Potential Groundwater Recharge from the Infiltration of Surface Runoff in Cold and Dry Creeks, Phase 2

Runoff from Cold and Dry Creeks may provide an important source of groundwater recharge on the Hanford Site. This report presents estimates of total volume and distribution of such recharge from extreme precipitation events. Estimates were derived using a simple approach that combined the Soil Conservation Service curve number runoff method and an exponential-decay channel infiltration model. Fifteen-minute streamflow data from four gaging stations, and hourly precipitation data from one climate station, were used to compute curve numbers and calibrate the infiltration model. All data were from several storms occurring during January 1995. Design storm precipitation depths ranging from 1.6 to 2.7 inches were applied with computed curve numbers to produce total runoff/recharge of 7,700 to 15,900 ac-ft, or approximately 10 times the average annual rate from this recharge source as determined in a previous study. Approximately two-thirds of the simulated recharge occurred in the lower stream reaches contained in the broad alluvial valley that parallels State Highway 240 near the Hanford 200 Area

2005 Closure Assessments for WMA-C Tank Farms: Numerical Simulations

In support of CH2M HILL Hanford Group, Inc.'s (CHG) closure of the Hanford Site Single-Shell Tank (SST) Waste Management Area (WMA) tank farms, numerical simulations of flow and solute transport were executed to investigate different potential contaminant source scenarios that may pose long-term risks to groundwater from the closure of the C Tank Farm. These simulations were based on the initial assessment effort (Zhang et al., 2003), but implemented a revised approach that examined a range of key parameters and multiple base cases. Four different potential source types were identified to represent the four base cases, and included past leaks, diffusion releases from residual wastes, leaks during retrieval, and ancillary equipment sources. Using a two-dimensional cross section through the C Tank Farm (Tanks C-103–C-112) and a unit release from Tank C-112, two solutes (uranium-238 (U-238) and technetium-99 (Tc 99)) were transported through the problem domain. To evaluate the effect of sorption on contaminant transport, seven different sorption coefficients were simulated for U 238. Apart from differences in source releases, all four base cases utilized the same median parameter values to describe flow and contaminant transport at the WMA C. Forty-six additional cases were also run that examined individual transport responses to the upper and lower limits of the median parameter values implemented in the base case systems. For the conservative solute, Tc-99, results amongst the base cases showed that the simulations investigating past leaks demonstrated the highest peak concentrations and the earliest arrival times (48 years) due to the proximity of the plume to the water table and the high recharge rate before surface barriers were installed. Simulations investigating leaks during retrieval predicted peak concentrations ~60 times smaller than the past leak cases, and corresponding arrival times that occurred ~70 years later. The diffusion release base case predicted the lowest peak concentrations and arrival times for all solutes. Even after 10,000 years of simulation, only 11.2% of the Tc-99 mass migrated past the fence line compliance point in the groundwater. Although ancillary equipment cases released the contaminant at a similar depth as the diffusion cases, nearly all of the Tc-99 (99.0%) exited the groundwater domain by the end of the simulation due to differences in release rates. These differences were also reflected in the peak arrival times, which were ~8,500 years for the diffusion base case, and ~3,700 years for the base ancillary equipment release. In the diffusion cases, peak concentration predictions were sensitive to the rate of diffusion, but had no impact on the peak concentration arrival times. The average peak concentration was ~3.2 times higher than the base case value for the upper estimate of diffusion, and 3.2 10-3 lower for the lower bounding estimate. The past leak, ancillary equipment and retrieval leak cases were sensitive to the estimate of the pre-barrier installment recharge rate. For example, on average for the past leaks, relative concentrations increased by ~2.2 times for the upper recharge estimate, and decreased by ~0.14 times for the lower bound. Faster arrival times were associated with the upper recharge estimate, and slower arrival times with the lower estimate. Similar trends in both predicted peaks and arrival times occurred for the ancillary equipment and retrieval leaks scenarios that investigated the uncertainty in the pre-barrier installment recharge rate. Uncertainty in the plume depth also impacted predicted peak concentrations and arrival times for the past leak scenario. Trends similar to the pre-barrier installment recharge rate resulted, with higher concentrations and earlier breakthroughs associated with a lower plume depth, and lower concentrations and later breakthroughs with a higher plume depth

Analysis of Flood Hazards for the Materials and Fuels Complex at the Idaho National Laboratory Site

Researchers at Pacific Northwest National Laboratory conducted a flood hazard analysis for the Materials and Fuels Complex (MFC) site located at the Idaho National Laboratory (INL) site in southeastern Idaho. The general approach for the analysis was to determine the maximum water elevation levels associated with the design-basis flood (DBFL) and compare them to the floor elevations at critical building locations. Two DBFLs for the MFC site were developed using different precipitation inputs: probable maximum precipitation (PMP) and 10,000 year recurrence interval precipitation. Both precipitation inputs were used to drive a watershed runoff model for the surrounding upland basins and the MFC site. Outflows modeled with the Hydrologic Engineering Centers Hydrologic Modeling System were input to the Hydrologic Engineering Centers River Analysis System hydrodynamic flood routing model

Environmental application of stable xenon and radioxenonmonitoring

Characterization of transuranic waste is needed to makedecisions about waste site remediation. Soil-gas sampling for xenonisotopes can be used to define the locations of spent fuel andtransuranic wastes. Radioxenon in the subsurface is characteristic oftransuranic waste and can be measured with extreme sensitivity usinglarge-volume soilgas samples. Measurements at the Hanford Site showed133Xe and 135Xe levels indicative of 240Pu spontaneous fission. Stablexenon isotopic ratios from fission are distinct from atmospheric xenonbackground. Neutron capture by 135Xe produces an excess of 136Xe inreactor-produced xenon providing a means of distinguishing spent fuelfrom separated transuranic materials

Prediction of land subsidence due to groundwater withdrawal in Las Vegas Valley, Nevada

Online access for this thesis was created in part with support from the Institute of Museum and Library Services (IMLS) administered by the Nevada State Library, Archives and Public Records through the Library Services and Technology Act (LSTA). To obtain a high quality image or document please contact the DeLaMare Library at https://unr.libanswers.com/ or call: 775-784-6945.A one-dimensional finite-difference model that simulates vertical compaction (consolidation) due to groundwater withdrawal is applied to two sites in Las Vegas Valley, Nevada. The input to the model consists of interpreted water level records and driller’s lithologic logs. The calibrated constant parameters, vertical hydraulic conductivity and virgin specific storage of the compacting clay beds, are back-calculated with historical subsidence data from survey levelings. Although there are no definitive water level or lithologic records at either site, a broad range of possible input values predicts 4 to 16 cm of subsidence at one site from 1990-2000, and 11 to 63 cm at another site during the same period. Lithologic data are the weakest component of the study and deserve priority in future modeling efforts. The model can be used as a groundwater management tool to aid in planning placement and intensity of pumping and artificial recharge in Las Vegas Valley to minimize land subsidence

Simulation of vegetation and hydrology for climate change analysis of a mountain watershed

Climate change is expected to have both direct and indirect effects on water resources. Hydrologic impacts of two indirect effects, vegetation density and stomata! conductance, are evaluated for the American River, a 200 km² watershed in the Cascade Range of Washington state. First, a set of distributed hydrology-biogeochemistry model structures are created by coupling DHSVM (Distributed Hydrology-Soil-Vegetation Model) and Biome-BGC (BioGeochemistry Cycles). The model structures are applied to idealized hillslopes and current and future climate scenarios for the watershed. Eleven model structures, differing in vertical 1-D hydrology parameterization, lateral water routing, timestep, slope and aspect, are tested. Sensitivity of hydrology and vegetation density (as measured by leaf area index, LAI) is evaluated with respect to model structure, lapsed climate (elevation), climate change, and soil thickness and nitrogen input rate. Lapsed climate accounts for the largest range in LAI, but choice of model structure is also significant, highlighting opportunities and problems in model development. LAI is water-limited at low elevations, temperature-limited at high elevations, and solar-limited at all elevations. All model structures predict increased LAI under the future scenario that includes reduced stomatal conductancethe conifer forest grows denser. Next, climate scenarios and LAI results from the idealized hillslope simulations are input to the hydrology model DHSVM for hydrologic analysis of the full American River watershed. Basin-average annual precipitation, streamflow, and evapotranspiration all increase under the future climate scenario. The direct effect of increased temperature causes the major hydrologic impact, reduced snowpack and altered seasonal timing of streamflow and ET. Indirect effects of altered LAI and stomatal conductance on hydrology are minor in comparison to the direct effects. Future streamflow and ET are essentially the same between the simplest treatment of climate change, involving fixed LAI and physical climate change only, and the most detailed treatment, involving variable LAI and reduced stomatal conductance in addition to physical climate change

Hydrodynamic Simulation of the Columbia River, Hanford Reach, 1940--2004

Many hydrological and biological problems in the Columbia River corridor through the Hanford Site require estimates of river stage (water surface elevation) or river flow and velocity. Systematic collection of river stage data at locations in the Hanford Reach began in 1991, but many environmental projects need river stage information at unmeasured locations or over longer time periods. The Modular Aquatic Simulation System 1D (MASS1), a one-dimensional, unsteady hydrodynamic and water quality model, was used to simulate the Columbia River from Priest Rapids Dam to McNary Dam from 1940 to 2004, providing estimates of water surface elevation, volumetric flow rate, and flow velocity at 161 locations on the Hanford Reach. The primary input data were bathymetric/topographic cross sections of the Columbia River channel, flow rates at Priest Rapids Dam, and stage at McNary Dam. Other inputs included Yakima River and Snake River inflows. Available flow data at a gaging station just below Priest Rapids Dam was mean daily flow from 1940 to 1986 and hourly thereafter. McNary dam was completed in 1957, and hourly stage data are available beginning in 1975. MASS1 was run at an hourly timestep and calibrated and tested using 1991--2004 river stage data from six Hanford Reach locations (areas 100B, 100N, 100D, 100H, 100F, and 300). Manning's roughness coefficient in the Reach above each river recorder location was adjusted using an automated genetic algorithm and gradient search technique in three separate calibrations, corresponding to different data subsets, with minimization of mean absolute error as the objective. The primary calibration was based on 1999, a representative year, and included all locations. The first alternative calibration also used all locations but was limited in time to a high-flow period during spring and early summer of 1997. The second alternative calibration was based on 1999 and included only 300 Area stage data. Model goodness-of-fit for all years with data was high in the primary calibration and indicated little bias caused by selecting 1999. The alternative calibrations led to improved goodness-of-fit for their limited time and locations, but degraded goodness-of-fit overall. Overall, the simulations were very accurate and even highlighted some probable data problems, as evidenced by systematic shifts in the data. Further improvements in simulating the historic period would depend on correcting these inferred data problems. For all years and locations, the mean absolute error in the primary calibration was 14.8 cm, the mean error was 1 mm, and model efficiency was 0.988. The MASS1 output for 1940--2004 can be used to reconstruct historical river elevations at Hanford or to build scenarios of future river elevations for solving environmental problems such as groundwater-river interaction or fish habitat inventories. Model output and additional processing services are available from the authors. Longer-term scenarios extending more than a few decades from now should also consider the impacts of climate change and reservoir operation change. Once defined, these impacts could be used to drive new simulations with MASS1

2004 Initial Assessments of Closure for the S-SX Tank Farm: Numerical Simulations

In support of CH2M HILL Hanford Group, Inc.'s (CHG) preparation of a Field Investigative Report (FIR) for the closure of the Hanford Site Single-Shell Tank (SST) Waste Management Area (WMA) tank farms, a set of numerical simulations of flow and solute transport was executed to investigate different potential contaminant source scenarios that may pose long-term risks to groundwater from the closure of the S-SX Tank Farm. This report documents the simulation of 7 cases (plus two verification) involving two-dimensional cross sections through the S Tank Farm (Tanks S-101, S102, and S-103) and the simulation of one case involving three-dimensional domain of the S Tank Farm. Using a unit release scenario at Tank S-103, three different types of leaks were simulated. These simulations assessed the effect of leaks during retrieval as well as residual wastes and ancillary equipment after closure. Two transported solutes were considered: uranium-238 (U-238) and technetium-99 (Tc 99). To evaluate the effect of sorption on contaminant transport, six different sorption coefficients were simulated for U 238. Overall, simulations results for the S Tank Farm showed that only a small fraction (< 0.4%) of the U-238 with sorption coefficients 0.6 mL/g migrated from the vadose zone in all of the cases. For the conservative solute, Tc-99, results showed that the simulations investigating leaks during retrieval demonstrated the highest peak concentrations and the earliest arrival times due to the high infiltration rate before water was added and surface barriers installed. Residual leaks were investigated with different release rate models, including uniform release, advection-dominated, diffusion-dominated, and saltcake (solubility-controlled) release models. Of the four models, peak concentrations were lowest and arrival times later for the uniform release model due to the lower release rate of the residual tank waste solids; similar high peak concentrations occurred for the advection-dominated and the salt cake models due to the higher release rate. For the tank ancillary equipment leak case, the diffusion-dominated release rate model yielded peak concentrations and arrival times that were similar to the majority of the past leak cases for residual tank wastes. Comparison between the results of the two-dimensional and those of the three-dimensional simulations show that the two-dimensional simulation significantly overestimated the peak concentrations of the contaminants by a factor of about 41 for Tc-99 and 37 for U-238 with sorption coefficient of 0.03 mL/g

Analysis of Flood Hazards for the Materials and Fuels Complex at the Idaho National Laboratory Site

Researchers at Pacific Northwest National Laboratory conducted a flood hazard analysis for the Materials and Fuels Complex (MFC) site located at the Idaho National Laboratory (INL) site in southeastern Idaho. The general approach for the analysis was to determine the maximum water elevation levels associated with the design-basis flood (DBFL) and compare them to the floor elevations at critical building locations. Two DBFLs for the MFC site were developed using different precipitation inputs: probable maximum precipitation (PMP) and 10,000 year recurrence interval precipitation. Both precipitation inputs were used to drive a watershed runoff model for the surrounding upland basins and the MFC site. Outflows modeled with the Hydrologic Engineering Centers Hydrologic Modeling System were input to the Hydrologic Engineering Centers River Analysis System hydrodynamic flood routing model

Integrated Modeling Approach for the Development of Climate-Informed, Actionable Information

Flooding is a prevalent natural disaster with both short and long-term social, economic, and infrastructure impacts. Changes in intensity and frequency of precipitation (including rain, snow, and rain-on-snow) events create challenges for the planning and management of resilient infrastructure and communities. While there is general acknowledgment that new infrastructure design should account for future climate change, no clear methods or actionable information are available to community planners and designers to ensure resilient designs considering an uncertain climate future. This research demonstrates an approach for an integrated, multi-model, and multi-scale simulation to evaluate future flood impacts. This research used regional climate projections to drive high-resolution hydrology and flood models to evaluate social, economic, and infrastructure resilience for the Snohomish Watershed, WA, USA. Using the proposed integrated modeling approach, the peaks of precipitation and streamflows were found to shift from spring and summer to the earlier winter season. Moreover, clear non-stationarities in future flood risk were discovered under various climate scenarios. This research provides a clear approach for the incorporation of climate science in flood resilience analysis and to also provides actionable information relative to the frequency and intensity of future precipitation events