Toluene Spill in Kirby, Pennsylvania
In December 2004, a tanker truck ran off the hilly terrain of I-79 near the town of Kirby, Pennsylvania. After heading down the steep embankment, the truck landed approximately 80 feet below the highway, immediately south of the Kirby interchange. The tanker released over 2,000 gallons of pure toluene, a component of gasoline, which caused soil and groundwater contamination on the slope. The spill also impacted Whiteley Creek, located at the base of the embankment.
The slope of the hill was a PennDOT right-of-way property, while the access area was private land, adjacent to state game lands. The project required coordinating with the owners of the properties, as well as the Pennsylvania Department of Environmental Protection, the trucking company, and it’s insurance provider. Physical access to the site was difficult, and required building haul roads and a temporary bridge over Whiteley Creek that could withstand heavy equipment.
A portion of Whitely Creek was dammed and the contaminated shore was dug out with a bucket. Following confirmation sampling, the material was replaced with clean riprap. A berm was then placed along the creek to protect it from remediation activities on the hillslope.
More than just a steep slope, the impacted area contained engineered and compacted fill to support PennDOT’s exit ramp, as well as a wing wall for an approximately 20 foot tall culvert that routes Whiteley Creek under I-79.
Better Solutions, Better Results
The trucking company initially chose soil vapor extraction (SVE) as the remediation method due to concerns about the possible failure of the steep slope during excavation. Instead, Hard Hat developed a solution to the slope stability problem that allowed excavation and on-site ex-site treatment, which accomplished the remediation much faster and with greater certainty than the proposed SVE system.
The first step required the area’s steep slope to be stabilized. This involved a thorough geotechnical investigation and the design of a mechanical stabilization system. Impacted soil was removed using bench cuts to maintain slope integrity. A top-down shoring system was designed. The shoring wall was constructed in five foot sections as the soil was excavated, secured with 40-60 foot soil nails placed horizontally into the embankment to anchor the wall. Excavation of the contaminated soil also required removal of the existing impacted fill soils above the water table in conjunction with the shoring system.
An on-site thermal soil treatment made the project even more demanding. Because pure toluene falls into hazardous waste category U220, soil could not be hauled away; instead, approximately 3,000 cubic yards of soil were treated on site with a thermal desorption remedy.
To address groundwater contamination, a pump and treat system with an air stripper was used to transfer toluene to the vapor phase, followed by treatment of the vapor stream before discharge. Approximately 134,000 gallons of groundwater were removed and treated using this system.
The site was backfilled and restored following the completion of all remediation activities. Treated soil and structural fill were used to cover the shoring wall and replace the slope. The entire area was then seeded and mulched to restore a natural look to the hill.
A benefit to the client was that post remediation sampling was reduced from 2 years to 1 year due to continual low groundwater sample results during remediation. After this period the wells were abandoned in accordance with Pennsylvania regulations.
Due to their ability to demonstrate compliance with remediation standards, the client received a Pennsylvania Department of Environmental Protection Act 2 Release of Liability, relieving the client of concerns for further remediation of the site.