Groundwater Solutions: Innovating to Address Emerging Issues for Groundwater Resources Conference: Alphabetical Content Listing
Contaminated Large Plumes Part I
Scott Potter, Ph.D.
Adaptive Design to Complete Remediation of Cr(VI)-Impacted Groundwater to Drinking Water Standards
Frank Lenzo
Site-wide remediation services were performed under a fixed-price contract to achieve regulatory closure where former industrial operations resulted in chromium impacts to soil and groundwater. The initial groundwater remedy implemented from 1994 to 2007 consisted of a network of up to 14 extraction wells situated throughout the plume. While the initial extraction system achieved hydraulic containment, the design did not significantly achieve concentration reductions or plume footprint contraction. Full-scale in-situ groundwater remediation was conducted at the site from April 2008 to September 2017 over 10 operational phases over two hydrostratigraphic units. Cr(VI) concentrations have been reduced from baseline concentrations greater than 10,000 micrograms per liter (µg/L) in the source area to below cleanup goals (10 µg/L) throughout the plume. Successful remediation of Cr(VI) in groundwater was achieved through adaptive operation that enhanced groundwater gradients and associated mass flux within discrete treatment cells, established robust in situ reactive zones capable of in-situ Cr(VI) reduction, and proactively optimized system operation in response to treatment performance. The adaptive approach employed in this case study can be applied to achieve substantial reduction in lifecycle costs for groundwater remediation of a broad range of contaminants amendable to enhanced extraction and biogeochemical fixation through in-situ remediation.
Adaptive Site Management at Complex Sites
Elisabeth Hawley
An Interstate Technology & Regulatory Council (ITRC) team recently prepared technical and regulatory guidance on “Remediation Management of Complex Sites”. This presentation will highlight the contents of the guidance with a focus on adaptive site management as a process for managing remediation at complex sites. Other relevant initiatives, including EPA’s pilot program on adaptive management, will also be summarized.
The ITRC guidance can help regulators and project managers understand and apply adaptive site management principles and develop a long-term site closure strategy at complex sites. The guidance describes site challenges and how to integrate them into a conceptual site model, conduct a remediation potential assessment, integrate adaptive site management concepts into a remedy design or remedy transition, set interim objectives and performance metrics, prepare components of a long-term management plan, and set decision criteria for adjusting, optimizing or reevaluating remedy performance. Numerous case studies describe real-world applications of remediation and remediation management at complex sites. The guidance also describes techniques for effective stakeholder engagement at complex sites.
Biological Treatment of Mixed SVOCs Including 1,2,3-trichloropropane and 1,4-Dioxane
Mark Klemmer
Groundwater in three separate transmissive zones at the site of a former chemical production plant in Mississippi contains several volatile and semi-volatile organic compounds (VOCs and SVOCs) in the parts per million (ppm) range. The pilot test was conducted on water with up to 140 ppm 2-chloroethanol, 70 ppm bis(2-chloroethoxy)methane (BCEM), 21 ppm 1,2-dichloroethane (DCA), 13 ppm ethylene glycol, 11 ppm 1,2,3-Trichloropropane (1,2,3-TCP), 3.4 ppm 1,4-dioxane, and minor (<1.0 ppm) concentrations of bis(2-chloroethyl)ether (BCEE) and minor concentrations of several other organics and VOCs. Dense non-aqueous phase liquids (DNAPLs) are present in two distinct areas of the upper aquifer, consisting of varying concentrations of the contaminants of concern (COCs). Hydrochloric acid was used in the former plant’s production processes, with historic releases resulting in depressed groundwater pH as low as 3.5, and dissolved iron concentrations as high as 400 ppm. An interim groundwater pump and treat system has been operating at the site, providing hydraulic containment of the impacted groundwater plume as well as pretreatment prior to discharging to a publicly owned treatment works (POTW). Both aspects of the planned remedy require a reliable treatment system with a high degree of COC removal.
Characterization of a Large Hexavalent Chromium and PFAS Plume in Fractured Bedrock
James Doherty, PhD, PE, LSP
Hexavalent chromium and per- and polyfluoroalkyl substances (PFAS) were released to fractured bedrock by a chromium plating facility. Sampling for these materials in monitoring and residential water wells determined that the extent of groundwater impacts was approximately one square mile extending to a depth of over 400 feet. The results of investigations conducted at the site indicate that it is likely that a significant portion of the area was not impacted by the release but can instead be attributed to background conditions.
The investigations focused on collecting several lines of evidence to distinguish between site impacts and background conditions. Multiple rounds of groundwater samples were collected and analyzed for metals, PFAS and other organic compounds. To evaluate groundwater migration pathways site investigations included conducting surficial and down-hole geophysical investigations, packer testing and pumping tests to evaluate the hydraulic characteristics and fracture interconnectivity of the bedrock.
Lines of evidence used to distinguish between areas impacted by the release and background areas include: characterization of the fractured bedrock groundwater flow, hexavalent to total chromium ratios, PFAS fingerprinting, changes in groundwater physical conditions, groundwater anionic and cationic composition, and characterization of the composition of the rock matrix.
Innovative Solutions to Challenges of a Long-term Groundwater Remediation and Municipal Water Supply Program
Jeff Biggs
The Tucson International Airport Area Groundwater Remediation Project (TARP) is a Federal Superfund large groundwater plume remediation program that has produced municipal drinking water for the City of Tucson, Arizona’s water customers since 1994. Throughout TARP’s 25-year history, Tucson Water has operated two remediation wellfields and a water treatment plant (WTP) to treat volatile organic chemicals (VOCs), primarily trichloroethene (TCE). In 2002, a second water quality challenge surfaced when 1,4‑dioxane was first detected in TARP groundwater. Tucson Water initially managed 1,4-dioxane concentrations by blending TARP treated water with other potable water sources while studying effectiveness of advanced oxidation processes (AOPs). When EPA reduced the Drinking Water Health Advisory levels for 1,4-dioxane by nearly an order of magnitude in 2011, the blending approach was no longer viable, and Tucson Water completed design and construction of a UV-hydrogen peroxide AOP facility in early 2014. Having solved the TCE and 1,4-dioxane challenges, Tucson Water is now faced with its third water quality challenge at TARP due to PFOA/PFOS levels above EPA’s Drinking Water Health Advisory published in May 2016, along with ongoing operation, maintenance, and replacement challenges for aging wells. This presentation reviews TARP’s history and details its challenges and evolving innovative solutions.
Remediation of Chemical and Radioactive Contaminants from Groundwater of Hanford Site Nuclear Facility, WA, USA
Dibakar Goswami
The Hanford nuclear operations and chemical separations processes supported the generation of plutonium for the Cold War and left world’s most complicated “problem areas” of contaminated soil and groundwater. At present, about 105 square kilometers of groundwater beneath the Hanford Site are contaminated above the state and federal drinking standard. In the early nineties, a comprehensive site wide groundwater remediation strategy included goals to address various contaminated plumes of hazardous and radioactive waste to protect the adjacent Columbia River and the overall reduction of immediate risk to the human health and the environment. It addressed major plumes found in the reactor areas adjacent to the Columbia River to protect the river from contaminants of chromium, strontium-90, and uranium. It also included containment of major plumes found in the central plateau region that contain chlorinated solvents and radionuclides so that these plumes never reaches the Columbia River. To meet these goals, active groundwater remediation systems are placed using the state of the art pump and treat systems to capture all the mobile contaminants covering organic, inorganic and radioactive constituents. Innovative technologies such as sequestration technologies for the strontium-90 and Uranium are deployed to address complex groundwater problems.
Targeted 3D Plume Analyses: Assessing Boundary Control on Large Complex Sites
Eryn Torres
Boundary control of dissolved-phase groundwater plumes can be assessed by examining the concentration changes in individual wells, but these trends can be difficult to interpret, especially for large sites, since their evolution in three-dimensions (3D) over time is complex. A more descriptive and comprehensive plume stability characterization method is designed to address this complex issue, by advancing the 2D moment analysis found in the Monitoring And Remediation Optimization System (MAROS) software (GSI, 2012). This new method examines changes over time in the overall mass, the migration of the center of mass, and the dispersion of mass in 3D. The new method leverages the 3D volumetric interpolation capabilities of Earth Volumetric Studio (C Tech, 2018) with Python automation to interpolate and calculate mass distributions of years of sample concentrations using thousands of wells. This method is used on subareas of a large Superfund site in California to assess the effectiveness of boundary control of migration of multiple analytes. The results of these subarea plume stability analyses are confirmed by separate mass flux analyses. The method has been approved by the EPA and provides an additional line of evidence to assess the adequacy of the boundary control system for meeting site objectives.
Emerging Contaminants Panel: Making Good Decisions with Limited Data and Great Uncertainty
Jeff Biggs
Emerging Contaminants Part I
Patricia Reyes
Effectiveness of In Situ Colloidal Activated Carbon Treatment to Mitigate PFAS Migration in Groundwater on DoD Site
Ryan Moore
Camp Grayling in Crawford County, Michigan is a training center for the Michigan Army National Guard. In 2016, the DMVA became aware of the potential contamination of PFAS from operations such as onsite firefighting training activities and began testing. PFAS was found commingled with a chlorinated solvent plume that was migrating towards the property boundary. The DMVA reviewed potential remedial options to test in the field such as pump and treat, but ultimately decided to test an in-situ reactive barrier application of colloidal activated carbon, an approach that is first of its kind in the State of Michigan.
Colloidal activated carbon was selected because of the rapid reductions of PFAS by removal from the dissolved mobile phase. Colloidal activated carbon effectively increases the retardation factor of PFAS migration contaminants by multiple orders of magnitude and eliminates the exposure to down-gradient receptors. In addition, colloidal activated carbon was selected due to its expected lower project costs when compared to operating a mechanical system.
This presentation will review the project design considerations, field activities, and post- application data. Additionally, the presentation will answer questions related to the distribution of the colloidal activated carbon in the subsurface and expected long-term efficacy.
Eliminating Risk of Exposure to PFAS in Groundwater: Full Scale In Situ Remediation with Colloidal Activated Carbon
Scott Wilson
Colloidal activated carbon (CAC) is emerging as a low cost, effective method for the in situ remediation of PFAS in groundwater. CAC can be readily emplaced into an aquifer and coat the high flux zones to create an in situ, permeable sorption barrier which purifies the passively migrating groundwater. PFAS constituents from up-gradient source zones are rapidly sorbed to the activated carbon and removed from the mobile dissolved phase, eliminating the route of exposure to down-gradient receptors and thereby also eliminating the public health risk associated with PFAS exposure.
Data will be presented from several field case sites at which a single application of colloidal activated carbon resulted in reduction in PFAS groundwater concentrations by several orders of magnitude, bringing them below USEPA health advisory levels. CAC isotherm data and sorption test data will also be presented for specific PFAS compounds indicating excellent sorption capability and increased performance with decreasing carbon particle size. Additionally, plume modeling will be presented indicating the longevity of in situ colloidal carbon treatment for PFAS to be on the order of multiple decades before reapplication is required.
Enhanced Degradation of Chlorinated Solvents Through Combined Colloidal Activated Carbon Remedies
Maureen Dooley
Colloidal activated carbon suspensions allow for low-pressure injection and uniform distribution of solid-state reagents. Zero valent iron (ZVI) has long been used as a solid-state reagent for reactive barriers in the treatment of chlorinated solvents. The development of colloidal activated carbon (PlumeStop) has demonstrated its ability to act as a passive barrier while treating chlorinated solvents. With the introduction of colloidal ZVI (AquaZVI), these two reagents may be co-applied. This innovative combined remedy allows for a duel approach and the rapid removal of contaminants, providing long term in-situ treatment with a single application of the amendments.
The project site contained petroleum hydrocarbons, chlorinated ethenes and ethanes in the sub-surface. This pilot event aimed to create a reactive barrier wall for protection of downgradient residential wells from migrating contamination.
The project site contained petroleum hydrocarbons, chlorinated ethenes and ethanes in the sub-surface. This pilot event aimed to create a reactive barrier wall for protection of downgradient residential wells from migrating contamination.
Enhanced Reductive Dechlorination and Electrical Resistance Heating Reduces Plume
Glenn Iosue, P.E., BCEE
A dry cleaning facility operated from 1947 to 2014. Fugro was retained by California Department of General Services to assess conditions, address risks posed, and to remediate the Site to allow redevelopment. The facility used a variety of dry cleaning solvents including tetrachloroethene (PCE) and the petroleum-based Stoddard Solvent. Contaminant plumes of the various chemicals of concern (COCs) are commingled onsite.
The Site is located in a dense urban setting with low income and market rate housing, restaurants and a child care facility as direct neighbors. Subsurface conditions at the Site are complex with sandy silts, dense silts, silts and clays, silty sands, and cobble/boulders. Based on the soil matrix, three water bearing zones were identified. Fugro’s focus was on the shallow groundwater because it is the source of vapor intrusion risk. The groundwater plume has been delineated to extend below several city blocks presenting unique challenges in development of the Conceptual Site Model.
The Site is located in a dense urban setting with low income and market rate housing, restaurants and a child care facility as direct neighbors. Subsurface conditions at the Site are complex with sandy silts, dense silts, silts and clays, silty sands, and cobble/boulders. Based on the soil matrix, three water bearing zones were identified. Fugro’s focus was on the shallow groundwater because it is the source of vapor intrusion risk. The groundwater plume has been delineated to extend below several city blocks presenting unique challenges in development of the Conceptual Site Model.
Lessons Learned from PFAS Analysis of Groundwater at Multiple Sites
Jack Sheldon
Background. Groundwater collected from 19 US sites with past use of aqueous film forming foam (AFFF), and analysis of per and polyfluoroalkyl substances (PFAS) provides opportunity for trend analysis and lessons learned. During the sampling program, 72 groundwater samples were collected using the same sampling method and analyzed by the same analytical laboratory on the same brand of AFFF. Yet, lack of an apparent data trend suggests there are other influences on the suite of PFAS detected in groundwater.
Approach. Over a three-year review period, potential PFAS source areas from past AFFF use were identified at hundreds of sites in the mid-west and surveyed. Nineteen sites were selected for further PFAS source, nature and extent investigations based on risk to a potential sensitive receptor.
Results/Lessons Learned. Details of the sampling programs and the challenges of sampling under complex scenarios will be discussed. Graphical presentations of the data and trend analysis will be provided to identify possible causes for the wide variation of PFAS suites detected in groundwater from the same AFFF. The viability for and challenges surrounding PFAS source fingerprinting will be discussed.
Sorptive Removal of F-53B from Water by Sodium Dodecyl Sulfate Modified Layered Double Hydroxide
Xin Song, Ph.D.
The phase out of perfluorooctane sulfonate (PFOS) promotes the production and use of its alternatives, one of which is chlorinated polyfluorinated ether sulfonate (trade name F-53B). F-53B has been widely detected in various environmental matrices and has been reported to have equal or higher health risks than PFOS. Therefore, developing effective remediation strategies for F-53B removal is essential. In this study, we develop a rapid and effective sorbent, i.e. sodium dodecyl sulfate modified layered double hydroxide (SDS-LDH), for the sorptive removal of F-53B from water. SDS-LDH can remove F-53B within 15 min while having a sorption capacity of over 950 mg/g. Moreover, it can keep ~60% removal of F-53B in the presence of excessive co-existing CO32- (the molar ratio of CO32-/F-53B is 28534) which has the strongest host−guest electrostatic interactions with SDS-LDH. Sorption mechanisms of F-53B by SDS-LDH include ion pairing/exchange, hydrogen bond and hydrophobic binding. The results of density functional theory highlight the vital role of hydroxy groups in SDS-LDH, which contribute to the satisfactory removal of F-53B by SDS-LDH. In addition, sodium dodecyl sulfate can offer extra active sites for F-53B via a weak hydrogen bond as C-F/Cl…H.
Emerging Contaminants Part II
Patricia Reyes
Emerging Contaminants and the MCL Development Process
Lisa Corey, Ph.D.
Under the Safe Drinking Water Act, US EPA evaluates chemical contaminants in drinking water for regulation. Based on the chemical’s hazard and potential for exposure, EPA may enact a non-enforceable Maximum Contaminant Level Goal (MCLG) followed by a Maximum Contaminant Level (MCL). Regulation of contaminants in drinking water often lags behind occurrence and detection in ground and surface waters. With an increased emphasis on using the best available scientific methods, the process of MCL development requires more time and specific expertise. This presentation will briefly review past methods of MCL development and compare these with current methods using two chemicals recently evaluated by US EPA in the MCLG process. The current methods of chemical evaluation will also frame the discussion on the emerging issue of perfluorinated compounds (PFAS). PFAS present a difficulty in that they are a large class of chemicals in which most of the chemicals have very little toxicological information available to form the basis of an MCLG; however, the information on several members of the class have spurred concern among communities, regulatory agencies, and other stakeholders.
Hidden Valley Lake Community Services District Pilots Innovative Cr(VI) Remediation System
Vladimir Dozortsev, Ph.D.
An innovative approach to generate a stannous ion reagent in-situ via an electrolytic process has been evaluated at the Hidden Valley Lake Community Services District (HVLCSD) during a pilot demonstration that studied the efficacy of the technology to continuously reduce Cr (VI) to below 10 ppb. The HVLCSDpilot site has a Cr (VI) level of 18-22 ppb with a well output of 1,100 gallons per minute (gpm).The piloted technology features an online Cr (VI) analyzer to control and monitor system performance (http://www.aquametrologysystems.com/learn-more-cr/), in real time, making the system an ideal solution for HVLCSD’s remote location since unattended operation is possible. Scale demonstrations often generate substantial waste streams of treated water that must be wasted; however this was not the case with HVLCSD. The pilot system was designed to minimize treated waste streams while demonstrating performance at scale, limiting the size and cost of the pilot unit, aiding the rapid deployment of the technology and minimizing disruption to the pilot site owing to its very small footprint. Results of this novel Cr (VI) remediation system pilot at HVLCSDwill be detailed.
PFAS Removal Using Super-fine Powdered Activated Cargon Couples with Ceramic Membrane Microfiltration
Terence Reid, PE
Emerging public concern for eliminating per- and polyfluoroalkyl substances (PFASs) is accelerating the advancement of new treatment approaches. Granular activated carbon (GAC) is an effective PFAS adsorbent, but primarily on the long-chained compounds. Limited capabilities removing short-chained PFAS and high disposal costs have driven the need for new, more effective solutions. Super-fine powdered activated carbon (SPAC) with a mean particle diameter < 1 µm has demonstrated specific PFAS adsorption rates of 480 times greater than the most effective GAC products. The high effective surface area and smaller diameter offers greater access to internal micro- and mesopores permitting high reductions in both long and short-chained PFAS compounds. A novel technology employs cross-flow ceramic membrane microfiltration (CMF) to generate a highly concentrated SPAC suspension and produce superior removals of broad-spectrum PFAS compounds from contaminated water. Direct comparison of the SPAC-CMF system performance with that of GAC has demonstrated exceptional removal efficiencies while demanding significantly less carbon. The SPAC-CMF system’s rapid adsorption kinetics and higher loading capacity prior to breakthrough offers an improved PFAS removal solution for both drinking water and site remediation applications. A 500 liter/day fully automated, mobile pilot system has been developed to demonstrate the SPAC-CMF technology.
PFAS: Smart Characterization for an Emerging Contaminant
Patrick Curry, PG
The benefits of flux-based conceptual models derived from high-resolution site characterization are well understood for chlorinated solvents (CVOCs) and hydrocarbons. However, most practitioners are not aware that the approach can be used for emerging contaminants like per- and polyfluoroalkyl substances (PFAS). The introduction of a mobile laboratory capable of producing reliable PFAS results in hours instead of weeks has enabled us to conduct real-time characterization at PFAS sites for the first time. When combined with high resolution injection logging methods like the Hydraulic Profiling Tool (HPT), PFAS impacts can be mapped using a mass flux framework to identify key transport pathways that help focus extraction-based remedies.
The mobile PFAS laboratory (Pace Analytical Services, Inc.) uses a solid phase extraction sample prep technique followed by LC/MS/MS analyses that are based on EPA Method 537 (modified). The mobile lab is able to process up to 20 groundwater samples per day, which is sufficient to guide multiple drilling rigs and eliminate wasted borings and samples. This approach allows stakeholders to quickly understand the distribution of PFAS, and evaluate focused, efficient remedies – particularly important given the challenges associated with PFAS remediation. These concepts are illustrated using several case studies.
Plenary Session
Wayne Praskins
Water Supply
Leslie Dumas, P.E., D.WRE
Developing a Programmatic Approach to Integrated Groundwater Resources Management
Leslie Dumas, P.E., D.WRE
California’s Sustainable Groundwater Management Act (or SGMA) establishes a new structure for the local management of groundwater to ensure long-term sustainability. SGMA requires preparation of Groundwater Sustainability Plans (or GSPs) by Groundwater Sustainability Agencies (or GSAS), which include a definition of basin sustainability and a plan to achieve the desired sustainability goals. GSPs are required to address six ‘undesirable results’ including the long-term stability of groundwater levels, protecting and improving groundwater quality, protecting groundwater-dependent ecosystems and minimizing inelastic land subsidence. Successful programs will require the integrated management of all types of water supplies in addition to a larger programmatic approach to ensuring that significant undesirable results do not occur while minimizing impacts to urban and agricultural land use. At the time this conference occurs, GSPs due in January of 2020 will have been drafted and those due in January of 2022 underway. This presentation will summarize the means and methods developed under SGMA for integrated groundwater basin management and will provide an assessment as to the Plans’ complexity and implementation that will be required to meet the State’s objective of long-term sustainable groundwater basins.
The Parchment Water Response - Coordinated Response to a Water Emergency
David Harn
On July 26, 2018, the MDEQ received results showing high levels of PFAS compounds in the City of Parchment’s municipal water supply. The water supply had been sampled on June 18 as part of a statewide sampling initiative for public water supplies and schools. Results of the sampling indicated a concentration of PFOS at 760 ppt and PFOA at 670 ppt. The total PFAS concentration identified in the system was 1,600 ppt. The water system served over 1,200 customers and 3,100 people in Parchment and adjoining Cooper Township. A “Do Not Drink” advisory was immediately issued, a state of emergency declared, and arrangements were made to provide alternate water to the affected residents. Over the course of the next 30 days, the City of Kalamazoo was able to connect its water system to Parchment’s, and on August 27, 2018, the advisory for the municipal system was lifted.
A residential well sampling program also was undertaken in the area as many residents in Cooper Township are served by private water wells. Sampling of these wells identified PFAS impacts, necessitating additional response actions. While the initial crisis impacting the municipal system has been addressed, work continues to protect residents in Cooper Township.
Time for a Groundwater Revolution: Security and Water Supply in Sub-Saharan Africa
Jude Cobbing, Ph.D.
Groundwater is the main source of domestic water for most Africans, and it supports widespread small-scale irrigation. Groundwater is especially vital in the drought-prone African drylands. Yet, in contrast to India, China, California and other regions, Africa has had no large-scale groundwater-led “green revolution”, and few associated economic benefits. This is despite major groundwater potential – most African countries use less than 10% of their sustainable, renewable groundwater resource. Sub-Saharan Africa’s population will double by 2050, and urban populations will triple. Africa needs a step-change in groundwater use – a groundwater revolution. This will improve food security, urban living conditions, and climate resilience, and boost economic growth. A mix of political-economy factors is likely responsible for the current low levels of groundwater use in Sub-Saharan Africa, together with an ascendant international groundwater discourse of crisis, caution and scarcity that is more relevant to heavily exploited regions. Since water supply is closely coupled with security and stability in Africa, and African stability greatly influences global security, now is the time for groundwater thought leaders and influential groundwater organizations to support a groundwater-led green revolution in Africa.