PUBLIC HEALTH ASSESSMENT
SHERWOOD MEDICAL COMPANY
NORFOLK, MADISON COUNTY, NEBRASKA
The Sherwood Medical Company plant is south of Norfolk, Nebraska, on U.S. Highway 81 in northwestern Madison County. The plant produces medical syringes and blood-collection systems. Volatile organic compounds (VOCs) from chlorinated solvents used in clean-up operations at the plant have been released into groundwater at the site. VOCs have migrated from the site into private wells north and northeast of the plant including the drinking water wells at the adjacent Park Mobile Home Court.
The Agency for Toxic Substances and Disease Registry (ATSDR) has determined that site-related contamination currently poses no apparent public health hazard because available information indicates that current exposures are not expected to cause adverse health effects. However, past exposures to VOC-contaminated groundwater posed a public health hazard to residents of the Park Mobile Home Court. Residents of the mobile home park who used water from the park's wells for domestic purposes were exposed to numerous VOCs by ingesting contaminated drinking water, by breathing VOCs that volatilized into the air during showering and bathing, and, to a lesser extent, by absorbing VOCs through the skin when showering and bathing.
The owners and employees of two downgradient commercial operations and three government operations were likely exposed to low levels of VOCs by ingesting drinking water from their water supply wells. However, the levels of VOCs found in their wells do not pose a public health hazard.
Employees of the Sherwood Medical plant may have been exposed to VOCs via ingestion of contaminated drinking water before the facility's carbon treatment system was installed. Although VOCs were found in the plant's supply wells at levels of public health concern, the level of contaminants actually present in drinking water consumed by the plant's employees is not known. Plant employees who used and handled chlorinated solvents on the job were also potentially exposed to VOCs, primarily 1,1,1-trichloroethane, through inhalation and skin absorption.
Other persons who might be exposed to VOCs include business owners and employees and residents with private wells near the site that are not currently affected by site contaminants but that could become contaminated in the future. The public health significance of such potential exposures is not known.
The community health concerns discussed in this public health assessment primarily involve worker exposure. ATSDR has referred those concerns to the state office of the Occupational Safety and Health Administration, U.S. Department of Labor.
On the basis of the findings of this public health assessment, ATSDR has made recommendations to reduce or prevent exposure of private well users and plant workers to site-related contaminants.
ATSDR has determined that no follow-up health activities are indicated at this time for the site. However, ATSDR will reevaluate the site for appropriate follow-up activities if future data or information indicates that human exposure to site contaminants is occurring at levels of public health concern or that past exposure to site contaminants is causing adverse health effects.
The Agency for Toxic Substances and Disease Registry (ATSDR), whose headquarters are in Atlanta, Georgia, is a federal agency within the U.S. Department of Health and Human Services and is authorized by the Comprehensive Environmental Response, Compensation, and Liability Act of 1980 (CERCLA) to conduct public health assessments of hazardous waste sites. Under the authority of CERCLA, ATSDR has conducted this public health assessment of the Sherwood Medical Company site, which is listed on the U.S. Environmental Protection Agency (EPA) National Priorities List (NPL). ATSDR has evaluated the public health significance of this site; more specifically, ATSDR has considered whether health effects are possible and has recommended actions to reduce or prevent possible health effects.
The Sherwood Medical facility is south of Norfolk, Nebraska, approximately 1 mile from the southern city limit, on U.S. Highway 81 in northwestern Madison County (Figures 1 and 2, Appendix A). The plant was built by Brunswick Corporation in 1961. The facility operated as Roeher Products from 1961 to 1968, when Brunswick changed the name to Sherwood Medical Company. Initially, the plant produced hypodermic needle assemblies; in 1974, production of glass blood-collection assemblies was added. In 1982, Sherwood Medical Company was purchased by American Home Products (1).
As shown in Figures 2 and 3, Sherwood Medical is bordered on the north by the Park Mobile Home Court (PMHC). This mobile home park currently has about 50 occupied units and several vacant units. The maximum capacity of the PMHC is 117 units (2).
In October 1987, routine sampling by the Nebraska Department of Health (NDOH) discovered various volatile organic compounds (VOCs) in the main well at the Park Mobile Home Court. The NDOH resampled the well, which provided drinking water to the park's residents, in November 1987 and confirmed the presence of VOCs. Upon discovering that the well was contaminated, the NDOH notified the Nebraska Department of Environmental Control (NDEC), which in turn reported the contamination to the EPA regional office (1).
From November 1987 to January 1989, the NDOH and EPA sampled local wells several times. VOCs, including trichloroethylene (TCE), 1,1,1-trichloroethane (1,1,1-TCA), 1,1-dichloroethane (1,1-DCA), and tetrachloroethylene (PCE), were found in Sherwood Medical Well #5 (used for industrial purposes) and the main well of the mobile home park (3).
Using CERCLA emergency funds, EPA supplied bottled water to the mobile home park residents beginning in February 1988. Later that month, EPA installed a temporary carbon treatment system on the park's main well, eliminating the need for bottled water (3). In December 1988, EPA notified Sherwood Medical that it was considering the company a potentially responsible party (PRP) for the groundwater contamination at the mobile home park. Sherwood Medical then entered into a Removal Action Administrative Order (AO) with EPA in September 1989, and agreed to assume responsibility for supplying the mobile home park's residents with an alternative water supply (2). During that month, Sherwood Medical connected the mobile home park to a new carbon treatment system that used water from the plant's supply wells (3). This treatment system, which replaced the previous temporary system, continues to provide drinking water to the mobile home park residents and also supplies treated water for use within the Sherwood Medical plant.
The Sherwood Medical plant uses polypropylene in its injection molding process to produce syringe components. Blood collection systems are assembled from purchased components. From 1963 until December 1992, the plant used chlorinated solvents, primarily 1,1,1-TCA, to clean its tool-and-die equipment and injection molds. (Note: Use and on-site disposal of 1,1,1-TCA by Sherwood Medical was first noted during a Resource Conservation and Recovery Act (RCRA) inspection in January 1988 (5).) Facility floor drains, including those in the boiler and tool and die rooms, originally discharged spills and wash-down water to Sherwood Lake, a pond on the Sherwood Medical property. Those rooms are the principal areas where chlorinated solvents were used in the past (1). All use of chlorinated solvents by the Sherwood Medical plant was discontinued in December 1992 (4).
In 1967, the boiler room and tool and die room floor drain lines were redirected to an existing plant septic tank. At that time, a concrete settling basin was installed ahead of the septic tank to settle out metal cuttings and oils washed into the floor drains during plant operations. Effluent from the septic tank discharged to two leach fields until 1969, when they began losing their infiltration capacity. As a result, a third leach field was installed north of the other two fields. To ensure that the new leach field would not develop the same oil clogging problems as the previous fields, a 2,000-gallon, steel underground storage tank (UST) was installed and connected to the concrete settling basin. A skimmer line was installed in the UST, which allowed floating oils to be removed from the liquid wastes before discharge to the leach field. Oily liquids were periodically pumped out of the UST and removed by a waste oil hauler (1).
In 1974, Sherwood Medical Company built a sewage treatment plant (STP) and stopped using the septic tank and leach field system. At that time, all wastewater lines, except those from the boiler and tool and die rooms, were redirected to the new STP, which discharges to Sherwood Lake. The boiler and tool and die room lines continued to drain to the concrete settling basin and UST; however, the discharge line from the UST to the leach field was disconnected. As before, oily liquids that accumulated in the UST were periodically pumped out and removed by a waste hauler (1).
In July 1988, Ecology and Environment Inc. (E&E), an EPA contractor, conducted Phase I of an expanded site investigation (ESI) of the Park Mobile Home Court groundwater contamination. The investigation included a soil gas survey of the area and environmental sampling of Sherwood Lake (water and sediment) and Sherwood Medical wastewater discharges. In January 1989, E&E completed Phase II of the ESI, including a soil gas survey and sampling of residential drinking water wells in the area. The purpose of the two investigations was to determine the source of the Park Mobile Home Court well contamination (1).
In September 1989, under the terms of an EPA-approved removal action work plan, the concrete settling basin and UST were taken out of service. Both the boiler room and tool and die room floor drain lines were redirected to the facility STP. The liquid and solid wastes in the settling basin and UST were pumped out, sampled, and placed in on-site containers. The settling basin and UST were then pressure washed; the resulting washwater also was pumped out and put in containers on site. No problems related to the integrity of either the concrete settling basin or UST were observed during removal activities. The facility septic tank also appeared to be sound. However, holes were observed in portions of the 3-inch polyvinyl chloride (PVC) piping between the concrete settling basin and the UST, suggesting that liquid wastes may have been released into surrounding soil. In November 1990, the facility septic tank also was emptied, pressure washed, and removed from service under an addendum to the removal action work plan. Liquids and sludges removed from the septic tank were sampled (1).
Sherwood Medical Company entered into a Remedial Investigation/Feasibility Study (RI/FS) Administrative Order (AO) with EPA in March 1991. Stage I and IB RI field activities were conducted from April to October 1991 by the Mittelhauser Corporation. RI activities included drilling and installation of groundwater monitoring wells on and off the Sherwood Medical property and collection of 1) subsurface soil samples (during well installation); 2) groundwater samples from monitoring wells, plant supply wells, and off-site private wells; 3) plant wastewater discharge samples; 4) surface water and sediment samples from Sherwood Lake; and 5) soil gas samples. The groundwater samples from Stage I and IB field activities are referred to as Round 1 and 2 samples, respectively (2).
In December 1991, an additional series (Round 3) of groundwater samples was taken from the on- and off-site monitoring wells, plant supply wells, and off-site private wells (6).
In April and May 1992, a final series (Round 4) of groundwater samples was collected from selected background and on-site monitoring wells as part of a Metals Verification Test (MVT). The purpose of the MVT, which was conducted in accordance with an approved EPA sampling plan, was to characterize the mobile fraction of metals present in site groundwater (7,8).
Stage II of the RI was conducted in June 1992 in order to define the presence and extent of soil contamination at four suspected source areas. During Stage II, 25 soil borings were drilled on site and soil samples from the borings were collected and analyzed for VOCs (7,8).
In September 1993, EPA issued a Record of Decision (ROD) for the Sherwood Medical Company site that presented EPA's selected remedy for addressing VOC soil and groundwater contamination at the site. The major components of the selected remedy include 1) potable drinking water for the residents of the Park Mobile Home Court and other properties with contaminated wells; 2) removal of the plant's old underground storage tank, concrete settling basin, and septic tank, and treatment of associated soils, if necessary; 3) excavation and low-temperature thermal treatment of contaminated soils from the CS/CN area; 4) extraction and treatment (air stripping) of contaminated on-site and off-site groundwater; 5) groundwater monitoring, and accelerated groundwater treatment if drinking water standards are not met within 5 years; and 6) deed restriction to prohibit installation and use of water supply wells in the contaminated portion of the aquifer on the plant property (9).
ATSDR staff members Roberta Erlwein, Steve Richardson, Bill Greim, and Don Gibeaut visited the site and surrounding area on January 15 and 16, 1992. Observations made and information obtained during the visit are described in appropriate sections of this document.
Numerous single-family residences are adjacent to the Sherwood Medical site (Figures 2 and 3). Approximately 50 occupied mobile homes are in the Park Mobile Home Court along the northern Sherwood Medical property line. The main well for the mobile home park is about 1,500 feet northeast of the plant entrance. A single-family residence is on U.S. Highway 81 approximately 1,100 feet north of the plant entrance. Other single-family residences are just south of the Sherwood Medical property along Sherwood Road. The closest residence to the plant is approximately 300 feet from the plant entrance on Sherwood Road. The Park Mobile Home Court and Sherwood Road residents range in age from young children to senior adults. It should be noted that the residential wells along Sherwood Road are considered to be upgradient of the site; the Park Mobile Home Court wells are downgradient (10).
The city of Norfolk, Nebraska, which is about 1.5 miles north of the site, has a population of 21,476 (U.S. Census, 1990). Norfolk has grown by about 10% since the 1980 census, and is expected to continue to grow at about the same rate (10).
The region south of Norfolk is predominantly open, sparsely populated, agricultural land. However, near the Sherwood Medical site are several industrial and commercial facilities and private residences (Figures 2 and 3) (2). Immediately west of the site, across U.S. Highway 81, is the Karl Stefan Airport (Norfolk Municipal). There are two wells at the airport--one at the main airport building and another at the Midplains Aviation Inc. building. Because those wells are upgradient from the Sherwood Medical plant, they are not likely to be affected by contaminants from the plant (10).
Immediately east of the Sherwood Medical plant along Sherwood Road is Easy Blend Manufacturing, Inc. (formerly Ron Kinning Inc.), and Theisen Brothers Inc., a heavy-duty construction company with a private water supply well. East of Theisen Brothers is a storage area owned by Nebraska Harvester Systems Inc. (7,10).
North and northeast of the Park Mobile Home Court are two small commercial operations with private wells. Water from those wells is used primarily to wash down industrial equipment. Because the wells are downgradient of the Sherwood Medical plant, they are subject to being affected by groundwater contaminants from the site (10). As shown in Figures 2 and 3, other commercial wells are nearby. The existence of commercial wells near the mobile home park suggests that additional commercial and industrial development of this area is possible.
Agricultural land use is prevalent in areas surrounding the Sherwood Medical plant. It has been reported that 1,580 acres of irrigated land are within 3 miles of the site. Most of that land is used to grow corn as feed for livestock (3,10). However, the land immediately adjacent to the site is not used for agriculture, and it is unlikely that the site will affect agriculture in the area (10).
Natural Resources Use
The primary source of groundwater in the vicinity of the Sherwood Medical site is the unconfined alluvial aquifer; the bedrock Niobrara Chalk Formation is a secondary source. The alluvial is composed of unconsolidated, inter-mixed alluvial sand and gravel deposits that near the site vary in thickness from approximately 58 feet to 69 feet. The water table at the site is at depths ranging from 5 to 15 feet below ground surface. The saturated thickness of the aquifer averages about 50 feet. In general, there are no continuous confining layers or aquitards in the alluvial deposits or at the bedrock boundary (2).
Groundwater in the alluvial aquifer flows northeast from the site area to the Elkhorn River, where it discharges as baseflow. The flow is predominately horizontal and has a horizontal hydraulic gradient of approximately 0.005 feet per foot. For the majority of the site, the vertical groundwater flow direction is downward and uniform throughout the saturated thickness of the alluvial aquifer. This vertical hydraulic gradient averages approximately 0.0036 feet per foot and is the result of regional flow that primarily occurs at the base of the alluvial aquifer system (2). In the northeastern portion of the site, however, the vertical flow direction is upward because of the natural discharge to Medelmans Lake and to the Elkhorn River (9).
The Niobrara Formation is made up of calcareous shale and shaly chalk and lies directly under the alluvial deposits. The bedrock surface at the site is at depths between 58 and 69 feet below ground surface. Groundwater flow in the bedrock aquifer is also to the northeast (1,2).
Core samples have shown that the upper several feet of the bedrock are relatively unfractured. However, saturated zones of intensely fractured bedrock were commonly found below the upper, unfractured sections. Bedrock pump tests on the site have shown that the fractured portion of the Niobrara Formation is hydraulically connected to the overlying alluvial aquifer (2).
As previously discussed, multiple private supply wells are near the Sherwood Medical site. Most of the wells are screened in the alluvial aquifer at a typical depth of 55 to 60 feet, including the four Sherwood Medical plant wells, the two Park Mobile Home Court wells, several industrial and commercial wells, and a number of private residential wells (Figures 2 and 3). More specifically, approximately 45 residential wells are within 1/2 mile of the plant and about 100 are within 1 mile. Most of these wells are believed to be upgradient of the site (3).
A few private supply wells, including the residential well north of the plant on Highway 81 and the Karl Stefan Airport main well, are screened in the Niobrara Formation. In general, because adequate supplies are available in the alluvial sands and gravel, the Niobrara Formation is not extensively used (3).
Another category of supply wells in the Norfolk area includes those used for crop irrigation. Approximately 15 registered irrigation wells are south of the Elkhorn River within 3 miles of the Sherwood Medical site. As previously discussed, those wells are used primarily to irrigate corn grown for livestock feed. Irrigation wells in the region are commonly between 50 and 150 feet deep (3,5).
The city of Norfolk obtains drinking water from two well fields. The first, which is approximately 2.8 miles north-northeast of the Park Mobile Home Court within the city limits, has 5 wells and a capacity of 4.5 million gallons per day. The average depth of the wells is 120 feet; 50 to 60 feet penetrate the Niobrara Formation. The second well field is about 3.5 miles northwest of the Park Mobile Home Court and 2 miles west of the city limits. That field consists of six wells along the Elkhorn River, with a capacity of 5 to 7 million gallons per day. Well depths average 60 feet into the alluvial sand and gravel aquifer (5).
The Norfolk public water system has approximately 7,500 service connections. The southernmost extension of the system is to Monroe Street and U.S. Highway 81 (1.25 miles north of Park Mobile Home Court). All businesses and residences south of the Elkhorn River obtain water for drinking and other household uses from private wells. There are no rural water districts within 3 miles of the mobile home park south of the Elkhorn River (5).
Sherwood Lake occupies a topographical low in the eastern part of the Sherwood Medical property (see Figure 3). Before the site was developed, there is evidence that the Sherwood Lake area existed as a surface expression of the water table and a point of groundwater discharge. Currently, the water level in Sherwood Lake is maintained primarily by input of treated process water and stormwater runoff water from the Sherwood Medical plant. The lake currently serves as a recharge area for groundwater (10). This shallow surface water is not known to be used for recreation (e.g., swimming or fishing). However, children from the residences along Sherwood Road and from the mobile homes in the Park Mobile Home Court could wade and swim in the lake or play along its edge.
A larger lake, Medelmans Lake, is north of the Park Mobile Home Court (Figure 2). The lake was formed as a result of a sand and gravel operation that is still active. The sand and gravel operation is on the southern shoreline and currently pumps water from the southern part of the lake. Members of the Norfolk Boat Club are reported to use some parts of the lake for boating, water skiing, and swimming. Club members may also eat fish caught from the lake. On the basis of information from previous site investigations, Medelmans Lake is considered a discharge area for groundwater (10,11).
The Elkhorn River is just north of Medelmans Lake, approximately 1 mile north of the site (see Figures 1 and 2). The river is about 3.5 feet deep at its deepest point and does not entirely transect the alluvial aquifer. Although groundwater is reported to discharge to the river, it is uncertain whether the river actually represents a hydraulic barrier (2,3,7). It is not known whether the river, in the vicinity of the site, is used for recreational activities such as swimming, boating, or fishing.
Health outcome data were not evaluated during preparation of this public health assessment because available databases were not appropriate for the exposed community. The Health Outcome Data Evaluation subsection of the Public Health Implications section discusses in detail why such an evaluation was not performed.
County health officials, regional and state water quality staff, and city officials were not aware of any health-related concerns or inquiries associated with the Sherwood Medical site. They did report receiving complaints from residents of the Park Mobile Home Court regarding tastes and odors in their drinking water before the trailer park well was shut down.
ATSDR conducted two public availability meetings at the Norfolk City Library on January 16, 1992; a total of 6 people attended. The following health concerns were reported:
- An employee of the Sherwood Medical plant reported exposure (6-7 years previously) to high levels of trichloroethylene and ozone by way of inhalation and skin contact. The employee noted current symptoms of fatigue, muscular pain, and headaches. Concern also was expressed that there seemed to be a high rate of cancer, dating back to 1979 or earlier, among Sherwood Medical employees.
- A Norfolk resident expressed concern about high rates of cancer (specifically, breast and testicular cancer) among former and current Sherwood Medical workers.
Note: Sherwood Medical officials have indicated that trichloroethylene (TCE) was never used at their plant so no employees were ever exposed to TCE while working there. It is possible that the employee who reported exposures to TCE was actually referring to trichloroethane (1,1,1-TCA) since 1,1,1-TCA was used at the plant in the past.
These community health concerns are addressed in the Public Health Implications section of this public health assessment.