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PUBLIC HEALTH ASSESSMENT

LOCKWOOD SOLVENT GROUNDWATER PLUME
(a/k/a LOCKWOOD SOLVENT GROUND WATER PLUME)
BILLINGS, YELLOWSTONE COUNTY, MONTANA


SUMMARY

The Lockwood Solvents Site is a chlorinated solvent groundwater plume comprised mostly oftetrachloroethene (PCE), trichloroethene (TCE), cis-1,2-dichloroethene (cis-1,2-DCE), and vinylchloride. Sampling data show that volatile organic compounds (VOCs) have entered privatewells at levels above federal and state drinking water standards. People in the area used theirprivate wells for domestic purposes, including showering and bathing.

In the recent past, the Lockwood Solvent Groundwater Plume Site was a public health threat.Some residents were exposed to certain volatile organic compounds (VOCs) that might havecaused harmful effects. While bathing or showering a few residents were exposed totetrachloroethene (PCE). That exposure might have damaged the nervous system. Specifically,past exposure to PCE during bathing or showering might have caused mild changes in eye-handcoordination, changes in the ability to respond as quickly as normal to repeated stimuli, andchanges in the eye's perception of stimuli. These effects might have occurred during PCEexposure, but they are not expected in residents whose exposure ceased by switching to amunicipal water supply. Moreover, residents who showered with water from wells with highPCE levels might have an increased risk of cancer from PCE exposure. This conclusion is,however, uncertain because of limitations in determining the risk of cancer for PCE. In additionto PCE, a few residents were also exposed to vinyl chloride--that might have increased their riskof cancer. These conclusions are based on VOC levels in private wells sampled in 1998 and1999. VOC levels in prior years might have been higher or lower.

Currently, most adults report that they and their children never drank the water from their privatewells. Still, they were exposed to VOCs in groundwater while bathing or showering. Suchcontact with VOC-contaminated water resulted in inhalation exposures as the VOCs evaporatedfrom the water. In addition, bathing and showering exposed residents to VOCs by absorptionthrough the skin. Some adults and children also might have been exposed to VOCs via a soil-gaspathway.

To date, all of the affected homes either receive water from the municipal water supply or areserved by wells in which any contamination is below drinking water standards. These adults andchildren are no longer exposed to contaminants from household use of well water. The soil gaspathway and outdoor use of contaminated private wells remain potential exposure pathways forresidents whose homes are connected to the public water supply. The Montana Department ofEnvironmental Quality (MDEQ) continues to provide bottled water to residents whose privatewells contain contaminant levels below, but approaching, a Maximum Contaminant Level(MCL). MDEQ has confirmed that all businesses in the Lockwood Solvents Groundwater PlumeSite with private wells containing contaminant levels exceeding an MCL provide their employeeswith bottled water. In addition to these measures, steps have been taken to improve the indoor airquality of two homes located over the highest levels of groundwater contamination.

The source and extent of that groundwater contamination has not been determined. Samplingdata indicate that contaminant levels are approaching MCLs in several private wells in the sitearea. Additionally, off-site wells could become contaminated as the plume migrates; therefore,monitoring of the contaminant plume is necessary to prevent future exposures to adults andchildren.

ATSDR recommends the following for the Lockwood Solvents Groundwater Plume Site:

  1. If private wells exceed state or federal guidelines, implement procedures to stop exposureto contaminants in groundwater.
  2. Define the extent of the contaminant plume to determine whether other private wells inproximity to the plume have been impacted, or could in the future be impacted.
  3. Continue to monitor indoor air concentrations at selected residences, particularly ifconditions at the site change and during cold weather to confirm that indoor air levels ofVOCs are safe. Consider testing indoor air at commercial establishments for selectedVOCs if significant groundwater contamination is found beneath the facility.
  4. Continue to monitor contaminant levels in private wells of area residences andcommercial businesses that are not connected to the public water supply.
  5. With the affected community and local health officials, develop and implement a healtheducation plan to meet information and skill-development needs regarding localenvironmental health issues.
  6. Encourage residents to contact their personal physicians if their wells were highlycontaminated with VOCs. Residents can provide their physicians a summary of thisreport and then the resident and the personal physician can then decide what medicalmonitoring is appropriate.

In addition to these recommendations, ATSDR plans to conduct health education to informresidents of the contents and conclusions of this public health assessment. Agencyrepresentatives will talk with residents to obtain input on developing an education plan thatmeets the residents' needs. This plan will involve working with residents to develop healtheducation materials that answer their questions about the Lockwood Solvents Site. The plan willinclude items such as when and where residents want to meet, how to present information, whoshould present information, and follow-up activities.

A copy of a previous version of this document was available for public comment from February 8, 2002 until May 13, 2002. Comments received from the public are addressed inAppendix J.


PURPOSE AND PUBLIC HEALTH ISSUES

Purpose

In this public health assessment, the Agency for Toxic Substances and Disease Registry(ATSDR) evaluates a community's exposure to contaminants at hazardous wastes sites. ATSDRworks with local, state, and federal agencies as well as affected communities to identifynecessary public health measures This process can involve some or all of the following:

  • assessing how people might be exposed to contaminants,
  • evaluating the possible health effects that can result from exposure to contaminants, then determining appropriate public health actions to control those effects,
  • recommending medical tests, health education, and health promotion activities,
  • making recommendations to local, state, and federal agencies, and
  • finding ways to involve the community in health promotion.

This public health assessment describes ATSDR's activities at the Lockwood SolventsGroundwater Plume Site in Billings, Montana (referred to hereafter as the "Lockwood SolventsSite" or "the site"), and conclusions about the public health impact of contamination at that site.

Public Health Issues

This public health assessment describes ATSDR's activities at the Lockwood SolventsGroundwater Plume Site, and provides the Agency's opinion about the public health impact ofcontamination at the site. This public health assessment investigates whether exposure tochemicals in groundwater cause harmful effects in people, either in the past, present, or future.


BACKGROUND

Site Description

The Lockwood Solvents Site is located within the unincorporated community of Lockwood,adjacent to the northeastern outskirts of Billings, Yellowstone County, Montana. The site is achlorinated solvent groundwater plume comprised mostly of tetrachloroethene (PCE),trichloroethene (TCE), cis-1,2-dichloroethene (cis-1,2-DCE), and vinyl chloride. The source(s)and extent of the groundwater contamination will be determined during the remedialinvestigation.

The site is within the Yellowstone River Basin. That part of the community adjacent to theYellowstone River is within the 100-year flood plain. The Yellowstone River flows in anortheasterly direction, and forms the northern and western boundaries of the site (HRS- 2000).Rosebud Lane and Klenck Lane form the southern and eastern boundaries, respectively(Appendix A, Figure 1). These boundaries are approximate. The Remedial Investigation, whichis currently underway, will further define the site boundaries.

For household uses such as showering, bathing, and washing, residents in the area rely on privatewell water. Sampling data reveal that volatile organic compounds (VOCs) have entered privatewells along Bonnie Lane, Cerise Road, Doon Avenue, Island Park Road, Klenck Lane, LomondLane, Sandy Lane, and Taylor Place. Data indicate the highest concentrations of VOCs ingroundwater are in the Lomond Lane area. The Lomond Lane area is defined as the area north ofTaylor Road, west of Klenck Lane, south of the Yellowstone River, and east of Sandy Lane(Appendix A, Figure 2).

The Lockwood Solvents Site comprises residential, commercial, and light industrial properties.Several commercial and industrial facilities are within or near the site boundaries. They includeseveral large and small quantity generators of hazardous waste. Several commercialestablishments are known to store, use or manufacture chlorinated solvents (Pioneer- 1998a).

The Lockwood Water Treatment Plant, operated by the Lockwood Water and Sewer District(LWSD) is at 736 Cerise Road. The LWSD is a local supplier of public drinking water to aportion of the Lockwood community. The LWSD supplies public drinking water from theYellowstone River, which has not been shown to be affected by the groundwater contamination.

According to 2000 U.S. Census data, a total of 1,931 persons live within 1 mile of the site.Ethnic groups within the 1 mile radius include 1,803 Caucasians; 83 Hispanics; 31AmericanIndians and Alaska Natives alone; 8 African Americans; 10 Asian or Pacific Islanders; and 18identified as other ethnic groups. Included in these numbers are 193 children aged 6 and younger,and 222 adults aged 65 and older (Appendix A, Figure 3).

Site History

Contamination was discovered in Lockwood in 1986 during an investigation of a Cenex pipelinerupture. During the 1986 investigation, the LWSD found their public water supply wells werecontaminated with chlorinated solvents at levels below the Maximum Contaminant Level(MCL). An MCL is a regulatory limit set by the Environmental Protection Agency (EPA) whichspecifies the maximum permissible level of a contaminant in water that is deliverable to the userof a public water system.

Beginning in 1991, the Montana Department of Environmental Quality (MDEQ) initiated a seriesof investigations to determine the source of LWSD well contamination. Other independentinvestigations were also conducted in the vicinity of the LWSD wells. Benzene, toluene, xylene,and ethylbenzene (components of gasoline) and chlorinated solvents, such as TCE and cis-1,2-DCE, were found in the groundwater in the vicinity of the LWSD wells and up to one-half mileeast of the LWSD wells (HRS 2000). The results of these investigations was that the widespreadsolvent contamination was attributable to the combined solvent releases from the major industrialand commercial facilities in the area (Pioneer 1998a).

In 1993, the Water Quality Bureau of the Montana Department of Health and EnvironmentalServices collected water samples from three private residential wells along Cerise Road andIsland Park Road. The Bureau wanted to determine whether contamination had spread from theCenex pipeline leak or other known contaminant sources to downgradient private wells. TheBureau found the private wells were contaminated with solvents, but at levels below state and federal drinking water standards (Pioneer 1998a).

Past ATSDR Reports

ATSDR has issued two previous health consultations for the Lockwood Solvents Site. The first,released on December 9, 1999, dealt with public health concerns about (1) bathing in watercontaminated with VOCs and (2) VOCs migrating into houses from soil. This consultationconcluded that VOCs in private wells were a public health concern (see Appendix D). ATSDRreleased the second health consultation on May 3, 2000. This consultation evaluated indoor air measurements of VOCs in two homes, concluding that contamination levels were not a public health concern (see Appendix E).

Site Visits

ATSDR staff visited the Lockwood Solvents Site from January 16 through 18, 2001. ATSDRrepresentatives met with staff from the MDEQ and Yellowstone County Health Department.ATSDR visited local residents in their homes, as well as owners and workers in their place ofbusiness, to document health concerns and to obtain specific information about well water usagein the area. We drove through the site area, observing the distribution of residences andbusinesses around the site. Coulson Ditch, a free-flowing body of water, appeared to containbetween 1 to 2 feet of standing water where it transected Lomond Lane. Also, several homeswere observed between Lockwood Road and Rosebud Lane that were not previously included inany of the site maps. ATSDR is investigating to determine the source of potable water for thesehomes and whether these homes are potentially within the area of groundwater contamination.

ATSDR learned through interviews with current residents that most residents did not use theirwell water for drinking or cooking purposes. Unappealing taste and appearance were the reasonsmost residents gave for not using the water. Others cited knowledge of past contamination in thearea as a reason for not using the water. For similar reasons, many business owners in the areasupply bottled water to their employees for drinking. ATSDR did not obtain well water usagereports from residents who may have lived in the area in the past and have since relocated.Therefore, our conclusions regarding water usage are based upon reported usage by currentresidents only.

At a January 18, 2001 public availability session, ATSDR invited local residents and businessowners to speak with staff individually. Representatives from the local media, EPA and MDEQwere also present. Approximately 40 persons attended and spoke with ATSDR staff membersabout their health concerns from exposure to contaminants in their private wells. Residents alsodescribed their health concerns in letters mailed to ATSDR after the session. A recurring issue inboth personal interviews and letters was concern over subsurface vapors entering homes andcontaminating indoor air. Residents asked that the indoor air in their homes be tested on a regularbasis and the test results explained to them in clear, understandable language. Informationobtained during the site visit and in letters from residents is discussed in pertinent sections of thisassessment. The Community Health Concerns section, which appears later in this assessment,addresses residents' health-related concerns.

On March 13 and 14, 2002, ATSDR held two additional public availability sessions in thecommunity. The purpose of the sessions was to discuss with and answer questions from residentsabout the conclusions in the initial public health assessment, and to address additional healthconcerns from residents. ATSDR also began implementing health education activities for thecommunity in the form of health education materials and referrals, as appropriate. Approximately 10 people attended both sessions.


ENVIRONMENTAL CONTAMINATION

A review of environmental contamination at the site is an integral element of a public healthassessment. In the following sections, the results of environmental sampling conducted byMDEQ or EPA at the Lockwood Solvents Site are discussed for each media (i.e., groundwater,surface water, sediment, soil, and air).

In the following sections, concentrations of chemicals in each of the media are compared toappropriate comparison values to select chemicals for further evaluation. A contaminant found toexceed a comparison value indicates that a more detailed analysis is necessary for that chemical.The comparison values are used only to screen for chemicals that require further evaluation.Levels of contamination greater than these values do not necessarily mean that adverse healtheffects will occur. The amount of the chemical, the duration of exposure, the route of exposure,and the health status of exposed individuals are also important factors in determining thepotential for adverse health effects.

If its concentration in some medium exceeded one of the comparison values, that chemical wasretained as a contaminant of concern and is listed in Tables 1 through 3 in Appendix B. It shouldbe noted, however, that no chemicals exceeding a comparison value were detected in sediment orsoil samples. The major chemicals of concern are four chlorinated solvents: PCE, TCE, cis-1,2-DCE, and vinyl chloride. The maximum concentration of these four chemicals was listedwhenever detected in each medium, even if the maximum concentration did not exceed acomparison value for that medium.

Groundwater (includes private wells)

Maximum Contaminant Level (MCL): An MCL is the regulatory limit set by the EPA which establishes the maximum permissible level of a contaminant in water that is deliverable to the user of a public water system. If an MCL is exceeded, regulatory action must be taken to mitigate exposures to the users of the water supply.Beginning in1998, the MDEQ began a series of investigations to determine the extent ofgroundwater contamination in the Lockwood area and to identify the source or sources of thecontamination. In June 1998, the MDEQ conducted a site investigation under the ComprehensiveEnvironmental Response, Compensation and Liability Act (CERCLA) integrated assessmentprocess. The investigation included sampling 14private wells potentially within the suspected area ofcontamination. In addition, groundwater sampleswere collected from seven potential source areas (viaa Geoprobe® sampling device), three existinggroundwater monitoring wells, and two LWSD publicwells.

Nine residential wells, mainly in the Lomond Lanearea, and several groundwater samples had levels of contamination which exceeded MaximumContaminant Levels (MCLs). The primary contaminants of concern, PCE, TCE, cis-1,2-DCE,and vinyl chloride, were detected in private wells and in groundwater at concentrations whichexceeded MCLs. Carbon tetrachloride was detected in a groundwater sample at 9 ppb, whichexceeds the MCL of 5 ppb for the compound. The maximum concentration detected for themajor contaminants and the applicable MCLs are listed in Table A below.

Table A.

Major Contaminants of Concern Detected in Private Wells and Groundwater, June 1998
Contaminant Maximum Contaminant Level (MCL) (ppb) Maximum Concentration Detected in Private Wells1 (ppb) Maximum Concentration Detected in Groundwater (ppb)
tetrachloroethene (PCE) 5 1,900 2
trichloroethene (TCE) 5 150 3,770
cis-1,2-dichloroethene (DCE) 70 590 15,200
vinyl chloride 2 190 6

1Private well results are reported for laboratory-analyzed samples only.

In September 1998, MDEQ collected samples from nine additional residential and commercialwells in the area. VOCs were detected in all samples except for one residential well sample. Tworesidential wells contained levels of PCE, TCE, cis-1,2-DCE, and vinyl chloride which exceededapplicable MCLs. Carbon tetrachloride was detected in a commercial well at 12 ppb, whichexceeds the MCL of 5 ppb for the compound. The maximum concentration detected (inSeptember 1998) for the major contaminants and the applicable MCLs are listed in Table Bbelow.

Table B.

Major Contaminants of Concern Detected in Private Wells and Groundwater, September 1998
Contaminant Maximum Contaminant Level (MCL) (ppb) Maximum Concentration Detected in Private Wells1 (ppb) Maximum Concentration Detected in Groundwater (ppb)
tetrachloroethene (PCE) 5 319 507
trichloroethene (TCE) 5 81 109
cis-1,2-dichloroethene (DCE) 70 217 405
vinyl chloride 2 9 38

1Private well results are reported for laboratory-analyzed samples only.

In January and March 1999, MDEQ conducted an investigation to identify the source or sourcesof VOC contamination and to sample (or resample) all existing residential or commercial wellsthat were potentially within the vicinity of the groundwater plume. Seven wastewater disposalsystem samples, twelve groundwater samples, ten commercial well samples, and six residentialwell samples were collected as part of the investigation. The wastewater disposal systems at areabusinesses did not contain chlorinated solvents and were eliminated as a potential source ofcontamination (Pioneer 1999c). However, concentrations of VOCs in private wells andgroundwater continued to exceed federal MCLs. The maximum concentration detected for themajor contaminants of concern and the applicable MCLs are listed in Table C below.

Table C.

Major Contaminants of Concern Detected in Private Wells and Groundwater, January/March 1999
Contaminant Maximum Contaminant Level (MCL) (ppb) Maximum Concentration Detected in Private Wells1 (ppb) Maximum Concentration Detected in Groundwater (ppb)
tetrachloroethene (PCE) 5 395 40
trichloroethene (TCE) 5 82 9.1
cis-1,2-dichloroethene (DCE) 70 184 7.5
vinyl chloride 2 11 Not detected

1Private well results are reported for laboratory-analyzed samples only.

In May of 1999, MDEQ submitted a request for the EPA to investigate groundwatercontamination specifically in the Lomond Lane area. Between September and October 1999,EPA sampled 27 private wells, collected 48 groundwater samples from 37 locations, andinstalled and sampled 11 groundwater monitoring wells (HRS 2000). EPA found elevatedconcentrations of VOCs in both groundwater and private wells in the area. The maximumconcentration detected for the major contaminants and the applicable MCLs are listed in Table D below.

Table D

Major Contaminants of Concern Detected in Private Wells and Groundwater, September/October 1999
Contaminant Maximum Contaminant Level (MCL) (ppb) Maximum Concentration Detected in Private Wells1 (ppb) Maximum Concentration Detected in Groundwater (ppb)
tetrachloroethene (PCE) 5 1,500 4,200
trichloroethene (TCE) 5 140 350
cis-1,2-dichloroethene (DCE) 70 390 1,300
vinyl chloride 2 87 330

1Private well results are reported for laboratory-analyzed samples only.

Indoor Air

Indoor air sampling has been conducted at selected residences in the Lomond Lane areabeginning in September 1999 until February 2002. Indoor air samples were collected by EPA,MDEQ, or a private contractor (Pioneer) on behalf of MDEQ.

In September 1999, EPA collected air samples from the crawl spaces and living areas of two homes on Lomond Lane (URS 2000). The two homes were selected for indoor air sampling because of their location above the highest concentrations of VOCs in groundwater (Tetra Tech 2002). Of the four major site contaminants, PCE was detected up to a maximum concentration of 5.3 parts per billion (ppb)(1), or 36.3 µg/m3; and TCE was detected up to a maximum concentration of 2.36 ppb, or 6.1 µg/m3, in the crawl spaces of the two homes. Cis-1,2-DCE and vinyl chloride were either not detected or not analyzed for in these samples. The maximum concentrations of PCE and TCE are below ATSDR's air comparison values of 40 ppb (276 µg/m3) and 100 ppb (546 µg/m3), respectively, for the compounds.

In January 2000, EPA collected additional indoor air samples from the two previously-sampled residences to evaluate wintertime air concentrations. The highest concentrations of PCE (19.8 ppb or 136.3 µg/m3) and TCE (14.0 ppb or 76.2 µg/m3 ) were detected in the indoor living area of one of the homes. Again, cis-1,2-DCE and vinyl chloride were either not detected or not analyzed for in these samples. The concentrations of PCE and TCE were higher in indoor air in January than in September, but the concentrations did not exceed applicable comparison values for the compounds. Other VOC compounds, including methylene chloride, chloroform, benzene, and bromodichloromethane, were detected at concentrations which exceeded applicable comparison values (See Table 3, Appendix 2).

In March, April, and June 2000, EPA collected additional air samples from the crawl spaces and living spaces of the previously-sampled two homes and several other homes in the Lomond Lane area. Maximum concentrations of PCE (5.4 ppb or 37 µg/m3), TCE (2.2 ppb or 12 µg/m3), and cis-1,2-DCE (4.7 ppb or 19 µg/m3) were detected at levels below their applicable air comparison values. Vinyl chloride was detected up to a maximum concentration of 0.62 ppb (1.6 µg/m3) in the living area of one residence. This concentration of vinyl chloride exceeds ATSDR's comparison value of 0.04 ppb (0.1 µg/m3) for the compound. Several other VOCs, including carbon tetrachloride, 1,1-dichloroethene, and 1,2-dichloroethane were detected at concentrations which exceeded their applicable comparison value (See Table 3, Appendix 2).

Beginning in April 2001, indoor air monitoring in the Lomond Lane area was conducted in accordance with an approved Sampling and Analysis Plan (Preliminary Residential Air Sampling). Sampling locations were selected based on whether 1) the location was an occupied residence, and 2) the location was above underlying groundwater contaminant concentrations in excess of the EPA MCL (Tetra Tech 2002). The first round of sampling under the new plan was conducted in April/May 2001 by MDEQ. A total of 18 samples were collected during the April/May 2001 sampling event. The maximum concentrations of the major site-related contaminants were 17.7 ppb (122 µg/m3) for PCE and 5.8 ppb (31.7 µg/m3) for TCE in the crawl space area of a home. Maximum concentrations of cis-1,2-DCE up to 1.8 ppb or 7.1 µg/m3, and vinyl chloride up to 0.01 ppb or 0.03 µg/m3 were detected in the indoor living space of a home. None of the major site-related contaminant concentrations exceeded comparison values during the April/May 2001 sampling. Carbon tetrachloride (up to 0.1 ppb or 0.63 µg/m3) and 1,2-dichloroethane (up to 0.04 ppb or 0.17 µg/m3) were detected in the living space at concentrations which exceeded the comparison values of 0.07 µg/m3 and 0.04 µg/m3, respectively, for the compounds.

In July 2001, additional indoor air sampling was conducted by MDEQ. A total of 5 samples were collected from the crawl space and living space of three residences. The four major contaminants were detected at concentrations up to 16.7 ppb (115 µg/m3) for PCE, 5.8 ppb (31.6 µg/m3) for TCE, and 7.8 ppb (4.7 µg/m3) for cis-1,2-DCE in the crawl space of one home; vinyl chloride was detected at a maximum concentration of 0.01 ppb (0.03 µg/m3) in a sample from the indoor living space of a residence. None of the major contaminant concentrations exceeded comparison values during the July 2001 sampling. Carbon tetrachloride (up to 0.08 ppb or 0.52 µg/m3) was detected in the living space and 1,2-dichloroethane (up to 0.18 ppb or 0.73 µg/m3) was detected in the crawl space at concentrations which exceeded the comparison values of 0.07 µg/m3 and 0.04 µg/m3, respectively, for the compounds.

Pioneer was contracted by MDEQ to conduct additional indoor monitoring at 15 residences in October 2001. Crawl space samples were not collected during this and subsequent sampling events because air levels from a crawl space cannot be used to determine if air levels in living spaces are unsafe. Confounding factors and other potential point source contributors could not be ruled out from crawl space samples (Tetra Tech 2002). Therefore, only samples from the living spaces of homes were collected and are considered indicative of actual breathing zone concentrations to which residents are exposed. The results of the October 2001 sampling revealed concentrations of PCE up to 5.5 ppb (37.9 µg/m3), TCE up to 3.1 ppb (16.7 µg/m3); cis-1,2-DCE up to 1.7 ppb (6.7 µg/m3), and vinyl chloride up to 0.02 ppb (0.05 µg/m3). None of the major site-related contaminant concentrations exceeded comparison values during the October 2001 sampling. Carbon tetrachloride (up to 0.12 ppb or 0.75 µg/m3) and 1,2-dichloroethane (up to 0.12 ppb or 0.49 µg/m3) continued to exceed the comparison values of 0.07 µg/m3 and 0.04 µg/m3, respectively, for the compounds.

In February 2002, Pioneer collected 16 additional indoor air samples from 14 residences in the Lomond Lane area. PCE was detected in indoor air at concentrations up to 5.7 ppb (39.5 µg/m3), TCE, up to 1.08 ppb (5.9 µg/m3) and DCE, up to 9.8 ppb (6.3 µg/m3). Vinyl chloride was not detected in any of the samples. None of the four major site contaminants was detected at concentrations which exceeded comparison values during the February 2002 sampling event. Carbon tetrachloride (up to 0.08 ppb or 0.51 µg/m3 ) and 1,2-dichloroethane (up to 0.06 ppb or 0.24 µg/m3) exceeded the comparison values of 0.07 µg/m3 and 0.04 µg/m3, respectively, for the compounds.

Table E below gives the maximum detected concentration of all indoor air sampling resultsbetween September 1999 and February 2002 for the contaminants of concern. Only samplescollected from indoor living areas are included in the chart. It should be noted that of the fourmajor contaminants (PCE, TCE, cis1,2-DCE, and vinyl chloride), only vinyl chloride exceededits comparison value in one sample.

Table E.

Maximum Indoor Air Concentrations for Major Site-Related Contaminants of Concern
Contaminant Maximum Concentration Detected ( in ppb) Comparison Value in ppb Maximum Concentration Detected (in µg/m3) Comparison Value in µg/m3
tetrachloroethene (PCE) 19.8 40 136.3 276
trichloroethene (TCE) 14.0 100 76.2 546
cis-1,2-dichloroethene (DCE) 4.7 9.2* 19 37*
vinyl chloride 0.62 0.04 1.6 0.1

* represents EPA Risk-based Concentration (RBC)

It is important to consider the presence of background concentrations of chemicals in U.S. homeswhen evaluating the concentration of chemicals found in the air in homes at the LockwoodSolvents Site. By background concentrations, ATSDR means that low levels of VOCs are usuallyfound in most homes. These low concentrations may come from off-gassing of buildingmaterials, from outdoor sources permeating into the home, or from human activities in the home.Human activities, such as smoking, crafts, or hobbies can contribute to increased indoor airconcentrations of some chemicals. In addition, the use and storage of consumer householdproducts (e.g., cleaners, paints, and glues) and the use of heating fuels in the home can provideadditional indoor vapor emission sources (Wallace 1987). Another source of indoor chemicals inair is parking a car in an attached garage. The vapors escaping from gasoline will increase levelsof benzene and other chemicals in indoor air. ATSDR considered these factors when evaluatingthe indoor air data from the Lomond Lane area. Even though a chemical might normally befound in indoor air due to human activities, it will still be evaluated in the Public HealthImplications section of this document if it exceeds a comparison value.

Soil (including soil vapor)

In June 1998, MDEQ collected soil and soil vapor samples at selected locations. Nocontaminants were detected in the soil vapor samples. Five VOCs were detected in soil samples:chloromethane, cis-1,2-DCE, TCE, PCE, and naphthalene. However, no samples exceededapplicable soil comparison values. In January and March 1999, soil samples were collected inthree areas using a Geoprobe sampling device. PCE was detected in two of the three soil samplesup to a maximum concentration of 2.3 ppm, which is below the comparison value of 12 ppm forPCE in soil. Soil vapor sampling was attempted at two locations. The high clay content and smallpore size of the soil did not allow for collection of soil vapor samples and the sampling wasabandoned (Pioneer 1999a).

Surface Water/Sediment

In January through March 1999, MDEQ collected three surface water and sediment samples fromCoulson Ditch. Coulson Ditch is a body of free-flowing water traversing the southern portion ofthe site from west to east. Coulson Ditch has been identified as a potential source of contaminanttransport to the Lomond Lane Area from an upstream source. The sampling results revealed thatCoulson Ditch contained only very low levels of TCE and DCE. Sediment samples contained nodetectable VOC compounds. In September 1999, EPA collected three additional surface watersamples from Coulson's Ditch. No detectable levels of any VOC compounds were evident in thesurface water samples.

The Lockwood Solvents Site was proposed to the National Priorities List (NPL) on May 11,2000. The site was placed on the NPL on December 1, 2000. The NPL is the EPA's list of themost serious hazardous waste sites throughout the United States. NPL sites are given the highest priority for cleanup under the federal Superfund program.


DISCUSSION OF EXPOSURE PATHWAYS

ATSDR's pathways analysis determines whether people have come into contact withcontaminants from a site and whether those contacts were substantial enough to cause harm. Tomake this determination, ATSDR identifies exposure pathways or ways in which a chemicalcould enter a person's body (e.g., ingestion, inhalation, or dermal (skin) contact). An exposure pathway contains five major elements:

  1. a source of contamination,
  2. transport through an environmental medium,
  3. a point of exposure,
  4. a route of exposure, and
  5. an exposed population.

If an exposure pathway contains all five elements and exists now or existed in the past, thepathway is considered complete. Completed exposure pathways are evaluated to determinewhether health effects could occur. If one or more of the five elements is not clearly defined butcould be present, the exposure pathway is classified as potential. Tables 4 and 5 list thecompleted and potential exposure pathways for the site.

Completed Exposure Pathways

Groundwater in Private Wells

The most significant completed exposure pathway for the site is the past use of contaminatedgroundwater by residents and workers. In the past, adults and children used the contaminatedgroundwater from their private wells for household purposes such as drinking, cooking, bathing,washing clothes, and filling toilets. Residents also used their private wells to water lawns and filloutdoor swimming pools. Workers in some businesses in the area have previously used wellwater and continue today to use well water for job-related purposes (e.g., spray-washing trucks,cleaning equipment, mixing products, etc.) or washing their hands. The primary exposure routesfor children, adults, and workers are ingestion, dermal contact, and inhalation.

Either MDEQ or EPA have sampled most of the known private wells on or near the LockwoodSolvents Site. From June 1998 to November 2000, these agencies collected approximately 100samples from 34 private wells. The samples included 23 residential wells, one irrigation well,and 10 commercial wells. Analytical data indicate that many wells are contaminated with VOCs,primarily PCE, TCE, cis-1,2-DCE, and vinyl chloride. The highest levels of contamination werein the Lomond Lane Area. The maximum concentration detected of each contaminant and theapplicable comparison values are contained in Table 1 in Appendix B.

Thirteen (10 residential and 3 commercial) of the 34 sampled wells contained levels of PCE thatexceeded EPA's maximum contaminant level (MCL) of 5 ppb for PCE. Nine of these 13 wellscontained PCE levels above EPA's Removal Action Level (RAL) of 70 ppb for PCE. A RAL isthe contaminant level at which EPA will take immediate action to stop exposures to people froma source of contamination. The maximum concentration of PCE detected in a private well was1,900 ppb, which is 380 times greater than the MCL of 5 ppb and 27 times greater than the RALof 70 ppb. Twelve ( 9 residential and 3 commercial) of the 34 sampled wells contained levels ofTCE which exceeded EPA's MCL of 5 ppb for TCE. The maximum level of TCE detected in aprivate well was 150 ppb, which is 30 times greater than the MCL of 5 ppb for TCE. Seven (6residential and 1 commercial) of the 34 sampled wells contained levels of cis-1,2-DCE whichexceeded EPA's MCL of 70 ppb for cis-1,2-DCE. The maximum level of cis-1,2-DCE detectedin a private well was 590 ppb, which is 8 times greater than the MCL of 70 ppb for cis-1,2-DCE.Eight (7 residential and 1 commercial) of the 34 sampled wells contained levels of vinyl chloridewhich exceeded EPA's MCL of 2 ppb for vinyl chloride. The maximum concentration of vinylchloride detected in a private well was 190 ppb, which is 95 times greater than the MCL of 2 ppbfor vinyl chloride. Carbon tetrachloride was detected in one commercial well at a concentrationof 12 ppb, which exceeded the federal MCL of 5 ppb for the compound. Several other VOCcompounds were detected in private wells throughout the site at concentrations below MCLs(Table 1, Appendix B).

Groundwater in the shallow water table aquifer is contaminated with VOCs - primarily PCE,TCE, cis-1,2-DCE, and vinyl chloride. There is no way of knowing exactly when people wereinitially exposed to contaminants in groundwater. People could have been exposed for a long orrelatively short period of time, depending upon when the groundwater was contaminated and thelength of their residency within the site. Many of the major industries have operated in the areafor many decades. If groundwater was contaminated soon after potential source facilities beganoperating, ATSDR estimates that the maximum duration of exposure could be 15 to 25 years.

By telephone and face-to-face interviews, ATSDR obtained water usage reports from all currentresidents whose private wells had contamination levels above an MCL. ATSDR learned throughthese personal interviews that currently most adults and children never used their water fordrinking or cooking purposes. The few residents who did report drinking their well water did sofor only a short time (less than 1 year), or did not have contamination in their wells above afederal MCL. Some residents reported an unappealing taste or appearance of the water as reasonsfor not drinking their well water. Others reported concern over the quality of the water because ofknowledge of past contamination in the area. Also, for similar reasons, most businesses in thearea had for some time supplied their workers with bottled water for drinking purposes. ATSDRdid not contact residents who might have lived in the area in the past and have subsequentlymoved from the area. Past residents might have been exposed to contaminated drinking water formany years, depending upon their length of residency in the area and the time of the initialgroundwater contamination. ATSDR assumes that current and past residents might have beenexposed to contaminated groundwater for up to 20 years.

Actions Taken to Reduce Exposures via Private Wells

Currently, there are no known significant exposures to contaminants in private wells. Beginningin September 1998, MDEQ began supplying bottled water to residents whose private wells wereidentified as having contaminant levels approaching or exceeding an MCL. In July 1999, EPA'sRemoval Action Program continued providing bottled water to residents whose private wellcontained contamination exceeding an MCL. EPA's Removal Action Program also supplied bulkwater to those residents whose private well contained contamination exceeding an MCL. MDEQcontinues to provide bottled water to residents whose private wells have contaminant levelsapproaching an MCL. Currently, all of the affected homes identified to date either receive waterfrom the municipal water supply or are served by a private well that has not shown contamination above state or federal drinking water standards.

Indoor Air

People were likely exposed to VOCs in indoor air from two sources: vapors from domestic use ofwell water (showering, bathing, etc.) and subsurface vapor migration. VOCs in contaminatedgroundwater will volatilize from water when well water is used for showering, bathing, cooking,or other household purposes. The evaporating VOCs accumulate in the air of the bathroom orkitchen and are later dispersed throughout the house. Occupants then breathe in the contaminatedvapors. Vapors produced by using VOC-contaminated water contribute to the total concentrationof VOCs in the indoor air from other sources. In addition, VOCs in groundwater can evaporatefrom the groundwater into the spaces between soil particles (soil gas). The soil gas then diffusesthrough the soil, enters basements or homes through cracks in the walls or floors andcontaminates indoor air. Adults and children are exposed by inhaling chemicals in the indoor air.

The EPA collected air samples from the crawl spaces, living areas or both at several homesbetween September 1999 and February 2002. Of the four primary contaminants of concern- PCE,TCE, cis-1,2-DCE, and vinyl chloride- only vinyl chloride was detected in one sample at aconcentration which exceeded the comparison value for the compound. Other VOC compounds,notably carbon tetrachloride and 1,2-DCA, were detected above ATSDR comparison values inindoor air.

As previously stated, low levels of VOCs are found in most homes, having originated fromseveral possible sources: outdoor air, home building materials, use and storage of consumerhousehold products (cleaning, home care, refinishing, automotive and hobby products), and useof heating fuels in the home (EPA-2002). Because of these multiple sources, indoor air oftencontains VOCs, thus making it difficult to prove that indoor air contaminants are indeed comingfrom soil gas.

The presence of PCE and TCE at higher levels in some homes compared to other homes at theLockwood Solvents Site suggests that VOCs might be migrating into some homes from thegroundwater contaminant plume. There appears to be some correlation between high VOCcontamination in groundwater and higher VOC levels in indoor air. The homes over the highestlevels of groundwater contamination also had the highest indoor levels of PCE and TCE.Although the detected indoor air levels for the major contaminants of concern did not exceedcomparison values, the presence of these VOCs would still contribute to a person's overall VOCexposure if the person was also bathing in contaminated well water. It should be noted that it isnot certain if the contaminated groundwater is the source of the chemicals found in the indoor airin these homes. It is possible that other indoor sources contributed to the elevated levels of VOCsfound in some homes. It is uncertain at this time if vapors are entering homes via the soilmigration pathway, but exposures along this pathway were possible in the past and couldcontinue into the future until the groundwater is remediated.

Actions Taken to Reduce Exposures via Indoor Air

After the January 2000 air sampling, EPA took steps to improve the indoor air quality of twohomes on Lomond Lane. The groundwater under these two homes contained the highestconcentration of contaminants of any residence in the Lockwood Solvents Site. In addition, theindoor air samples taken from the living areas and crawl spaces of these two homes containedconcentrations of PCE which exceeded established screening levels. EPA performed vapormitigation at these two homes to reduce the migration and collection of VOCs in the indoor air atthese two homes. EPA installed vents in the crawl spaces, placed air intakes in the attics, andreplaced the duct work in the homes. Post-mitigation sampling indicated that PCE levels werereduced because of EPA's actions (Tetra Tech 2002).

Residences with private well contaminant levels above MCLs have been provided with publicwater for household uses. By providing an alternative water supply for these residents, exposureto vapors from household use of contaminated water has been eliminated.

Potential Exposure Pathways

Surface Water and Sediment

Groundwater from the site could discharge into water bodies in the area and carry site-relatedcontaminants into the surface water and sediments. People who swim, fish, or play in nearbystreams, ponds, springs, and drainage or irrigation ditches may be exposed intermittently toVOCs, primarily through incidental ingestion and dermal contact.

Surface water samples collected from Coulson Ditch in winter 1999 were found to contain lowlevels of VOC compounds. The levels detected were below drinking water standards and,therefore, are probably not harmful. The source of the VOCs in Coulson Ditch has not beendetermined. Surface water samples from fall 1999 found no detectable concentration of any VOCcompounds. No VOC compounds were detected in sediment samples from Coulson Ditch.Current data do not suggest that the VOC plume is affecting water quality in Coulson Ditch. Thepossibility of future contamination as the VOC plume migrates cannot be ruled out.

The generalized direction of groundwater flow in the area is north-northwest, toward theYellowstone River. Therefore, the Yellowstone River could be receiving contaminants from thedischarge of groundwater into the river. If site-related contaminants are reaching the YellowstoneRiver, the contaminant levels in the river would likely be very low because of dilution andvolatilization of VOCs from the river to the atmosphere.

High concentrations of VOCs have been detected in surface water at A-J Gravel Pond. Up to 661ppb PCE, 110 ppb TCE, 306 ppb cis-1,2-DCE, and 39 ppb vinyl chloride were detected in asurface water sample collected from the pond in September 1998. The A-J Gravel Pond is a 2.2-acre gravel pit located on Lomond Lane immediately adjacent to the Yellowstone River. The pitshares the northern sidewall with the Yellowstone River. Water is pumped from the pitapproximately three times per year in four to five week intervals to allow mining of the gravel.The water is pumped at a rate of approximately 300,000 gallons per hour and discharged into theadjacent Yellowstone River. The pond is then allowed to recharge via local groundwater andpossibly the Yellowstone River (Pioneer 1999).

According to MDEQ, people have been observed fishing in the A-J Gravel Pond in the past. It isuncertain whether the fish were eaten and whether fishing or other recreational activitiescurrently occur at the pond. Recreational users of the A-J Gravel Pond may be intermittentlyexposed to contaminants via incidental ingestion, inhalation, or dermal contact. Workers at thegravel pit could be exposed to VOCs via incidental ingestion, inhalation, or dermal contact asthey work in and around the pond. Workers or recreational users of the pond are unlikely to beexposed to contaminants via inhalation at levels of health concern because of rapid volatilizationand dilution of the compounds in ambient air. Occasional contact with or accidental ingestion ofwater from the pond is unlikely to result in adverse health effects. Sampling data are notavailable to confirm whether VOC compounds are retained in sediments; but, because of thevolatile nature of the contaminants, this exposure pathway appears unlikely to result insignificant exposures.

Groundwater (including private wells)

Because the plume of contaminated groundwater has not been fully defined, the possibility ofoff-site groundwater contamination cannot be ruled out. As the plume migrates, groundwatercontamination could spread to areas outside of the known areas of contamination. Private wellsto the northwest of the Lockwood Solvents Site could be threatened if the plume migrates underthe Yellowstone River.

The sampling data indicate that the contaminant levels in several residential wells areapproaching MCLs. The contaminant levels in these wells could increase (i.e., greater than MCL)as the plume migrates. The potential also exists for a resident or business owner to install a newwell in the contaminated groundwater plume and use the well for potable purposes. Furthermore,residents could chose to keep their private wells in service to use for watering their gardens,washing their cars, or other outdoor uses.

Soil

VOCs have been detected in soil samples taken from the Lockwood Solvents Site, but theconcentrations did not exceed applicable comparison values. If soils in and around the sourcearea contained high levels of VOCs in the past, outdoor workers at the facility could have beenexposed to contaminants in soil through incidental ingestion, dermal contact, or inhalation.Typically, VOCs in contaminated surface soil tend to volatilize rapidly in outdoor ambient air.Because information about past levels of VOC contamination in soil is not available, this pastpotential exposure pathway cannot be fully evaluated.

Results of soil sampling conducted at potential source areas show that the majority of soilcontamination is associated with deeper soils, likely due to the downward migration ofcontaminants to the subsurface over time. Workers who dig into the ground around areas ofcontamination could be exposed to VOCs in subsurface soils if they do not wear properprotective equipment. Residents should not be exposed to the chemicals of concern through thesoil medium if they do not dig into subsurface soils.

Biota

Adults and children who consume garden produce irrigated with contaminated groundwater arenot likely to be substantively exposed to the chemicals of concern because plants generally do notbioaccumulate VOCs. Further, plants are not likely to take up substantial amounts of VOCsthrough their roots. VOCs found in surface water in Coulson Ditch and A-J Gravel Pond mighthave reached the Yellowstone River and been taken up by fish. However, fish generally do notbioaccumulate VOCs found in surface water. Information about VOC levels in the YellowstoneRiver and about fish consumption from the Yellowstone River and A-J Gravel Pond are notavailable to fully evaluate this potential pathway.


1. A ppb means parts per billion and refers to the amount of chemical in a billion parts of air. For instance, 30 ppb PCE means 30 parts of PCE to every billion parts of air.




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