GIS SUPPORT TO INVESTIGATION OF GROUNDWATER CONTAMINATION

A CASE STUDY

ABSTRACT

The South Well Field, a significant groundwater supply source for the city of South Bend, Indiana, has contaminant concentrations (dissolved solvents) approaching the Safe Drinking Water Act (SDWA) Maximum Concentration Limits (MCLs). On March 18, 1997, the Mayor of the City of South Bend, Indiana wrote the Environmental Protection Agency (EPA) requesting assistance concerning the South Well field groundwater contamination. During October 1997, the EPA initiated a groundwater investigation to identify the types and concentrations of groundwater contaminants in the vicinity of the South Well Field. Data from the groundwater investigation will be used in the design of an interim treatment system for the South Well Field. This report outlines the project methodology, how Geographic Information Systems data could be used to support the investigation and analysis of the groundwater contamination, and the author's development of Arcview graphical outputs to supplement textual analysis and reporting. References are located at the Bibliography.

INTRODUCTION

The South Well Field is part of South Bend, Indiana's drinking water supply system. It provides drinking water to approximately 16,000 residents and is identified in the City's Master Plan as a significant water supply source. Until recently, the South Well Field has had only intermittent use. However, during periods of high use in recent years, the city has had to tap into the well field. In summer of 1996, the City of South Bend identified contaminant concentrations (dissolved solvents) approaching the Safe Drinking Water Act (SDWA) Maximum Concentration Limits (MCLs) during periods of high water use. In accordance with the SDWA, March 18, 1997, the Mayor of South Bend contacted the US Environmental Protection Agency (EPA) for assistance. The EPA subsequently asked the United States Army Corps of Engineers to assist in the investigation of the Chippewa Avenue Area Groundwater Contamination Site (Chippewa Site) in South Bend. (Herring, 1998)

At the request of the EPA, the United States Army Corps of Engineers (USACE) agreed to manage an evaluation of the hydrogeologic conditions in the vicinity of the South Well Field. The South Well Field Pre-Design Field Investigation was conducted between November 1997 and January 1998. A concurrent site-wide ground water investigation was conducted between October and November 1997. Results from this site-wide groundwater investigation were used to assist in determination of groundwater flow directions, contaminant concentrations and distributions, and aquifer hydrochemical characteristics. In February 1997, I contacted the project manager to request data for a required semester project for Geology 8056, Geographic Information Systems. The project manager agreed to coordinate with appropriate contacts at the EPA and United States Geological Service (USGS) for approval for my use of the material. Approval was later given. The following paragraphs outline the project methodology, some results, and my use of the provided data to assist in both the semester project and with the USACE project for EPA.

BACKGROUND

Various organizational entities are associated with the initial investigation and analysis of groundwater contamination and development remedial actions to eliminate contamination to safe levels. EPA assembled an Integrated Project Team to provide technical and management assistance. The primary participants are the EPA, USACE - Omaha District, USGS, City of South Bend, and various contractors providing analysis and technical services. The participants and process are shown in Figure 1.

Figure 1. Integrated Project Team Interfaces and Roles

The Environmental Protection Agency

The EPA was established in the Executive Branch as an independent agency in accordance with the Reorganization Plan No. 3 of 1970. The EPA was created to permit coordinated and effective governmental action on behalf of the environment. The EPA endeavors to abate and control pollution systematically, by proper integration of a variety of research, monitoring, standard setting, and enforcement activities. As a complement to its other activities, EPA coordinates and supports research and anti-pollution activities by State and local governments, private and public groups, individuals, and education institutions. The EPA also reinforces efforts among other Federal agencies with respect to the impact of their operations on the environment, and it is specifically charged with making public its written comments on environmental impact statements and with publishing its determinations when those hold that a proposal is unsatisfactory from the standpoint of public health or welfare or environmental quality. (EPA, 1985)

The US Army Corps of Engineers - Omaha District

The Omaha District Office contains two divisions which provide groundwater contamination evaluation support. The Environmental Engineering Division has capabilities for all facets of planning, study, design, analysis, and performance evaluation of water and wastewater facilities. Responsibilities for support of environmental remediation activities include water and soil treatment technologies. For the Chippewa project they are providing the water treatment plant predesign to enable the South Well Field to be used.

The Hydrologic Engineering Division has capabilities to provide traditional hydrologic engineering services (floodplain/floodway analysis, watershed modeling and analysis, water supply analysis, et al), specialties and non-traditional services (landfill cap drainage design, water quality analysis, et al), and support services (water quality and sediment sampling, CADD/GIS applications, et al). For the Chippewa project they are providing water supply analysis, water quality and sediment sampling, and CAD/GIS analysis. (USACE, 1998)

The Indiana District of the US Geological Survey (USGS)

The Indiana District of the US Geological Survey (USGS), located in Indianapolis, Indiana, provided technical assistance to the EPA for the groundwater modeling at the site. The technical assistance included:

The Indiana Department of Environmental Management

The Indiana Department of Environmental Management provided background geohydrologic information on the Chippewa Site, as well as, access to South Bend water treatment and other facilities, and coordinated access to potential industrial originators of contaminants. (Robinson, 1997)

Contractor Support

The USACE retained several contractors under its "Total Environmental Restoration Contract" (TERC) for investigation, design, and implementation of any removal or remedial actions at the Site on behalf of the EPA. The contractors also collated, organized, and provided initial analysis of groundwater sampling and geological data. (EPA, 1997)

Technical Services

Technical Services included aerial imagery interpretation by the EPA's Environmental Sciences Division (ESD) in Las Vegas, Nevada. ESD conducted historical imagery research in the National Archives, imagery interpretation and reporting, and production of a bound supporting document with accompaning annotated imagery. Various laboratories were contracted to provide water chemical analysis. (EPA, 1997)

METHODOLOGY

Remote Sensing Support

As noted earlier, the EPA's Environmental Sciences Division provide historical research imagery to determine potential contamination sources and to fix the construction of contamination sources in time, as well as, location. They then performed a three step process to analyze the data; data identification and acquisition, photographic analysis and interpretation, and graphics and textual preparation. Imagery taken in 1938, 1951, 1957, 1965, 1973, 1987, and 1993 was found. Figure 2 shows the northern section of project area in 1938. Note that the South Field (annotated as the Rum Well Field) is the elliptical object located near the center of the image. Images were scanned with a table top scanner and converted into TIF format files. They were processed for use in this paper using Microsoft Imager software. Imagery is courtesy of the EPA.

Figure 2. 1938 Imagery of South Bend South Well Field Area

Figure 3 is 1993 photography of the entire site. As you would expect, significant residential and, importantly, industrial growth has occurred. The well fields are essentially surrounded by industrial and waste facilities to the south. As we will see, this will be significant locational factor. Also note that the large manufacturing building to the southeast of the well field on the 1993 imagery, is not present on the 1938 imagery.

Figure 3. 1993 Imagery of South Bend South Well Field Area

GIS Support

The USGS provided ARC/INFO (export files), Arcview (shape files), and other digital formats (i.e. JPEG graphics). Universal access was provided via a password protected file transfer protocol (FTP) site. However, the FTP site was difficult to access. After repeated unsuccessful attempts, I coordinated a visit to the USACE. With the assistance of the USACE GIS personnel I attempted to access the information with no success. Contact with USGS resulted in the USGS personnel downloading the data to a USACE computer from their end. The USACE GIS personnel provided me the data in the form of a writable CD-ROM. Export and shape files, with accompaning data, included:

The author compiled the following Arcview maps to accompany the remainder of the text using the USGS source material as original data. The maps were compiled using the Arcview software located in the Computer Laboratory at the University of Nebraska - Omaha, Durham Science Center, between March 16 and April 12, 1998. Some revisions were made in late April. The maps were compiled from the Arcview shape files provided on the CD-ROM. Not all the provided data was used.

Creation of the maps involved using the same procedures provided in the Arcview training received in the GIS course this semester. In short, a view was created, added a theme, selected appropriate data fields, created a legend (modified for appropriate display), and exported the resulting map into a transportable digital form. Once the maps were completed, they were exported in the form of bitmap (.BMP) files. Alternate file type conversion resulted in too large a file size to store on a floppy disk.

Area Overview

The Chippewa Site is approximately four square miles bordered by the U.S. 31 by-pass to the south, the Penn Central Railroad right-of-way to the north, Main Street to the east, and Locust Road/Olive Street on the west in South Bend. Located within the Chippewa Site are the Rum Village and South Well Field municipal drinking water supply wells, the former AM General facility and other nearby potential contaminant sources. Local topography at the southern portion of the Field Investigation area (Ireland Road) slopes gently northward toward the South Well Field and somewhat more steeply westward toward Bowman Creek. (EPA, 1998) Figure 4 shows the land classification, wetlands, streams, and road network at the site and surrounding area. Note the project area is centered on this map (contained in the box) but the area covered is significantly larger than the project study area. This map is to provide overall orientation and illustrate proximity of relative manmade features and surface hydrology relative to the site.

Figure 4. Overview and Landuse Classification

Surface Geography

Field study shows the unconsolidated material underlying the South Well Field consists primarily of undifferentiated glacial outwash material. In general, the subsurface soils in the area are thick sand and gravelly sand sequences that locally contain subordinate gravel and interspersed fine-glacial till units. Additional information collected during the Field Investigations was used to further assess local geology and hydrogeology. Soil cuttings removed from soil borings and soil samples collected using standard split-spoon sampling methods were classified according to soil type by the on-site geologist or hydrogeologist, following Unified Soil Classification System standards. Based on the Field Investigation, subsurface soils in the vicinity of the South Well Field consist primarily of poorly graded sands and gravely sands (little or no fines) to a depth of at least 27 meters (85 feet) below the ground surface (bgs). (EPA, 1998) As indicated above, Figure 5 will provide a consolidated look at both the surface geography and soil types. The soil types will indicate the relative filtering and transmissivity characteristics of the underlying geological structure.

Figure 5. Surface Geography and Soils

 

Hydrology

The South Well Field is located 1.6 kilometers (1 mile) from the southwestern edge of the St. Joseph river drainage basin. A shallow, unconfined aquifer exists within the upper sand unit of the Hilltop Aquifer System in the Field Investigation area. Based on the coarse-grained soil types present in the area, the average hydraulic conductivity of the surficial aquifer is estimated to range from 0.1 to 0.001 centimeters/second. (EPA, 1998) Figure 6 illustrates the locations of the various aquifiers, acquifer thickness, and well locations. The wells are color coded to indicate data collection relationship. Note that one of the thickest sections of the Hilltop Acquifer is the South field Well Site.

Figure 6. Well and Acquifer Data

INVESTIGATION RESULTS

As a result of the EPA directed study, groundwater contaminant plumes from as many as three different locations were identified. Of the plumes identified only one is impacting the South Well field. It contains contaminant concentrations which exceed the MCLs. However, because significant volumes of clean or uncontaminated groundwater from outside the plume area is injected into the acquifer, concentrations of contaminants are expected to remain under the MCL during non-drought, limited production demand, confirming the empirical experiences of the City of South Bend authorities. The USACE - Omaha District is finalizing the data and will present a final report and recommendation to the City and EPA. Additionally, USACE - Omaha District is designing a filtering system to remove contaminants at the well head, to enable complete use of the field by the City of South Bend.

CONCLUSION

Interestingly, I was surprised by some events in my research for this project. Although at least some of the USGS information had been available on the FTP site since early December 1997, the USACE had not accessed it. This was due to several factors:

These problems were highlighted during my request for information support. As a result, training in Arcview as been coordinated for two of the USACE personnel working on the South Bend project and additional software licenses purchased for copies of Arcview. Additionally, they have requested I provide them short term assistance in familiarizing them with the specific data associate with this project and my efforts with it. These criticisms notwithstanding, GIS data ultimately will provide significant support to the effective investigation and documentation of groundwater contamination in the South Bend, Indiana, South Well Field Site.