Application of three aquifer test methods for estimating hydraulic properties within the 100-N Area (original) (raw)
Related papers
1991
Hydraulic conductivities were estimated from more than 1,500 aquifer-test analyses and more than 5,000 specific-capacity data from wells drilled into Tertiary and younger sediments of the Gulf Coast region in the south-central United States. The values are assumed to represent the coarser-grained sediments in the aquifer systems. The purpose of estimating hydraulic conductivities for this area is to compare these estimates to hydraulic conductivities determined from the simulation of regional groundwater flow as part of the Gulf Coast Regional Aquifer-System Analysis project. In the simulation model, hydraulic conductivities are separated into two groups: coarse-grained sediments (sands) and fine-grained sediments (silts and clays). Values for hydraulic conductivity range from less than 1 foot per day to more than 1,000 feet per day. The values are log normally distributed; thus, the geometric mean was used to represent a typical hydraulic conductivity. The geometric mean hydraulic conductivity for the entire study area was 55 feet per day from aquifer-test analyses and 71 feet per day from specific-capacity data. A two-way analysis of variance was performed on the combined estimates of hydraulic conductivity that were grouped into 10 model layers and 9 areas within the overall study area. Results of this analysis indicate that area, layer, and the interaction of area and layer were all significant in explaining the variation of hydraulic conductivity at a probability level of 0.001. Thus, comparisons of means were done for each area and layer combination. Overall, the highest geometric means generally were in model layer 11 which corresponds to the upper Pleistocene and younger deposits along the coast of the Gulf of Mexico and the alluvium of the Mississippi River. Within each model layer, the geometric mean increased from areas along the western part of the study area to the eastern part, which indicates that the deposits near the Mississippi River might be more permeable than elsewhere. Two separate analysis of covariance were performed on the estimates of hydraulic conductivity to determine if variations within each area and layer combination could be explained by depth of the well or by the thickness of sand beds throughout the perforated interval of the well. Results of these analyses indicate that depth to the middle of the perforated or screened interval was significant at the probability level of 0.02 and that sandbed thickness was not significant at the probability of 0.10. In the analysis with depth, hydraulic conductivity decreased as a function of depth in a majority of area and layer combinations.
A simple procedure for the identification of aquifer parameters based on steady-state pumping tests
IAHS-AISH publication, 2006
Résumé/Abstract Three-dimensional steady flow towards a fully penetrating well of radius rw, in a confined aquifer, is studied by means of a finite-volume numerical scheme. The hydraulic conductivity K is modelled as an axisymmetric, stationary random space function mimicking hydraulic property variations at the local scale. We develop a new methodology for the identification of the geostatistical model of variability from a steady-state pumping test involving a few wells. A constant water discharge is extracted from each well in sequence ...
Results of Detailed Hydrologic Characterization Tests - Fiscal Year 1999
2001
This report provides the results of detailed hydrologic characterization tests conducted within newly constructed Hanford Site wells during fiscal year 2002. Detailed characterization tests performed included groundwater-flow characterization, barometric response evaluation, slug tests, single-well tracer tests, constant-rate pumping tests, and in-well vertical flow assessments. Hydraulic property estimates obtained from the detailed hydrologic tests include hydraulic conductivity, transmissivity, specific yield, effective porosity, in-well lateral flow velocity, aquifer-flow velocity, vertical distribution of hydraulic conductivity (within the well-screen section), and in-well vertical flow velocity. In addition, local groundwater-flow characteristics (i.e., hydraulic gradient and flow direction) were determined for two sites where detailed well testing was performed. Results obtained from these tests provide hydrologic information that supports the needs of RCRA waste management area characterization and sitewide groundwater monitoring and modeling programs and reduces the uncertainty of groundwater-flow conditions at selected locations on the Hanford Site.
Summary and evaluation of hydraulic property data available for Eielson Air Force Base, Alaska
1994
Most of the contaminantsource areasat Eielson Air Force Base are located above an unconfined alluvial aquiferwith relativelyhigh hydraulicconductivity. Hydraulictests that have been conducted ,, on wells at the base were evaluated, and in some cases reanalyzed, to determinehydraulicconductivity and specific yield for the aquifer. The reviewed tests included 2 multiple-wellpumping tests and 30 slug tests. One slug test was conductedon a well in the bedrockaquiferat Site 38. All the other tests were conductedon the alluvial aquifer. Two slug tests performedon deeper wells in the alluvial aquifershowed an oscillatory responseand had not been previously analyzed. Reanalysis of the pumping tests and analysis of the two oscillating slug tests resultedin estimates of hydraulic conductivityranging from 240 to 1500 ft/d for the alluvial aquiferunderlying the developed portion of the base. Specific yield estimatesranging from 0.07 to 0.23 were determined from the pumping tests. The single slug test conducted in the bedrockaquiferresulted in an estimatedhydraulicconductivity of 1.2 Pt/d. Results of the other slug tests were not consideredvalid. Review of the previous pumpingtests indicatedthat the original analyses were not correctbecause type curves for an elastic unconfinedaquiferresponse were used, while the data indicatenonelastic unconfinedaquiferbehavior. Reanalysis of the pumpingtest data, using the appropriatetype curves, producedresults for hydraulicconductivitythat were within a factorof two of the original results. However, Closeragreementbetween the results at differentmonitoringwells was obtained for both tests. Also, estimatesof specific yield were obtained from reanalysis of the tests. Review of the slug tests indicatedthat only the test conductedon the bedrockaquifer andthe two oscillating slug tests gave reliable indicationsof hydraulicconductivity. Results of the other slug tests are not considered valid because of limitations of the slug test method for characterizinghighly permeable aquifersand, in some cases, because of shortcomingsin the data collection and analysis procedures. At best, the remainingslug tests may be used to indicatea minimumvalue for hydraulic conductivity. The actualhydraulicconductivityis thoughtto be significantly higher.
1988
A stochastic approach has been used to study the effects of spatial variability of aquifer characteristics on defining effective (uniform) aquifer model parameters. The parameters considered were hydraulic conductivity, riverbed leakance, and aerially distributed recharge. An unconfined aquifer model was constructed for an area similar to that near Livermore, California. Monte-Carlo realizations of the parameters were generated for different spatial correlation structures. Parameters were considered to have a support scale equivalent to that of the finite-difference blocks, except for the case involving local-scale conditioning. For each of the Monte-Carlo realizations, groundwater flow was simulated. Estimates of the mean (expected value) and standard deviation of hydraulic heads for all of the realizations were obtained. In all cases stationarity of the parameters was assumed and an exponential-type semivariogram was used. Several different cases were studied. The first set explored the influence of correlation length of hydraulic conductivity. The next inspected the impact of conditioning the Monte Carlo realizations upon either block-scale or local-scale hydraulic conductivity values. The remaining cases explored aerial zonation of hydraulic conductivity, riverbed leakance, and aerial recharge, respectively. For the cases that explored hydraulic conductivity, comparisons were made between simulations using the geometric mean and the spatially variable values. The most striking result was that the geometric mean of the hydraulic conductivity (a uniform value) did not produce the expected value of heads. Rather, an effective hydraulic * Also affiliated with U.S. Geological Survey.-217-conductivity value between the harmonic mean and the geometric mean led to the best match with the expected value of heads. The p-norm was used to describe the averaging process. The p-norm ranged from 1 for the arithmetic mean to-1 for the harmonic mean, with 0 representing the geometric mean. The-0.2 p-norm produced the best results for the conditional simulations and the-0.4 p-norm was best for the unconditional simulations. Deviations in simulated heads based upon the geometric mean hydraulic conductivity versus those based upon the spatially variable hydraulic conductivity realizations were greatest near the pumping wells. The standard deviations in heads from most of the various sets of flow simulations were over 5 meters at the wells and diminished to less than one meter in between the wells. The geometric mean produced heads at the wells that were consistently above the expected heads. Conditioning produced a considerable decrease in the standard deviation of heads at well locations. Without conditioning increasing the correlation length increases the standard deviations. With conditioning increasing the correlation length decreases the standard deviation. For riverbed leakance and aerially distributed recharge, an effective value between the arithmetic mean and geometric mean would likely produce the best match with the expected value of heads. Although the value would probably be nearer the arithmetic mean. These results may only apply to this system, however, we believe it is clear that use of the geometric mean as an effective hydraulic conductivity value may not be best in other realistic cases.
1993
Portions of this document may be illegible in electronic image products. Images are produced from the best available original document. Summary This report provides an update on the development of a three-dimensional conceptual model of groundwater flow in the unconfined aquifer system for the Hanford Site. The conceptual model will provide a basis for three-dimensional numerical modeling and will enable better understanding and more accurate predictions of contaminant transport under changing site conditions. The area included in the conceptual model has been extended to include the entire Hanford Site south and west of the Columbia River, and the area south of the Hanford Site to the confluence of the Yakima and Columbia rivers. The conceptual model within the earlier study area, south of Gable Mountain to the 300 Area, was also relined and updated. Geologic descriptions of samples from selected wells were interpreted to determine the extent and thickness of hydrogeologic units within the unconfined aquifer system. Nine hydrologically significant units were previously defined above the underlying basalt. These units have been extended into the expanded model area and refined within the previously defined area. Delinition of the units is based on textural differences that are expected to reflect differences in hydraulic properties. The geologic data have been entered into a geographical information system. Maps showing the extent of each unit are presented. Additional hydraulic property data were obtained by conducting aquifer tests at six wells. These and other available data were used to develop a new transmissivity distribution for the model area that is being applied in inverse calibration of the existing two-dimensional numerical flow model. A single value of hydraulic conductivity was assigned for mud-dominated units within the flow system. This was based on a few test results for the Hanfbrd Site and representative values presented in the literature. Additional geologic and water-level information was collected to help define the flow system boundary corresponding to the Yakima River. The lower reach of the river appears to have poor hydraulic communication with the unconfined aquifer. The range of possible recharge from Cold Creek and Dry Creek valleys also needs to be better defined. An aquifer test was conducted at well 699-43-104 and provides an estimate of hydraulic conductivity for the mouth of the Cold Creek Valley. However, the gradient in this area is uncertain. Possible methods of determining interflow between the unconfined and confined aquifer systems are being evaluated. Analysis for tritium and iodine-129 at the reconfigured "Golderl' well 699-18-21 is presented.
1994
Portions of this document may be illegible in electronic image products. Images are produced from the best available original document. Summary This report provides an update on the development of a three-dimensional conceptual model of groundwater flow in the unconfined aquifer system for the Hanford Site. The conceptual model will provide a basis for three-dimensional numerical modeling and will enable better understanding and more accurate predictions of contaminant transport under changing site conditions. The area included in the conceptual model has been extended to include the entire Hanford Site south and west of the Columbia River, and the area south of the Hanford Site to the confluence of the Yakima and Columbia rivers. The conceptual model within the earlier study area, south of Gable Mountain to the 300 Area, was also relined and updated. Geologic descriptions of samples from selected wells were interpreted to determine the extent and thickness of hydrogeologic units within the unconfined aquifer system. Nine hydrologically significant units were previously defined above the underlying basalt. These units have been extended into the expanded model area and refined within the previously defined area. Delinition of the units is based on textural differences that are expected to reflect differences in hydraulic properties. The geologic data have been entered into a geographical information system. Maps showing the extent of each unit are presented. Additional hydraulic property data were obtained by conducting aquifer tests at six wells. These and other available data were used to develop a new transmissivity distribution for the model area that is being applied in inverse calibration of the existing two-dimensional numerical flow model. A single value of hydraulic conductivity was assigned for mud-dominated units within the flow system. This was based on a few test results for the Hanfbrd Site and representative values presented in the literature. Additional geologic and water-level information was collected to help define the flow system boundary corresponding to the Yakima River. The lower reach of the river appears to have poor hydraulic communication with the unconfined aquifer. The range of possible recharge from Cold Creek and Dry Creek valleys also needs to be better defined. An aquifer test was conducted at well 699-43-104 and provides an estimate of hydraulic conductivity for the mouth of the Cold Creek Valley. However, the gradient in this area is uncertain. Possible methods of determining interflow between the unconfined and confined aquifer systems are being evaluated. Analysis for tritium and iodine-129 at the reconfigured "Golderl' well 699-18-21 is presented.
Results of Detailed Hydrologic Characterization Tests - Fiscal Year 2002
2003
This report provides the results of detailed hydrologic characterization tests conducted within newly constructed Hanford Site wells during fiscal year 2002. Detailed characterization tests performed included groundwater-flow characterization, barometric response evaluation, slug tests, single-well tracer tests, constant-rate pumping tests, and in-well vertical flow assessments. Hydraulic property estimates obtained from the detailed hydrologic tests include hydraulic conductivity, transmissivity, specific yield, effective porosity, in-well lateral flow velocity, aquifer-flow velocity, vertical distribution of hydraulic conductivity (within the well-screen section), and in-well vertical flow velocity. In addition, local groundwater-flow characteristics (i.e., hydraulic gradient and flow direction) were determined for two sites where detailed well testing was performed. Results obtained from these tests provide hydrologic information that supports the needs of RCRA waste management area characterization and sitewide groundwater monitoring and modeling programs and reduces the uncertainty of groundwater-flow conditions at selected locations on the Hanford Site.
Results of Detailed Hydrologic Characterization Tests - FY 1999/011
2001
This report provides the results of detailed hydrologic characterization tests conducted within newly constructed Hanford Site wells during fiscal year 2002. Detailed characterization tests performed included groundwater-flow characterization, barometric response evaluation, slug tests, single-well tracer tests, constant-rate pumping tests, and in-well vertical flow assessments. Hydraulic property estimates obtained from the detailed hydrologic tests include hydraulic conductivity, transmissivity, specific yield, effective porosity, in-well lateral flow velocity, aquifer-flow velocity, vertical distribution of hydraulic conductivity (within the well-screen section), and in-well vertical flow velocity. In addition, local groundwater-flow characteristics (i.e., hydraulic gradient and flow direction) were determined for two sites where detailed well testing was performed. Results obtained from these tests provide hydrologic information that supports the needs of RCRA waste management area characterization and sitewide groundwater monitoring and modeling programs and reduces the uncertainty of groundwater-flow conditions at selected locations on the Hanford Site.