorological Design Studies Center (HDSC) within the Office 

of Hydrologic Development of the NWS is in an ongoing process of updating its precipitation 

frequency estimates, which are available in NOAA Atlas 14 format. At the time of this writing, 

only a portion of the United States had been updated into this format. Atlas 14 supercedes 

precipitation frequency estimates contained in previous NWS publications. The updates are 

based on more recent and extended data sets, currently accepted statistical approaches, and 

improved spatial interpolation and mapping techniques. A complete list of NWS publications is 

listed in Table D-2. The rainfall analysis data is DCN 43095 and an index of spatial data analyses 

conducted for the proposed rule is DCN 43097 the Administrative Record. 

Table D-1. EPA Region indicators 

EPA Region Indicator city 

1 Manchester, NH 

2 Albany, NY 

3 Washington, DC, VA, and MD 

4 Atlanta, GA 

5 Chicago, IL—IN 

6 Dallas, Fort Worth, and Arlington, TX 

7 Kansas City, MO and KS 

8 Denver and Aurora, CO 

9 Las Vegas, NV 

10 Boise City, ID, and Seattle, WA 
Appendix D: Precipitation Data Representative of Major U.S. Metropolitan Areas 

D-2 

Table D-2. Current NWS precipitation frequency publications 

Location 5 min–60 min 1 hr–24 hr 2 day–10 day 

Arizona, Nevada, New Mexico, Utah, and 

Southeast California 

NOAA Atlas 14 

(2003) 

NOAA Atlas 14 

(2003) 

NOAA Atlas 14 

(2003) 

Remainder of the Western United States 

Arkell & Richards 

(1986) 

Frederick & Miller 

(1979) 

NOAA Atlas 2 

(1973) 

Tech. Paper 49 

(1964) 

Delaware; Illinois; Indiana; Kentucky; Maryland; 

New Jersey; North Carolina; Ohio; Pennsylvania; 

South Carolina; Tennessee; Virginia; West 

Virginia; and Washington, DC 

NOAA Atlas 14, 

Volume 2 (June 

2004) 

NOAA Atlas 14, 

Volume 2 

(June 2004) 

NOAA Atlas 14, 

Volume 2 

(June 2004) 

Remainder of the Eastern United States Tech. Memo 35 

(1977) 

Tech. Paper 40 

(1961) 

Tech. Paper 49 

(1964) 

Hawaii Tech. Paper 43 

(1962) 

Tech. Paper 43 

(1962) 

Tech. Paper 

51(1965) 

Alaska Tech. Paper 47 

(1963) 

Tech. Paper 47 

(1963) 

Tech. Paper 52 

(1965) 

Puerto Rico NOAA Atlas 14, 

Volume 3 

NOAA Atlas 14, 

Volume 3 

NOAA Atlas 14, 

Volume 3 

NOAA Atlas 14 contains precipitation frequency estimates with associated confidence limits for 

the United States for 5-minute through 60-day durations at average recurrence intervals of 1 year 

through 1,000 year. The estimates are based on the analysis of annual maximum series and then 

converted to partial duration series results. Figure D-1 shows an example of the Atlas 14 

interface. 
Appendix D: Precipitation Data Representative of Major U.S. Metropolitan Areas 

D-3 

Figure D-1. Example of PFDS Atlas 14 – Virginia. 

The Atlas 14 interface allows the user to choose from various data parameters, such as data type 

(precipitation depth or precipitation intensity); units (English or Metric); time series type (partial 

duration or annual maximum); and the weather station location. The rainfall data results used in 

EPA’s analysis are shown in Table D-3. 

For the states not currently updated by NOAA Atlas 14, the rainfall-frequency values for 

selected durations were estimated using a series of maps presented in the older NWS 

publications. The current modeling effort focused on the 2-year 24-hour, 10-year 24-hour, 

25-year 24-hour, and 10-year 6-hour precipitation data. Therefore, the data for the remainder of 

the Western United States were estimated by using NOAA Atlas 2, Precipitation Frequency 

Atlas of the Western United States (1973), which are generalized maps presented for 6- and 

24-hour point precipitation for the return periods of 2, 5, 10, 25, 50, and 100 years. Atlas 2 is 

published in separate volumes for each of the states. Similarly, the maps presented in the 

corresponding Technical Paper were used for the remainder of the Eastern United States and 

Hawaii. (Alaska was not included in this analysis because EPA lacked sufficient data on the 

annual amount of construction activity occurring in Alaska). Examples of an Atlas 2 map and a 

map from a Technical Paper are shown in Figures D-6 and D-7, respectively. 

Precipitation frequency results not generated by Atlas 14 for the remaining states (i.e., using 

Atlas 2 or Technical Paper maps) are presented in Table D-4. The rainfall depths in Table D-4 
Appendix D: Precipitation Data Representative of Major U.S. Metropolitan Areas 

D-4 

were estimated by identifying the target city on the Atlas 2 or Technical Paper map and linearly 

approximating the rainfall value. For example, if a city fell between a depth of 4.5 and 5 inches 

and the city was approximately 20 percent of the map distance from the 5-inch line, a rainfall 

depth of 4.9 inches was estimated. Note that the maps provided data for depth only. Intensity 

estimates were calculated by dividing the duration (e.g., 6- or 24-hour) by the depth. 

Additionally, Atlas 2 depths were converted from tenths of an inch to inches. 

The above data were used in modeling state basin size requirements. New York and Wisconsin 

specified alternate basin size storm events (10-year, 24-hours and 1-year, 24-hours, respectively). 

Therefore, a depth of 4.4 inches for a 10-year 24-hour event in Albany, New York, and a depth 

of 2.5 inches for a 1-year 24-hour event in Madison, Wisconsin were also estimated. 

For use in estimating the annual volume of runoff produced, the PRISM Group analysis and 

mapping services, developed by the Oregon State University, was used to obtain annual 

precipitation data for all indicator cities and gauge locations. The PRISM data sets were 

developed through projects funded partly by the U.S. Department of Agriculture (USDA) 

Natural Resources Conservation Service, USDA Forest Service, NOAA Office of Global 

Programs, and others. PRISM Group is responsible for nearly all major climate mapping efforts 

at the federal level in the United States. Some examples of recent and current projects include the 

following: 

 Climate Atlas of the United States, for the National Climatic Data Center 

 Precipitation and temperature maps for all 50 U.S. states and possessions, for USDA 

Natural Resources Conservation Service 

 103 years of monthly temperature and precipitation maps for the lower 48 states, for 

NASA/NOAA Office of Global Programs 

The PRISM Model is a knowledge-based system that uses point measurements of precipitation, 

temperature, and other climate elements to produce continuous, digital coverages. Figure D-2 

provides an example of the PRISM Data Explorer interface. 
Appendix D: Precipitation Data Representative of Major U.S. Metropolitan Areas 

D-5 

Figure D-2. Example of PRISM Interface. 

The PRISM interface allows users to choose from various parameters such as months (January 

through December, all months, and annual); start and stop years (1895 to current); and units 

(English or Metric). The PRISM-required inputs are latitude and longitude points for all indicator 

cities and gauge locations. Results were compiled of annual precipitation totals for the years of 

1895 to 2007 from which a determination was made for the annual average for each indicator 

city in each state (presented in Table D-5). The latitude and longitude point inputs for the PRISM 

Gridcell analysis were obtained from NOAA Atlas 14 weather station locations [e.g., Phoenix 

WSFO AP, AZ (02-6481)] where possible. For the states not currently updated by NOAA Atlas 

14, the U.S. Geological Survey (USGS) Geographic Names Information System (GNIS) was 

used to obtain latitude and longitude points. 

Figure D-3 provides an example of the USGS interface. 
Appendix D: Precipitation Data Representative of Major U.S. Metropolitan Areas 

D-6 

Figure D-3. Example of USGS GNIS Interface. 

The indicator city and the state were input into this interface and then Populated Place under the 

Feature Class field was selected for obtaining the latitude and longitude points. Once Send Query

is selected, the results are displayed in a table format as shown in the Figure D-4 example. The 

user can then click the desired Feature Name in the list for a Detailed Report as shown in the 

example in Figure D-5. 

Figure D-4. Example of USGS GNIS Query Results. 
Appendix D: Precipitation Data Representative of Major U.S. Metropolitan Areas 

D-7 

Figure D-5. Example of USGS GNIS Query Detail Report. 

The Sequence 1 latitude (DEC) and longitude (DEC) data coordinates from the USGS GNIS 

query results were used for use in the PRISM model for each indicator city. 
D-8 

Table D-3. NOAA Atlas 14 precipitation frequency results 

Precipitation frequency estimates (depth/inches) Point Estimates Data series: Partial duration maxima State: ILLINOIS Station: CHICAGO OHARE WSO ARP Lon (dd): -87.9142 Lat (dd): 41.9861 Elev (feet): 66 Date/time: Thu Jan 31 08:44:02 EST 2008 

Freq (yr) 5-min 

10-

min 

15-

min 

30-

min 

60-

min 

120-

min 3-hr 6-hr 12-hr 24-hr 2-day 4-day 7-day 10-day 20-day 

1 0.39 0.6 0.73 0.97 1.19 1.39 1.49 1.78 2.05 2.34 2.7 3.08 3.58 4.05 5.53 2 0.46 0.71 0.87 1.17 1.43 1.68 1.8 2.15 2.47 2.85 3.26 3.7 4.27 4.81 6.54 5 0.54 0.84 1.03 1.41 1.77 2.1 2.27 2.75 3.13 3.64 4.11 4.55 5.16 5.77 7.71 

10 0.61 0.95 1.17 1.62 2.06 2.47 2.68 3.3 3.74 4.29 4.81 5.26 5.88 6.57 8.63 25 0.7 1.08 1.33 1.88 2.44 2.94 3.21 4.05 4.57 5.25 5.83 6.28 6.9 7.69 9.88 50 0.78 1.18 1.46 2.09 2.76 3.35 3.67 4.73 5.32 6.07 6.68 7.13 7.73 8.61 10.85 

100 0.85 1.28 1.59 2.3 3.08 3.77 4.13 5.46 6.11 6.96 7.6 8.05 8.61 9.59 11.85 200 0.93 1.39 1.73 2.52 3.43 4.2 4.63 6.26 6.98 7.93 8.61 9.04 9.54 10.63 12.86 500 1.04 1.53 1.9 2.82 3.9 4.81 5.31 7.42 8.24 9.38 10.08 10.56 10.92 12.12 14.25 

1000 1.13 1.64 2.05 3.08 4.32 5.33 5.91 8.47 9.38 10.62 11.32 11.86 12.19 13.38 15.34 

Precipitation Intensity Estimates (in/hr) 

2 5.47 4.27 3.48 2.33 1.43 0.84 0.6 0.36 0.21 0.12 0.07 0.04 0.03 0.02 0.01 5 6.48 5.03 4.12 2.82 1.77 1.05 0.76 0.46 0.26 0.15 0.09 0.05 0.03 0.02 0.02 

10 7.36 5.68 4.66 3.24 2.06 1.23 0.89 0.55 0.31 0.18 0.1 0.05 0.03 0.03 0.02 25 8.45 6.46 5.32 3.75 2.44 1.47 1.07 0.68 0.38 0.22 0.12 0.07 0.04 0.03 0.02 50 9.36 7.09 5.85 4.18 2.76 1.68 1.22 0.79 0.44 0.25 0.14 0.07 0.05 0.04 0.02 

100 10.24 7.7 6.38 4.61 3.08 1.88 1.38 0.91 0.51 0.29 0.16 0.08 0.05 0.04 0.02 200 11.18 8.35 6.92 5.05 3.43 2.1 1.54 1.04 0.58 0.33 0.18 0.09 0.06 0.04 0.03 500 12.46 9.16 7.62 5.64 3.9 2.4 1.77 1.24 0.68 0.39 0.21 0.11 0.07 0 0 

1000 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 

Date/time: Thu Jan 31 08:47:43 EST 2008 
D-9 

Precipitation frequency estimates (depth/inches) Point Estimates Data series: Partial duration maxima State: NEW MEXICO Station: SANTA FE Lon (dd): 105.9 Lat (dd): 35.6833 Elev (feet): 7582 Date/time: Thu Jan 31 10:56:42 EST 2008 

Freq (yr) 5-min 

10-

min 

15-

min 

30-

min 

60-

min 

120-

min 3-hr 6-hr 12-hr 24-hr 2-day 4-day 7-day 

10-

day 

20-

day 

1 0.2 0.3 0.38 0.51 0.63 0.76 0.82 0.96 1.09 1.24 1.4 1.62 1.92 2.18 2.91 2 0.26 0.39 0.49 0.66 0.81 0.97 1.04 1.2 1.37 1.54 1.75 2.02 2.39 2.71 3.62 5 0.34 0.52 0.65 0.87 1.08 1.28 1.34 1.52 1.71 1.92 2.16 2.5 2.94 3.34 4.41 

10 0.41 0.62 0.77 1.04 1.28 1.52 1.59 1.77 1.98 2.22 2.5 2.88 3.36 3.84 5.01 25 0.5 0.76 0.94 1.26 1.56 1.84 1.93 2.13 2.36 2.62 2.94 3.39 3.92 4.5 5.78 50 0.56 0.86 1.06 1.43 1.77 2.1 2.19 2.4 2.64 2.93 3.29 3.78 4.36 5 6.36 

100 0.64 0.97 1.2 1.62 2 2.38 2.47 2.68 2.94 3.26 3.64 4.18 4.79 5.51 6.91 200 0.71 1.08 1.34 1.8 2.23 2.67 2.77 2.98 3.23 3.58 3.99 4.58 5.22 6.02 7.45 500 0.81 1.23 1.52 2.05 2.54 3.07 3.18 3.38 3.63 4.02 4.46 5.12 5.79 6.69 8.14 

1000 0.89 1.35 1.67 2.25 2.79 3.38 3.51 3.7 3.95 4.35 4.83 5.54 6.21 7.21 8.64 

Precipitation Intensity Estimates (in/hr) 

2 3.1 2.36 1.95 1.31 0.81 0.48 0.35 0.2 0.11 0.06 0.04 0.02 0.01 0.01 0.01 5 4.13 3.14 2.6 1.75 1.08 0.64 0.45 0.25 0.14 0.08 0.05 0.03 0.02 0.01 0.01 

10 4.91 3.73 3.08 2.08 1.28 0.76 0.53 0.3 0.16 0.09 0.05 0.03 0.02 0.02 0.01 25 5.96 4.54 3.75 2.52 1.56 0.92 0.64 0.36 0.2 0.11 0.06 0.04 0.02 0.02 0.01 50 6.76 5.15 4.25 2.86 1.77 1.05 0.73 0.4 0.22 0.12 0.07 0.04 0.03 0.02 0.01 

100 7.64 5.81 4.81 3.24 2 1.19 0.82 0.45 0.24 0.14 0.08 0.04 0.03 0.02 0.01 200 8.51 6.47 5.35 3.6 2.23 1.34 0.92 0.5 0.27 0.15 0.08 0.05 0.03 0.03 0.02 500 9.7 7.38 6.1 4.11 2.54 1.54 1.06 0.56 0.3 0.17 0.09 0.05 0.03 0 0 

1000 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 

Date/time: Thu Jan 31 10:57:41 EST 2008 
D-10 

Precipitation frequency estimates (depth/inches) Point Estimates Data series: Partial duration maxima State: ARIZONA Station: PHOENIX WSFO AP Lon (dd): -111.99 Lat (dd): 33.4431 Elev (feet): 1148 Date/time: Thu Jan 31 11:18:08 EST 2008 

Freq (yr) 5-min 

10-

min 

15-

min 

30-

min 

60-

min 

120-

min 3-hr 6-hr 12-hr 24-hr 2-day 4-day 7-day 

10-

day 

20-

day 

1 0.17 0.27 0.33 0.44 0.55 0.63 0.67 0.81 0.91 1.1 1.21 1.32 1.45 1.58 1.93 2 0.23 0.35 0.43 0.58 0.72 0.81 0.86 1.03 1.16 1.4 1.55 1.68 1.85 2.02 2.48 5 0.31 0.48 0.59 0.79 0.98 1.09 1.14 1.33 1.48 1.81 2.03 2.21 2.43 2.65 3.26 

10 0.38 0.57 0.71 0.96 1.19 1.31 1.36 1.57 1.73 2.14 2.42 2.64 2.9 3.16 3.86 25 0.46 0.7 0.87 1.18 1.46 1.6 1.67 1.9 2.06 2.59 2.96 3.25 3.57 3.88 4.65 50 0.53 0.81 1 1.35 1.67 1.83 1.92 2.16 2.32 2.95 3.38 3.73 4.1 4.45 5.26 

100 0.6 0.91 1.13 1.52 1.88 2.07 2.18 2.43 2.59 3.33 3.83 4.26 4.67 5.05 5.88 200 0.67 1.02 1.26 1.7 2.1 2.3 2.45 2.7 2.85 3.71 4.31 4.81 5.26 5.69 6.51 500 0.76 1.16 1.44 1.94 2.4 2.62 2.83 3.08 3.22 4.24 4.96 5.59 6.11 6.57 7.35 

1000 0.83 1.27 1.57 2.12 2.62 2.87 3.13 3.37 3.5 4.66 5.49 6.22 6.79 7.29 8 

Precipitation Intensity Estimates (in/hr) 

2 2.74 2.08 1.72 1.16 0.72 0.4 0.29 0.17 0.1 0.06 0.03 0.02 0.01 0.01 0.01 5 3.76 2.86 2.36 1.59 0.98 0.55 0.38 0.22 0.12 0.08 0.04 0.02 0.01 0.01 0.01 

10 4.52 3.44 2.85 1.92 1.19 0.66 0.45 0.26 0.14 0.09 0.05 0.03 0.02 0.01 0.01 25 5.56 4.23 3.5 2.35 1.46 0.8 0.56 0.32 0.17 0.11 0.06 0.03 0.02 0.02 0.01 50 6.37 4.85 4.01 2.7 1.67 0.92 0.64 0.36 0.19 0.12 0.07 0.04 0.02 0.02 0.01 

100 7.19 5.47 4.52 3.04 1.88 1.03 0.73 0.41 0.21 0.14 0.08 0.04 0.03 0.02 0.01 200 8.03 6.11 5.05 3.4 2.1 1.15 0.82 0.45 0.24 0.15 0.09 0.05 0.03 0.02 0.01 500 9.14 6.96 5.75 3.87 2.4 1.31 0.94 0.51 0.27 0.18 0.1 0.06 0.04 0 0 

1000 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 

Date/time: Thu Jan 31 11:19:49 EST 2008 
D-11 

Precipitation frequency estimates (depth/inches) Point Estimates Data series: Partial duration maxima State: UTAH Station: SALT LAKE CITY NWSFO Lon (dd): -111.955 Lat (dd): 40.7725 Elev (feet): 4235 Date/time: Thu Jan 31 14:22:26 EST 2008 

Freq (yr) 5-min 

10-

min 

15-

min 

30-

min 

60-

min 

120-

min 3-hr 6-hr 12-hr 24-hr 2-day 4-day 7-day 

10-

day 

20-

day 

1 0.12 0.18 0.23 0.3 0.38 0.5 0.58 0.75 0.94 1.14 1.29 1.5 1.74 1.96 2.56 2 0.15 0.23 0.29 0.39 0.48 0.61 0.71 0.92 1.14 1.4 1.58 1.84 2.13 2.4 3.15 5 0.21 0.32 0.39 0.53 0.65 0.8 0.89 1.1 1.37 1.67 1.89 2.2 2.55 2.86 3.73 

10 0.26 0.39 0.48 0.65 0.81 0.97 1.05 1.27 1.57 1.9 2.15 2.51 2.9 3.23 4.17 25 0.34 0.52 0.65 0.87 1.08 1.25 1.31 1.53 1.88 2.21 2.49 2.94 3.38 3.72 4.74 50 0.42 0.65 0.8 1.08 1.33 1.51 1.55 1.75 2.13 2.45 2.76 3.27 3.75 4.08 5.15 

100 0.52 0.79 0.98 1.32 1.63 1.83 1.84 2 2.41 2.69 3.03 3.61 4.13 4.44 5.54 200 0.63 0.96 1.19 1.6 1.99 2.2 2.21 2.28 2.7 2.95 3.3 3.96 4.51 4.8 5.92 500 0.82 1.24 1.54 2.07 2.57 2.81 2.82 2.88 3.14 3.29 3.66 4.43 5.03 5.26 6.38 

1000 0.99 1.5 1.86 2.51 3.11 3.37 3.38 3.44 3.5 3.54 3.94 4.8 5.42 5.6 6.71 

Precipitation Intensity Estimates (in/hr) 

2 1.81 1.38 1.14 0.77 0.48 0.31 0.24 0.15 0.09 0.06 0.03 0.02 0.01 0.01 0.01 5 2.48 1.89 1.56 1.05 0.65 0.4 0.3 0.18 0.11 0.07 0.04 0.02 0.02 0.01 0.01 

10 3.08 2.35 1.94 1.31 0.81 0.48 0.35 0.21 0.13 0.08 0.04 0.03 0.02 0.01 0.01 25 4.12 3.13 2.59 1.74 1.08 0.63 0.44 0.26 0.16 0.09 0.05 0.03 0.02 0.02 0.01 50 5.09 3.87 3.2 2.15 1.33 0.76 0.52 0.29 0.18 0.1 0.06 0.03 0.02 0.02 0.01 

100 6.22 4.73 3.91 2.63 1.63 0.91 0.61 0.33 0.2 0.11 0.06 0.04 0.02 0.02 0.01 200 7.57 5.77 4.76 3.21 1.99 1.1 0.74 0.38 0.22 0.12 0.07 0.04 0.03 0.02 0.01 500 9.79 7.45 6.16 4.15 2.57 1.41 0.94 0.48 0.26 0.14 0.08 0.05 0.03 0 0 

1000 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 

Date/time: Thu Jan 31 14:23:39 EST 2008 
D-12 

Precipitation frequency estimates (depth/inches) Point Estimates Data series: Partial duration maxima State: NEVADA Station: LAS VEGAS WSO AIRPORT Lon (dd): -115.167 Lat (dd): 36.0833 Elev (feet): 2152 Date/time: Thu Jan 31 14:25:16 EST 2008 

Freq (yr) 5-min 

10-

min 

15-

min 

30-

min 

60-

min 

120-

min 3-hr 6-hr 12-hr 24-hr 2-day 4-day 7-day 

10-

day 

20-

day 

1 0.12 0.17 0.22 0.29 0.36 0.45 0.5 0.61 0.7 0.77 0.8 0.88 0.96 1.04 1.18 2 0.15 0.23 0.29 0.39 0.48 0.59 0.65 0.79 0.92 1 1.05 1.16 1.27 1.37 1.58 5 0.22 0.33 0.41 0.55 0.68 0.82 0.89 1.07 1.25 1.37 1.42 1.58 1.73 1.86 2.18 

10 0.27 0.41 0.51 0.69 0.85 1 1.07 1.29 1.48 1.62 1.68 1.87 2.04 2.19 2.58 25 0.35 0.53 0.66 0.88 1.09 1.26 1.34 1.58 1.8 1.96 2.02 2.24 2.43 2.59 3.07 50 0.41 0.62 0.77 1.04 1.29 1.48 1.54 1.82 2.03 2.2 2.27 2.52 2.71 2.88 3.42 

100 0.48 0.73 0.91 1.23 1.52 1.72 1.77 2.07 2.27 2.46 2.51 2.78 2.97 3.15 3.76 200 0.56 0.85 1.05 1.42 1.76 1.98 2.01 2.33 2.5 2.7 2.75 3.04 3.22 3.4 4.09 500 0.67 1.02 1.27 1.71 2.12 2.36 2.39 2.69 2.83 3.03 3.05 3.38 3.55 3.73 4.49 

1000 0.77 1.17 1.45 1.96 2.42 2.67 2.69 3 3.07 3.27 3.28 3.63 3.79 3.97 4.77 

Precipitation Intensity Estimates (in/hr) 

2 1.82 1.39 1.15 0.77 0.48 0.29 0.22 0.13 0.08 0.04 0.02 0.01 0.01 0.01 0 5 2.59 1.97 1.63 1.1 0.68 0.41 0.3 0.18 0.1 0.06 0.03 0.02 0.01 0.01 0 

10 3.24 2.47 2.04 1.37 0.85 0.5 0.36 0.22 0.12 0.07 0.04 0.02 0.01 0.01 0.01 25 4.16 3.17 2.62 1.76 1.09 0.63 0.45 0.26 0.15 0.08 0.04 0.02 0.01 0.01 0.01 50 4.91 3.74 3.09 2.08 1.29 0.74 0.51 0.3 0.17 0.09 0.05 0.03 0.02 0.01 0.01 

100 5.78 4.4 3.64 2.45 1.52 0.86 0.59 0.35 0.19 0.1 0.05 0.03 0.02 0.01 0.01 200 6.7 5.1 4.22 2.84 1.76 0.99 0.67 0.39 0.21 0.11 0.06 0.03 0.02 0.01 0.01 500 8.08 6.14 5.08 3.42 2.12 1.18 0.8 0.45 0.23 0.13 0.06 0.04 0.02 0 0 

1000 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 

Date/time: Thu Jan 31 14:33:29 EST 2008 
D-13 

Precipitation frequency estimates (depth/inches) Point Estimates Data series: Partial duration maxima State: INDIANA Station: INDIANAPOLIS WSFO AP Lon (dd): -86.2789 Lat (dd): 39.7317 Elev (feet): 780 Date/time: Thu Jan 31 14:35:02 EST 2008 

Freq (yr) 5-min 

10-

min 

15-

min 

30-

min 

60-

min 

120-

min 3-hr 6-hr 12-hr 24-hr 2-day 4-day 7-day 

10-

day 

20-

day 

1 0.38 0.6 0.73 0.97 1.18 1.39 1.47 1.74 2.07 2.46 2.87 3.26 3.85 4.39 5.99 2 0.46 0.71 0.87 1.17 1.43 1.68 1.78 2.11 2.49 2.95 3.43 3.89 4.58 5.21 7.09 5 0.55 0.85 1.04 1.43 1.79 2.11 2.24 2.67 3.1 3.62 4.19 4.69 5.49 6.23 8.36 

10 0.62 0.95 1.17 1.63 2.07 2.45 2.61 3.12 3.6 4.13 4.76 5.31 6.22 7.03 9.35 25 0.71 1.08 1.34 1.89 2.46 2.94 3.14 3.77 4.29 4.83 5.54 6.15 7.2 8.12 10.65 50 0.78 1.19 1.47 2.1 2.76 3.33 3.58 4.31 4.86 5.38 6.15 6.81 7.98 8.98 11.66 

100 0.85 1.28 1.59 2.3 3.08 3.75 4.05 4.89 5.46 5.94 6.76 7.47 8.76 9.84 12.66 200 0.93 1.38 1.72 2.51 3.4 4.19 4.55 5.51 6.08 6.5 7.39 8.13 9.56 10.72 13.65 500 1.02 1.5 1.88 2.78 3.85 4.81 5.26 6.41 6.97 7.27 8.22 9.02 10.63 11.89 14.95 

1000 1.1 1.6 2 2.99 4.2 5.31 5.84 7.15 7.68 7.86 8.86 9.71 11.46 12.8 15.94 

Precipitation Intensity Estimates (in/hr) 

2 5.48 4.28 3.49 2.33 1.43 0.84 0.59 0.35 0.21 0.12 0.07 0.04 0.03 0.02 0.01 5 6.56 5.1 4.18 2.86 1.79 1.05 0.75 0.45 0.26 0.15 0.09 0.05 0.03 0.03 0.02 

10 7.42 5.72 4.69 3.26 2.07 1.23 0.87 0.52 0.3 0.17 0.1 0.06 0.04 0.03 0.02 25 8.51 6.51 5.36 3.79 2.46 1.47 1.05 0.63 0.36 0.2 0.12 0.06 0.04 0.03 0.02 50 9.38 7.11 5.87 4.19 2.76 1.67 1.19 0.72 0.4 0.22 0.13 0.07 0.05 0.04 0.02 

100 10.22 7.7 6.38 4.6 3.08 1.88 1.35 0.82 0.45 0.25 0.14 0.08 0.05 0.04 0.03 200 11.1 8.29 6.87 5.01 3.4 2.1 1.51 0.92 0.5 0.27 0.15 0.08 0.06 0.04 0.03 500 12.29 9.03 7.51 5.57 3.85 2.41 1.75 1.07 0.58 0.3 0.17 0.09 0.06 0 0 

1000 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 

Date/time: Thu Jan 31 14:36:24 EST 2008 
D-14 

Precipitation frequency estimates (depth/inches) Point Estimates Data series: Partial duration maxima State: OHIO Station: COLUMBUS WSO AIRPORT Lon (dd): -82.8808 Lat (dd): 39.9914 Elev (feet): 820 Date/time: Thu Jan 31 13:06:58 EST 2008 

Freq (yr) 5-min 

10-

min 

15-

min 

30-

min 

60-

min 

120-

min 3-hr 6-hr 12-hr 24-hr 2-day 4-day 7-day 

10-

day 

20-

day 

1 0.35 0.55 0.67 0.89 1.09 1.27 1.35 1.61 1.89 2.19 2.53 2.9 3.48 3.97 5.52 2 0.42 0.66 0.8 1.07 1.32 1.54 1.63 1.94 2.26 2.62 3.03 3.45 4.14 4.71 6.51 5 0.5 0.78 0.96 1.32 1.65 1.93 2.04 2.41 2.8 3.23 3.7 4.19 5.01 5.63 7.65 

10 0.57 0.88 1.08 1.5 1.91 2.24 2.37 2.8 3.25 3.73 4.25 4.79 5.7 6.37 8.54 25 0.65 1 1.23 1.74 2.25 2.67 2.84 3.36 3.9 4.44 5.03 5.62 6.68 7.38 9.71 50 0.71 1.08 1.34 1.92 2.53 3.02 3.21 3.83 4.44 5.03 5.66 6.29 7.46 8.18 10.62 

100 0.78 1.17 1.46 2.1 2.81 3.39 3.61 4.33 5.03 5.64 6.33 6.98 8.27 8.99 11.51 200 0.84 1.26 1.56 2.28 3.1 3.77 4.03 4.86 5.65 6.3 7.02 7.7 9.11 9.83 12.4 500 0.93 1.36 1.7 2.52 3.48 4.3 4.62 5.62 6.55 7.23 8 8.68 10.28 10.96 13.56 

1000 0.99 1.44 1.8 2.7 3.79 4.73 5.09 6.25 7.29 7.98 8.78 9.46 11.2 11.85 14.41 

Precipitation Intensity Estimates (in/hr) 

2 5.05 3.94 3.21 2.15 1.32 0.77 0.54 0.32 0.19 0.11 0.06 0.04 0.02 0.02 0.01 5 6.05 4.7 3.85 2.63 1.65 0.96 0.68 0.4 0.23 0.13 0.08 0.04 0.03 0.02 0.02 

10 6.83 5.27 4.32 3 1.91 1.12 0.79 0.47 0.27 0.16 0.09 0.05 0.03 0.03 0.02 25 7.82 5.98 4.92 3.48 2.25 1.34 0.94 0.56 0.32 0.19 0.1 0.06 0.04 0.03 0.02 50 8.58 6.51 5.37 3.84 2.53 1.51 1.07 0.64 0.37 0.21 0.12 0.07 0.04 0.03 0.02 

100 9.34 7.03 5.82 4.2 2.81 1.69 1.2 0.72 0.42 0.24 0.13 0.07 0.05 0.04 0.02 200 10.1 7.54 6.25 4.56 3.1 1.88 1.34 0.81 0.47 0.26 0.15 0.08 0.05 0.04 0.03 500 11.12 8.18 6.8 5.04 3.48 2.15 1.54 0.94 0.54 0.3 0.17 0.09 0.06 0.05 0 

1000 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 

Date/time: Thu Jan 31 13:07:44 EST 2008 
D-15 

Precipitation frequency estimates (depth/inches) Point Estimates Data series: Partial duration maxima State: PENNSYLVANIA Station: PHILADELPHIA WSO AP Lon (dd): -75.2311 Lat (dd): 39.8683 Elev (feet): 6 Date/time: Thu Jan 31 14:50:28 EST 2008 

Freq (yr) 5-min 

10-

min 

15-

min 

30-

min 

60-

min 

120-

min 3-hr 6-hr 12-hr 24-hr 2-day 4-day 7-day 

10-

day 

20-

day 

1 0.35 0.56 0.69 0.95 1.19 1.43 1.56 1.93 2.34 2.68 3.07 3.44 3.98 4.46 6.01 2 0.41 0.66 0.83 1.15 1.44 1.73 1.89 2.33 2.82 3.23 3.71 4.15 4.78 5.34 7.13 5 0.49 0.78 0.98 1.4 1.79 2.17 2.37 2.91 3.54 4.08 4.7 5.22 5.94 6.54 8.53 

10 0.54 0.86 1.08 1.57 2.05 2.49 2.73 3.38 4.13 4.8 5.51 6.1 6.89 7.5 9.63 25 0.6 0.95 1.21 1.79 2.38 2.93 3.22 4.03 5.01 5.85 6.68 7.36 8.27 8.87 11.14 50 0.64 1.02 1.29 1.94 2.63 3.26 3.61 4.56 5.75 6.74 7.66 8.4 9.42 9.97 12.32 

100 0.68 1.08 1.37 2.09 2.88 3.6 4.01 5.11 6.55 7.7 8.71 9.52 10.64 11.12 13.52 200 0.72 1.14 1.43 2.23 3.13 3.93 4.4 5.69 7.42 8.76 9.85 10.72 11.95 12.32 14.74 500 0.76 1.2 1.51 2.4 3.44 4.38 4.94 6.51 8.68 10.3 11.48 12.45 13.82 14.05 16.38 

1000 0.79 1.24 1.56 2.52 3.68 4.72 5.36 7.16 9.73 11.6 12.84 13.87 15.36 15.48 17.64 

Precipitation Intensity Estimates (in/hr) 

2 4.97 3.97 3.32 2.3 1.44 0.87 0.63 0.39 0.23 0.13 0.08 0.04 0.03 0.02 0.01 5 5.83 4.67 3.94 2.8 1.79 1.08 0.79 0.49 0.29 0.17 0.1 0.05 0.04 0.03 0.02 

10 6.43 5.15 4.34 3.14 2.05 1.25 0.91 0.56 0.34 0.2 0.11 0.06 0.04 0.03 0.02 25 7.18 5.72 4.83 3.58 2.38 1.46 1.07 0.67 0.42 0.24 0.14 0.08 0.05 0.04 0.02 50 7.68 6.11 5.16 3.89 2.63 1.63 1.2 0.76 0.48 0.28 0.16 0.09 0.06 0.04 0.03 

100 8.17 6.49 5.47 4.19 2.88 1.8 1.33 0.85 0.54 0.32 0.18 0.1 0.06 0.05 0.03 200 8.59 6.81 5.73 4.46 3.13 1.97 1.47 0.95 0.62 0.36 0.21 0.11 0.07 0.05 0.03 500 9.08 7.19 6.03 4.8 3.44 2.19 1.65 1.09 0.72 0.43 0.24 0.13 0.08 0 0 

1000 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 

Date/time: Thu Jan 31 14:51:05 EST 2008 
D-16 

Precipitation frequency estimates (depth/inches) Point Estimates Data series: Partial duration maxima State: KENTUCKY Station: FRANKFORT LOCK 4 Lon (dd): -84.8817 Lat (dd): 38.235 Elev (feet): 600 Date/time: Thu Jan 31 14:52:10 EST 2008 

Freq (yr) 5-min 

10-

min 

15-

min 

30-

min 

60-

min 

120-

min 3-hr 6-hr 12-hr 24-hr 2-day 4-day 7-day 

10-

day 

20-

day 

1 0.38 0.59 0.72 0.96 1.17 1.37 1.47 1.8 2.12 2.51 2.96 3.34 3.98 4.48 6.17 2 0.45 0.7 0.86 1.15 1.41 1.65 1.77 2.16 2.54 3 3.55 4 4.73 5.34 7.31 5 0.52 0.82 1.01 1.38 1.74 2.04 2.19 2.67 3.13 3.73 4.38 4.89 5.76 6.48 8.7 

10 0.59 0.91 1.12 1.57 2 2.36 2.54 3.09 3.62 4.34 5.06 5.62 6.61 7.42 9.81 25 0.67 1.03 1.27 1.8 2.35 2.8 3.03 3.7 4.32 5.23 6.04 6.63 7.82 8.76 11.31 50 0.73 1.11 1.38 1.98 2.62 3.15 3.43 4.2 4.89 5.98 6.84 7.44 8.82 9.86 12.49 

100 0.79 1.2 1.49 2.16 2.9 3.53 3.86 4.74 5.5 6.79 7.69 8.29 9.88 11 13.69 200 0.85 1.28 1.59 2.34 3.19 3.92 4.31 5.31 6.16 7.67 8.6 9.17 11 12.22 14.9 500 0.94 1.38 1.73 2.58 3.59 4.47 4.96 6.14 7.09 8.95 9.89 10.39 12.59 13.92 16.53 

1000 1 1.46 1.83 2.76 3.9 4.92 5.49 6.82 7.86 10.01 10.95 11.35 13.87 15.29 17.79 

Precipitation Intensity Estimates (in/hr) 

2 5.35 4.19 3.42 2.3 1.41 0.82 0.59 0.36 0.21 0.13 0.07 0.04 0.03 0.02 0.02 5 6.29 4.91 4.02 2.77 1.74 1.02 0.73 0.45 0.26 0.16 0.09 0.05 0.03 0.03 0.02 

10 7.06 5.47 4.5 3.14 2 1.18 0.84 0.52 0.3 0.18 0.11 0.06 0.04 0.03 0.02 25 8.02 6.16 5.08 3.61 2.35 1.4 1.01 0.62 0.36 0.22 0.13 0.07 0.05 0.04 0.02 50 8.77 6.68 5.52 3.97 2.62 1.58 1.14 0.7 0.41 0.25 0.14 0.08 0.05 0.04 0.03 

100 9.49 7.18 5.95 4.33 2.9 1.76 1.28 0.79 0.46 0.28 0.16 0.09 0.06 0.05 0.03 200 10.21 7.67 6.38 4.68 3.19 1.96 1.44 0.89 0.51 0.32 0.18 0.1 0.07 0.05 0.03 500 11.23 8.3 6.93 5.16 3.59 2.24 1.65 1.03 0.59 0.37 0.21 0.11 0.07 0 0 

1000 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 

Date/time: Thu Jan 31 14:52:44 EST 2008 
D-17 

Precipitation frequency estimates (depth/inches) Point Estimates Data series: Partial duration maxima State: WEST VIRGINIA Station: CHARLESTON WSFO AP Lon (dd): -81.5914 Lat (dd): 38.3794 Elev (feet): 744 Date/time: Thu Jan 31 14:53:54 EST 2008 

Freq (yr) 5-min 

10-

min 

15-

min 

30-

min 

60-

min 

120-

min 3-hr 6-hr 12-hr 24-hr 2-day 4-day 7-day 

10-

day 

20-

day 

1 0.34 0.53 0.65 0.85 1.04 1.21 1.27 1.5 1.77 2.16 2.58 2.99 3.6 4.15 5.8 2 0.4 0.63 0.77 1.03 1.26 1.46 1.53 1.8 2.11 2.56 3.06 3.54 4.25 4.89 6.79 5 0.48 0.75 0.92 1.26 1.58 1.82 1.91 2.22 2.58 3.1 3.66 4.21 4.97 5.67 7.77 

10 0.54 0.83 1.03 1.43 1.81 2.1 2.2 2.56 2.96 3.55 4.15 4.73 5.54 6.27 8.5 25 0.62 0.94 1.17 1.65 2.13 2.48 2.61 3.03 3.5 4.16 4.82 5.44 6.27 7.03 9.42 50 0.67 1.02 1.26 1.8 2.38 2.78 2.93 3.41 3.95 4.65 5.35 5.98 6.82 7.61 10.09 

100 0.72 1.09 1.36 1.96 2.62 3.08 3.26 3.81 4.41 5.17 5.89 6.53 7.37 8.15 10.71 200 0.78 1.16 1.44 2.11 2.86 3.38 3.59 4.22 4.89 5.7 6.45 7.08 7.9 8.68 11.3 500 0.84 1.24 1.55 2.29 3.17 3.8 4.05 4.78 5.57 6.44 7.21 7.8 8.58 9.34 12.02 

1000 0.89 1.3 1.62 2.43 3.42 4.12 4.41 5.23 6.11 7.02 7.79 8.36 9.08 9.83 12.52 

Precipitation Intensity Estimates (in/hr) 

2 4.82 3.77 3.07 2.06 1.26 0.73 0.51 0.3 0.18 0.11 0.06 0.04 0.03 0.02 0.01 5 5.78 4.49 3.68 2.52 1.58 0.91 0.64 0.37 0.21 0.13 0.08 0.04 0.03 0.02 0.02 

10 6.49 5.01 4.11 2.85 1.81 1.05 0.73 0.43 0.25 0.15 0.09 0.05 0.03 0.03 0.02 25 7.39 5.66 4.66 3.29 2.13 1.24 0.87 0.51 0.29 0.17 0.1 0.06 0.04 0.03 0.02 50 8.08 6.12 5.05 3.61 2.38 1.39 0.98 0.57 0.33 0.19 0.11 0.06 0.04 0.03 0.02 

100 8.7 6.55 5.42 3.92 2.62 1.54 1.08 0.64 0.37 0.22 0.12 0.07 0.04 0.03 0.02 200 9.34 6.97 5.78 4.21 2.86 1.69 1.2 0.7 0.41 0.24 0.13 0.07 0.05 0.04 0.02 500 10.13 7.45 6.19 4.59 3.17 1.9 1.35 0.8 0.46 0.27 0.15 0.08 0.05 0 0 

1000 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 

Date/time: Thu Jan 31 14:54:26 EST 2008 
D-18 

Precipitation frequency estimates (depth/inches) Point Estimates Data series: Partial duration maxima State: VIRGINIA Station: WASHINGTON REAGAN AP Lon (dd): -77.0342 Lat (dd): 38.865 Elev (feet): 22 Date/time: Tue Feb 5 10:31:30 EST 2008 

Freq (yr) 5-min 

10-

min 

15-

min 

30-

min 

60-

min 

120-

min 3-hr 6-hr 12-hr 24-hr 2-day 4-day 7-day 

10-

day 

20-

day 

1 0.36 0.57 0.71 0.97 1.21 1.41 1.5 1.84 2.22 2.57 2.99 3.33 3.85 4.41 5.95 2 0.43 0.68 0.86 1.18 1.49 1.71 1.83 2.23 2.67 3.11 3.62 4.02 4.64 5.29 7.07 5 0.51 0.81 1.03 1.46 1.87 2.17 2.32 2.81 3.4 4 4.64 5.14 5.86 6.61 8.55 

10 0.57 0.91 1.15 1.66 2.16 2.52 2.71 3.29 4.02 4.78 5.51 6.1 6.91 7.71 9.74 25 0.64 1.02 1.3 1.92 2.56 3.02 3.26 4 4.97 5.98 6.83 7.55 8.48 9.31 11.41 50 0.7 1.11 1.41 2.12 2.87 3.43 3.72 4.61 5.8 7.04 7.98 8.8 9.83 10.65 12.76 

100 0.75 1.2 1.51 2.31 3.19 3.85 4.21 5.26 6.72 8.24 9.25 10.2 11.32 12.11 14.16 200 0.81 1.28 1.61 2.51 3.52 4.3 4.72 5.97 7.75 9.61 10.68 11.75 12.96 13.67 15.61 500 0.87 1.38 1.74 2.77 3.97 4.93 5.45 7.01 9.32 11.71 12.83 14.08 15.42 15.98 17.63 

1000 0.93 1.46 1.83 2.97 4.33 5.44 6.06 7.89 10.67 13.55 14.68 16.08 17.51 17.89 19.22 

Precipitation Intensity Estimates (in/hr) 

2 5.11 4.09 3.43 2.37 1.49 0.86 0.61 0.37 0.22 0.13 0.08 0.04 0.03 0.02 0.01 5 6.08 4.87 4.11 2.92 1.87 1.08 0.77 0.47 0.28 0.17 0.1 0.05 0.03 0.03 0.02 

10 6.79 5.43 4.58 3.32 2.16 1.26 0.9 0.55 0.33 0.2 0.11 0.06 0.04 0.03 0.02 25 7.7 6.13 5.18 3.84 2.56 1.51 1.09 0.67 0.41 0.25 0.14 0.08 0.05 0.04 0.02 50 8.36 6.67 5.62 4.24 2.87 1.71 1.24 0.77 0.48 0.29 0.17 0.09 0.06 0.04 0.03 

100 9.04 7.18 6.05 4.63 3.19 1.93 1.4 0.88 0.56 0.34 0.19 0.11 0.07 0.05 0.03 200 9.67 7.66 6.45 5.02 3.52 2.15 1.57 1 0.64 0.4 0.22 0.12 0.08 0.06 0.03 500 10.49 8.29 6.96 5.54 3.97 2.46 1.82 1.17 0.77 0.49 0.27 0.15 0.09 0 0 

1000 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 

Date/time: Tue Feb 5 10:32:29 EST 2008 
D-19 

Precipitation frequency estimates (depth/inches) Point Estimates Data series: Partial duration maxima State: MARYLAND Station: BALTIMORE WSO ARPT Lon (dd): -76.6839 Lat (dd): 39.1722 Elev (feet): 147 Date/time: Thu Jan 31 14:47:48 EST 2008 

Freq (yr) 5-min 

10-

min 

15-

min 

30-

min 

60-

min 

120-

min 3-hr 6-hr 12-hr 24-hr 2-day 4-day 7-day 

10-

day 

20-

day 

1 0.34 0.55 0.69 0.94 1.17 1.4 1.51 1.86 2.25 2.61 3.03 3.35 3.89 4.43 5.99 2 0.41 0.66 0.83 1.14 1.43 1.7 1.83 2.25 2.72 3.16 3.66 4.05 4.68 5.33 7.12 5 0.49 0.78 0.99 1.41 1.8 2.16 2.33 2.84 3.46 4.06 4.7 5.18 5.92 6.65 8.61 

10 0.55 0.87 1.1 1.6 2.08 2.51 2.71 3.32 4.09 4.85 5.59 6.15 6.98 7.75 9.81 25 0.62 0.98 1.25 1.85 2.46 3 3.27 4.04 5.06 6.08 6.92 7.61 8.56 9.36 11.5 50 0.67 1.07 1.35 2.03 2.76 3.4 3.72 4.66 5.91 7.16 8.09 8.87 9.92 10.71 12.86 

100 0.72 1.15 1.45 2.22 3.06 3.82 4.2 5.32 6.86 8.38 9.39 10.27 11.42 12.16 14.26 200 0.77 1.22 1.54 2.4 3.37 4.25 4.71 6.04 7.92 9.76 10.84 11.84 13.08 13.73 15.73 500 0.83 1.32 1.66 2.64 3.79 4.87 5.45 7.09 9.53 11.89 13.02 14.19 15.55 16.01 17.76 

1000 0.88 1.39 1.74 2.82 4.11 5.37 6.04 7.98 10.93 13.76 14.9 16.2 17.66 17.93 19.36 

Precipitation Intensity Estimates (in/hr) 

2 4.93 3.94 3.3 2.28 1.43 0.85 0.61 0.38 0.23 0.13 0.08 0.04 0.03 0.02 0.01 5 5.87 4.7 3.96 2.82 1.8 1.08 0.78 0.47 0.29 0.17 0.1 0.05 0.04 0.03 0.02 

10 6.55 5.24 4.42 3.2 2.08 1.25 0.9 0.55 0.34 0.2 0.12 0.06 0.04 0.03 0.02 25 7.4 5.9 4.99 3.69 2.46 1.5 1.09 0.68 0.42 0.25 0.14 0.08 0.05 0.04 0.02 50 8.04 6.4 5.4 4.07 2.76 1.7 1.24 0.78 0.49 0.3 0.17 0.09 0.06 0.04 0.03 

100 8.66 6.88 5.8 4.44 3.06 1.91 1.4 0.89 0.57 0.35 0.2 0.11 0.07 0.05 0.03 200 9.25 7.33 6.17 4.8 3.37 2.13 1.57 1.01 0.66 0.41 0.23 0.12 0.08 0.06 0.03 500 10 7.9 6.63 5.28 3.79 2.44 1.81 1.18 0.79 0.5 0.27 0.15 0.09 0 0 

1000 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 

Date/time: Thu Jan 31 14:48:21 EST 2008 
D-20 

Precipitation frequency estimates (depth/inches) Point Estimates Data series: Partial duration maxima State: DELAWARE Station: DOVER Lon (dd): -75.5167 Lat (dd): 39.2583 Elev (feet): 0 Date/time: Thu Jan 31 14:45:28 EST 2008 

Freq (yr) 5-min 

10-

min 

15-

min 

30-

min 

60-

min 

120-

min 3-hr 6-hr 12-hr 24-hr 2-day 4-day 7-day 

10-

day 

20-

day 

1 0.35 0.56 0.7 0.96 1.2 1.46 1.58 1.95 2.36 2.68 3.09 3.42 3.98 4.48 6.05 2 0.42 0.67 0.84 1.16 1.46 1.76 1.92 2.35 2.83 3.26 3.76 4.16 4.8 5.38 7.2 5 0.49 0.78 0.99 1.41 1.8 2.2 2.39 2.92 3.54 4.24 4.89 5.35 6.08 6.71 8.71 

10 0.55 0.88 1.11 1.61 2.09 2.57 2.81 3.44 4.21 5.08 5.85 6.37 7.17 7.8 9.93 25 0.62 0.98 1.25 1.85 2.46 3.05 3.35 4.14 5.15 6.36 7.32 7.88 8.77 9.38 11.63 50 0.67 1.07 1.35 2.04 2.76 3.44 3.81 4.75 6 7.49 8.59 9.18 10.14 10.71 13 

100 0.72 1.15 1.45 2.22 3.05 3.84 4.27 5.39 6.91 8.75 10.01 10.62 11.64 12.12 14.43 200 0.77 1.21 1.53 2.38 3.35 4.25 4.76 6.08 7.92 10.19 11.62 12.23 13.29 13.73 15.9 500 0.82 1.3 1.64 2.6 3.73 4.79 5.42 7.04 9.38 12.37 14.04 14.63 15.74 16.12 17.96 

1000 0.87 1.37 1.72 2.78 4.05 5.25 5.98 7.88 10.71 14.27 16.15 16.69 17.81 18.17 19.6 

Precipitation Intensity Estimates (in/hr) 

2 5.02 4.01 3.36 2.32 1.46 0.88 0.64 0.39 0.23 0.14 0.08 0.04 0.03 0.02 0.01 5 5.87 4.7 3.96 2.82 1.8 1.1 0.8 0.49 0.29 0.18 0.1 0.06 0.04 0.03 0.02 

10 6.59 5.26 4.44 3.22 2.09 1.29 0.93 0.57 0.35 0.21 0.12 0.07 0.04 0.03 0.02 25 7.4 5.9 4.99 3.69 2.46 1.52 1.11 0.69 0.43 0.27 0.15 0.08 0.05 0.04 0.02 50 8.04 6.4 5.4 4.07 2.76 1.72 1.27 0.79 0.5 0.31 0.18 0.1 0.06 0.04 0.03 

100 8.65 6.87 5.79 4.43 3.05 1.92 1.42 0.9 0.57 0.36 0.21 0.11 0.07 0.05 0.03 200 9.19 7.28 6.13 4.77 3.35 2.12 1.58 1.02 0.66 0.42 0.24 0.13 0.08 0.06 0.03 500 9.85 7.79 6.54 5.2 3.73 2.4 1.8 1.18 0.78 0.52 0.29 0.15 0.09 0.06 0 

1000 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 

Date/time: Thu Jan 31 14:46:04 EST 2008 
D-21 

Precipitation frequency estimates (depth/inches) Point Estimates Data series: Partial duration maxima State: NEW JERSEY Station: HIGHTSTOWN 2 W Lon (dd): -74.5642 Lat (dd): 40.265 Elev (feet): 98 Date/time: Thu Jan 31 14:43:06 EST 2008 

Freq (yr) 5-min 

10-

min 

15-

min 

30-

min 

60-

min 

120-

min 3-hr 6-hr 12-hr 24-hr 2-day 4-day 7-day 

10-

day 

20-

day 

1 0.34 0.54 0.68 0.93 1.16 1.41 1.55 1.97 2.39 2.73 3.16 3.55 4.16 4.73 6.4 2 0.41 0.65 0.81 1.12 1.41 1.72 1.89 2.39 2.89 3.31 3.84 4.3 5 5.67 7.61 5 0.48 0.77 0.97 1.38 1.77 2.18 2.41 3.03 3.68 4.26 4.94 5.46 6.26 6.99 9.13 

10 0.54 0.86 1.09 1.57 2.05 2.54 2.8 3.55 4.36 5.07 5.87 6.44 7.31 8.06 10.35 25 0.61 0.96 1.22 1.81 2.41 3.03 3.36 4.3 5.37 6.3 7.25 7.86 8.83 9.6 12.02 50 0.66 1.04 1.32 1.99 2.7 3.42 3.82 4.93 6.24 7.37 8.44 9.06 10.12 10.87 13.34 

100 0.71 1.12 1.42 2.17 2.99 3.83 4.3 5.6 7.2 8.57 9.75 10.37 11.5 12.21 14.69 200 0.75 1.19 1.51 2.35 3.29 4.25 4.79 6.33 8.26 9.9 11.2 11.79 12.99 13.63 16.07 500 0.81 1.28 1.62 2.57 3.69 4.84 5.49 7.38 9.86 11.93 13.38 13.88 15.18 15.66 17.96 

1000 0.86 1.35 1.69 2.74 4 5.31 6.05 8.26 11.22 13.69 15.24 15.65 17 17.39 19.43 

Precipitation Intensity Estimates (in/hr) 

2 4.86 3.89 3.26 2.25 1.41 0.86 0.63 0.4 0.24 0.14 0.08 0.04 0.03 0.02 0.02 5 5.77 4.62 3.9 2.77 1.77 1.09 0.8 0.51 0.31 0.18 0.1 0.06 0.04 0.03 0.02 

10 6.44 5.15 4.34 3.15 2.05 1.27 0.93 0.59 0.36 0.21 0.12 0.07 0.04 0.03 0.02 25 7.27 5.79 4.89 3.62 2.41 1.51 1.12 0.72 0.45 0.26 0.15 0.08 0.05 0.04 0.03 50 7.87 6.27 5.29 3.98 2.7 1.71 1.27 0.82 0.52 0.31 0.18 0.09 0.06 0.05 0.03 

100 8.47 6.73 5.67 4.34 2.99 1.92 1.43 0.94 0.6 0.36 0.2 0.11 0.07 0.05 0.03 200 9.04 7.16 6.02 4.69 3.29 2.13 1.6 1.06 0.69 0.41 0.23 0.12 0.08 0.06 0.03 500 9.74 7.7 6.46 5.14 3.69 2.42 1.83 1.23 0.82 0.5 0.28 0.14 0.09 0 0 

1000 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 

Date/time: Thu Jan 31 14:43:54 EST 2008 
D-22 

Precipitation frequency estimates (depth/inches) Point Estimates Data series: Partial duration maxima State: TENNESSEE Station: NASHVILLE WSO AIRPORT Lon (dd): -86.6764 Lat (dd): 36.1253 Elev (feet): 498 Date/time: Thu Jan 31 14:41:00 EST 2008 

Freq (yr) 5-min 

10-

min 

15-

min 

30-

min 

60-

min 

120-

min 3-hr 6-hr 12-hr 24-hr 2-day 4-day 7-day 

10-

day 

20-

day 

1 0.38 0.61 0.76 1.04 1.3 1.54 1.67 2 2.37 2.83 3.37 3.76 4.56 5.24 7.08 2 0.45 0.71 0.9 1.24 1.55 1.83 1.99 2.38 2.82 3.37 4.03 4.48 5.44 6.24 8.39 5 0.51 0.82 1.04 1.48 1.9 2.23 2.41 2.88 3.42 4.11 4.92 5.45 6.62 7.51 9.9 

10 0.57 0.91 1.15 1.67 2.17 2.54 2.76 3.31 3.92 4.7 5.65 6.23 7.58 8.53 11.05 25 0.64 1.01 1.28 1.9 2.54 2.97 3.23 3.9 4.62 5.53 6.69 7.29 8.93 9.91 12.56 50 0.69 1.09 1.39 2.09 2.83 3.31 3.61 4.38 5.19 6.2 7.53 8.15 10.01 11.01 13.7 

100 0.74 1.17 1.48 2.27 3.12 3.67 4.01 4.88 5.79 6.89 8.41 9.04 11.15 12.13 14.82 200 0.78 1.24 1.57 2.44 3.42 4.03 4.41 5.41 6.41 7.61 9.34 9.94 12.34 13.26 15.91 500 0.84 1.33 1.68 2.67 3.83 4.52 4.97 6.15 7.28 8.6 10.63 11.17 13.99 14.8 17.31 

1000 0.89 1.4 1.75 2.84 4.15 4.91 5.41 6.73 7.96 9.37 11.65 12.14 15.31 15.99 18.35 

Precipitation Intensity Estimates (in/hr) 

2 5.35 4.28 3.59 2.48 1.55 0.91 0.66 0.4 0.23 0.14 0.08 0.05 0.03 0.03 0.02 5 6.17 4.94 4.16 2.96 1.9 1.11 0.8 0.48 0.28 0.17 0.1 0.06 0.04 0.03 0.02 

10 6.82 5.45 4.6 3.33 2.17 1.27 0.92 0.55 0.33 0.2 0.12 0.06 0.05 0.04 0.02 25 7.63 6.08 5.14 3.81 2.54 1.48 1.08 0.65 0.38 0.23 0.14 0.08 0.05 0.04 0.03 50 8.24 6.56 5.54 4.17 2.83 1.66 1.2 0.73 0.43 0.26 0.16 0.08 0.06 0.05 0.03 

100 8.83 7.02 5.92 4.53 3.12 1.83 1.33 0.82 0.48 0.29 0.18 0.09 0.07 0.05 0.03 200 9.41 7.46 6.27 4.88 3.42 2.01 1.47 0.9 0.53 0.32 0.19 0.1 0.07 0.06 0.03 500 10.12 8 6.71 5.34 3.83 2.26 1.66 1.03 0.6 0.36 0.22 0.12 0.08 0 0 

1000 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 

Date/time: Thu Jan 31 14:41:55 EST 2008 
D-23 

Precipitation frequency estimates (depth/inches) Point Estimates Data series: Partial duration maxima State: NORTH CAROLINA Station: CHARLOTTE WSO ARPT Lon (dd): -80.9542 Lat (dd): 35.2225 Elev (feet): 728 Date/time: Thu Jan 31 14:38:42 EST 2008 

Freq (yr) 5-min 

10-

min 

15-

min 

30-

min 

60-

min 

120-

min 3-hr 6-hr 12-hr 24-hr 2-day 4-day 7-day 

10-

day 

20-

day 

1 0.4 0.63 0.79 1.09 1.35 1.57 1.68 2.03 2.41 2.77 3.24 3.63 4.17 4.78 6.41 2 0.47 0.75 0.94 1.3 1.64 1.9 2.02 2.45 2.91 3.34 3.9 4.36 4.97 5.69 7.57 5 0.55 0.88 1.11 1.57 2.02 2.36 2.52 3.06 3.64 4.19 4.86 5.37 6.04 6.83 8.93 

10 0.6 0.96 1.22 1.77 2.3 2.71 2.91 3.54 4.23 4.86 5.62 6.18 6.9 7.73 10.01 25 0.67 1.06 1.35 1.99 2.65 3.16 3.44 4.19 5.04 5.76 6.64 7.28 8.08 8.94 11.46 50 0.71 1.13 1.43 2.16 2.93 3.51 3.85 4.7 5.69 6.48 7.45 8.15 9.01 9.89 12.59 

100 0.75 1.19 1.51 2.31 3.19 3.85 4.27 5.23 6.36 7.22 8.27 9.04 9.97 10.85 13.73 200 0.79 1.25 1.57 2.45 3.44 4.19 4.7 5.77 7.06 7.97 9.11 9.95 10.95 11.82 14.89 500 0.83 1.31 1.65 2.62 3.76 4.64 5.29 6.52 8.04 9 10.26 11.2 12.28 13.12 16.44 

1000 0.86 1.35 1.69 2.74 4 4.97 5.75 7.11 8.82 9.8 11.15 12.16 13.31 14.13 17.64 

Precipitation Intensity Estimates (in/hr) 

2 5.64 4.51 3.78 2.61 1.64 0.95 0.67 0.41 0.24 0.14 0.08 0.05 0.03 0.02 0.02 5 6.55 5.25 4.43 3.14 2.02 1.18 0.84 0.51 0.3 0.17 0.1 0.06 0.04 0.03 0.02 

10 7.22 5.78 4.87 3.53 2.3 1.35 0.97 0.59 0.35 0.2 0.12 0.06 0.04 0.03 0.02 25 7.99 6.37 5.38 3.99 2.65 1.58 1.14 0.7 0.42 0.24 0.14 0.08 0.05 0.04 0.02 50 8.53 6.8 5.74 4.32 2.93 1.75 1.28 0.79 0.47 0.27 0.16 0.08 0.05 0.04 0.03 

100 9.02 7.16 6.04 4.62 3.19 1.93 1.42 0.87 0.53 0.3 0.17 0.09 0.06 0.05 0.03 200 9.44 7.49 6.3 4.9 3.44 2.1 1.57 0.96 0.59 0.33 0.19 0.1 0.07 0.05 0.03 500 9.94 7.86 6.59 5.25 3.76 2.32 1.76 1.09 0.67 0.38 0.21 0.12 0.07 0 0 

1000 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 

Date/time: Thu Jan 31 14:39:36 EST 2008 
D-24 

Precipitation frequency estimates (depth/inches) Point Estimates Data series: Partial duration maxima State: SOUTH CAROLINA Station: COLUMBIA WSFO AP Lon (dd): -81.1219 Lat (dd): 33.9456 Elev (feet): 209 Date/time: Thu Jan 31 13:53:59 EST 2008 

Freq (yr) 5-min 

10-

min 

15-

min 

30-

min 

60-

min 

120-

min 3-hr 6-hr 12-hr 24-hr 2-day 4-day 7-day 

10-

day 

20-

day 

1 0.46 0.73 0.91 1.25 1.55 1.79 1.89 2.24 2.61 3.02 3.55 4.02 4.68 5.32 7.17 2 0.53 0.85 1.06 1.47 1.84 2.14 2.25 2.67 3.12 3.62 4.25 4.82 5.57 6.31 8.47 5 0.61 0.97 1.23 1.75 2.24 2.61 2.77 3.27 3.84 4.52 5.28 5.93 6.79 7.61 10.02 

10 0.68 1.08 1.37 1.99 2.59 3.05 3.25 3.85 4.54 5.28 6.13 6.84 7.79 8.68 11.25 25 0.76 1.21 1.53 2.27 3.03 3.62 3.91 4.64 5.51 6.39 7.35 8.13 9.2 10.18 12.93 50 0.83 1.32 1.67 2.51 3.4 4.11 4.49 5.35 6.39 7.33 8.37 9.19 10.36 11.39 14.25 

100 0.89 1.41 1.79 2.74 3.77 4.62 5.1 6.1 7.33 8.35 9.47 10.31 11.58 12.66 15.59 200 0.95 1.51 1.9 2.96 4.15 5.16 5.76 6.92 8.36 9.46 10.66 11.5 12.87 13.99 16.96 500 1.03 1.62 2.04 3.25 4.67 5.91 6.71 8.09 9.87 11.1 12.35 13.21 14.73 15.89 18.8 

1000 1.09 1.72 2.16 3.5 5.11 6.56 7.55 9.14 11.23 12.47 13.75 14.59 16.25 17.43 20.23 

Precipitation Intensity Estimates (in/hr) 

2 6.35 5.08 4.25 2.94 1.84 1.07 0.75 0.45 0.26 0.15 0.09 0.05 0.03 0.03 0.02 5 7.27 5.83 4.91 3.49 2.24 1.3 0.92 0.55 0.32 0.19 0.11 0.06 0.04 0.03 0.02 

10 8.14 6.5 5.48 3.97 2.59 1.52 1.08 0.64 0.38 0.22 0.13 0.07 0.05 0.04 0.02 25 9.12 7.27 6.14 4.55 3.03 1.81 1.3 0.78 0.46 0.27 0.15 0.08 0.05 0.04 0.03 50 9.91 7.9 6.66 5.02 3.4 2.06 1.49 0.89 0.53 0.31 0.17 0.1 0.06 0.05 0.03 

100 10.68 8.48 7.15 5.48 3.77 2.31 1.7 1.02 0.61 0.35 0.2 0.11 0.07 0.05 0.03 200 11.41 9.05 7.61 5.92 4.15 2.58 1.92 1.16 0.69 0.39 0.22 0.12 0.08 0.06 0.04 500 12.32 9.74 8.18 6.51 4.67 2.95 2.23 1.35 0.82 0.46 0.26 0.14 0.09 0 0 

1000 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 

Date/time: Thu Jan 31 13:54:39 EST 2008 
D-25 

Precipitation frequency estimates (depth/inches) Point Estimates Data series: Partial duration maxima State: PUERTO RICO Station: SAN JUAN WSFO Lon (dd): -66 Lat (dd): 18.4333 Elev (feet): 6 Date/time: Tue Feb 5 09:38:04 EST 2008 

Freq (yr) 5-min 

10-

min 

15-

min 

30-

min 

60-

min 

120-

min 3-hr 6-hr 12-hr 24-hr 2-day 4-day 7-day 

10-

day 

20-

day 

1 0.37 0.51 0.66 1.05 1.56 1.87 2 2.48 2.8 3.27 4 4.44 5.12 5.75 7.86 2 0.46 0.63 0.81 1.29 1.91 2.34 2.51 3.15 3.62 4.26 5.21 5.75 6.59 7.35 9.92 5 0.52 0.7 0.9 1.45 2.15 2.7 2.95 3.89 4.7 5.66 6.9 7.61 8.56 9.32 12.13 

10 0.55 0.76 0.97 1.56 2.31 2.94 3.25 4.42 5.54 6.76 8.26 9.11 10.14 10.9 13.89 25 0.6 0.82 1.05 1.69 2.5 3.24 3.61 5.08 6.68 8.29 10.13 11.2 12.33 13.05 16.24 50 0.63 0.86 1.11 1.78 2.64 3.45 3.88 5.58 7.58 9.5 11.63 12.88 14.08 14.76 18.07 

100 0.66 0.9 1.16 1.86 2.76 3.64 4.13 6.06 8.49 10.75 13.17 14.6 15.88 16.5 19.91 200 0.69 0.94 1.21 1.93 2.87 3.83 4.37 6.54 9.44 12.04 14.79 16.42 17.75 18.28 21.78 500 0.72 0.98 1.26 2.02 3 4.06 4.68 7.17 10.73 13.83 17.03 18.96 20.35 20.73 24.27 

1000 0.74 1.01 1.3 2.09 3.1 4.22 4.9 7.64 11.74 15.24 18.8 20.97 22.4 22.65 26.17 

Precipitation Intensity Estimates (in/hr) 

2 5.51 3.77 3.22 2.58 1.91 1.17 0.84 0.53 0.3 0.18 0.11 0.06 0.04 0.03 0.02 5 6.18 4.22 3.62 2.89 2.15 1.35 0.98 0.65 0.39 0.24 0.14 0.08 0.05 0.04 0.03 

10 6.65 4.54 3.89 3.11 2.31 1.47 1.08 0.74 0.46 0.28 0.17 0.09 0.06 0.05 0.03 25 7.2 4.93 4.21 3.37 2.5 1.62 1.2 0.85 0.55 0.35 0.21 0.12 0.07 0.05 0.03 50 7.6 5.19 4.44 3.56 2.64 1.72 1.29 0.93 0.63 0.4 0.24 0.13 0.08 0.06 0.04 

100 7.93 5.42 4.64 3.72 2.76 1.82 1.37 1.01 0.71 0.45 0.27 0.15 0.09 0.07 0.04 200 8.26 5.64 4.83 3.86 2.87 1.91 1.45 1.09 0.78 0.5 0.31 0.17 0.11 0.08 0.05 500 8.64 5.9 5.05 4.04 3 2.03 1.56 1.2 0.89 0.58 0.35 0.2 0.12 0 0 

1000 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 

Date/time: Tue Feb 5 09:39:39 EST 2008 
D-26 

Precipitation frequency estimates (depth/inches) Point Estimates Data series: Partial duration maxima State: DISTRICT OF COLUMBIA Station: NATIONAL ARBORETUM WASHINGTON DC Lon (dd):-76.97 Lat (dd): 38.9133 Elev (feet): 78 Date/time: Tue Feb 5 09:44:27 EST 2008 

Freq (yr) 5-min 

10-

min 

15-

min 

30-

min 

60-

min 

120-

min 3-hr 6-hr 12-hr 24-hr 2-day 4-day 7-day 

10-

day 

20-

day 

1 0.35 0.56 0.7 0.96 1.2 1.41 1.51 1.85 2.25 2.61 3.03 3.37 3.91 4.46 6.02 2 0.42 0.67 0.85 1.17 1.47 1.71 1.83 2.25 2.71 3.16 3.67 4.07 4.7 5.35 7.16 5 0.5 0.8 1.01 1.44 1.85 2.17 2.33 2.84 3.44 4.06 4.7 5.2 5.94 6.68 8.65 

10 0.56 0.9 1.13 1.64 2.14 2.52 2.72 3.32 4.08 4.85 5.59 6.18 7.01 7.8 9.86 25 0.63 1.01 1.28 1.9 2.52 3.02 3.27 4.04 5.04 6.07 6.93 7.64 8.6 9.42 11.55 50 0.69 1.1 1.39 2.09 2.83 3.42 3.73 4.65 5.89 7.15 8.09 8.91 9.96 10.78 12.92 

100 0.74 1.18 1.49 2.29 3.15 3.84 4.22 5.32 6.83 8.37 9.39 10.32 11.48 12.25 14.33 200 0.8 1.26 1.59 2.48 3.47 4.28 4.73 6.03 7.87 9.76 10.84 11.9 13.15 13.84 15.8 500 0.86 1.36 1.72 2.73 3.92 4.91 5.47 7.09 9.47 11.9 13.03 14.26 15.65 16.16 17.85 

1000 0.91 1.44 1.8 2.92 4.26 5.42 6.07 7.98 10.86 13.78 14.91 16.3 17.79 18.1 19.47 

Precipitation Intensity Estimates (in/hr) 

2 5.05 4.04 3.38 2.34 1.47 0.86 0.61 0.37 0.23 0.13 0.08 0.04 0.03 0.02 0.01 5 6.01 4.81 4.06 2.88 1.85 1.08 0.77 0.47 0.29 0.17 0.1 0.05 0.04 0.03 0.02 

10 6.72 5.37 4.53 3.28 2.14 1.26 0.9 0.55 0.34 0.2 0.12 0.06 0.04 0.03 0.02 25 7.61 6.06 5.12 3.79 2.52 1.51 1.09 0.68 0.42 0.25 0.14 0.08 0.05 0.04 0.02 50 8.27 6.58 5.56 4.18 2.83 1.71 1.24 0.78 0.49 0.3 0.17 0.09 0.06 0.04 0.03 

100 8.92 7.09 5.97 4.57 3.15 1.92 1.4 0.89 0.57 0.35 0.2 0.11 0.07 0.05 0.03 200 9.54 7.56 6.36 4.95 3.47 2.14 1.58 1.01 0.65 0.41 0.23 0.12 0.08 0.06 0.03 500 10.33 8.17 6.86 5.46 3.92 2.46 1.82 1.18 0.79 0.5 0.27 0.15 0.09 0 0 

1000 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 

Date/time: Tue Feb 5 09:45:19 EST 2008 
D-27 

Figure D-6. NOAA Atlas 2 – Montana – Isopluvials of 2-year, 24-hour precipitation in tenths of an inch. 
D-28 

Figure D-7. Technical Paper No. 40 Rainfall Frequency Atlas of the United States for Durations from 30 Minutes to 24 Hfrom 1 to 100 Years – 10-Year, 6-Hour Rainfall (inches). 
D-29 

Table D-4. Atlas 2 and technical paper map results 

2-year, 24-hour storm 10-year, 24-hour storm 25-year, 24-hour storm 1

State Indicator city Depth (inches) Intensity (inches/hr) Depth (inches) Intensity (inches/hr) Depth (inches) Intensity (inches/hr) 

(

Alabama Montgomery 4.50 0.19 6.5 0.27 7.6 0.32 Arkansas Little Rock 4.10 0.17 6.05 0.25 7 0.29 California Sacramento 2.00 0.08 3 0.13 3.5 0.15 Colorado Denver 2.00 0.08 3 0.13 3.8 0.16 Connecticut Hartford 3.10 0.13 4.8 0.2 5.5 0.23 Florida Tallahassee 4.75 0.20 7.4 0.31 8.5 0.35 Georgia Atlanta 3.70 0.15 5.5 0.23 6.5 0.27 Hawaii Honolulu 4.75 0.20 7.8 0.33 8.9 0.37 Idaho Boise 1.20 0.05 1.8 0.08 2.2 0.09 Iowa Des Moines 3.25 0.14 4.7 0.2 5.5 0.23 Kansas Kansas City 3.50 0.15 5.2 0.22 6.1 0.25 Louisiana Baton Rouge 5.25 0.22 8.2 0.34 9.1 0.38 Maine Augusta 2.80 0.12 4.25 0.18 4.9 0.2 Massachusetts Boston 3.10 0.13 4.5 0.19 5.5 0.23 Michigan Lansing 2.40 0.10 3.6 0.15 4.2 0.18 Minnesota St. Paul 2.75 0.11 4.2 0.18 4.7 0.2 Mississippi Jackson 4.45 0.19 6.7 0.28 7.8 0.33 Missouri Kansas City 3.45 0.14 5.3 0.22 6 0.25 Montana Helena 1.30 0.05 2.1 0.09 2.4 0.1 Nebraska Lincoln 3.00 0.13 4.8 0.2 5.4 0.23 New Hampshire Manchester 2.80 0.12 4.3 0.18 5 0.21 New York Albany 2.90 0.12 4 0.17 5.9 0.25 North Dakota Bismarck 1.90 0.08 3.25 0.14 3.75 0.16 Oklahoma Oklahoma City 3.70 0.15 5.8 0.24 6.9 0.29 Oregon Salem 2.50 0.10 3.5 0.15 4 0.17 Rhode Island Providence 3.20 0.13 4.8 0.2 5.7 0.24 South Dakota Pierre 2.25 0.09 3.5 0.15 4.1 0.17 Texas Fort Worth 3.90 0.16 6.3 0.26 7.4 0.31 Vermont Montpelier 2.40 0.10 3.7 0.15 4.25 0.18 Washington Seattle 2.00 0.08 3 0.13 3.4 0.14 Wisconsin Madison 2.80 0.12 4.1 0.17 4.75 0.2 Wyoming Cheyenne 1.60 0.07 2.4 0.1 2.8 0.12 
Appendix D: Precipitation Data Representative of Major U.S. Metropolitan Areas 

D-30 

Sources: PRISM, Oregon State University. http://mole.nacse.org/prism/nn/index.phtml; PRISM 

data sets were developed through projects funded partly by the USDA Natural Resources 

Conservation Service, USDA Forest Service, NOAA Office of Global Programs, and others. 

Class/Location and Latitude/Longitude Sources: USGS Geographic Names Information 

System (GNIS) http://geonames.usgs.gov/pls/gnispublic/, and National Oceanic and 

Atmospheric Administration (NOAA) National Weather Service (NWS) Precipitation Frequency 

Data Server (PFDS) Atlas 14 http://hdsc.nws.noaa.gov/hdsc/pfds/. 

PRISM Data Variables:

Parameter: Annual Precipitation 

Start year: 1895 

Stop year: 2007 

Units: inches 

Table D-5. Average annual precipitation data (1895 to 2007) 

Indicator city, State 

USGS class location 

(e.g., Populated Place) 

OR 

NOAA NWS Precipitation Frequency Data Server 

Atlas 14 site location (e.g., WSO ARP) 

Latitude 

(Northing) 

Longitude 

(Westing) 

Average 

precipitation 

(inches) 

Montgomery, Alabama Montgomery Populated Place (165344) 32.3668 -86.2999 49.04 

Phoenix, Arizona Phoenix WSFO AP, AZ (02-6481) 33.443 -111.99 7.74 

Little Rock, Arkansas Little Rock Populated Place (83350) 34.7464 -92.2895 47.62 

Sacramento, California Sacramento Populated Place (1659564) 38.5815 -121.494 18.39 

Denver, Colorado Denver Populated Place (201738) 39.7391 -104.984 13.31 

Hartford, Connecticut Hartford Populated Place (213160) 41.7637 -72.685 44.41 

Dover, Delaware Dover, Delaware (07-2730) 39.2583 -75.516 43.02 

Tallahassee, Florida Tallahassee Populated Place (308416) 30.4382 -84.2807 62.01 

Atlanta, Georgia Atlanta Populated Place (351615) 33.7489 -84.3879 50.86 

Boise, Idaho Boise Populated Place (400590) 43.6135 -116.203 11.33 

Chicago, Illinois Chicago O'Hare WSO ARP, IL (11-1549) 41.986 -87.9142 33.04 

Indianapolis, Indiana Indianapolis WSFO AP, IN (12-4259) 39.7317 -86.2789 39.69 

Des Moines, Iowa Des Moines Populated Place (465961) 41.6005 -93.6091 31.66 

Kansas City, Kansas Kansas City Populated Place (478635) 39.1141 -94.6274 36.69 

Frankfort, Kentucky Frankfort Lock 4, KY (15-3028) 38.235 -84.8817 45.01 

Baton Rouge, Louisiana Baton Rouge Populated Place (1629914) 30.4507 -91.1545 58.77 

Augusta, Maine Augusta Populated Place (581636) 44.3106 -69.7794 41.67 

Baltimore, Maryland Baltimore WSO AP, MD (18-0465) 39.1722 -76.6839 42.28 

Boston, Massachusetts Boston Populated Place (617565) 42.3584 -71.0597 42.40 

Lansing, Michigan Lansing Populated Place (1625035) 42.7325 -84.5555 30.28 

Saint Paul, Minnesota Saint Paul Populated Place (662851) 44.9444 -93.0932 28.76 
Appendix D: Precipitation Data Representative of Major U.S. Metropolitan Areas 

D-31 

Indicator city, State 

USGS class location 

(e.g., Populated Place) 

OR 

NOAA NWS Precipitation Frequency Data Server 

Atlas 14 site location (e.g., WSO ARP) 

Latitude 

(Northing) 

Longitude 

(Westing) 

Average 

precipitation 

(inches) 

Jackson, Mississippi Jackson Populated Place (711543) 32.2987 -90.1848 52.48 

Helena, Montana Helena Populated Place (802116) 46.5927 -112.036 11.78 

Lincoln, Nebraska Lincoln Populated Place (837279) 40.8 -96.6669 28.31 

Las Vegas, Nevada Las Vegas WSO Airport, NV (26-4436) 36.0833 -115.166 3.82 

Manchester, New Hampshire Manchester Populated Place (868243) 42.9956 -71.4547 40.23 

Hightstown, New Jersey Hightstown 2 W, NJ (28-3951) 40.265 -74.5642 47.00 

Santa Fe, New Mexico Santa Fe, NM (29-8072) 35.6833 -105.9 15.46 

Albany, New York Albany Populated Place (977310) 42.6525 -73.7562 36.91 

Charlotte, North Carolina Charlotte WSO ARPT, NC (31-1690) 35.2225 -80.9542 43.19 

Bismarck, North Dakota Bismarck Populated Place (1035849) 46.8083 -100.783 16.09 

Columbus, Ohio Columbus WSO Airport, OH (33-1786) 39.9914 -82.8808 37.79 

Oklahoma City, Oklahoma Oklahoma City Populated Place (1102140) 35.4675 -97.5164 32.81 

Salem, Oregon Salem Populated Place (1167861) 44.9428 -123.035 40.72 

Philadelphia, Pennsylvania Philadelphia WSO AP, PA (36-6889) 39.8683 -75.2311 41.62 

Providence, Rhode Island Providence Populated Place (1219851) 41.8239 -71.4128 44.74 

Columbia, South Carolina Columbia WSFO AP, SC (38-1939) 33.9456 -81.1219 45.45 

Pierre, South Dakota Pierre Populated Place (1266887) 44.3683 -100.35 16.10 

Nashville, Tennessee Nashville WSO Airport, TN (40-6402) 36.1253 -86.6764 46.11 

Fort Worth, Texas Fort Worth Populated Place (1380947) 32.7254 -97.3208 32.52 

Salt Lake City, Utah Salt Lake City NWSFO, UT (42-7598) 40.7725 -111.955 14.56 

Montpelier, Vermont Montpelier Populated Place (1461834) 44.26 -72.5753 34.00 

Arlington, Virginia Washington Reagan AP (44-8906) 38.865 -77.0342 40.35 

Seattle, Washington Seattle Populated Place (1512650) 47.6062 -122.332 35.26 

Charleston, West Virginia Charleston WSFO AP, WV (46-1570) 38.3794 -81.5914 42.82 

Madison, Wisconsin Madison Populated Place (1581834) 43.073 -89.4012 31.47 

Cheyenne, Wyoming Cheyenne Populated Place (1609077) 41.1399 -104.82 14.74 

District of Columbia National Arboretum DC (18-6350) 38.9133 -76.97 41.74 
Appendix E 

Determination of Development Rates in U.S. Watersheds 
Appendix E: Determination of Development Rates in U.S. Watersheds 

E-1 

Land Use Data Sources 

There are multiple sources of land cover change information at a national scale. The U.S. 

Environmental Protection Agency (EPA) initially reviewed the U.S. Department of Agriculture 

(USDA) National Resources Inventory (NRI). The NRI is a publicly available data set that tracks 

temporal changes in major land covers within the United States using a sampling method. NRI 

data is available for the entire United States on an 8-digit hydrologic unit basis (hydrologic units1

or HUCs) for the years 1982, 1987, 1992, and 1997. Data from these years are comparable and 

can be used for analyzing land cover change at several broad scales. Data from NRI are also 

available for the years 2001, 2002, and 2003, though not on an HUC basis. Data from these years 

are available only at the major river basin level, and are not directly comparable to data from 

earlier years because of changes in statistical and sampling methodologies. 

The U.S. Geological Survey (USGS) National Land Cover Dataset (NLCD) provides another 

national source of data on land cover change. The Multi-Resolution Land Characteristics 

Consortium (MRLC) has produced the NLCD data sets that are based on classification of 

30-meter pixel resolution Landsat ETM+ (TM) satellite imagery. NLCD data is publicly 

available for the years 1992 and 2001.2

 Because new developments in mapping methodology, 

new sources of input data, and changes in the mapping legend for the 2001 National Land Cover 

Database (NLCD 2001) confound direct comparison between NLCD 2001 and the 1992 National 

Land Cover Dataset (NLCD 1992), USGS prepared and recently released the NLCD 1992/2001 

Retrofit Land Cover Change Product. The NLCD 1992/2001 Retrofit Land Cover Change 

Product was developed to offer more accurate direct change analysis between the two products. 

The NLCD 1992/2001 Retrofit Land Cover Change Product uses a specially developed 

methodology to provide land cover change information at the Anderson Level I classification 

scale,3 relying on decision tree classification of Landsat imagery from 1992 and 2001. While 

NLCD 1992 reported on developed land in the categories of low-intensity residential, highintensity residential, commercial/industrial/transportation, and urban/recreational grasses, NLCD 

2001 reported categories of developed low, medium, high, and open space. To compare change 

between the two data sets, the developed categories were merged into one overall urban class. 

Unchanged pixels between the two dates are coded with the NLCD 2001 Anderson Level I class 

code, while changed pixels are labeled with a from-to land cover change value. Modified 

Anderson Level I Classifications include the following: 

 Open water 

 Urban 

 Barren 

 Forest 

 Grassland/Shrub 

 Agriculture 

 Wetlands Ice/Snow 

 

1

 For definitions of hydrologic units, see http://water.usgs.gov/GIS/huc.html. 2

 To obtain data and for further descriptions of NLCD products, see http://www.mrlc.gov/index.asp. 3

 See http://landcover.usgs.gov/pdf/anderson.pdf
Appendix E: Determination of Development Rates in U.S. Watersheds 

E-2 

The NLCD 1992/2001 Retrofit Land Cover Change Product was intended to provide a current, 

consistent, and seamless data set for the United States at medium spatial resolution for Anderson 

Level I classes. This land cover change map and all documents pertaining to it are considered 

provisional until a formal accuracy assessment can be conducted. Detailed definitions and 

discussion of the NLCD 1992/2001 Retrofit Land Cover Change Product will be provided in an 

upcoming paper.4

Watershed Boundary Data Sources 

HUC boundaries encompass surface water drainage to an outlet and are useful units for 

summarization of land cover change information. HUCs through four levels were created in the 

1970s as the USGS developed a hierarchical HUC that divides the country into 21 regions, 222 

subregions, 352 accounting units, and 2,149 cataloging units on the basis of surface hydrologic 

features. The 8-digit HUC, or cataloging unit (now referred to as a basin), is approximately 

448,000 acres. By the 1990s, geographic information system (GIS) tools facilitated the mapping 

of digital HUC boundaries and the Natural Resources Conservation Service started to delineate 

HUCs to the 5th and 6th level by using GIS to meet 1:24,000 National Map Accuracy Standards. 

With increased interest from other federal, state, and local entities, this initiative became an 

interagency effort to create the Watershed Boundary Dataset (WBD) as a hydrologically correct, 

seamless, and consistent national GIS database. The new levels are called watershed (5th level, 

10-digit) and subwatershed (6th level, 12-digit). The watershed level is typically 40,000 to 

250,000 acres, and the subwatershed level is typically 10,000 to 40,000 acres. An estimated 

22,000 watersheds and 160,000 subwatersheds will be mapped to the 5th and 6th level when the 

data set is complete. 

The WBD provides publicly available spatial data for watershed boundaries at various scales 

within the United States. Attachment A shows the status of the WBD for the nation as of April 

28, 2008. EPA is working to certify 10- and 12-digit HUC boundaries for the remainder of the 

country. Because the WBD is not complete, and because the water quality model used by EPA 

(SPARROW) does not operate on HUC boundaries, EPA chose not to characterize land use 

change on a HUC basis. 

Another option for summarizing national land cover change in drainage area units is to use a 

coarser USGS data set than the WBD. A consistent, national scale watershed data set was 

prepared to match the Reach File Version 1.0 (RF1) hydrology data set, a vector database used 

extensively by EPA and states to model approximately 700,000 miles of streams and open waters 

in the conterminous United States. This watershed data set, the Enhanced River Reach File 1.2 

(ERF1_2), was designed to be a digital database of river reaches capable of supporting regional 

and national water-quality and river-flow modeling.5

 The ERF1_2 coverage extends the earlier 

drainage area founded on the 1-kilometer data for North America.6

 ERF1_2 contains 67,171 

watersheds with a minimum size of 247 acres (1 km2

) and an average size of 30,182 acres (122 

 

4

 Coan, M., Fry, J., Homer, C., Meyer D. K., Larson, C., and J. Wickham. In Progress. Completion of the National 

Land Cover Database 1992/2001 Change Product. 

5

 Further information on ERF1_2 watersheds is at http://water.usgs.gov/GIS/metadata/usgswrd/XML/erf1_2.xml. 6

 Verdin, K.L., and S.K. Jenson. 1996. Development of continental scale digital elevation models and extraction of 

hydrographic features. In Proceedings of the Third International Conference/Workshop on Integrating GIS and 

Environmental Modeling. CD-ROM. Santa Fe, NM. 
Appendix E: Determination of Development Rates in U.S. Watersheds 

E-3 

km2). (See DCN 43097 in the Administrative Record for an index of the spatial data analyses 

conducted for the proposed rule. 

Analysis 

EPA prepared spreadsheets summarizing the amount of acreage changing from undeveloped land 

to developed land within each state and ERF1_2 watershed of the United States by aggregating 

land cover change estimates from the NLCD 1992/2001 Retrofit Land Cover Change Product on 

an ERF1_2 level. Figure 1 shows an example of the Retrofit Land Cover Change Product near an 

urban area. 

Figure E-1. NLCD 1992/2001 Retrofit Land Cover Change 

Product near Seattle, Washington. 

Attachment B provides processing notes for the NLCD 1992/2001 Retrofit data analysis run by 

EPA. This data was combined with EPA Region boundaries by spatially joining the National 

Atlas State coverage7

 attributed with EPA Region borders and the ERF1_2 watersheds. EPA 

Regional boundaries were thus joined to ERF1_2 watershed so that developed areas within each 

region could be identified. Representative urban areas describing the fastest developing and 

greatest land area developing between 1992 and 2001 in a watershed are shown in Table E-1 and 

Figure E-2. 

 

7

 http://www.nationalatlas.gov/mld/statesp.html 
Appendix E: Determination of Development Rates in U.S. Watersheds 

E-4 

Table E-1. Fastest developing watersheds by 

representative urban area per EPA Region 

EPA Region Indicator cities 

1 Manchester, NH 

2 Albany, NY 

3 Washington, DC, VA, MD 

4 Atlanta, GA 

5 Chicago, IL—IN 

6 Dallas, Fort Worth, and Arlington, TX 

7 Kansas City, MO and KS 

8 Denver and Aurora, CO 

9 Las Vegas, NV 

10 Boise City, ID 

Seattle, WA 

Figure E-2. Urban Areas Selected for Each EPA Region. 

After representative urban area watersheds were targeted, the ERF1_2 watershed summarizations 

were also aggregated by state. When summarizing by state, an approach was needed to apportion 

partial watersheds (those crossing state boundaries) into state aggregations. Allocation of 

developed acreage within ERF1_2 watersheds overlapping state boundaries was done using a 

basic area-weighting approach. 

Table E-2 shows a national overview of developed acreage according to data source. Attachment 

C presents state level results for developed acreage change in each ERF1_2 watershed. 
Appendix E: Determination of Development Rates in U.S. Watersheds 

E-5 

Table E-2. National change in developed acreage (1992–2001) 

Source 

1992 

(million acres) 

2001 

(million acres) 

NLCD RETROFIT 96.8 102.1 

State aggregated NLCD RETROFIT 

ERF1_2 watersheds 96.5 101.8 

NLCD (original) 40.3 101.3 

NRI 87 106.3 

Attachment A. Status of Watershed Boundary Data Set 
Appendix E: Determination of Development Rates in U.S. Watersheds 

E-6 

Attachment B. NLCD 1992-2001 Land-cover Change Estimates Processing Notes 

J. Wickham and T. Wade (EPA/ORD/NERL/ESD/LEB) 

02/08/2008 

Grabbed erf file from water.usgs.gov/gis site 

61,215 watersheds in erf1_2ws_lg (61215 records in vat) 

1186 single pixel watersheds 

67,172 polygons in vector version 

Frequency of vector version returns 61215 unique values of grid_code 

Projected into albers 

67171 polygons in albers version 

61214 unique grid-codes 

5957 multi-part polygons 

WS is used throughout as an acronym for watershed; WS is also equivalent to grid-code. 

US was split into 8 regions to estimate changes (nw1, nw2, ne1, ne2, sw1, sw2, se1, se2) 

changes were compiled into master file using 

$1lcclass<date> = <>lcclass<date> + $1lcclass<date> where $1 = masterfile and <> = the 

regional files the equation sums watersheds that were split across regions. Areas were summed 

then converted to percentages. The attribute labeled area was used to convert to percentages. 

47 watersheds split across regions. 

 8562 9124 14264 14776 14857 15006 15324 16331 18374 23999 24000 24242 25213 25230 

26327 26371 28767 30796 30816 31089 31378 33206 35283 36052 38432 38460 38550 38598 

39269 39841 41670 41698 41758 42307 42309 42697 42712 42817 42831 43718 58938 58994 

59002 80951 81729 

8 WS outside US 

grid-code 95005 completely outside US (in CA west of ME) 

grid-code 32171 completely outside US (in CA Nrth of MT) 

others 31486 31534, 31535, 35239,35276, 42648 

These WS have a -1 for LA01 and LA92 (explained below). 

82 watersheds (grid-codes) in water; no land change estimates 

1671 1762 1917 1918 4439 4440 4454 4455 10527 11764 11765 11766 11973 12181 12384 

12440 12553 12555 18003 18014 19055 21249 21251 22621 22728 22793 22821 22854 26515 

29044 29059 29063 29072 29261 32037 32051 32102 32108 32136 34650 34664 34665 34666 

34787 34810 34811 34814 34818 38005 38051 38053 38154 38266 38816 38817 38818 38819 

38820 38821 38975 40981 41030 42294 44296 45535 46510 46544 56786 57091 57095 57211 

57427 57428 57526 57685 57689 57696 60232 65001 65002 80886 81545 

Attributes LA92 and LA01 = land area in watershed for 1992 and 2001, respectively. Large 

changes in the amount of water will cause anomalies in the percentage differences. For example, 

WS 26515 in north central Missouri went from ag to water. It’s a small (1km^2) WS. These 
Appendix E: Determination of Development Rates in U.S. Watersheds 

E-7 

anomalies will be common on the coast, and otherwise spread throughout were the small 

(i.e., 1km^2) WS overlay such changes. WS 81555 is a coastal example at the mouth of the Miss. 

R. The attribute Dwatpct was added as a flag for changing amounts of water. It was calculated as 

( ( LA01 - LA92 ) / area ) * 100. The max value of Dwatpct is 67 percent in WS = 56768. The 

change is due to sedimentation of a reservoir in the PNW. There are 191 WS with Dwatpct >= 

5 percent. 

Attachment C. State Level Results for NLCD Developed Acreage Change in Each 

Watershed 

State 1992devacre 2001devacre 

Annual development 

rate 

Alabama 2,066,843 2,197,496 14,517 

Arizona 1,285,258 1,408,765 13,723 

Arkansas 1,836,496 1,912,492 8,444 

California 6,278,143 6,524,815 27,408 

Colorado 1,609,387 1,751,902 15,835 

Connecticut 727,078 736,015 993 

Delaware 113,052 120,720 852 

Florida 4,526,626 4,870,084 38,162 

Georgia 3,026,921 3,319,772 32,539 

Idaho 847,520 898,118 5,622 

Illinois 4,014,480 4,197,711 20,359 

Indiana 2,238,170 2,353,388 12,802 

Iowa 2,527,225 2,621,239 10,446 

Kansas 2,463,194 2,666,459 22,585 

Kentucky 1,740,669 1,830,327 9,962 

Louisiana 1,788,423 1,903,893 12,830 

Maine 653,697 695,682 4,665 

Maryland 698,386 754,384 6,222 

Massachusetts 1,174,234 1,203,889 3,295 

Michigan 3,746,569 3,946,405 22,204 

Minnesota 2,648,001 2,731,809 9,312 

Mississippi 1,721,138 1,827,869 11,859 

Missouri 2,845,661 2,967,035 13,486 

Montana 1,187,901 1,246,068 6,463 

Nebraska 1,699,570 1,752,634 5,896 

Nevada 572,706 646,794 8,232 

New Hampshire 426,786 443,382 1,844 

New Jersey 1,124,705 1,162,613 4,212 

New Mexico 799,207 838,609 4,378 

New York 2,682,301 2,752,573 7,808 

North Carolina 2,816,229 2,984,988 18,751 

North Dakota 1,667,029 1,727,113 6,676 

Ohio 3,549,025 3,705,445 17,380 

Oklahoma 2,387,508 2,537,439 16,659 

Oregon 1,552,824 1,617,957 7,237 

Pennsylvania 3,006,384 3,149,538 15,906 

Rhode Island 173,764 177,085 369 
Appendix E: Determination of Development Rates in U.S. Watersheds 

E-8 

State 1992devacre 2001devacre 

Annual development 

rate 

South Carolina 1,487,194 1,632,427 16,137 

South Dakota 1,315,111 1,388,776 8,185 

Tennessee 2,189,700 2,307,879 13,131 

Texas 8,229,892 8,791,816 62,436 

Utah 758,031 831,309 8,142 

Vermont 304,570 309,628 562 

Virginia 1,818,500 1,954,409 15,101 

Washington 2,286,574 2,402,332 12,862 

West Virginia 1,016,805 1,049,133 3,592 

Wisconsin 2,345,956 2,411,998 7,338 

Wyoming 491,168 516,818 2,850 

District of Columbia 26,381 28,865 276 

State aggregated totals 96,492,992 101,807,897 590,545