Performance Monitoring to Assess Environmental System Behavior II Posters
Presiding: T J Nicholson, Office of Nuclear Regulatory Research, U.S. Nuclear Regulatory Commission; R Ford, Robert S. Kerr Environmental Research Center, U.S. Environmental Protection
H43C-01 1330h
Web Based Autonomous Geophysical/Hydrological Monitoring of the Gilt Edge Mine Site: Implementation and Results
The Ruby Gulch repository at the Gilt Edge Mine Superfund site is a capped waste rock repository. Early in the system design EPA and its subcontractor, Bureau of Reclamation, recognized the need for long-term monitoring system to provide information on the repository behavior with the following objectives: 1 Provide information on the integrity of the newly constructed surface cover and diversion system 2 Continually assess the waste's hydrological and geochemical behavior, such that rational decisions can be made for the operation of this cover and liner system 3 Easily access of information pertaining to the system performance to stakeholders 4 Integration of a variety of data sources to produce information which could be used to enhance future cover designs. Through discussions between EPA, the Bureau of Reclamation and Idaho National Laboratory a long-term monitoring system was designed and implemented allowing EPA to meet these objectives. This system was designed to provide a cost effective way to deal with massive amounts of data and information, subject to the following specifications: 1 Data acquisition should occur autonomously and automatically, 2 Data management, processing and presentation should be automated as much as possible, 3 Users should be able to access all data and information remotely through a web browser. The INL long-term monitoring system integrates the data from a set of 522 electrodes resistivity electrodes consisting of 462 surface electrodes and 60 borehole electrodes (in 4 wells with 15 electrodes each), an outflow meter at the toe of the repository, an autonomous, remotely accessible weather station, and four wells (average depths of 250 feet) with thermocouples, pressure transducers and sampling ports for water and air. The monitoring system has currently been in operation for over a year, and has collected data continuously over this period. Results from this system have shown both the diurnal variation in rockmass behavior, movement of water through the waste (allowing estimated in residence time) and are leading to a comprehensive model of the repository behavior. Due to the sheer volume of data, a user driven interface allows users to create their own views of the different datasets.
H43C-02 1330h
Developing a Framework for Performance Monitoring to Assess the use of Monitored Natural Attenuation for Remediation of Inorganic Contaminants in Ground Water
The USEPA is leading an effort to develop technical documentation that provides the policy, scientific and technical framework for assessing the viability of MNA for inorganic contaminants in ground water (hereafter referred to as the Inorganics Framework Document). Development of the Inorganics Framework Document is being carried out in conjunction with site-specific assessments of the viability of MNA at sites with ground water contamination. For one of these field sites, researchers at the National Risk Management Research Laboratory are assessing the potential for natural attenuation of arsenic within a contaminated ground-water aquifer. Based on the current state of knowledge, arsenic is considered to be a contaminant for which application of MNA may be of marginal success. The mobility of arsenic in ground water is strongly dependent on partitioning to immobile aquifer solids. However, arsenic is susceptible to changes in chemical speciation due to shifts in redox chemistry resulting from abiotic and biotic processes. These potential changes in chemical speciation require that detailed information for assessing the stability of immobilized arsenic be collected in space and time. This observation has been confirmed as part of the field study, where it has been established that partitioning to sediments results in significant removal of arsenic from the aqueous phase. However, the partitioning process is readily reversible under reducing conditions, indicating that MNA cannot be used as a sole remedy for site cleanup. Notice: This is an abstract of a proposed presentation and does not necessarily reflect EPA policy.
H43C-03 1330h
Testing an Integrated Ground-Water Monitoring Strategy for Nuclear Waste and Decommissioning Sites
This talk discusses a Nuclear Regulatory Commission-sponsored research project designed to develop an integrated and systematic strategy for monitoring ground-water flow and transport through the unsaturated zone to the underlying water-table aquifer at waste disposal sites. The goal is to provide scientifically-based guidance for monitoring across a wide range of geologic settings, waste compositions, and site designs. The monitoring will specifically support performance assessment studies and modeling. The research objectives include: (1) the strategy will couple performance confirmation monitoring to site characterization and performance assessment, and will consist of an ordered and logical sequence of procedures; (2) the research will develop the technical bases as citable references, identified guidance and analytical tools, and test case applications of the developed integrated ground-water monitoring strategy for confirming performance of nuclear waste and decommissioning sites; (3) this strategy will focus on identifying and monitoring critical performance indicators (e.g., water contents over time in the unsaturated zone, and ground-water potentials in the saturated zone) of the hydrologic system; and (4) the strategy will demonstrate the connection between performance indicators and site performance. The monitoring strategy has been developed in draft form, and the testing phase of this work is beginning. The test plan includes: 1. develop testing objectives; 2. develop success criteria based on objectives; 3. select test datasets from field sites; 4. apply the draft strategy to field data; 5. feed-back for strategy improvement. Testing objectives will include: 1. develop rules for selection of performance indicators; 2. evaluate efficient methods to develop conceptual site models; 3. develop rules for selection of monitoring points (in the spatial and temporal domain) and rules for identification of monitoring approaches (e.g., geophysical methods) and techniques; 4. develop criteria for "essential elements of information" (minimal data requirements); 5. develop rules for data analysis - selection and application of appropriate data review, analysis and statistical testing methods (e.g., trend analyses) and; 6. integrate rules into a graded approach to application of the monitoring strategy. This paper will lay out the strategy and test plan in more detail, and discuss testing progress.
http://www.advenvsoln.com/agu05H8b.htm
H43C-04 1330h
Evaluating Conceptual Site Models with Multicomponent Reactive Transport Modeling
Modeling ground-water flow and multicomponent reactive chemical transport is a useful approach for testing conceptual site models and assessing the design of monitoring networks. A graded approach with three conceptual site models is presented here with a field case of tetrachloroethene (PCE) transport and biodegradation near Charleston, SC. The first model assumed a one-layer homogeneous aquifer structure with semi-infinite boundary conditions, in which an analytical solution of the reactive solute transport can be obtained with BIOCHLOR (Aziz et al., 1999). Due to the over-simplification of the aquifer structure, this simulation cannot reproduce the monitoring data. In the second approach we used GMS to develop the conceptual site model, a layer-cake multi-aquifer system, and applied a numerical module (MODFLOW and RT3D within GMS) to solve the flow and reactive transport problem. The results were better than the first approach but still did not fit the plume well because the geological structures were still inadequately defined. In the third approach we developed a complex conceptual site model by interpreting log and seismic survey data with Petra and PetraSeis. We detected a major channel and a younger channel, through the PCE source area. These channels control the local ground-water flow direction and provide a preferential chemical transport pathway. Results using the third conceptual site model agree well with the monitoring concentration data. This study confirms that the bias and uncertainty from inadequate conceptual models are much larger than those introduced from an inadequate choice of model parameter values (Neuman and Wierenga, 2003; Meyer et al., 2004). Numerical modeling in this case provides key insight into the hydrogeology and geochemistry of the field site for predicting contaminant transport in the future. Finally, critical monitoring points and performance indicator parameters are selected for future monitoring to confirm system performance.
http://www.advenvsoln.com/agu05H08a.htm
H43C-05 1330h
Protocol for Quantifying a Solute Mass Flux in Shallow Groundwater
Field solute transport studies inferring the relevance of matrix and preferential flow processes are common but actual flux measurements quantifying their impact are essentially nonexistent. To fully understand solute transport and develop theory to describe their behavior and impact, it is crucial to first quantitatively determine a total solute flux, including when preferential flow becomes active. As a result, to quantify a total solute flux leaching from matrix and preferential flow processes must be simultaneously monitored. A protocol extending a flux method previously developed for tile-drained systems was tested for shallow ground water systems without a tile drain. A bromide flux was monitored that represented a treated soil area of about 30 m2, which was subsequently subjected to a 4.1 mm/h irrigation rate. Results indicated that: 1) over 98 percent of the applied bromide tracer was recovered; 2) at 4.1 mm/h over half of the surface-applied bromide was recovered at a depth of 1.6 m after only 280 mm of irrigation; and 3) at this location, bromide fluxes were dominated by preferential flow when subjected to a 4.1 mm/h irrigation rate. Preliminary results suggest this protocol may be a useful tool for quantifying solute transport fluxes in non tile-drained systems.
H43C-06 1330h
Using Temporal Persistence to Improve Monitoring and Upscale of Soil Moisture Contents
When a field or a small watershed is repeatedly surveyed for soil water content, sites often can be spotted where soil is consistently wetter or consistently dryer than average across the study area. The phenomenon has been called time stability, temporal stability, or temporal persistence in spatial patterns of soil water contents. It was shown that such persistence can be used to optimize monitoring and upscaling of soil moisture. Relatively less is known about temporal persistence of water content at various depths in vadose zone. The objectives of this work are to demonstrate the temporal persistence in soil water contents measured on a vertical two-dimensional grid, and to propose a technique to utilize this persistence to monitor and upscale soil water content. Sixty TDR probes (two-rods) were installed along the trench in loamy soil at 12 locations with 50-cm horizontal spacing at 5 depths (15, 35, 55, 75, and 95 cm). Some probes at a given depth consistently showed water contents below average whereas others show water contents above the average. To quantify the persistence, we computed relative water contents as ratios of individual-probe water contents to average water contents from the same depth. The number of probes could be decreased and the soil water content could be upscaled much more efficiently because the variability ranges of relative water contents were narrow. A numerical experiment showed the efficiency of the proposed technique. Corrections for temporal persistence can be useful to improve estimates of layer-averaged water contents and their uncertainty.
H43C-07 1330h
Monitoring Non-point Source Pollution using the Reference Condition Approach: A Case-study from the Minnesota River Basin
Non-point source (NPS) pollution, primarily by nutrients, sediment, and bacteria, is of concern throughout the U.S.A. Agriculture has been identified as a major component of NPS loading to the nation's waterways and several conservation programs have been incorporated into natural resources management to help curb the effects of NPS pollution from agricultural practices. Effective implementation of such programs requires monitoring strategies that foster better understanding of how water quality is affected by land use change. Those monitoring programs require precise definition of `reference condition', a term that must be locally calibrated and have regional inferential capability. That need for simultaneous local and regional utility poses a challenge. We developed a tool using the `reference stream' approach for determining least-impacted stream links in landscapes dominated by agriculture. We applied our method to watersheds in the Minnesota River Basin where a significant proportion of the land is devoted to agricultural practices. The result is a tested design metric that facilitates selection of reference conditions for judging the effectiveness of conservation programs.