Charlotte Drum Recycling Facility

A remedial event was conducted at an active drum recycling facility to chemically oxidize VOCs that entered the unsaturated soil through a 500 gallon UST that had historically contained used mineral spirits.

In 2011, an 11'x20'x7' excavation of contaminated unsaturated soil was removed from the source area. At the bottom of the excavation, 220 pounds of persulfate and 100 pounds of 15-25 micron ZVI were emplaced within the seeping groundwater before the pit was filled with clean fill.

In 2012, a follow-up injection program utilized permanent injection wells to inject additional oxidant including sodium persulfate and hydrogen peroxide. Four injection wells were installed around MW-4 over the targeted interval of approximately 10' of saturated clayey to sandy silt and weathered limestone soils.

The injection program utilized permanent injection wells to inject oxidants. A total of 1,420 pounds of sodium persulfate, mixed into 750 gallons of 2.5-10% hydrogen peroxide was injected into four wells (IW-1S, IW-1D, IW-2S and IW-2D) in the area around MW-4.

The treatment area covered approximately 4,239 sq ft. The approach combined chemical oxidation followed by biological attenuation using sulfate reduction processes.

Groundwater within MW-4 produced strongly oxidizing water in the following sampling events, as well as elevated sulfate concentrations indicating successful distribution of remedial materials.

This Charlotte project utilized a dual-phase treatment approach combining sodium persulfate and hydrogen peroxide — two complementary oxidants that target different contaminant fractions through different radical chemistry. Sodium persulfate, when activated, generates sulfate radicals (SO₄•⁻) with a standard reduction potential of 2.6 V that are effective against chlorinated solvents and recalcitrant compounds. Hydrogen peroxide generates hydroxyl radicals (•OH) with a reduction potential of 2.8 V — the strongest oxidant in aqueous solution — that rapidly destroy petroleum hydrocarbons, BTEX, and naphthalene.

The permanent well injection method used for this project enables long-term, multi-event treatment delivery. Permanent injection wells are constructed with PVC screen and riser pipe installed in a drilled borehole with filter pack and grout seal — allowing repeated amendment delivery over multiple treatment events without re-mobilization of drilling equipment. This approach is cost-effective for sites requiring phased treatment or where monitoring data indicates the need for supplemental injections.

The 100% reduction of all targeted compounds within one year — with acetone as the only remaining VOC detected — demonstrates the effectiveness of the dual-phase chemical oxidation approach. The facility remained active during treatment, highlighting the key advantage of in-situ remediation over excavation at operating industrial sites where business continuity is essential.

Charlotte, North Carolina is located in Mecklenburg County within the Piedmont physiographic province. The shallow geology consists of Precambrian and Paleozoic-age metamorphic rocks — predominantly gneiss and schist — overlain by residual soil (saprolite) formed by deep in-place weathering. The saprolite is typically clay-rich with variable thickness, creating moderate-permeability conditions suitable for in-situ remediation via permanent well injection.

The 2011–2012 project timeframe and 18-month duration reflect the sustained treatment approach needed for complete contaminant destruction at this site. The combination of chemical oxidation (Phase 1) followed by biological attenuation (Phase 2) — noted in the technology list — is a hallmark of IET's combined-remedy approach: aggressive ISCO destroys the source mass, then enhanced bioremediation polishes residual contamination and prevents rebound through long-term biological treatment.