Former Gas Station
Project Year
2016
Project Duration
5 months
Contaminants of Concern
Remediation Technologies Used
- • In-Situ Chemical Oxidation (ISCO)
- • Direct Push Injection
- • Multi-Phase Treatment
Key Results
- ✓Over 90% BTEX reduction achieved
- ✓TPH levels below action levels
- ✓Dissolved phase petroleum effectively destroyed
- ✓Site achieved regulatory closure
- ✓Property redevelopment enabled
Target Contaminants
Site Background
This former gas station site in northwest Pennsylvania experienced petroleum releases from underground storage tanks (USTs) that resulted in significant soil and groundwater contamination with BTEX compounds and total petroleum hydrocarbons (TPH).
The contamination threatened nearby receptors and required prompt remediation to achieve regulatory compliance.
Remediation Strategy
IET implemented an in-situ chemical oxidation (ISCO) program specifically designed for petroleum hydrocarbon contamination. The strategy included:
- Advanced oxidation chemistry for rapid petroleum destruction
- Multi-phase injection approach to address residual contamination
- Strategic targeting of source zones and dissolved plume
- Treatment of both vadose and saturated zones
Implementation
The ISCO program was executed using direct-push injection technology to deliver oxidation reagents throughout the contaminated zones. Multiple injection points were installed to ensure comprehensive coverage of the treatment area.
IET's experienced field crew completed the work efficiently while maintaining strict safety protocols and minimizing site disruption.
Results
The chemical oxidation treatment achieved excellent results:
- BTEX concentrations reduced by over 90%
- TPH levels decreased below action levels
- Dissolved phase petroleum effectively destroyed
- Site achieved regulatory closure requirements
- Property redevelopment enabled
Technical Approach & Petroleum ISCO Chemistry
This former gas station site in northwestern Pennsylvania required in-situ chemical oxidation (ISCO) to address petroleum hydrocarbon contamination from underground storage tank (UST) releases. IET's ISCO program for petroleum sites typically utilizes activated persulfate, catalyzed hydrogen peroxide (Fenton's reagent), or a combination of both — selected based on contaminant type, soil conditions, and treatment timeline requirements. Persulfate generates sulfate radicals effective against BTEX and TPH, while hydrogen peroxide generates hydroxyl radicals that rapidly destroy petroleum hydrocarbons.
The multi-phase injection approach — delivering oxidants in multiple treatment events — addresses the challenge of residual contamination that persists after the initial oxidation pulse. Petroleum sites often have residual NAPL in soil pores that slowly desorbs into groundwater over time. Multiple injection phases allow the oxidant to destroy this re-dissolving contamination as it enters the dissolved phase, achieving more complete treatment than a single high-dose injection.
Direct-push injection technology was used to deliver the oxidants throughout the contaminated zones — targeting both the vadose zone (where residual petroleum mass resides in soil pores above the water table) and the saturated zone (where dissolved-phase contamination migrates with groundwater flow). The 90%+ BTEX reduction and TPH reduction below action levels enabled regulatory closure and property redevelopment, demonstrating the effectiveness of ISCO for former gas station site closure.
Erie Site Context & Northwestern Pennsylvania Geology
The Erie, Pennsylvania area is located in Erie County within the Erie Lobe glaciated plateau physiographic province. The shallow geology consists of Quaternary-age glacial till and lacustrine deposits — predominantly clay, silt, and sand — overlying Devonian-age shale and sandstone bedrock. The glacial deposits create moderate-permeability conditions suitable for in-situ remediation, with a shallow water table typically at 5–15 feet bgs.
Former gas station sites in this region commonly have petroleum contamination from UST releases that migrated through the glacial till into the shallow groundwater. The BTEX and TPH contamination at this site threatened nearby receptors, requiring prompt remediation to achieve regulatory compliance. The ISCO approach — with its rapid treatment timeline and ability to destroy contaminants in place without excavation — is ideal for former gas station sites being redeveloped, as it enables property transaction and reuse without the cost and disruption of soil excavation and disposal.