Leveraging its environmental expertise, regulatory relationships, and creative problem-solving, Trihydro supported the characterization, remediation, and closure of a power plant. 

Trihydro provided environmental support for the characterization, remediation, and closure of a natural gas and fuel oil power plant. The site is in a high-visibility location and is subject to a Resource Conservation and Recovery Act (RCRA) Corrective Action Consent Agreement, with additional oversight and permitting through multiple state, city, and county agencies. The client sold the property in the late 1990s, but retained responsibility to investigate and remediate impacts from environmental releases that occurred before the property sale. When the project began, the power plant was active so Trihydro coordinated work schedules with the client and the current facility staff to achieve project objectives without impacting the current property owner’s operational, decommissioning, and safety requirements. The Trihydro team worked with local experts to confirm field activities protected cultural resources and sensitive plant and animal species unique to the site location.

In a RCRA Facility Investigation (RFI) Work Plan, Trihydro summarized existing environmental data and addressed data gaps for soil and groundwater. After receiving regulatory approval of the RFI, Trihydro executed a field investigation that included collecting and analyzing more than 700 soil samples and 200 groundwater samples using hand tools and direct-push drilling. The project team reviewed the new data in the context of historical data and site operations to evaluate source-specific and facility-wide environmental conditions. Trihydro identified locations where total petroleum hydrocarbons (TPH) concentrations in soil and groundwater were above the site screening levels. Residual petroleum products beneath former aboveground storage tanks (ASTs) were identified as a potential threat to groundwater quality (through leachate) and environmental receptors. As a cost-effective short-term solution, Trihydro applied an environmentally safe polymer emulsion product across former AST pads to provide a stabilized soil surface that minimized rainfall infiltration and controlled dust and erosion. Trihydro then used a risk-based approach to demonstrate that the residual TPH products do not pose an unacceptable threat to potential receptors or the environment, saving the client $700,000 in soil removal costs by obtaining regulatory concurrence that remediation was not necessary.

Following the RFI investigation and discussion with regulators, Trihydro managed a groundwater monitoring program to evaluate detections of TPH and metals in site groundwater. Through a continuous data review process and collaboration with regulators, Trihydro negotiated reductions in the number of sample locations, analytical suite, and sampling frequency to reduce costs to the client and focus the path to site closure. Trihydro completed an RFI data gap investigation to address remaining questions about TPH in soil and groundwater, and supported conceptual site model (CSM) development to complete the RCRA RFI phase. The project team deactivated19 groundwater monitoring wells after demonstrating to regulators that the wells were no longer needed for the site groundwater monitoring program.

To achieve closure on the facility’s off-site tank farm, which was under county oversight, Trihydro worked with the client and state regulators to establish a collaborative Voluntary Cleanup Agreement (VCA) under which the county would defer data and risk assessment review to state regulators. Trihydro removed a soil hotspot impacted with TPH and metals, then completed a human health and ecological risk assessment that documented no unacceptable risks to potential receptors. Regulators accepted the risk assessment, which allowed for the termination of the VCA and closure of the tank farm by the county. 

Collaboration with the regulatory community led to expedited project approvals and cost savings for the client. 

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