Madison Former Gas Station
At a former gas station in Madison, New Jersey, in situ remediation was applied to address petroleum hydrocarbon source mass within the subsurface smear and saturated zones. Excavation of gasoline and fuel oil underground tanks (USTs) along with the associated piping and shallow hydrocarbon soil impacts had previously been completed.
However, excavation was impacted due to accessibility limitations from the service center building and road. Following excavation and enhanced fluid recovery activities, residual benzene, toluene, ethylbenzene, xylene (BTEX), trimethylbenzene (TMB), and light non-aqueous phase liquid (LNAPL) impacts remained.
The primary area of concern was approximately 1,500 sq ft with a 15-ft vertical target interval from approximately 25 to 40 feet below ground surface (bgs). The geology at the site is dense silt and clay with depth to groundwater at 30 ft bgs.
A total of 13,300 lbs of Provect-OX were applied via 20 temporary direct push injection locations to treat the area of concern and two impacted monitoring wells.
The service center remained open and active during drilling and injection activities, demonstrating the non-intrusive nature of the technology.
Provect-OX rapidly oxidizes the organic contaminants present in soil and groundwater and provides long-term, sustained secondary bioremediation to manage residuals and prevent contaminant rebound. This is accomplished by using ferric iron (Fe III) as a safe and effective means of activating persulfate, which quickly yields sulfate and ferrate radicals for chemical oxidation treatment.
A pH buffer is also pre-blended with the Provect-OX to offset any post-injection acidic pH conditions that are normally observed with traditional persulfate applications.
Following the Provect-OX application, petroleum hydrocarbon groundwater concentrations have significantly decreased over a 2-year monitoring period.
MW-6R Results:
- Ethylbenzene: 68.8% reduction (2,510 to 784 μg/L)
- Total Xylenes: 89.5% reduction (5,910 to 621 μg/L)
- Toluene: 99.9% reduction (1,790 to 2.5 μg/L)
- 1,2,4-Trimethylbenzene: 99.0% reduction (5,460 to 56.6 μg/L)
MW-9 Results:
- Benzene: 88.0% reduction (29.7 to 3.56 μg/L)
- Ethylbenzene: 92.8% reduction (1,590 to 115 μg/L)
- Total Xylenes: 98.7% reduction (6,280 to 84.2 μg/L)
- Toluene: 99.3% reduction (7,680 to 53.3 μg/L)
- LNAPL completely eliminated
Chemical oxidative conditions were evident immediately post-treatment with increased ORPs (+354 mV and +32.6 mV). By 3 months post-injection, ORPs in both wells were negative, indicating transition to a reducing environment conducive to enhanced bioremediation.