Ground Water Vulnerability Assessment Predicting Relative Contamination Potential Under Conditions of Uncertainty (1993) / Chapter Skim
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5 Case Studies
5 Case Studies
Pages 135-169
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From page 135... ...
In only one of the cases presented here, Hawaii, are attempts made to quantify the uncertainty associated with the assessment results. IOWA Introduction Ground water contamination became an important political and environmental issue in Iowa in the mid-1980s.
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From page 136... ...
to educate policy makers and the public about the potential for ground water contamination, and (3) to provide guidance for planning and assigning priorities to ground water protection efforts in the state.
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The most important factor used in the assessment was thickness of overlying materials which provide natural protection to a well or an aquifer. Other factors considered included type of aquifer, natural water quality in an aquifer, patterns of well location and construction, and documented occurrences of well contamination.
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From page 138... ...
. Further analyses of existing and new well water quality data will be used to clarify relationships between aquifer depth and ground water contamination.
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summarizes the Cape Cod ground water protection program. Defining the Question The Area Wide Water Quality Management Plan for Cape Cod (CCPEDC 1978a, b)
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By the time that the Draft and Final Area Wide Water Quality Management Plans were published (CCPEDC 1978a, b) , an updated method for delineating zones of contribution, using the regional water table map, had been developed.
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From page 141... ...
In 1988, the public agencies named above completed the Cape Cod Aquifer Management Project (CCAMP) , a resource-based ground water protection study that used two towns, Barnstable and Eastham, to represent the more and less urbanized parts of Cape Cod.
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The ground water management experience of Cape Cod has resulted in a better understanding of the resource and the complexity of the aquifer
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From page 143... ...
Public concerns over ground water quality have remained high and were a major factor in the creation of the Cape Cod Commission by the Massachusetts legislature. The commission is a land use planning and regulatory agency with broad authority over development projects and the ability to create special resource management areas.
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With some exceptions for already impaired areas, a differentiated resource protection approach in the vulnerable aquifer setting of Cape Cod has resulted in a program that approaches universal ground water protection.
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From page 145... ...
Overpumping of ground water to meet the growing demands of the urban centers, which accounts for about 80 percent of the state's population, contributes to salt water intrusion in coastal areas. This overpumping is considered the most significant problem for degradation of ground water quality in the state.
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From page 146... ...
, depth to water table, soil permeability, land use, and local hydrogeology. Defining the Question Permeable soils, high net recharge rates, intensively managed irrigated agriculture, and growing demands from urban population centers all pose considerable threat of ground water contamination.
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In 1983, the Florida legislature passed the Water Quality Assurance Act, and in 1984 adopted the State and Regional Planning Act. These and subsequent legislative actions provide the legal basis and guidance for the Ground Water Strategy developed by the Florida Department of Environmental Regulation (DER)
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. Part of the 1983 Water Quality Assurance Act requires Florida DER to "establish a ground water quality monitoring network designed to detect and predict contamination of the State's ground water resources" via collaborative efforts with other state and federal agencies.
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From page 149... ...
In developing maps for their districts, each of the five water management districts (WMDs) used the following criteria: ground water recharge, ground water quality, aquifer vulnerability, ground water availability, influence of existing uses on the resource, and ground water supply.
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For example, the St. Johns River WMD used a GIS-based map overlay and DRASTIC-like numerical index approach that rated the following attributes: recharge, transmissivity, water quality, thickness of potable water, potential water expansion areas, and spring flow capture zones.
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From page 151... ...
Two bills related to the implementation of the Bluebell program are being considered by the 1993 Florida legislation. THE SAN ~IOAQUIN VALLEY Introduction Pesticide contamination of ground water resources is a serious concern in California's San Joaquin Valley (SJV)
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Public concern over pesticides in ground water resulted in passage of the California Pesticide Contamination Prevention Act (PCPA)
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One of these mandates requires that monitoring studies be conducted in areas of the state where the contaminant pesticide is used, in other areas exhibiting high risk portraits (e.g., low organic carbon, slow soil hydrolysis, metabolism, or dissipation) , and in areas where pesticide use practices present a risk to the state's ground water resources.
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From page 154... ...
Currently, California has 182 PMZs involving five registered pesticides. California has pursued this mechanical approach to assessing ground water vulnerability to pesticides for reasons that cover a spectrum of political, economic, and practical concerns.
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From page 155... ...
The obvious contamination scenario is the normal scenario in the eastern SJV, and because of its size it creates a huge management problem. While more sophisticated methods for assessing ground water vulnerability have been developed, a question that begs to be asked is "How would conversion to the use of enhanced techniques for evaluating ground water vulnerability improve ground water protection policy and management in the SJV?
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From page 156... ...
Ground water contamination is of special concern in Hawaii, as in other insular systems, where alternative fresh water resources are not readily available or economically practical. Salt water encroachment, caused by pumping, is by far the biggest source of ground water contamination in Hawaii; however, nonpoint source contamination from agricultural chemicals is increasingly a major concern.
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From page 157... ...
The reality, however, is that past, present, and future agricultural, industrial, and military activities present potentially significant ground water contamination problems in Hawaii. Since 1977 when 1,874 liters of ethylene dibromide (EDB)
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UPOLU POINT KAW·~- ~j ~-1-' HILO BAY {HILO At\ ~ KAI LUA 11~ 010) PAHOA ~ ALAPANA ~ ~ G ~ ~ D 1 ~O - DRINKING WATER SOURCES I ~/\ - IRRIGATION SOURCES 8~: O - INDUSTRY SOURCES NAALEHU ~5 0 5 10 15 20 ~r ~- _ , ~ - DRINKINC/INDUSTR~ SOURCES KAUNA POINT ~SCALE IN MrLES FIGURE 5.6b The occurrence and distribution of ground water contamination on the Island of Hawaii.
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From page 159... ...
B~< SANDS ~1 _~: Kit C 1 0 1 2 3 4 5 6 Db~ SCALE IN MILES HANALEI KAPPA 2 ~34 ~ ,~) LIHUE HANAPEPE POIPU ~ ~ G E: 1\1 D - DRINKING WATER SOURCES /\ - IRRIGATION SOURCES FIGURE 5.6d The occurrence and distribution of ground water contamination on the Island of Kauai.
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Approaches Researchers have embarked on several parallel approaches to quantitatively assess the vulnerability of Hawaii's ground water resources, including: (1) sampling, (2)
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From page 161... ...
The pesticide leaching assessment maps developed by Khan and Liang (1989) are intended for incorporation into the regulatory process.
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Motivation for the development of the vulnerability index was provided by two specific questions: 1. Given limited resources and the geographic diversity of the water quality problems associated with agricultural production, what areas of the country have the highest priority for study and program implementation?
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In areas where the water table is near the surface, these predictions relate directly to shallow ground water contamination. In other areas a time lag is involved.
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Geological Survey is working to measure the quality of surface and ground water resources under its National Water Quality Assessment Program. At the conclusion of the project, survey information will be combined with what is learned in other elements of the President's Water Quality Initiative to assess the magnitude of the agriculture-related water quality problem for the nation as a whole and used to evaluate the potential economic and environmental effects of Initiative policies of education, technical assistance, and financial assistance if implemented nationwide.
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From page 165... ...
The Cape Cod approach to ground water vulnerability assessment is perhaps one of the oldest and most sophisticated in the United States. Driven by the need to protect the sole source drinking water aquifer underlying this sandy peninsula, the vulnerability assessment effort has focused on the iden
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From page 166... ...
In addition, several monitoring networks have been established to assess background water quality and monitor actual effects in areas identified as highly vulnerable. The coupling of ground water vulnerability assessments with monitoring and research efforts, provides the basis of an incremental and evolving ground water protection program in Florida.
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Final Area Wide Water Quality Management Plan for Cape Cod. Barnstable, Massachusetts: Cape Cod Commission.
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1991. Ground Water Quality Monitoring Network.
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1991. Use of a Geographic Information System to Assess Risk to Ground-Water Quality at Public-Supply Wells, Cape Cod, Massachusetts.
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