Water: Coastal Zone Act Reauthorization Amendments
B. Water Quality Assessment Management Measure
Assess water quality as part of marina siting and design.
This management measure is intended to be applied by States to new and expanding marinas. Under the Coastal Zone Act Reauthorization Amendments of 1990, States are subject to a number of requirements as they develop coastal nonpoint source programs in conformity with this measure and will have some flexibility in doing so. The application of management measures by States is described more fully in Coastal Nonpoint Pollution Control Program: Program Development and Approval Guidance, published jointly by the U.S. Environmental Protection Agency (EPA) and the National Oceanic and Atmospheric Administration (NOAA) of the U.S. Department of Commerce.
Assessments of water quality may be used to determine whether a proposed marina design will result in poor water quality. This may entail predevelopment and/or postdevelopment monitoring of the marina or ambient waters, numerical or physical modeling of flushing and water quality characteristics, or both. Cost impacts may preclude a detailed water quality assessment for marinas with 10 to 49 slips (See Economic Impacts of EPA Guidance Specifying Management Measures for Sources of Nonpoint Pollution in Coastal Waters.) A preconstruction inspection and assessment can still be expected, however. Historically, water quality assessments have focused on two parameters: dissolved oxygen (DO) and pathogen indicators. The problems resulting from low DO in surface waters have been recognized for over a century. The impacts of low DO concentrations are reflected in an unbalanced ecosystem, fish mortality, and odor and other aesthetic nuisances. DO levels may be used as a surrogate variable for the general health of the aquatic ecosystem (Thomann and Mueller, 1987). Coastal States use pathogen indicators, such as fecal coliform bacteria (Escherichia coli) and enterococci, as a surrogate variable for assessing risk to public health through ingestion of contaminated water or shellfish (USEPA, 1988) and through bathing (USEPA, 1986).
Dissolved Oxygen. Three important factors support the use of DO as an indicator of water quality associated with marinas. First, low DO is considered to pose a significant threat to aquatic life. For example, fish and invertebrate kills due to low DO are well known and documented (Cardwell and Koons, 1981). Second, DO is among the few variables that have been measured historically with any consistency. A historical water quality baseline is extremely useful for predicting the impacts of a proposed marina. Third, DO is fundamentally important in controlling the structure and, in some areas, the productivity of biological communities.
Pathogen Indicators. Marinas in the vicinity of harvestable shellfish beds represent potential sources for bacterial contamination of the shellfish. Siting and construction of a marina or other potential source of human sewage contiguous to beds of shellfish may result in closure of these beds. Also, nearby beaches and waters used for bathing should be considered.
Fecal coliform bacteria, Escherichia coli, and enterococci are used as indicators of the pathogenic organisms (viruses, bacteria, and parasites) that may be present in sewage. These indicator organisms are used because no reliable and cost-effective test for pathogenic organisms exists. Water quality assessments can be used to ensure that water quality standards supporting a designated use are not exceeded. For example, in waters approved for shellfish harvesting, a marina water quality assessment could be used to document potential fecal coliform concentrations in the water column in excess of the standard of 14 organisms MPN (most probable number) per 100 milliliters of water. This standard should not be exceeded in areas where the exceedance would result in the closure of harvestable or productive shellfish beds. Many States have adopted EPA's 1986 ambient water quality criteria for bacteria, which recommend E. coli and enterococci as indicators of pathogens for freshwater and marine bathing.
3. Management Measure Selection
Selection of this measure was based on the widespread use and proven effectiveness of water quality assessments in the siting and design of marinas. The North Carolina Department of Environmental Management conducted a postdevelopment study to characterize the water quality conditions of several marinas and to provide data that can be used to evaluate future marina development (NCDEM, 1990). The sampling program demonstrated that marina water quality monitoring studies are effective at assessing potential water quality impacts from coastal marinas. Water quality assessments have been used successfully at a variety of other proposed marina locations nationwide to determine potential water quality impacts (USEPA, 1992b). Many States require water quality assessments of proposed marina development (Appendix 5A). Marinas with 10 to 49 slips may not be able to afford monitoring or modeling. (See Economic Impacts of EPA Guidance Specifying Management Measures for Sources of Nonpoint Pollution in Coastal Waters.) In such instances a preconstruction inspection and assessment can still be performed. Dredging requires a River and Harbor Act section 10 permit from the U.S. Army Corps of Engineers (USACE). If there is discharge into waters of the United States after dredging, then a CWA section 404 permit is required. A CWA section 401 Water Quality Certification is required from the State before a section 404 permit is issued by the USACE.
As discussed more fully at the beginning of this chapter and in Chapter 1, the following practices are described for illustrative purposes only. State programs need not require implementation of these practices. However, as a practical matter, EPA anticipates that the management measure set forth above generally will be implemented by applying one or more management practices appropriate to the source, location, and climate. The practices set forth below have been found by EPA to be representative of the types of practices that can be applied successfully to achieve the management measure described above.
Two effective techniques are available to evaluate water quality conditions for proposed marinas. In the first technique, a water quality monitoring program that includes predevelopment, during-development, and postdevelopment phases can be used to assess the water quality impacts of a marina. In the second approach, effective assessment can be accomplished through numerical modeling that includes predevelopment and postconstruction model applications.
Numerical modeling can be used to study impacts associated with several alternatives and to select an optimum marina design that avoids and minimizes impacts to both water quality and habitats existing at the site (e.g., Rive St. Johns Canal study and Willbrook Island marina). A combination of field surveys and numerical modeling studies may be necessary to identify all environmental concerns and to avoid or minimize marina impacts on both water quality conditions and nearby shellfish habitat.
- a. Use a water quality monitoring methodology to predict postconstruction water quality conditions.
A primary objective for use of a water quality assessment is to ensure that the 24-hour average dissolved oxygen concentration and the 1-hour (or instantaneous) minimum dissolved oxygen concentration both inside the proposed marina and in adjacent ambient waters will not violate State water quality standards or preclude designated uses.
The first step in a marina water quality assessment should be the evaluation and the characterization of existing water quality conditions. Before an analysis of the potential impacts of future development is made, it should be determined whether current water quality is acceptable, marginal, or substandard. The best way to assess existing water quality is to measure it. Acceptable water quality data may already have been collected by various government organizations. Candidate organizations include the U.S. Geological Survey, the USACE, State and local water quality control and monitoring agencies, and engineering and oceanographic departments of local universities.
The second step in a marina water quality assessment is to set design standards in terms of water quality. In most States, the water quality is graded based on DO content, and a standard exists for the 24-hour average concentration and an instantaneous minimum concentration. A State's water quality standard for DO during the critical season may be used to set limits of acceptability for good water quality.
The best way to assess marina impacts on water quality is to design a sampling strategy and physically measure dissolved oxygen levels. During the sampling, sediment oxygen demand and other data that may be used to estimate dissolved oxygen levels using numerical modeling procedures can be collected (USEPA, 1992c, 1992d). A postdevelopment field program may include dye-release and/or drogue-release studies (to verify circulation patterns) and a water quality monitoring program. Data collected from such studies may be used to assist in the prediction of water quality or circulation at other potential marina sites.
Sampling programs are effective methods to evaluate the potential water quality impacts from proposed marinas. The main objective of a preconstruction sampling program is to characterize the water surrounding the area in the vicinity of the proposed marina. Another objective of a preconstruction sampling program is to provide necessary information for modeling investigations (e.g., Tetra Tech, 1988).
- b. Use a water quality modeling methodology to predict postconstruction water quality conditions.
Water quality monitoring can be expensive, and therefore a field monitoring approach may not be practical. The use of a numerical model may be the most economical alternative. However, all models require some field data for proper calibration. A better and more cost-effective approach would be a combination of both water quality monitoring and numerical modeling (Tetra Tech, 1988).
Modeling techniques are used to predict flushing time and pollutant concentrations in the absence of site-specific data. A distinct advantage of numerical models over monitoring studies is the ability to easily perform sensitivity analyses to establish a set of design criteria. Limits of water quality acceptability, flushing rates, and sedimentation rates must be known before quantifying the limit of geometric parameters to comply with these standards. Numerical models can be used to evaluate different alternative designs to determine the configuration that would provide for maximum flushing of pollutants. Models can also be used to perform sensitivity analysis on the selected optimum design.
In 1982, preconstruction numerical modeling studies were conducted to investigate whether a proposed marina in South Carolina would meet the State water quality standards after construction. Modeling results indicated that the proposed Wexford Marina would meet water quality standards (Cubit Engineering, 1982). The marina was approved and constructed. Follow-up monitoring studies were conducted to evaluate preconstruction model predictions (USEPA, 1986). The monitoring results indicated that shellfish harvesting standards were being met, thereby validating the preconstruction modeling study.
EPA Region 4 recently completed an in-depth report on marina water quality models (USEPA, 1992c). The primary focus of the study was to provide guidance for selection and application of computer models for analyzing the potential water quality impacts (both DO and pathogen indicators) of a marina. EPA reviewed a number of available methods and classified them into three categories: simple methods, mid-range models, and complex models. Simple methods are screening techniques that provide only information on the average conditions in the marina. Screening methods do not provide spatial or time-varying water quality predictions, and therefore it is recommended that these methods be used with open marina designs and/or marinas sited in areas characterized by good flushing rates and good water quality conditions (USEPA, 1992c). In addition, simple models are not suitable where marina flushing is controlled by the prevailing wind, requiring the application of more advanced models, such as WASP4.
In poorly flushed areas and in marinas with a complex design, a more advanced method will identify those areas where water quality standards may be violated. The complex methods are also capable of predicting spatial and time-variant water quality conditions and provide the complete water quality picture inside a proposed marina. In general, advanced models are more effective and more appropriate than simple screening methods in assessing environmental impacts associated with marina siting and design (USEPA, 1992c).
Costs associated with applying a numerical model or conducting a water quality monitoring program range from 0.1 to 2.0 percent of the total marina development project cost. Table 5-2 (14k) provides cost information by marina, size, State, and year built. These factors should all be considered when comparing a particular cost associated with a specific item. For example, costs associated with the water quality monitoring program for Barbers Point Harbor and Marina complex were estimated at $56,000. On the other hand, the cost of the water quality monitoring program for the Beacons Reach marina, North Carolina, was $3,000. It was only when a full environmental assessment was conducted (e.g., North Point and Barbers Point marina complex) that costs were higher. In addition, several models have been recommended as appropriate tools to assess potential water quality impacts from coastal marinas (USEPA, 1992c, 1992d). The cost associated with applying the simple model is on the order of $1,000, whereas the cost associated with the advanced model is in the range of $25,000 to $100,000. Siting and design practices to reduce environmental impacts were frequently part of a larger design/environmental study. Costs for a total environmental assessment of a proposed marina ranged from 1 percent to 5 percent of the total project cost.
- c. Perform preconstruction inspection and assessment.
A preconstruction inspection and assessment may be affordable in place of detailed water quality monitoring or modeling for marinas with 10 to 49 slips. The River and Harbor Act of 1899 section 10 and Clean Water Act section 404 permit application process requires applicants to present to the USACE information necessary for a water quality assessment. An expert knowledgeable in water quality and hydrodynamics may assess potential impacts using available information and site inspection.