Targus was retained to perform an environmental site assessment (Phase I ESA and additional non-ASTM services) of a recently-constructed apartment property. As an additional service, Targus conducted short-term screening of a subset of the ground-contact dwelling units for radon.
A substantial minority of units were found to exceed the EPA Action Level of 4.0 picoCuries per liter of air (pCi/L). In an effort to secure more reliable indicators of average radon concentrations, long-term post-closing testing was conducted. Replicate detectors retrieved after a six-month exposure period confirmed elevated radon levels in a subset of units tested, including those that were found to be elevated during the initial screening. While the remainder of detectors were left undisturbed, Targus conducted a pilot test in several units with the greatest confirmed indoor radon concentrations. Sub-slab depressurization (SSD) was applied to confirm wide pressure field extension beyond the limits of just the units targeted and reductions in interior radon concentrations during a period before and after the test.
Based on the results of the pilot test, permanent SSD systems will be installed at the previously-targeted units and at other units that may be confirmed to have elevated indoor radon concentrations. At present we are reviewing building construction drawings to identify the potential presence of vertical pipe chases that may allow for interior placement of risers and installation of rooftop fans. This approach is expected to provide better vacuum distribution and also avoid exterior piping that is believed by the owner to detract from building appearance.