24    INVESTIGATION OF INGROUND BIOLOGICAL
TREATMENT FOR GROUNDWATERS CONTAMINATED
WITH VOLATILE ORGANIC COMPOUNDS
Robert W. Peters, Assistant Professor
Wendy L. Oresik, Graduate Student
School of Civil Engineering
Purdue University
West Lafayette, Indiana 47907
Bruce Minsley, Deputy Utilities Director
Department of Public Utilities
Kalamazoo, Michigan 49001-2898
INTRODUCTION
The Kalamazoo Public Utility operates a water supply system consisting of 116 wells and 25 pump
stations, providing an average of 17 million gallons per day. The groundwater supply is derived from a
series of aquifers "consisting of unconsolidated deposits of gravel, sand, silt, and clay, characteristic
of glacial deposits".1 The glacial deposits generally lie between 6.1-12.2 m (20-40 ft) below the surface
and extend to 61.0m (200 ft).
In late 1980, the State of Michigan Department of Public Health initiated a routine, statewide
trihalomethane monitoring program. An unexpected result of this program was the detection of 10
parts per billion (ppb) of tetrachloroethylene in the waters from one pump station, Station No. 1. The
Utility proceeded to immediately survey the remaining pump stations for the presence of volatile
organic contaminants. The results of this survey indicated one other station, Station No. 11, had low
levels of 1-5 ppb of 1,2-dichloroethane and cis-l,2-dichloroethylene. Because of these compounds
and the low concentrations found, the Michigan State Health Department, along with the Kalamazoo
Public Utility, decided to merely monitor the levels of contaminants at Station 11. A full scale
hydrogeologic contaminant investigation at Station 1 was instituted.
During the first quarter of 1981, the Kalamazoo Public Utilities instituted a system wide monitoring
of its 15 well fields for volatile organic compounds (VOC's). Station 11 was one of two well fields
found during this first round of sampling to contain VOC's. Concentrations of 1-2 ppb of cis-1,2-
dichloroethylene and dichloroethane were observed at Station 11. In January 1982, a third well field
began to show low levels of trichloroethane contamination. In concurrence with the State of Michigan
Department of Public Health, the Utility continued to use Station 11 while performing hydrogeologic
investigations leading to remedial action measures for the other two stations.2'3 Because contaminant
levels had not changed during one year's monitoring at Station 11, the new contamination problem at
the third well was given higher priority and on-going monitoring was maintained for Station 11.
Station 11 finally was elevated in priority in late 1984, when routine sampling began to show the
presence of vinyl chloride, a known carcinogen. In 1985, the Utility initiated a hydrogeologic investigation to determine the scope, source(s), and potential remedial action(s) for Station 11. Vinyl
chloride was detected at a concentration level of 2 ppb in the discharge from Station 11. This finding
resulted in Station 11 being removed from operation and relegated to emergency use only.
WELL FIELD CHARACTERISTICS
Station 11 is located in a residential and open space area in the west central section of the City of
Kalamazoo, near the Western Michigan University campus. The well field began production in 1954.
Figure 1 is a map showing the location of the various wells of concern in this study. The well field is
protected by a minimum 30m (100 ft) sanitary isolation zone on all sides. The aquifer is in an area
referred to as the Kalamazoo-Portage Groundwater Reservoir.' This aquifer consists of "coarse sand
and gravel beds forming an upper aquifer and two lower aquifers, which are separated by beds
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