NERT is conducting a number of treatability and pilot studies aimed at identifying effective remediation approaches for the contaminants present beneath the NERT Site or migrating from the NERT Site. The goal of each study is to evaluate a given method’s effectiveness at destroying or removing one or more of the identified contaminants. NERT’s treatability studies have included both laboratory testing and field testing of treatment technologies within the NERT RI Study Area. Field testing assesses the effectiveness of the treatment technology in conditions unique to the NERT RI Study Area. Pilot studies are larger-scale tests performed in the field to provide quantitative performance, cost, and design information for the remedial technology being tested. The technologies being tested may eventually be used to supplement or replace the Site’s existing groundwater extraction and treatment system (GWETS) if the new methods are more effective, have greater longevity, and/or are more efficient.
The figure above shows the locations of the various treatability and pilot studies that have been implemented within the NERT RI Study Area.
OU-1 Treatability Studies:
Soil Flushing Treatability Study
Status: Complete
Summary: This study was designed to evaluate the feasibility of infiltrating additional water into the subsurface to mobilize soluble contaminants, primarily perchlorate, in soils. The mobilized contaminants could then be captured and treated by the Site’s existing groundwater extraction and treatment system. Additives could also be introduced into the infiltrating water to enhance biologic degradation of the some of the contaminants. Prior to field implementation, laboratory tests were performed at the University of Nevada – Las Vegas (UNLV) to better understand physical and chemical conditions that may alter the effectiveness of the approach. Microcosm studies were performed to support biodegradation of perchlorate in vadose zone soils focused on the effectiveness of several carbon substrates and the need for macronutrient addition. The field study found reductions of perchlorate mass between 5% and 98% following soil flushing, depending on the rate of water application and use of a carbon substrate.
Work Plan: Treatability Study Work Plan Soil Flushing Pilot Test dated November 26, 2014 (NDEP approved on January 7, 2015)
Final Report: Soil Flushing Treatability Study Report dated July 3, 2017 (NDEP approved on August 22, 2017)
In-Situ Chromium Treatability Study
Status: Complete
Summary: This study was designed to evaluate the feasibility of, and the optimal approach for, achieving in-situ reduction of hexavalent chromium in groundwater at the NERT Site using both chemical and biological technologies. Microcosm and column studies were performed at UNLV prior to performing the field study to evaluate the effectiveness of the proposed chemical amendments and carbon substrates in promoting hexavalent chromium reduction under site-specific conditions. Both field-scale reduction studies demonstrated effective and rapid reduction of hexavalent chromium in groundwater. The field-scale contaminant reduction study, which used calcium polysulfide as a reducing agent, reduced hexavalent chromium within less permeable units, but appeared less effective in more permeable units. The biological reduction study demonstrated effective and rapid reduction of hexavalent chromium and other contaminants in groundwater within more permeable areas, while biological reduction was slower and less extensive for groundwater in less permeable units.
Work Plan: In-Situ Chromium Treatability Study Work Plan dated May 31, 2016 (NDEP approved on August 19, 2016)
Final Reports: In-Situ Chromium Treatability Study Results Report dated June 22, 2018 (NDEP approved on August 3, 2018); Addendum to the In-Situ Chromium Treatability Study Results Report dated January 25, 2019 (NDEP approved on April 11, 2019)
Vacuum Enhanced Recovery (VER) Treatability Study
Status: Complete
Summary: This study was designed to evaluate the extent to which applying a vacuum on groundwater extraction wells screened within lower permeability soils would improve groundwater recovery of the well compared to conventional pumping. This technology could be utilized to improve groundwater recovery in existing groundwater extraction wells, as well as reduce the number and depth of groundwater extraction wells to be installed within lower permeability soils. Based on the results of the study, depending on the conditions and depth of the extraction well, VER increased groundwater extraction rates by 21%-30% and the simulated radius of influence by 8%-26%.
Work Plan: Vacuum Enhanced Recovery Treatability Study Work Plan dated August 23, 2017 (NDEP approved on September 18, 2017)
Final Report: Vacuum Enhanced Recovery Treatability Study Results Report dated July 12, 2018 (NDEP approved on September 6, 2018)
Ammonium Perchlorate (AP) Area Down and Up Flushing Treatability Study
Status: Complete
Summary: This study was designed to build on the Soil Flushing Treatability Study (described above). This study tested a new, larger scale, water delivery system (drip irrigation) designed to flush perchlorate from the vadose zone soils, as well as the viability of removing perchlorate from saturated soils within the Upper Muddy Creek formation (UMCf), which has lower permeability. Perchlorate mass reductions of 97% and 99% were achieved in the vadose zone via soil flushing. Perchlorate mass reductions of 44% and 51% were observed in the lower permeability saturated soils.
Work Plan: AP Area Down and Up Flushing Treatability Study Work Plan dated February 15, 2018 (NDEP approved on March 5, 2018)
Final Report: AP Area Down and Up Flushing Treatability Study Results Report dated December 21, 2018 (NDEP approved on January 18, 2019)
Hydrogen Gas Permeable Membrane Treatability Study
Status: Complete
Summary: The goal of this study was to determine if hydrogen-based gas permeable membrane technology can consistently reduce perchlorate at high concentrations in groundwater to below 18 µg/L, the current perchlorate discharge limit for the fluidized bed reactor (FBR) system and produce less waste than the current FBRs. In the propriety hollow-fiber membrane biofilm reactor, autotrophic micro-organisms use hydrogen gas as an electron donor to reduce perchlorate, as well as other oxidizing contaminants such as chlorate or hexavalent chromium. Testing indicated that this technology was successful in reducing the concentrations of perchlorate and hexavalent chromium below the target levels established in the work plan.
Work Plan: Hydrogen-Based Gas Permeable Membrane Technology Pilot Test Work Plan dated February 15, 2019 (NDEP approved on March 27, 2019)
Final Report: Hydrogen-Based Gas Permeable Membrane Pilot Test Results Report, Revision 2 dated May 31, 2023 (NDEP approved on June 8, 2023)
Unit 4 Source Area In-Situ Bioremediation Treatability Study
Status: In Progress
Summary: This treatability study is evaluating source area groundwater treatment using a combination of in-situ bioremediation and groundwater extraction to treat groundwater impacted with very high concentrations of perchlorate and other contaminants within the former Unit Building 4 area. Generally, perchlorate-reducing microorganisms are ubiquitous in the subsurface, but need to be stimulated with a food and energy source. As a result, successful in-situ groundwater treatment using bioremediation requires understanding the chemical, geochemical, physical, geological, and hydrogeological conditions, followed by developing a scientifically-based engineered approach to achieve the required conditions for native microorganisms to thrive and biodegrade perchlorate in this area of very high contaminant concentrations. A series of bench-scale studies were performed at UNLV prior to field implementation within the Unit 4 source area to evaluate the effectiveness of proposed carbon substrates and amendments under site-specific conditions. Results of the bench-scale study and the plan for a field-scale study are presented in the Unit 4 Source Area In-Situ Bioremediation Treatability Study Work Plan Addendum dated July 22, 2021. The field component of the study began in late 2021 and is anticipated to continue through late 2024.
Work Plans: Unit 4 Source Area In-Situ Bioremediation Treatability Study Work Plan dated February 5, 2018 (NDEP approved on February 21, 2018). The Unit 4 Source Area In-Situ Bioremediation Treatability Study Work Plan Addendum dated July 22, 2021 (NDEP approved on September 1, 2021).
Final Report: To be issued in Q2 2025
OU-2 Treatability Studies:
Galleria Drive Bioremediation Treatability Study
Status: Complete
Summary: The objective of this in-situ bioremediation treatability study was to demonstrate and evaluate the effectiveness of implementing in-situ bioremediation to reduce the contaminants present in the shallow UMCf that are migrating through the vicinity of Galleria Drive in the Eastside Study Area. A bench-scale study, which is described in the Galleria Drive Bioremediation Treatability Study Work Plan Addendum, was performed at UNLV to evaluate the effectiveness of bioremediation on site-specific soil and groundwater that contains elevated sulfate and total dissolved solids concentrations. The Galleria Drive Bioremediation Treatability Study was terminated prior to field implementation due to a potential land sale within the originally proposed study area and unfavorable subsurface conditions (i.e., extremely low hydraulic conductivity zones making injections into the subsurface impractical) in subsequently identified areas.
Work Plans: Galleria Drive Bioremediation Treatability Study Work Plan dated October 6, 2017 (NDEP approved on October 31, 2017), Galleria Drive Bioremediation Treatability Study Work Plan Addendum dated March 29, 2019 (NDEP approved on May 1, 2019), and Treatability/Pilot Study Modification No. 8 – Galleria Drive Bioremediation Treatability Study dated July 30, 2019 (NDEP approved on August 2, 2019).
Final Report: Phase 2a Results and Final Closeout – Galleria Drive Bioremediation Treatability Study issued on March 27, 2020 (NDEP approved on May 11, 2020).
OU-3 Treatability Studies:
Groundwater Bioremediation Treatability Study
Status: Complete
Summary: A bioremediation treatability study was conducted near the City of Henderson’s Bird Viewing Ponds (Birding Ponds) to evaluate the feasibility of the in-situ bioremediation of perchlorate in the groundwater present within the alluvium. Both microcosm and column studies were performed at UNLV prior to performing the field study to evaluate the effectiveness of the proposed carbon substrates in promoting perchlorate reduction in groundwater under site-specific conditions. During the initial bioremediation evaluation near the Birding Ponds, groundwater was found to be amenable to perchlorate biodegradation and the addition of a carbon substrate provided a sustained reducing environment in the subsurface for significant perchlorate biodegradation.
Work Plan: Groundwater Bioremediation Treatability Study Work Plan dated January 6, 2015 (NDEP approved on January 21, 2015).
Final Report: Groundwater Bioremediation Treatability Study Results Report dated November 25, 2016 (NDEP approved on June 26, 2017).
SWF Area Bioremediation Treatability Study
Status: In Progress
Summary: The objective of this treatability study was to demonstrate the effectiveness of using in-situ bioremediation to reduce the flux of perchlorate mass that is not currently being captured by the existing extraction well network. Prior to field testing, both microcosm and adsorption/desorption tests were performed at UNLV to evaluate the effectiveness of the proposed carbon substrates in promoting perchlorate reduction under site-specific conditions and to evaluate the potential longevity of the proposed injectates. The treatability study successfully demonstrated that in-situ bioremediation is effective at substantially reducing perchlorate and chlorate concentrations in groundwater. Based on these results, this treatability study was extended to develop a more thorough understanding of the key design considerations and operation and maintenance components as they relate to long-term applications of in-situ bioremediation (such as long-term injection frequencies and quantities, injection well maintenance requirements, and potential biomass buildup in the subsurface). The field component of the treatability study was completed in March 2023, with a comprehensive results report anticipated to be submitted in October 2024.
Work Plans: Seep Well Field Area Bioremediation Treatability Study Work Plan dated September 6, 2016 (NDEP approved on September 22, 2016); Treatability/Pilot Study Modification No. 6 – Seep Well Field Area Bioremediation Treatability Study dated December 11, 2018 (NDEP approved on December 14, 2018)
Interim Final Report: Seep Well Field Area Bioremediation Treatability Study Results Report dated August 13, 2019 (NDEP approved on September 30, 2019)
Annual Reports: Annual Progress Reports are submitted for the study extension. The NDEP-approved annual progress reports include: the Seep Well Field Area Bioremediation Treatability Study - 2021 Annual Progress Report dated August 17, 2022 (NDEP approved on September 30, 2022); the Seep Well Field Area Bioremediation Treatability Study - 2020 Annual Progress Report dated September 29, 2021 (NDEP approved on November 17, 2021); and the Seep Well Field Area Bioremediation Treatability Study 2019 Annual Progress Report dated September 4, 2020 (NDEP approved on October 8, 2020).
Las Vegas Wash In-Situ Bioremediation Pilot Study
Status: In Progress
Summary: The goal of this study was to evaluate the effectiveness and implementability of in-situ bioremediation in a geologically complex portion of the NERT RI Study Area where perchlorate-contaminated groundwater is migrating into the Las Vegas Wash. This study builds on previous bioremediation work conducted as part of the Groundwater Bioremediation Treatability Study (see description above) and SWF Area Bioremediation Treatability Study (see description above). Prior to beginning the field study, adsorption/desorption tests and column diffusion studies were performed to better understand the interaction of the Upper Muddy Creek Formation (UMCf) soil with the proposed carbon substrates, as well as evaluation of the potential for upward migration of perchlorate from the UMCf into the alluvium. Other studies focused on the alluvium and more transmissive deposits, so this study has been implemented to evaluate the effectiveness and implementability of in-situ bioremediation in the low permeability UMCf. Separate studies for the UMCf are necessary to examine in-situ bioremediation in varying lithological characteristics, saturated thicknesses, and chemical/geochemical compositions of the groundwater that will likely be encountered during full-scale remediation. The pilot study is being executed on a larger scale than previous bioremediation treatability studies conducted for NERT and is providing key information needed to evaluate design, optimization/scale-up, and efficiency of this technology and its effectiveness on the RAO of mitigation of the perchlorate mass flux discharge to the Las Vegas Wash. The field component of the study began in late 2020 and was completed in December 2022, with the final results report planned to be submitted in the first quarter of 2024.
Work Plans: Pre-field and laboratory activities were described in the Las Vegas Wash Bioremediation Pilot Study Work Plan dated September 22, 2017 (NDEP approved on October 16, 2017). Results of the bench-scale studies and implementation of the pilot study are described within the Las Vegas Wash Bioremediation Pilot Study Work Plan Addendum dated November 11, 2019 (NDEP approved on December 11, 2019).
Final Report: To be issued in Q1 2024
Las Vegas Wash Zero-Valent Iron (ZVI) Enhanced Bioremediation Treatability Study
Status: In Progress
Summary: The goal of this treatability study is to test the performance of coarse-grained zero valent iron (ZVI) in treating perchlorate in groundwater when operated as a passive flow-through groundwater treatment system. In groundwater, ZVI corrodes (i.e., rusts) producing dissolved hydrogen, which is used by naturally-occurring bacteria to reduce perchlorate. ZVI-enhanced bioremediation is a unique application with several key positive attributes that may result in this being a more efficient and effective technology. Bench-scale testing conducted using soil and groundwater from two test areas indicates that coarse-grain ZVI can enhance biological reduction of perchlorate in groundwater given appropriate stimulation of the microbial environment. Batch microcosm and column tests were performed at UNLV using soil and groundwater from one test area near Galleria Drive and additional batch microcosm tests to evaluate coarse-grain ZVI treatment of nitrate, chlorate, and perchlorate at a test area near the Las Vegas Wash. A necessary next step is to test coarse-grain ZVI in the field under site-specific subsurface conditions to provide important information for design, monitoring, and construction of a potential full-scale application of this technology. The field component of the study began in August 2022 and is anticipated to continue through 2024.
Work Plans: Phase 1 of this treatability study, described in the Galleria Road ZVI-Enhanced Bioremediation Treatability Study Work Plan dated September 29, 2017 (NDEP approved October 26, 2017), was completed in June 2019. This treatability study was moved from the Galleria Drive area to the Las Vegas Wash area and supplemental field investigation and bench-scale testing is described within Treatability/Pilot Study Modification No. 9 dated October 8, 2019 (NDEP approved on October 14, 2019). Results of the bench-scale studies and a description of the Phase 2 implementation of the treatability study are described in the Las Vegas Wash ZVI-Enhanced Bioremediation Treatability Study Work Plan Addendum dated September 29, 2021 (NDEP approved on November 10, 2021).
Final Report: To be issued in Q1 2025
Last updated: February 2024
