Geosyntec professionals will make a significant technical contribution to the 33rd Annual International Conference on Soils, Sediments, Water, and Energy at the University of Massachusetts in Amherst from October 16-19, 2017.
Geosyntec will lead a workshop, deliver two platform presentations, four poster presentations. Jessica Yeager serves on the Scientific Advisory Board (SAB).
The conference is presented by The Association for Environmental Health & Sciences Foundation (AEHS), and is expected to have over 200 poster presentations, 80 posters, six workshops, and 48 exhibitors. The Annual Conference on Soils, Sediments, Water and Energy has become the preeminent national conference in this important environmental area. The conference attracts 600-800 attendees annually which includes a wide variety of representation from state and federal agencies, military, industry (including railroad, petroleum, transportation, and utilities), environmental engineering and consulting, and academia.
The AEHS is a non-profit, member-supported, professional organization. Their purpose is to facilitate communication and foster cooperation among professionals concerned with the challenge of soil, sediment and water assessment, cleanup, and protection. According to the AEHS Foundation, resolutions for environmental contamination can be found only through the integration of scientific and technological discovery, social and political judgment, and hands-on practice. AEHS Foundation facilitates conferences, seminars, publications, collaborative partnerships, and a members-only online community.
Title: Sustainable Remediation: Frameworks, Tools, and Case Studies
Time: Monday, October 16, 1:00pm – 5:00pm
Location: Room 169
Anne Fitzpatrick, Geosyntec, Seattle, WA; Sabine E. Apitz, SEA Environmental Decisions, Hertfordshire, United Kingdom; David Harrison, NERA Economic Consulting, Boston, MA; Amanda McNally, Geosyntec Consultants, Pittsburgh, PA; Thomas Potter, Massachusetts Department of Environmental Protection, Boston, MA
Although guidance for sustainability considerations has been progressing from recommending best management practices (BMPs) to optimization of selected remedies to guidance on remedy selection, the focus remains on green remediation, or footprint reduction, rather than a full consideration of sustainability. A number of initiatives, frameworks, and tools have been developed, regionally, nationally and internationally to address the need to incorporate a holistic sustainable remediation approach when evaluating and selecting remedial alternatives. The workshop objective is to discuss regulatory drivers, concepts, tools and frameworks for the assessment, selection, and optimization of sustainable remediation options. A range of approaches will be reviewed, using the recently developed sustainability framework applied in the Portland Harbor Superfund Site Sustainability Project (PHSP), as an example of how emerging environmental, economic and social tools for evaluating and communicating the impacts of remedial alternatives can be used in support of decision making. Workshop participants will learn how sustainability concepts can be incorporated into site cleanups. The discussion will identify how these tools can be adapted to small and large-scale sites under a range of regulatory drivers, using a tiered approach. A focus will be the consideration of how differing stakeholder priorities affect outcomes; and how stakeholder value-linked sustainability analysis can identify trade-offs and points of contention, providing a systematic, transparent tool for community engagement. An interactive element will be included, where workshop attendees work through a demonstration of this process.
Title: Use of Mass Loading Assessment to Characterize Vapor Intrusion Potential
Time: Thursday, October 19, 9:00am – 9:30am
Location: Room 168
Presenter & Co-authors: Theresa Gabris, Geosyntec Consultants, Washington, DC; William Wertz, Geosyntec Consultants, Inc., Castleton, NY; Todd McAlary, Geosyntec Consultants, Inc., Toronto, ON, Canada; Darius Mali, Geosyntec Consultants, Inc., Guelph, ON, Canada; Daniel Carr, Sanborn, Head and Associates, Inc., Dayton, ME
The characterization of vapor phase VOC mass loading (VOC mass flux multiplied by building footprint area) offers a promising alternative to conventional indoor air and sub-slab sampling because mass loading results have been found to exhibit considerably less temporal variability than conventional indoor air samples. Three mass loading estimation techniques were employed as part of an ongoing ESTCP VI research project (ER-201503) to assess the VI potential at a former dry cleaning facility at Vandenberg Air Force Base. One technique used groundwater, soil and soil vapor data to characterize the mass loading potential associated with the presence of PCE, TCE and cis-1,2-DCE in the vadose zone beneath the building (MFsoil). Those loading estimates were compared with loadings determined through temporary operation of a sub-slab ventilation system (MFSSV) that captured vapors below the building, and indoor loadings associated with sub-slab vapor entry induced during building pressure cycling (MFBPC) via a blower door. In addition, the blower door fan was used to pressurize the building and inhibit sub-slab vapor entry in order to assess the mass loadings attributable to residual indoor sources of VOCs. Cross-slab and cross-building differential pressure measurements were used in conjunction with the MFBPC results to develop building leakage and mass loading curves for use in estimating reasonable maximum exposure (RME) concentrations and calculating the building-specific magnitude of sub-slab vapor attenuation under natural and depressurized conditions. The results from each approach are presented and compared with historical VI characterization data from the building as well as the results of similar mass loading estimates from other buildings where these techniques have been used.
Title: Vapor Intrusion Source Investigation Technique to Support Rapid Response Scenarios
Time: Thursday, October 19, 11:30am – 12:00pm
Location: Room 169
Presenter & Co-authors: David Jensen, Geosyntec Consultants, Acton, MA; Todd Creamer, Geosyntec Consultants, Portsmouth, NH
Some vapor intrusion (VI) pathway investigations require results on short timelines, including commercial property transactions and exposure scenarios related to trichloroethylene (TCE). Evaluating large buildings under these conditions can be challenging using traditional discrete sub-slab soil gas sampling. High Volume Sampling (HVS) is an innovative investigation technique, which can rapidly and more costeffectively increase confidence in identifying contamination sources beneath a building slab than by traditional methods. Traditional sub-slab sampling may only involve screening 5 to 10 liters of soil gas. To increase confidence that all significant sources have been identified can require using very large numbers of such discrete sampling locations. In contrast, one HVS test is typically used to screen between 10,000 and 100,000 liters of soil gas covering an area of several thousand square feet. By screening soil gas during an hour-long test, spatial trends of common soil gas parameters are generated. Analysis of these trends can discern information about the presence, magnitude, and geometry of sources beneath the building slab. Additionally, the HVS testing facilitates collection of pneumatic data, which can be used to identify and test preferential pathways, to estimate slab leakage, and to collect design criteria for targeted mitigation system design.
Title: Multi-Faceted Remediation Strategy for Tetrachloroethene in a Complex Urban Environment
Presenter & Co-authors: Alice Blayney and Julianna Connolly, Geosyntec Consultants, Brookline, MA; Erin Kirby, Geosyntec Consultants, Bedford, NH; Douglas Larson, Carl Elder, and Christopher Arsenault, Geosyntec Consultants, Acton, MA
Historical operations at a dry cleaning facility in a mixed-use urban setting introduced tetrachloroethene (PCE) to the subsurface beneath the dry cleaner building and an adjacent four-lane roadway. PCE containing wastewater was discharged from the building into a leaky sewer lateral that extended from the dry cleaner to a storm drain under the adjacent four-lane roadway. Remediation was complicated by the high-traffic urban environment and multiple utilities beneath the roadway. Construction of a nearby building with a deep slurry wall foundation divided the source area from a large section of the downgradient plume, providing an opportunity to treat the two areas separately using multiple sustainable remediation strategies.
The source area was treated using enhanced in situ biodegradation (EISB) and targeted soil excavation. EISB amendments were distributed to the subsurface using multiple methods including injections in the four-lane roadway, recirculation of amendments beneath the dry cleaner foundation slab, and injection of amendments through the leaky sewer lateral, after the connect to the main sewer was plugged. Additionally, a temporary groundwater capture and treatment system (GCTS) was installed adjacent to the downgradient slurry wall to establish hydraulic control of source area groundwater while source area treatment was ongoing. Treated groundwater was supplemented with an electron donor to remove nitrate and reinjected downgradient of the slurry wall, resulting in enhanced flushing of the plume's toe.
Tailoring a variety of remediation strategies to this complex urban site resulted in an effective remedy with a small carbon footprint. Installation of the temporary GCTS and implementation of EISB were concurrent with planned capital improvements, resulting in reduced marginal cost for remedial construction. The combination of EISB, hydraulic control, enhanced natural attenuation, and targeted soil removal have reduced the mass of chlorinate ethenes to concentrations where active systems will not be necessary to achieve regulatory closure.
Title: Adjusting Analyte Concentrations in Groundwater Samples Using Potassium Bromide to Account for Drilling Water Dilution
Presenter & Co-authors: Dariusz Chlebica, David Adilman, Christopher Arsenault, and Carl Elder, Geosyntec Consultants, Acton, MA; Bruce Thompson and John Hunt, De Maximis, Inc., Windsor, CT
Many drilling methods add water to lubricate and cool the drilling bit, remove cuttings and/or maintain hydraulic pressure on the formation to prevent influx of "heaving" sands. Typically, some water used during drilling is lost to the formation which can be problematic when groundwater profiling is used to assess contaminant concentrations during drilling. To ensure samples representative of only groundwater are collected, it is common to pump from the sampling point 1 to 5 times the volume of water lost to the formation before collecting samples. Alternatively, tracers can be mixed into the drilling water and the boreholes are pumped until the tracer concentrations are sufficiently low. A novel method using potassium bromide as a tracer was developed for the PushAhead™ profiler designed by Cascade Drilling, LP. For this approach, drilling water with a known concentration of potassium bromide is used, and the concentration of the potassium bromide is measured in each groundwater sample. The ratio of bromide in the sample relative to bromide in the drilling water is used to calculate a "dilution factor" that is used to adjust analyte concentrations in the sample to account for dilution from drilling water. The method provides more reliable analytical data for decision-making (e.g., ensuring monitoring well screens are in the intervals with most significant contamination). This approach also eliminates purging prior to sampling, minimizing waste generation and decreasing drilling time. The potassium bromide is recovered during well development following monitoring well installation. The method was approved by EPA and MassDEP for use in a wellhead protection zone. Using this approach, the vertical and horizontal extent of overburden 1,4-dioxane and VOCs plumes were delineated allowing optimal screen placement for 15 monitoring wells within a 90 foot-thick stratified drift aquifer at a Massachusetts CERCLA site.
Title: Jet Injection Emplaced mZVI Treatment of TCE in Clay Till: Two Years of Performance Monitoring
Presenter & Co-authors: Dylan Eberle and Chapman Ross, Geosyntec Consultants, Acton, MA; Neal Durant, Geosyntec Consultants, Washington, DC; William Slack, FRx, Cincinnati, OH; Peder Johansen, Capital Region of Denmark, Hillerød, Region Hovedstaden, Denmark; Eline Begtrup Weeth and Torben Højbjerg Jørgensen, COWI A/S, Odense City, Odense, Denmark
Direct-Push Technology Jet Injection (DPT-JI) is a treatment strategy that can overcome the challenges of treating chlorinated solvents in low-permeability formations. This patent-pending injection method combines high pressure jetting (10,000 psi) and controlled hydraulic fracturing for emplacement of amendments into geologic matrices where remediation is limited by contact between reagents and solvents trapped in the matrix. In this study DPT-JI was used to emplace zero valent iron (mZVI) into a clay till source zone in Nivå, Denmark (the Site) for in-situ chemical reduction of chlorinated solvents. The target treatment area (TTA) at the Site is approximately 750 m2 and 6 to 12 meters below ground surface (mbgs). Trichloroethene (TCE) is the primary contaminant of concern, with concentrations as high as 83 mg/kg observed during the baseline soil characterization.
In November 2014, 49 tonnes of mZVI was injected into the TTA. Results indicate that this new injection method can consistently create subhorizontal mZVI zones with a radius of influence of at least 3 m and depth spacings of 0.5 and 1 m. During the first two years of performance monitoring, strongly reducing conditions have been observed within the TTA. After 18 months, the estimated mass of TCE in TTA soils decreased approximately 85% from 29.3 kg to 4.5 kg. Reductions of TCE in post-injection soil cores are typically coincident with observed mZVI filled fractures. Groundwater data indicate that the TCE mass discharge from the source area has decreased by over 70% two years post-injection. Significant ethene and ethane production, up to 3.6 mg/L ethane, has been measured in the TTA demonstrating complete TCE degradation. Although three more years of performance monitoring are planned, the findings to date show that DPT-JI emplaced remedies can achieve significant degradation of chlorinated solvents in lowpermeability soils that are largely inaccessible to conventional injection technologies.
Title: Evaluating the Shutdown of Sub-Slab Depressurization Systems Downgradient of a Former Drum Burial Site
Presenter & Co-authors: Shahen Huda, Joseph Jeray, and Chapman Ross, Geosyntec Consultants, Acton, MA; Julianna Connolly, Geosyntec Consultants, Brookline, MA
After completion of groundwater remediation, Geosyntec conducted shutdown tests to demonstrate that active sub-slab depressurization (SSD) systems were no longer needed to mitigate vapor intrusion at three buildings downgradient of a Former Drum Disposal Site. Concentrations of volatile organic compounds (VOCs) in shallow groundwater near each building have decreased due to groundwater remediation activities at the Site, and we hypothesized that VOCs migrating from shallow groundwater to indoor air may no longer pose an unacceptable risk. SSD systems are installed in a commercial office building and two residential buildings, including a duplex with separate SSD systems in each unit's basement.
Shutdown tests were conducted to evaluate indoor air VOC concentrations when the SSD systems were not operating. Multiple tests were completed for each SSD system in accordance with MassDEP guidance. The shutdown tests involved shutting down each SSD system for at least one week to allow conditions to equilibrate. Indoor air samples were then collected. For selected tests, sub-slab soil gas samples and groundwater samples were also collected. Groundwater samples were collected periodically throughout the SSD operational period.
Indoor air and sub-slab soil gas results from the shutdown tests were compared to regulatory threshold values and risk management criteria. Results were also compared to concentrations in samples collected before the installation of each SSD system. Trends in indoor air and soil gas concentrations, and their relationships to groundwater concentrations, were also evaluated.
The SSD system shutdown tests were an effective application of the MassDEP Vapor Intrusion Guidance to limit the duration of active SSD operation. This project is a case study for using SSD systems as an interim measure rather than a permanent engineered control requiring long-term operation and maintenance. The data evaluated here can be used to inform decision-making at similar sites about the effects of source remediation on downgradient receptors.
Learn more about the event at: http://www.aehsfoundation.org/east-coast-conference.aspx.
Learn more about AEHS at: http://www.aehsfoundation.org/.