Geosyntec Practitioners to Present at EcoForum 2020
Geosyntec will deliver five presentations and one keynote at EcoForum 2020 eConference on September 14-18, 2020.
The Geosyntec presenters are Frederic Cosme, CPEng, Ir. (Australia), Jason Conder, Ph.D. (California), Robert Ettinger (California), Paul Nicholson, P.Eng. (Ontario), David Reynolds, Ph.D., P.Eng. (Australia), and Kathy Phillips, Ph.D. (Australia), Douglas Larson, Ph.D., P.E., LSP (Massachusetts), and David Adilman, P.G. (Massachusetts).
Frederic Cosme is a Principal Engineer based in Melbourne, Australia with more than 20 years of experience focused on environmental consulting and hydrogeology. Frederic helps clients convert scientific outcomes of investigations into practical remedial engineering design considerations and tangible risk-based results.
Jason Conder is a Principal Scientist based in California with more than 15 years of experience focused on risk assessment and contaminated sediments in contaminated site assessment and management, environmental toxicology, and ecological and human health risk assessment.
Robert Ettinger is a Senior Principal Environmental Scientist based in California with more than 20 years of professional experience focused on soil vapor extraction system design, vapor emission estimation, and subsurface contaminant vapor migration to indoor air.
Paul Nicholson is a Senior Engineer formerly based in Melbourne, Australia and now located in Canada. Paul has over 15 years of experience with the evaluation of vapor intrusion and has been integral in the development and implementation of many innovative assessment tools, such as high volume sampling, building pressure cycling, and mass flux evaluation.
David Reynolds is a Senior Principal Engineer and based in Sydney with more than 20 years of experience specialized in the development and implementation of groundwater remediation technologies and management strategies for complex sites with challenging hydrogeological conditions. He is the Australian Operations Manager for Geosyntec.
Kathy Phillips is a Senior Professional with Geosyntec Consultants in Melbourne. Her experience includes 10 years of consulting on contaminated site assessment and remediation, including several radiological sites, as well as human health risk assessment. She obtained her doctoral degree in Chemical Engineering from the University of Delaware with a focus on the behavior of chemicals in the environment.
Doug Larson is a Senior Principal Engineer based in Massachusetts with more than 30 years of experience focused on the investigation and cleanup of hazardous waste sites throughout the United States.
David Adilman is a Principal Geologist based in Massachusetts focused on the characterization and remediation of soil and groundwater as well as the design and implementation of large-scale construction dewatering and landfill monitoring programs.
For this year only, the Australasian Land & Groundwater Association (ALGA) has established a first ever virtual event-duo, which joins together a new New Zealand Land & Groundwater Conference, and EcoForum 2020. These events will explore how these countries solve difficult contaminated site problems and will present this along with approaches and solutions that are being applied internationally.
ALGA's mission is to promote the protection, restoration and management of land and groundwater for the benefit of human health and the broader environment across Australasia. ALGA pursues this mission through: facilitating and encouraging the expression and interchange of ideas, opinions and knowledge between stakeholders and other persons involved in contaminated land and groundwater; improving the capacity, knowledge and skills of persons working in the fields of contaminated land and groundwater industry; fostering honesty, integrity, rational thinking and professionalism in persons involved in the fields of contaminated land and groundwater; encouraging and supporting research and development of science and engineering that will advance the assessment, sustainable management and remediation of contaminated land and groundwater; and doing anything ancillary to the objectives.
Title: 20E016 - Practical Considerations on Resolving Groundwater and Surface Water Interaction at Contaminated Sites
Presenter: Frederic Cosme, CPEng, Ir. (Australia)
Coauthors: Matt Edwards (BlueSphere), Lange Jorstad (Geosyntec Consultants) and Greg Luke (BlueSphere)
Background/Objectives Practically resolving groundwater and surface water interaction is becoming an increasingly critical challenge at contaminated sites adjoining surface water bodies. This is particularly the case in Australia as substantial industrial development has occurred in close proximity to coastlines and rivers. However, most conventional approaches to evaluate groundwater – surface water interaction are not suited to the relatively small scale at which contaminated groundwater typically occurs as they have been developed for broader water resource studies at the catchment scale. Hence, there is merit in outlining a specific set of tools and approaches to improve the resolution of this challenge in a more practical manner, at a scale that is relevant to the typical exposure scenarios evaluated in risk assessments at contaminated sites.
Approach/Activities There is a growing range of tools and approaches available. Drive-point piezometers are typically deployed in soft sediments where the groundwater table is shallow. Seepage meters are well suited to near-shore environments, also favoring sites with soft sediments, and can provide direct measurements of discharge rates and composition. Depending on the temperature contrast between groundwater and surface water, portable or distributed temperature sensors can assist in locating and characterizing discharge zone(s). Passive flux meters can be deployed in monitoring wells provided the rate of groundwater discharge remains relatively constant during the deployment period. Applied and environmental tracers are very useful to assess the degree of groundwater – surface water mixing within aquifers prior to discharge, the surface water residence time in the hyporheic zone or the discharge rate when it is variable (e.g. tidal environments). Compound specific isotope analysis has proven to be valuable in demonstrating the role played by the hyporheic zone in acting as a natural bioreactor.
Results/Lessons Learned The paper presents examples of the use of these methods in contaminated site settings within Australia, including the results obtained and how they were used to further our understanding of environmental risk. The successful selection and implementation of these tools and techniques should consider the following at the investigation design stage:
- A plausible and robust hypothesis on the extent and nature of the groundwater – surface water interaction, as a component of a sound risk assessment. There is a higher chance of success if the tool selection and data collection is guided by the verification of this hypothesis with empirical data.
- The investigation design should aim to differentiate the contaminant loading attributable to groundwater – surface water interaction from other potential contamination sources affecting the receiving environment (e.g. off-site contribution, effluent discharge, sediment, air-borne deposition).
- The collection of high-resolution spatial and temporal data is critical to appropriately assessing what are often highly dynamic environments (for example, in tidally influenced zones where changes occur on an hourly basis).
- The best results are achieved through integration of multiple lines of evidence to resolve the dominant processes affecting contaminant fate and transport at the groundwater – surface water interface (physical, chemical and biological)
Title: 20E011 - Tools for Evaluating the Ecological Risks of Per- and Polyfluoroalkyl Substances at AFFF Sites
Presenter: Jason Conder, Ph.D. (California)
Coauthors: Jennifer Arblaster
Background/Objectives Perfluoroalkyl and Polyfluoroalkyl Substances (PFAS) have been widely used in numerous applications since the 1950s, including aqueous film forming foams (AFFFs) used for fire suppression at airports, firefighting training facilities, and other industrial locations. Many AFFF sites host ecological habitat, or, due to the offsite transport potential for PFAS, PFAS-impacted AFFF sites may affect nearby and downgradient habitats. Ecological Risk Assessments (ERAs) may be needed at these sites to facilitate decision making; however, the required supporting information and strategic guidance have historically been unavailable.
Approach/Activities As part of a United States Department of Defense Strategic Environmental Research and Development Program (SERDP) project, a guidance document was developed to provide a current state-of-the-practice overview of methods, practices, and key data gaps for assessing the potential for risks from exposure to PFAS for threatened and endangered (T&E) species at AFFF-impacted sites. The guidance is intended to provide the technical support to quantitatively evaluate ecological risks and enable site managers to make defensible, risk-based management decisions using the best available information and approaches. As an added effort to this guidance, which has been available since 2019, we have developed two Microsoft Excel based food web modeling tools based on the detail technical reviews included in the guidance. These Excel models allow a user to input concentrations of PFAS in abiotic media (i.e., soil, sediment, and water) and/or biotic media (i.e., tissue samples) to predict concentrations of PFOS in biota of aquatic and terrestrial food webs, concentrations of PFAS in the diets of vertebrate wildlife, and daily exposure estimates for vertebrate wildlife.
Results/Lessons Learned This presentation will provide information on how the user can access and download the free aquatic and terrestrial Excel modeling tools. In addition, we will provide a demonstration of the tools, including how they can be modified for evaluating the risks to Australasian wildlife. Based on model performance with real world data and additional experiences with ecological risk assessments conducted in Australasia and North America, it is apparent that at many sites, PFOS is commonly a key driver of risk-based concerns for ecological receptors. Along with highlighting these new tools for PFAS-focused ERAs, and current general lessons learned from their application, ongoing data gaps and research needs for PFAS ecological risk assessments will be discussed.
Title: 20E021 - Advantages and Limitations to Vapor Intrusion Modeling for Risk-Based Decision Making
Presenter: Robert Ettinger (California)
Background/Objectives Analytical and numerical models have been used to evaluate key fate and transport phenomena that influence the vapour intrusion (VI) pathway. Additionally, models are frequently used to quantify VI risks and develop corrective action goals. The utility of modeling for risk-based decision making has been questioned due to uncertainties associated with the accuracy of the model results. Models often fail to provide useful information when the conceptual framework for the model is inconsistent with site conditions (e.g., ignoring the effect of natural vadose-zone biodegradation on chemical fate) or model input parameters are not representative of site conditions. However, when appropriately applied, model can provide a useful line of evidence for VI assessments. This presentation will provide examples to illustrate how models can be effectively used in VI assessments while acknowledging their limitations.
Approach/Activities The first step in using a model for a VI assessment is to identify an suitable model that will capture the key characteristics of the site. Various models are available to evaluate the VI pathway, and it is important to understand their limitations when selecting the methodology to be used for a specific application. The next step is to determine technically defensible model input parameters based on site conditions that account for the variabilities and uncertainties of the various factors that influence VI. Understanding the sensitivities of each input parameter on model outcomes is a critical factor in the data evaluation process. Lastly, the uncertainties of the model output must be considered in the interpretation of the results for risk-based decision making.
Results/Lessons Learned VI model results can provide an effective additional line of evidence for evaluating the VI pathway at contaminated sites. However, it is important to understand the limitations of the models and confirm that appropriate input parameters based on site conditions are used. Also, the uncertainties of the model results should be recognized in the application of the modeling
Title: 20E020 - Building Specific Attenuation Factors for Vapor Intrusion Assessments
Presenter: Paul Nicholson, P.Eng (Ontario)
Background/Objectives In vapor intrusion (VI) assessments attenuation factors are the ratio of the indoor concentration of a contaminant to the subsurface concentration of a contaminant and account for reductions in concentrations which occur during transport of vapors from beneath a building to indoor air. When evaluating the potential risk to occupants within a building, attenuation factors are used to estimate the indoor air concentrations based on subsurface concentrations. The current National Environment Protection (Assessment of Site Contamination) Measure (ASC NEPM) incorporates a default attenuation factor of 0.1 when deriving the interim Health Investigation Levels (HILs) for chlorinated hydrocarbons. Empirical data from the USEPA indicates that this value could result in over 99% of vapor intrusion sites requiring additional investigations. A screening value that screens in almost every location is not practical. There are several approaches for developing more accurate building attenuation factors which will be discussed in this presentation.
Approach/Activities Australia has a limited data set on attenuation factors thereby resulting in the selection of an overly conservative value in the NEPM. One of the key aspects for the entry of vapors to a building are the various building specific factors, like building pressure, cracks, air exchange rates etc. Therefore, the determination of a building specific attenuation factor is a key to evaluating VI risk to occupants. There are some simple and robust methods which could be adopted by industry to better calculate attenuation factors. Approaches to building specific attenuation factors will be presented:
- The Johnson and Ettinger model and the range of assumed building values
- USEPA empirical attenuation factor database and selection of a conservative value of 0.03
- Indoor air and subsurface data forensics to determine building specific attenuation factors and differentiating background sources
- Subsurface pneumatic testing to calculate a building specific attenuation factor
- Radon as a potential tracer compound
Results/Lessons Learned The presentation will focus on the need for a change in policy with respect to the current NEPM attenuation factor value of 0.1 for subslab to indoor air. Building specific attenuation factors are generally orders of magnitude higher than the NEPM values and simple methods are available for developing building specific attenuation factors to show they are in the range of 0.03 to 0.0003.
Title: 20E019 - Bellevue 20 Years On - Taking the Final Steps to Closure
Presenter: David Reynolds, Ph.D., P.Eng. (Australia)
Background/Objectives Geosyntec was engaged to design, implement, monitor and validate an enhanced in situ bioremediation (EISB) remedy for a zone of groundwater impact in the vicinity of the former waste control site located in Bellevue, Western Australia. The overall objective of the remedial action was to design and implement an effective remediation program that permanently reduced the concentrations of the groundwater contaminants of concern (COCs; primarily trichloroethene [TCE]) to the appropriate risk-based criteria (at a minimum) in a cost-effective, sustainable and timely manner consistent with the expectation of community and relevant stakeholders.
Approach/Activities Preliminary work for the EISB remedy included installation of nine monitoring wells within the treatment area, and collection of baseline soil and groundwater samples. Following these activities, electron donor (emulsified vegetable oil) and a commercially available dechlorinating bacterial (bioaugmentation) culture (KB-1® Plus) were injected into the subsurface within the source zone (PTA) and a secondary bio-barrier (STA) located downgradient of the source zone to promote in situ biodegradation of the COCs in groundwater in these areas. Following the EISB injection activities, bi-annual groundwater sampling of 16 validation monitoring wells began and continued for a period of roughly 2.5 years (five total sampling events). Throughout the performance monitoring period, changes in the groundwater concentrations of total organic carbon, dissolved hydrocarbon gases, volatile fatty acids, nitrate, sulphate, dissolved iron, Dehalococcoides ethenogenes microorganisms, ORP, dissolved oxygen, as well as pH at some of the validation wells provided evidence that biologically active and reducing zones had been established in the PTA and STA.
Results/Lessons Learned Remediation of the PTA was considered complete when concentrations of TCE, cis1,2-dichloroethene (cis-1,2-DCE), and vinyl chloride (VC) in PTA validation monitoring wells fell below the remediation criteria for three consecutive monitoring events. This occurred in the fourth performance monitoring event. Concentrations remained below remediation criteria in all additional monitoring events. Remediation of the STA was considered complete when concentrations of TCE, cis-1,2-DCE, and VC in STA validation monitoring wells fell below the remediation criteria. This occurred by the fourth performance monitoring event. The validation report has now been approved by the Site Auditor and marks the first instance of successful Auditor approved bioremediation of chlorinated ethenes in Western Australia.
Title: 20E015 - Selection of a Uranium Immobilization Remedy Using Apatite at the Nuclear Metals, Inc. Superfund Site
Presenters: Kathy Phillips, Ph.D. (Australia), Douglas Larson, Ph.D., P.E., LSP (Massachusetts), and David Adilman, P.G. (Massachusetts)
Background/Objectives At the Nuclear Metals, Inc. (NMI) Superfund Site (Concord, Massachusetts, USA), depleted uranium (DU) was used to manufacture armor penetrators for the United States (U.S.) Army from 1958 to 1985. NMI disposed of process waste containing DU, nitric acid, and lime in an unlined basin within a property that is now bordered by residential and light commercial development. DU was released to soils and groundwater beneath and near the basin; subsequent removal of sludge from the bottom of the basin left behind residual soil contamination and a small but concentrated plume of DU in groundwater.
Geochemical data for soil and groundwater samples collected over the first five years of remedial investigation activities were used to develop a surface complexation model to predict subsurface DU transport in groundwater at the NMI Site. Concurrently, the U.S. Environmental Protection Agency (EPA) developed its guidance for monitored natural attenuation (MNA) of radionuclides which was issued in 2010. Based on the transport modelling results and the U.S. EPA MNA guidance, it was determined that an active remedy would be required to prevent DU migration in groundwater from reaching the Assabet River, which is approximately 350 meters downgradient of the basin where the DU was released.
Approach/Activities A feasibility study (FS) conducted to assess remediation strategies for DU-impacted groundwater identified sequestration of dissolved DU via the precipitation of stable uranyl phosphate (U-P) minerals as a viable alternative. Field column studies were conducted at two locations within the DU groundwater plume to assess the use of the fish bone-derived mineral hydroxyapatite to convert dissolved DU in groundwater to U-P. Based on the results of these studies, the FS concluded that hydroxyapatite is an effective material for in situ DU remediation that can be readily implemented, requiring no redox manipulation, and that it could provide significant cost savings over more active approaches. Following the FS, the U.S. EPA selected hydroxyapatite injection within the DU plume as the preferred remedy for DU- impacted groundwater at the NMI Site.
Results/Lessons Learned This presentation describes the conceptual design of the hydroxyapatite remedy to sequester DU in groundwater, including methods to inject powdered hydroxyapatite within the affected saturated zone soils. Predesign investigation activities to assess the effectiveness of different injection methods are about to begin pending relaxation of work restrictions associated with the COVID-19 pandemic; available data on injection method effectiveness through August 2020, and the anticipated impact of those data on the final remedial design, will be included in the presentation.
About the event: https://landandgroundwater.com/duo-econference-event
Event Program: Global Perspectives Locally Focused
About ALGA: https://landandgroundwater.com/page/vision-mission
Learn more about David Reynolds: https://www.geosyntec.com/people/david-reynolds