Remedial/Mitigation Evaluations and Design

Orange County, California

EA constructed and calibrated a groundwater flow model for an area covering greater than 30 square miles. The groundwater flow model was calibrated to transient conditions representative of the low and high potentiometric cycles observed in area monitoring wells. The model also incorporated historical and ongoing source site remedial system groundwater extraction.  The calibrated model was used to simulate groundwater extraction alternatives to address operable unit groundwater contamination within a shallow aquifer system. The simulations included disposal of extracted water (following treatment) via injection into deeper portions of the shallow aquifer system.  The calibrated groundwater flow model was also used to estimate horizontal groundwater flux rates to assess potential dosing of in-situ chemical oxidation.

Orange County, California

EA prepared Feasibility Study (FS) documents to evaluate and screen remedial technologies and process options that were retained for the development of remedial alternatives to address groundwater contamination in an Operable Unit in Orange County, California. The retained remedial alternatives were further evaluated in detail as part of the FS, which is being conducted in cooperation with California state agencies to develop an interim remedy for Operable Unit groundwater contamination. The FS included evaluation and designation of chemicals of concern (COCs); evaluation of the potential human health and ecological risks to groundwater and surface water; identification, evaluation, and screening of General Response Actions, Remedial Technologies, and Process Options; and development of Remedial Alternatives and groundwater discharge end use options.

Orange County, California

EA staff designed, permitted, constructed and performed operations and maintenance (O&M) of a soil vapor extraction (SVE) system to remediate solvent-contaminated soil (primarily spent TCE) from a former leaking RCRA-permitted underground storage tank (UST). The SVE system was operated and continues to operate to contain potential indoor-air vapor intrusion of solvents into overlying medical services buildings. EA successfully obtained the Cal-EPA Department of Toxic Substances Control (DTSC) Environmental Indicator (EI) Program designation “Under Control” on a timeline desired and established by the DTSC. EA staff also designed, permitted, constructed, and performed O&M of a groundwater EISB remedy for solvents in groundwater, which included installation of over 100 injection wells, and periodic injection of food-grade soybean oil and microorganisms known to enhance reductive dechlorination of volatile organic compounds (VOCs).

Los Angeles County, California

EA staff provides peer review of technical documents; has developed and continues to refine strategic planning and remediation programs, and prepares work plans and USEPA deliverables for ongoing soil and groundwater remediation at a Superfund Site in Los Angeles County, California. Soil contaminated with solvents (principally PCE) was remediated or is being remediated using soil vapor extraction (SVE), and dual-phase extraction (DPE). Groundwater containment using groundwater extraction and treatment (GET) is ongoing. EA is currently permitting and designing the GET and will oversee construction of a full-scale GET system remedy including seven large-diameter extraction wells (1,000 gallons per minute estimated total extraction); collection piping; a groundwater treatment facility; disposal piping; a surface water end use discharge structure; and an optional sewer/storm drain end use option for periods when surface water discharge is unavailable.

Los Angeles County, California

EA staff prepared a detailed evaluation of treated groundwater end uses to assess the risks associated and requirements for a large groundwater extraction and treatment system in an adjudicated groundwater basin. The alternatives included reinjection into shallow and/or deep aquifer systems, use in existing water reclamation systems, infiltration, and surface water discharge. EA engaged multiple permitting agencies to outline treatment requirements and reached out to partnering entities to maximize preservation of the water resource and minimize treatment system downtime due to end use constraints.

Southern California

EA staff assessed vapor intrusion potential into large multi-tenant commercial buildings and prepared a mitigation plan that included maintaining positive building pressure and integrating a soil remediation system to reduce vapor intrusion of halogenated volatile organic compounds into indoor air. The soil remediation system was implemented under existing structures by installing vapor extraction wells inside and around the perimeter of the building. The system was operated successfully and was subject to vapor and indoor air monitoring for several years after which closure with land use controls was attained.