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OCR for page 118
CHAPTER 5. WATER QUALITY AND DRAINAGE OVERVIEW Connections between water quality issues and environmental justice may not be apparent at first glance, but there are several possible links. Natural physical laws and topography dictate the design of water quality and drainage improvements, and the location and function of these improvements could have distributive effects. Additionally, the associated improvements typically include a number of subjective design issues that can affect the quality of the visual environment. The very essence of water quality improvements suggests a net positive result for society. You should, however, consider a wider range of interests than has typically been done in the past to ensure that protected groups are not disproportionately impacted by the proposed improvements. A brief case study presented later in this chapter provides an example of why environmental justice should be addressed when evaluating how transportation system changes affect water quality and drainage. The state-of-practice discussion below begins with a broad look at current water quality and drainage engineering practices at the level appropriate for environmental document preparation. Common methodologies and engineering tools used to study water quality and drainage impacts are presented systematically, along with recommended approaches on how to extend these methods to allow for effective environmental justice assessment. Links to Web sites and other information are provided for those seeking more detailed information regarding the tools and processes used in the engineering analysis. The methods discussion draws connections between environmental justice issues and the engineering analyses associated with water quality and drainage design. Strategies and checklists are presented to help practitioners seamlessly incorporate environmental justice considerations into traditional analyses. The chapter closes with the Camp Coldwater Springs case study as an example of the connections between drainage design and environmental justice. STATE OF THE PRACTICE The current environmental impact analysis process as it pertains to water quality and drainage is made up of five general steps. 1. Evaluate existing conditions. 2. Evaluate regulatory agency jurisdiction and requirements. 3. Evaluate impacts to groundwater quality and quantity. 4. Evaluate water quality impacts to natural water bodies. 5. Evaluate water quantity impacts to natural water bodies. Each project will require its own unique level of emphasis for each of the general steps listed above. The following is a short summary of the components that make up the evaluations required for an environmental effects analysis. 121

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Evaluating existing conditions This evaluation includes identifying the overall project limits for potential build and no-build options. The evaluation must be of sufficient detail to identify surface drainage patterns. An understanding of the topography of the project area and of points "downstream" of the project limits must be developed for a successful evaluation. Typical resources used for this evaluation include the following: Aerial photos and contour maps (either commissioned specifically for a given project or provided by local government planning/engineering departments); Geographic information system (GIS)-based mapping (generally provided by local government planning/engineering departments); National Wetland Inventory; State public waters information; United States Geological Survey (USGS) quadrangles; and City and county drainage information. Field investigation and verification of the mapping information also should be conducted as part of this evaluation. The existing conditions evaluation should include the modeling of runoff in the project area based on current surface topography and soils/pavements, as well as on improvements such as ponds, pipes, and channels. A common modeling approach is presented in the "Evaluating water quality impacts to natural water bodies" discussion on page 124. Evaluating regulatory agency jurisdiction and requirements This component involves developing a list of all local, regional, state, and national agencies that may have an interest in the project based on the scope of the affected area. The delineation of this area should include the project limits and downstream areas. Agencies involved may be either stakeholders or regulating agencies. Agency jurisdictions and concerns will often overlap, and open communication among agencies is necessary to ensure that project requirements are complementary, not contradictory, to each other. Tables 5-1 and 5-2 list typical agencies that might be included and their respective areas of concern. This part of the evaluation typically requires several meetings with the stakeholder agencies to compile their specific concerns and requirements, as well as to determine which permits will be required as part of the project. A complete understanding of the cumulative agency requirements is necessary to develop the scope of the proposed improvements as they relate to water resource issues. Evaluating impacts to groundwater quality and quantity Typical groundwater impacts occur as a result of construction dewatering process improvements that involve permanent excavations below the existing groundwater table. Dewatering processes may result in infiltration of pollutants into the groundwater from runoff or ponding areas. 122

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Table 5-1. Local and regional coordinating agencies for water quality and drainage Soil & water Coastal Area of Watershed Lake conservation shoreline concern Municipalities organizations associations districts organizations Water quality Water quantity System design and connections Best management practices Groundwater quality Shoreline erosion control Habitat Table 5-2. State and federal coordinating agencies for water quality and drainage Natural Pollution Area of resources control Corps of 1 2 3 concern agency agency EPA FEMA Engineers U.S. FWS Water quality Water quantity NPDES4 regulations and guidelines Wetland Conservation Act Navigable waters Floodplains Wildlife habitat Fisheries Lakes and streams 1. United States Environmental Protection Agency 2. Federal Emergency Management Agency 3. United States Fish and Wildlife Service 4. National Pollutant Discharge Elimination System 123

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Permanent excavations may ultimately alter groundwater elevations in the project area. Analysis should include estimated rates and volumes associated with groundwater infiltration from pond areas and groundwater exfiltration into sewers, ponds, and subdrainage systems. Generally, groundwater quality is not adversely affected by infiltration from storm water detention basins collecting runoff from roadway areas. Recharge from storm water pond infiltration is often beneficial to groundwater. Special cases such as runoff from industrial sites and/or the presence of chemicals, such as deicing fluids from airport operations, in the runoff stream may cause regulating agencies to require measures to limit infiltration. Existing pollutants in the soils located between water quality ponds and groundwater tables may also cause agencies to require limitation measures. Modeling tools commonly used for evaluating groundwater impacts include the following: FEFLOW (Finite Element Flow): This program provides an advanced 2-dimensional and 3-dimensional environment for performing complex groundwater flow, contaminant transport, and heat transport modeling. GMS 4.0 (Groundwater Modeling Software): GMS is a comprehensive program with tools for every phase of a groundwater simulation, including site characterization, model development, post-processing, calibration, and visualization. Evaluating water quality impacts to natural water bodies Typical water quality impacts to natural water bodies include the introduction of pollutant-laden sand and silt into runoff streams that originate from impervious or paved surfaces. Phosphorus is a commonly targeted pollutant; however, metals and salts are also found in runoff generated from roadway surfaces. Typical water quality treatment options include the construction of sedimentation ponds, infiltration areas, and hydraulic structures, such as grit chambers, to remove pollutant-laden sediments from the runoff stream. Many municipalities and watershed organizations require that water quality ponding improvements be constructed to conform to the National Urban Runoff Program (NURP) standards. However, requirements may vary depending on the area of the country and on existing conditions prior to improvement. The most common limiting factor for water quality improvements is the availability of land to construct water quality ponds. This can be especially problematic in developed corridors. Modeling tools to evaluate water quality impacts are commonly used in conjunction with topographic maps and land use and zoning information. The most commonly used model is the P8 Urban Catchment Model. P8 is a U.S. Environmental Protection Agency (EPA) computer model for predicting the generation and transport of stormwater runoff pollutants in urban watersheds. Continuous water-balance and mass-balance calculations are performed on a user- defined system consisting of watershed, particle classes, water quality components, and storage and treatment devices. Evaluating water quantity impacts to natural water bodies Water quantity impacts on natural water bodies often include stream erosion and higher flood levels on streams, wetlands, and lakes. These impacts are mostly due to increased rates of runoff 124