CLEARFIELD -- Three intermingled and contaminated plumes are not causing health risks to residents, and now plans are for continued monitoring through 2014 to determine the best course to fix the problem.
The Hill Air Force Base Environmental Restoration Directorate updated the Clearfield City Council regarding the indoor sampling program and groundwater contamination.
There are three plumes in the area, including a shallow trichloroethene (TCE) one found between 8 and 100 feet below the ground surface, a shallow tetrachloroethene (PCE) one found approximately 25 feet below the surface, and a deep TCE plume found between 175 and 290 feet below the surface.
Maximum TCE concentrations for the shallow and deep plumes are 200 parts per billion and 750 parts per billion, respectively. The Environmental Protection Agency drinking water standard is 5 parts per billion.
The maximum PCE concentration is 63 parts per billion.
"The contamination is not affecting city wells or drinking water," said project manager Robert Wallace.
Wallace explained they have already done a feasibility study outlining remediation alternatives available for cleanup of the three plumes. This was finished in September.
He said the next step is to create the proposed plan, which was originally due in March 2010. Because of the limited data for deep TCE and PCE plumes, the Air Force has opted to defer the plan until 2014 for additional studying and monitoring.
"The plumes are not a risk to the residents' health or the environment," Wallace said. "We need the additional time to observe the plumes and make smart decisions."
With the extended timeline, they will be able to get four more years of data. In the meantime, they will still sample groundwater and observe to make sure no problems are developing.
Indoor Air Sampling Program Manager Jarrod Case also explained they are continuing air sampling.
Case said the only way residents could be exposed is to drill a well to access the shallow water, which is illegal, or be exposed to vapors coming off the plumes as the water evaporates.
"We check to make sure that is not happening," Case said.
He explained historically about 1,742 homes in communities surrounding the base were sampled. Of those, 160 were homes in Clearfield.
Six of those homes had detections above action levels, with eight below action levels. However, Case said, those homes were found to have indoor sources for contamination and were not related to the plumes.
In 2009, 732 homes were sampled, including 55 in Clearfield. One Clearfield home had detections above action levels and two below. The other 52 had no detection issues.
"We offer sampling annually, and we will continue to," Case said. "There are ways to fix any problems that are found."
So far, all problems have been traced to indoor sources within the affected homes.