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A Risk assessment CASE STUDY
Human Health and explosion risk mitigation


    Snyder Geologic assisted Hensel Phelps Construction Company (HPCC) and HM Pitt with management of environmental issues related to the reconstruction and expansion of the San Ysidro Land Port of Entry (SYLPOE), the busiest land border crossing the world, between San Diego, California and Tijuana, Mexico.

For one task at the project site, where a new Pedestrian Walkway for the border crossing was being constructed, a new storm sewer and manhole was being constructed. Due to high levels of hydrocarbons, a large excavation was required to remove hazardous levels of hydrocarbon-impacted soil. In addition to the removal, we conducted a health risk assessment of hydrocarbon vapors that could potentially present a health risk to future site workers required to access the manhole. A potentially explosive atmosphere evaluation was also performed to ensure that after remedial excavation any remaining hydrocarbon vapors would not accumulate in the manhole or sewer pipeline that could ignite.

Based on the vapor risk calculations, we developed an excavation strategy to remove a sufficient amount of soil that would mitigate both health risks and risks of explosion, but which would also minimize the cost of waste disposal, saving the project hundreds of thousands of dollars.