Project Overview: Prior to remedial activities at a former manufactured gas plant (MGP) site in the metropolitan area of Chicago, Cardno ChemRisk was asked to perform a risk assessment of potential vapor emissions that might occur during the remediation of the site.

Our Approach: Our team estimated vapor emissions from soil due to various excavation activities for different areas of the site and performed air dispersion modeling to estimate the air concentrations of the chemicals of interest at different offsite locations, such as a mini golf course, a trade school, and various commercial establishments.  The results of the air modeling were also used to calculate risk-based fenceline air concentration objectives protective of the same offsite locations. The fenceline air concentration objectives were developed to ensure that remediation activities did not pose a risk to the public living or working near the site during the actual remediation activities. Chemicals of interest included benzene, toluene, ethylbenzene, xylene (BTEX), and polycyclic aromatic hydrocarbons (PAHs).

Our Value: Our risk assessment demonstrated that remediation activities, as planned, were not anticipated to be a risk at the offsite locations.  In addition, the calculated fenceline air concentration objectives provided values to which fenceline air sampling concentrations could be compared in order to determine if additional mitigation measures needed to be implemented once remediation at the site began.