Remediation at train depot

>99% Contaminant Reduction at Largest Train Maintenance Depot in Northern Europe

Estimated Reading Time: < 1 minute

Case study highlights:

  • Carefully designed integrated remediation strategy used physical, chemical, sorptive and biological treatment
  • Innovative use of PetroFix Permeable Reactive Barriers (PRBs) completed to prevent residual contaminant egress from outside of the treatment area and protect against future spills
  • Significant reductions of petroleum hydrocarbons have been achieved onsite – starting with LNAPL and reaching stringent target values – within nine months

This case study reviews the in situ remediation strategy implemented across the largest train maintenance depot in northern Europe, located in Hagalund, Sweden. As part of the remedial application, Swedish remediation contractor Envytech installed a network of additional monitoring wells across the site. This was done to better delineate the plume and identify any unknown contamination prior to commencement of remediation. Site investigations identified LNAPL across much of the northern area of the site, which required a revised groundwater remediation strategy.

First Application of PetroFix at Petrol Filling Station in Sweden

Estimated Reading Time: < 1 minute

Case study highlights:

  • The integrated remediation treatment strategy ensured that optimum treatment efficiency was maintained throughout the phases of works
  • The amount of excavation and offsite disposal was minimized
  • All underground infrastructure remained in situ
  • All works were completed at an active petrol filling station with minimal disruption to the commercial operations of the facility
  • 12-month period monitoring results show reductions of >98% of the gasoline range of petroleum hydrocarbon concentrations in the groundwater

RGS Nordic was asked by Circle K to remediate groundwater contaminated with gasoline at an active Petrol Filling Station (PFS) in Nykvarn, Sweden. During the site investigation, petroleum hydrocarbon contamination was identified within the fill material around the underground storage tank (UST) farm.RGS Nordic was required to deliver a remediation strategy that posed minimal disruption to the commercial operations of the PFS. The chosen remediation strategy combined targeted excavation, in situ chemical oxidation (ISCO), in situ sorption, and enhanced aerobic biodegradation using a range of complementary REGENESIS technologies: RegenOx®, ORC-Advanced® and PetroFix®.

Scott AFB

Performance-Based Objectives Achieved at Scott AFB

Estimated Reading Time: < 1 minute

Case study highlights:

  • Impacted soil was caused by leaking underground piping and removal of two large UST’s
  • Second round of direct push injections included PetroFix to treat lingering BTEX
  • One month following application of PetroFix, BTEX levels were at non-detect and have continued to remain at that level for 5 sampling events

This case study reviews the Corrective Action Plan (CAP) at Scott Air Force Base, a large military base located in Southwestern Illinois that was contaminated with petroleum impacted soil. One month following the application of PetroFix™, contaminant levels reached non-detect. Benzene continued to remain non-detect through March 2020 and the site was recommended for no further action. The final CAP Addendum proposed two rounds of groundwater treatment by injection at Former Tank 85 to reduce benzene concentrations below the groundwater remediation objectives. The first round of injections was completed in February through March 2018 and consisted of the use of REGENESIS’ RegenOx®, coupled with ORC Advanced® to stimulate aerobic bioremediation. The initial injection was successful in reducing most contaminants within the affected area. The second round of injections at the former UST was completed in March 2019 using REGENESIS’ PetroFix micron-scale remedial fluid.

Buffalo case study

Excavation With RegenOx Successfully Treats Large PHC Plume

Estimated Reading Time: < 1 minute

Case study highlights:

  • After previous consultants attempted remediation without success, C&S created a remediation strategy that successfully reduced the plume.
  • The combined remedy approach of excavation and ISCO exceeded the remediation goals.
  • Successful remediation enabled the construction of a 350,000 sq. ft. $110 million facility at the Buffalo Niagara Medical Campus.

This case study reviews a former gas station site in Buffalo, New York that required remediation due to leaking underground storage tanks. Together with REGENESIS, C&S Consulting designed an in situ remediation strategy to target the residual contaminant plume. RegenOx® in situ chemical oxidant was chosen because of its ability to target petroleum hydrocarbons and its non-corrosive properties. As part of the New York State Department of Environmental Conservation (NYSDEC) Brownfield Cleanup Program, C&S designed a complex remediation program to ensure a quick and affordable solution. Petroleum contamination extended from 10 to 40 feet below grade. The site was excavated to 26 feet below ground surface to remove residual contamination and to enable equipment staging and material handling areas to support the deeper excavation area.

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.

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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

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.
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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.