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Preliminary Endangerment Assessment

Mission Hills High School, San Marcos, CA

Client:  San Marcos Unified School District

TGI performed a Preliminary Endangerment Assessment for the site of a proposed high school on a 45-acre property in San Marcos, California.  The work was performed pursuant to the requirements of AB387/SB162 with oversight from the California EPA/Department of Toxic Substances Control (DTSC).
Much of the site was cultivated with row crops and/or vineyards from the mid-1940’s through mid-1950’s, indicating the potential for the presence of pesticides and herbicides.  From 1958 to late 1999, the property has been used as part of a dairy farm.  Waste streams and potential contaminants related to the recent dairy operation include animal manure and urine, milking barn washwater, equipment cleaning solvents and acids, and petroleum hydrocarbons.  The dairy operation may also use or have used other compounds such as pesticides, and herbicides.  The site is adjacent to other portions of the dairy facility that may also have discharges that have impacted the site. 
The primary contaminants of concern at the site are animal wastes (nitrates, nitrites, ammonia and biological pathogens), operations wastes (waste oils, anti-freeze, solvents, acids and associated chemicals), and residential wastes (PCB’s, asbestos, lead paint and septic effluent). 
TGI performed an extensive sampling and analysis program to evaluate the potential presence of chemical constituents in surface water, sediment, surface soils, subsurface soils, and groundwater beneath the site.  Based upon the sampling results, a human health and ecological screening evaluation was performed in accordance with the protocols detailed in the DTSC PEA Guidance Manual. 
A public participation Community Profile was prepared to establish the procedures and protocols for informing the community surrounding the site of the PEA investigation. 


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