Highway Rest Stop — Bowmansville

The subject site is an active rest-stop along a major Pennsylvania highway. The site has been impacted by the historic release of petroleum fluids. The contaminants of concern are petroleum hydrocarbons, such as benzene and toluene.

The in-situ injection program targeted these compounds with 27 injections using synergistic catalyzed reactions and long lasting (via persulfate) oxidation. Injections occurred between 10 and 18 feet below ground surface over a span of 2 days in September 2007. The geology of the site is combination of silt and sand.

The remedial approach utilized both free radical chemistry, oxidation chemistry and facultative biological oxidation in such a way as to extend the oxidant and free radical residuals while enhancing the in-situ environment such that it was suitable for biologically based attenuation.

IET applied three remedial materials to the subsurface via a patented injection process and apparatus (US Patent 7,044,152) such that the oxidation reactions occurred in a controlled manner. In a unique application of zero-valent iron metal, IET activated both the persulfate and the peroxide species in-situ, allowing for both the oxidation and biological remedial processes to occur via a single injection event.

The premise of the approach is based on the utilization of oxidizing species and their by-products. The first phase, the oxidation event, chemically oxidizes the majority of dissolved and sorbed targeted compounds. Once the oxidants are exhausted, the ferric iron and sulfate species allow for the biological attenuation phase.

The groundwater results from the five monitoring wells within the injection area showed large reductions in petroleum hydrocarbons.

This Bowmansville project demonstrates IET's patented (US 7,044,152) dual-phase treatment technology — using ZVI to simultaneously activate persulfate and peroxide in a single injection event. The ZVI catalyst generates sulfate radicals from persulfate and hydroxyl radicals from peroxide, creating a multi-radical oxidative environment that destroys BTEX, naphthalene, and aromatic hydrocarbons. The three remedial materials are delivered via IET's patented injection process, ensuring controlled activation in-situ.

The two-phase mechanism — oxidation followed by biological attenuation — provides both rapid source destruction and sustained long-term treatment. The first phase chemically oxidizes the majority of dissolved and sorbed contaminants, while the second phase uses the spent oxidant by-products (ferric iron and sulfate) as electron acceptors for facultative biological degradation of residual contamination. The 99.9% reduction in all petroleum hydrocarbons at Source Area Monitoring Well B demonstrates the effectiveness of this dual-phase approach.

The active site operations maintained throughout treatment — noted in the Key Success Factors — highlights the key advantage of in-situ remediation over excavation at operating facilities. The patented single-event dual-phase treatment eliminates the need for multiple mobilizations, reducing both cost and operational disruption while achieving superior treatment results.

The silt and sand geology noted in the Key Success Factors indicates a site with moderate permeability — conditions suitable for in-situ remediation via direct push injection. Silt-sand mixtures provide enough permeability for reagent distribution while maintaining sufficient residence time for treatment reactions to occur. The five monitoring wells within the injection area provided comprehensive performance data, with source area wells showing the most dramatic reductions (99.9% at Well B) and the most contaminated well showing 49–65% reductions.

The benzene, toluene, xylenes, and naphthalene contaminants of concern at this site are typical of petroleum hydrocarbon releases — likely from historical underground storage tank systems or surface spills at an active facility. The dual-phase ZVI-activated chemistry is particularly effective for these petroleum compounds because the sulfate and hydroxyl radicals generated by the system target different classes of hydrocarbon molecules, providing broader-spectrum treatment than single-oxidant approaches.