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PUBLIC HEALTH ASSESSMENT

DELAVAN MUNI WELL #4
DELAVAN, WALWORTH COUNTY, WISCONSIN


SUMMARY

Groundwater in the Delavan area is contaminated with VOCs (volatile organic compounds). This VOC contamination was measured in Delavan municipal water, from 1983 through 1993, but is not an apparent public health hazard because VOCs were not at levels that pose a health concern. Delavan Well No. 4 is an indeterminate public health hazard for past human exposures to contaminated drinking water. Delavan residents were evidently exposed to municipal water contaminated with VOCs prior to 1982, but it is not possible to determine the level and duration of their exposures. In June 1993, a treatment system came online that removes contamination from the water. Contaminated groundwater is not an apparent public health hazard for private well users in the Delavan area. No Delavan-area homes were identified that obtain contaminated drinking water from private wells. Three Delavan businesses have wells contaminated with low levels of VOCs that are not a health concern.

The full extent of contaminated groundwater in and around Delavan has not been determined and needs to be characterized. Any newly discovered, existing private wells in the Delavan area should be evaluated or tested for VOC contamination. Any new private wells installed in the Delavan area should also be evaluated or tested for VOC contamination.

Ambient air exposure to VOCs from a storm sewer carrying treated water away from Sta-Rite Industries, a nearby manufacturer, is an indeterminate public health hazard. Adequate air sampling has not been conducted inside and adjacent to the storm sewer covers, as recommended in the Preliminary Public Health Assessment for Delavan Well No. 4. Air samples should be collected from inside the storm sewers and at storm sewer access covers to provide data which can be used to more fully evaluate possible human exposures to VOCs in ambient air.

Sediments in Swan Creek, where treated water from Sta-Rite leaves the storm sewer, contained VOCs at levels that are not a health concern. Surface water and sediments in a five-acre pond, located immediately adjacent to the Sta-Rite property, should be tested for contamination. This is a data gap.

Delavan Well No. 4 is one of several municipal wells serving the City of Delavan, located in Walworth County, Wisconsin. In early 1982, Well No. 4 was found to be contaminated with several VOCs, and three months later the use of Well No. 4 was halted. Delavan Well No. 4 was designated a Superfund site in 1984. Sta-Rite was identified as the probable source of the contamination. In 1983, the nearby Delavan Well No. 3 was also found to be contaminated with VOCs, but this well was not removed from service. In 1990, a decrease in contaminant levels prompted the City of Delavan to return Well No. 4 to normal use. To keep concentrations of specific VOCs below Wisconsin groundwater standards, the City was required to blend water from Well No. 4 with water from other wells. In 1993, a new treatment facility began processing water from Wells No. 3 and No. 4, removing all measurable contamination. No community health concerns relating to Delavan Well No. 4 have been reported.


BACKGROUND

A. Site Description and History

Site Description

    Delavan Well No. 4 is located in the City of Delavan, Walworth County, Wisconsin, (Figure 1) and is owned by the City of Delavan. Well No. 4 is found within the southeast ¼ of Section 17, T2N, R16E, in the Town of Delavan. This Superfund site is defined as "the contaminated aquifer used by the Delavan Well No. 4" [47]. Delavan Well No. 4 was nominated to the federal National Priorities List in 1983 and officially placed on the NPL in 1984 [33].

    The land around Delavan has moderate topographic relief with a gently rolling surface. This area was glaciated during the most recent glacial period. Local soils consist of glacial till, with moraine and outwash deposits. Surface water in the area drains into Turtle Creek, which flows west and enters the Rock River, over 20 miles to the west of Delavan. The terrain in the vicinity of Well No. 4 is fairly flat, and Comus Lake is approximately 5,000 feet to the northwest. The depth to groundwater around Well No. 4 is approximately 35 feet, and the general flow of groundwater in the area is reported to be to the northwest, towards Comus Lake [64, P4.13].

History

    In 1981 the City of Delavan municipal water supply system consisted of three high-powered, high-capacity wells, two elevated storage reservoirs, and a distribution network of pipes. All municipal wells drew water from the shallow sand and gravel aquifer. Pumping records from 1979, 1984, and 1987 show that water use for Delavan was 230, 294 and 270 million gallons annually [13] [28]. In 1981, Well No. 4 pumped an average of 12 million gallons per month, roughly one-third of the City of Delavan's municipal water needs. Well No. 4 was constructed in 1968, is 115 feet deep and has a capacity of 680 gallons per minute. In 1981 Well No. 3 pumped a monthly average of 7.4 million gallons (Figure 3). Well No. 3 is 130 feet deep and has a capacity of 680 gallons per minute. One elevated reservoir has a capacity of 150,000 gallons and the second, which is near Well No. 3, has a capacity of 250,000 gallons. A one-million gallon elevated reservoir is planned for construction in a business park east of Well No. 4.

    In March 1982, the Wisconsin Department of Natural Resources (DNR) reported that Delavan municipal Well No. 4 was contaminated with five volatile organic compounds (VOCs). This testing by the DNR was part of a first-time U. S. Environmental Protection Agency sponsored survey that examined VOC contamination in 144 community water supplies throughout Wisconsin [24]. One of the contaminants found in Well No. 4, trichloroethylene (TCE), was measured at 130 µg/L (Table 1). This level exceeded the then state health advisory for TCE of 45 µg/L. Other VOC contaminants were detected in the well water, but all were below Wisconsin health advisory levels in place at that time and not a health concern. Consequently, the City of Delavan halted use of Well No. 4 in July 1982 [33]. This DNR testing also found TCE in Delavan Wells No. 2 and No. 5, but at only trace levels (less than 1 µg/L) [24]. There were no reports that contamination was found again in these wells.

    In August 1982, one month after Well No. 4 was taken offline, water samples were collected from taps at the nearby Wileman Elementary School, the Delavan city hall, and the Delavan high school. TCE was not found in these samples; analysis was not performed for other VOCs.

    Delavan Well No. 3, located approximately 1,000 feet west of Well No. 4 (Figure 2), was first tested for VOCs in September 1982, and no contamination was found. However, in June 1983 low levels of TCE and another VOC were detected in water samples collected from the well [12]. Since that date, water samples collected from Well No. 3 have frequently shown the presence of TCE and other VOCs.

    In March 1984, TCE (at 27 µg/L) was the only contaminant found in Well No. 4, and no contamination was detected in Well No. 3. These changes in contaminant concentrations could have been affected by the changes in pumping rates of the two municipal wells and the clean-up and control of the apparent contaminant sources at Sta-Rite. Between August 1983 and February 1984, there were dramatic changes in the monthly pumping rates of both wells. After February 1984 the pumping rate of Well No. 4 was dropped to a standby basis and the use of Well No. 3 increased. In September 1984, Well No. 3 pumped a reported 22.9 million gallons (Figure 3). It was not until the Fall of 1984 that the first extraction wells on the Sta-Rite property became operational.

    The source of VOC contamination in Well No. 3 has not been identified, but Well No. 3 and Well No. 4 may share one or more of the same sources of contamination. Well No. 3, was first tested for VOCs in September 1982, but no contamination was detected. Concern was expressed by the DNR, in July 1983, that major changes in pumping rates of Wells No. 3 and No. 4 could influence the movement of the suspected contaminated groundwater plume(s), possibly resulting in contaminated water being drawn toward Well No. 3.

    In 1984 groundwater modeling suggested high pumping rates would be necessary at Well No. 3 to draw contaminated groundwater from the Sta-Rite property [43, P3.3]. Contamination was not found in Well No. 3 until after pumping rates were decreased for Well No. 4 and increased for Well No. 3 (Figure 3). The highest level of TCE detected in Well No. 3 (230 µg/L) was in August 1983, the same month Well No. 4 was decreased to a standby rate and Well No. 3 was almost doubled above average production levels.

    Capture zone modeling on Well No. 3 and Well No. 4, conducted by an environmental consultant, indicated it was plausible for these wells to be drawing contaminated groundwater from some of the same sources [62]. A sampling history of both wells show the presence of certain VOCs (including TCE) with similar variations in concentrations through time.

    The City of Delavan halted use of Well No. 4, in July 1982, four months after finding contamination and relied more heavily on water pumped by Well No. 3. Well No. 4 continued to be pumped at a slightly decreased rate (approximately 6.5 million gallons per month), but the water was discarded (Figure 3). After July 1982, the pumping rate of Well No. 3 was increased from 7 to 10.5 million gallons per month. The pumping rates of Wells No. 2 and No. 5 were also increased in July 1982. In January 1984, the pumping rate of Well No. 4 was decreased to a standby rate of approximately 400,000 gallons per month.

    The preliminary public health assessment for Delavan Well No. 4 was issued by the Agency for Toxic Substances and Disease Registry (ATSDR) in June 1989 [41]. The preliminary health assessment concluded the site was a potential public health concern because "of the risk to human health caused by the possibility of exposure to hazardous substances via contaminated municipal drinking water from Well No. 4." The document recommended that Well No. 4 not be used to provide drinking water for residents of the City of Delavan, except in an emergency and only if blended with water from other wells. The Site Review and Update for Delavan Well No. 4 was released by ATSDR on September 30, 1993. This update report concluded that the site was an indeterminate public health hazard and recommended that a full public health assessment be conducted on the site [41].

    In April 1990 environmental consultants recommended the City of Delavan return Well No. 4 for normal use on an unrestricted basis. The consultant reported a decline in VOC contaminant levels observed in Well No. 4 over the previous few years [15]. This decline was attributed to the removal of contaminant sources or the installation of extraction wells at the Sta-Rite property. Their recommendation was also based on pump test results Well No. 4 which were conducted by the City of Delavan in 1989.

    As a result the DNR authorized the City of Delavan to return Well No. 4 to normal use in May 1990. However, the DNR recommended that Well No. 4 be "operated as a lag pump and blended with water from Well No. 3" because TCE continued to be present in Well No. 4 at concentrations slightly below the Wisconsin Groundwater Quality Enforcement Standard of 5 µg/L [30]. Pumping records indicate that Well No. 4 was returned to normal use in late 1990.

    Well No. 6 came on-line in July 1993, is over 1,500 feet deep and draws water from a separate aquifer isolated by bedrock from the shallower aquifer used by other city wells. The City of Delavan built a one million gallon storage tank in the Delavan Business Park, 4,000 feet northeast of Well No. 4, and became operational in January 1996. At the site of Wells No. 3 and No. 6 is a 250,000 gallon storage tank, and the City has no plans to replace it in the foreseeable future.

    In June 1993 the City of Delavan brought a new water treatment facility on-line that treats water provided by wells No. 3, No. 4, and the new Well No. 6. This facility is located next to wells No. 3 and No. 6. The facility includes a stripping tower for water from Well No. 4, an aeration system for water from wells No. 3 and No. 6, and an iron removal component for all three wells. The Delavan Director of Utilities reported the first tests of post-treatment water in June 1993 showed no detectable levels of VOC contamination.

    After the discovery of VOC contamination in Well No. 4 in 1982, the City of Delavan and DNR attempted to identify the source of the contamination [11]. The DNR surveyed ten businesses operating in the vicinity of Well No. 4 to determine which used TCE [25]. Sta-Rite Industries, located east of Well No. 4 and directly across Wright Street (Figure 2) previously reported to the City of Delavan and DNR their historical use of TCE in their manufacturing processes [66].

    STA-RITE INDUSTRIES

    Sta-Rite (Sta-Rite Industries, Inc.) has manufactured submersible water pumps and other products in Delavan since 1958. In 1990, Sta-Rite was the largest manufacturing employer in Walworth County with 525 employees [56, P4.1] [17]. Operations at the Wright Street Sta-Rite property occur in two buildings: Plant No. 1 was constructed in 1958 and Plant No. 2 was built in 1968 (Figure 2).

    Sta-Rite reported use of various VOC solvents in Delavan from 1960 till 1977 [56]. Sta-Rite recycled and evaporated spent solvents; however, the handling and disposal of some solvents apparently resulted in contamination of soils and groundwater under and in the vicinity of the Sta-Rite property. The principal solvent used at Sta-Rite was TCE, though other solvents used included PCE (tetrachloroethylene). TCE was used at Plant 1 as a paint thinner and degreaser from 1960 to 1977 [66]. At Plant 2 TCE was used for cleaning and degreasing from 1968 till 1977 [56, P4.1]. Though Sta-Rite reports continued use of solvents, their use has been decreased and are recycled. Sta-Rite began recycling spent solvents in 1976 [56, P4.4].

    The soils and groundwater at both of these Sta-Rite plants were contaminated with VOCs. At Plant 1 a series of floor drains and catch basins were used to collect spilled and spent solvents. Contamination may have entered into the ground through cracks in catch basins [64, P2.7]. The liquid collected from the catch basins drained into the Sta-Rite storm sewage system, along with non-contact cooling and pump-test wastewater. Prior to 1982, this storm sewer ultimately discharged into an open drainage ditch system. This open drainage system started south of Plant 1, and liquid in it flowed west to the eastern edge of Wright street and south to a marshy area south of Plant 2.

    Overflow from the marshy area went through a culvert, under Wright street and into a vacant lot south of Well No. 4. In 1982 Sta-Rite connected their storm sewer system into the recently installed Delavan municipal storm sewer system [61, P2.7], and is currently covered by a Wisconsin Pollutant Discharge Elimination system permit [31]. Since connecting to the Delavan storm sewer, there are no accounts of spent manufacturing solvents being discharged into the Delavan storm sewer because Sta-Rite reports solvent use was decreased and they began recycling spent solvents in 1976 [56, P4.4].

    A single sump at Plant 2 received waste liquids. This sump was a series of manhole sections without a bottom section. Liquids emptied into the sump discharged directly into the ground [61, P2.6] [66]. The depth to groundwater under the Sta-Rite facility was reported to be approximately 35 feet below the surface [59, P1.1]. The sump at Plant 2 was identified in 1983 by a Sta-Rite contractor as a likely source of contamination affecting municipal well No. 4 [70].

    INVESTIGATIONS AND FOLLOW-UP ACTIVITIES

    There have been a number of investigations as a result of the contamination found at the Sta-Rite property. For a complete account of these investigations refer to the original documents or the detailed summary of previous investigations in the Sta-Rite Remedial Investigation Report [64, P2.14].

    A report released in early 1983 described VOC contamination of sub-surface soils on and groundwater under the Sta-Rite property, and indicated Plant 2 as a possible source of the contamination found at well No. 4 [64, P2.14] [70]. These contaminated soils were removed in November 1983 [33, P7].

    A subsequent investigation in May 1983 was unable to identify the path of contaminants from Plant 2 to well No. 4. The report did indicate a plume of contaminated groundwater was evidently migrating away from Plant 1 and to the northwest, which is the general direction of local groundwater flow [40]. The report concluded that VOC contaminated groundwater near Plant 1 had little to no effect on Well No. 4 [33, P4].

    A contractor modeled groundwater contamination at Sta-Rite and described in a 1983 report that up to three plumes are migrating away from the Sta-Rite property. This report concluded Well No. 4 is only affected by contamination from Plant 2, and that most of groundwater contaminants found at Plant 2 are not drawn by Well No. 4. The report also concluded that contamination from Plant 1 is not being drawn by either wells No. 3 or No. 4, and the contamination detected in well No. 3 is probably not coming from the Sta-Rite property [41, P15]. The DNR raised several issues in response to this report, most notably of the need to determine the full extent of groundwater contamination coming from the Sta-Rite property and how this contamination might be affecting present and future water supplies [27]. An engineering consulting firm working for the City of Delavan also responded to the report and questioned the accuracy and the sensitivity of the model [71].

    In 1984 and 1985 seven groundwater extraction wells were installed on the Sta-Rite property [67]. Five wells were installed around Plant No. 1, and ultimately, two extraction wells were installed at Plant No.2. Table 5 describes the PCE and TCE concentrations found in water from each extraction well. Releases by Sta-Rite of contaminated extraction water into surface water has been permitted by the DNR, under the Wisconsin Pollutant Discharge Elimination System. The extracted water, which contains VOC contaminants, is disposed into the Delavan storm sewer. Water from four of the extraction wells (EX-1, EX-2, EX-3, and EX-7) is sprayed into the storm sewer [65, P3.21]. Spraying is intended to hasten the evaporation of VOC contaminants from the water. Water from the other wells is poured into the storm sewer. Sta-Rite is required monthly to collect and analyze samples of extraction well water discarded into the Delavan storm sewer system [31].

    An April 1984 report prepared by a consultant for Sta-Rite concluded that contamination affected only the upper portion of the aquifer and contaminated groundwater flowed northwest towards Comus Lake, and because of this reported that "Sta-Rite believes it is not necessary to implement an extensive groundwater monitoring program to define the exact plume boundaries." The report recommended: the installation of a groundwater extraction system to control contaminated groundwater; additional monitoring wells near Plant 1; and a soil flushing and groundwater extraction system near the sump area at Plant 2 [43, P4].

    Soils in the sump area, next to Plant No. 2, had elevated levels of VOCs. A soil flushing system was in operation at this location from 1984 till 1988. Water flushed through the soil was discharged into the storm sewer. In May 1988 a vapor extraction system that vents soil gas into the atmosphere was installed here [33, P7].

    Pump testing was conducted in 1989 by the City of Delavan on Well No. 4 to evaluate the changes in contaminant concentration during moderate use of the well over 30 days. As a result of these tests the capture zone of Well No. 4 was estimated by an engineering contractor to only include Plant 2. The subsequent report suggested Plant 1 to be "hydraulically isolated" from Delavan Well No. 4 [55].

B. Site Visits

In conjunction with the Southeast DNR District office, two representatives of the Wisconsin Division of Health (DOH), Henry Nehls-Lowe and Chuck Warzecha, visited Delavan on April 13, 1993. The site visit team met with staff from Delavan Water Works, received an overview of the status of the water supply system for the City and the plans to bring the new well and treatment facility online. Leaving the Water Works office, the team passed by the Delavan School for the Deaf located on the west side of Delavan. Students at this school could be a potentially sensitive population to adverse health effects from exposure to contaminated drinking water (see Demographics on page 8). Upon arriving at Well No. 3, the team toured the adjacent, new water treatment facility in the final stages of construction. Next to this facility is Well No. 6, which was scheduled to come on-line within eight weeks. It was noted that Wileman School is immediately south of this location.

After leaving the treatment facility, the team went northwest and onto the 900 block of Ann Street. The DNR has determined that two bulk storage fuel facilities at this location (the former Mobil Oil and Mudlaf/Standard Oil site) have contaminated nearby soils and groundwater with fuel products. Both of these facilities are approximately 500 feet west-northwest of Well No. 3 and are being cleaned up under the authority of the Wisconsin Environmental Repair Statute. In addition to contamination by fuel products, VOCs (including PCE and TCE) were also found in groundwater under and around this site. The site visit team then drove around the Sta-Rite property, noting the locations of monitoring and extraction wells, including Well No. 4 across Wright Street.

DOH received reports that local residents collected drinking water from a spring located on the northwest side of the City of Delavan, adjacent to a cemetery and next to Lake Comus. On April 11, 1995, two DOH staff, Henry Nehls-Lowe and Chuck Warzecha, visited Delavan and collected a water sample from the spring. Laboratory analysis of the sample found trichloroethylene at 6.3 µg/L. Based on this information, the City of Delavan took action that halted use of the spring by removing a pipe that protruded from the ground [22].

A home owner, living less than one-half mile northeast of the Delavan city limits, expressed concern about possible contamination of her well. On July 26, 1995, two DOH staff, Henry Nehls-Lowe and Chuck Warzecha, collected a water sample from this private well. Laboratory analysis of the sample found no detectable VOC contamination [23].

C. Demographics, Land Use, and Natural Resource Use

Demographics

    Delavan Well No.4 is in the City of Delavan. The 1990 census determined there were 5,387 residents of Delavan. In 1984 the City of Delavan reported that 1,564 households were served by the municipal water system [13], providing domestic water to an estimated 4,200 people (assuming 2.7 persons per household). Approximately 94 percent of the population is white, with a median age of 36.7 years, and an average household income of $33,760 [10].

    The Baseline Risk Assessment identified five potentially sensitive populations within one mile of the site. This includes a day care and preschool, two private schools, a public elementary school, and a nursing home (Figure 2) [60, P3.1]. Also within the City is the Delavan School for the Deaf, which is operated by the Wisconsin Department of Public Instruction. This school receives its water from the Delavan municipal water system. During the school year approximately 180 students, from 6 to 21 years of age, attend this school. Most students reside at the school from Sunday evening till Friday afternoon and many have multiple handicaps and related health problems [19], which might make them more susceptible to the effects of VOC contaminated drinking water.

Land and Natural Resource Use

    Well No. 4 is located in a commercial and industrial area on the southeast side of Delavan. The area surrounding Delavan Well No. 4 is made up of a number of different zoning types, as designated by the City of Delavan. Immediately east of the well and across Wright street is an area of industrial zoning, which includes the Sta-Rite property. Further east of Sta-Rite and north of Highway 43 is a recently constructed industrial park, on which only a few structures were present at the time of the April 1993 site visit. Directly north and northwest of Well No. 4 is a commercial/industrial zoned area with a mixture of light industries located on Ann Street. North of Ann Street is a railroad right-of-way, with residences immediately beyond the track. South of Well No. 4 is a mixed pattern of residential, industrial and commercial properties. Immediately south of Well No. 4 is an apartment building that was constructed in 1962. Across Wright street from the apartment building is a strip shopping mall. Approximately 1,000 feet southwest of Well No. 4 and directly south of Well No. 3 is Wileman Elementary School. One and one-half miles southeast of the site is a dog racing track. Less than 500 feet southeast of the Sta-Rite property is a five-acre pond, where there is evidence that people fish. Fishing and boating are also popular activities on Comus Lake, located approximately 4,900 feet northwest of the Sta-Rite property.

    Agriculture is a major activity beyond the city limits of Delavan. Over 65 percent of land in Walworth county is farmland, of which dairy farming is the most significant agricultural activity [17].

    In the Delavan area, groundwater is the source of most water used for domestic and agricultural purposes (except for irrigation). Outside of the Delavan city limits, most nearby households obtain water from private wells.

D. State and Local Health Data

"Health Outcome Data" refers to records of death and illness. A review of health outcome data may be appropriate when there is evidence people living near a Superfund or contaminated site have been exposed to hazardous substances at levels which could lead to an increase in rates of death or disease. A review also may be appropriate if there are reports of unusual clusters of disease near the site or due to specific community health concerns.

As discussed later in the Pathways Analysis section, Delavan residents have apparently been exposed to contaminated water pumped by Wells No. 3 and No. 4. However, it is unclear if people were exposed to contaminated water for a duration and at levels that might plausibly result in deaths or illness. The Wisconsin Department of Health and Family Services, Division of Health, has not received any reports of clusters of chronic disease or cancers in the vicinity of this site. The available data systems that could be used to investigate if elevated levels of illness and/or death are discovered include the Wisconsin Cancer Reporting System, the vital statistics records of births and deaths in Wisconsin, and the Wisconsin Birth and Development Outcome Monitoring Program.


COMMUNITY HEALTH CONCERNS

No community health concerns have been received about Well No. 4 by the Walworth County Human Services agency nor the Wisconsin Division of Health.


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