Assessment of Soil Gas Sampling Data
at the Millbrook Condominiums Site
EAST WINDSOR, HARTFORD COUNTY, CONNECTICUT
The conclusions and recommendations in this health consultation are based on the data and information made available to the Connecticut Department of Public Health and the Agency for Toxic Substances and Disease Registry. The Connecticut Department of Public Health and the Agency for Toxic Substances and Disease Registry will review additional information if and when received. The review of additional data could change the conclusions and recommendations listed in this document.
The U.S. Environmental Protection Agency (EPA) requested a review of soil gas sampling data for the Millbrook Condominium Site in East Windsor, Connecticut. The EPA provided environmental sampling data from this site . The purpose of this health consultation is to determine whether the soil gas levels pose a public health hazard.
The site is located at 110-112 Main Street in East Windsor, Connecticut, and consists of two adjoining parcels of land identified as block 37, lots 8 and 8A, and a portion of land on block 37, lot 18 . The property currently consists of the following: 21-unit condominium complex, commercial office building, commercial retail strip mall, and a vacant powerhouse building. The former mill building is one of the original structures to have survived a fire in May 1986, which also destroyed several other buildings in the complex. The former mill building was renovated into a 21-unit condominium that has been occupied since 1990. The area surrounding the former mill condominium building consists of paved areas, grassed sections, overgrown brush, and wooded areas. Broad Brook defines the northern and western boundary of the site.
On June 19, 1998, the Connecticut Department of Public Health (CT DPH) reviewed an investigation of site contaminants . That review was conducted to determine what immediate public health risks may be present for residents currently living in the former mill condominium building. The review recommended that the contaminated soils be remediated, and residents be relocated prior to initiating any large scale remedial activities. The CT DPH also recommended that children not play on the grounds of the condominium complex based primarily on surface soil results showing elevated concentrations of carcinogenic polynuclear aromatic hydrocarbons (PAHs).
After the June 1998 review was released, there was an expectation that the people living in the condominiums would be relocated. However, since that failed to occur, the CT DPH and ATSDR were asked to review the health implication of the ongoing potential exposures. On April 19, 2000, the CT DPH and ATSDR developed a Health Consultation examining surface soil sampling data. The surface soil was determined to be contaminated with PAHs at concentrations representing a Public Health Hazard to residents who may be exposed.
As a result of past operations on this site, there are numerous areas of contamination surrounding the former mill condominium building. These historic sources include above ground fuel oil storage tanks, a manufactured gas plant, cleaning solvents, plating solutions containing heavy metals, and a former coal storage area. There is a potential that ash wastes generated from the manufactured gas plant were disposed throughout the site.
Since the past practices at this site included the use and potential of disposal of solvents, there is the possibility that subsurface contamination may pose a risk of migrating through the soil and entering into the condominiums. In an effort to determine the risks posed by such contamination, a preliminary soil gas survey was conducted during December of 1999 . One of the findings of that investigation was the detection of elevated levels of 1,1-dichloroethylene. On March 30, 2000, the EPA conducted an indoor walk-through four of the condominium units. The purpose of the walk-through was to determine whether soil gas could potentially migrate into the living spaces of the condominiums. Observations made at that time indicated that there were no areas within the four units investigated from which soil gas would likely enter the occupied areas. The current structures do not include basements or sumps which if present, could increase the potential for soil gas infiltration.
The population potentially exposed consists of current and former residents of the 21-unit condominium building. Approximately 80 people live in the complex. Twenty of these residents may be young children (under age 6). This corresponds to, on average, two adults, one older child and one young child per condominium unit. The population includes units that are rented, as well as owner occupied units.
On June 8, 2000,  the EPA conducted a soil gas survey to characterize the volatile organic compounds (VOCs) inside the soil pore areas as close to the foundation of the condominium units as possible. Sixteen locations were selected around the condominium complex for this soil gas sampling. Probes were placed at depths ranging from 1 foot 6 inches, to a maximum depth of 4 feet 3 inches. The target depth was four feet, and the depths deviated from that target when an obstruction or groundwater was encountered. Table 1 lists the probe depths, groundwater depth, and whether a confirmatory canister sampling was conducted as that location (see also Figure 1).
|Probe Number||Sample Depth||Depth to Groundwater||Confirmatory Canister Site|
|1||4 feet 2 inches|| *||No|
|2||4 feet 3 inches||||No|
|3||4 feet 2 inches||||No|
|4||4 feet 0 inches||||Yes|
|5||4 feet 3 inches||||Yes|
|6||3 feet 9 inches||4 to 5 feet||No|
|7||2 feet 5 inches||||No|
|8||1 foot 6 inches||||No|
|9||4 feet 1 inches||||No|
|10||4 feet 3 inches||||Yes|
|11||3 feet 11 inches||||No|
|12||3 feet 5 inches||||No|
|13||4 feet 1 inches||||Yes|
|14||4 feet 1 inches||||No|
|15||3 feet 9 inches||||Yes|
|16||4 feet 3 inches||||No|
*Groundwater was not encountered during these probe installations.
All collection locations were selected to be as close as feasible to the foundation of the condominium. The data collected from all locations were analyzed using a portable gas chromatograph/mass spectrophotometer (GC/MS). The results of that analysis are presented in Table 2. The analysis targeted three chlorinated VOCs known to be site-related: trichloroethylene, 1,1,1-trichloroethane, tetrachloroethylene. The chemical previously detected in the preliminary analysis, 1,1-dichloroethylene, was also screened for, but not detected [personal communication between Gary Perlman (CT DPH) and Frank Gardener (US EPA), August 2000].1 Five of the locations where the highest recorded VOCs were measured, were subsequently sampled with a canister. The soil gas collected in the canister was subsequently sent to a laboratory for chemical analysis. The complete list of chemicals that were analyzed is listed in Appendix A. The result of the canister analysis is presented in Table 3.
Tables 2 and 3 contain the following column headings: frequency of detection, concentration range, background ambient air, health comparison value, and Connecticut residential volatilization criteria for soil vapor (CT RSR). The frequency of detection column lists a fraction of the total samples that detected the specified chemical. For example the value listed for tetrachloroethylene was 11/16. This indicates that eleven of the sixteen total samples detected this compound. The concentration range column provides information about the minimum and maximum levels detected. During the soil gas sampling, the ambient air background levels were simultaneously measured. The results are listed in the column labeled background ambient air.
The health comparison value column lists numbers that are used as guidelines for exposures to chemicals in the air. When concentrations of chemicals are below these values, no adverse health effects are likely. These levels were used to determine which chemicals should be examined further.
The last column contains the CT RSR soil gas volatilization criteria. This number is used to determine soil gas values that may result in indoor air levels posing a potential health hazard. The CT DEP and CT DPH jointly developed these health-based numbers. During the development of these numbers, both carcinogenic and non-carcinogenic health risks were considered. Consequently, when the soil gas levels are below the residential volatilization criteria, it is not anticipated that the soil gas concentrations would pose a risk to people living in residential dwellings. These criteria are based upon an ASTM2 model which simulates soil gas infiltration through a cracked foundation. The model incorporates many parameters including: soil characteristics, infiltration rates, and dilution factors. For example, the CT RSR for tetrachloroethylene is 11,000 ppb. This value represents the concentration, when detected in soil gas, that would not result in indoor concentrations at a level of health concern.
|Compound||Frequency of Detection||Concentration Range||Background Ambient Air||Health Comparison Value*||Source||CT RSR†|
* Health comparison value assumes a 70-kilogram adult inhales 20 cubic meters of air per day.
† Connecticut residential volatilization criteria for soil vapor 
§ Not detected.
‡ Risk-based Concentration for ambient air from EPA region III .
¶ Intermediate Minimum Risk Level.
Background ambient air was sampled over an eight-hour period at a location 144 feet south of the garage. The ambient air sampling was conducted during the soil gas sampling activities. All data were of acceptable quality, and no data were rejected.
|Compound||Frequency of Detection||Concentration Range||Background Ambient Air||Health Comparison Value†||Source||CT RSR‡|
|Methyl ethyl ketone||0/5||ND||ND||300||RfC‡‡||2,400,000|
| 1,1,2-Trichloro- |
* This contaminant was detected in the initial soil gas survey.
† Health comparison value assumes a 70-kilogram adult inhales 20 cubic meters of air per day.
‡ Connecticut residential volatilization criteria for soil vapor .
§ Not Detected.
¶ Chronic Minimum Risk Level.
# Cancer Risk Evaluation Guide.
** Risk-based Concentration for ambient air from EPA region III .
†† None Assigned.
‡‡ Reference Concentration.
On May 15, 2000, a public availability session was conducted. Approximately forty-five people attended this forum. During that meeting, many residents were asked about whether they were aware of the recommendations regarding the avoidance of activities that would disturb the soil. Many residents indicated that they were aware of these recommendations. However, several residents indicated that new tenants may not be aware of the restrictions. However, they indicated that the signs were clear and the message presented was easily understood. Residents did not express concern about soil gas measurements, but wanted to be kept informed of any soil gas results. Discussions then focused on legal issues related to the CT DEP's proposal to buy-out the condominiums.
In order to determine the health implications of exposures, the CT DPH and the ATSDR consider how people might come into contact with the contaminants. The CT DPH and ATSDR use a systematic process of reviewing available environmental data. If the concentration of a detected chemical in a specific media is below the health comparison value, then the exposure is not of health concern. Consequently, no further evaluation is required. However, if the concentration is above the health comparison value, then the exposure undergoes further evaluation to determine whether the exposure might result in the adverse health effects. If a chemical does not have any health comparison value, a review of the scientific literature is conducted to determine if the exposures are of health concern.
The indoor air potential exposure pathway was identified at the Millbrook Condominium Site after evaluation of the existing soil gas data. This potential pathway was assessed as to whether it represents a health concern for the public. The evaluation is presented below.
Potential Exposure PathwaySoil Gas.
The potential for exposure to soil gas and, therefore, adverse health effects from exposures, at this site is low for three main reasons. First the EPA determined that there were no areas within the four units investigated from which soil gas could enter the occupied areas. Second, the current structures do not include basements or sumps which if present, could increase the potential for soil gas infiltration. Third, if the chemicals enter the occupied areas, the effect of dilution and other factors, would result in concentrations below a level of concern.
All soils contain gaps between the particles which are filled with either liquids (usually water) or gases. Soil gas is the term used to describe the gas that fills these voids. Volatile organic contaminants in on-site and off-site groundwater will tend to separate into a soil gas phase. Elevated levels of VOCs in the soils and shallow groundwater may contaminate ambient air on-site and/or off-site depending upon the migration potential of the soil gas. Site contaminants could migrate through porous media as soil gas and enter confined building spaces (basements) through crawl spaces, plumbing holes, other floor holes (e.g., sumps) and foundation cracks, and contaminate indoor air.
The chemical, 1,1-dichloroethylene, which was originally detected at elevated levels in the soil gas preliminary survey in December of 1999, was not subsequently detected in the current round of sampling. There has been no confirmation of that compound in any canister sampling rounds.
Seven chemicals were detected below their respective Health comparison values and CT residential volatilization criteria for soil vapor, and thus do not represent health concern. The following chemicals met the above criteria:
methyl ethyl ketone
Four chemicals were detected above their respective health comparison values, but were below their respective CT residential volatilization criteria for soil vapor. The health comparison values for these compounds were developed for ambient air exposures. Since levels detected in soil gas are diluted when infiltration occurs, the realistic indoor air exposure concentration will likely be well below health comparison values. Moreover, since the CT residential volatilization criteria for these chemicals were not exceeded, these four chemicals do not pose a public health conern.
The seven remaining chemicals did not have any CT RSRs. Five of which were detected at concentrations below their respective health comparison values for direct inhalation. These five therefore do not represent a health concern. These chemicals include the following:
These are two remaining chemicals which lack CT RSRs, and were detected above their respective health comparison values. These chemicals are 1,2,4-trimethylbenzene and 1,3,5-trimethylbenzene. Since levels detected in soil gas are diluted when infiltration occurs, the effect of dilution and other factors, would result in concentrations that are likely below a level of concern. Consequently, concentrations of these two chemicals do not pose a public health concern.
Based on ATSDR's public health hazard categories (See Appendix B), the soil gas concentrations, as measured during June of 2000, around the foundation of the Millbrook Condominium units represent no apparent public health hazard to occupants of the dwellings. The conclusion is based on two main factors. The first is the low potential for soil gas infiltration. The second is the effects of dilution and other factors on any infiltrating gases that would result in concentrations below a level of health concern. It should be noted that however, that this conclusion is based on a limited data set taken over a short period of time. This conclusion could be revised if new data become available.
None at this time.
The Public Health Action Plan for the Millbrook Condominiums site contains a description of the actions completed and to be taken by the Agency for Toxic Substances and Disease Registry, the Connecticut Department of Public Health, and the Connecticut Department of Environmental Protection. Included in this plan is a commitment on the part of the Agency for Toxic Substances and Disease Registry and the Connecticut Department of Public Health to follow up on this plan to ensure that there is implementation.
The public health actions implemented include:
- The Connecticut Department of Public Health and the CT DEP have advised residents of the 21-unit condominium complex that children should not play on the grounds of the former mill building property, as well as areas near the residential condominium building.
- The Connecticut Department of Public Health and the CT DEP have advised residents of the 21-unit condominium complex that children and adults should not engage in digging or gardening activities throughout the site and should keep their pets from disturbing the top layer of soil.
The public health actions to be implemented include:
- The Connecticut Department of Public Health and the CT DEP will review and summarize additional environmental sampling data.
- The Connecticut Department of Public Health will conduct environmental health education for local public health officials, and local citizens regarding the results of this health consultation and previous recommendations issued for this site.
- The CT DPH and ATSDR will review any additional data, if they become available.
Gary D. Perlman, MPH
Environmental Epidemiology and Occupational Health
Connecticut Department of Public Health
ATSDR Regional Representative:
US EPA Region 1
ATSDR Technical Project Officer:
Superfund Site Assessment Branch
Division of Health Assessment and Consultation
Agency for Toxic Substances and Disease Registry
The Health Consultation for the review of the Soil Gas Sampling Data for the Millbrook Condominium Site was prepared by the Connecticut Department of Public Health under a cooperative agreement with the Agency for Toxic Substances and Disease Registry (ATSDR). It is in accordance with approved methodology and procedures existing at the time the health consultation was initiated.
Gregory V. Ulirsch
Technical Project Officer, SPS, SSAB, DHAC
The Division of Health Assessment and Consultation (DHAC), ATSDR, has reviewed this Health Consultation and concurs with its findings.
Chief, SSAB, DHAC, ATSDR
- U.S. Environmental Protection Agency New England Regional Laboratory Office of Environmental Measurements and Evaluation. June 2000. Soil Gas Survey final report Mill Brook Condominiums East Windsor, Connecticut.
- Agency for Toxic Substances and Disease Registry. Health Consultation Assessment of Surface Soil Sampling Data at the Millbrook Condominiums Site East Windsor, Hartford County, Connecticut. Atlanta: US Department of Health and Human Services; April 19, 2000.
- U.S. Environmental Protection Agency. Data sheets concerning volatile organic screening results for soil gas samples collected on December 10, 1999, at Millbrook Condominium Site. East Windsor, Connecticut. 1999.
- Connecticut General Statutes 22a-133k (rev to January 1, 1999).
- EPA Region 3. April 2000 Update. Risk-Based Concentration Table. Available at: http://www.epa.gov/reg3hwmd/risk/riskmenu.htm . Accessed August 11, 2000.
|Carbon Tetrachloride||Methyl Bromide|
|Chlorobenzene||Methyl Ethyl Ketone|
|Chloroethane||Methyl isobutyl ketone|
|4-Ethyl Toluene||Vinyl Chloride|
|A. Urgent public health hazard||This category is used for sites that pose an urgent public health hazard as the result of short-term exposures to hazardous substances.|| |
evidence exists that exposures have occurred, are occurring, or are likely to occur in the future AND
estimated exposures are to a substance(s) at concentrations in the environment that, upon short-term exposures, can cause adverse health effects to any segment of the receptor population AND/OR
community-specific health outcome data indicate that the site has had an adverse impact on human health that requires rapid intervention AND/OR
physical hazards at the site pose an imminent risk of physical injury
|B. Public health hazard||This category is used for sites that pose a public health hazard as the result of long-term exposures to hazardous substances.|| |
evidence exists that exposures have occurred, are occurring, or are likely to occur in the future AND
estimated exposures are to a substance(s) at concentrations in the environment that, upon long-term exposures, can cause adverse health effects to any segment of the receptor population AND/OR
community-specific health outcome data indicate that the site has had an adverse impact on human health that requires rapid intervention
|C. Indeterminate public health hazard|| |
This category is used for sites with incomplete information.
limited available data do not indicate that humans are being or have been exposed to levels of contamination that would be expected to cause adverse health effects; data or information are not available for all environmental media to which humans may be exposed AND
there are insufficient or no community-specific health outcome data to indicate that the site has had an adverse impact on human health.
|D. No apparent public health hazard||This category is used for sites where human exposure to contaminated media is occurring or has occurred in the past, but the exposure is below a level of health hazard.|| |
exposures do not exceed an ATSDR chronic MRL or other comparable value AND
data are available for all environmental media to which humans are being exposed AND
there are no community-specific health outcome data to indicate that the site has had an adverse impact on human health.
|E. No public health hazard||This category is used for sites that do not pose a public health hazard.|| |
no evidence of current or past human exposure to contaminated media AND
future exposures to contaminated media are not likely to occur AND
there are no community-specific health outcome data to indicate that the site has had an adverse impact on human health.
1 However, 1,1-dichloroethylene was not listed in the data tables supplied by the US EPA.
2 ASTM (the American Society for Testing and Materials) was organized in 1898, and is one of the largest voluntary standards development organizations in the world. ASTM is not-for-profit organization that provides a forum for the development and publication of voluntary consensus standards for materials, products, systems and services. ASTM develops standard test methods, specifications, practices, guides, classifications, and terminology in 130 areas covering subjects such as metals, paints, plastics, textiles, petroleum, construction, energy, the environment, consumer products, medical services and devices, computerized systems, electronics, and many others. [source: ASTM. Frequently Asked Questions, what is ASTM? Available at: http://www.astm.org. Accessed August 18, 2000.]