FRC 2023 Poster Presentations
Posters Listed Alphabetical Order by Presenter's Last Name
Do You Know Your Site? Qualitative Characterization, Modeling, and Remediation to Predict Site Closure
Bill Brab, CPG. P.G., Senior Geologist, AST Environmental, Inc.
Abstract:
Background/Objectives. A review of the Statistical Inventory Records in August 1993 indicated a release of fuel had occurred into the environment, five (5) gasoline tanks were documented at the site and were subsequently removed in November 1993 or closed-in-place in June 2004. A series of mobile-enhanced multi-phased extraction events were completed between July 1993 and November 2008. The site is >0.25 miles from a wellhead protection area and is zone commercial and vacant. A dedicated multi-phase extraction unit was deployed at the site beginning in March 2011 and operated until August 2017. Soil gas survey points installed and were below the look-up-values and the volatilization to indoor air is not a complete pathway; however, free product was present in one on-site monitoring well and benzene remained elevated above the site-specific clean-up level (SSCL) in seven (7) monitoring wells on and off-site. Approach/Activities. A Remedial Design Characterization was conducted in September 2018 to rapidly characterize the extent of total petroleum mass in soil and groundwater at the site, emergency interim corrective action was approved for in-situ remedial injections in November 2018 and was completed in December 2018. Modeling of the total mass present at the site in soil and groundwater indicated the required time to reach clean-up would be 4-6 years following completion of the interim measures. To evaluate the progress of the interim measures, a high-resolution site characterization (HRSC) was conducted in January 2021 using the laser-induced fluorescence (UVOST®) to identify the potential extent of remaining residual LNAPL at the site. The UVOST survey was utilized to optimize the subsequent qualitative High-Resolution Site Characterization (qHRSC) program completed in June 2021, the qHRSC Program consisted of the installation of eighteen (18) soil borings across the site to establish a new baseline for contaminant concentrations at the site and update the existing conceptual site model (CSM). Using the data from the qHRSC, a surgical injection design was developed for the site using Trap & Treat® BOS 200+®. To expedite the time to site closure, the second injection event was approved in November 2021 and was completed in March 2022. Post-injection performance monitoring of COCs and degradation biproducts were completed from baseline (RDC 2018) thru the current date, microbial diagnostics were completed throughout 2022 to further evaluate conditions and progress at the site. Results/Lessons Learned. The presentation will focus on the demonstration of the efficient use of investigative methods to expedite the time to implement a fiscally responsible remediation program, resulting in reduced time to reach site closure and cost to clean-up expenses. A review of the historical Conceptual Site Model (CSM), involvement of all stakeholders to update the CSM using qHRSC (HRSC + RDC methods), and implementation of in-situ injection methods and technologies which enhance source zone depletion and significantly reduce the time to reach the site-specific clean-up goals to justify site closure and No Further Action will also be discussed. Remedial evolution will highlight the development, selection, and use of a new and cutting-edge application of cometabolic synergy: powdered activated carbon coupled with an enhanced biological component. Lessons learned and relevant data to be presented will include benefits of high-density indiscriminate (regardless of field screening/field observations) soil and groundwater sampling for qualitative analysis in the laboratory, post-injection performance analytical and microbial diagnostic tools will also be provided.
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Meeting the Challenges of Groundwater in Fractured Rock
Bill Brab, CPG. P.G., Senior Geologist, AST Environmental, Inc.
Abstract:
This presentation will describe how to characterize a fractured bedrock site succinctly and successfully with the intention to design and inject pertinent reactants utilizing high-capacity pumps and narrow-interval straddle packers. The main difference between this approach and conventional bedrock characterization and injection is the deployment of multiple methods to evaluate lines of evidence during investigation; this process is not reliant on few techniques or tools to render a subsurface model and/or design. These diverse practices include both conventional and novel means to evaluate a borehole characterization and injection point (BCIP), which includes noninvasive surface and borehole geophysical methods and intrusive geological and aquifer characterization procedures (i.e. lithology and hydrogeology). The intention and planning throughout the investigation is to develop a remediation program with significantly increased distribution (radius of influence (ROI) can underserve the injection program and performance within the formation) via fractures, features, discontinuities, secondary porosities, and other subsurface pathways that are either typically under-characterized or overlooked for injection operations. By overlaying these unique data sets, representations, and video of geology and subsurface contaminant conditions (sorbed contaminant mass and mass flux), environmental practitioners can move forward in confidence with a BCIP injection design that uses actionable data. The design is therefore practical, efficient, and effective – completed in one mobilization or several sequenced events.
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Fiscally Conscious DNAPL Remediation - Legacy Liability to Managed Closure
Bill Brab, CPG. P.G., Senior Geologist, AST Environmental, Inc.
Abstract:
Background/Objectives. A former chemical plant stored, repackaged, and (re)distributed chemicals, including but not limited to: hydrogen peroxide, methylisobutyl carbinol (MIBC), tetrachloroethene (PCE), acetone, ethanol, and diesel fuel. Based on the site’s geology, a phased approach utilizing combined remedies was selected as the preferred remedial option: Trap & Treat® BOS 100® was installed as a permeable reactive barrier (PRB) off-site to capture dissolved impacts leaving the facility, and shallow soil mixing with activated persulfate was used to mitigate unsaturated soil impacts adjacent to source media. Additionally, Trap & Treat® CAT 100 was used to mitigate saturated soil source mass and groundwater impacts. Approach/Activities. High-density quantitative soil and groundwater sampling was conducted in 2011 and 2012 to refine the existing Conceptual Site Model (CSM). High density soil and groundwater sampling verified vertical and horizontal distribution of contaminant mass on and off-site, significant unsaturated mass confirmed a sustained NAPL source for a dissolved solute plume downgradient further off-site. A Phased approach utilizing combined remedies was selected as the remedial option for the facility; interim corrective action was completed in 2013 and 2014 and included 1) an off-site in-situ permeable reactive barrier utilizing Trap & Treat® BOS 100® to capture dissolved impacts leaving the facility and 2) shallow soil mixing activated persulfate to mitigate unsaturated soil impacts adjacent to source media. Pilot-Scale Phase 1 was conducted in December 2016 utilized Trap & Treat® CAT 100 to evaluate effectiveness with mitigating saturated source mass soil and groundwater impacts. Full Scale Phase 2 completed in September 2018 included additional off-site source and dissolved-phase treatment utilizing Trap & Treat® CAT 100. Full Scale Phase 3 and Phase 4 were completed in September 2019 and September 2020 respectively) included CAT 100 injections in the source area. The final Full-Scale Phase 5 was completed in September 2021 included CAT 100 injections in the remaining on-site source areas. Results/Lessons Learned. The presentation will discuss the development of the CSM over time, highlight the remedial action as a site-specific case study example including characterizing and injecting remediation products into tighter lithologies, and the financially responsible phased approach deployed at this site over multiple fiscal years. Lessons learned and relevant data to be presented will include the benefits of high-density indiscriminate soil and groundwater sampling for quantitative analysis in the laboratory and improvements to the BOS 100® platform to mitigate source-level DNAPL mass on-site. Long term performance monitoring will demonstrate CVOCs reductions in comparison with abiotically and biologically generated degradation byproducts and microbial biomass and metagenomic sequencing analysis, supporting the decision to issue a managed closure status for the facility in the 4th Quarter of 2022.
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GWQS Achieved in Fractured Bedrock at a TCE Release Site in New Jersey
Bill Brab, CPG. P.G., Senior Geologist, AST Environmental, Inc.
Abstract:
Background/Objectives. Trap & Treat® BOS 100® was injected in fractured, shale bedrock at a corporate site in New Jersey in 2017. An unknown TCE discharge was discovered in groundwater testing in 1992, and over the course of 20 years several remedial actions were completed including soil removal. In 2016, a Remedial Investigation Report (RIR) was completed and the Trap & Treat® approach was recommended to update the existing conceptual site model (CSM) before applying a focused BOS 100® injection program in 2018 with post-injection monitoring conducted quarterly. The Classification Exception Area /Well Restriction Area (CEA/WRA) was lifted in 2020 and the site was granted No Further Action (NFA) status, after achieving New Jersey Ground Water Quality Standards (GWQS) only 25 months post-injection. Approach/Activities. The site was in a grassy area abutted by woods at a corporate campus. Previously, three other AOCs onsite were managed and closed using excavation and removal of overburden soils; afterwards, chlorinated solvent impacts were not above limits in overburden soils. This injection effort focused on treating groundwater in bedrock. The Area of Interest encompassed ~3,500 ft2 and was situated in the Passaic Formation, which consists of reddishbrown argillaceous shale with localized sandstone/siltstone interbedding. Depth to water occurs at ~10 ft below ground surface (ft-bgs), and the impacted groundwater interval was from ~10 to 60 ft-bgs. The contaminants of concern (COCs) were TCE and 1,1-DCE, and the project objective for both constituents in groundwater was 1 µg/L. A key to bedrock remediation is to not focus solely on highly transmissive zones. The smaller aperture fracture networks and overlying weathered bedrock habitually contain more residual contaminant mass than more transmissive features. Being able to access, isolate, and treat these zones is key to success at difficult fractured rock sites, and many sites require a combination of methods due to dissimilar properties between the less consolidated and consolidated units. A Transition Zone (TZ) of partially weathered rock was present from 10 to 25 ft-bgs that prevented the use of standard direct push technology (DPT) equipment to reach and isolate this interval for assessment and treatment. TZ remediation consisted of utilizing RPI’s GeoTAP™ Method; this methodology was developed to gain access to challenging geologies and first involves pre-drilling to the desired depth using sonic, air rotary, or hollow-stem augers (HSA). The evacuated borehole is then backfilled with hydrated bentonite chips or pellets to seal the bore wall, and a DPT rig can then push through the bentonite column to reach the desired injection depth intervals without compromising the bore seal. Remediation slurries or fluids are then injected through the bentonite. This technique has been used successfully on more than 30 project sites across the country, accessing depths as great as 180 ft-bgs. Bedrock characterization and injection points (BC/IPs) were installed with air rotary/HSA in the competent lithology. Casing was installed from ground surface to 15 ft-bgs and the vertical interval of interest was left uncased so borehole geophysical tooling and discrete interval (18 in.) sampling with a straddle packer could be conducted. Finally, the bedrock zone remediation implementation used a custom straddle packer (18 in. interval) to deliver BOS 100® slurries pumped from a unique bedrock injection unit with accessible flow rates ranging from 50 to 250 gallons per minute and pressure up to 3,000 psi. Results/Lessons Learned. The focus of this presentation will be to showcase recent improvements to techniques and approaches to access contaminant impacts in transition zones/saprolite/epikarst and consolidated lithologies for characterizing in situ remediation. This site-specific case study will illustrate the development of quantified, high-density CSMs using high-density, discrete groundwater sampling for quantitative lab analysis, which provides for surgical and aggressive in situ remediation techniques that install requisite in situ treatment product precisely where it is needed.
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Bench Scale In-Situ Stabilization/Solidification Study for Site Impacted with Coal Tar
Tomecia Bradley, CHMM, Program Manager, KEMRON Environmental Services, Inc.
Abstract:
KEMRON Environmental Services, Inc. performed an in-situ solidification/stabilization treatability study on materials sampled from the Camden Gas Site located in Camden, New Jersey. The test materials were impacted with volatile organic compounds, semi volatile organic compounds and petroleum hydrocarbons typically contained in coal tar waste samples. KEMRON evaluated the effectiveness of pozzolanic additives including combinations of type I Portland cement and blast furnace slag cement. Testing was performed on a “representative”” site material in two phases including preliminary and optimization mixture evaluations. The study was designed to facilitate full-scale treatment using soil auger technologies. Therefore, KEMRON evaluated the density and viscosity of each reagent grout mixture to ensure these parameters were within an acceptable range for soil auger delivery. Testing of the treated samples included unconfined compressive strength testing, permeability testing, wet/dry durability testing, and leachable volatile organic compounds, semivolatile organic compounds and extractable petroleum hydrocarbons analyses as determined by the Synthetic Precipitation Leaching Procedure (SPLP). Additional testing of selected candidate samples included leachable contaminants of concern as determined by the 1315 method of the Leaching Environment Assessment Framework (LEAF). The treatability study identified mixtures capable of meeting the project goals and regulatory criteria. It was then determined that full-scale remediation would depend on cost and feasibility of each treatment option.
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Remedial Approaches for Passive Management of PFAS Contaminated Groundwater, Surfacewater, Stormwater, and Sediment
John Collins, COO, AquaBlok, Ltd.
Abstract:
Background/Objectives. Managing media contaminated with low but measurable concentrations of PFAS can be a challenge due to the need for effective treatment at reasonable costs. Several sites with PFAS issues may require a solution that achieves measurable reductions without needing to meet a regulated level. The ability to implement a passive system for in-situ remediation of shallow groundwater, surface or storm waters, and impacted sediment could allow for a more sustainable, low-impact and lower cost approach. Lab and bench scale testing have been undertaken to evaluate the effectiveness and feasibility of several amendment media for use in a delivery technology to mitigate PFAS release via stormwater and groundwater-to-surface water discharge, and to provide important data to support a plan to pursue a full-scale/field application. The technology consists of coating effective amendments (such as powder activated carbon, RemBind® and FluoroSorb®) onto an aggregate carrier to create a composite particle that allows for targeted removal of PFAS compounds in a permeable treatment configuration. Other approaches being considered include capping shallow soils, creating a treatment zone above the water table, or direct application of the amendment to ponds/impoundments. The development and assessment of an in-situ remediation approach which allows for a more sustainable, low-impact, and lower cost approach that reduces human health and ecological risk would represent a useful tool in the remediation toolbox. Approach/Activities. Lab investigations assessed the PFAS adsorption kinetics and equilibrium capacity of the adsorbents, as well as the hydraulic conductivity and other relevant physical properties of the product. Water samples from several sites consisting of a wide range of PFAS concentrations and water quality, were used to rigorously evaluate and validate the properties of the media. Data from the lab tests provided generalized conditions to inform a flow-through permeable reactive barrier (PRB) treatment system concept that supported the installation of a pilot system aimed at addressing the release of shallow GW to a receiving stream. The preliminary configurations, conceptual approach, and limited performance data from a pilot-scale evaluation of the passive treatment approach will be presented. Results/Lessons Learned. The development and implementation of a novel, passive adsorbent system at addressing PFAS migration via stormwater/surface water/groundwater was undertaken and data are being collected and will be evaluated. The particle system used consists of a proven powdered amendment for PFAS was implemented in a passive, flow-through treatment system. Preliminary results indicate that significant PFOS and PFOA removal is being achieved, however more data needs to be collected to support the development of a full-scale system that can address a significant range of rain events.
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Four-year Column Study Demonstrates the Reactivity and Persistence of Sulfidated Zero Valent Iron
John Freim, Director Material Science, Regenesis
Abstract:
Sulfidated microscale zero valent (SZVI) is an in-situ remediation product capable of eliminating toxic groundwater contaminants through direct chemical reduction. A key feature of SZVI is its core shell configuration with particle interiors consisting of zero valent iron and a surface layer consisting of reduced iron sulfide. The sulfidated surface effectively inhibits the hydrolysis reaction of ZVI and water and enables the preferential reduction of contaminants. Together these result in improved longevity compared to bare, unsulfidated ZVI products. Sulfidation also increases reaction kinetics by over an order of magnitude for common groundwater contaminants including chlorinated ethenes such as trichloroethylene (TCE). A column study was undertaken to evaluate the performance and longevity of SZVI Over the course of the experiment, dissolved phase trichloroethene was continually passed through four soil columns: one that was sterile with no additives, one with biological additives alone, one with SZVI alone, and one combining SZVI and biological additives. Remediation efficiency was evaluated by measuring concentrations of TCE and the daughter products cis-dichloroethylene and vinyl chloride (cDCE and VC) in the effluent. For the SZVI alone column, a 2 mg/L TCE solution in deoxygenated water was initially used and as the experiment progressed, the influent was increased to 20 mg/L TCE with oxygenated water to better understand of the capabilities of the product. Even after stressing the system, no significant breakthrough of TCE or daughter products was observed until the end the 4-year experiment; verifying the exceptional reactivity and persistence provided by sulfidated zero valent iron.
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Challenges to Preparing Remedial Cost Estimates for PFAS Sites
Dave Hempleman, P.E., Environmental Remediation and Compliance Engineer, Partner Engineering and Science, Inc.
Abstract:
Per- and polyfluoroalkyl substances (PFAS) refers to an entire class of substances that includes perfluorooctane sulfonate (PFOS) and perfluorooctanic acid (PFOA). This presentation will describe some of the challenges for estimating a range of remediation costs at PFAS-contaminated sites, supported by assumptions in a regulatory environment very much in flux. A Remedial Cost Estimate (RCE) is an important tool that brackets worst- and best-case cleanup costs for a contaminated property. The information used to estimate costs for remediation includes understanding the environmental fate and transport properties of the contaminant; chemical and physical data of the contaminated media; property size and use; and understanding the applicable regulations governing the requirements for contamination assessment, remediation, and closure. PFAS is a family of stable, recalcitrant chemical compounds that do not readily degrade under natural conditions. Estimating remediation costs for a property that is (or may be) contaminated by PFAS requires innovative solutions because the regulatory status of the contaminant is still emerging and PFAS is difficult to cleanup. The unsettled regulatory status of PFAS cleanup standards and very stable chemical structure of PFAS compounds affect the evaluation of cost-effective remedial alternatives and, ultimately, the selection and cost analyses of a range of potential remedial solutions.
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Treatment Success and Application Insights With Colloidal Activated Carbon For Hydrocarbon Plumes: A Multi-Site Review
Todd Herrington, Global PetroFix Prod Mgr, Regenesis
Abstract:
Colloidal activated carbon (CAC) is an emerging remediation amendment with a strong affinity for many toxic soil and groundwater contaminants. When combined with a destructive mechanism, it is possible to rapidly adsorb contaminants onto the carbon particles, with degradation accomplished through biological or abiotic processes. We will summarize twenty recent projects across North America where an engineered mixture of CAC and electron acceptors achieved site closure at most sites, often within a year and a single injection. Key application variables and ranges contributing to the portfolio’s success will be highlighted, including parameters such as injection spacing and injection pore-space filled. This poster will also highlight a recent Florida panhandle project where prior mechanical approaches could not achieve the Florida Department of Environmental Protection’s (FDEP’s) groundwater cleanup target levels (GCTLs). A PetroFix injection was used to reduce BTEX concentrations from over 2,000 ug/L to 1 ug/L or less for over 30 months and meet the criteria for closure. All UIC parameters were below background within two years.
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Accelerating Site Closure and Addressing Emerging Contaminants: ecoSPEARS' Innovative Environmental Remediation Technologies
Trevor Ludwig, Project Development Manager, ecoSPEARS
Abstract:
ecoSPEARS develops and deploys green, sustainable remediation technologies to extract and eliminate persistent organic pollutants (POPs) such as PCBs, dioxins, APIs, and PFAS from the environment. Through the exclusive license of the NASA-patented Sorbent Polymer Extraction and Remediation System (SPEARS) technology, ecoSPEARS offers innovative solutions for efficient and on-site remediation. The presentation will highlight ecoSPEARS' ability to address different needs such as expediting site closure through targeted remediation by deploying our various materials directly onto contaminated areas, significantly enhancing the efficiency of the cleanup process, minimizing the need for extensive excavation or transportation. This presentation will also address ecoSPEARS ability to remediate both emerging and legacy contaminants. The discussion will include data from recent treatability studies, featuring results from the recent 1,4-dioxane & PFAS studies for impacted soils & groundwater. Furthermore, the presentation will showcase successful remediation results achieved through on-site pilot deployments of the sediment and groundwater technologies, demonstrating their potential in addressing chemical contaminants and facilitating land reuse.
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Field Test of the New Direct Push Nuclear Magnetic Resonance Logging for Hydrogeologic
Dan Pipp, Direct Image - Environmental Chemist, GeoProbe
Abstract:
Nuclear magnetic resonance (NMR) technology has recently been adapted for advanced hydrogeologic investigations. A downhole NMR sensor directly measures a radio-frequency response from hydrogen in pore fluids. NMR signal amplitude is directly proportional to the quantity of moisture in the pore space and the signal decay time indicates the pore size, which is strongly correlated with hydraulic conductivity. Further, the distribution of decay times serves as a proxy for the saturated pore size distribution, a basis for classifying bound versus mobile fluid volumes. Empty 2.25in casing is driven to depth and the NMR logging tool is deployed out the bottom of the tool string. The borehole is then logged upon rod retraction. Estimates of porosity, hydraulic conductivity, moisture content, and bound versus mobile water have been compared to direct measurements on core samples and in-situ hydrogeologic testing. NMR estimates of hydraulic conductivity typically agree with other methods such as HPT dissipation and pneumatic slug tests.
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Quantitative High-Resolution Site Characterization (qHRSC) and Lessons Learned
Derek Pizarro, Senior Product Manager, AST Environmental, Inc
Abstract:
Background/Objectives. Limitations in funding or regulatory requirements often lead to soil and groundwater data gaps and an incomplete conceptual site model (CSM). An accurate CSM leads to better remedy selection, surgical application of the chosen remedy or remedies, shorter remedial timeframes, and lower overall remedial costs. One of the most common data gaps is limited speciated saturated soil analytical data and discrete assessment in underlying units. An integral approach to characterization and remediation is to obtain spatially and vertically dense soil analytical data and vertical profiling of groundwater; vertical groundwater profiling can effectively be twinned with high density soil sampling to determine contaminant mass distribution, gradients, and variability in aquifer properties due to geologic heterogeneity. These limitations also apply to transition zone and bedrock units but can be resolved with recent advances in procedures and methodologies. Approach/Activities. Most overburden injection via direct-push technology (DPT) is not adequate to capture the total contaminant mass present nor is the equipment effective for installation within the geologic medium. Improvements to overburden injection methodologies will be highlight the use of flexible overburden remediation units (low pressure/low flow to high pressure/high flow) combined with unique downhole tooling and field installation protocols to allow expert installation of all commercially available injectates. Additionally, subsurface conditions exist within the transition between overburden and competent bedrock lithologies that may prevent the use of traditional equipment or techniques to reach and isolate the targeted depth interval for assessment and treatment. These obstructions can be naturally occurring (hardpan/caliche, chert layers, dense fine-grained sediments, gravel, partially weathered rock, etc.) or anthropogenic (cut and fill, buried rubble like concrete, etc.). Development of the GeoTAP™ technique has provided both access for characterization and access to these intervals. It been used successfully on 50+ project sites across the country accessing depths as great as 180 feet below ground surface. This method characterizes these zones such that drilling is conducted like a bedrock application and injection is like overburden reactant/reagent installations. Finally, a key to bedrock remediation is not to just treat the highly transmissive zones. A combination of custom packers for discrete sampling and injection (18” between inflation elements) and a unique bedrock injection unit (flow rates ranging from 50 to 250 gallons per minute and pressures up to 2,700 psi.) allows focused treatment using high energy access to the smaller aperture fracture networks which typically contain more contaminant mass than more transmissive features. Being able to isolate and treat these zones is a key component to success at difficult fractured rock sites. Results/Lessons Learned. A comparative evolution of recent improvements to techniques and approaches to characterization and injection in overburden, transition zone/saprolite, and consolidated lithologies will be discussed. Site-specific case studies will illustrate the development of both quantified high-density data (CSMs) and focused in-situ remediation techniques. Lessons learned and relevant data will depict the benefits of high-density indiscriminate soil and groundwater sampling for quantitative lab analysis, then subsequent aggressive techniques to install the required in-situ treatment in targeted locations and loadings.
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12 Essential Leadership Skills Workshop
Bimal Shah, Rajparth Achievers, LLC
Abstract:
According to Entrepreneur Magazine, Management by leadership has been positively impacting many companies across the globe and it starts at the top. Attendees will walk away with: ✓ 12 Essential Skills needed to be an effective leader. ✓ How to apply at least three to five of those strategies in the next 30 days to your business and your leadership in the company. ✓ How to make employees “Feel” being a leader. ✓ FREE Tool on how to make your employees leaders and own their activities and their responsibilities every day with The Good job Measurer™ and other tools. ✓ FREE tools to build and practice leadership every day.
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Shallow Soil Remediation using the Landform Leveling Technique and Confirmation Testing
Steven Snyder, Senior Project Manager, Partner Engineering and Science, Inc.
Abstract:
Using satellite-guided agricultural heavy equipment, including loaders, scrapers, graders, and rome plow discs, remediate metals in shallow soils which pose an ecological or direct exposure risk. The efficacy of the landform leveling process is monitored in real time via x-ray florescence (XRF) testing and confirmed by EPA-approved laboratory analytical methods. The landform leveling process is effective at addressing large areas of soil impacts while limiting the volume of generated waste media.
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Real-Time Data Through Horizontal Soil Sampling for Optimized Horizontal Vapor Extraction Well Performance
Tomas Will, Senior Technical Environmental Scientist, Directional Technologies, Inc.
Abstract:
Background/Objectives. Further assessment and vapor mitigation were required at an industrial facility in the Northeast where subsurface impact from perchloroethylene (PCE) and trichloroethylene (TCE) resulted in conditions for potentially harmful vapor intrusion. The surrounding areas of the building had been fully assessed with vertical soil sampling methods; however, the area beneath the northern portion of the building had little assessment data due to the difficulties involved with accessing the sub-slab soil. Vertical borings through the floor of the facility were logistically impossible, and therefore horizontal soil sampling methods were selected for additional site characterization. The overall objective of the horizontal soil sampling was to provide immediate field data to delineate the extent of chlorinated solvent impact beneath the building. The data was then used to determine the optimal locations for installation of horizontal vapor extraction wells, thus completing assessment and installation in one mobilization. Approach/Activities. Collecting soil samples with directional drilling methods is not as simple as collecting soil samples through vertical drilling techniques. Similarly, to vertical soil sampling, the ground conditions of the target soils play a major factor in whether sample recovery is possible. Complicating assessment of the site was the underlying geology consisting of loose to dense clayey sand, and silty sand, with some gravel. Collecting soil samples in this type of formation can be difficult as gravel could block the sampling device, preventing sample recovery. As with vertical soil sampling, horizontal soil recovery can be difficult in formations which are too hard, too soft, or very saturated. A specialized horizontal soil sampling tool allows for the maximum soil recovery within difficult ground conditions. The specialized horizontal soil sampling tool is comparable to a 2-foot split spoon sampling device. Horizontal soil sampling was conducted at the facility to screen for the presence of elevated chlorinated VOCs. The soil samples were collected every 5-feet during soil boring advancement to delineate the extent of the source area beneath the facility. Results/Lessons Learned. Based on the analyses of the horizontal soil samples collected, the final target locations and screened intervals of the horizontal SVE wells were determined. Two horizontal wells were installed beneath the northern portion of the facility. The first horizontal SVE well was 75 feet in total length, installed to a final depth of approximately 22 feet BGS. The second horizontal SVE well was installed in an area of more significant chlorinated solvent impact; therefore, the second horizontal well was 90 feet in total length and extended to approximately 25 feet BGS. Without the ability to collect the horizontal soil samples, the optimal locations for the horizontal vapor extraction well screens may have been missed, resulting in an under-performing vapor extraction system with continued risk to the air quality within the building.
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