Former Agricultural Chemical Facility Site Investigation
Terraphase has undertaken a comprehensive, multi-year environmental investigation at a former agricultural chemical distribution facility in Southern California. Site contamination linked to historical operations was first assessed in the late 1980s. Since then, the investigation has evolved significantly through multiple phases conducted by Terraphase, resulting in identifying residual contaminant sources critical to informing the design of appropriate remedial strategies.
Scope of Services
To date, Terraphase has advanced over 50 soil borings, installed 27 dual-nested soil-vapor probes, collected over 50 grab groundwater samples, installed sub-slab soil-vapor probes, and conducted indoor air sampling. These activities focused on characterizing impacts from 1,2-dichloropropane (1,2-DCP), 1,3-dichloropropene (1,3-DCP), ethylene dibromide (EDB or 1,2-DBA), methyl bromide, and 1,2,3-trichloropropane (1,2,3-TCP).
Notable Accomplishments
- Multi-media investigation of agricultural-related chemicals of concern at a legacy site, particularly 1,2,3-TCP, which has a California’s maximum contaminant level in groundwater of 5 parts per trillion
- Characterized new, formerly unknown, residual source areas to inform remedial design and implementation
Post-Fire Site Investigation and Risk Assessment
A total of 31 structures were destroyed in the Santa Monica Mountains National Recreation Area (SAMO) during the California Woolsey Fire in November 2018. The structures were located in the nine areas within the SAMO (i.e., Paramount Ranch, Peter Strauss Ranch, Rocky Oaks, Cooper/Brown, Arroyo Sequit, Circle X Ranch, Morrison Ranch, Miller Property, and the Dragon Property). Terraphase was contracted to provide environmental consulting services and oversight of fire debris cleanup by Lead Builders, Inc. (LBI), working directly for the National Park Service (NPS).
Scope of Services
Terraphase prepared a Sampling and Analysis Plan (SAP) to characterize ash and soil following the Woolsey Fire in the Santa Monica Mountains and to implement a Time Critical Removal Action (TCRA) to mitigate human and ecological exposure to burned building debris, ash and impacted soil. To support decisions on removal of fire debris and impacted soil, Terraphase collected samples of ash and soil in nine burned areas. The Terraphase data visualization and management team supported the Woolsey Fire Time Critical Response Action with data management, ash and soil data tabulation and mapping, data screening, statistical analysis, and data validation.
Specific to the ash and soil characterization at the site, our team prepared site maps using GPS data and prepared and managed a project specific database to collect and analyze all of ash and soil data including preparation of data tables and data outputs to support data characterization and human and ecological risk assessment activities.
Based on the data collected, Terraphase developed risk-based human health and ecological remediation goals (RGs) for soil. The risk based screening levels were used to select soil removal areas for the TCRA. Following implementation of the TCRA, Terraphase collected confirmation soil samples at the nine impacted areas to evaluate removal of soil above RGs. The RGs were used along with naturally occurring site-specific background concentrations to evaluate the results of post-cleanup confirmation soil samples following fire debris removal.
Notable Accomplishments
- GPS data collection, expedited sampling and risk assessment, and ArcGIS mapping of sampling over large areas to expedite recovery planning and implementation
City of Torrance Airport and Commercial Property Site Investigations
Terraphase was engaged by the city of Torrance in California to investigate soil, soil vapor, and groundwater impacted with chlorinated volatile organic compounds (CVOCs) at a large commercial site in Southern California. The site had a long history of industrial operations, including large-scale degreasing processes at multiple locations.
Scope of Services
Terraphase developed and implemented a focused soil, soil vapor, and perched and regional groundwater investigation to characterize and delineate the nature and extent of trichloroethene (TCE), tetrachloroethene (PCE), 1,1,1-trichloroethane (1,1,1-TCA), and 1,1-dichloroethene (1,1-DCE) impacts from past industrial operations. The project included advancement of soil borings, installation of monitoring wells and multi-depth soil-vapor probes, and coordination with key stakeholders, including multiple commercial tenants, the Federal Aviation Administration (FAA), and airport management, due to some investigation work in proximity to active runways.
The investigation involved advancing over 60 soil borings—many exceeding depths of 100 feet below ground surface—using a membrane interface hydraulic profiling tool (MIHPT) tool to characterize soil and groundwater impacts. Additionally, 14 multi-depth soil-vapor probes were advanced to 85 feet below ground surface, with over 60 soil-vapor samples collected. The investigation included the collection of 40 grab-groundwater samples, and the installation of 8 groundwater monitoring wells. Several of the investigated areas were on airport property, requiring runway closure and night work. The investigations were performed to more precisely define the extent of CVOC impacts; design remedies for soil, soil vapor, and perched and regional groundwater; and support the development of removal and remedial action work plans.
Notable Accomplishments
- Advanced 60 borings across commercial and airport properties, while navigating tenant, regulatory, and airport requirements
- Employed state-of-the-art techniques for sample collection
- Collected quality data in challenging work conditions
- Generated a large dataset to support removal action and remedial action planning
