SGM-SF_2017with 12/20 Revisions

Vapor Intrusion (VI)—Informational Guidance 66 ANSI/AARST SGM-SF 2017 (with 1220 revisions) Soil Gas Mitigation Standards for Existing Homes A-3.4.5 Soil Gas Measurements Soil gas measurements are often conducted in association with the initial site characterization. Soil gas measurements under the building and within ASD duct piping can be compared with measurements taken during initial ASD commissioning to help characterize evidence of a shifting or depleted source. Soil gas measurements within ASD duct piping are also employed to evaluate regulatory compliance with limits on discharged hazardous vapors. Monitoring for changes of soil gas concentrations within duct piping is one procedure employed for chemical vapor intrusions sites when there is reason to believe that the systemmight eventually not be needed. However, check with your state regulatory agency for conditions that would fully warrant possible decommissioning. A-3.5 Decommissioning systems In certain instances, the source of hazardous soil gas can be found to have migrated away from a building or found to be depleted in hazardous concentrations, either naturally or as a result of remediation and related efforts. In such circumstances, considerations can include discontinued operation of soil gas mitigation systems and ongoing stewardship. A-3.5.1 Decommission Decisions Decisions to decommission a system due to evidence of a shifting or depleted source are beyond the scope of this document but normally include documented measurements of soil gas from under the building with the system inactive for an adequate period of time prior to the measurement. A test for radon gas should also be conducted at this time to inform the property owner if there are other reasons to warrant continued system operation. A-3.5.2 Advise Property Owner It is recommended to advise the owner that a resident can continue his/her own testing for continued verification