O’Brien & Gere provided expert testimony and litigation support related to human exposure to volatile compounds following a catastrophic gasoline release from a service station.  Inadequate investigation of the magnitude and areal extent of the impacts from the release led to the collection of inadequate and insufficient data to support our clients' position. Because of the extreme data limitations, O’Brien & Gere developed a novel retrospective approach for estimating historical indoor air concentrations of gasoline constituents originating from affected groundwater underlying the impacted homes. Although this approach was considered novel with respect to the science of vapor intrusion at the time and challenged by the opposition, it was subsequently recognized as an acceptable approach by the Court. O’Brien & Gere's efforts resulted in the presentation of supportable exposure scenarios that led to significant financial benefits for the client group.

On a 3 month schedule, O’Brien & Gere developed and executed a work plan to evaluate the extent of a groundwater plume and assess potential impact to indoor air quality.  Some of the tasks and services included work plan development, site investigation, sub-slab and indoor air sampling program, building surveys and inventories, and ground water sampling.

With no disruption to facility operations, O'Brien & Gere designed and constructed a sub-slab depressurization system for a 50, 000 ft² industrial facility. Some of the tasks and services involved were building survey and visual inspection; sub-slab diagnostic testing; mitigation system design; and construction and commissioning.

Over 65 engineers and scientists at O’Brien & Gere worked for more than two years to provide design, construction, and commissioning services associated with the installation of over 500 sub-slab depressurization systems within a 350-acre area.  Other mitigation techniques, such as building pressurization, heat recovery ventilation, trenched systems, were also used where sub-slab depressurization was not feasible. In addition to system installation, O’Brien & Gere has continued to provide operation and maintenance of these systems for over five years. Services included sub-slab diagnostic testing, screening evaluations, mitigation system design, installation and commissioning, air dispersion modeling, ambient air monitoring, data management, operation and maintenance, and value engineering.

O’Brien & Gere developed and executed a vapor intrusion investigation and mitigation program for the largest vapor intrusion site in New Jersey.  The scope of the program included work in an offsite residential area where shallow groundwater is impacted with chlorinated volatile organic constituents.  Investigative activities have consisted of: (1) offsite shallow groundwater sampling to further assess and define the edges of the plume boundary and update the conceptual site model (CSM); (2) pre-mitigation sampling of indoor and ambient air and sub-slab soil gas within the pre-defined vapor mitigation area to further evaluate the vapor pathway and update the CSM; and (3) sub-slab soil gas sampling along the groundwater plume boundary to further define the potential for vapor intrusion and the mitigation area.  To date, more than 1,000 samples have been collected.  Based on an assessment of the data collected during the early phases of the program, installation of sub-slab depressurization systems was offered to property owners in the mitigation area as a proactive interim remedial measure.  Where systems have been installed, the process has involved: (1) diagnostic testing and system design; (2) permitting; (3) system installation and commissioning to assess performance; (4) post-mitigation indoor air sampling; and (5) interim remedial measure reporting.  To date, O’Brien & Gere has designed and installed approximately 250 systems and currently provides routine operation and maintenance of these systems.  O’Brien & Gere has also assisted with public awareness support as part of this project including website design, meetings with property owners, participation at public availability sessions, and preparation of various materials for distribution to the public including fact sheets and mitigation FAQs brochure.

O’Brien & Gere designed and installed a sub-slab depressurization system for an 800,000 ft² manufacturing facility using an innovative and cost saving approach. Through sub-slab diagnostic testing, O’Brien & Gere determined that traditional sub-slab depressurization using conventional saw-cut trenches and vertical risers would be too disruptive and costly for occupants and owners, respectively. Utilizing horizontal well techniques, 540 linear feet of specially designed perforated piping was installed beneath the slab and coupled to a regenerative blower. Post-installation commissioning indicated that approximately 60% of the building’s footprint was successfully depressurized. Moreover, indoor air concentrations within the workspace have dropped by more than 90%, and are now compliant with TCE air guidline values established by the New York State Department of Health.