CONCLUSIONS:

• This analysis gives a clear indication that the UFA Technology has an economic advantage over the baseline, and furthermore, that the baseline methods cannot even provide data for many of the conditions and situations for which the UFA can operate. The biggest savings are time and effort. The UFA can provide results in days instead of years as with the baseline methods. The UFA was developed so that maintenance costs are low.

• The time savings in analyzing 3,000 samples across the United States Department of Energy (USDOE) Complex is at least a factor of ten, i.e., twenty UFAs operating over five years versus ten baseline laboratories operating over fifty years. The cost savings depends strongly upon the project requirements and is related to the time savings and the increased quality of the results using the UFA method, but can also be estimated as a factor of five. However, because the UFA provides data not obtainable by the baseline methods for many situations and conditions of concern to DOE, and because the UFA can address expedited response actions and other time-dependant situations, the savings are actually much greater.

BACKGROUND:

There is a great need for understanding contaminant distribution and flow behavior in subsurface environments at DOE sites in order to develop effective site restoration strategies, expedited response actions, and defensible predictions of contaminant migration and impact. The UFA method is an innovative technology for rapidly and accurately determining the transport properties directly in almost any porous media such as soil, rock, cement, ceramic or sludge, with respect to almost any fluid, including water, waste effluent, oils and organic solvents. The most important transport properties requiring measurement are the hydraulic or fluid conductivity of any liquids (units of cm/s), the retardation factor or chemical behavior of the migrating contaminants, and the composition of the pore fluids. The alternative to the UFA method is to rely on extrapolations of contaminant behavior from less reliable assumptions which could result in a higher risk of not choosing the most appropriate restoration strategy for a particular situation. Inadequate predictive capability in this area will lead to loss of time, money, and credibility for DOE in meeting its long-term restoration goals. This technology has been demonstrated and is now commercially available.

The objective of this document is to evaluate the cost effectiveness of this technology versus the baseline technologies of traditional soil columns and curve-fitting estimation techniques. Evaluation is based upon references (1), (2), (3) and (4). The following are brief descriptions of the technologies

• Baseline Soil Columns
  This baseline technology consists of packing a hollow tube with the porous media and dripping fluid in the top at some fixed rate, and waiting for the flow rate out of the bottom to equal that rate, called hydraulic steady-state. Using traditional methods, the time required to reach hydraulic steady-state depends strongly upon the material, but is linear with the hydraulic conductivity, i.e., if it takes an ordinary soil 1 year to reach steady-state at 10^-7 cm/s, it will take 10 years to reach steady-state at 10^-8 cm/s, and 100 years to reach steady-state at 10-9 cm/s. Since it is necessary to attain steady-state at or below 10^-7 cm/s for materials at most western DOE sites, this can be time-prohibitive. To run experiments for years involves extensive space, time and manpower requirements that are difficult to maintain, and whose costs are not reflected in standard quotations and prices.

• Baseline Curve-Fitting Estimation Techniques
  This baseline technology consists of packing a hollow sample tube with the porous media, saturating with water, and allowing to drain over several weeks to months while measuring the capillary tension in the soil at regular intervals. This data is then subjected to two computer curve-fitting routines to estimate the unsaturated hydraulic conductivity. This technique is faster than the soil column method, but still requires several weeks. It is an estimation only and strongly depends upon several assumptions. Furthermore, this baseline technology cannot be used to set conditions for actual experiments on the porous media.

• The UFA Method
  The UFA technology consists of packing the porous media into a specially designed titanium canister which is subjected to large fluid driving forces up to 10,000 g in an open-flow centrifugation device. A rotating seal assembly allows an ultra-low flow pump to deliver fluid to the sample surface during rotation. Because of the large driving forces, steady-state is reached within hours even at hydraulic conductivities as low as 10^-11 cm/s, removing the traditional time barrier to these types of experiments. With rapid, direct measurements of transport properties possible for any porous media, the UFA can address issues facing expedited response actions, screening tests of formulations and material properties, and other problems needing immediate answers.

ASSUMPTIONS:

• The number of samples required to adequately characterize a site with respect to the transport and fate of contaminants in soils and rocks has never been quantified, but depends strongly upon the complexity of the subsurface. A conservative estimate is two samples per geologic unit. The number of soil and rock units underlying the DOE Complex, together with their heterogeneities and lateral discontinuities, makes the number of samples needing characterization in the tens of thousands. This large number of samples requires rapid and cost effective techniques of analysis if DOE sites are to be adequately characterized and remediated over the next 10 years.

• No sampling costs or costs of aqueous chemical analyses were included as these will be unaffected by the technology used.

ANALYSIS:

Comparisons of costs and time for the UFA method and baseline technologies are given in the Cost Comparisons Between Baseline and UFA Technologies Table. Information on traditional soil columns and curve-fitting estimations comes from standard references to the techniques, (1) and (2), from our own experience with these techniques, and from price lists of soil testing laboratories in the western United States of which the testing lab of Westinghouse Hanford Company is a competitive representation. No one has ever used traditional soil columns to measure hydraulic conductivities down to 10^-10 cm/s, but it is conservatively estimated to require over 20 years. The cost estimate for an experiment that long is very difficult and will surely exceed the conservative $20K given in the Cost Comparisons Between Baseline and UFA Technologies Table. Note that the baseline technologies cannot be used for certain applications (shown as NP in the Cost Comparisons Between Baseline and UFA Technologies Table), e.g., pore water extraction, and the estimation techniques are not experimental techniques and so cannot obtain experimental data for applications such as chemical retardation or non-aqueous phase liquid transport experiments.

Information on the UFA comes from our UFA Laboratory where the technique was developed and is discussed in references (3) and (4). Capital costs come from actual purchases, and maintenance costs come from actual experience.

PERSPECTIVES:

• The major benefit of the UFA technology is rapid, direct measurement of fluid transport properties, and, therefore, improved predictive capabilities of contaminant migration, greater probability of choosing successful restoration strategies, improved remediation schedules, and a reduced need in the future for lengthy experimental programs. This is difficult to quantify in terms of cost savings, but the inability to adequately determine these types of information in the past has been cited as a primary reason for our inability to remediate, or even evaluate, large contaminated sites.

• A major cost-benefit is the ability of the UFA method to obtain data on materials and situations not possible with baseline methods. Some limitations of the baseline technologies occur during applications to experiments such as chemical retardation of contaminants, e.g., radionuclides, heavy metals, and organics, which cannot be carried out under field conditions. Major time and cost savings occur with the UFA because baseline technologies take so long to reach steady-state at low water contents before the chemical experiments even begin. Maintaining control of the boundary conditions and chemistry over the years required to run an unsaturated retardation experiment, as an example, for uranium at 5% water, content is prohibitive. Yet the UFA can perform the same experiment in a few weeks, allowing great control over experimental conditions. In addition, extracting pristine pore water from highly unsaturated or impermeable samples has never been possible without significantly altering the chemical compositions as occurs with attempting to extract by squeezing or suction. However, the UFA can extract pore waters from highly unsaturated and impermeable materials without any chemical alteration and can achieve excellent yields, e.g., 95% from a sand at 3% water content.

APPLICABILITY:

As mentioned above, it is difficult to determine the number of samples across the DOE Complex that require characterization, but a conservative estimate can be placed at about 10,000. The UFA technology is essential if this number of samples are to be characterized over the next 10 years. Traditional methods cannot complete this task in that time frame or with the necessary degree of accuracy. However, 10 UFAs operating over 5 years could characterize the transport properties of the entire DOE Complex and provide the necessary information for any successful site restoration strategy and response actions well into the future. Total costs, including capital, for these 5 years would not exceed $10 million dollars. The alternative is to use the baseline methods at other laboratories, a sufficient number of which do not exist at this time. Gearing those labs up to speed in five years would cost in excess of $50 million dollars, and there is no gaurantee that the data collection could be achieved in 5 years.

REFERENCES:

(1) Klute, A. 1986. Methods of Soil Analysis, Second Edition, American Society of Agronomy, Inc., Madison, WI.

(2) van Genuchten, M. Th., F. J. Leij, and L. J. Lund. 1992. Indirect Methods for Estimating the Hydraulic Properties of Unsaturated Soils, University of California, Riverside, CA.

(3) Conca, J. L. and J. V. Wright (1992) "A New Technology for Direct Measurements of Unsaturated Transport", Proc. of the Nuclear and Hazardous Waste Management Spectrum '92 Meeting, American Nuclear Society, vol. 2, p. 1546-1555.

(4) Conca, J. L. and J. V. Wright (1992) "Flow and Diffusion in Unsaturated Gravel, Soil and Whole Rock", Applied Hydrogeology, vol. 1, p. 5-24.

©1996-12 UFA Ventures Inc.

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