The Cupertino Union School District (District) proposed to purchase a 1.48-acre property adjacent to the Sedgewick Elementary School for a school expansion project (not to result in the addition of classrooms or students to the existing school). The expansion site was the subject of a cleanup program conducted under the oversight of the California Department of Toxic Substances Control (DTSC) School Property Evaluation and Cleanup Division.
A Phase I Environmental Site Assessment and Preliminary Soil Quality Evaluation was prepared for the subject site in 2014 and identified the following facts. Historic and existing uses of the site included residential and orchard. An underground storage tank (UST) was removed from the site in 1996. Concentrations of chlordane (an organochlorine pesticide) and lead above the United States Environmental Protection Agency Region 9 residential screening level (RSL) were identified in soil around the perimeter of existing building structures. Total petroleum hydrocarbons gasoline (TPHg), ethylbenzene and xylenes above the RSL were identified in soil at a depth of 12 feet below ground surface at the location of the previously removed UST.
Padre was retained by the District to prepare a Preliminary Site Assessment (PEA) Workplan (2015). The purpose of the PEA was to establish whether a release or potential release of hazardous substances which pose a threat to human health exists at the subject site. The PEA included review of existing records; discussion of findings; execution of a conceptual site model to identify the complete exposure pathways for the screening level evaluation of chronic health risk; and preparation of a plan (including detailed field and laboratory procedures) for the implementation of further soil sampling and soil gas sampling and evaluation at the site. The PEA was approved by the DTSC in June 2015.
Padre prepared a Technical Memorandum on behalf of the District outlining revisions to the PEA field sampling plan due to revisions to the screening level adopted by the DTSC for Chlordane in October 2015. A Supplemental Site Investigation (SSI) Summary Report was also prepared in accordance with above referenced memorandum and submitted to the DTSC.
On behalf of the District Padre prepared a Removal Action Workplan (RAW) in 2018 that was based upon the results of the Final PEA, the SSI and RAW scoping meeting held with the DTSC. Among other elements, the RAW identified the nature, source and extent of contaminants at the site; provided a risk evaluation and preliminary cleanup goals, and included an engineering evaluation, identification and evaluation of removal action alternatives, and a plan for removal action implementation. The recommended remedy for the subject site was excavation, transport and off-site disposal of soil containing elevated levels of chlordane and lead. After completion of removal action, it was proposed that the site would be regraded and restored to meet the needs of the final school design.
The RAW was implemented in October 2018 and approximately 215 cubic-yards of pesticide and lead-containing soil was excavated and temporarily stockpiled pending waste characterization. The stockpiled soil was classified as a non-hazardous waste solid and transported to Republic Services, Inc. Newby Island Landfill Facility located in Milpitas, Santa Clara County, California.
In 2019, Padre prepared a Removal Action Completion Report (RACR) that detailed the removal action and concluded that post-removal action conditions of the subject site do not pose a significant threat to human health or the environment. The DTSC approved the RACR and certified that all response actions have been completed and further removal/remedial actions are not necessary for the subject site.
Public outreach by the DTSC was conducted throughout the site evaluation, planning and removal action process. The outreach was performed to inform the public about the site and cleanup activities and to provide the public an opportunity to be involved in the DTSC’s decision-making process. Technical documents prepared by Padre served as one of the information sources used during this process.