Engineering Papers⌕ Search

Engineering topics

Freshley, Mark

Publications and source records attributed to Freshley, Mark.

7 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

Coupling Big Data Analytics and Reactive Transport Modeling for Cost-effective Groundwater Monitoring - 17163

This study presents an innovative approach for sustainable and cost-effective groundwater monitoring. This approach takes advantage of recent advances in various technologies: (1) in situ autonomous sensors, (2) big data analytics, and (3) parallel high-performance computing for flow and reactive transport modeling. In situ sensors are used to periodically measure the key variables (such as pH, redox potential, electrical conductivity, and groundwater level), which control contaminant mobility and the plume spatial and temporal distribution. Based on a limited number of groundwater sampling, the data analytics methods-data mining and machine learning-allow us to identify and quantify the correlations between the in situ-measured variables and contaminant concentrations, and also to detect significant changes associated with the plume mobility. In addition, a state-of-the-art parallel numerical flow and reactive transport simulator Amanzi, and uncertainty quantification software Agni are used to provide an improved physical and mechanistic understanding of the contaminated groundwater system behavior, and to predict the long-term plume distribution for optimizing and adapting the monitoring strategy. Amanzi and Agni were developed as part of the Advanced Simulation Capability for Environmental Management (ASCEM) program of the DOE Office of Environmental Management. Such modeling is critical, particularly, for assessing the impact of climate change and associated hydrological shifts. The developed approach is expected to significantly reduce the groundwater sampling frequency and associated cost. In addition, the real-time information on plume mobility serves as an early warning system, improving the resiliency of contaminated or potentially contaminated sites. We demonstrate this approach using as an example the Savannah River Site (SRS) F-Area, where groundwater is contaminated by various radionuclides, including uranium, tritium and technetium. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2017

Applications Of The Advanced Simulation Capability For Environmental Management (ASCEM) - 17253

Three applications were completed using the Advanced Simulation Capability for Environmental Management (ASCEM), supported by the U.S. Department of Energy's Office of Environmental Management. These analyses were performed for the Savannah River Site (SRS) F-Area, the Los Alamos National Laboratory (LANL) Site, and the Nevada National Security Site (NNSS). At the SRS F-Area, ASCEM simulations were used to help develop cost-effective, long-term monitoring approaches for science-based site closure and management. The simulation results were used to develop a mechanistic understanding of correlations between contaminant concentrations and master variables that can be used for monitoring. At LANL, the ASCEM simulator Amanzi was integrated with a LANL-based decision support tool for the LANL onsite program. A saturated-zone site model focused on a key area of interest was developed and calibrated to measured data. This model was applied to quantify uncertainty and provide decision support to inform chromium remediation efforts. To support assessment of groundwater contamination at NNSS, ASCEM was used to calibrate hydrologic properties and flow directions using water levels observed under steady-state conditions and during four different pump tests on Pahute Mesa. The flow fields generated from these pump tests will be used to simulate transport pathways from underground nuclear tests to compare with field observations and to test alternative conceptual models of transport, which will ultimately facilitate better placement of monitoring wells. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2017

Technetium Management Program Plan - 17376

Technetium management is a high-priority activity for the U.S. Department of Energy (DOE) Office of Environmental Management (EM) complex. Waste management and remediation issues involving technetium represent environmental risks and challenges that are unique to DOE. This plan lays out the technology development activities that are underway as well as future technology needs to address technetium issues across DOE EM sites and across programmatic areas of tank waste, groundwater and soils, and facility decommissioning and deactivation in order to be comprehensive and to allow integration of similar activities. The program was developed in close coordination with site representatives and program offices. Activities and needs that were identified share common themes and were grouped into areas of characterization, treatment, and disposition. Characterization includes understanding the inventory at particular locations, the chemical species, and chemical and physical behavior, whether in a treatment process flowsheet or a geological setting that displays periodic contaminant releases. The tools for characterization in these different environments might use the same sensors or protocols. Treatment options include methods to capture technetium such as ion-exchange or manipulation of oxidation states, which also may be applied across program areas. Disposition includes end-points of the processes and environmental risk, including waste form behavior, mobility of technetium once it is treated or remediated, and long-term monitoring. Disposition represents integration of all cleanup actions at a site. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2016

Effective Long-term Monitoring Strategies by Integrating Reactive Transport Models with In situ Geochemical Measurements - 16212

Long-term monitoring of contaminant transport in groundwater is expected to account for a large fraction of future life-cycle cleanup costs at the DOE sites. The Attenuation-Based Remedies in the Subsurface Applied Field Research Initiative (ABRS AFRI) is developing an innovative approach for cost-effective in situ long-term monitoring. The approach is based on strategically adding the measurements of controlling variables (such as pH, redox potential, electrical conductivity, and groundwater level), which control the plume mobility and its spatial and temporal distribution. In situ measurements of these variables - supplemented with a reduced number of standard periodic groundwater samples - are expected to lead to more cost-effective monitoring, and can also serve as an early warning system for detecting unexpected plume migration. The objective of this study is to support the development of such a long-term monitoring approach through the application of advanced computational methods, including (1) statistical data mining and analysis, and (2) three-dimensional flow and reactive chemical transport modeling. We have performed the statistical data analysis of historical and current monitoring data at the Savannah River Site (SRS) F-Area to quantify the correlations between the controlling variables and radioactive contaminant concentrations. In parallel, we have used 3D modeling of flow and contaminant transport to provide the prediction of the contaminant plume evolution. The results of both data analysis and modeling confirmed that the correlations between controlling variables and contaminant concentrations are significant. Modeling results also suggest that the correlation parameters will change in the future, which is important to assess the long-term efficacy of the proposed monitoring approach. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2016

Applications Using the Advanced Simulation Capability for Environmental Management Tool-set - 16335

The Office of Soil and Groundwater of the U.S. Department of Energy (DOE) Office of Environmental Management (EM) developed the Advanced Simulation Capability for Environmental Management (ASCEM). The ASCEM tool-sets can be used for making informed choices in uncertain and complex environments, where cost-benefits of environmental impacts and human health need to be considered. The deployments and demonstrations show how ASCEM provides a unified framework that facilitates efficient modeling and analyses to address costs and benefits of engineering and remediation decisions: - Evaluation of engineered remediation and monitoring strategies at the Savannah River Site (SRS) F-Area in collaboration with the Office of Soil and Groundwater Remediation, Attenuation-Based Remedies in the Subsurface Applied Field Research Initiative; - Assessment of performance assessment issues and waste tank closure at SRS; - Evaluation of alternative conceptual models for the deep vadose zone at the Hanford Site, supporting waste tank closure. The ASCEM tool-sets enable computationally efficient representations of the complex subsurface systems, including fractured and faulted volcanic and carbonate aquifers, a very deep water table, and multiple contaminant sources. The applications demonstrate that deployment of the ASCEM tool-sets provides an opportunity to reduce conservatisms in modeling assessments and allows detailed investigation of alternative conceptual models. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2016

Technical Evaluation of Iodine Remediation for 200-UP-1 - 16379

From the 1940's through the 1990's, liquid wastes from materials used and produced at the Hanford Site were disposed to the ground through cribs, ditches, ponds, and trenches. The major sources that contributed to groundwater contamination within the 200-UP-1 Operable Unit (OU) were associated with plutonium-separation and uranium recovery operations at the S Plant and U Plant facilities, as well groundwater migration from 200-ZP-1 OU. Iodine-129 is present in the groundwater and vadose zone beneath the 200-UP-1 OU, and is one of the primary risk drivers for the site. Hydraulic containment is the currently selected remedy for I-129 in the groundwater. There is currently no remedy selected for controlling migration of I-129 from the vadose zone to the groundwater. A UP-1 Evaluation Plan for I-129 was developed to provide the scientific and technical understanding necessary for developing remediation approaches for I-contaminated groundwater as well as risk-based approaches for managing I-129 present in the vadose zone. A site conceptual model for understanding the biogeochemical drivers for iodine speciation and determine the processes that drive the fate and transport of I-129 through the vadose zone and into groundwater was included. These data will provide the information to decrease the uncertainty related to the inventory, distribution, and transport properties which will lead to appropriate treatment strategies for the I-129 plume(s). A wide range of technologies and approaches are being evaluated including consideration of removal, cost, and long-term impacts to the site. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗