TCE and Heavy Metals Remediation Using Chemical Injections
In 1989, a fire destroyed a chemical distribution warehouse which reportedly contained nearly 100 drums of solvents and plating solutions. Heat from the fire ruptured many drums and the subsequent environmental assessments identified chlorinated solvents (primarily TCE) and dissolved cadmium in groundwater.
ES&M completed a comprehensive site assessment which included testing to evaluate potential remedies. ES&M determined that conditions were favorable for a chemical injection program encouraging reductive dichlorination.
ES&M worked with PeroxyChem to develop a remedial agent that would simultaneously reduce the concentration of both chlorinated solvents and cadmium in groundwater. PeroxyChem’s EHC® series of reagents, a concentrated, buffered, microemulsion of carbon, nutrients, and iron, was applied as both a concentrated slurry and as a more dilute liquid. Included in the formulation was PeroxyChem’s sulfide-based EHC® Metals Remediation Compound to address the dissolved cadmium.
ES&M oversaw the installation of injection boreholes into which the EHC® In-situ chemical reduction (ISCR) Reagent slurry was injected. A total of 3,650 lbs. of granular EHC® was mixed with water to form a pumpable slurry which was injected into thirty-five boreholes. Each borehole was subsequently converted into an injection well. Using a 1,000-gallon reagent tank, the ELS® microemulsion was mixed with water and potassium bicarbonate (KHCO3), the pH buffer solution. The aqueous ELS® solution was pumped from the tank and into the injection wells using a series of diaphragm pumps. A total of 45,000 gallons of ELS® mixture was injected into the thirty-five injection wells.
A series of groundwater monitoring events were completed before, during, and after the injection to assess distribution of reagents in the aquifer, the effectiveness of the reductive dechlorination remedy, and to evaluate when additional reagents may be needed. Groundwater was monitored for pH, oxidation/reduction potential (ORP), temperature, conductivity and dissolved oxygen (DO). After three months, groundwater samples were collected for laboratory analysis and the results demonstrated that the TCE concentrations had been reduced by more than 98% and the dissolved cadmium concentration had been reduced by more than 99%.