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ISCO Treatment Achieves Closure on Arizona Superfund Site
Benzene Contamination Treated to Non-Detect with Single PersulfOx® Application
Project Highlights
- Previous remediation attempts included soil vapor extraction coupled with groundwater pump and treat/air sparging.
- PersulfOx was applied via gravity-feed through existing remediation wells.
- Single application of PersulfOx resulted in benzene reductions of 1,000 ug/L to non-detect.
- Site closure achieved
Project Summary
Persistent benzene contamination at an Arizona Superfund Site kept the state regulatory agency from closing the site. The City of Tucson maintenance yard contained low residual concentrations of benzene around 1,000 ug/L in a single well. An initial remediation approach used soil vapor extraction coupled with groundwater P&T and air sparging, however results did not meet site closure criteria.
When considering alternatives, the State of Arizona wanted to be efficient by using the existing remediation wells. As a result, Regenesis worked with the state to design a PersulfOx application using the existing infrastructure. Regenesis worked with the state to design and assist with the application of PersulfOx® using the existing remediation wells. After one application, benzene contamination levels were non-detect in the offending well and site closure was achieved.
Remediation Approach
The treatment approach was a trial by the State of Arizona to apply PersulfOx via gravity-feed directly into the existing remediation wells to target residual benzene concentrations. By using the existing in situ infrastructure, the cost of the one-time PersulfOx application was less than $15/cubic yard.
Technology Description
PersulfOx is a sodium persulfate-based chemical oxidation technology which destroys both hydrocarbon and chlorinated solvent-type contaminants in the subsurface. PersulfOx contains a built-in catalyst which activates the persulfate component and generates contaminant-destroying free radicals without the need for the addition of a separate activator.
Regenesis Remediation Services™ – TCE-Impacted Soil Treated with RegenOx®
In Situ Chemical Oxidation Significantly Reduces Contamination Concentrations at Former Manufacturing Facility Site
Regenesis Remediation Services (RRS) was contracted to design and perform in situ chemical oxidation (ISCO) via soil mixing to remediate trichloroethylene (TCE) impacted soils at a former manufacturing site in Hamilton, Ohio. RegenOx® was selected as the primary remediation technology based on site conditions, and the treatment area focused on soilbound TCE contamination averaging 86 mg/kg in the sandy-silt to clay-rich unsaturated soils. The remediation objective was to reduce TCE levels in the soil to below the maximum concentration for Toxicity Characteristic Leaching Procedure (TCLP) of 0.5 mg/L, to allow for subsequent off-site disposal.
The impacted soils were treated in-place by a hydraulic excavator with a specialized mixing attachment. RegenOx was evenly dispersed throughout the contaminated soil, then thoroughly mixed using the excavator attachment. Once mixing was complete, the soils were hydrated with a RegenOx solution, to maximize oxidant loading to achieve aggressive remediation goals. As a result of the soil mixing procedures, a 99% reduction in soil concentrations was achieved. RRS remediated approximately 670 cubic yards of TCE-impacted soil on this real estate redevelopment project. Soil mixing was performed primarily from 4 feet to 8 feet below ground surface (bgs) over an area of approximately 4,500 square feet. Construction activities were able to proceed on schedule due to RRS’s well managed application and proper use of the RegenOx chemistry.
Regenesis Remediation Services™ – TCE Impacted Soil Treated with RegenOx®
Soil Mixing Using In Situ Chemical Oxidation Reduces Contamination Concentrations at Former Manufacturing Facility
Regenesis Remediation Services (RRS) was asked to design and implement a pilot test as well as a full scale design for a soil mixing project using in situ chemical oxidation (ISCO) technology. The specific goal of the remediation plan was to reduce trichloroethylene (TCE) levels to less than .5 ppm, to meet standards for off-site removal as non-hazardous waste. The design included the use of RegenOx® Part A and B as an oxidant in a pug mill system. The TCE at this former manufacturing facility was present from two (2) feet below ground surface (bgs) down to eleven feet bgs in certain areas.
A total of 27,950 pounds of RegenOx Part A and 7,260 lbs of RegenOx Part B were applied over 39 discrete treatment cells during the course of the remediation project. Using an excavator, the top two feet of soil was removed and stored separately, after which the contaminated soil could be excavated and treated with RegenOx Part A and B in a pug mill system. Using RegenOx as an oxidizer, TCE on site was remediated using oxidation to dechlorinate TCE to dichloroethene (DCE), vinyl chloride (VC), and finally to ethene, a benign end product. Two years later, soil samples came back clean and the soil could be trucked off site as non-hazardous waste.
Regenesis Remediation Services™ – PCE Treated with RegenOx®
Soil Mixing Using In Situ Chemical Oxidation Reduces Contamination Concentrations at Former Dry Cleaning Facility
Regenesis Remediation Services (RRS) was hired for this large-scale soil mixing project to treat tetrachloroethylene (PCE) in shallow surface soils. The application used in situ chemical oxidation (ISCO) technology to oxidize residual chlorinated solvents at this former dry cleaner site. The goal was to reduce chlorinated volatile organic compounds (cVOCs), particularly PCE, from >20 ppm to less than 5 ppb. The design of the project was divided into a grid with twelve sections, each 25 feet (ft.) by 21.5 ft., and 5 ft. deep.
Using RegenOx® remediation chemistry and an excavator to complete the soil mixing, the impacted soils were removed by an excavator and a proportional amount of RegenOx was evenly dispersed throughout the excavated soil, then thoroughly mixed using the excavator.
Once mixing was complete, the soils were placed back into the treatment cell while being hydrated with a RegenOx solution made up of RegenOx, water and hydrogen peroxide. By optimizing the contact between the soil, contaminants, and RegenOx, powerful desorption effects strip PCE off of the soil matrix and onto the RegenOx catalytic surface. This catalytic surface contributes to localized free-radical generation, leading to focused and efficient contaminant destruction via soil mixing. After eight days of the completion of the project, 98-100% reductions were achieved in the twelve sections of the grid.
Regenesis Remediation Services™ – PCE Plume Treated with RegenOx®
In Situ Chemical Oxidation Reduces Contamination Concentrations at a Former Dry Cleaner Site
Regenesis Remediation Services (RRS) was contracted to design and perform in situ chemical oxidation (ISCO) via soil mixing to remediate tetrachloroethylene (PCE) impacted soil at a former dry cleaner site located in Cook County, Illinois. RegenOx® was chosen as the primary remediation technology for the chemical oxidation. The treatment area focused on soilbound PCE contamination around 1,170 mg/kg in the clay-rich unsaturated soils. The soil remediation objective was to reduce PCE levels below the 240 mg/kg soil saturation limit established by the Illinois EPA.
The impacted soils were removed by a mini trackhoe excavator and placed inside a vacant unit adjacent to a treatment cell where the soil mixing was performed. A proportional amount of RegenOx was evenly dispersed throughout the excavated, contaminated soil, then thoroughly mixed using the excavator. Once mixing was complete, the soils were placed back into
the treatment cell while being hydrated with a RegenOx solution.
By optimizing the contact between the soil, contaminants, and RegenOx, powerful desorption effects strip PCE off of the soil matrix and onto the RegenOx catalytic surface. This catalytic surface contributes to localized free-radical generation, leading to focused and efficient contaminant destruction. Approximately 242 cubic yards of soil bound contaminant mass was successfully treated at this site. Soil mixing was performed from surface grade to approximately 10 feet below grade.
Regenesis Remediation Services™ – LNAPL Recovery at an Active Gas Station
Combined Treatment Remedies Reduce Contamination Concentrations at Michigan Service Station
Regenesis Remediation Services (RRS) was contracted to remediate a residual LNAPL and dissolved-phase petroleum plume from historic gasoline and diesel fuel releases at an active service station. RegenOx PetroCleanze™ (PetroCleanze) was chosen as the primary remediation technology to facilitate the recovery of residual LNAPL and chemically oxidize contaminants without negatively impacting sensitive infrastructure.
The design called for three (3) application events using PetroCleanze, with Oxygen Release Compound (ORC®) Advanced applied during the final application event in a down-gradient plume cut- off barrier, to promote the enhanced aerobic biodegradation of dissolved-phase petroleum hydrocarbons. Eight (8) injection/extraction wells and 28 direct-push technology (DPT) injection points were used to apply the remediation reagents in the silty-sand aquifer and smear zone. Vacuum extraction was conducted between PetroCleanze applications to recover residual freephase petroleum hydrocarbons liberated from the soils. Reagent distribution monitoring confirmed PetroCleanze was present throughout the targeted source area during each application event.
Prior to the first PetroCleanze application event, no measurable free product was observed at this site since 2006. Less than twenty-four hours after the first PetroCleanze application event, LNAPL up to three inches thick was observed in four of the eight wells. After completing the third application and extraction event, LNAPL was not observed in any wells on site, and BTEX concentrations in groundwater were showing reductions for the first time since the fuel releases first occurred. A total of 2,160 pounds of RegenOx PetroCleanze and 1,120 lbs. of ORC Advanced were injected.
Regenesis Remediation Services™ – LNAPL Recovery & In Situ Chemical Oxidation
Combined Treatment Remedies Reduce Contamination Concentrations at a Former Service Station
Regenesis Remediation Services (RRS) was contracted to remediate a dissolved-phase and residual LNAPL petroleum hydrocarbon plume resulting from historic petroleum fuel releases at a former service station. RegenOx® PetroCleanze™ (PetroCleanze) was chosen as the primary remediation technology in addition to Oxygen Release Compound (ORC®) Advanced, to facilitate recovery of residual LNAPL and chemically oxidize contaminants without negatively impacting sensitive infrastructure. ORC Advanced was applied during the second PetroCleanze application to promote the enhanced aerobic bioremediation of dissolved phase petroleum hydrocarbons.
Eighteen direct-push injection points were used to apply the reagents in the silty sand aquifer and saturated soil over the course of two application events. Vacuum extraction was conducted after each PetroCleanze application to recover residual free-phase petroleum hydrocarbons liberated from the soils. Reagent distribution monitoring during the application events confirmed PetroCleanze was present across the targeted source area. Remediation chemistry was applied via direct-push injection points with a bottom-up approach from 5 to 15 feet below ground surface (bgs). A total of 4,470 pounds (lbs.) of RegenOx PetroCleanze and 720 lbs. of ORC Advanced were injected throughout the course of the two applications.
Regenesis Remediation Services™ – LNAPL Recovery with RegenOx®
Remediation of Residual LNAPL and a Dissolved-Phase Plume at a Former Gasoline Service Station
Regenesis Remediation Services (RRS) was contracted to remediate a residual LNAPL and dissolved phase petroleum plume from a historic fuel release at this former gasoline service station. RegenOx PetroCleanze™ (PetroCleanze) was chosen as the primary remediation technology to facilitate recovery of residual LNAPL and chemically oxidize contaminants without negatively impacting sensitive infrastructure.
Twenty-six (26) direct-push injection points were used during each of the four (4) application events to apply the remediation chemistry in the sandysilt aquifer and smear zone soils. Vacuum extraction was conducted after each PetroCleanze application to recover residual free-phase petroleum hydrocarbons liberated from the soils. Reagent distribution monitoring confirmed PetroCleanze was present across the targeted source area during each application event. Direct-push injection points were advanced using a bottom-up approach between 25 and 20 feet below ground surface (bgs). The injection interval focused on the highest concentrations of contaminants identified in the upper saturated soils and smear zone soils. A total of 13,230 pounds of PetroCleanze were injected via DPT injection points over the course of the project with low pressures and moderate flow rates.
Regenesis Remediation Services™ – PersulfOx® Treats Petroleum Hydrocarbons
In Situ Chemical Oxidation and Enhanced Aerobic Biodegradation Remediate Underground Storage Tank Site
Regenesis Remediation Services (RRS) was contracted to design and implement an in situ chemical oxidation (ISCO) treatment plan to remediate a diesel gas plume from a former leaking underground storage tank (UST) on a residential farm property. The defined treatment area comprised approximately 5,280 square feet (ft2), and the treatment of the gas plume included three application events using
PersulfOx®, with the final application immediately followed by an application with Oxygen Release Compound Advanced (ORC® Advanced). A total of 5,840.6 pounds of PersulfOx and 2,589 pounds of ORC Advanced were injected during the course of the project.
Utilizing PersulfOx remediation chemistry to distribute throughout the subsurface, 91 direct-push injection technology (DPT) injection points were advanced every 100 ft2 over the course of three application events. ORC-A was applied in 53 discrete DPT injection points approximately every 100 ft2. RRS utilized both expendable points and retractable screen-tip injection tooling to apply the PersulfOx and ORC Advanced at discrete intervals across the vertical treatment interval from 8 to 12 feet and 8 to 16 feet below ground surface (bgs) within the sandy saturated soils. Low pressures and moderate application rates were utilized to apply the remediation chemistry at up to four (4) injection point locations simultaneously. RRS personnel performed real-time reagent distribution diagnostics to optimize the distribution of the material.
Redeveloped DOD Site Treated with Turn-Key ISCO Remediation
PersulfOx® Applied at Four Locations on Former Air Force Base in Ohio
Project Highlights
- RRS applied PersulfOx in four separate areas of this former air base, including the parking lot of an active business ensuring litlle disturbance to the commercial operation
- RRS was able to redesign the project from the field achieving maximum injection without downtime and cost over-runs
Project Summary
Regenesis Remediation Services (RRS) was contracted to remediate this former DOD facility. Perchlorethene (PCE) levels of 400 ppb were treated with in situ chemical oxidation (ISCO) employing PersulfOx Catalyzed Persulfate technology. The application included two injection events which involved working within an active parking area of an operating business. The original site design included utilizing direct-push injections, but RRS readjusted the plan in the field after product surfacing was observed in one area that was under construction. Despite the redesign, the application was completed ahead of schedule and under budget
Remediation Approach
Two injection events included the application of 50,000 pounds of PersulfOx through 85 injection points per event in a grid design with treatment 18-31 feet below ground surface. RRS had initially designed the project to use only direct-push injection points. But after surfacing was witnessed, RRS redesigned the project to include the installation of five injection wells.
Technology Description
PersulfOx is a sodium persulfate-based chemical oxidation technology which destroys both hydrocarbon and chlorinated solvent-type contaminants in the subsurface. PersulfOx contains a built-in catalyst which activates the persulfate component and generates contaminant-destroying free radicals without the need for the addition of a separate activator.
