continued Human Health Risk
Human health risk involves the exposure to potentially toxic contaminant and duration of exposure. While the petroleum plume from the tank farm has been largely remediated, the potential risk from residual contaminants in the groundwater and potentially from residual vapors in the soil still exists. Based on publicly available records, it appears that soil vapor studies for health risk have yet to be undertaken at the site.
Regardless of the results of such studies, engineering controls are available to protect users of the site. However, with regard the soil contaminants, whether they are pesticides, metals, burn ash by-products or something else, the reuse of that soil will need careful consideration if it is to be used close to the ground surface for open space, parks and greenways so that the public and maintenance workers are not exposed.
Risk to Environment
The creation of open space and parks within the flood zone means the potential for these contaminants to be present. The location of any soil re-use relative to the river will be important. Once the soil is no longer capped by the parking lot, rain and irrigation can mobilize any contaminants toward the river.
Handling of the Soil
It’s been said that the SDSU plan will keep all the excavated soil on the site, which is a smart way to save money. However, if significant concentrations of contaminants are widespread from the historical land uses, management of how the soil is handled and where it is reused will be important.
Soil with concentrations of contaminants above certain levels will not be allowed for use as fill soil and will require appropriate disposal off-site. Due to the petroleum plume, if dewatering is required for any part of the project, the groundwater extracted will likely require treatment prior to discharge.
A site-wide evaluation of these issues with potential contaminants and how it all fits in with the proposed grading and construction plans should be undertaken. This is the approach that was successfully implemented when I managed the assessment and remediation of the 19 city blocks of the Petco Park and East Village redevelopment project.
Everyone plans for the obvious issues; the trick is to understand the hidden ones and how to best handle the unknowns. Too many times developers choose to limit the effort they put into the assessments up-front.
On projects of this scale, that can have a disastrous outcome to the projects budget and schedule. With a solid assessment and plan, remediation costs can be minimized and schedules can be protected.
Chris Spengler is Principal of C. Spengler Strategies, a construction and environmental consulting firm.