In Situ pilot remediation of gasworks impacted groundwater, Stockholm, Sweden

Estimated Reading Time: 3 minutes

Introduction

In the north-east of Central Stockholm, a historical industrial site was earmarked for redevelopment. Part of the site comprised a former gasworks, where historical operations have caused a complex mix of contaminants to impact the surrounding soil, groundwater and shoreline sediments.

The large site is due to be redeveloped in a series of parcels including a road, industrial park, residential homes and schools. Remediation is required to ensure the human health risk is removed as part of the restoration of the site. The impacted groundwater also represents an environmental risk and requires treatment. Risk assessments were used to determine that remediation was required to a depth of 20m BGL. The geology of the site is heterogeneous, comprising a shallow made ground, a clay layer and underlying coarse sands.

The sands are highly impacted with a range of gas works contamination included creosote NAPLs and high levels of benzene. The saturated clays are also impacted with dissolved phase contamination. Due to contaminants, concentrations and superficial geologies, a range of remedial methods would be required to ensure the most appropriate was used in each scenario. Therefore, RGS Nordic engaged REGENESIS to design a series of pilot tests utilising several in-situ methods. The results from these trials would then be used to shape the full-scale remediation strategy for the entire gasworks site area.

Download pdf

Combined In Situ Remediation Approach and Planning

REGENESIS proposed a pilot-scale combined remediation approach comprising:

  • Enhanced desorption using PetroCleanze to target high concentrations of soil-bound contaminants of concern (COC’s) in the sands,
  • In Situ Chemical Oxidation (ISCO) using both RegenOx and PersulfOx to target medium to high dissolved phase and soil-bound PAHs in the sandy soil, and
  • Enhanced aerobic degradation using ORC-Advanced to target the low dissolved phase benzene and naphthalene concentrations in the clay.

Results

Groundwater samples were collected 3-4 months after the application of REGENESIS remediation products, see graphs 1 to 3. The results are displayed below

Enhanced Desorption using PetroCleanze

>95% reduction in dissolved phase benzene was achieved with the addition of PetroCleanze. The treatment for PAHs was found to be less effective, primarily due to the low baseline PAH concentrations which were below the optimum treatment concentration range for PetroCleanze.

Graph 1– Effect of PetroCleanze application on dissolved Benzene concentrations

ISCO using RegenOx and PersulfOx

>90% reduction in dissolved phase benzene and PAHs was observed using PersulfOx. In the RegenOx trial, dissolved benzene concentrations were found to decrease by 80%, while PAH levels increased slightly, potentially due to large volumes of desorbed COCs being released into groundwater post-treatment.

Enhanced Aerobic Biodegradation using ORC-Advanced

A sustained reduction in Naphthalene and benzene (despite suspected influx into the test area) was achieved using ORC-Advanced in the saturated clay.

Graph 2– Effect of PersulfOx application on PAH concentrations

Conclusion

  • A wide range of contaminant concentrations were treated effectively using a combined in-situ remediation approach.
  • Substantial reductions in COC concentrations were achieved despite the challenging geological setting.
  • The results from the pilot tests show that all areas of the gasworks site can be successfully remediated in-situ using REGENESIS remediation products, providing significant cost savings when compared with conventional techniques

Graph 3– Effect of ORC-A application on PAH concentrations

PlumeStop® and ORC Advanced® Applications Achieve Successful Results in 24 Hours

Estimated Reading Time: 5 minutes

Project Highlights

  • Successful rapid reduction of petroleum hydrocarbon contaminant concentrations in soil and groundwater completed within approximately 24 hours.
  • In Situ injection application of PlumeStop® Liquid Activated Carbon and ORC Advanced technologies assist REGENESIS strategic partner in bringing closure to facility identified as Leaking Underground Storage Tank (LUST) site
  • Petroleum hydrocarbon concentrations (PHCs) in groundwater and soil reduced below Washington Department of Ecology’s (Ecology) Model Toxics Control Act (MTCA)

Project Summary

An active gasoline station in Bothell, Washington was listed as a hazardous Leaking Underground Storage Tank (LUST) site by the State of Washington Department of Ecology (Ecology) after two subsurface investigations detected petroleum hydrocarbon-impacted soil and groundwater. Entering into the state’s Voluntary Cleanup Program (VCP) in 2001, the site continuously failed to meet regulatory requirements defined in the Model Toxics Control Act (MTCA), despite years of cleanup efforts using a soil vapor extraction (SVE) system and an air sparge (AS) system to remove contaminant concentrations from beneath the site. Charged with remediation, Antea Group partnered with REGENESIS to implement a solution, which included in situ injection applications using PlumeStop and ORC Advanced technologies.

Technology Applied

PlumeStop – an innovative groundwater remediation technology designed to address the challenges of excessive time and end-point uncertainty in groundwater remediation. PlumeStop is composed of very fine particles of activated carbon (1-2µm) suspended in water through the use of unique organic polymer dispersion chemistry. Once in the subsurface, the material behaves as a colloidal biomatrix binding to the aquifer matrix, rapidly removing contaminants from groundwater, and expediting permanent contaminant biodegradation.

ORC Advanced (ORC-A) – an engineered, oxygen-release compound designed specifically for enhanced, in situ aerobic bioremediation of petroleum hydrocarbons in groundwater and saturated soils that, upon contact with groundwater, produces a controlled-release of molecular oxygen (17% by weight) for periods of up to 12 months in a single application, accelerating aerobic biodegradation processes up to 100 times faster than natural degradation rates.

Background

Despite the installation of three groundwater monitoring wells (MW-1 through MW-3) in 2002 and five additional monitoring wells (MW-4 through MW-8) in 2003, concentrations of total petroleum hydrocarbons in TPH-g and BTEX in the western portion of the site exceeded the Model Toxics Control Act (MTCA) Method A cleanup levels. In 2004, a soil vapor extraction (SVE) system and an air-sparge (AS) system were installed and by 2005 an estimated 2,076 pounds of total volatile hydrocarbons (TVH) were extracted, with concentrations falling below MTCA Method A cleanup levels for two consecutive quarters. Laboratory analysis of groundwater samples collected during the following two quarters, however, indicated that hydrocarbon compounds in groundwater had increased in several monitoring wells.

Challenge

The AS system was restarted in October, 2005 and operated on an approximate 2-week-on and 2-week-off cycle through February, 2009, when it was shut down based on non-detectable hydrocarbon concentrations in all but one groundwater monitoring well, MW-3. As a remediation strategy to address TPH-g and benzene impacts that remained in well MW-3, sulfate injection was proposed. However, due to high sulfate concentrations observed in the down-gradient monitoring well, MW-9, the sulfate injections were suspended in November of 2012 and evaluations of other chemical injection methods were proposed.

REGENESIS Remediation Services (RRS) recommended PlumeStop injection and completed two soil borings for design verification testing in November, 2015. Soils on-site were primarily sand and gravel, with two, 4-6” clayey silt layers—one at approximately five feet and the other at 10.5 feet below ground surface (bgs). Based on field screening with photoionization (PID), contamination appeared to be concentrated at the 8-9 feet depth interval, a point at which soil increasingly hardens. With results of a laboratory analysis, RRS modified the design, adjusting the vertical treatment interval from 5-12 feet below ground surface to 7-11 feet, with the concentrations and quantities of PlumeStop and ORC-A remaining unchanged.

Solution

REGENESIS Remediation Services (RRS) injected approximately 200 gallons of PlumeStop 6,000 ppm solution into on-site wells IW-1 and SVE-1 December, 2015. Using strategically placed point locations to rapidly reduce contaminant concentrations, Direct Push Technology (DPT) was employed to advance injection points throughout the treatment zone at each respective injection point location. The following day, the solution was increased to 12,000 ppm, for a total of 835 gallons of PlumeStop solution (as applied with water) injected within the targeted treatment interval to deliver the full volume of remediation chemistry and complete the application on schedule.

A total of nine (9) PlumeStop DPT injection points were cleared to 5 feet below ground surface pre-injection, and during the course of the injection seven (7) point locations were advanced to a depth of 11 feet below ground surface and retracted to a depth of 7 feet below ground surface using 1.50 inch outer diameter (O.D) Geoprobe® injection rods with retractable screen tooling.

Additionally, 120 pounds of ORC-A were applied at approximately 30% solution (w/w) in cleared boreholes via a backfilling method, which involved drilling to the target depth, retracting the rods and pouring the ORC-A slurry down open boreholes to approximately 5 feet below ground surface in order to properly abandon points.

Results

During the course of the injection and at the end of the application, increases in groundwater levels were observed in monitoring wells MW-3 and MW-9 in the treatment area. Additionally, increases in ORP (oxidation reduction potential) were observed in MW-2, MW-3, MW-6, MW-7, MW-8, and MW-9. Increases in dissolved oxygen were also noted post-injection in MW-2, MW-3, MW-6, MW-7, MW-8, and MW-9.

The successful and rapid reduction of petroleum hydrocarbon contaminant concentrations in soil and groundwater was achieved within approximately 24 hours, despite difficulty injecting the material via direct-push injection points. With field modifications, RRS was able to not only mitigate surfacing issues by switching to injection via injection well application but also observe the desired distribution of the remediation chemistry in the subsurface.

In the same way the State of Washington Department of Ecology continues to take steps and implement tools that will streamline the cleanup process even further, REGENESIS recognizes the critical need for cost-effective, sustainable and environmentally sound remediation solutions. Whether pioneering new in situ technologies in the lab or rolling up its sleeves in the field to ensure a successful project outcome, REGENESIS remains committed to advancing the remediation industry for the benefit of its partners as well as for the future of the world at large.

How PlumeStop® Brings Sites to Permanent Closure

PlumeStop rapidly removes contaminants from groundwater and stimulates their permanent degradation. This exciting, turn-key solution offers several key benefits for addressing brownfield site treatment, including:

  • Rapid reduction of dissolved-phase plumes
  • Distribution of widely under low injection pressures
  • Achievement of stringent groundwater clean-up standards
  • Providing a long-term means of addressing matrix back–diffusion
  • Elimination of excessive time and end-point uncertainty associated with groundwater remediation

PlumeStop is composed of very fine particles of activated carbon (1-2µm), suspended in water through the use of unique organic polymer dispersion chemistry. Once in the subsurface, the material behaves as a colloidal biomatrix, binding to the aquifer matrix, rapidly removing contaminants from groundwater, and expediting permanent contaminant biodegradation. This unique remediation technology accomplishes treatment with the use of highly dispersible, fast-acting, sorption-based technology which captures and concentrates dissolved-phase contaminants within its matrix-like structure. When contaminants are sorbed onto the regenerative matrix, biodegradation processes achieve complete remediation at an accelerated rate, leading to successful site treatment.

remediation case study

Redevelopment of former gas works unlocked by combining technologies

Estimated Reading Time: 5 minutes

Integrated remediation strategy provides rapid and cost-effective clean up

 

Fig. 1 – Remedial works at residential construction site
  • During the construction of multiple residential dwelling it became apparent that a historical gas works had previously occupied the site.
  • A targeted site investigation needed to be completed quickly to identify the areas requiring remedial action, enabling construction to continue in plots outside of the plume.
  • A combined remedial strategy was required to address soil, LNAPL, DNAPL and dissolved phase contamination.
  • The implementation of the treatment had to be completed around partially completed housing and live underground services.
  • The remedial works had to be completed quickly in a manner as to not impact the build program.
  • The strategy needed to provide appropriate protection to both human health and controlled waters.
  • The need to respond and act quickly required excellent communication and good working relationships to be established between the consultant, stakeholders, regulators and multiple specialist remediation contractors and suppliers.
Download the pdf

Remedial Approach

A wide range of remediation technologies were deployed sequentially and in parallel to provide the most rapid and cost effective clean up:

  • Ex situ bio-piling of hydrocarbon impacted soils
  • LNAPL skimming
  • Pump and treat (P&T) of dissolved phase contamination
  • DNAPL pumping and settlement/collection
  • Enhanced abstraction of contaminant mass using PetroCleanze
  • In Situ chemical oxidation (ISCO) using RegenOx, which is compatible with footings and services already in place
  • Accelerated aerobic natural attenuation using ORC Advanced slurry
  • Accelerated aerobic natural attenuation using a pelletised oxygen-release compound (ORC Advanced) placed in the backfill
  • PlumeStop Liquid Activated Carbon injection to install a subsurface activated carbon filter to adsorb and biologically degrade dissolved phase contamination
  • Gas vapour membrane installation

Ex situ treatment

The impacted materials within the unsaturated zones within Plume A and B were excavated and placed in a biopile for onsite treatment (Figure 1). Nutrients were added and the biopile was turned until remedial targets were achieved. The soils were then backfilled under the CL:AIRE Code of Practice. Prior to backfill with the remediated soils, ORC Advanced Pellets were added to the base of the excavation. This provided a source of dissolved oxygen for up to a year, stimulating the growth of an effective aerobic biomass and accelerating the degradation of the petroleum hydrocarbon contamination.

Fig. 2 – Details of Ex-Situ Treatment

In Situ Treatment

The southern part of Plume A was made inaccessible by footings and services; here in-situ treatment was completed accommodate these obstructions without compromising treatment efficacy. Within Plume B, where high levels of contamination had been encountered (Figure 2), several in situ remedial actions were taken as appropriate to concentration, location and sequence in the strategy:

  • REGENESIS injected PlumeStop, a micron-scale colloidal Liquid Activated Carbon substrate along the western margin of the site via direct push to protect the offsite surface water. PlumeStop creates a subsurface activated carbon filter which adsorbs the contaminant influx, which is then degraded by the microbial growth on the carbon biomatrix. Biological degradation was also accelerated through co-application of ORC Advanced and the presence of the pelletised ORC placed in the base of the excavation upgradient, providing a controlled release of oxygen.
  • Where LNAPL and high dissolved phase concentrations were observed, a network of injection boreholes were installed by Rake Remediation/REGENESIS. Many of the wells were installed by removing suspended floors and lifting in a mini-rig to complete the drilling beneath partially constructed dwellings. Through these wells, multiple applications of RegenOx were completed. This in situ chemical oxidant was chosen as it was safe to handle on this busy site and would not corrode services installed at the site, nor would it be detrimental to the concrete footings.
Fig. 3 – Details of In Situ Treatment

  • Following the ISCO, ORC Advanced slurry was injected to enhance the natural attenuation (ENA) of the residual dissolved phase contamination to low levels.
  • In Plume B, high levels of contamination in the form of both L- and DNAPL were encountered. This was removed using a P&T system augmented with PetroCleanze, an inorganic surfactant that uses a high pH, carbonates, silicates and partial oxidation to remove contaminants from soils. The PetroCleanze was injected to produce a temporary desorption event, which once observed, allowed the P&T system to be switched back for a short period to remove the contamination. This process was repeated three times to maximise the efficacy of the P&T and shorten the treatment programme.
  • Once the NAPL was removed, multiple rounds of RegenOx were completed, followed by ORC Advanced via injection through wells.
  • Long term groundwater monitoring programme was put in place to monitor the effectiveness of the clean-up.

Results

The following graphs (Figures 7 and 8) show the variations in concentrations for selected priority contaminants of concern over the monitoring period for Plume A and B. These show a marked reduction in the hydrocarbon dissolved phase concentrations over time, with compliance achieved with the remedial criteria.

Fig. 7 – Plume A: Benzene concentrations over time. (red line = DQRA)
Fig. 8 – Plume B: Aromatic C8-C10 concentrations over time (red line = DQRA)

Conclusion

Complimentary remedial technologies were combined successfully to achieve:

  • Contaminant mass reduction to below remedial targets in the soil and groundwater within 6 months.
  • Protection of onsite and offsite receptors.
  • Written confirmation by the Environment Agency that they ‘agree with (the reports’) conclusions’ and that ‘development may proceed’.
  • Remediation completed on a tight budget – as remediation had not been foreseen by the developer.
  • Ex-Situ remediation of soils and their reuse on site under the CL:AIRE CoP avoided offsite disposal of ~800m3 to landfill.
  • In Situ enhancement of the P&T system, minimising the time, cost and volume of abstraction required.
  • By combining the technologies intelligently, both simultaneously and sequentially, the programme length was minimised – allowing construction to continue within only 6 months.

Ex Situ Chemical Oxidation of Soils at a Fuel Storage Depot, Sweden

Estimated Reading Time: 3 minutes

With RGS Nordic

Summary

An area of impacted soils was discovered at an oil-distribution depot at a Swedish harbour. This was thought to have occurred due to historic spillages and leaks from industrial land use on the site. Remediation of the soils was required to MKM levels (Swedens generic industrial land use clean-up criteria).

Download pdf

As the contaminated soil was quite shallow (1.0-2.5m BGL) it was determined that excavation would be easily achieved. Treatment of the soils through biopiling or windrows was not deemed appropriate due to limited space. Therefore ex situ mixing of the soils with a chemical oxidant, PersulfOx, was chosen in order to provide rapid reduction of the contaminant mass. This would be followed by a short period of enhanced biological degradation in the treated soils, stimulated by the increased redox in the soil moisture following the chemical oxidation process. Partial chemical oxidation of the hydrocarbons into more bioavailable and biodegradable compounds would also accelerate biodegradation of a proportion of the residual contaminant mass.


PersulfOx was added into the soils at a dosage rate of 17kg per 1m3 of soils. This was then mixed thoroughly using an Allu hydraulic bucket, during which the soils were wetted. This would increase the soil moisture in order to facilitate the chemical reaction. Care was taken to avoid adding too much water and risk damaging the geotechnical properties of the soils.

The sides and base of the excavations were validated to delineate the vertical and lateral extent of the impacted zone and ensure that all of the contaminated soil had been removed. Following application of the PersulfOx, the treated soils were then placed back into the excavations and validated. Following successful validation, the soils were compacted to the required capacity in order to allow site traffic to pass over the treated areas.

Results

Sampling of the soils three months after treatment, showed that the target concentrations had been reduced to below the target guideline values, see Figure 1 and 2.

Fig. 1: Combined results from both areas, Aliphatic C5-C16

  • The impacted soils were successfully remediated in a short period of time.
  • Due to its built-in catalyst, the use of PersulfOx avoided the need for dangerous activators such as hydrogen peroxide or caustic soda, making the remediation process much safer.
  • The treatment area was minimised, making the remediation of the soils practical and avoiding greater disruption to the site operator.

Fig. 2: Combined results from both areas, Total Petroleum Hydrocarbons

Combined Remedy Leads to Site Closure

Estimated Reading Time: < 1 minute

Case study highlights:

  • Significant contaminant reductions achieved in both the source area and core plume
  • 8-10 weeks of time saved compared to alternative approaches
  • $500,000 saved in project costs compared to alternative Electrical Resistance Heating (ERH) approach being considered

This case study reviews an active Underground Storage Tank (UST) case with the Arizona Department of Environmental Quality (ADEQ), where the site needed to meet ADEQ closure levels quickly in order to seek risk-based closure as part of a property transaction. After performing remedial assessment activities, the consulting firm Antea Group selected a combined remedy approach from REGENESIS, which included soil mixing using RegenOx® and H2O2 in the source zone and ISCO injections using PersulfOx® in the core plume. The solution from REGENESIS achieved ADEQ Closure levels for the site and now Antea Group is seeking a risk-based closure.

Galligu and TPH Contaminated Site Remediation in Runcorn, UK

Estimated Reading Time: 5 minutes

Summary

Wildgoose Construction’s redevelopment of a former bus depot into commercial/retail, including a new public house for Marston’s, posed unique and complex challenges. Geotechnical and Environmental Associates Ltd (GEA) identified that each step in the solution process would have a follow-on effect, so a well thought-out, integrated approach was crucial for the project’s success.

BB Award and GE Award finalist logos

Fig. 1 – PlumeStop barrier injection near site boundary

The site comprised a hillside covered by industrial waste from the Leblanc process comprising several metres of galligu above a black ash layer which was underlain by cohesive glacial till. Two geoenvironmental issues needed addressing:

  1. Stability: the galligu had a weak structure, with a ‘toothpaste’ consistency in parts;
  2. TPH contamination; leaking underground storage tanks (UST)s onsite resulted in fuel infiltrating the subsurface and moving offsite via perched water in an ash layer beneath the galligu.
The downgradient boundary comprises a steep slope to the canal where the contaminated groundwater egressed at ground-level, polluting the waterway.
Download pdf

An integrated solution: Soil/cement mixed panels were used to support structures, with a soil/cement mixed mattress covering the entire site, as a load transfer platform. Installation of these panels altered the groundwater flow, which therefore needed modelling to ensure the contaminant treatment could be targeted accurately.

Modelling groundwater flow through anthropogenic waste and man-made installations presented a challenge, as models are designed for more homogeneous and isotropic conditions. However, it was shown that groundwater would be raised and channelled towards the panel ‘wall’ at the boundary. Here the groundwater would funnel through gaps at a higher velocity.

An innovative Liquid Activated Carbon substrate was used to integrate with the panels, which required no maintenance and provided effective treatment in the extremely bio-toxic environment created by galligu. This subsurface carbon-filter entirely prevented contaminant egress from the site.

Integrated Geoenvironmental Solution

The structure of galligu varied across the site: from fused crystalline ‘rock’ in upper areas, to a weak ‘toothpaste’ consistency at depth – unsuitable to build on. Previous settlement caused hydrocarbon leaks from broken pipes, resulting in the bus depot closure. Potential settlement prevented the use of a raft foundations. In addition, the presence of a high pressure gas main prevented the use of a piling solution. Therefore a soil/cement panel solution was piloted and then installed full scale by Deep Soil Mixing Ltd, using in situ mixing equipment (see figure 5 and 6).

Fig. 2 – Conceptual Site Model in Section

Fig. 3 – Remedial Strategy in Section

The geotechnical solution created a new challenge: to understand how the cement stabilised columns would alter the groundwater flow pattern across the site. This was crucial to know, in order to determine where contaminant egress may occur at the site boundary.

Galligu creates strongly alklaline, arsenic rich, reduced conditions in the subsurface. This inhibits biological degradation, resulting in ongoing persistence of TPH. This chemistry prevents typical remedial approaches to be taken as the remedial solution would have to: not react with the cement, galligu or ash; capture the hydrocarbons in the toxic conditions produced by the galligu; work for decades, until the residual secondary source is depleted, without power, pumping or further action.

When PlumeStop Liquid Activated Carbon (LAC) was chosen, the placement of this underground filter needed to be carefully considered. At the boundary, the groundwater flow was extremely fast through the gaps. Hence, by moving the barrier into the site, the slower groundwater allowed for a longer treatment time in the PlumeStop. The PlumeStop barrier length was guided by the modelling, to transect the entire contaminant plume. REGENESIS provided bespoke design work to match the predicted groundwater flow and contaminant levels (i.e. the contaminant flux).

Application

REGENESIS worked with GEA and their client to ensure the design matched their requirements. REGENESIS also managed and completed the injection works onsite using direct push injection, and then provided a completion report and warranty.

All work was completed on a busy construction site, with a high-pressure gas main and large easement.

Results

Following injection of the PlumeStop across the width of the predicted contaminant plume, the TPH concentrations at the site boundary were dramatically reduced by 98%. Although not the main focus of the treatment, low levels of PAH were also reduced to non-detect.

Fig. 14 – TPH concentrations at site boundary before and after PlumeStop barrier treatment

Conclusion

This integrated geoenvironmental solution was highly successful, delivering a number of key achievements:

  • Galligu is often treated ex-situ, which was not practical in this situation. The soil/cement stabilisation approach provided an economical solution to the geotechnical problems presented by Galligu, whilst encapsulating the contaminants within it and minimising future leaching. Being a low disturbance technique, it also permitted treatment alongside a high-pressure gas main where piling was not permitted. Groundwater modelling of the altered flow pattern was required to allow the design of the remedial scheme. Due to the inevitable uncertainties associated with groundwater flow through the ash layer this modelling was carried out using a low cost electrical analogue modelling technique.
    • The remedial scheme allowed the project to proceed within budget and was delivered on time.
    • Treatment of petroleum hydrocarbon contamination in the presence of galligu has not been completed previously to our knowledge.
    • This was the fourth use of PlumeStop in the UK and represents an imaginative and fully thought-through application that allowed highly effective remediation, protection of a public waterway and cost-effective geoenvironmental treatment of a busy and difficult site.

This project has won in the category ‘Best Conceptual Design’ in the Brownfield Briefing Awards 2018, and was shortlisted in the GE Awards 2018.

Combined Remedy Chosen for FDEP Innovative Technologies Program

Estimated Reading Time: < 1 minute

Case study highlights:

  • An in situ combined remedy approach that was chosen as the most technically-feasible and cost-effective strategy in a competitive bid scenario for the Florida Department of Environmental Protection’s Innovative Technologies Program
  • High level of site complexity – flowable fill layer present over the treatment area, difficult geology (i.e., clays and limestone), and close proximity to structures, utilities and a roadway
  • Use of PlumeStop, RegenOx, and ORC Advanced to successfully address a large BTEX plume

A former gas station site in Taylor County Florida had undergone prior remedial efforts over the years. The Florida Department of Environmental Protection (FDEP), through its Innovative Technologies Program, engaged the environmental consulting firm, Advanced Environmental Technologies LLC (AET) to design an alternative combined remedial approach employing PlumeStop®, RegenOx® and ORC Advanced®, to sorb, degrade, and destroy the existing petroleum contaminant plume. Prior to full-scale implementation, treatment of this site began with a thorough Design Verification Testing (DVT).

RegenOx Application Quickly and Efficiently Lowered Diesel Range Organics (DRO) to Below ADEC Requirements

Estimated Reading Time: 2 minutes

Project Highlights

  • Two applications of RegenOx® reduced contaminants to a level below the Alaska Department of Environmental Conservation (ADEC) standards to protect against migration to groundwater
  • Completed in 8 weeks, restoring agriculture viability
  • Soil was safely and efficiently cleaned preventing fuel from contaminating a nearby sensitive receptor
Download PDF

diesel remediation

Project Summary

A Hydaburg site in Alaska, owned by Alaska Power and Telephone, previously housed diesel fuel generators and is now being converted into a hydro-electric plant. The land was contaminated by a diesel fuel spill requiring remediation. Approximately 1,000 cubic yards of soil were impacted and the starting concentrations of DRO were approximately 1 500 ppm. The goal was to reduce concentrations to below the ADEC standard of 230 ppm.

Due to the cold weather encountered during this project and the sensitive infrastructure in the area, it was important that the technology work effectively in less than ideal conditions. Also, the technology could not be corrosive nor generate excess heat. RegenOx, produces minimal heat and pressure, is non-corrosive, and works well at any temperature above freezing making it ideal for this project. Additionally, RegenOx is a chemical oxidant which quickly and effectively destroys a range of contaminants-in this case, DRO. The soil was screened with a trommel and RegenOx was mixed in a cement truck before being sprayed onto the soil. RegenOx was applied twice, with the applications spaced a week apart. This site required 20 lbs of RegenOx per cubic yard, in total 20,000 lbs.

Technology Description

RegenOx is a percarbonate-based in situ chemical oxidation technology that rapidly destroys petroleum hydrocarbons and chlorinated contaminants through powerful chemical reactions. It directly oxidizes contaminants while a catalytic component generates oxidizing free radicals to destroy the target compounds.

Results

After two applications of RegenOx, the concentrations of DRO went from 1,500 ppm to below 125 ppm, satisfying the ADEC requirement of below 230 ppm, within 8 weeks. After the remediation treatment, the soil was spread out, grass was planted and is now growing at the Hydaburg site, attesting to the renewed health of the soil.