Derek Pizarro, CPG

Gasoline Tanker Truck Rollover Remediated Using qHRSC and an Activated Carbon Injectate Permeable Reactive Barrier

Derek Pizarro, CPG, Senior Geologist and Product Manager, AST Environmental, Inc.

SUMMARY :

In 2015, a gasoline transport tanker struck a parked trailer on the shoulder of a rural part of US Route 23, causing a release of up to approximately 4,000 gallons of fuel near major surface water features. The primary challenges were protecting nearby surface water bodies and accessing the areas of contamination due to the presence of a state highway with multiple buried utilities (gas, water, fiber, and other communication lines) and surrounded by thick-forested residential properties. Initial response activities included soil excavation, resulting in removal of approximately 1,100 tons of soil impacted with petroleum hydrocarbons (PHCs). Subsequent installation and sampling of groundwater monitoring wells indicated contaminant plume expansion. Two phases of work were performed to facilitate the primary objective of the remedial effort- reduce LNAPL saturation and enhance the reduction of petroleum hydrocarbon mass.    In 2017, the first phase consisted of updating and revising the existing (post-excavation) Conceptual Site Model (CSM), which focused on a remedial design characterization (RDC) event using quantified high resolution site characterization (qHRSC) data. qHRSC is a combination of HRSC and quantifiable soil and groundwater data (physical samples). The second phase was completed in 2018, involving the installation of a series of six BOS 200® permeable reactive barriers (PRBs) to capture and treat LNAPL and PHC impacts within the saturated soil and groundwater plume. This was accomplished by injecting an adsorption platform of activated carbon (AC) coupled with AC-enhanced microbial degradation that could manage the LNAPL in the short term, while allowing continued, long-term treatment of dissolved phase mass utilizing the BOS 200 biological processes.    

APPROACH:

The RDC data were instrumental in the development of a quantitative CSM for the LNAPL source and solute plume. The qHRSC data determined that LNAPL level contaminant mass remained under the highway, sorbed into a natural peat layer. The RDC included the installation of 21 soil borings with samples collected every 2 vertical feet, plus 10 temporary monitoring wells to supplement the groundwater data from 14 existing wells. The RDC also included refinement of the hydraulic conductivity and groundwater gradient via rising- and falling-head slug tests in seven of the existing monitoring wells. Full-scale remediation involved injection of 42,700 lbs. of BOS 200 and 30,800 lbs. of a terminal electron acceptors (TEAs) formula across 665 injection points using direct push technologies (DPT). Angled DPT injections were used along both sides of the highway to target mass residing beneath it.     

RESULTS:  

Performance monitoring over more than four years has demonstrated the continued biological degradation of PHCs in groundwater. PHC mass reduction was 94% or greater at 1,700 days post-injection. The series of six PRBs has been sufficiently protective of the nearby surface water bodies. Continued biological degradation of PHC impacted groundwater is apparent in the post-injection performance monitoring data.

Derek Pizarro, CPG is a Senior Geologist and Product Manager for AST Environmental, Inc. and a Certified Professional Geologist (AIPG). He has more than 20 years of experience in environmental applications, specifically contaminant transport studies, heavy metals remediation, permeable reactive barrier (PRB) design, and reagent bench-scale testing and design for environmental projects, industrial facilities, landfill, and utilities clients. Derek has been a technical advisor for the testing and selection of in situ stabilization (ISS) treatment for CERCLA sites, state land recycling programs, and privately funded cleanups. 

Prior to AST, Derek served as General Manager and Environmental Products Director for a chemical manufacturing company. He is a technical board member for the Global EnviroSummit Conference, board member for EnviroClass, and formerly served on the American Foundry Society (AFS) Environmental Health & Safety (EHS) committee.