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Utility Right of Way Risk Assessment
A risk assessment was performed on a former underground storage tank (UST) site under the Pennsylvania Storage Tank and Spill Prevention Act (Act 32). The site had been utilized as an automobile service garage and retail gasoline fueling facility from the 1920s to the present. The risk assessment evaluated on-site impacts for both current and future use (i.e. potential residential use) and off-site impacts in various right-of-ways (ROW) near the site, including the ROW adjacent to the on-site property. This summary focuses on the ROW analysis adjacent to the site.
Based on an evaluation of the analytical soil and groundwater data utilized for the ROW adjacent to the site, more constituents of interest (COI) and higher concentrations were observed towards the northern end of the street, and less COI/lower concentrations were observed towards the southern end of the street. Therefore, in order to reduce the potential need to restrict access along the entire ROW adjacent to the site, the ROW was conceptually divided into 3 segments (i.e. Segment 1, Segment 2, and Segment 3) to account for the variation of impacts. Construction worker and utility worker scenarios were developed for the entire ROW through a refined conceptual model process. Because of how the data were distributed within the subsurface, both vertically and horizontally, soil and groundwater exposure pathways were retained for Segment 1 (northern end of street), and only groundwater exposure pathways were retained for Segments 2 and 3 (central and southern end of street). In addition, the exposure point concentrations were estimated differently for each segment to account for the segment-specific conceptual approach. Consequently, the three segments were quantitatively evaluated separately for the construction and utility worker. It was assumed these receptors would spend an equal amount of time in each segment and, therefore, some of the exposure parameters were equally divided into three. Once the risk and hazard indices were calculated for each segment, they were added to estimate the total risk and hazard index for the construction worker and the utility worker for the entire ROW. By evaluating the ROW in this manner, this reduced the potential need for restricting the entire ROW and reduced the potential need to mitigate the entire ROW.