LAYTON -- Hill Air Force Base continues to sample the indoor air of Layton homes situated above shallow, contaminated groundwater plumes, as the base works to mitigate any volatile vapors coming off the groundwater.
Base officials attended the Layton City Council meeting last week to provide city leaders with an annual update of the long-term cleanup of Operable Unit No. 8.
That area, as defined by the base, is where groundwater plumes contaminated by trichloroethylene (TCE) and 1,2 DCA -- chemicals originating from a degreaser the base used for years for aircraft -- have flowed off base and into area neighborhoods.
OU-8 takes in the southern area of the base, and extends south into Layton and Clearfield. OU-8 was established in 1993 as part of a plan to consolidate all groundwater contamination under the base's industrial complex.
Based on the concern about vapors rising from the shallow, contaminated groundwater as cleanup of the plumes continues, indoor air sampling is occurring in hundreds of Layton homes near the base, said Lance Kovel, OU-8 project manager.
The limited indoor air samplings suggest volatile organic chemicals, including TCE, 1,2 DCA and chloroform, were found in indoor air in homes near the OU-8 groundwater.
The 2010 air-sampling statistics show 2,712 homes in cities around the base have been contacted, 992 of them in Layton, Kovel said.
Of the Layton homes, 223 have had air sampling performed. Only one of those homes detected vapor at an action level, Kovel said.
When a home is above the action level, the base does additional sampling to determine the location and source of the vapor, said Erik Dettenmaier, base air program manager.
"If it is determined it is coming from the base, we then install a vapor removal system inside the home," he said.
Having only one of the 223 Layton homes sampled this year showing vapor above action levels, Dettenmaier said, indicates base officials are doing a good job of mitigating the problem in the homes that have had vapor intrusion.
"As long as there is potential for these vapors to move up into homes," he said, "there will be air sampling."
Councilman Scott Freitag asked base officials about the disparity between the number of homes contacted, and the number of homes that allow indoor air sampling to be done.
Residents' unwillingness to participate stems either from the inconvenience and intrusion air sampling places on them, or the resident declining the offer is remaining ignorant in the event vapor detection could make it more difficult to resell their home, said Jarrod Case, remedial program manager for the base.
Councilman Barry Flitton said he would equate residents' ignoring the problem to people "burying their heads in the sand."
The council also was concerned about the safety of the city's drinking water.
The contaminated groundwater is limited to the shallow aquifer and does not pose a threat to the drinking water supply, Kovel said. The plumes the base is responding to are within 200 feet of the surface, he said, while cities draw drinking water from aquifers that are 600 feet deep.
Between each aquifer there is also a natural geological barrier preventing shallow groundwater from leaking into the drinking water, he said.
Current monitoring data reveals the contaminated plumes in Layton do not appear to be expanding, Kovel said.