Targus was retained to perform an environmental site assessment (Phase I ESA and Additional Non-ASTM services) of an office park encompassing five separate six-story buildings and a parking garage on approximately 50 acres of land. The improvements were constructed between 1998 and 2001.
No recognized environmental conditions were identified during completion of the Phase I ESA. Short term radon testing was performed in three ground floor locations per building in accordance with the client’s scope of services requirements. Radon concentrations in one of the buildings were above the EPA Action Level of 4.0 picoCuries per liter of air (pCi/L). Additional short-term sampling in the building confirmed the initial results, as did long-term testing for 351 days.
Discussions with maintenance personnel indicated that a slab penetration was identified in the building and patched prior to long-term testing. Based on the long-term testing results, it appeared that another pathway for indoor migration of radon gas was present. In order to assess potential pathways, Targus conducted a search of the floor in and around the suite with the highest radon concentrations and in the surrounding areas. Targus identified a slab joint in a stairwell as a suspect radon entry point.
Targus deployed a real-time radon detector to evaluate the radon concentrations in each of the first-floor tenant suites, and to spot-check suspect radon entry points. Initial sniff tests were conducted for thoron. Thoron gas has a very short half-life, and was a better indicator of sub-slab entry points. Once potential entry points were identified, radon concentrations were measured. The results of the real-time testing suggested that the ineffectively sealed joint in the floor slab exposed in the stairwell was the main entry point for radon. The joint seal was repaired, and follow-up real-time radon testing was performed. Radon concentrations above the EPA residential dwelling target level were not detected at multiple locations tested in the building. Targus recommended sealing additional joints in the slab, if identified during future renovations on the ground floor of the building.