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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.
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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.
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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
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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
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