Environmental Assessment for Proposed Effluent Guidelines and Standards for the Construction and Development Category June 2002 Environmental Assessment for Proposed Effluent Guidelines and Standards for the Construction and Development Category June 2002 United States Environmental Protection Agency Office of Water (4303T) 1200 Pennsylvania Avenue, NW Washington, DC 20460 www. epa. gov/ waterscience/ guide/

[EPA 821 R 02 009] Acknowledgments and Disclaimer The Construction and Development Effluent Guidelines proposed rule and support documents were prepared by the C& D Project Team: Eric Strassler, Project Manager; Jesse Pritts, P. E., Engineer; George Denning, Economist; Karen Maher, Environmental Assessor; and Michael G. Lee, Attorney. Technical support for this Environmental Assessment was provided by Tetra Tech, Inc.

Neither the United States government nor any of its employees, contractors, subcontractors or other employees makes any warranty, expressed or implied, or assumes any legal liability or responsibility for any third party's use of, or the results of such use of, any information, apparatus, product or process discussed in this report, or represents that its use by such a third party would not infringe on privately owned rights. Mention of trade names or commercial products does not constitute endorsement by EPA or recommendation for use. Environmental Assessment of Construction and Development Proposed Effluent Guidelines June 2002 i Contents Section 1 Introduction and Background 1.1 Introduction .......................................................... 1 1 1.2 Organization of Environmental Assessment ................................. 1 2 1.3 Review of Regulatory History Related to C& D Industries ...................... 1 3 1.3.1 Clean Water Act ................................................. 1 3 <IP_ADDRESS> NPDES Storm Water Permit Program .......................... 1 3 1.3.2 Other State and Local Government Storm Water Requirements ............ 1 4 Section 2 Categories of Reported Impacts and Pollutants 2.1 Introduction .......................................................... 2 1 2.2 Pollutants Associated with Construction and Land Development Storm Water Runoff .................................................... 2 2 2.2.1 Sediment ...................................................... 2 2 <IP_ADDRESS> Sources of Sediment ....................................... 2 2 <IP_ADDRESS> Receiving Waters Impacts ................................... 2 5 2.2.2 Metals ........................................................ 2 7 <IP_ADDRESS> Sources of Metal Runoff .................................... 2 8 <IP_ADDRESS> Metals Impacts on Receiving Waters .......................... 2 10 2.2.3 PAHs, and Oil and Grease ........................................ 2 11 <IP_ADDRESS> Sources of PAHs, and Oil and Grease ........................ 2 11 <IP_ADDRESS> Receiving Water Impacts ................................... 2 12 2.2.4 Pathogens .................................................... 2 13 <IP_ADDRESS> Sources of Pathogens ...................................... 2 13 <IP_ADDRESS> Receiving Water Impacts .................................. 2 15 2.3 Physical Impacts of Construction and Land Development Activities ............. 2 16 2.3.1 Hydrologic Impacts ............................................. 2 18 <IP_ADDRESS> Increased Runoff Volume .................................. 2 19 <IP_ADDRESS> Increased Flood Peaks ..................................... 2 22 <IP_ADDRESS> Increased Frequency and Volume of Bankfull Flows ............. 2 22 <IP_ADDRESS> Changes in Baseflow ...................................... 2 22 2.3.2 Impacts on Geomorphology/ Sediment Transport ...................... 2 23 <IP_ADDRESS> Increased Transport of Sediment ............................. 2 23 <IP_ADDRESS> Decreased Sediment Transport .............................. 2 25 <IP_ADDRESS> Increase in Size of Channel ................................. 2 26 2.3.3 Changes in Habitat Structure ...................................... 2 27 <IP_ADDRESS> Embeddedness ........................................... 2 27 <IP_ADDRESS> Large Woody Debris (LWD) ................................ 2 28 Environmental Assessment of Construction and Development Proposed Effluent Guidelines June 2002 ii <IP_ADDRESS> Changes in Stream Features ................................. 2 29 2.3.4 Thermal Impacts ............................................... 2 29 2.3.5 Direct Channel Impacts .......................................... 2 30 <IP_ADDRESS> Channel Straightening and Hardening/ Reduction in First Order Streams ............................................. 2 30 <IP_ADDRESS> Fish Blockages ........................................... 2 30 2.3.6 Site Differences in Physical Impacts ................................ 2 30 Section 3 Description of Assessment Methodology 3.1 Introduction .......................................................... 3 1 3.2 Methodology to Estimate Pollutant Loadings from Construction Runoff Water Discharges ...................................................... 3 1 3.3 Characterizing the Nation's Stream Network ................................ 3 4 3.3.1 Characterizing the Stream Network within Developing Acreage ........... 3 9 3.3.2 Characterizing the Flow Conditions in Stream Network ................. 3 12 3.3.3 Converting Stream Miles into Impact Estimates ....................... 3 14 Section 4 Environmental Benefits Assessment of Evaluated Regulatory Options 4.1 Total Suspended Solids Loadings ......................................... 4 1 4.2 Total Suspended Solid In Stream Concentrations ............................. 4 3 4.3 Miscellaneous Impacts .................................................. 4 4 Section 5 References ....................................................... 5 1 Appendices A. Evaluating Pollutant Loadings from Construction Activities that Potentially Impact the Environment ...................................................... A 1 B. Inventorying of Streams Potentially Impacted by Construction Activities .......... B 1 C. Impacts of Construction Activity on Hydrology .............................. C 1 Tables Table 1 1. Regulatory Options Evaluated for Controlling Discharges from Construction Activities ........................................... 1 2 Table 2 1. Studies of Soil Erosion as TSS From Construction Sites ................. 2 3 Table 2 2. Sources of Sediment in Urban Areas ................................. 2 4 Table 2 3. Source Area Concentrations for TSS in Urban Areas .................... 2 4 Environmental Assessment of Construction and Development Proposed Effluent Guidelines June 2002 iii Table 2 4. Sediment Impacts on Receiving Waters .............................. 2 6 Table 2 5. Metal Sources and Hot Spots in Urban Areas .......................... 2 9 Table 2 6. Metal Source Area Concentrations in Urban Areas .................... 2 10 Table 2 7. Metals Impacts on Receiving Waters ................................ 2 11 Table 2 8. Effects of PAHs and Oil and Grease on Receiving Waters ............... 2 13 Table 2 9. Percentage Detection of Giardia Cysts and Cryptosporidium Oocysts in Subwatersheds and Wastewater Treatment Plant Effluent in the New York City Water Supply Watersheds ........................... 2 15 Table 2 10. Effects of Bacteria on Receiving Waters ............................. 2 16 Table 2 11. Physical Impacts on Streams ...................................... 2 17 Table 2 12. Hydrologic Differences Between a Parking Lot and a Meadow ........... 2 20 Table 2 13. Comparison of Bulk Density for Undisturbed Soils and Common Urban Conditions .............................................. 2 21 Table 3 1. Common Construction Erosion and Sediment Control BMPs ............. 3 2 Table 3 2. Site BMPs Evaluated by EPA for Effluent Guidelines Development ........ 3 3 Table 3 3. Results of the National Stream Survey ............................... 3 6 Table 3 4. Land Development Annually in Ecoregions ......................... 3 11 Table 3 5. Characterization of Stream Orders for Ecoregions ..................... 3 13 Table 3 6. Characterization of Stream Length by Flow Type for Ecoregions ......... 3 14 Table 3 7. Estimated Miles of Streams Potentially Affected by One Year's Construction ................................................... 3 16 Table 3 8. Active Construction Site Runoff Scenarios for Option 1 and Option 2 ..... 3 18 Table 3 9. Runoff Coefficients for Land Uses ................................. 3 18 Table 3 10. Runoff EMCs for Acres Within a Watershed ......................... 3 20 Table 4 1. Regulatory Options Evaluated for Controlling Discharges from Construction Activities ........................................... 4 1 Table 4 2. Estimated TSS Loadings Reductions for Proposed Regulatory Options ...... 4 2 Table 4 3. Development Scenarios Used to Estimate Impacts of Regulatory Options .... 4 3 Table 4 4. Estimated Average In Stream TSS Concentrations Reduction ............. 4 4 Figures Figure 2 1. Ultimate Channel Enlargement .................................... 2 18 Figure 2 2. Altered Hydrograph in Response to Urbanization ..................... 2 19 Figure 2 3. Runoff Coefficient Versus Impervious Cover ........................ 2 20 Figure 2 4. Baseflow in Response to Urbanization: Nassau County, NY ............. 2 23 Figure 2 5. Increased Shear Stress from an Urban Hydrograph .................... 2 24 Figure 2 6. Sediment Production from Construction Sites ........................ 2 25 Figure 2 7. Drainage Network of Rock Creek, Maryland, Before and After Urbanization. ............................................. 2 26 Environmental Assessment of Construction and Development Proposed Effluent Guidelines June 2002 iv Figure 2 8. Channel Enlargement in Watts Branch, Maryland ..................... 2 27 Figure 2 9. Large Woody Debris as a Function of Watershed Imperviousness ........ 2 28 Figure 2 10. Stream Temperature Increase in Response to Urbanization .............. 2 29 Figure 3 1. Ecoregions for Stream Inventorying ................................. 3 5 Figure 3 2. Land Use Distribution of a Watershed ............................... 3 15 Environmental Assessment of Construction and Development Proposed Effluent Guidelines 1. The term impact is used to denote negative conditions related to elevated concentrations of pollutants, physical destruction or alteration of habitat by excessive flows, elevation of water temperature, and loss of fish spawning access due to new road crossings June 2002 1 1 Section 1 Introduction and Background 1.1 Introduction The U. S. Environmental Protection Agency (EPA) is proposing national effluent limitation guidelines for the construction and development (C& D) category. By establishing national standards, EPA intends to reduce the environmental impacts of construction site storm water discharges. This environmental assessment has been prepared to support the proposed rule by identifying and estimating the environmental benefits of implementing the proposal.

For purposes of the environmental assessment, construction is defined as the process by which land is converted from one land use to another. Hence, construction impacts are a result of how the land is converted, not a result of what the land becomes. 1 Land development is defined in this document as the conversion of land from a pre development condition such as rural land use to a post development condition such as urban land use. The impacts from the land development industry originate from the post development condition (what the land use becomes), which causes adverse environmental effects that were not present in the pre development condition.

Adverse environmental impacts attributable to the C& D industries have been well documented and include (but are not limited to) alteration of stream flow patterns, change in river channels, and reduction in the water quality of receiving waters as a result of increased generation and transport of sediment. Aquatic habitats also can be damaged as a result of reduced water quality and altered hydrology. These environmental impacts can in turn cause additional environmental and economic damage by increasing the frequency and magnitude of flooding events in vulnerable areas.

The purpose of this document is to describe the methods used to evaluate and quantify such impacts as they occur under the current regulatory framework and might occur under the proposed effluent guidelines. This report also presents estimates of the environmental benefits that would accrue from implementation of the proposed technology controls. As discussed later in the document, however, the environmental assessment and the associated Economic Analysis of the proposed rule (EPA, 2002) only partially capture the full range of potential benefits that would derive from implementing the proposed regulations. Not all categories of environmental impacts from C& D activities can be quantified and therefore some are not amenable to monetization procedures. These additional categories of environmental benefits are evaluated in only a qualitative manner. Environmental Assessment of Construction and Development Proposed Effluent Guidelines June 2002 1 2 The environmental assessment evaluates construction impacts for each of the three regulatory options considered in the proposal. As shown in Table 1 1, these options range from no new regulatory requirements (Option 3) to requirements for inspections and certifications of erosion and sediment controls and implementation of new storm water pollution prevention plans for certain sized sites.

Table 1 1. Regulatory Options Evaluated for Controlling Discharges from Construction Activities Option Description Option 1 ° Applicable to construction sites with one acre or more of disturbed land ° Operators required to:  Inspect site throughout land disturbance period  Certify that the controls meet the regulatory design criteria as applicable ° Amend NPDES regulations at 40 CFR Part 122 (no new effluent guideline regulations)

Option 2 ° Applicable to construction sites with five acres or more of disturbed land ° Operators required to:  Prepare storm water pollution prevention plan  Design, install, and maintain erosion and sediment controls  Inspect site throughout land disturbance period  Certify that the controls meet the regulatory design criteria as applicable ° Creates a new effluent guidelines category at 40 CFR Part 450 and amends Part 122 regulations Option 3 ° No new regulatory requirements The assessment, where appropriate, estimates reductions in environmental impacts attributable to EPA's proposed rule. To help the reader understand the estimated changes under the regulatory proposal, the document also summarizes the regulatory framework currently in place.

1.2 Organization of Environmental Assessment This document first provides background information on the current regulatory framework and summarizes how the proposed regulation would alter this framework. Section 2 provides additional background information on how the C& D industries affect the environment through generation of pollutants in storm water runoff and alteration of hydrology. A detailed discussion of the methodology used to estimate environmental impacts from the C& D industries is provided in Section 3. Section 4 presents EPA's estimates of environmental impacts of construction Environmental Assessment of Construction and Development Proposed Effluent Guidelines June 2002 1 3 activities under baseline conditions and under the various regulatory options evaluated for the proposed rule. Section 5 provides the references used in the analysis. The appendices are provided primarily for readers who seek further detail about how the methodology was developed.

1.3 Review of Regulatory History Related to C& D Category This subsection describes the federal and state regulations designed to control storm water discharges from the C& D industries. It describes the regulatory framework that is currently in place.

1.3.1 Clean Water Act Congress adopted the Clean Water Act (CWA) to "restore and maintain the chemical, physical, and biological integrity of the Nation's waters" (Section 101( a), 33 U. S. C. 1251( a)). To achieve this goal, the CWA prohibits the discharge of pollutants into navigable waters except in compliance with the statute. CWA section 402 requires "point source" discharges to obtain a permit under the National Pollutant Discharge Elimination System (NPDES). These permits are issued by EPA regional offices or authorized State agencies.

Following enactment of the Federal Water Pollution Control Amendments of 1972 (Public Law 92 500, October 18, 1972), EPA and the States issued NPDES permits to thousands of dischargers, both industrial (e. g. manufacturing, energy and mining facilities) and municipal (sewage treatment plants). In accordance with the Act, EPA promulgated effluent limitation guidelines and standards for many industrial categories, and these requirements are incorporated into the permits.

The Water Quality Act of 1987 (Public Law 100 4, February 4, 1987) amended the CWA. The NPDES program was expanded by defining municipal and industrial storm water discharges as point sources. Industrial storm water dischargers, municipal separate storm sewer systems and other storm water dischargers designated by EPA must obtain NPDES permits pursuant to section 402( p) (33 U. S. C. 1342( p)).

<IP_ADDRESS> NPDES Storm Water Permit Program EPA's initial storm water regulations, promulgated in 1990, identified construction as one of several types of industrial activity requiring an NPDES permit. These "Phase I" storm water regulations require operators of large construction sites to apply for permits (40 CFR 122.26( b)( 14)( x)). A large site construction activity is one that: ° will disturb five acres or greater; or Environmental Assessment of Construction and Development Proposed Effluent Guidelines June 2002 1 4 ° will disturb less than five acres but is part of a larger common plan of development or sale whose total land disturbing activities total five acres or greater (or is designated by the NPDES permitting authority); and ° will discharge storm water runoff from the construction site through a municipal separate storm sewer system (MS4) or otherwise to waters of the United States. The Phase II storm water rule, promulgated in 1999, generally extends permit coverage to sites one acre or greater (40 CFR 122.26( b)( 15)).

In addition to requiring permits for construction site discharges, the NPDES regulations require permits for certain MS4s. The local governments responsible for the MS4s must operate a storm water management program. The local programs regulate a variety of business activities that affect storm water runoff, including construction.

1.3.2 Other State and Local Government Storm Water Requirements States and municipalities may have other requirements for flood control, erosion and sediment (E& S) control, and in many cases, storm water quality. Many of these provisions were enacted before the promulgation of the EPA Phase I storm water rule. All states have laws for E& S control, and these are often implemented by MS4s. A summary of existing state and local requirements is provided in the Development Document (EPA, 2002a). Key control measures used by states and municipal/ regional authorities in these programs include:

° Storm water controls designed for peak discharge control ° Storm water controls designed for water quality control ° Storm water controls designed for flood control ° Specified depths of runoff for water quality control ° Percent reduction of loadings for water quality control (primarily solids and sediments) ° Numeric effluent limits for water quality control (primarily total suspended sediments, settleable solids, or turbidity) ° Control measures for biological or habitat protection ° Control measures for physical in stream condition controls (primarily streambed and stream bank erosion).

Control measures used to reduce pollutants entering water bodies are commonly required during the construction (land disturbance) phase. Post construction requirements for pollutant reductions are generally broader and more stringent. Typically, water quantity control measures for peak discharges and runoff volume controls that apply to post development conditions are not required during the construction phase. Environmental Assessment of Construction and Development Proposed Effluent Guidelines June 2002 2 1 Section 2 Categories of Reported Impacts and Pollutants 2.1 Introduction Construction and land development activities can generate a broad range of environmental impacts by introducing new sources of contamination and by altering the physical characteristics of the affected land area. In particular, these activities can result in both short and long term adverse impacts on surface water quality in streams, rivers, and lakes in the affected watershed by increasing the loads of various pollutants in receiving water bodies, including sediments, metals, organic compounds, pathogens, and nutrients. Groundwater also can be adversely affected through diminished recharge capacity. Other potential impacts include the physical alteration of existing streams and rivers due to the excessive flow and velocity of storm water runoff.

Construction activities typically involve excavating and clearing existing vegetation. During the construction period, the affected land is usually denuded and the soil compacted, leading to increased storm water runoff and high rates of erosion. If the denuded and exposed areas contain hazardous contaminants, they can be carried at increased rates to surrounding water bodies by storm water runoff. Although the denuded construction site is only a temporary state (usually lasting less than 6 months), the landscape is permanently altered even after the land has been restored by replanting vegetation. For example, a completed construction site typically has a greater proportion of impervious surface than the predevelopment site, leading to changes in the volume and velocity of storm water runoff. Changes in land use might also lead to new sources of pollution, such as oils and metals from motor vehicles, nutrients and pesticides from landscape maintenance, and pathogens from improperly installed or failing septic tanks. Increased pollutant loads are particularly evident when land development takes place in previously undeveloped environments. Together the short term impacts from construction activities and the long term impacts of development can profoundly change the environment.

The following subsections describe how pollutants associated with construction activities and land development storm water discharges can adversely affect the environment. Potential effects include impairment of water quality, destruction of aquatic life habitats, and enlargement of flood plains. To the extent possible, this analysis distinguishes between environmental impacts generated during construction and environmental impacts from post development activities. Although in most cases the differences are in magnitude and duration (e. g., sediment runoff), environmental impairment from such contaminants as pathogens are more likely to be associated with the overall urbanization of a watershed than with the types of activities that take place during construction. The discussion of environmental impacts first evaluates the impacts of contaminated runoff and then focuses on the physical impacts of construction and land development. Environmental Assessment of Construction and Development Proposed Effluent Guidelines June 2002 2 2 2.2 Pollutants Associated With Construction and Land Development Storm Water Runoff This subsection describes pollutants associated with construction and land development storm water runoff. The description does not represent the complete suite of contaminants that can be found in the runoff but focuses instead on those that are the most prevalent and of greatest concern to the environment. These pollutants include sediment, metals, poly aromatic hydrocarbons (PAHs), oil, grease, and pathogens.

2.2.1 Sediment Sediment is an important and ubiquitous constituent in urban storm water runoff. Surface runoff and raindrops detach soil from the land surface, resulting in sediment transport into streams. Sediment can be divided into three distinct subgroups: suspended solids, turbidity, and dissolved solids.

Total suspended solids (TSS) are a measure of the suspended material in water. The measurement of TSS in urban storm water allows for estimation of sediment transport, which can have significant effects locally and in downstream receiving waters.

Turbidity is a function of the suspended solids and is a measure of the ability of light to penetrate the water. Turbidity can exhibit control over biological functions, such as the ability of submerged aquatic vegetation to receive light and the ability of fish to breathe dissolved oxygen through their gills.

Total dissolved solids are a measure of the dissolved constituents in water and are a primary indication of the purity of drinking water.

<IP_ADDRESS> Sources of Sediment Construction Sites Erosion from construction sites can be a significant source of sediment pollution to nearby streams. A number of studies have shown high concentrations of TSS in runoff from construction sites, and results from these studies are summarized in Table 2 1. One study, conducted in 1986, calculated that construction sites are responsible for an estimated export of 80 million tons of sediment into receiving waters each year (Goldman, 1986, cited in CWP, 2000). On a unit area basis, construction sites export sediment at 20 to 1,000 times the rate of other land uses (CWP, 2000). Environmental Assessment of Construction and Development Proposed Effluent Guidelines June 2002 2 3 Table 2 1. Studies of Soil Erosion as TSS From Construction Sites Site Mean Inflow TSS Concentration (mg/ L) Source Seattle, Washington 17,500 Horner, Guerdy, and Kortenhoff, 1990 SR 204 3,502 Horner, Guerdy, and Kortenhoff, 1990 Mercer Island 1,087 Horner, Guerdy, and Kortenhoff, 1990 RT1 359 Schueler and Lugbill, 1990 RT2 4,623 Schueler and Lugbill, 1990 SB1 625 Schueler and Lugbill, 1990 SB2 415 Schueler and Lugbill, 1990 SB4 2,670 Schueler and Lugbill, 1990 Pennsylvania Test Basin 9,700 Jarrett, 1996 Georgia Model 1,500 – 4,500 Sturm and Kirby, 1991 Maryland Model 1,000 – 5,000 Barfield and Clar, 1985 Uncontrolled Construction Site Runoff (MD) 4,200 York and Herb, 1978 Austin, Texas 600 Dartiguenave, EC Lille, and Maidment, 1997 Hamilton County, Ohio 2,950 Islam, Taphorn, and Utrata Halcomb, 1998 Mean TSS (mg/ L) 3,681 NA Post Development Conditions as a Source of Sediment Sediment sources in urban environments include bank erosion, overland flow, runoff from exposed soils, atmospheric deposition, and dust (Table 2 2). Streets and parking lots accumulate dirt and grime from the wearing of the street surface, exhaust particulates, "blown on" soil and organic matter, and atmospheric deposition. Lawn runoff primarily contains soil and organic matter. Source area monitoring data from Bannerman (1993), Waschbusch (2000), and Steuer (1997) are shown in Table 2 3. Hot spots were identified for the transport of sediment from the urban land surface, and they include streets, parking lots, and lawns. Environmental Assessment of Construction and Development Proposed Effluent Guidelines June 2002 2 4 Table 2 2. Sources of Sediment in Urban Areas Source Area Loading Bank erosion ° Up to 75 percent in California and Texas studies Overland flow ° Lawns  average value of geometric means from 4 studies: 201 mg/ L Runoff from areas with exposed soils ° Average value: 3,640 mg/ L Blown on material and organic matter ° May account for as much as 35 to 50 percent in urban areas Bannerman et al., 1993; Dartinguenave et al., 1997; Schueler, 1987; Steuer et al., 1997; Trimble, 1997; Waschbusch et al., 2000;

Table 2 3. Source Area Concentrations for TSS in Urban Areas Source Area TSS (mg/ L) a TSS (mg/ L) b TSS (mg/ L) c Monroe Basin Harper Basin Commercial parking lot 110 58 51 High traffic street 226 232 65 Medium traffic street 305 326 51 Low traffic street 175 662 68 69 Commercial rooftop 24 15 18 Residential rooftop 36 27 15 17 Residential driveway 157 173 34 Residential lawn 262 397 59 122 a Steuer et al., 1997. b Bannerman et al., 1993. c Waschbusch et al., 2000.

Parking lots and streets are responsible not only for high concentrations of sediment but also for high runoff volumes. Normally about 90 percent of the water that falls on pavement is converted to surface runoff, whereas roughly 5 to15 percent of the water that falls on lawns is converted to surface runoff (Schueler, 1987). The source load and management model (SLAMM; Pitt and Voorhes, 1989) evaluates runoff volume and concentrations of pollutants from different urban Environmental Assessment of Construction and Development Proposed Effluent Guidelines June 2002 2 5 land uses and predicts loads to the stream. When used in the Wisconsin and Michigan subwatersheds, the model estimated that parking lots and streets were responsible for more than 70 percent of the TSS delivered to the stream (Steuer, 1997; Waschbusch et al., 2000). Because basin water quality measurements were taken at pipe outfalls, bank erosion was not accounted for in the studies.

Sediment load is due to erosion caused by an increased magnitude and frequency of flows brought on by urbanization (Allen and Narramore, 1985; Booth, 1990; Hammer, 1972; Leopold, 1968). Stream bank studies by Dartinguenave et al. (1997) and Trimble (1997) determined that stream banks are large contributors of sediment in urban streams. Trimble (1997) used direct measurements of stream cross sections, sediment aggradation, and suspended sediment to determine that roughly 66.7 percent of the sediment load in San Diego Creek was a result of bank erosion. Dartiguenave et al. (1997) used a GIS based model developed in Austin, Texas, to determine the effects of stream channel erosion on sediment loads. By effectively modeling the pollutant loads on the land surface and by monitoring the actual in stream loads at U. S. Geological Survey (USGS) gauging stations, they were able to determine that over 75 percent of the sediment load came from the stream banks.

<IP_ADDRESS> Receiving Waters Impacts Sediment transport and turbidity can affect habitat, water quality, temperature, and pollutant transport, and can cause sedimentation in downstream receiving waters (Table 2 4). Suspended sediment and its resulting turbidity can reduce light for submerged aquatic vegetation. In addition, deposited sediment can cover and suffocate benthic organisms like clams and mussels, cover habitat for substrate oriented species in urban streams, and reduce storage in reservoirs. Pollutants such as hydrocarbons and metals tend to bind to sediment and are transported with storm flow (Crunkilton et al., 1996; Novotny and Chesters, 1989). Increased turbidity also can cause stream warming by reflecting radiant energy (Kundell and Rasmussen, 1995). Environmental Assessment of Construction and Development Proposed Effluent Guidelines June 2002 2 6 Table 2 4. Sediment Impacts on Receiving Waters Resource Affected Impacts of Sediment Indicator Source Streams Loss of sensitive species and a decrease in fish and macroinvertebrate diversity communities GA loss of sensitive species at 25 NTU Kundell and Rasmussen, 1995 Clogging of gills and loss of habitat Leopold, 1973 Decreased flow capacity in streams Maryland decreased flow capacity. Increased overbank flows Barrett and Molina, 1998 Interference with water quality processes. Affects transport of contaminants MacRae and Marsalek, 1992 Wetlands Deposition of sediment High accretion rates in a tidal wetland as a result of sediment transport in an urbanized watershed Pasternack, 1998 Loss of sensitive species: amphibians, plants Loss of amphibian species Horner, 1996 Loss of seven wetland/ SAV plant species since European development Hilgartner, 1986 Reservoirs Turbidity results in increased costs of treatment for drinking water more abatement costs at >5 NTU McCutcheon et al., 1993 Sedimentation results in decreased storage Beaches Turbidity reduces aesthetic value Kundell and Rasmussen, 1995 Sedimentation can result in increased accretion rates in wetlands and change plant community structure Environmental Assessment of Construction and Development Proposed Effluent Guidelines Table 2 4. Sediment Impacts on Receiving Waters Resource Affected Impacts of Sediment Indicator Source June 2002 2 7 Estuaries Sedimentation Pasternack, 1998 Turbidity Livingston, 1996 Reduced light attenuation can lead to a loss of submerged aquatic vegetation (SAV) Schiff, 1996 Mackiernan et al., 1996 SAV losses due to sediments and eutrophication Short and WyllieEcheverria 1996 SAV losses in NE Orth and Moore, 1983 Essential habitat requirements for SAV include light attenuation, dissolved inorganic nitrogen, phosphorus and chlorophyl a Stevenson et al., 1993 Loss of seven wetland/ SAV plant species since European settlement Hilgartner, 1986 2.2.2 Metals Many toxic metals can be found in urban storm water, although only metals such as zinc, copper, lead, cadmium, and chromium are of concern because of their prevalence and potential for environmental harm. These metals are generated by motor vehicle exhaust, the weathering of buildings, the burning of fossil fuels, atmospheric deposition, and other common urban activities.

Metals can bioaccumulate in stream environments, resulting in plant growth inhibition and adverse health effects on bottom dwelling organisms (Masterson and Bannerman, 1995). Generally the concentrations found in urban storm water are not high enough for acute toxicity (Field and Pitt, 1990). Rather, it is the cumulative effect of the concentration of these metals over time and the buildup in the sediment and animal tissue that are of greater concern. Environmental Assessment of Construction and Development Proposed Effluent Guidelines June 2002 2 8 <IP_ADDRESS> Sources of Metal Runoff Construction Sites Construction sites are not thought to be important sources of metal contamination. Runoff from such sites could have high metals contents if the soil is already contaminated. Construction activities alone do not result in metal contamination.

Post Development Conditions as a Source of Metals Post development conditions create significant sources of metal runoff in the urban environment, including streets, parking lots, and rooftops. Table 2 5 summarizes the major sources of metal runoff by metal type. Copper can be found in high concentrations on urban streets as a result of the wear of brake pads that contain copper. A study in Santa Clara, California, estimated that 50 percent of the copper released is from brake pads (Woodward Clyde, 1992). Sources of lead include atmospheric deposition and diesel fuel, which are found consistently on streets and rooftops. Zinc in urban environments is a result of the wear of automobile tires (an estimated 60 percent of the total zinc in the Santa Clara study), paints, and the weathering of galvanized gutters and downspouts. Source area concentrations estimated by researchers in Wisconsin and Michigan are presented in Table 2 6. Actual concentrations vary considerably, and highconcentration source areas vary from study to study. A study using SLAMM for an urban watershed in Michigan estimated that most of the zinc, copper, and cadmium was a result of runoff from urban parking lots, driveways, and residential streets (Steuer, 1997). Environmental Assessment of Construction and Development Proposed Effluent Guidelines June 2002 2 9 Table 2 5. Metal Sources and Hot Spots in Urban Areas Metal Sources Hot Spots Zinc Tires, fuel combustion, galvanized pipes and gutters, road salts Estimate of 60% from tires a Parking lots, rooftops, and streets Copper Auto brake linings, pipes and fittings, algacides, and electroplating Estimate of 50% from brake pads a Parking lots, commercial roofs, and streets Lead Diesel fuel, paints, and stains Parking lots, rooftops, and streets Cadmium Component of motor oil; corrodes from alloys and plated surfaces Parking lots, rooftops, and streets Chromium Found in exterior paints; corrodes from alloys and plated surfaces More frequently found in industrial and commercial runoff a Woodward Clyde, 1992 (Santa Clara, CA, study) Sources: Barr, 1997; Bannerman et al., 1993; Steuer, 1997 Environmental Assessment of Construction and Development Proposed Effluent Guidelines June 2002 2 10 Table 2 6. Metal Source Area Concentrations in Urban Areas (in ug/ L)

Source Area Diss. Zinc Total Zinc Diss. Copper Diss. Copper Total Copper Diss. Lead Diss. Lead Total Lead Total Lead Total Lead Citation (a) (b) (a) (b) (b) (a) (c) (a) (c) (b)

Commercial parking lot 64 178 10.7 9 15 40 22 High traffic street 73 508 11.2 18 46 2.1 1.7 37 25 50 Mediumtraffic street 44 339 7.3 24 56 1.5 1.9 29 46 55 Low traffic street 24 220 7.5 9 24 1.5 0.5 21 10 33 Commercial rooftop 263 330 17.8 6 9 20 48 9 Residential rooftop 188 149 6.6 10 15 4.4 25 21 Residential driveway 27 107 11.8 9 17 2.3 52 17 Residential lawn na 59 na 13 13 na na na Basin outlet 23 203 7.0 5 16 2.4 49 32 na : not available Sources: (a) Steuer 1997; (b) Bannerman 1993; (c) Waschbusch, 1996, cited in Steuer, 1997 <IP_ADDRESS> Metals Impacts on Receiving Waters Downstream effects of metal transported to receiving waters, such as lakes and estuaries, have been studied extensively. Selected studies on metal impacts on receiving waters are summarized in Table 2 7. Although evidence exists for the buildup of metals in deposited sediments in receiving waters and for bioaccumulation in aquatic species (Bay et al., 2000; Livingston, 1996), specific effects of these concentrations on submerged aquatic vegetation and other biota are not well understood. Environmental Assessment of Construction and Development Proposed Effluent Guidelines June 2002 2 11 Table 2 7. Metals Impacts on Receiving Waters Resource Affected Impacts of Metals Evidence Streams ° Chronic toxicity due to in stream concentrations and accumulation in sediment ° Bioaccumulation in aquatic species ° Acute toxicity at certain concentrations Chronic toxicity increased during longerduration studies, i. e., 7/ 14/ 21 day studies (Crunkilton, 1996); Delayed toxicity (Ellis, 1986/ 1987); Baseflow toxicity (Mederios, 1983); Resuspension of metals during storms accounting for some toxicological effects (Heaney and Huber, 1978); Bioaccumulation in crayfish (Masterson & Bannerman, 1994)

Reservoirs/ Lakes ° Accumulation of metals in sediment Bioaccumulation levels in bottom feeding fish were found to be influenced by the metal levels of the bottom sediments of storm water ponds (Campbell, 1995).

Estuaries ° Accumulation of metals in sediment ° Loss of SAV Tampa Bay (Livingston, 1996); San Diego (Schiff 1996); SAV losses in northeast San Francisco Bay (Orth and Moore, 1983)

2.2.3 PAHs, and Oil and Grease Petroleum based substances such as oil and grease and poly aromatic hydrocarbons (PAHs) are found frequently in urban storm water. Many constituents of PAHs and oil and grease, such as pyrene and benzo[ b] fluoranthene, are carcinogens and toxic to downstream biota (Menzie Cura and Assoc., 1995). Oil and grease and PAHs normally travel attached to sediment and organic carbon. Downstream accumulation of these pollutants in the sediments of receiving waters such as streams, lakes, and estuaries is of concern.

<IP_ADDRESS> Sources of PAHs, and Oil and Grease Construction Sites Construction activities during site development are not believed to be major contributors of these contaminants to storm water runoff. Improper operation and maintenance of construction equipment at construction sites, as well as poor housekeeping practices (e. g., improper storage of oil and gasoline products), could lead to leakage or spillage of products that contain hydrocarbons, but these incidents would likely be small in magnitude and managed before offsite contamination could occur. Environmental Assessment of Construction and Development Proposed Effluent Guidelines June 2002 2 12 Post Development Conditions as a Source of PAHs, and Oil and Grease In most storm water runoff, concentrations of PAHs and oil and grease are typically below 5 mg/ L but concentrations tend to increase in commercial and industrial areas. Hot spots for these pollutants in the urban environment include gas stations, commuter parking lots, convenience stores, residential parking areas, and streets (Schueler, 1994). Schueler and Shepp (1993) found concentrations of pollutants in oil/ grit separators in the Washington Metropolitan area and determined that gas stations had significantly higher concentrations of hydrocarbons and a greater presence of toxic compounds than streets and residential parking lots. A study of source areas in an urban watershed in Michigan (which excluded gas stations) showed that high concentrations from commercial parking lots contributed 64 percent of the estimated hydrocarbon loads (Steuer et al., 1997).

<IP_ADDRESS> Receiving Water Impacts Toxicological effects from PAHs and oil and grease are assumed to be reduced by their attachment to sediment (lessened availability) and by photodegradation (Schueler, 1994). Evidence of possible impacts on the metabolic health of organisms exposed to PAHs and of bioaccumulation in streams and other receiving waters does not exist (Masterson and Bannerman, 1994; MacCoy and Black, 1998); however, crayfish from Lincoln Creek, analyzed in the Masterson and Bannerman study, had a PAH concentration of 360 micrograms per kilogram— much higher than the concentration known to be carcinogenic. The crayfish in the control stream did not have detectable levels of PAHs. Known effects of PAHs on receiving waters are summarized in Table 2 8. Long term effects of PAHs in sediments of receiving waters call for additional study. Environmental Assessment of Construction and Development Proposed Effluent Guidelines June 2002 2 13 Table 2 8. Effects of PAHs and Oil and Grease on Receiving Waters Resource Affected Impacts of PAHs and Oil and Grease Citations Streams ° Possible chronic toxicity due to in stream concentrations and accumulation in sediment ° Bioaccumulation in aquatic species ° Acute toxicity at certain concentrations Bioaccumulation in crayfish tissue studies (Masterson and Bannerman, 1994); Potential metabolic costs to organisms (Crunkilton et al., 1996); delayed toxicity (Ellis, 1986/ 1987); Baseflow toxicity (Mederios, 1983)

Reservoirs ° Accumulation of PAHs in sediment Sediment contamination may result in a decrease in benthic diversity and transfer of PAHs to fish tissue (Schueler, 2000 CWP); Elevated levels of PAHs found in pond muck layer (Gavens et al., 1982)

Estuaries ° Accumulation of PAHs in sediment ° Potential loss of SAV ° Accumulation of PAHs in fish and shellfish tissue Tampa Bay (Livingston, 1996); San Diego, San Francisco Bay (Schiff, 1996)

2.2.4 Pathogens Microbes, or living organisms undetectable by the naked eye, are commonly found in urban storm water. Although not all microbes are harmful, several species such as the pathogens Cryptosporidium and Giardia can directly cause diseases in humans (pathogens). The presence of bacteria such as fecal coliform bacteria, fecal streptococci, and Escherichia coli indicates a potential health risk (indicators). High levels of these bacteria may result in beach closings, restrictions on shellfish harvest, and increased treatment for drinking water to decrease the risk of human health problems.

<IP_ADDRESS> Sources of Pathogens Construction Sites Construction site activities are not believed to be major contributors to pathogen contamination of surface waters. The only potential known source of pathogens from construction sites are portable septic tanks used by construction workers. These systems, however, are typically selfcontained and are not connected to the land surface. Any leaks from them would likely be identified and addressed quickly. Environmental Assessment of Construction and Development Proposed Effluent Guidelines June 2002 2 14 Post Development Conditions as a Source of Pathogen Runoff Coliform sources include pets, humans, and wild animals. Source areas in the urban environment for direct runoff include lawns, driveways, and streets. Dogs have high concentrations of coliform bacteria in their feces and have a tendency to defecate in close proximity to impervious surfaces (Schueler, 1999). Many wildlife species also have been found to contribute to high fecal concentrations. Essentially, any species that is present in significant numbers in a watershed is a potential pathogen source. Source identification studies, using methods such as DNA fingerprinting, have attributed high coliform levels to such species as rats in urban areas, ducks and geese in storm water ponds, dogs, and even raccoons (Blankenship, 1996; Lim and Oliveri, 1982; Pitt et al., 1988; Samadapour and Checkowitz, 1998).

Indirect surface storm water runoff sources include leaking septic systems, illicit discharges, sanitary sewer overflows (SSOs), and combined sewer overflows (CSOs). These sources have the potential to deliver high concentrations of coliforms to receiving waters. Illicit connections from businesses and homes to the storm drainage system can discharge sewage or washwater into receiving waters. Leaking septic systems are estimated to constitute 10 to 40 percent of all systems. Inspection is the best way to determine whether a system is failing (Schueler, 1999).

There is also evidence that these bacteria can survive and reproduce in stream sediments and in storm sewers. During a storm event, they are resuspended and add to the in stream bacteria load. Source area studies reported that end of pipe concentrations were an order of magnitude higher than any source area on the land surface; therefore, it is likely that the storm sewer system itself acts as a source (Bannerman, 1993; Steuer et al., 1997). Resuspension of fecal coliform bacteria from fine stream sediments during storm events has been reported in New Mexico (NMSWQB, 1999). The sediments in the storm sewer system and in streams may be significant contributors to the fecal coliform load. This area of research certainly warrants more attention to determine whether these sources can be quantified and remediated.

Giardia and Cryptosporidium in urban storm water are also a concern. There is evidence that urban watersheds and storm events might have higher concentrations of Giardia and Cryptosporidium than other surface waters (Stern, 1996). (See Table 2 9.) The primary sources of these pathogens are humans and wildlife. Although Cryptosporidium is found in less than 50 percent of storm water samples, data suggest that high Cryptosporidium values may be a concern for drinking water supplies. Both pathogens can cause serious gastrointestinal problems in humans (Bagley et al., 1998). Environmental Assessment of Construction and Development Proposed Effluent Guidelines June 2002 2 15 Table 2 9. Percentage Detection of Giardia Cysts and Cryptosporidium Oocysts in Subwatersheds and Wastewater Treatment Plant Effluent in the New York City Water Supply Watersheds Source Water Sampled (No. of sources/ No. of samples) Percent Detection Total Giardia Confirmed Giardia Total Cryptosporidium Confirmed Cryptosporidium Wastewater effluent (8/ 147) 41.5 12.9 15.7 5.4 Urban subwatershed (5/ 78) 41.0 6.4 37.2 3.9 Agricultural subwatershed (5/ 56) 30.4 3.6 32.1 3.6 Undisturbed subwatershed (5/ 73) 26.0 0.0 9.6 1.4 Source: Stern et al., 1996.

<IP_ADDRESS> Receiving Water Impacts Fecal coliform bacteria, fecal streptococci, and E. coli are consistently found in urban storm water runoff. Their presence indicates that human or other animal waste is also present in the water and that other harmful bacteria, viruses, or protozoans might be present as well. Concentrations of these indicator organisms in urban storm water are highly variable even within a given monitoring site. Data for fecal coliform bacteria illustrate this variability: site concentrations range from 10 to 500,000 most probable number per 100 milliliters (MPN/ 100mL) (Schueler, 1999).

Concentrations in urban storm water typically far exceed the 200 MPN/ 100 mL threshold set for human contact recreation. The mean concentration of fecal coliform bacteria in urban storm water for 34 studies across the United States was 15,038 MPN/ 100mL (Schueler, 1999). Another national database of 1,600 samples (mostly Nationwide Urban Runoff Program data collected in the 1980s), estimates the mean concentration at 20,000 MPN/ 100 mL (Pitt, 1998). Fecal streptococci concentrations for 17 urban sites had a mean of 35,351 MPN/ 100 mL (Schueler, 1999). Transport occurs primarily as a result of direct surface runoff, failing septic systems, SSOs, CSOs, and illicit discharges.

Human health can be affected by bacterial impacts on receiving waters when bacteria standards for water contact recreation, shellfish consumption, or drinking water are violated. Epidemiological studies from Santa Monica Bay have documented frequent sickness in people who swim near outfalls (SMBRP, 1996). Documented illnesses include fever, ear infections, gastroenteritis, nausea, and flu like symptoms. Table 2 10 describes the effects of bacteria and protozoan problems on different receiving waters. Environmental Assessment of Construction and Development Proposed Effluent Guidelines June 2002 2 16 Table 2 10. Effects of Bacteria on Receiving Waters Resource Affected Impacts of Bacteria Citations Streams ° Human health issues More than 80,000 miles of streams and rivers in non attainment because of high fecal coliform levels (USEPA, 1998a)

Reservoirs ° Contamination of water supply Increased treatment cost of drinking water due to bacteria contamination (USEPA, 1996)

Beaches ° Human health issues More than 4,000 beach closings or advisories (USEPA, 1998b)

Estuaries ° Closing of shellfish beds ° Beach closings Nearly 4% of all shellfish beds restricted or conditional harvest due to high bacteria levels (NOAA 1992); More than 4,000 beach closings or advisories (USEPA, 1998b)

2.3 Physical Impacts of Construction and Land Development Activities This subsection describes the physical impacts of construction activities and development conditions, which include hydrologic, geomorphic, habitat structure, thermal, and direct channel impacts. These impacts are most visible on the urban stream. Construction and land development impacts on stream systems are described for each of these impact categories (Table 2 11). Site differences of these impacts are also noted. Because it is very difficult to differentiate between physical impacts that occur during construction and impacts that result from post development conditions, the discussion addresses physical impacts from a broader perspective. It does not differentiate between short term effects arising and site construction activities from long term impacts of post development conditions.

Physical changes are often precipitated by changes in hydrology that result when permeable rural and forest land is converted to impervious surfaces like pavement and rooftops and relatively impermeable urban soils. The conversion causes a fundamental change in the hydrologic cycle because a greater fraction of rainfall is converted to surface runoff. This change in the basic hydrologic cycle causes a series of other impacts (Table 2 11). The stream immediately begins to adjust its size, through channel erosion, to accommodate larger flows. Streams normally increase their cross sectional area by incising, widening, or often both. This process of channel response to increases in impervious surfaces accelerates sediment transport and destroys habitat. In addition, urbanization frequently leads to alteration of natural stream channels, such as Environmental Assessment of Construction and Development Proposed Effluent Guidelines June 2002 2 17 straightening or lining with concrete or rock to transport water away from developed areas more quickly. Finally, impervious surfaces also absorb heat, thereby increasing stream temperatures during runoff events.

Table 2 11. Physical Impacts on Streams Impact Class Specific Impacts Cause( s)

Hydrologic ° Increased runoff volume ° Increased peak flood flow ° Increased frequency of "bankfull" event ° Decreased baseflow ° Paving over natural surfaces ° Compaction of urban soils Geomorphic ° Sediment transport modified ° Channel area increase to accommodate larger flows ° Modified flows ° Channel modification ° Construction Habitat structure ° Stream embeddedness ° Loss of large woody debris ° Changes in pool/ riffle structure ° Modified flows ° Stream channel erosion ° Loss of riparian area Thermal ° Increased summer temperatures ° Heated pavement ° Storm water ponds ° Loss of riparian area Channel modification ° Channel hardening ° Fish blockages ° Loss of first and second order streams through storm drain enclosure ° Direct modifications to the stream system.

Figure 2 1 depicts the impacts of land development on the stream channel. At low levels of imperviousness, the stream has a stable channel, contains large woody debris, and has a complex habitat structure. As urbanization increases, the stream becomes increasingly unstable, increases its cross sectional area to accommodate increased flows, and loses habitat structure. In highly urbanized areas, stream channels are often modified through channelization or channel hardening. These physical changes are often accompanied by decreased water quality. Environmental Assessment of Construction and Development Proposed Effluent Guidelines June 2002 2 18 0.00 2.00 4.00 6.00 8.00 10. 00 12. 00 14. 00 0.0 10. 0 20. 0 30. 0 40. 0 50. 0 60. 0 70. 0 80. 0 Impervi ousness (%) Enlargement Ratio Figure 2 1. Ultimate Channel Enlargement (Claytor and Brown, 2000; MacRae and DeAndrea, 1999)

2.3.1 Hydrologic Impacts The increased runoff volume that results from land development alters the hydrograph, from its predeveloped condition (Figure 2 2). The resulting hydrograph accommodates larger flows with higher peak flow rates. Because storm drain conveyance systems (e. g., curbs, gutters) improve the efficiency with which water is delivered to the stream, the hydrograph is also characterized by a more rapid time of concentration and peak discharge. Finally, the flow in the stream between events can actually decrease because less rainfall percolates into the soil surface to feed the stream as baseflow. The resulting hydrologic impacts include increased runoff volume, increased flood peaks, increased frequency and magnitude of bankfull storms, and decreased baseflow volumes. Environmental Assessment of Construction and Development Proposed Effluent Guidelines June 2002 2 19 Figure 2 2. Altered Hydrograph in Response to Urbanization (Schueler, 1987)

<IP_ADDRESS> Increased Runoff Volume Impervious surfaces and urban land use changes alter infiltration rates and increase runoff volumes. Table 2 12 shows the difference in runoff volume between a meadow and a parking lot. The parking lot produces approximately 15 times more runoff than a meadow for the same storm event. Schueler (1987) demonstrated that runoff values increase significantly with the impervious surfaces in a watershed (Figure 2 3). The increased volume of water from urban areas is the greatest single cause of the negative impacts of urban storm water on receiving waters. The volume causes channel erosion and loss of habitat stability, as well as an increase in the total load of many pollutants such as sediment and nutrients. Environmental Assessment of Construction and Development Proposed Effluent Guidelines June 2002 2 20 Table 2 12. Hydrologic Differences Between a Parking Lot and a Meadow Hydrologic or Water Quality Parameter Parking Lot Meadow Runoff coefficient 0.95 0.06 Time of concentration (minutes) 4.8 14.4 Peak discharge, 2 yr, 24 h storm (ft 3 /s) 4.3 0.4 Peak discharge rate, 100 yr storm (ft 3 /s) 12.6 3.1 Runoff volume from 1 in. storm (ft 3 ) 3,450 218 Runoff velocity @ 2 yr storm (ft/ sec) 8 1.8 Key Assumptions: 2 yr, 24 hr storm = 3.1 in.; 100 yr storm = 8.9 in. Parking Lot: 100% imperviousness; 3% slope; 200 ft flow length; hydraulic radius = 0.03; concrete channel; suburban Washington `C' values Meadow: 1% impervious; 3% slope; 200 ft flow length; good vegetative condition; B soils; earthen channel Source: Schueler, 1987.

Figure 2 3. Runoff Coefficient Versus Impervious Cover (Schueler, 1987). Environmental Assessment of Construction and Development Proposed Effluent Guidelines June 2002 2 21 Construction activities also cause fundamental modifications in native soils. The compaction of urban soils and the removal of topsoil during construction decreases the infiltration capacity of the soil, resulting in a corresponding increase in runoff (Schueler, 2000). The bulk density is a measure of soil compaction, and Table 2 13 shows the values for different aspects of urbanization.

Table 2 13. Comparison of Bulk Density for Undisturbed Soils and Common Urban Conditions Undisturbed Soil Type or Urban Condition Surface Bulk Density (grams/ cubic centimeter)

Peat 0.2 to 0.3 Compost 1.0 Sandy Soils 1.1 to 1.3 Silty Sands 1.4 Silt 1.3 to 1.4 Silt Loams 1.2 to 1.5 Organic Silts/ Clays 1.0 to 1.2 Glacial Till 1.6 to 2.0 Urban Lawns 1.5 to 1.9 Crushed Rock Parking Lot 1.5 to 1.9 Urban Fill Soils 1.8 to 2.0 Athletic Fields 1.8 to 2.0 Rights of Way and Building Pads (85%) 1.5 to 1.8 Rights of Way and Building Pads (95%) 1.6 to 2.1 Concrete Pavement 2.2 Note: Shading indicates "urban" conditions. Source: Schueler, 2000. Environmental Assessment of Construction and Development Proposed Effluent Guidelines June 2002 2 22 <IP_ADDRESS> Increased Flood Peaks Increased flow volume increases peak flows. Data from Sauer et al. (1983) suggest that peak flow from large flood events (10 year to 100 year storm events) increases substantially with urbanization. The paper presents results of a survey of urban watersheds throughout the United States and predicts flood peaks based on watershed impervious cover and a "basin development factor" that reflects watershed characteristics such as the amount of curb and gutter, and channel modification. These data suggest that at 50 percent impervious cover, the peak flow for the 100 year event can be as much as twice that in an equivalent rural watershed. Data from Seneca Creek in Montgomery County, Maryland, suggest a similar trend. The watershed experienced significant growth during the 1950s and 1960s. Comparison of gauge records from 1961 to 1990 to those from 1931 to 1960 suggests that the peak 10 year flow event increased from 7,300 to 16,000 cfs, an increase of more than 100 percent (Leopold, 1994).

<IP_ADDRESS> Increased Frequency and Volume of Bankfull Flows Stream channel morphology is more influenced by frequent (1 to 2 year) storm events, or "bankfull" flows, than by large flood events. Hollis (1975) demonstrated that urbanization increased the frequency and magnitude of these smaller sized runoff events much more than the larger events. Data from this study suggest that streams increase their 2 year bankfull discharge by two to five times after development takes place. Many other studies have documented the increase in flow associated with impervious cover. A study by Guay (1995) compared the 2 year flows events before and after development in an urban watershed in Parris Valley, California, in the 1970s and in the 1990s. The impervious level of 9 percent in the 1970s increased to 22.5 percent by the 1990s. The 2 year discharge more than doubled from 646 cfs to 1,348 cfs. A 13 percent change in impervious cover resulted in a doubling of the 2 year peak flow.

A significant impact of land development is the frequency with which the bankfull event occurs. Leopold (1994) observed a dramatic increase in the frequency of the bankfull event in Watts Branch, an urban subwatershed in Rockville, Maryland. This watershed also experienced significant development between the 1950s and 1960s. A comparison of gauge records indicated that the bankfull storm event frequency increased from two to seven times per year from 1958 to 1987.

<IP_ADDRESS> Changes in Baseflow Land development results in a smaller recharge to groundwater and a corresponding decrease in stream flow during dry periods (baseflow). Only a small amount of evidence, however, documents this decrease in baseflow. Spinello and Simmons (1992) demonstrated that baseflow in two urban Long Island streams went dry seasonally as a result of urbanization (Figure 2 4). Another study in North Carolina could not conclusively determine that urbanization reduced baseflow in some streams in that area (Evett et al., 1994). It is important to note, however, that Environmental Assessment of Construction and Development Proposed Effluent Guidelines June 2002 2 23 groundwater flow paths are often complex. Water supplying baseflow feeding the stream can be from deeper aquifers or can originate in areas outside the surface watershed boundary. In arid and semiarid areas, watershed managers have reported that baseflow actually increases in urban areas. Increased infiltration from people watering their lawns and return flow from sewage treatment plants are two possible sources (Caraco, 2000). Recharge of clean groundwater is important in these communities, and managers would rather see clean water infiltrated than transported as surface water during storm events.

Figure 2 4. Baseflow in Response to Urbanization: Nassau County, NY (Spinello and Simmons, 1992)

2.3.2 Impacts on Geomorphology/ Sediment Transport Changes in hydrology, combined with additional sediment sources from construction and modifications to the stream channel, result in changes to the geomorphology of stream systems. These impacts include increased, and sometimes decreased, sediment transport and channel enlargement to accommodate larger flows.

<IP_ADDRESS> Increased Transport of Sediment The increased frequency of bankfull (1 to 2 year) storms causes more "effective work" (as defined by Leopold), causing greater sediment transport and bank erosion to take place within the channel. For the same storm event, the increased volume results in a greater amount of total stress above the critical shear stress required to move bank sediment (Figure 2 5). This effect is Environmental Assessment of Construction and Development Proposed Effluent Guidelines June 2002 2 24 compounded by the fact that smaller, more frequent storm events also cause flows in excess of the stress required to move sediment.

Figure 2 5. Increased Shear Stress from an Urban Hydrograph (Schueler, 1987)

The result of this change in effective work on stream banks is increased channel erosion. Studies in California (Trimble, 1997) and Austin, Texas (Dartinguenave et al., 1997) suggest that 60 to 75 percent of the sediment transport in urban watersheds is from channel erosion as compared to estimates of between 5 percent and 20 percent for rural streams (Collins et al., 1997; Walling and Woodward, 1995). If the sediment is not deposited in the channel at obstructions, it is transported downstream to receiving waters such as lakes, estuaries, or rivers. The result can be reduced storage and habitat due to the filling of these water bodies. Environmental Assessment of Construction and Development Proposed Effluent Guidelines June 2002 2 25 The clearing and grading of land for new construction at the outset of urbanization is another source of sediment in urban streams. Figure 2 6 (from Leopold, 1968) illustrates the difference in sediment from uncontrolled and controlled construction sites.

Figure 2 6. Sediment Production from Construction Sites (Leopold, 1968)

<IP_ADDRESS> Decreased Sediment Transport Decreased sediment transport off the land surface itself can result after urbanization as natural drainage and first order channels are replaced by storm drains and pipes (Figure 2 7). Channel erosion downstream might result when any export of sediment is not replaced by diminished upstream sediment supply. Ultimately, after significant erosion has taken place, the downstream channel will have adjusted to its post development flow regime and sediment transport will be reduced. Hence, the stability of the land surface and the piping of drainage channels limit storm water's exposure to sediment and reduce the sediment supply. Environmental Assessment of Construction and Development Proposed Effluent Guidelines June 2002 2 26 Figure 2 7. Drainage Network of Rock Creek, Maryland Before and After Urbanization (Dunne and Leopold, 1978)

<IP_ADDRESS> Increase in Size of Channel Channels increase their cross sectional area to respond to higher and more frequent urban flows. In post development urban watersheds, the increase in frequency of this channel forming event normally causes sediment transport to be greater than sediment supply. The channel widens (and/ or downcuts) in response to this change in sediment equilibrium (Allen and Narramore, 1985; Booth, 1990 Hammer, 1977; Morisawa and LaFlure, 1979;). Some research suggests that over time channels will reach an "ultimate enlargement," relative to a predeveloped condition, and that impervious cover can predict this enlargement ratio (MacRae and DeAndrea, 1999). This was shown in Figure 2 3, which depicted the relationship between ultimate stream channel enlargement and impervious cover for alluvial streams, based on data from Texas, Vermont, and Maryland. Figure 2 8 shows the channel expansion that has taken place and is projected to occur in Watts Branch near Rockville, Maryland, in response to urbanization. Environmental Assessment of Construction and Development Proposed Effluent Guidelines June 2002 2 27 0 1 2 3 4 5 6 7 8 9 10 0 5 10 15 20 25 30 35 40 45 Cross Section Stations (ft)  Looking Downstream Elevation (ft msl) Historic Section Curr ent Section Bankfull Depth Ultimate Section ? Historic c ross section Current cross section Ultimate c ross section ?

Figure 2 8. Channel Enlargement in Watts Branch, Maryland (Schueler, 1987) Note: Cross sections have been overlaid for illustration purposes only. Actual sections do not share the same datum.

Stream channels expand by incision, widening, or both. Incision occurs when the stream downcuts and the channel expands in the vertical direction. Widening occurs when the sides of the channel erode and the channel expands horizontally. Either method results in increased transport of sediment downstream and degradation of habitat. Channel incision is often limited by grade control from bedrock, large substrate, bridges, or culverts. These structures impede the downward erosion of the stream channel and limit incision. In substrates such as sand, gravel, and clay, however, stream incision can be of greater concern (Booth, 1990).

Channel widening more frequently occurs when streams have grade control and the stream cuts into its banks to expand its cross sectional area. Urban channels frequently have artificial grade control due to the frequent culverts and road crossings. These are often areas where sediment can accumulate as a result of undersized culverts and bridge crossings.

2.3.3 Changes in Habitat Structure Land development results in many changes in habitat structure, including embeddedness, decreased riffle/ pool quality, and loss of large woody debris (LWD). Increased sedimentation due to clearing and grading during construction resulting from bank erosion can significantly reduce the amount of habitat for substrate oriented species.

<IP_ADDRESS> Embeddedness Increased sediment transport from construction and land development can fill the interstitial spaces between rocks and riffles, which are important habitat for macroinvertebrates and fish Environmental Assessment of Construction and Development Proposed Effluent Guidelines June 2002 2 28 species, such as darters and sculpins. The stream bottom substratum is a critical habitat for trout and salmon egg incubation and embryo development (May et al., 1997).

<IP_ADDRESS> Large Woody Debris (LWD)

The presence and stability of LWD is a fundamental habitat parameter. LWD can form dams and pools, trap sediment and detritus, provide stabilization to stream channels, dissipate flow energy, and promote habitat complexity (Booth et al., 1996). For example, depending on the size of the woody debris and the stream, the debris can create plunge, lateral, scour, and backwater pools, short riffles, undercut banks, side channels, and backwaters, and create different water depths (Spence et al., 1996). The runoff generated in urban watersheds from small storms can be enough to transport LWD. Maxted et al. (1994) found that woody debris were typically buried under sand and silt in urban streams. In addition, the clearing of riparian vegetation limits an important source of large woody debris. Horner et al. (1996) present evidence from the Pacific Northwest (Figure 2 9) that LWD in urban streams decreases with increased imperviousness.

Figure 2 9. Large Woody Debris as a Function of Watershed Imperviousness (Horner et al., 1996) Environmental Assessment of Construction and Development Proposed Effluent Guidelines June 2002 2 29 <IP_ADDRESS> Changes in Stream Features Habitat diversity is a key factor in maintaining a diverse and well functioning aquatic community. The complexity of the habitat results in increased niches for aquatic species. Sediment and increases in flow can reduce the residual depths in pools and decrease the diversity of habitat features such as pools, riffles, and runs. Richey (1982) and Scott et al. (1986) reported an increase in the prevalence of glides and a corresponding altered pool/ riffle sequence due to urbanization.

2.3.4 Thermal Impacts Summer in stream temperatures have been shown to increase significantly (5 to 12 degrees) in urban streams because of direct solar radiation, runoff from heat absorbing pavement, and discharges from storm water ponds (Galli, 1991). Increased water temperatures can prevent temperature sensitive species from surviving in urban streams. Figure 2 10 shows the increase in water temperature resulting from urbanization.

Figure 2 10. Stream Temperature Increase in Response to Urbanization (Galli, 1991)

Water temperature in headwater streams is strongly influenced by local air temperatures. Galli (1991) reported that stream temperatures throughout the summer are higher in urban watersheds, and the degree of warming appears to be directly related to the imperviousness of the contributing watershed. Over a 6 month period, five headwater streams in the Maryland Piedmont that have different levels of impervious cover were monitored. Each urban stream had Environmental Assessment of Construction and Development Proposed Effluent Guidelines June 2002 2 30 mean temperatures that were consistently warmer than that of a forested reference stream, and the size of the increase appeared to be a direct function of watershed imperviousness. Other factors, such as a lack of riparian cover and ponds, were also shown to amplify stream warming, but the primary contributing factor appeared to be watershed impervious cover.

2.3.5 Direct Channel Impacts <IP_ADDRESS> Channel Straightening and Hardening/ Reduction in First Order Streams Channel straightening and hardening includes the addition of riprap or concrete to the channel, the straightening of natural channels, and the piping of first order and ephemeral streams. Although this conversion process often becomes necessary to control runoff from urbanized areas, adverse impacts often occur downstream. In a national study of urban watersheds in 269 gauged basins, Sauer et al. (1983) determined that channel straightening and channel lining (hardening)— along with the percentage of curbs and gutters, streets, and storm sewers— were the dominant land use variables affecting storm flow. These variables all affect the efficiency with which water is transported to the stream channel. Maintaining this efficiency increases the velocities needed for storm water to exceed critical shear stress velocities, eroding the channel. These factors also considerably degrade any natural habitat for stream biota.

<IP_ADDRESS> Fish Blockages Infrastructure associated with urbanization— such as bridges, dams, and culverts— can have a considerable effect on the ability of fish to move freely upstream and downstream in the watershed. This in turn can have localized effects on small streams, where nonmigratory fish species can be inhibited by the blockage from recolonizing areas after acutely toxic events. Anadromous fish species such as shad, herring, salmon, and steel head also can be blocked from making the upstream passage that is critical for their reproduction.

2.3.6 Site Differences in Physical Impacts Site differences that can affect physical impacts include location of the impervious surfaces, presence of vegetation, and soil type within the watershed. Location of the impervious development can be instrumental in the timing of runoff in a watershed. If the development is at the bottom of the watershed, peak flow from the urbanized area will likely have passed downstream before the flow peaks from the upper watersheds reach the urbanized area (Sauer et al., 1983). Vegetation can reduce channel erosion from storm flows. A study in British Columbia showed that meander bends with vegetation were five times less likely to experience significant erosion from a major flood than similar non vegetated meander bends (Beeson and Doyle, 1995). The types and porosity of soils are also important in determining runoff characteristics from the land surface and erosion potential of the channels. Allen and Narramore Environmental Assessment of Construction and Development Proposed Effluent Guidelines June 2002 2 31 (1985) showed that channel enlargement in chalk channels was from 12 to 67 percent greater than in shale channels near Dallas, Texas. They attributed the differences to greater velocities and shear stress in the chalk channels. Environmental Assessment of Construction and Development Proposed Effluent Guidelines June 2002 3 1 Section 3 Description of Assessment Methodology 3.1 Introduction This section describes EPA's methodology to assess the environmental impacts of the construction and development category. The methodology was used by EPA to quantify the potential environmental and economic benefits that would result from implementation of the proposed regulatory options. These quantified benefits are enumerated in Section 4 of this document.

The methodology described in this section focuses on impacts related to pollutant loadings discharged from construction sites. EPA used total suspended solids (TSS) to indicate pollutantrelated benefits for proposed options.

3.2 Methodology to Estimate Pollutant Loadings from Construction Runoff Water Discharges EPA's methodology for estimating construction site pollutant loadings builds upon the methodology used in the Economic Analysis of the Final Phase II Storm Water Rule (USEPA, 1999). This report (referred to herein as the Phase II EA):

° Estimated the annual number of construction sites or starts covered under Phase I and Phase II programs ° Developed detailed "model construction sites" to represent a range of construction site types, sizes and locations to estimate national construction site TSS loadings (3 site sizes, 5 slopes, and 15 climatic regions)

° Estimated suspended solids loadings with and without a suite of BMPs.

The Phase II EA estimated that in the absence of any controls, construction sites on average generate approximately 40 tons of TSS per acre per year. In addition, the Phase II EA estimated that properly designed, installed and maintained erosion and sediment (E& S) control BMPs, in combination, can potentially achieve a 90 to 95 percent reduction in sediment runoff. The suite of E& S BMPs evaluated in EPA's Phase II EA is shown in Table 3 1. Environmental Assessment of Construction and Development Proposed Effluent Guidelines June 2002 3 2 Table 3 1. Common Construction Erosion and Sediment Control BMPs BMP Description Erosion Control a Sediment Control b Silt Fence Yes Runoff Diversion Yes Mulch Yes Seed and Mulch Yes Construction Entrance Yes Stone Check Dam Yes Sediment Trap Yes Sediment Pond Yes a. Erosion controls are those distributed throughout the site to help retain soil in place. b. Sediment controls are intended to intercept eroded soils preventing runoff from the construction site.

The analysis conducted by EPA indicates that environmental benefits would be achieved by implementing procedures that ensure good E& S practices and that establish design criteria and installation for construction site BMPs. The suite of BMPs considered by EPA in its effluent guidelines development is presented in Table 3 2. Environmental Assessment of Construction and Development Proposed Effluent Guidelines June 2002 3 3 Table 3 2. Site BMPs Evaluated by EPA For Effluent Guidelines Development BMP Description Application Rationale Design/ Installation Criteria Sediment Basins Standardization to 3,600 cubic feet of storage per watershed acre for sites

10 acres.

Sediment Traps Applicable to sites

10 acres.

Mulch Mulching of any denuded surface would be required within 2 weeks of final grade.

PAM a PAM would be used as a temporary stabilization method until final cover can be installed. EPA assumed that PAM is appropriate for 20 percent of construction sites.

Site Administration BMPs E& S Site Inspections and Certification (a) Certify completion of SWPPP, (b) Certify installation of BMPs, (c) Conduct inspections every 14 days, (d) Remove sediment from basins and traps periodically, and (e) Certify that the site has been stabilized prior to filing NOT.

a PAM: Polyacrylamide Implementing these BMPs as part of the proposed Option 1 is expected to achieve benefits due to:

° Higher installation rates because certification would be required; ° Certification of BMP implementation that creates a verifiable record of site E& S controls; ° Higher BMP maintenance frequency due to proposed inspection requirements.

In addition, Option 2 is expected to achieve additional benefits due to:

° Shorter no control periods due to more timely application of erosion BMPs; ° Standardization of design/ sizing criteria (Codification of BMP designs under Option 2 would result in higher removal efficiencies).

Under the proposed options EPA estimates increased efficiency, as measured by the pounds of eroded material retained on construction sites, to range from 5 to 15 percent for Option 1 and 20 percent for Option 2. The lower and upper percentages of net performance for Option 1 yield upper and lower bounds of reductions in construction site loadings discharged to the environment, respectively. These ranges indicate potential additional reductions in suspended Environmental Assessment of Construction and Development Proposed Effluent Guidelines June 2002 3 4 solid discharges as a result of regulatory implementation, and do not account for states with equivalent construction programs and for acres not covered by the proposed guidelines. To account for these two factors, EPA developed additional steps to lower its estimates of TSS loadings reductions.

For Option 2, EPA also reduced the estimated loadings to discount sites between 1 and 5 acres in size. These sites would not be regulated under proposed Option 2 effluent guidelines, and constitute approximately 15 percent of annually developed acreage. EPA discounted TSS loadings reductions estimates by 15 percent to account for the fact that these sites would not be affected by Option 2.

As detailed in Appendix A, EPA performed an evaluation of state construction general permits and regulations to estimate the percentage of national acreage developed annually that is currently covered under regulation that is equivalent to or exceeds the proposed option levels. EPA evaluated states, focusing on those with annual developed acreage greater than 50,000 acres. Overall, EPA estimated that approximately 41 percent of developing acreage is currently subject to regulatory requirements equivalent to or exceeding those under Options 1 and 2. EPA surveyed the following four proposed requirements:

1. 3,600 cubic feet per acre storage requirement for sediment basins on sites  10 acres 2. Certification of BMPs at installation 3. 14 day or more frequent inspection 4. 14 day cover for erosion and dust control.

To account for states currently performing at or above the levels designated under Option 1and 2, EPA reduced estimated TSS loading estimates by 41 percent to remove states with equivalent programs. The results of EPA's loadings assessment are provided in Section 4.

3.3 Characterizing the Nation's Stream Network To evaluate environmental impacts related to stream size and length, EPA characterized stream densities in 19 "ecoregions" for the contiguous United States (Figure 3 1). Detailed methodologies are explained in Appendix B. The 19 ecoregions were developed based on the stream density of large river systems, a relatively coarse assessment. Next, EPA performed a characterization or inventory to estimate a typical stream density within each region, and to define a statistically "standard" watershed for each ecoregion. EPA first determined the stream Environmental Assessment of Construction and Development Proposed Effluent Guidelines 1 Stream Order is a hierarchal ordering of streams based on the degree of branching. A first order stream is an unbranched or unforked stream. Two first order streams flow together to make a second order stream; two second order streams combine to make a third order stream. First order watersheds in EPA's ecoregion specific standard watersheds occupy between 20 and 50 acres.

June 2002 3 5 network based on stream orders 1 , assessing approximately 100,000 acres in each ecoregion. The analysis estimated the average number, acreage, slope, and length of streams, as well as the ratio of stream orders and their drainage area. EPA used those data to estimate the total stream miles in each ecoregion's standard watershed. Because EPA focused on land development, regional stream densities were established through spatial and statistical averaging of actual stream networks at the developing fringe of existing metropolitan areas.

      Figure 3 1. Ecoregions for Stream Inventorying Only one metropolitan area was analyzed for each ecoregion because of the extensive amount of data processed to define stream networks based on 30 meter digital elevation data for 100,000 acres. Environmental Assessment of Construction and Development Proposed Effluent Guidelines June 2002 3 6 EPA's stream inventory focused on relatively small watersheds that terminate in a small perennial stream (e. g., a fourth order stream in the mid Atlantic area). Intermittent and small perennial streams are expected to be the water bodies most adversely affected by the activities of the construction and land development industry. Less emphasis was placed on the inventory and evaluation of larger perennial rivers (i. e., greater than fifth order in the mid Atlantic area) because they potentially have more pollutant sources and isolating the benefits of the proposed effluent guidelines in these water bodies could potentially be difficult.

The results of EPA's assessment of stream information in each of the 19 ecoregion standard watersheds are presented in Table 3 3. In general, whenever EPA determined it should to estimate impacts related to the total mileage of streams located within a defined acreage, EPA used these values to convert the acreage to stream miles on the basis of stream order. Information in the table (i. e., number and stream length) was also used to scale up the impacts on a stream order basis.

Table 3 3. Results of the National Stream Survey EcoRegion Reach Order Number of Segments Analyzed General Ratio of Stream Orders* Average Segment Length, ft Average Slope of River, ft/ ft Average Watershed Acreage per Segment Drainage Area Ratio of Upstream Channels to the Downstream Channel**

1 1 608 87 428 3.06% 53.07 0 2 104 15 1,078 1.75% 273.35 5.15 3 22 3 3,323 1.07% 1,597.67 5.84 4 7 1 6,914 0.81% 6,425.88 4.02 2 1 742 82 499 11.25% 45.78 0 2 166 18 1,185 7.37% 228.24 4.99 3 34 4 2,801 5.25% 1,194.55 5.23 4 9 1 4,297 4.51% 4,434.78 3.71 3 1 829 92 423 3.11% 53.08 0 2 179 20 1,017 2.00% 266.69 5.02 3 35 4 2,307 1.29% 1,316.02 4.93 4 9 1 9,367 0.62% 8,283.03 6.29 Environmental Assessment of Construction and Development Proposed Effluent Guidelines Table 3 3. Results of the National Stream Survey EcoRegion Reach Order Number of Segments Analyzed General Ratio of Stream Orders* Average Segment Length, ft Average Slope of River, ft/ ft Average Watershed Acreage per Segment Drainage Area Ratio of Upstream Channels to the Downstream Channel**

June 2002 3 7 4 1 961 120 309 2.81% 29.55 0 2 209 26 591 1.62% 129.62 4.39 3 45 6 1,259 1.03% 556.92 4.3 4 8 1 6,411 0.50% 4,417.34 7.93 5 1 862 86 434 0.52% 57.35 0 2 201 20 825 0.40% 398.05 6.94 3 47 5 1,751 0.28% 2,119.32 5.32 4 10 1 3,835 0.17% 6,114.79 2.89 6 1 961 120 371 4.37% 29.55 0 2 209 26 779 3.20% 138.31 4.68 3 45 6 1,372 2.45% 554.87 4.01 4 8 1 4,724 1.13% 3,369.25 6.07 7 1 862 86 351 6.22% 42.56 0 2 201 20 954 3.21% 229.2 5.39 3 47 5 2,028 1.81% 1,096.47 4.78 4 10 1 5,850 0.84% 5,447.43 4.97 8 1 638 80 302 1.08% 27.43 0 2 141 18 612 0.72% 123.19 4.49 3 35 4 1,340 0.52% 580.24 4.71 4 8 1 3,058 0.31% 2,112.57 3.64 9 1 645 81 356 0.43% 27.31 0 2 123 15 631 0.50% 127.26 4.66 3 28 4 2,170 0.34% 845.78 6.65 4 8 1 7,322 0.14% 5,134.48 6.07 Environmental Assessment of Construction and Development Proposed Effluent Guidelines Table 3 3. Results of the National Stream Survey EcoRegion Reach Order Number of Segments Analyzed General Ratio of Stream Orders* Average Segment Length, ft Average Slope of River, ft/ ft Average Watershed Acreage per Segment Drainage Area Ratio of Upstream Channels to the Downstream Channel**

June 2002 3 8 10 1 1,238 88 306 3.35% 30.89 0 2 275 20 742 2.05% 158.44 5.13 3 59 4 1,421 1.27% 691.2 4.36 4 14 1 4,392 0.70% 4,339.58 6.28 11 1 1,050 105 353 3.71% 30.89 0 2 198 20 859 2.04% 158.44 5.13 3 41 4 1,595 1.29% 691.2 4.36 4 10 1 3,241 0.81% 4,339.58 6.28 12 1 960 80 376 14.71% 34.1 0 2 215 18 801 9.29% 155.93 4.57 3 50 4 2,162 5.95% 867.6 5.56 4 12 1 3,054 4.15% 3,082.49 3.55 13 1 753 63 272 22.47% 21.96 0 2 161 13 587 14.88% 107.42 4.89 3 43 4 1,311 9.97% 497.52 4.63 4 12 1 6,152 3.77% 3,738.79 7.51 14 1 933 72 427 5.78% 37.21 0 2 194 15 865 3.50% 171.65 4.61 3 44 3 1,635 2.38% 720.88 4.2 4 13 1 2,073 1.35% 2,563.73 3.56 15 1 1,424 129 381 3.86% 31.84 0 2 290 26 697 2.29% 143.06 4.49 3 58 5 1,469 2.05% 545.11 3.81 4 11 1 3,315 1.07% 2,680.10 4.92 Environmental Assessment of Construction and Development Proposed Effluent Guidelines Table 3 3. Results of the National Stream Survey EcoRegion Reach Order Number of Segments Analyzed General Ratio of Stream Orders* Average Segment Length, ft Average Slope of River, ft/ ft Average Watershed Acreage per Segment Drainage Area Ratio of Upstream Channels to the Downstream Channel**

June 2002 3 9 16 1 1,009 72 463 8.12% 39.77 0 2 224 16 1,064 5.09% 191.81 4.82 3 53 4 2,170 3.92% 888.83 4.63 4 14 1 4,309 2.56% 4,293.71 4.83 17 1 464 77 464 20.60% 57.02 0 2 79 13 1,605 14.51% 395.06 6.93 3 21 4 3,018 9.47% 1,823.06 4.61 4 6 1 5,392 4.27% 6,881.95 3.77 18 1 251 84 381 3.86% 31.84 0 2 50 17 697 2.29% 143.06 4.49 3 13 4 1,469 2.05% 545.11 3.81 4 3 1 3,315 1.07% 2,680.10 4.92 19 1 457 65 463 8.12% 39.77 0 2 102 15 1,064 5.09% 191.81 4.82 3 27 4 2,170 3.92% 888.83 4.63 4 7 1 4,309 2.56% 4,293.71 4.83 Notes: A stream "segment" is a single stream reach between upstream and downstream confluence points. * The "General Ratio of Stream Orders" value indicates the number of streams of "X" order found in a single fourth order watershed. ** The "Drainage Area Ratio of Upstream Channels to the Downstream Channel" indicates the ratio of drainage areas based on full watershed area of each stream order.

3.3.1 Characterizing the Stream Network within Developing Acreage Although the information contained in the table can be used to convert acreage into estimated stream miles for the 19 ecoregions it is not sufficient to estimate the number of stream miles Environmental Assessment of Construction and Development Proposed Effluent Guidelines June 2002 3 10 contained within the land area developed each year. To calculate that estimate, EPA first estimates the number of acres developed and the geographic region in which the developing acres are located. EPA used geographically linked annual development rates in the U. S. from the National Resources Inventory (NRI) (USDA, 2000). The NRI captures data on land cover and use, soil erosion, prime farmland soils, wetlands, habitat diversity, selected conservation practices, and related resource attributes at more than 800,000 scientifically selected sample sites. NRI estimated the development rate for hundreds of individual watersheds that cover the contiguous states. To estimate the annual development rate for each of the 19 ecoregions, EPA summed the development rates of all watersheds within the boundary of each ecoregion.

The NRI was used for assessing the impacts of the construction and land development industry because it provides a consistent and periodic national assessment of land development trends and employs a standard methodology for the entire nation. In addition, the NRI also provides information on land use prior to development (e. g., the acres of farm land converted into residential use). EPA's analysis of the most current NRI information available (rates of land development from 1992 to 1997) is shown in Table 3 4, which shows that the current rate of land development is approximately 2 million acres per year. Environmental Assessment of Construction and Development Proposed Effluent Guidelines June 2002 3 11 Table 3 4. Land Development Annually in Ecoregions (Adapted from USDA, 2000)

Ecoregion Acres Developed Annually Percent of National Total Miles of Streams Within Developed Acres 1 64,236 2.9% 134 2 91,015 4.1% 303 3 34,424 1.6% 61 4 338,378 15.2% 957 5 67,107 3.0% 137 6 127,511 5.7% 387 7 42,321 1.9% 82 8 252,790 11.4% 1,075 9 330,635 14.9% 805 10 326,850 14.7% 686 11 97,386 4.4% 181 12 249,748 11.3% 757 13 35,090 1.6% 113 14 38,822 1.7% 152 15 11,093 0.5% 42 16 57,947 2.6% 149 17 28,799 1.3% 58 18 12,592 0.6% 47 19 12,607 0.6% 32 Totals 2,219,352 6,160 Values provided indicate total acres developed. Approximately, sites

1 acres constitute 2 percent of acres developed, and sites between 1 and 5 acres constitute 15% of the acres developed.

Table 3 4 also provides EPA's estimate of the miles of stream contained within the acres developed annually. When estimating the total miles of stream per ecoregion by stream order, EPA first estimated the number of fourth order watersheds developed. For example, in Environmental Assessment of Construction and Development Proposed Effluent Guidelines June 2002 3 12 ecoregion 19, the number of acres developed annually (12,607) was divided by the number of acres in a fourth order watershed (4,293) to yield the number of developed watersheds (2.9). This number was then multiplied by the average number of feet per fourth order stream (4,309) and by the stream order ratio (1) to yield the number of feet of fourth order streams in developed areas (12,496). In order to find the total number of stream feet for the ecoregion, these steps are repeated for third, second and first order streams and the sum taken of each order of stream feet.

3.3.2 Characterizing the Flow Conditions in Stream Network Table 3 5 shows the estimated division of perennial and intermittent streams by stream order for each ecoregion. The designations provided in Table 3 5 are based on best professional judgment. EPA notes that third and fourth order streams in relatively arid areas of the nation could be perennial due to small dams and lakes; however, the analysis assumes they are intermittent in nature. Environmental Assessment of Construction and Development Proposed Effluent Guidelines June 2002 3 13 Table 3 5. Characterization of Stream Orders for Ecoregions Ecoregion 1st Order 2nd Order 3rd Order 4th Order 1 I I I I 2 I I I I 3 I I I P 4 I I P P 5 I I P P 6 I I P P 7 I I P P 8 I I P P 9 I I P P 10 I I P P 11 I I P P 12 I I P P 13 I I I I 14 I I I I 15 I I P P 16 I I P P 17 I I P P 18 I I I I 19 I I P P 20 I I P P P = Perennial; I = Intermittent EPA estimated the total miles of intermittent and perennial streams based on a cross product of information on Tables 3 3, 3 4 and 3 5 (total stream lengths by order, ecoregion development rates, and perennial/ intermittent assumptions, respectively). The results of this calculation are shown in Table 3 6. Environmental Assessment of Construction and Development Proposed Effluent Guidelines June 2002 3 14 Table 3 6. Characterization of Stream Length by Flow Type for Ecoregions Ecoregion Geographic Name Baseline Conditions Perennial Stream Miles Intermittent Stream Miles 1 Midwest 0 134 2 Southwest Arid 0 303 3 Southwest 7 54 4 Coastal Atlantic 196 762 5 Atlantic Shoreline 25 112 6 North Florida 77 310 7 South Florida 19 63 8 New England 197 878 9 Appalachia 198 608 10 Great Lakes Region 147 539 11 Mississippi Outlet 38 143 12 Mississippi West 159 598 13 Upper Midwest & Dakotas 0 113 14 Midwest Central 0 152 15 Pacific Coastal Region 8 34 16 Southern California 32 117 17 Willamette Valley 13 45 18 Eastern Washington 0 47 19 Sierras 7 25 Total 1,123 5,036 3.3.3 Converting Stream Miles into Impact Estimates Inventorying stream information for each of the ecoregions and estimating the miles of stream contained within urbanizing acreage provides a basis for estimating impacts that are proportional Environmental Assessment of Construction and Development Proposed Effluent Guidelines June 2002 3 15 to stream length. EPA developed data sets which indicate stream type (perennial or intermittent), stream order, and location (ecoregion). The data, however, are not sufficiently customized at the local/ regional level to permit detailed environmental modeling of stream impacts on an ecoregion basis. Hence, EPA estimated environmental changes at the national level.

Table 3 6 shows national and ecoregion specific estimates of the river miles contained within the acres developed annually, if all acres developed were within a single watershed. Additional adjustment is necessary to account for the fact that development is not consolidated in a single land mass but rather is dispersed among areas not currently under construction. See Figure 3 2. To estimate the miles of streams potentially impacted under baseline conditions, EPA considered a range of assumptions about the ratio of construction to non construction area within watersheds. As shown in Figure 3 2, EPA assumed that an area of 10 times larger than the total area under construction is also impacted from runoff from construction in addition to runoff from urban areas, forests and agriculture.

Land Use Type Distribution Across Watershed Existing Urban Area (25% Under Scenario 1) Farm/ Pasture Area (32.5% Under Scenario 1) Forested Area (32.5% Under Scenario 1) Construction This Year (10% Under Scenario 1) Stream Channels Figure 3 2. Land Use Distribution of a Watershed. Environmental Assessment of Construction and Development Proposed Effluent Guidelines June 2002 3 16 Given this assumption, a construction rate of 2.2 million constructed acres per year means that streams dispersed in 22 million acres of land area are potentially impacted by construction site runoff in combination with runoff from urban, forested and farm land. Based on EPA's assessment of stream lengths contained in the 19 ecoregions and the rates of development in each ecoregion, EPA estimates that roughly 10,000 perennial stream miles and 36,000 intermittent stream miles are potentially affected by construction site runoff annually (Table 3 7).

Table 3 7. Estimated Miles of Streams Potentially Affected by One Year's Construction Ecoregion Geographic Name 2. 2 Million Acres (Acreage Constructed Annually ) 22 Million Acres (Assumed Land Area Containing Acreage Constructed Annually )

Perennial Stream Miles Intermittent Stream Miles Perennial Stream Miles Intermittent Stream Miles 1 Midwest  107 0 1,070 2 Southwest Arid  242 0 2,420 3 Southwest 7 43 70 430 4 Coastal Atlantic 196 609 1,960 6,090 5 Atlantic Shoreline 25 90 250 900 6 North Florida 7 South Florida 8 New England 197 702 1,970 7,020 9 Appalachia 198 486 1,980 4,860 10 Great Lakes Region 147 431 1,470 4,310 11 Mississippi Outlet 12 Mississippi West 159 478 1,590 4,780 13 Upper Midwest & Dakotas  91 0 910 14 Midwest Central  121 0 1,210 15 Pacific Coastal Region 8 27 80 270 16 Southern California 32 93 320 930 17 Willamette Valley 13 36 130 360 Environmental Assessment of Construction and Development Proposed Effluent Guidelines Table 3 7. Estimated Miles of Streams Potentially Affected by One Year's Construction Ecoregion Geographic Name 2. 2 Million Acres (Acreage Constructed Annually ) 22 Million Acres (Assumed Land Area Containing Acreage Constructed Annually )

Perennial Stream Miles Intermittent Stream Miles Perennial Stream Miles Intermittent Stream Miles June 2002 3 17 18 Eastern Washington  38 0 380 19 Sierras 7 20 70 200 Total 989 3,614 9,890 36,140 Notes: ° EPA assumed that all streams within fourth order watersheds are intermittent in regions 1, 2, 13, 14, and 18. ° Total values reflect a 20 percent reduction in intermittent stream miles to account for streams that are expected to be converted into below grade pipe systems. Values also discount stream miles in Ecoregions 6, 7, and 11 because these systems are greatly influenced by man made channel networks and natural wetland systems (i. e., are less hierarchal in nature).

EPA then developed a simple stream model to assess potential changes in TSS concentrations during wet weather periods for the estimated 61 thousand miles of streams receiving discharges from construction sites annually. EPA evaluated three development scenarios to estimate the range of potential TSS reductions in streams within watersheds experiencing construction runoff, as shown in Table 3 8. The three development scenarios are intended to represent low, moderate, and high levels of urbanization, over which construction activities are superimposed. EPA used a simple mass balance approach to estimate in stream TSS concentrations, as follows:

1. Estimate the average annual runoff from each land use condition, from construction acreage affected, and not affected by proposed guideline options.

2. Estimate the average annual TSS loading from each land use condition, based on EPA estimated or literature reported event mean concentration (EMC) for TSS.

3. Estimate national average change in the in stream concentration of TSS using land use fractions given in each of the three scenarios in Table 3 8. This assessment is performed for all 2.2 million acres developed annually, based on the total estimated runoff volume in a single (typical) rainfall year.

Table 3 8, also shows the allocation of regulated construction sites for Options 1 and 2. Under Option 1, approximately 0.2 percent of the watershed is assumed to be covered by construction sites less than 1 acres in size. The runoff from these acres is not affected by Option 1 proposed Environmental Assessment of Construction and Development Proposed Effluent Guidelines June 2002 3 18 requirements. Under Option 2, approximately 1.7 percent of the watershed is assumed to be covered by construction sites less than 5 acres in size. The runoff from these acres are not affected by Option 2 proposed requirements. Runoff coefficients (Table 3 9) indicate the portion of rainfall that leaves the area as runoff. The remainder is assumed to infiltrate into the ground or evaporate. Values were selected based on EPA estimates of percent imperviousness, values reported in literature, and best professional judgement.

Table 3 8. Active Construction Site Runoff Scenarios for Option 1 and Option 2 Land Use Conditions Land Use Coverage Scenarios Low Urbanization Moderate Urbanization High Urbanization Existing Urban Area 25.0% 50.0% 75.0%

Forested 32.6% 20.1% 7.6%

Farm 32.6% 20.1% 7.6%

Sites Regulated Under Option 1 9.80% 9.80% 9.80%

Sites Not Affected by Option 1 0.20% 0.20% 0.20%

Sites Regulated Under Option 2 8.27% 8.27% 8.27%

Sites Not Affected by Option 2 1.73% 1.73% 1.73%

Table 3 9. Runoff Coefficients for Land Uses Land Use Conditions Runoff Coefficients Existing Urban Area 0.46 Forested 0.05 Farm 0.15 Construction a 0.80 a. Includes sites regulated under Option 1, not affected by Option 1, regulated under Option 2, and not affected by Option 2. Environmental Assessment of Construction and Development Proposed Effluent Guidelines 2 EPA defined a "typical rainfall year" as having a total rainfall depth within 10 percent of the average for the ecoregion, and not containing a single rainfall event with greater than a 2 year storm.

June 2002 3 19 EPA's simple in stream model estimates the potential reduction in TSS concentration during wet weather periods. EPA's approach does not taken into account the contributions of base flow and base flow loads (i. e., that entering streams due to groundwater) during wet weather periods. Excluding this base flow results in an overestimation of actual TSS concentrations.

Because rainfall conditions affect the results of EPA's assessment, an evaluation of approximately 30 years of rainfall records for 1,200 rainfall gauges was performed to identify a typical rainfall year for each of the 19 ecoregions. 2 Based on this evaluation, EPA estimated that the national average rainfall depth falling on construction sites is approximately 34.8 inches per year. This estimate is a weighted average, based on the acres developed in each ecoregion.

Table 3 10 presents the event mean concentrations (EMCs) used by EPA to estimate the range of TSS loadings. In selecting EMC values, EPA used values from the literature that would help create reasonable upper and lower bound estimates. High and low effectiveness estimates for construction site effluent concentrations were matched with lower bound and upper bound EMCs, respectively, for other land uses. For example, lower bound and upper bound EMC values for urban runoff (141 and 224 mg/ L) were assumed to bracket urban concentrations, and to indicate TSS annual loadings. Only forested area EMCs were held constant for both lower and upper bound estimates. In terms of annual TSS yield, EPA's assumed EMCs for urban areas correspond to 0.26 and 0.41 tons per acre per year. Annual TSS yield for farm/ pasture, equates to 0.15 and 3.0 tons per acre per year (Corsi et al., 1997; Novotny and Chesters, 1981; Horner et al., 1986; Horner, 1992; and Sonzogni et al., 1980).

EPA assumed that construction sites not affected by the proposed effluent guidelines would discharge TSS in concentrations similar to those estimated under baseline conditions. This assumption may overestimate TSS loadings estimates associated with Option 2 for sites between 1 and 5 acres. The results of EPA's simple national in stream model, based on the data and assumptions described above, are provided in Section 4. Environmental Assessment of Construction and Development Proposed Effluent Guidelines June 2002 3 20 Table 3 10. Runoff EMCs for Acres Within a Watershed (TSS in mg/ L)

Land Use Condition Lower Bound Upper Bound Option 1 Option 2 Option 1 Option 2 Urban Area 141 141 224 224 Forested/ Pasture 152 152 152 152 Farm 254 254 5,071 5,071 Regulated Construction Sites 2,613 1,843 6,529 5,081 Construction Sites Not Affected by Regulations 3,765 3,765 6,914 6,914 Notes: ° Urban TSS Concentrations are from USEPA, 1993 ° Option 1 high and low effectiveness assumes construction BMPs are installed/ operated so resulting capture of TSS generation is 80 and 50% of TSS generation, respectively. ° Option 2 high and low effectiveness assumes construction BMPs are installed/ operated so resulting capture of TSS generation is 90 and 70% of TSS generation, respectively. Environmental Assessment of Construction and Development Proposed Effluent Guidelines June 2002 4 1 Section 4 Environmental Benefits Assessment of Evaluated Regulatory Options This section presents the Agency's estimates of the environmental benefits that would result from implementation of erosion and sediment controls during construction activities. EPA evaluated 3 regulatory options for controlling discharges from active construction sites. Table 4 1 describes each of the options.

Table 4 1. Regulatory Options Evaluated for Controlling Discharges from Construction Activities Option Description Option 1 ° Applicable to construction sites with one acre or more of disturbed land ° Operators required to:  Inspect site throughout land disturbance period  Certify that the controls meet the regulatory design criteria as applicable ° Amend NPDES regulations at 40 CFR Part 122 (no new effluent guideline regulations)

Option 2 ° Applicable to construction sites with five acres or more of disturbed land ° Operators required to:  Prepare storm water pollution prevention plan  Design, install, and maintain erosion and sediment controls  Inspect site throughout land disturbance period  Certify that the controls meet the regulatory design criteria as applicable ° Creates a new effluent guidelines category at 40 CFR Part 450 and amends Part 122 regulations Option 3 ° No new regulatory requirements The following subsections present Agency estimates of regulatory conditions for suspended solids loadings and resulting improvements to the environment, including stream habitat.

4.1 Total Suspended Solids Loadings Construction projects involve a series of temporary activities (e. g., land clearing, grubbing, building), and, with the exception of large scale facilities, these projects generally have a duration of less than a year. During the construction period, erosion and sediment control (ESC) BMPs are employed to minimize pollutant discharges.

EPA used three criteria as a basis for selecting which pollutants to use as indicators of construction site pollutant loadings: (1) pollutants that correlate strongly with the construction Environmental Assessment of Construction and Development Proposed Effluent Guidelines June 2002 4 2 activities, (2) toxic pollutants should be considered only if dissolved concentrations are high, and (3) proposed effluent guidelines would significantly reduce loadings from current levels. Based on these criteria, EPA selected eroded soils/ sediment loadings (e. g., measured by TSS and14 turbidity) as the indicator of construction site pollutant loadings. Other runoff constituents are either present in low concentrations or account for such a small proportion of the total discharge that conventional treatment would not prove effective in removing additional levels beyond that attained in treating the suspended solid component.

Table 4 2 presents EPA's estimates of construction site loadings reductions under Options 1, 2 and 3 in terms of tons of TSS per year.

Table 4 2. Estimated TSS Loadings Reductions for Proposed Regulatory Options Option 1 Option 2 Option 3 Lower bound estimates Incremental Percent TSS captured by BMPs 5% 25% 0 Annual reductions (tons) 2,637,569 11,126,639 a 0 Upper bound estimates Incremental Percent TSS captured by BMPs 15% 25% 0 Annual reductions (tons) 7,912,707 11,126,639 a 0 a. Option 2 reductions were reduced by approximately 15 percent to account for sites between 1 and 5 acres in size not covered by this option.

As shown in the table, EPA estimates that under Option 1, construction sites would increase the removal rate of TSS by approximately 5 to 15 percent. The projected increase in net performance of construction site BMPs under Option 2 is about 25 percent. These estimates were developed using the Agency's engineering judgement, but are based on the following assumptions:

° Regulatory options would require that sediment ponds are certified at the time of installation to ensure they are built as designed ° Implementation of the proposal would result in more effective selection, installation and O& M of ESC BMPs due to inspection and certification of site activities.

° Option 2 would result in shorter duration of exposure for un managed denuded areas The regulatory options loadings were generated using three factors: total annual number of acres developed, tons per year of suspended solids per acre of land undergoing development, and Environmental Assessment of Construction and Development Proposed Effluent Guidelines June 2002 4 3 incremental improvement in BMP performance under the regulatory options. As described in Section 3, NRI data were used to estimate that approximately 2.2 million acres are developed annually and the estimate of 40 tons per acre generation of TSS at construction sites was based on the Phase II Storm Water Economic Assessment (EPA, 1999).

Estimated annual sediment loadings reductions from implementation of EPA's proposed alternatives range from 0 tons (Option 3: no new regulations) to approximately 11 million tons per year for Option 2.

4.2 Total Suspended Solid In Stream Concentrations Although the Agency did not attempt to quantify aquatic losses (e. g., fish kills, habitat loss), it did estimate how construction loadings impact in stream concentration levels of TSS in receiving water bodies.

Because in stream concentrations of TSS result from mixtures of point and nonpoint sources that cannot cannot be readily separated, EPA estimated in stream TSS concentrations for three different land use scenarios that assumed 10 percent of the land area was under construction and 90 percent was distributed among three types of land uses: forest, farm and urban. As shown in Table 4 3, the land use scenarios were developed to characterize different levels of urbanization, ranging from 25 percent urban in scenario 1 to 75 percent urban in scenario 3. EPA's analysis does not assess in stream settling and resuspension. In addition, there are other sources of TSS that have not been included in the analysis, such as loads resulting from commercial point source discharges and loads resulting from increased stream bank erosion related to higher stream flow rates and velocities in urbanizing water bodies. TSS loadings (section 4.1) were used in conjunction with different event mean concentration (EMC) values, runoff coefficients, and ESC BMP efficiency rates to generate TSS in stream concentrations, as described in section 3.3.3.

Table 4 3. Development Scenarios Used to Estimate Impacts of Regulatory Options Development Scenario Land Use Proportions 1. Low Urbanization 25% Urban, 10% Construction, 32.5% Farm, 32.5% Forest 2. Moderate Urbanization 50% Urban, 10% Construction, 20% Farm, 20% Forest 3. High Urbanization 75% Urban, 10% Construction, 7.5% Farm, 7.5% Forest Different land use scenarios were evaluated because of the differences in TSS characteristics that result as land becomes developed from rural to urban conditions. The high urban conditions contribute the lowest levels of TSS while the low urbanization contribute the highest levels of Environmental Assessment of Construction and Development Proposed Effluent Guidelines June 2002 4 4 TSS. This can be explained by the fact that forest and farm practices generate higher levels of sediment runoff and urbanized areas create more storm water runoff, diluting TSS concentrations.

Table 4 4 shows the estimated concentration reductions in TSS from the regulatory options. Reductions in TSS concentrations under Option 1 are estimated to range from 68 to 348 mg/ L. TSS concentrations under Option 2 would decrease from 276 to 489 mg/ L. The larger reductions from regulatory Option 2 reflect the more stringent proposed requirements resulting in higher ESC BMP effectiveness. Reductions from the lower bound comparisons are higher than reductions in the upper bound comparisons.

Table 4 4. Estimated Average In Stream TSS Concentrations Reduction, mg/ L Development Scenario High Effectiveness Estimates Low Effectiveness Estimates Option 1 Option 2 Option 1 Option 2 1. Low Urbanization 348 489 116 466 2. Moderate Urbanization 258 363 86 346 3. High Urbanization 205 289 68 276 Note: The results provided in this table could overestimate the differences between the effects of high and low urbanization because the study did not include discharges from commercial point sources or from increased stream bank erosion resulting from increased stream flow rates and velocities in urbanized areas. If these factors had been included, the concentrations under high urbanization would likely have been significantly higher.

4.3 Miscellaneous Impacts Sites under construction have hydrologic responses that differ from those under pre development conditions; both the peak discharge and duration of high discharges increase dramatically. (Appendix C describes hydrologic changes caused by construction and the effects of commonly employed sedimentation ponds on site discharge.) As a result, EPA believes that construction sites increase the potential for flooding of downstream areas above the levels found in the predevelopment condition. Both Options 1 and 2 are expected to reduce flooding potential by ensuring the installation and maintenance of sedimentation ponds (if already present) that retain site runoff and help minimize flooding potential.

Poor ESC BMP implementation has an adverse impact on aesthetics of affected water bodies lowering the visual quality of streams and lakes by creating high turbidity levels. Sediment Environmental Assessment of Construction and Development Proposed Effluent Guidelines June 2002 4 5 enriched runoff from failing construction site ESC BMPs convey sediment to adjacent land creating a visual nuisance and sometimes requiring clean up. Although EPA did not estimate the environmental or economic benefits associated with improvements in these conditions, EPA believes that both Option 1 and 2 would reduce these impacts significantly by requiring closer tracking of ESC BMP operation, problem identification, and problem resolution. Environmental Assessment of Construction and Development Proposed Effluent Guidelines June 2002 5 1 Section 5 References Allen, P. and R. Narramore. 1985. Bedrock Controls on Stream Channel Enlargement with Urbanization, North Central Texas. Water Resources Bulletin. 21( 6): 1037 1048.

Bagley et al. 1998. Sources and Fate of Giardia Cysts and Cryptosporidium Oocysts in Surface Waters. Journal of Lake and Reservoir Management. 14( 2 3): 379 392.

Bannerman, R.; D. Owens; R. Dodds; and N. Hornewer. 1993. Sources of Pollutants in Wisconsin Stormwater. Water Science and Technology. 28( 3 5): 241 259.

Barfield, B. J. and M. J. Clar. 1985. Development of New Design Criteria for Sediment Traps and Basins. Prepared for Maryland Department of the Environment, Water Resources Administration, Sediment and Stormwater Division. Annapolis, MD. 33pp.

Barr, R. 1997. Maryland NPDES Phase I Monitoring Data. Maryland Department of the Environment. Baltimore, MD.

Barrett, M. and J. Molina. 1998. Comparison of Filtration Systems and Vegetated Controls for Stormwater Treatment. 3 rd International Conference on Diffuse Pollution. August 31 September 4, 1998. Scottish Environment Protection Agency. Edinburgh, Scotland.

Bay S. and J. Brown. 2000. Assessment of MTBE Discharge Impacts on California Marine Water Quality. Prepared for State Water Resources Control Board. Southern California Coastal Water Research Project. Westminster, California.

Beeson, C. and P. Doyle. 1995. Comparison of Bank Erosion at Vegetated and Non vegetated Bends. Water Resources Bulletin. 31( 6).

Blankenship, K. 1996. Masked Bandit Uncovered in Water Quality Theft. Bay Journal. Vol 6. No. 6. Alliance for the Chesapeake Bay, Baltimore, MD.

Booth, D. 1990. Stream Channel Incision Following Drainage Basin Urbanization. Water Resources Bulletin. 26( 3): 407 417.

Booth, D. , D. Montgomery, and J. Bethel. 1996. Large Woody Debris in the Urban Streams of the Pacific Northwest. In Effects of Watershed development and Management on Aquatic Systems . L. Roesner (ed.) Engineering Foundation Conference. Proceedings. Snowbird, UT. August 4 9, 1996. Pp. 178 197. Environmental Assessment of Construction and Development Proposed Effluent Guidelines June 2002 5 2 Brown, E. and R. Claytor. 2000. Draft Watershed Assessment Study for Watts Branch. Watts Branch Watershed Plan. City of Rockville, MD. Center for Watershed Protection. Ellicott City, MD.

Campbell, K. R. 1995. "Concentrations of "Heavy Metals Associated with Urban Runoff in Fish Living in Stormwater Ponds." Archives of Environmental Contamination and Toxicology 27: 352 356.

Caraco D. S. 2000. "The Dynamics of Urban Stream Channel Enlargement." Article No. 19 in The Practice of Watershed Protection. 2000. Center for Watershed Protection, Ellicott City, MD. http:// www. stormwatercenter. net Center for Watershed Protection. 2000. The Practice of Watershed Protection: Techniques for Protecting Our Nation's Streams, Lakes, Rivers and Estuaries. Ellicott City, MD.

Collins, A., D. Wallings, and G. Leeks. 1997. Source Type Ascription for Fluvial Suspended Sediment Based on a Quantitative Composite Fingerprinting Technique. Catena 29: 1 27.

Corsi, S. R., D. J. Graczyk, D. W. Owens, and R. T. Bannerman. 1997. Unit Area Loads of Suspended Solids and Total Phophorus from Small Watersheds in Wisconsin. USGS Fact Sheet FS 195 97.

Crunkilton, R. et al. 1996. Assessment of the Response of Aquatic Organisms to Long term Insitu Exposures of Urban Runoff. In: Effects of Watershed Development and Management on Aquatic Ecosystems: Proceedings of an Engineering Foundation Conference. Snowbird, UT.

Dartiguenave, C. M., I. ECLille and D. R. Maidment. 1997. Water Quality Master Planning for Austin. CRWR Online Report 97 6.

Dunne, T., and L. B. Leopold. 1978. Water in Environmental Planning. W. H.. Freeman and Co., New York. 818 pp.

Ellis, J. 1986. "Pollutional Aspects of Urban Runoff." In: Urban Runoff Pollution. eds., H. C. Torno, J. Marsalek and M. Desbordes. Springer Verlag, Berlin.

Evett, et al. 1994. Effects of Urbanization and Land Use Changes on Low Stream Flow. North Carolina Water Resources Research Institute, Report No. 284. 66 pp.

Field R. and R. Pitt 1990. Urban Storm induced Discharge Impacts: US Environmental Protection Agency Research Program Review. Water Science and Technology. Vol. (22) 10 11. Environmental Assessment of Construction and Development Proposed Effluent Guidelines June 2002 5 3 Gavens, A., D. Revitt and J. Ellis. 1982. "Hydrocarbon Accumulation in Freshwater Sediments of an Urban Catchment." Hydrobiologia. (91): 285 292.

Galli, J. 1991. "Thermal Impacts Associated with Urbanization and Stormwater Management Best Management Practices." Publication No. 91701. Metropolitan Washington Council of Governments. Washington, D. C. 188 pp. http:// www. mwcog. org Guay, J. 1996. Effects of Increased Urbanization from 1970's to 1990's on Storm Runoff Characteristics in Perris Valley, CA. USGS Water Resources Investigations Report. 95 4273.

Hammer, T. 1972. "Stream Channel Enlargement Due to Urbanization." Water Resources Research 8( 6): 1530 1540.

Heany, J. and W. Huber. 1978. Nationwide Assessment of Receiving Water Impacts from Urban Storm Water Pollution. U. S. Environmental Protection Agency, Cincinnati, OH.

Hilgartner, W. 1986. Human Actions in the Watershed Reflected in Historical Estuarine Changes. Coastlines. Issue 6.2.

Hollis, F. 1975. The Effects of Urbanization on Floods of Different Recurrence Intervals. Water Resources Research, 11: 431 435.

Horner, et al. 1996. Watershed Determinates of Ecosystem Functioning. In: Effects of Watershed Development and Management on Aquatic Ecosystems. Roesner, L. A. (editor). Snowbird Utah. August 4 9, 1996. Engineering Foundation.

Horner, R. R., J. J. Skupien, E. H. Livingston and H. E. Shover. 1992. Water Quality Impacts of Urban Land Use. In: Fundamentals of Urban Runoff Management: Technical and Institutional Issues. Terrene Institute, Washington, DC.

Horner, R. R., J Geurdy, and M. J. Kortenhoff. 1990. Improving the Cost Effectiveness of Highway Construction Site Erosion and Pollution Control. Washington State Transportation Center and the Federal Highway Administration. Seattle, WA, 79pp.

Islam, Taphorn and Utrata Halcomb, 1998. Current Performance of Sediment Basins & Sediment Yield Measurement of Construction Sites in Unincorporated Hamilton County, Ohio. Prepared for Hamilton County Soil and Water Conservation District.

Jarrett, A. 1996. Sediment Basin Evaluation and Design Improvements. Pennsylvania State University. Prepared for Orange County Board of Commissioners, 11pp. Environmental Assessment of Construction and Development Proposed Effluent Guidelines June 2002 5 4 Kundell, J. and T. Rasmussen. 1995. Recommendations of the Georgia Board of Regent's Scientific Panel on Evaluating the Erosion Measurement Standard Defined by the Georgia Erosion and Sedimentation Act. In Proceedings of the 1995 Georgia Water Resources Conference. Athens, Georgia.

Leopold, L. 1968. Hydrology for Urban Land Use Planning – A Guidebook on the Hydrologic Effects of Urban Land Use. U. S. Geological Survey. Circular No. 554.

Leopold, L. 1973. "River Change with Time: An Example." Geological Society of America Bulletin. 84: 1845 1860.

Leopold, L. 1994. A View of the River. Harvard University Press, Cambridge, MA.

Lim, S. and V. Olivieri. 1982. Sources of Microorganisms in Urban Runoff. Johns Hopkins School of Public Health and Hygiene. Jones Falls Urban Runoff Project. Baltimore, MD 140 pp.

Livingston, E. "Florida's Evolving Stormwater/ Watershed Management Program" In Effects of Watershed development and Management on Aquatic Systems. L. Roesner (ed.) Engineering Foundation Conference. Proceedings. 1996. Snowbird, UT. (August 4 9): 567 590.

MacCoy, D. and R. Black. 1998. Organic Compounds and Trace Elements in Freshwater Streambed Sediment and Fish from the Puget Sound Basin. U. S. Geological Survey. USGS Fact Sheet 105 98.

McCutcheon, S. C., Martin, J. L. and Barnwell, T. O., Jr., Water Quality, Chapter 11, Handbook of Hydrology, David Maidment, Ed., McGraw Hill, New York, 1993.

Mackiernan, G., M. Leffler and T. Malone. 1996. Scientific Consensus and Public Policy: Dissolved Oxygen in the Chesapeake Bay. Watershed `96 Conference Proceedings. Baltimore, Maryland.

MacRae, C. and J. Marsalek. 1992. The Role of Stormwater in Sustainable Urban Development. Proceedings Canadian Hydrology Sympposium: 1992 Hydrology and its Contribution to Sustainable Development, June 1992. Winnipeg, Canada.

MacRae and DeAndrea, 1999. Assessing the Impact of Urbanization on Channel Morphology. 2 nd Internaitonal Conference on Natural Channel Systems. Niagra Falls, OT. Environmental Assessment of Construction and Development Proposed Effluent Guidelines June 2002 5 5 Masterson, J. and R. Bannerman 1994. Impacts of Stormwater Runoff on Urban Streams in Milwaukee County, Wisconsin. National Symposium on Water Quality. American Water Resources Association.

May, C. R. Horner, J. Karr, B. Mar, and E. Welch. 1997. Effects of Urbanization on Small Streams In the Puget Sound Lowland Ecoregion. Article No. 18 in The Practice of Watershed Protection. 2000. Center for Watershed Protection, Ellicott City, MD. http:// www. stormwatercenter. net Maxted, J. R., E. L. Dickey, and G. M. Mitchell. 1994. Habitat Quality of Delaware Nontidal Streams. Delaware Department of Natural Resources, Division of Water Resources Report.

Mederios, C., R. LeBlanc, and R. A. Coler. 1983. An In situ Assessment of the Acute toxicity of Urban Runoff to Benthic Macroinvertebrates. Environmental Toxicity and Chemistry (2): 119 126.

Menzie Cura and Associates. 1995. Measurements and Loadings of Polycyclic Aromatic Hydrocarbons (PAH) in Stormwater, Combined Sewer Overflows, Rivers, and Publically Owned Treatment Works (POTWs) Discharging into Massachusets Bay.

Morisawa, Marie and Ernest LaFlure. 1979. Hydraulic Geometry, Stream Equalization and Urbanization. In the Proceedings of the Tenth Annual Geomorphology Symposia Series entitled "Adjustments of the Fluvial System" held at Binghamton, New York September 21 22, 1979. Kendall/ Hunt Publishing Company, Dubuque, IA.

NOAA. 1992. 1990 Shellfish Register If Classified Estuarine Waters: Data Supplement. National Oceanic and Atmospheric Agency, National Ocean Service, Rockville, MD.

New Mexico Surface Water Quality Bureau, 1999. Six Mile, Cieneguilla and Moreno Creeks Draft Fecal Coliform TMDL Document.

Novotny, V. and G. Chesters. 1981. Handbook of Nonpoint Pollution: Sources and Management. Van Nostrand Reinhold Company NY. 555 pp.

Orth, R. and K. Moore. 1983. Chesapeake Bay: An Unprecedented Decline in Submerged Aquatic Vegetation. Science 22: 51 52.

Pasternack, G. 1998. Physical Dynamics of Tidal Freshwater Delta Evolution. PhD Dissertation. Johns Hopkins University, Baltimore, Maryland. Environmental Assessment of Construction and Development Proposed Effluent Guidelines June 2002 5 6 Pitt, R. 1998. Epidemiology and Stormwater Managment. In Stormwater Quality Management. CRC /Lewis publishers. New York, NY.

Pitt, R. and J. Voorhees. 1989. Source Load and Management Model – An Urban Nonpoint Source Water Quality Model: Wisconsin Department of Natural Resources, v. I III, PUBL WR Richey, J. S. 1982. Effects of Urbanization on a Lowland Stream in Urban Washington. PhD Dissertation. University of Washington.

Samadpour, M. and N. Checkowitz. 1998. Little Soos Creek microbial source tracking. Washington Water RESOURCE, Spring, 1998. University of Washington Urban Water Resources Center.

Sauer V. et al. 1983. Flood Characteristics of Urban Watersheds in the United States. US Geological Survey Water Supply Paper 2207.

Schiff, K. 1996. Review of Existing Stormwater Monitoring Programs for Estimating Bight Wide Mass Emissions from Urban Runoff. SCCWRP Annual Report 1996.