Demonstration of Compliance with Soil Gas Remediation Objectives for the Outdoor and Indoor Inhalation Exposure Routes

Section 742.227  Demonstration of Compliance with Soil Gas Remediation Objectives for the Outdoor and Indoor Inhalation Exposure Routes a)         For purposes of the outdoor inhalation exposure route and the indoor inhalation exposure route, compliance with soil gas remediation objectives developed under any tier shall be demonstrated in accordance with this Section by comparing the contaminant concentrations of discrete samples at each sample point to the applicable soil gas remediation objective. b)         This Section applies to exterior soil gas samples for the outdoor inhalation exposure route, near-slab soil gas samples collected outside of an existing building for the indoor inhalation exposure route, and exterior soil gas samples collected at the footprint of a potential building for the indoor inhalation exposure route.  Proposals to use sub-slab soil gas data for the indoor inhalation exposure route shall follow Section 742.935(c). c)         Sample points shall be determined by the program under which remediation is performed. d)         When collecting soil gas samples: 1)         Use rigid-wall tubing made of nylon or Teflon ® or other material approved by the Agency; 2)         Use gas-tight, inert containers to hold the sample. For light sensitive or halogenated volatile chemicals, these containers shall be opaque or dark-colored; 3)         Purge three volumes before obtaining each discrete soil gas sample; 4)         Use a helium tracer or other leak apparatus detection system approved by the Agency; and 5)         Limit the flow rate to 200 ml/min. e)         Soil gas samples shall be analyzed using a National Environmental Laboratory Accreditation Program (NELAP) certified laboratory. f)         Soil gas remediation objectives shall be compared to concentrations of soil gas collected at a depth at least 3 feet below ground surface and above the saturated zone.