New York Brownfield Cleanup Program Investigation and Remediation

Terraphase is providing Licensed Professional Engineering services at a site enrolled in the New York State Department of Environmental Conservation (NYSDEC) Brownfield Cleanup Program (BCP), governed by 6 NYCRR Part 375. The site has a history of sheet metal working and manufacturing operations.

Scope of Services

Terraphase prepared and implemented a Remedial Investigation Work Plan to delineate and characterize the nature and extent of contamination at the Site. The remedial investigation revealed petroleum hydrocarbon impacts to soil and groundwater from an on-site underground storage tank (UST), as well as chlorinated volatile organic compound (CVOC) impacts to sub-slab soil vapor.

Based on the investigation results, Terraphase evaluated remedial alternatives and developed a remedial design, which was presented in an Interim Remedial Measure Work Plan approved by NYSDEC.

Notable Accomplishments

• Designed and completed hot-spot excavation and off-site disposal of UST and impacted soil, with field screening during excavation
• Implemented an in-situ chemical oxidation program using activated sodium persulfate to address elevated total petroleum hydrocarbons, benzene, toluene, ethylbenzene, and xylene levels, with a follow-up application of liquid carbon for adsorption and bioremediation support
• Designed and installed a sub-slab depressurization system compliant with New York City Building Codes, incorporating vertical suction pits, horizontal extraction piping, and rooftop inline blowers to mitigate CVOCs in sub-slab vapor

Kansas Legacy Site Investigation and Closure Services

Terraphase was initially engaged to conduct a third-party desktop review of a legacy chlorinated solvent site in Kansas. The site, which had undergone multiple investigation phases over two decades, is currently occupied by an aircraft parts manufacturing facility adjacent to a private airport. The review marked the beginning of a 5-year effort to fully characterize the site and pursue regulatory closure through the Kansas Department of Health & Environment (KDHE) Voluntary Cleanup Program.

Scope of Services

Terraphase completed comprehensive horizontal and vertical delineation of volatile organic compounds (VOCs), revised the conceptual site model (CSM), and conducted a plume stability analysis. These efforts advanced the site’s regulatory status and positioned it for closure. To address contamination in the source area, Terraphase implemented a combined remedy approach using zero-valent iron (ZVI) for chemical reduction and in-situ bioremediation (ISB). The treatment process included hydraulic fracturing to enhance ZVI distribution and co-injection of bioremediation amendments to effectively shrink the VOC plume and meet KDHE’s “No Further Action” criteria.

Notable Accomplishments

• Completed full site characterization and reconceptualized the CSM
• Conducted plume stability analysis to support regulatory decision-making
• Advanced site toward closure under the KDHE Voluntary Cleanup Program
• Implemented innovative ZVI and ISB remedy with hydraulic fracturing
• Achieved significant VOC reduction in the source area
• Positioned site to receive a No Further Action designation from KDHE

Former Gasoline and Automotive Station Investigation and Remediation

Terraphase was engaged to take over environmental activities at a long-vacant former gasoline and automotive service station in Northern California that had been stalled in regulatory oversight. The site has multiple underground storage tanks (USTs) and associated piping. The property is now being redeveloped into a low-income apartment complex.

Scope of Services

Terraphase assumed responsibility for regulatory communication with the local oversight agency, conducted additional site characterization, and developed an updated conceptual site model (CSM). A revised remedial strategy was proposed and approved, including the use of a proprietary vapor suppressant and hydroseed to minimize odor impacts to nearby residential areas.

Terraphase managed the public notice process, contractor selection, and on-site remediation activities, including the excavation of approximately 9,700 tons of total petroleum hydrocarbon (TPH) and lead-impacted soil and removal of legacy piping. Following the remediation activities, soil-gas monitoring wells were installed to evaluate vapor intrusion risk. Terraphase also designed and oversaw the installation of a passive vapor intrusion mitigation system (VIMS), as required due to the presence of a regional tetrachloroethylene (PCE) plume, and supported the client in securing city planning and building approvals.

Notable Accomplishments

• Progressed site closure process that was stalled in regulatory oversight and secured regulatory agency approval for a revised remedial plan
• Excavated ~9,700 tons of TPH- and lead-impacted soil
• Designed and implemented a passive VIMS to address vapor intrusion risks
• Minimized community odor impacts with an innovative vapor suppressant and hydroseed application
• Supported the client in obtaining city planning and building department approvals for apartment complex development