General Separations Area (GSA) Groundwater Flow Model Update: Hydrostratigraphic Data

Bagwell, L.; Bennett, Patti; Flach, G. P.

doi:10.2172/1345797

Cited by 3 publications

(5 citation statements)

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“…The groundwater flow model supporting Performance Assessments (PAs) and Composite Analyses (CAs) at the Savannah River Site was significantly revised in 2016 and 2017 (Flach et al 2017a, b) using new hydrostratigraphic surfaces (Bagwell et al 2017), updated well water level calibration targets (Hiergesell et al 2015), and semi-automated model calibration with the PEST optimization code (Flach 2015). This model is referred to as "GSA_2016".…”

Section: Introductionmentioning

confidence: 99%

Updated Groundwater Flow Simulations of the Savannah River Site General Separations Area

Flach

2019

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The groundwater flow model supporting Performance Assessments (PAs) and Composite Analyses (CAs) at the Savannah River Site was significantly revised in 2016 and 2017 using new hydrostratigraphic surfaces, updated well water level calibration targets, and semi-automated model calibration with the PEST optimization code. This model is referred to as "GSA_2016". This report documents further refinement of the GSA_2016 model in 2018 to incorporate updates to model calibration targets, closure of the H-Area Ash Basin, construction of E-Area Slit Trench operational covers, and plume information from the Mixed Waste Management Facility and Low-Level Radioactive Waste Disposal Facility. Another objective was to lower hydraulic head residuals by adding another calibration zone. The resulting model is referred to as "GSA_2018".

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Section: Introductionmentioning

confidence: 99%

Updated Groundwater Flow Simulations of the Savannah River Site General Separations Area

Flach

2019

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“…The 2004 GSA/PORFLOW model supported PA2008 (WSRC, 2008) and related SAs and was reviewed by the DOE LFRG in 2008. Considering the significant amount of field data acquired since the mid-1990s and maturation of optimization software available for model calibration, the LFRG "recommended that the model be reevaluated with more current data and recalibrated using automated inverse procedures" (Bagwell and Flach, 2016;DOE LFRG, 2008). In response to these reviews and in preparation for the current ELLWF PA revision, Bagwell and Flach (2016) developed a program and execution plan for GSA GW flow modeling with the following objectives:…”

Section: Gsa/porflow Flow Modelmentioning

confidence: 99%

“…During 2016 and 2017, the 2004 GSA/PORFLOW model was substantially revised to incorporate new hydrostratigraphic surfaces and updated well-water level calibration targets current through late 2014 Bagwell and Flach, 2016). The revised model, referred to as GSA_2016, is documented in detail by Flach et al (2017).…”

Section: Gsa_2016 Flow Modelmentioning

confidence: 99%

“…CPT over the past two decades has enabled delineation of hydrostratigraphic elevations at many more locations than available through the mid-1990s. As noted for the GSA_2016 flow model, revised hydrostratigraphic "picks" and generated detailed hydrostratigraphic surfaces for the GSA per the General Separations Area (GSA) Groundwater Flow Model Update: Program and Execution Plan (Bagwell and Flach, 2016). The new hydrostratigraphic surfaces were adopted as-is for grid generation in the GSA_2018 flow model update.…”

Section: Gsa_2018 Groundwater Flow Model Recalibration Approachmentioning

confidence: 99%

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Performance Assessment for the E-Area Low-Level Radioactive Waste Disposal Facility at the Savannah River Site: Chapter 3

MAYER

HAMM

ALEMAN

et al. 2023

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are the PA for the INTEC calcined solids storage facility at the Idaho National Laboratory site (DOE-ID, 2019) and the PA for Waste Management Area C at the Hanford site (Mehta et al., 2016). The PA evaluates the potential impacts of changes in performance of different features of the system and demonstrates that the safety functions represent multiple and redundant barriers. Barrier analyses, assuming a safety function is not present, also test the robustness of the system in the event of the loss of one or more safety functions. Such evaluations also support a qualitative illustration of the concept of defense-in-depth.The safety concept for closure of the ELLWF encompasses a variety of different features (i.e., administrative controls, natural site features, and engineered barriers) that reduce the potential impacts on human health and the environment from the residual waste that will remain after closure. These features can be represented as a collection of safety functions acting independently and as a system to provide for overall safety. In some applications, attempts are made to assign numerical expectations to specific safety functions, but that is not the intent in this case. The concept of safety functions is used more qualitatively in two ways for this PA: 1. To illustrate the robustness of the ELLWF design, operational practices, and closure approach by documenting features that are and are not credited in different modeling cases.

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“…The GSA2016 model reflects updated characterization and monitoring data, and use of the PEST optimization code to perform model calibration. The DOE LFRG recommended automated calibration in a 2008 review of the ELLWF PA (Bagwell and Flach, 2016). The final calibration phase produced four variants termed "GSA2016.LU," "GSA2016.LW," "GSA2016.HU," and "GSA2016.HW," where…”

Section: Porflow Reference Simulationsmentioning

confidence: 99%

GoldSim® Aquifer Model Calibration and Plume Interaction

Wohlwend

Flach

2018

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The E-Area Low-Level Waste Facility (ELLWF) Probabilistic Aquifer Model (PAM) utilizes GoldSim ® Monte Carlo simulation software (GTG, 2017) to evaluate the transport of a tracer species as it travels from the water table below the disposal unit footprint, through the aquifer, to the Point of Assessment (POA) at the 100-meter boundary. This report documents the development and calibration of PAM as well as the implementation of plume interaction. PAM is a key component of the effort to include uncertainty quantification and sensitivity analysis (UQSA) in the next revision of the E-Area Performance Assessment (PA), considering recommendations from the 2015 PA strategic planning team outlined by Butcher and Phifer (2016). The Aquifer Model and associated optimized geometric parameters will be implemented in the future GoldSim ® (GS) system model that will simulate subsurface flow and radionuclide transport from the ground surface to the 100-meter POA.Simulations were performed to develop a methodology for calibrating PAM to PORFLOW (PF) tracer simulation results for both steady-state and pulse source terms. The East Aquifer Model had more disposal units (DUs) with errors over 5% and required additional calibration to better match PF results compared to the West and Center Aquifer Models. This is likely due to the plume traveling partially in the high-velocity transmissive zone (TZ) and the low-velocity tan clay confining zone (TCCZ) and lower aquifer zone (LAZ), as well as the streamtraces not being oriented perpendicular to the DU's cross-section. Overall percent errors, shown in Figure 0-1, between the calibrated Aquifer Model and the PF tracer simulations average 4% for the 32.8-foot and 10-foot dispersivity cases and 12% for the 100-foot dispersivity cases. Compared to the West and Center Aquifer Models, the East Aquifer Model has consistently larger Plume Overlap Factors with 22 factors exceeding 0.50 for the 32.8-foot dispersivity, steady-state simulations. As expected, the factors are larger where the streamtraces for neighboring DUs are nearby. Key findings and recommendations include:• Use of a single GS aquifer element for each DU adequately reproduces 3D PORFLOW tracer simulation results.• Implementation of plume overlap will not utilize the built-in GS plume function because this correction factor requires calibration to the ratio between the PF-calculated plume contribution and the GS concentration. Instead, the ratio itself will be directly used as the Plume Overlap Factor (POF) as a simpler means of accounting for co-mingling of plumes.

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General Separations Area (GSA) Groundwater Flow Model Update: Hydrostratigraphic Data

Cited by 3 publications

References 0 publications

Updated Groundwater Flow Simulations of the Savannah River Site General Separations Area

Updated Groundwater Flow Simulations of the Savannah River Site General Separations Area

Performance Assessment for the E-Area Low-Level Radioactive Waste Disposal Facility at the Savannah River Site: Chapter 3

GoldSim® Aquifer Model Calibration and Plume Interaction

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