EA staff designed and supervised a comprehensive soil assessment at a former 343-acre aerospace facility. Soil assessment was performed to investigate former contaminant source areas; to evaluate the potential risk that residual contaminants in soil posed to property users; and to identify areas requiring remediation. Thousands of soil matrix samples were collected and were analyzed for volatile organic compounds (VOCs), semi-VOCs, polynuclear aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), metals, arsenic, organochlorine pesticides, herbicides, and/or petroleum hydrocarbons. Soil vapor assessment included installation and monitoring of hundreds of soil vapor probes and analysis of soil vapor samples for VOCs, the results of which were used to evaluate potential indoor air vapor intrusion. Groundwater assessment was performed to delineate the lateral and vertical extent of contaminants in 13 separate groundwater contaminant plumes (primarily VOCs, petroleum hydrocarbons, and hexavalent chromium). Groundwater assessment was performed to investigate former contaminant source areas; to evaluate the potential risk that residual contaminants in groundwater posed to the environment; and to identify areas requiring remediation. Hundreds of groundwater monitor wells were designed, permitted, constructed, and monitored. Multiple phases of groundwater assessment were performed, with each successive phase informed by and building upon the preceding phases and the groundwater assessment and monitoring results were used to design, construct, and operate multiple groundwater remediation programs/systems.
Emergent Contaminants, Former Aerospace Manufacturing Facilities
Los Angeles County, California
EA provided strategic planning and risk management support, performed regulatory agency negotiations, and prepared work plans and documents for two former aerospace facilities with the potential for per- and polyfluoroalkyl substances (PFAS) contamination in soil and groundwater. The work complied with California Water Code Sections 13267 and 13383 Orders for the Determination of PFAS Substances at Chrome Plating Facilities. EA evaluated and documented historical PFAS use/storage/disposal information; prepared PFAS Use Questionnaires; prepared PFAS Soil and Groundwater Investigation Work Plans; negotiated the scope of the PFAS investigations with the regulatory agency; supervised field investigation activities; and peer reviewed implementation reports.
Vapor Intrusion, Former Aerospace Facility
Los Angeles County, California
EA designed, planned, and is implementing indoor air monitoring in several large commercial/industrial buildings (over 2,000,000 square feet of space) and one day-care building at a former aerospace facility in Los Angeles County, California. EA developed access agreements between the client and multiple property owners and tenants; directed development of and negotiated site-specific indoor air screening levels that were approved by the agencies; prepared indoor air monitoring work plans; directed field implementation of indoor air monitoring activities; directed and supervised risk assessors; evaluated indoor air monitoring data; and peer reviewed technical documents.
Conceptual Site Model and Numerical Modeling, Former Aerospace Facility
Orange County, California
EA staff prepared a detailed conceptual site model and developed a groundwater flow model for a large former aerospace facility in Orange County, California. The conceptual site model and groundwater flow model incorporated complex geologic folding that resulted in groundwater plume transport from near land surface to 1,000 feet below land surface within relatively short distances. The process involved evaluation of lithologic, geophysical, water level, and water quality data using a network of monitor wells ranging in depth from 100 to over 1,000 feet below land surface. The groundwater flow model was used to design a nominal 500 gallon per minute groundwater extraction, treatment, and reinjection system.
Groundwater, Vadose Zone and Surface Water Modeling, Former and Active Industrial Facilities
Southern California
EA staff have prepared multiple vadose zone models in Southern California to develop cleanup levels for halogenated solvents in soil and soil vapor. These models were also used to support post remediation closure at several sites. EA has also prepared integrated groundwater and surface water flow models to assess cleanup strategies using groundwater extraction and treatment as well as in-situ treatment methods to remediate solvents, hexavalent chromium, and 1,4-dioxane. This integrated model considered both inflow and outflow of surface to the groundwater system.
Public Participation and Community Outreach, Former Aerospace Facilities and a Public Water Agency
Southern California
EA staff implemented agency-required public participation activities at former aerospace facilities and for a public water agency in Southern California. EA prepared Public Participation Plans that were approved by the agencies; prepared several Fact Sheets, also referred to as Community Updates, which were mailed to the surrounding communities; developed “Frequently Asked Questions” and Community Surveys that were used to gauge community interest in the projects; prepared notifications for property owners use in communicating environmental programs to their workers and tenants; prepared materials and presented them to site workers and tenants; and prepared and distributed work notices that were provided to individual residents and businesses.
Forensic Investigation, Former Instrument Manufacturing Facility
Orange County, California
EA staff designed a regulatory-agency-approved compound specific isotopic analysis (CSIA) sampling and analysis plan to identify volatile organic compound (VOC) source areas, evaluate commingled plumes and off-site sources, and estimate VOC degradation rates. The work provided a line of evidence supporting a monitored natural attenuation (MNA) program at the site.
