Études de cas
J.S. Held rachète Shechter & Everett pour développer sa comptabilité judiciaire dans le domaine du droit de la famille en Floride
En savoir plusA multi-tenant industrial site in Torrance, California, consists of six contiguous parcels covering approximately six acres and has been undergoing long-term groundwater monitoring as part of a monitored natural attenuation remediation strategy for chlorinated volatile organic compounds (VOCs). Although groundwater concentrations have decreased substantially from historical levels, low to moderate concentrations of trichloroethene and 1,1-dichloroethene remain, and increasing concentrations had been identified downgradient of the site.
Regulatory review identified additional areas of concern across four parcels, including locations with limited or no soil vapor sampling, historical detections or other suspected occurrences of chlorinated VOCs, and conducting soil vapor extraction without evaluation of adjoining parcels. The Regional Water Quality Control Board (RWQCB), the regulatory agency overseeing site activities, required further evaluation of soil vapor conditions on-site and groundwater impacts off-site.
Our experts coordinated with the Regional Water Quality Control Board (RWQCB) and the City Public Works department, including renewal of access agreements for monitoring wells and continued groundwater sampling, as well as implementation of interim in-situ injection treatment of groundwater down-gradient of the site. We developed and implemented work plans for additional soil vapor assessment and a remedial action plan for groundwater, which received regulatory approval.
Our team conducted a soil vapor investigation that included installing and sampling 45 probes at 19 locations across the site. We installed probes at depths ranging from 5 to 80 feet below ground surface using direct-push and hollow-stem auger drilling methods. Geophysical screening was performed for utility clearance. Soil sampling was performed during drilling to identify lithology and confirm optimal intervals for probe placement.
The soil vapor study identified low concentrations of chlorinated VOCs, with a maximum of approximately 4 µg/L of tetrachloroethene (PCE). Results indicated that the impacted soil vapor did not present an ongoing source for groundwater impacts, but did suggest a potential for vapor intrusion based on the conservative default attenuation factor currently promulgated by the USEPA.
Indoor air sampling performed in conjunction with later phase soil vapor investigations indicated: 1) Indoor air concentrations were below screening levels for ambient air for commercial/industrial land use in all samples and below residential screening levels in all but one sample; and 2) Ratios between soil vapor concentrations and maximum indoor air concentrations indicate the actual site-specific attenuation factor is approximately 30 times less than the default factor. Our team is in the process of negotiation with RWQCB to determine how best to address their lingering concerns so that closure of the vadose zone (site soils) can be achieved.
The approved Interim Remedial Action Plan to address groundwater impacts in the downgradient area was implemented after obtaining a Waste Discharge Requirements (WDR) permit from the RWQCB. The work included installing additional groundwater wells up- and down-gradient of the area of interest, injecting a mixture of micro-granular zero-valent iron and a colloidal activated carbon solution, and conducting quarterly groundwater monitoring to evaluate effects. In addition to RWQCB approvals, City approvals of access agreements, additional well licensing, and a temporary traffic control plan were also necessary.
Two phases of injection have been conducted to date, and preliminary results indicate that the treatment has been successful in the dechlorination of trichloroethene (TCE) and other chlorinated VOCs. Although this treatment has been demonstrated to be effective, discussion of the cost-effectiveness of possible full-scale implementation across the plume width or within a subarea of the plume width is ongoing.
> Environmental Risk and Compliance
Notre équipe fournit des conseils d’experts sur la détection et la réduction du risque en matière environnementale et développe des solutions pour garantir un respect des normes EHS et une supervision indépendante.
> Environmental, Health, and Safety
J.S. Held dispense des services de conseil et d'expertise en matière d'environnement, santé et sécurité, portant notamment sur les dommages environnementaux et leur remédiation, le devoir de diligence environnemental, la transition énergétique, la toxicologie et l'épidémiologie, l'hygiène industrielle, la gestion responsable des produits et la garantie des produits, ainsi que la santé et la sécurité des personnes.
