(225e) Case Study - In-Situ Oxidation of Ground Water Contaminated By Petroleum Hydrocarbons, Acetone and Chlorinated Hydrocarbons At a Former Industrial Facility in Northern California

In-situ treatment of dissolved petroleum hydrocarbons and solvents presents many unique challenges due to variability in the subsurface hydrogeology, pH, and chemistry of the soil and ground water matrix. In addition, the petroleum hydrocarbon contaminants present a suite of chemicals in a variety of carbon chains, alkane lengths, and aromatic structures. Proposed in-situ treatments must be carefully tailored to the subsurface characteristics, land use, site-specific cleanup standards, and time constraints. This presentation describes the design and implementation of in-situ ground water remediation by injecting a mixture of Advanced Oxygen Release Compound (ORC-Advanced®) and Regenox® (a solid alkaline oxidant) to ground water contaminated by petroleum hydrocarbons, acetone, and chlorinated hydrocarbons at a former acetylene gas manufacturing site located in Northern California.

Nine ground water monitoring wells were installed and used to track water quality parameters and ground water contaminant concentrations within the treatment zone during remediation; and up-gradient and down-gradient to the treatment zone. Baseline ground water samples were collected and analyzed to estimate the chemical dosage and design the amendment mixture. The amendment consisted of a mixture of Regenox® for rapid, direct oxidation of contaminants and ORC Advanced®, for slow controlled release of oxidants for long-term bio-stimulation. A total of 10,023 gallons of amendment containing over five tons of oxidant was injected at 45 locations using multiple direct-push drill rigs. Eight quarters of post-treatment ground water monitoring showed that concentrations of all dissolved contaminants in ground water were successfully reduced to below cleanup standards. For example, acetone was reduced from a pre-remediation maximum concentration of 54,000 micrograms per liter (µg/L) to 1,600 µg /L.

Challenges encountered during implementation included surfacing of the injected material that reacted vigorously with naturally occurring carbon and anthropogenic contaminants.  Subsurface conditions varied widely across the treatments area, including the presence of lime sludge and subsurface obstructions such as buried railroad ties, pipelines and concrete slabs. In addition, since site access constraints required that all work be performed on weekends, multiple drill rigs and support vehicles operated within a fairly small area, increasing logistical and safety concerns.