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Pilot Test Injections for Treating Petroleum Hydrocarbons Using EHC-O速

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Site: Foxhoven Tire Center, Sterling, Colorado Lead Consultant / Injection Contractor: ERO Resources Corporation, Denver


Project Case Study: Pilot Test Injections for Treating Petroleum Hydrocarbons Using EHC-O速

Summary A field scale pilot test was performed to evaluate the performance of enhanced aerobic bioremediation of petroleum hydrocarbons at a vehicle maintenance facility in Colorado. The key constituent of interest (COI) found in groundwater is benzene, ranging up to 106 ppb. Adventus employed its EHC-O速 technology yielding safe, rapid, and effective treatment. Twelve weeks after injection, concentrations of benzene in the performance monitoring well reduced by >95%. Full Scale Treatment will be performed across the entire plume with EHC-O applied by direct push grid injections to enhance plume mitigation.

Background/Objectives The site is a former retail gasoline station which was demolished and the USTs removed in 1996. Approximately 2,400 cubic yards of contaminated soils were excavated and removed in 1996. An AS/SVE system was installed and operated from 1997 to 2004. Since 2004, the site has been under a Monitored Natural Attenuation (MNA) program. BTEX concentrations remained stable and have not decreased during the period 2004 to 2009. Residual contaminants are adsorbed into the soil matrix in the smear zone. The plume is approximately 100 ft wide and 250 ft long. The lithology is predominantly clay / silty clay to a depth of 14ft below ground surface (bgs). This is underlain by coarse sands. Depth to groundwater is 6 ft bgs and the thickness of the contaminated zone is 9 ft (from 6 to 15 ft bgs). The hydraulic conductivity is estimated to be 0.5 and 8.8 ft/day in the silty clay and coarse sands, respectively. The client was willing to implement enhanced biodegradation to reduce the constituent of interest below regulatory standards. EHC-O was the preferred

source of slow-release oxygen due to its ability to supply oxygen plus inorganic nutrients and buffering capacity in a more cost effective manner. Moreover, EHC-O provides a constant buffer, induced through the presence of Zeolites, against alkaline conditions which can be generated by the use of peroxygen compounds.

Figure 1: EHC-O pilot injection locations


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The Solution- Field Scale Pilot Study To verify the efficacy of EHC-O, ERO conducted a pilot test injection of Adventus’ EHC-O immediately upgradient of monitoring well MVW-3. Five injection points on 10 foot centers targeted a 10 foot vertical injection interval from 6 to 16 feet bgs in an area 20 ft x 20 ft (400 ft²). The EHC-O was mixed on-site as a 20% solids slurry and pressure injected, using a discrete interval injection tool and “top-down” method at 2-foot intervals, via a direct-push technology. A total of 225 lbs of EHC-O was injected per location. Exact injection point locations and volume of injected solution varied depending on site conditions and soil matrix. BTEX and geochemical parameters were monitored monthly post EHC-O Injections

Results/Analysis Initial benzene concentrations at MVM-3 exceeded the Colorado Department of Environmental Quality’s regulatory limit of 5 ppb by a factor of about 20. Twelve weeks following injection of EHC-O in the pilot test area, Benzene decreased below the regulatory limit of 5 ug/L with no rebound (Figure 2).

Figure 2: Benzene concentration in groundwater

Redox Indicator Parameters The base line geochemical data (Figure 3) indicated that the aquifer was anaerobic with highly reducing conditions that required significant amounts of EHC-O® to drive the conditions oxic and sustain aerobic degradation of petroleum hydrocarbons. Following EHC-O injections, the oxidation-reduction potential (ORP) increased within the injection zone. Dissolved Oxygen(DO) concentrations increased from a baseline concentration of 0.1 to as high as 9.8 mg/L suggesting that aerobic conditions were established within the injection zone. Given the high Chemical Oxygen Demand (COD), the decrease in DO/ORP after 3 months is attributed to the consumption of oxygen by other sinks (reduced metals) and strong background reducing conditions. Furthermore, an initial increase in pH suggests that hydroxyl ions were released during the hydration of peroxygen compounds (EHC-O) before reverting back to background levels. In addition to natural soil buffering, the decrease in pH could also be attributed to the presence of buffering agent (Zeolites) present in EHC-O.


Project Case Study: Pilot Test Injections for Treating Petroleum Hydrocarbons Using EHC-O速

Figure 3: EHC-O effect on geochemical parameters within the treatment area.

The Cost The material cost of using EHC-O was $1.54/ ft3. The injections were completed in 2 days. Results of this pilot study have shown that using the EHC-O technology offers a safe, effective and cost-efficient remedial solution for UST Sites.

Future Scope of Work Full-scale treatment is proposed implementing EHC-O in the residual source and downgradient area to expedite natural attenuation processes via accelerated aerobic biodegradation of constituents of interest (COIs) in the saturated zone. The dosage for EHC-O to be injected will

be calculated based on conservative assumptions taking into account the background reducing conditions and high COD. The injection locations will be strategically placed to obtain maximum influence to the monitoring wells in the plume and enhance plume mitigation within a single EHC-O application


Adventus • www.AdventusGroup.com

References Steve Mitchell ERO Resources Corporation smitchell@eroresources.com

For more information, contact Adventus by phone at 888.295.8661 or by email at info@adventusgroup.com or online at www.AdventusGroup.com

The Adventus Group provides the environmental remediation industry with a portfolio of innovative proprietary Soil, Sediment, and Groundwater remediation solutions and other technologies shown here. Contact us today to arrange a complementary Technology Transfer Session, or Site Evaluation.

The Adventus Group provides a growing portfolio of leading environmental remediation technologies, including patented products, and is best known for leadership in the area of in situ chemical reduction (ISCR) with the EHC® family of products. Adventus pioneered ISCR in the early 90’s to effectively and economically treat soil and groundwater contaminated with a wide variety of organic constituents and/ or metals amenable to biological and chemical reduction. Other Adventus products are also used to address problems that require oxidation processes and contaminant flux management. We support site owners, consultants, regulators, and others by providing unbiased design, and selection of the most cost-effective remediation strategies. Adventus has a world-wide presence and a strong record of sharing its achievements across more than 500 technical abstracts and publications.

Adventus Case Study--EHC-O in Colorado  

Pilot Test Injections for Treating Petroleum Hydrocarbons Using EHC-O®

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