Vapor Migration Investigation
MADISON KIPP CORPORATION
MADISON, DANE COUNTY, WISCONSIN
Groundwater and soils at certain locations at the Madison Kipp Corporation (MKC) arecontaminated with high levels of chlorinated solvents. Investigations have determined the extentof soil and groundwater contamination both on and off of the MKC property. Contamination onthe east side of MKC property is next to private, residential property, with some homes as closeas 50 feet to the on-site source . Only low levels of solvent contamination are in nearbyresidential soils and pose no apparent public health hazard. For off-site groundwater, solventcontamination was found at low levels in shallow groundwater and is not a potential vapormigration concern. Municipal water serves the area, which is not affected by contamination fromthe MKC property.
There is sufficient chlorinated solvent contamination in subsurface soils at the source on theeastern side of the MKC property to release solvent vapors into soils, but soil gas data are notavailable. Vapor migration potential at the MKC site is an indeterminate public health hazard. In order to evaluate the potential for soil vapor migration and in consideration of theselected in-situ soil treatment remedy, DHFS recommends a soil gas investigation to determinewhether vapors of chlorinated solvents are migrating away from the MKC property and towardsthe nearby homes. To rule out the potential for vapor migration and intrusion into nearbybuildings, soil gas should be tested in between the known sources of chlorinated solvents andnearby homes. The soil gas testing should be conducted in conjunction with the implementationof the soil in-situ treatment remedy. At this time, DHFS does not recommend the indoor air sampling of homes.
The Wisconsin Department of Health and Family Services (DHFS), in coordination with the Madison Department of Public Health, is evaluating the public health implications of chlorinated volatile organic compounds (VOC) or solvents off-gassing from contaminated groundwater and sub-surface soils on the Madison-Kipp Corporation (MKC) and the potential for soil gas vapors to migrate onto neighboring residential properties. The Madison Department of Public Health and DHFS questioned whether a public health hazard could result from vapor intrusion if site-related contamination migrated to nearby buildings. The MKC facility is located at 201 Waubesa Street, Madison, Wisconsin. DHFS staff most recently visited the property on July 16, 2003.
Groundwater investigations at the MKC property have found elevated levels of solvents, some at levels above the Wisconsin Groundwater Quality Public Health Enforcement Standards for drinking water (NR140). Table 1 summarizes the concentration range of chlorinated solvents found in groundwater at the MKC property that were above Wisconsin groundwater standards (Dames & Moore, 1999). Petroleum-related solvents have also been found in groundwater around the MKC property. Benzene was found in three monitoring wells above the Wisconsin Groundwater Enforcement Standard of 5.0 µg/L (micrograms per liter), with the highest level detected at 23 µg/L (in monitoring well MW-4S). All other petroleum-related solvents detected in these wells were less than their respective groundwater standards. Area households and businesses obtain drinking water from municipal water, which is not affected by contamination from the MKC property.
|Chemical||Highest Level Detected||Lowest Level Detected||Frequency of Detection in Groundwater Monitoring Wells||Wisconsin Groundwater Enforcement Standarda|
a-Wisconsin NR140 Groundwater Quality Public Health Enforcement Standard
*- Exceeds NR140 Groundwater Enforcement Standard
The investigations at the MKC property included follow-up rounds of groundwater sampling ofexisting monitoring wells, studies of local hydrogeology, and the installation of five additionalgroundwater monitoring wells. Between August 1999 and May 2002, ten additional rounds ofgroundwater samples were collected from seven older monitoring wells, as well as four sampling rounds from the four newer wells (Table 2).
In early 2001, a pair of monitoring wells were installed along the eastern side of the MKC property (MW-5S and MW-5D). Four rounds of groundwater sampling from this pair of monitoring wells found the highest levels of chlorinated solvents on the MKC property. In shallow groundwater (25 to 30 feet below ground surface) from this area (MW-5S), tetrachloroethylene and cis-1,2-dichloroethylene were detected at 680 and 21 µg/L, respectively, and trichloroethylene was found at 100 µg/L. In deeper groundwater (MW-5D), tetrachloroethylene and cis-1,2-dichloroethylene were detected at 8,800 and 300 µg/L, respectively. The elevated concentrations in deeper groundwater (greater than 30 feet) are indicative that contaminants are migrating downwards into the aquifer. Solvents in deeper groundwater are less likely to affect the levels of solvent vapors in shallower, unsaturated soils.
|Chemical||Highest Level Detected||Lowest Level Detected||Frequency of Detection in Groundwater Monitoring Wells||Wisconsin Groundwater Enforcement Standarda||EPA Generic Screening Levelsb|
a - Wisconsin NR140 Groundwater Quality Public Health Enforcement Standard
b - For 1x 10-6 Risk. Source: Table 2c, US Environmental Protection Agency. Draft Guidance for Evaluating the Vapor Intrusion to Indoor Air Pathway from Groundwater and Soils (Subsurface Vapor Intrusion Guidance). http://www.epa.gov/epaoswer/hazwaste/ca/eis/vapor.htm November 29, 2002.
* - Exceeds NR140 Groundwater Enforcement Standard
nd - Not Detected
n/a - Not Available
Contaminated groundwater was found in the monitoring well cluster at MW-5. In follow-up,during January 2002, a soil investigation was conducted along the eastern side of the MKCbuilding to identify a source of the chlorinated solvents in groundwater. Soil samples werecollected from fifteen geoprobe borings. Laboratory analysis found elevated concentrations ofchlorinated solvents from four sample locations at depths between 1 and 4 feet below the groundsurface (BGS). This location is the eastern side of the MKC building where there was previouslyan exhaust vent that discharged solvent vapors.
The subsurface soil samples with the highest solvent concentrations were directly beneath this source at near surface depths of 1 to 4 feet BGS. Concentrations in these subsurface soils ranged from 5,960 to 782,000 micrograms per kilogram (µg/kg or parts per billion) for tetrachloroethylene, 236 to 49,900 µg/kg for cis-1,2-dichloroethylene, and 5,590 to 8,470 µg/kg for trichloroethylene.
Soil sampling data indicated that the source of contaminants lies within the Madison-Kipp property boundary and is not on neighboring residential properties. However, during the winter of 2002, MKC conducted an off-site soil investigation on residential properties adjacent to the MKC property. The investigation identified off-site soil contamination near the surface at a few locations on several properties. These sample locations were 5 to 10 feet from the MKC property boundary and at shallow depths of 2 to 4 feet BGS. Tetrachlorethylene was found in these soils at relatively low levels, which were between of 31.0 and 1,430 µg/kg. These concentrations in shallow surface soils are not a direct contact health concern.
MKC has proposed an in-situ treatment for contaminated soil impacted with chlorinated solventcompounds. The treatment will involve a fluid drilling process, which involves injecting areagent into the soil to oxidize and breakdown the in-situ organic contaminants and establish anoxygen and nutrient enriched environment for proliferation of biodegraders. The in-situ processis a non-violent, controlled reaction producing no heat. If approved by DNR as the remedy, soilgas monitoring should be implemented to evaluate the remediation process and any potential forvapor migration.
Vapor Migration & Intrusion Issues
When large sources of chlorinated solvents are found in sub-surface soils and shallowgroundwater, vapors can be released and migrate upwards through soils. Vapors that moveupwards through soils can reach the open surface of the ground, are released to outdoor air,quickly disperse into the atmosphere, and are not a health concern.
When vapors from groundwater contaminated with solvents enters a home or office, the vaporsoften move through dirt floors or cracks in the foundation, become part of the air inside of thestructure, and then are breathed by a resident or worker. Under certain circumstances, the levelsof chlorinated solvents entering indoor air can accumulate at high enough levels to pose a long-term, unacceptable inhalation health risk to people who live or work in the structure. Thisconcept is referred to as "vapor migration and intrusion to indoor air" (US EPA, 2002).
When solvents are at very high levels in soils and are located above the water table, vapors can move directly from the source, through the soils, and enter the indoor air of nearby buildings.
Elevated levels of chlorinated solvents are in shallow soils at certain locations on the MKCproperty. It is possible that solvent vapors may also be migrating through soils and onto adjacentresidential properties
Understanding the full degree and extent of shallow groundwater contamination is very importantin assessing the potential for vapor intrusion into indoor air. The extent of groundwatercontamination around the MKC has been largely determined, and current data indicate shallowgroundwater flow is primarily south-southwest. A groundwater monitoring well nest, locatedsouthwest of the source and in proximity to the residences of concern, indicate that beyond thesource area, only very low levels of chlorinated solvents are in shallow groundwater.
Shallow groundwater contaminated with chlorinated solvents is the most common source of avapor migration and intrusion problems when solvent vapors move upward and enter homes andbuildings located directly above the contaminant plume. Investigations at other sites with highlevels of chlorinated solvent contamination in shallow groundwater have found solvent vapors insoil gas and unacceptable levels in the air of homes located directly above the plume. However,the groundwater contaminant plume coming from the MKC property is not likely to cause such avapor intrusion issue in nearby homes.
On the MKC property, only groundwater beneath the contaminant source and the actual sourcehave sufficient solvent concentrations to produce a measurable and substantial amount ofchlorinated solvent vapors that are possibly being released into subsurface soils. The potentialfor elevated levels of soil gas vapors on the MKC property should not be automaticallyinterpreted that vapor intrusion is occurring in nearby homes. However, since homes are as nearas 50 feet to the source on the MKC property, there is sufficient justification to pursue aninvestigation and further evaluate the vapor migration and intrusion pathway.
This pathway must first be examined on the MKC property by measuring the levels of solventvapors in soil gas from areas between the sources and nearby buildings. Under the current EPAdraft guidance, measuring the direct evidence of soil gas is the recommended first step and isimportant in demonstrating whether the potential threat exists for vapor intrusion (US. EPA,2002). It has been found that indoor air sampling alone is problematic, unless many indoor airsamples are collected simultaneously with many soil gas samples (Johnson, 2001).
Soil sampling data of only the contaminant source does not typically provide sufficientinformation to evaluate soil vapor migration and intrusion. In this case, the soil sampling dataindicate that a contaminant source is above and separate from the groundwater table. For thisreason, it is important to investigate the potential for vapor migration directly from the source inthe unsaturated soils.
Solvent vapors may be in soil gas along the eastern side of the MKC property and may bemigrating towards nearby homes. DHFS recommends that soil gas samples be collected fromsampling points between the known soil and groundwater sources of chlorinated solvents andnearby homes in conjunction with the in-situ remedy. DHFS does not recommend the samplingthe indoor air of nearby homes at this time. Once soil gas data are available, DHFS will evaluatethe data and determine whether further soil gas data are needed or if the indoor air of nearbyhomes needs to be tested.
For additional information about the public health implications of solvent vapor intrusion intoindoor air of buildings, please refer to the DHFS guidance on vapor intrusion (WDHFS, 2003).
The long-term exposure to chlorinated solvents in indoor air can be a health risk to children. Further investigation of the vapor intrusion pathway is needed to assess whether such anexposure and unacceptable health risk exist for children living in homes adjacent to the Madison Kipp Corporation property.
- Vapor migration potential at the MKC site poses an indeterminate public healthhazard. Groundwater and soils at certain locations on the MKC are contaminated with high levels of chlorinated solvents. Vapors from the solvents in the soil and groundwater could migrate to nearby homes and enter indoor air at levels that could be of health concern, but data are not available to rule out this pathway.
- Nearby homes and businesses obtain drinking water from municipal water, which is notaffected by contamination from the MKC property.
- On private property adjacent to MKC, investigations have only found low levels ofsolvent contamination in shallow soils at locations closest to the MKC property. Directcontact with these soils poses no apparent public health hazard.
DHFS recommends an environmental investigation to evaluate whether vapors of chlorinated solvents are migrating away from the MKC property and toward nearby homes.
- DHFS will evaluate the results of the soil gas solvent vapor investigation and assess the potential for a completed exposure pathway intrusion and whether further investigation is warranted.
- DHFS will continue to collaborate with the Madison Department of Public Health and theWisconsin Department of Natural Resources regarding public health issues andcommunity concerns related to the Madison Kipp Corporation.
- Dames and Moore Group Company. Project Status Report, Madison-KippCorporation, Madison, WI. Correspondence to L Lester, Wisconsin Departmentof Natural Resources. Madison, WI: Dames & Moore. June 17, 1999.
- US Environmental Protection Agency. Draft Guidance for Evaluating the VaporIntrusion to Indoor Air Pathway from Groundwater and Soils (Subsurface VaporIntrusion Guidance). http://www.epa.gov/epaoswer/hazwaste/ca/eis/vapor.htm November 29, 2002.
- Johnson PC, Ettinger RA, Kurtz JP, Bryan R and Kester JE. Migration of SoilGas Vapors to Indoor Air: An Empirical Assessmen of Subsurface Vapor-to-Indoor Air Attenuation, Factors Using Data from the CDOT-MTL Denver,Colorado Site. Technical Bulletin. American Petroleum Institute. 2001.
- Wisconsin Department of Health & Family Services. Guidance for Professionals:Chemical Vapor Intrusion and Residential Indoor Air. Madison, WI: DHFS. February 13, 2003.
- Wisconsin NR140. Groundwater Quality Public Health Enforcement Standard. March 2000.
Henry Nehls-Lowe, MPH
Bureau of Environmental Health
Division of Public Health
Wisconsin Department of Health & Family Services
This Madison Kipp Corporation vapor migration public health consultation was prepared by theWisconsin Department of Health and Family Services under a cooperative agreement with theAgency for Toxic Substances and Disease Registry (ATSDR). It is in accordance with approved methodology and procedures existing at the time the public health consultation was begun.
Technical Project Officer, SPS, SSAB, DHAC
The Division of Health Assessment and Consultation, ATSDR, has reviewed this public health consultation and concurs with the findings.
Chief, SPS, SSAB, DHAC, ATSDR