Sandia National Laboratories
Description
SEAMIST is an instrumentation and fluid sampler emplacement
technique designed for in situ characterization and monitoring. It uses an
inverting, pneumatically deployed tubular membrane (impermeable material) to
install sampling devices and instruments in boreholes.
The membrane is forced into a drilled or punched well due to by pressure. The membrane descends, everts, and presses against the hole wall, providing wall support and the effect of a continuous packer. After emplacement, the entire hole wall is sealed, thus preventing ventilation of the pore space or circulation of pore water in the well. The membrane can be retrieved from the hole.
Monitoring instruments and pore fluid sampling devices are placed on the outer surface of the membrane, in contact with the hole wall. The membrane isolates each measurement location. Emplacement has been demonstrated for vertical, horizontal, and crooked or partially obstructed holes. Instruments or samplers are not dragged along the hole wall at any time.
Permanent installation of the membrane is possible by filling the membrane with grout after emplacement. Semi-permanent installation can be accomplished by filling the membrane with sand after emplacement.
The membrane can be applied to perform vadose zone pore and fracture liquid sampling through the use of absorbent pads. Electrical resistance measurements inside the pads indicate moisture uptake. By attaching an array of absorbent pads to the membrane, high spatial resolution of the contaminant distribution is possible.
Extraction of soil gas samples from a hole can be accomplished via tubes to surface sample collectors, or getters, such as activated charcoal absorbers, can be attached to the membrane surface to absorb contaminants. A hybrid concept is to pull a gas sample through a filter positioned at the sampling point.
Air-permeability distribution within a soil matrix can be measured by emplacement of a membrane with several gas sampling ports. As the gas is pulled from one port to the surface, its flow rate and measured pressure response at the adjacent ports imply a local permeability distribution.
Additional instruments can be applied, such as temperature sensors, thermocouple psychrometers, and fiber-optic sensors. Calorimetric materials can be used for visual indications of contaminant distribution.
Technical Performance Data
Tritium Plume Monitoring. Two systems installed at Lawrence Livermore National Laboratory (LLNL) in 1991 are tracking the movement/concentrations of a tritiated water plume (vapor and liquid water sampling) to 40-ft depths.
Carbon Tetrachloride Monitoring. Two emplacement systems with disposable membrane liners are in use at Hanford for carbon tetrachloride plume monitoring.
Fracture Flow Mapping and Rate Measurement. Membranes coated with liquid-indicating and wicking layers were used to map and measure brine flows underground at the Waste Isolation Pilot Plant (WIPP).
Tritium and VOC Sampling. SEAMIST system
transported vapor sampling tubes and absorbent collectors 230 ft horizontally
beneath an old radioactive waste landfill at Los Alamos National Laboratory
(LANL).
SNL Integrated Demonstrations. Transported logging tools and cameras in horizontal boreholes of up to 230 ft length and 1.75 to 4.0 in. diameters. Performed gas sampling and permeability measurements in two boreholes of 11.5 in. diameter and 110 ft depth immediately after augering in SNL's CWL. Installed three borehole liners 110 ft long.
Vapor Sampling/Permeability Measurements. Three membranes were instrumented and installed at SRS in July 1992 for soil vapor, vapor pressure, and permeability measurements. Maximum depth was 130 ft, with ten sampling elevations per membrane.
Neutron Logging Tool Transport. The membrane towed a 3-lb neutron moisture logging tool in horizontal boreholes. Typically, four 4.5-in.-diameter holes (200-250 ft) were logged in one day, with data taken every 2 ft.
Vapor Sampling. A vapor sampling system was installed to 90-ft depths for long-term monitoring.
Borehole Liners. SEAMIST liners were
installed to support/seal holes while long-term monitoring system is
designed. Hole diameter was 8.5 in. and depths were 80 to 100 ft.
High Pressure Borehole Liners. Two Kevlar reinforced membranes were installed to a depth of 155 ft, then filled with water inside cased walls to prevent collapse of polyvinylchloride (PVC) casing during remediation experiments.
Cost. Membrane - $2K to $8K, depending on complexity; emplacement canisters and support sytems - $1K to $5K.
Projected Performance
Key performance parameters are listed below, including projections of near-term (1-3 yrs) performance.
Waste Applicability
Demonstrated measurement/monitoring of soils contaminated with tritium, carbon tetrachloride, and volatile organic compounds (VOCs).
Status
Regulatory Considerations
Regulatory considerations are a function of where the technology will be used, the nature of contamination, and the intended application of the technology.
Potential Commercial Applications
SEAMIST is commercially available for borehole lining,
liquid/vapor sampling, and permeability measurements. Potential near-term
applications, include water sampling below the water table; very long
(> 300 ft) horizontal deployment for landfill monitoring; pipe inspection,
characterization, and monitoring; and large-scale vapor plume movement
experiments/monitoring. The system can be used in both vertical and horizontal
pipes and conduits. The membrane can deploy through 45° and long-radius
90° elbows. It can pass over obstructions occupying one-half the pipe
diameter. These applications would be useful to utilities; the chemical,
mining, oil, and natural gas industries; Environmental Protection Agency (EPA)
and Department of Defense (DoD) cleanup operations; and various federal
Decontamination and Decomissioning (D&D) programs. SEAMIST
is also being considered for tritium monitoring in pipes.
Duets are being considered for D&D of Department of Energy (DOE)
facilities.
Baseline Technology
SEAMIST is a new technology. It replaces the need for ex
situ soil sample analysis. The membrane minimizes the likelihood of
contamination release from sampling and monitoring boreholes.
Intellectual Property Rights
Patent and Trademark Ownership: Eastman Cherrington Environmental, Houston, TX; Patent No. 5176207.
For more information, please contact:
References
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