Wellhead Protection Areas Research Articles

Statistical evidence on the effectiveness of sewering to protect groundwater from VOC contamination

Volatile organic compounds (VOCs) are an important source of contamination of groundwater supplies in Massachusetts and many parts of the United States. One local response is to require sewering in wellhead protection areas as an easily enforceable policy designed to reduce the probability of VOC contamination of groundwater. Data were collected for 238 wellhead protection areas in Massachusetts on VOC contamination levels and the sewered and unsewered land uses in those aquifer recharge areas. Logistic regression procedures were used to see whether sewering had any statistical effect on likelihood of contamination of well water. The results provided limited, but not overpowering, support for the idea that requiring commercial and industrial land uses to use sewers would reduce the chance of VOC contamination.

Intrinsic limitations of standard criteria and methods for delineation of groundwater-source protection areas (spring-head and wellhead protection areas) in carbonate terranes: critical review, technically-sound resolution of limitations, and case study in a Kentucky karst : J. F. Quinlan, J. A. Ray & G. M. Schindel, in: Karst geohazards: engineering and environmental problems in karst terrane. Proc. 5th conference, Gatlinburg 1995,

Intrinsic limitations of standard criteria and methods for delineation of groundwater-source protection areas (spring-head and wellhead protection areas) in carbonate terranes: critical review, technically-sound resolution of limitations, and case study in a Kentucky karst : J. F. Quinlan, J. A. Ray & G. M. Schindel, in: Karst geohazards: engineering and environmental problems in karst terrane. Proc. 5th conference, Gatlinburg 1995,

Management of diffuse pollution in groundwater under imprecise conditions using fuzzy models

This paper presents a framework for evaluation of nitrate control strategies that use spatially variable nitrogen input in the presence of imprecise information. The research stems from the fact that diffuse pollution has caused water consumers to be concerned with reducing the risk posed by contaminated water supplies. An important element in quantifying risk reduction is the use of simulation modeling to predict the transport and fate of contaminants under variable rate application as employed in a wellhead protection area strategy. Specifically, a groundwater model is linked with an unsaturated zone transport (and crop production) model which provides the nutrient and recharge loading rates to the saturated zone. To consider uncertainty stemming from the unsaturated zone model output, in addition to aquifer parameters, a new groundwater modeling technique is developed in which fuzzy set theory is combined with finite-difference modeling methods. The groundwater model incorporates imprecise parameters (i.e., transmissivity) into the modelling process through the use of fuzzy set theory. Imprecision has been encoded directly into the finite-difference equations using fuzzy numbers as input, and level-set operations combined with non-linear optimization are used to solve the system of equations. The resulting fuzzy output can be interpreted as the level of imprecision associated with the model. A case study is presented to illustrate the methodology.

Management of diffuse pollution in groundwater under imprecise conditions using fuzzy models

This paper presents a framework for evaluation of nitrate control strategies that use spatially variable nitrogen input in the presence of imprecise information. The research stems from the fact that diffuse pollution has caused water consumers to be concerned with reducing the risk posed by contaminated water supplies. An important element in quantifying risk reduction is the use of simulation modeling to predict the transport and fate of contaminants under variable rate application as employed in a wellhead protection area strategy. Specifically, a groundwater model is linked with an unsaturated zone transport (and crop production) model which provides the nutrient and recharge loading rates to the saturated zone. To consider uncertainty stemming from the unsaturated zone model output, in addition to aquifer parameters, a new groundwater modeling technique is developed in which fuzzy set theory is combined with finite-difference modeling methods. The groundwater model incorporates imprecise parameters (i.e., transmissivity) into the modelling process through the use of fuzzy set theory. Imprecision has been encoded directly into the finite-difference equations using fuzzy numbers as input, and level-set operations combined with non-linear optimization are used to solve the system of equations. The resulting fuzzy output can be interpreted as the level of imprecision associated with the model. A case study is presented to illustrate the methodology.

Nitrogen Loading Model for Wellhead Protection Areas

Groundwater Monitoring & RemediationVolume 15, Issue 1 p. 69-70 Nitrogen Loading Model for Wellhead Protection Areas Scott W. Horsley, Scott W. Horsley Scott W. Horsley is vice president of Horsley & Witten Inc., an environmental consulting firm specializing in water resources protection with offices in Massachusetts (3179 Main St., Barnstable, MA 02630); Rockville, Maryland; and Seattle, Washington. He serves as a consultant to EPA and state and local governments.Search for more papers by this author Scott W. Horsley, Scott W. Horsley Scott W. Horsley is vice president of Horsley & Witten Inc., an environmental consulting firm specializing in water resources protection with offices in Massachusetts (3179 Main St., Barnstable, MA 02630); Rockville, Maryland; and Seattle, Washington. He serves as a consultant to EPA and state and local governments.Search for more papers by this author First published: February 1995 https://doi.org/10.1111/j.1745-6592.1995.tb00502.xAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume15, Issue1February 1995Pages 69-70 RelatedInformation

Wellhead Protection Area Delineation Using the Analytic Element Method of Ground‐Water Modeling

AbstractThe Analytic Element Method (AEM) of ground‐water modeling was used to delineate wellhead protection areas (WHPAs) for existing and proposed wells in Brooklyn Park, Minnesota by simulating steady‐state flow in two aquifers: the water‐table aquifer (in glacial outwash) and the Franconia‐Ironton‐Galesville bedrock aquifer. Ground‐water time‐of‐travel was used as the delineation criterion. Ground‐water flow is significantly affected by a buried bedrock valley underneath the City. Transmissivity values for the water‐table aquifer are much higher in the buried bedrock valley and the hydraulic connection between the water‐table and the Franconia‐Ironton‐Galesville aquifers is more pronounced. The Analytic Element Method does not utilize a grid mesh and incorporates both regional‐scale and more detailed, local‐scale features in the same solution. This feature of AEM provided for the simulation of the city wells in the context of the regional flow field. Separate models, encompassing an area of approximately 500 square miles, were developed and calibrated for each aquifer using the Single Layer Analytic Element Model (SLAEM) and then linked together using the Multi‐Layer Analytic Element Model (MLAEM). Ground‐water travel‐time zones and WHPAs were delineated for the existing wells using reverse particle tracking.

A Hydrogeologic Field Laboratory for Undergraduate Instruction and Research

A growing national interest in ground-water problems has underscored a need for undergraduate field instruction in hydrogeology and, consequently, the value of a hydrogeologic field laboratory. Such a laboratory can replicate the physical and chemical conditions commonly encountered in assessments of ground-water supply and faced in ground-water monitoring. A field laboratory can be employed to represent features such as test wells for a water supply project, a wellhead protection area, a waste-disposal site, or a leaking underground storage tank. Students can learn how to measure ground-water levels, conduct pumping and slug tests, collect water samples, and monitor water quality. Further, the information obtained during application of investigative methods can provide initial data for subsequent analysis of hydraulic gradient, direction and rate of ground-water flow, hydraulic properties of aquifers (such as hydraulic conductivity, transmissivity, and storativity), chemical characteristics of ground wat...

A GEOGRAPHIC INFORMATION SYSTEMS APPROACH TO WELLHEAD PROTECTION1

ABSTRACT: The 1986 Amendments to the Safe Drinking Water Act mandate a multifaceted approach to wellhead protection. This approach includes: (1) delineating wellhead protection areas; (2) identifying and managing potential contaminants; (3) developing contingency plans in the event of weilfield contamination; (4) siting new wells; and (5) encouraging public participation. These elements encompass technical, administrative, and educational considerations. In functioning both as a research tool and as a decision support system, a geographic information system (GIS) is shown to have proven utility in addressing these issues. This article describes the application of common GIS functionality in facilitating a comprehensive wellhead protection scheme for an agricultural municipality in North Dakota.

Effects Of Fracture Density And Anisotropy On Delineation Of Wellhead-Projection Areas In Fractured-Rock Aquifers

Most wellhead protection studies in fractured-rock aquifers rely on the assumption that the aquifer approximates a porous medium at the scale of the wellhead protection area. Significant errors can result if the assumption is incorrectly applied. Some authors have developed theoretical and subjective criteria for determining when the porous-media approximation is appropriate. Most of these criteria, however, require detailed field work to test the validity of the porous-media approximation. Experiments have been carried out with Roucleau's two-dimensional discrete fracture flow model coupled with a particle-tracking code to determine when the porous-media approximation is appropriate for delineating the capture zone of a well drilled in fractured rock. Specifically, the effects of anisotropy and fracture density on the capture-zone determination have been examined. It has been found that, even in densely fractured aquifers, the zone of contribution determined by the fracture-flow model is significantly larger than the capture zone determined by porous-media-based models.

Geographic information systems: a tool for strategic ground water quality management

Abstract Geographically‐related information is needed for several elements of an integrated ground water quality management programme, including ground water monitoring planning, prioritization of pollution sources, usage of permits and inspections for source control, and planning and completion of remedial actions. Geographic Information Systems (GISs) can be used to support these elements along with delineating wellhead protection areas (WHPAs), prioritizing existing contaminant sources and evaluating proposed changes in land usage in such areas. Eight case studies of the use of GISs in wellhead protection programmes are summarized, including examples from Rhode Island, Mississippi, New Jersey, New York, Pennsylvania, Kansas, Massachusetts and Texas. Six additional examples are mentioned relative to the use of GISs for evaluating ground water pollution potential, facilitating data analysis for environmental restoration of a large area with numerous waste sites, evaluating trends in ground water nitrate ...

THE DEVELOPMENT AND IMPLEMENTATION OF A GIS‐BASED CONTAMINANT SOURCE INVENTORY OVER THE SPOKANE AQUIFER, SPOKANE COUNTY WASHINGTON1

ABSTRACT: U.S. Environmental Protection Agency (EPA) statutes require identification of all potential sources of contamination within a wellhead protection area. All wells over Spokane County's aquifer are included in one wellhead protection zone called the Aquifer Sensitive Area (ASA).A GIS‐based Contaminant Source Inventory (CSI) was developed for the ASA. Datasets listing businesses and agencies within the ASA were imported into the GIS from state, county, city, and local agencies. These datasets were selected, joined, and sorted using GIS relational database capabilities into one ASA “business master file.” Map files were projected and transformed into common coordinates. Next, business sites within the master file were spatially related by address to the digital map files. Likely Critical Materials Users (CMU) were identified by sorting on selected standard Industrial Codes (SIC). Additional files of CMUs were imported into the Contaminant Source Inventory. GIS queries were performed to locate specific materials, quantities, and storage facilities, and to analyze CMU activity within selected buffer zones.This project demonstrated the usefulness of GIS technology in the development, management, maintenance, and analysis of vast quantities of data associated with a local wellhead protection pro. gram.

Uncertainty in wellhead protection area delineation due to uncertainty in aquifer parameter values

The importance of modeling in hydrogeologic investigations has been stressed in a number of studies. Since the applicability of any model is dependent on the type of need and availability of hydrogeological information, a parametric analysis is essential to determine its applicability. This paper presents the results of a parametric analysis conducted to evaluate the effect of data uncertainty on wellhead protection area (WHPA) delineation. The precision of aquifer parameter values is the most important factor in a WHPA delineation process in relation to the model itself. To demonstrate the effect of variable values in a wellfield, we tested modified version of time-related analytical groundwater flow concept using a RESSQC model, which is used for capture zone delineation and to delineate contaminant front for injection wells. The RESSQC model is a modified version of the RESSQ code which was initially designed to only delineate contaminant fronts for injection wells. Field measured aquifer parameters for a shallow aquifer were used in the analysis. The results indicate that great caution must be taken when aquifer parameters such as hydraulic gradient, thickness, transmissivity and porosity are being used for WHPA delineation, since over or under-protection of WHPA can jeopardize the public health. An extended aquifer test and installation of various observation wells in or near different lithologic and depth zones may increase reliability of parameter values.

A Geographic Information System (GIS) User Interface for Delineating Wellhead Protection Areas

AbstractDigital tools such as Geographic Information Systems (GIS) store, analyze, map, and illustrate large amounts of diverse electronic data. This paper develops a GIS modeling user interface for delineating Wellhead Protection Areas (WHPAs) around public water‐supply wells. With this modeling interface, the user can extract the necessary information from the GIS database automatically. The GIS database can then store the delineated WHPAs for further analysis and display. The modeling interface allows local agencies to delineate and manage WHPAs for hundreds of wells more efficiently and effectively than with the traditional paper maps and overlay system.In order to demonstrate the efficiency of the user interface, this paper presents a wellhead delineation pilot study for the City of Houston. WHPAs for the 202 active public water‐supply wells in the city were delineated using GIS and the modeling interface. Detailed sensitivity analyses were completed to evaluate the effect of uncertainty in model parameters on the delineated WHPAs. Potential sources of contamination within the delineated WHPAs were then identified using the GIS database.While GIS are perceived as an important tool that can enhance a user's ability for spatial data analyses, they have many problems. The system hardware and software require a substantial investment in financial and human resources. Database development is a tricky process requiring planning and commitment; in most cases, the anticipated outcome from GIS software development is not immediately realized.

Coupled Simulation‐Optimization Modeling for Municipal Ground‐Water Supply Protection

AbstractA technique based on numerical ground‐water flow modeling and unconstrained nonlinear optimization has been developed to provide guidance for protecting municipal ground‐water supplies from contamination through capture zone management. The technique involves conventional finite‐difference ground‐water flow modeling and numerical flowpath/travel time calculation coupled with nonlinear mathematical programming. The objective of the technique is to specify pumping rates for wells in a wellfield such that the configuration of capture zones in relation to existing potential sources of contamination minimizes the risk of contamination while maintaining the required total water output from the wellfield. An important feature of the technique is its ability to incorporate realistic boundary conditions, complicated aquifer configurations, and spatially varying aquifer properties to whatever degree site‐specific data are available. Also, the technique is implemented on a personal computer. This approach to ground‐water supply protection enhances conventional wellhead protection area delineation because a greater level of protection can be achieved if potential contaminant sources are not even included in capture zones, rather than attempting to reduce the threat of those sources. The effectiveness of the technique was verified through application to a hypothetical ground‐water system. Practical aspects were demonstrated with an application in Pékin, Illinois. These efforts demonstrate the utility of an innovative modeling technique in ground‐water quality protection.

Wellhead Protection Area Delineation: Linking Flow Model with GIS

The protection of areas that contribute water to public wells (wellhead protection areas or WHPAs) is an important component of the Rhode Island Department of Environmental Management (RIDEM) ground-water protection strategy. An accurate, scientifically based WHPA delineation is the first step in wellhead protection. RIDEM has chosen to use the Uniform Flow analytical model, in conjunction with hydrogeologic mapping, for WHPA delineation around large public supply wells completed in stratified drift in Rhode Island. Geographic information system (GIS) calculates variables for input into the model, transforms model output into geographically referenced data layers, and provides mylar overlays for final hydrogeologic mapping of the WHPA. RIDEM hydrogeologists provide study area boundaries, run the model on a personal computer- (PC-) based program, and delineate the final WHPA on mylar overlays. Maps of the WHPAs and other hydrogeologic data will be provided to communities and water suppliers and will be the basis for local wellhead protection planning required under the Rhode Island Wellhead Protection Program.

Delineation of Wellhead Protection Areas: Theory and Practice

A preventive approach in groundwater protection programs throughout Europe and the United States, and almost unknown in Brazil, is to define the surface and subsurface areas, the Wellhead Protection Area (WHPA), from which a well or wellfield draws its water during a specified time. Overlaying a map of potential pollution sources on the delineated WHPA (Figure 1), those sources which fall within the WHPA boundaries are identified as definite threats, that need to be closely monitored, to the continued safe operation of the wellfield. Given the importance of effectively delineating the WHPA to protect public water supplies, the current delineation criteria, methods, and zones are presented, as well as analytical and numerical PC model analyses of different hydrogeological scenarios' effects on WHPA's size, shape and direction. Numerical models are shown to more accurately define WHPAs by taking into account the surrounding heterogeneous and anisotropic geology.

Development and Applications of a Wellhead Protection Area Delineation Computer Program

In the last few years, groundwater management has concentrated on the protection of groundwater quality. An increasing number of countries has adopted policies to protect vital groundwater resources from deterioration by regulating human interaction with the subsurface, the use of potential contaminants, land use restrictions, and waste transport and storage. One of the more common regulatory approaches to the protection of groundwater focuses on public water supplies to reduce the potential of human exposure to hazardous contaminants. Under the framework of the Safe Drinking Water Act amended by U.S. Congress in 1986, The U.S.EPA (1987) issued guidelines for the delineation of wellhead protection areas, recommending the use of analytical and numerical models for the identification of such areas. In this study, the theoretical background for the development of one such numerical model is presented. Two real-world applications are discussed: in the first case history, the model is applied to a Superfund Site in Puerto Rico as a tool for assessment of the effectiveness of a proposed pump-and-treat scheme for aquifer remediation. Based on simulation results for the evolution of the existing contaminant plume it was verified that such a scheme would not work with the proposed purging wells. The second case history is the delineation of a wellhead protection area in the Town of Littleton, Massachusetts, and subsequent design of a monitoring well network.

Ground Water Monitoring at Wellhead Protection Areas

AbstractWellhead protection programs implemented to this date have not, in general, included a comprehensive ground water monitoring strategy. This is due both to the relatively recent introduction of the wellhead protection concept into the ground water field and also to the complexity of the monitoring problem. A well‐planned monitoring program, however, can contribute significantly to the success of a wellhead protection program. The elements of wellhead protection, important from a monitoring perspective, are the management objectives, the types of potential contaminant sources, and the locations of those sources with respect to the wellhead protection area boundary. General monitoring strategies applicable to wellhead protection are derived from the relationships between these elements.

WHPA Code available

The Wellhead Protection Area code is now available for distribution by the International Ground Water Modeling Center in Indianapolis, Ind. The WHPA code is a modular, semianalytical, groundwater flow model developed for the U.S. Environmental Protection Agency, Office of Ground Water Protection, designed to assist state and local technical staff with the task of Wellhead Protection Area (WHPA) delineation. A complete news item appeared in Eos, May 1, 1990, p. 690.The model consists of four independent, semianalytical modules that may be used to identify the areal extent of groundwater contribution to one or multiple pumping wells. One module is a general particle tracking program that may be used as a post‐processor for two‐dimensional, numerical models of groundwater flow. One module incorporates a Monte Carlo approach to investigate the effects of uncertain input parameters on capture zones. Multiple pumping and injection wells may be present and barrier or stream boundary conditions may be investigated.

WHPA Code available

The Wellhead Protection Area (WHPA) code is now available for distribution by the International Ground Water Modeling Center in Indianapolis, Ind. The WHPA code is a modular, semi‐analytical, groundwater flow model developed for the U.S. Environmental Protection Agency, Office of Ground Water Protection. It is designed to assist state and local technical staff with the task of WHPA delineation.The model consists of four independent, semi‐analytical modules that may be used to identify the areal extent of groundwater contribution to one or multiple pumping wells. One module is a general particle tracking program that may be used as a post‐processor for two‐dimensional, numerical models of groundwater flow. One module incorporates a Monte Carlo approach to investigate the effects of uncertain input parameters on capture zones. Multiple pumping and injection wells may be present and barrier or stream boundary conditions may be investigated.