Program developed to ensure long-term O&M and performance of vapor intrusion mitigation

EPA Region 7 has developed a comprehensive VI program to address the installation and long-term operation and maintenance (O&M) of VI mitigation systems, as well as assessment sampling for future systems, in homes near the Chemical Commodities, Inc. Superfund site (CCI). Region 7's VI Program Implementation Manual, which describes decision processes and procedures as well as roles and responsibilities for these activities, is helping ensure protection of area homes and information outreach to the community.

The CCI site is an inactive chemical recycling facility located in central Olathe, a suburb of Kansas City. From 1951 until 1989, the facility stored and processed a variety of chemicals including surplus industrial and laboratory chemicals, many of which were hazardous substances and wastes. Materials were stored in aboveground and underground storage tanks and other containers throughout the site. Poor handling and housekeeping practices led to spills, leaks, and fires.

Following a fire in 1977, site investigations found that soil and groundwater at CCI were contaminated with elevated levels of metals, pesticides, PCBs, semi-volatile organic compounds, and volatile organic compounds (VOCs). Subsequent investigations indicate that the groundwater contaminant plume extends offsite, having migrated at least a distance of 1,000 feet beneath a neighborhood west of the site. Cleanup activities have included removal of stored chemicals from the site, limited excavation of onsite soil, and removal of all onsite buildings.

In 2001, the EPA began investigating the possibility of vapor intrusion into nearby homes. Air sampling performed in homes around the CCI facility found that VI raised concern for potential exposure to some residents. TCE was found to be the most prevalent VOC in the groundwater and was detected above the health-based action level in several homes.

As a result of these findings, EPA signed an action memorandum calling for installation of VI mitigation systems in homes near CCI. The Boeing Company, one of several potentially responsible parties, agreed to pay for and install VI systems in those homes identified by the EPA and to further assess additional homes in other nearby neighborhoods. Homes were selected for sampling based on their proximity to the CCI site and on the data collected during site characterization. Those with indoor air levels of target substances above the action levels (e.g., greater than 2 µg/m3 for TCE) qualified for a VI system. However, residents had the option of turning down installation of a system.

In total, indoor air was sampled in more than 100 homes and VI systems were installed in 45 homes (Figure 3). The VI systems are the same as those used to remove naturally occurring radon in parts of Kansas. A collection pipe was placed on the ground beneath homes with crawl spaces and vapor barriers were installed. Vapors collecting in the pipe from beneath the vapor barrier are extracted with a fan and vented to the outside via a vertical exhaust pipe that discharges above the roof. Homes with basements are vented to the roof by placing the vertical pipe through the concrete slab and into the subsurface.

The final remedy specified in a 2005 ROD includes a long-term VI program as part of the overall approach to groundwater remediation at the site. Region 7 is responsible for the O&M of the VI systems and O&M work, which will be overseen by Region 7, involves annual routine inspections to verify that each system is working properly. Before the first inspection, the homeowner must sign an access agreement that will allow EPA and its contractors to enter the home to perform O&M. The inspections take note of any structural changes to the home that may have occurred since the installation of the VI system or previous inspection which could impact the effectiveness of the system.

In addition to O&M, the VI program includes assessment sampling for homes without VI systems, installation of additional VI systems as necessary, and performance monitoring of any newly installed systems. The need for additional assessment sampling will be largely based on groundwater data, which could indicate plume migration into areas that have not previously been tested.

Overall, the VI systems installed in Olathe have been effective at reducing contaminant levels to levels below the EPA action levels. Annual inspections have revealed that most frequent problems involve tears or rips in the membranes and inadequate sealing around the edges of the vertical pipes. Many of the membranes have been replaced with a heavier-duty material, and pipes have been properly sealed. The mechanical components generally have had few problems. Because the VI systems have a life expectancy of 10-15 years, EPA anticipates the need to periodically replace mechanical components such as fans as the systems age over time.

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