Technology
Environmental Management
Interim Barrier
Interim barriers, designed to prevent rain and snow melt from percolating into the soil and driving contaminants closer to the water table have been installed over two tank farms and plans are being readied to install additional barriers over at least two additional farms. The barriers are temporary structures constructed under terms of the Tri-Party Agreement and are among several interim measures taken to improve protection of the groundwater from previous tank and pipe leaks.
The barriers will remain in place until a final closure decision is made for the farms. One barrier covers portions of the T Farm wre tank T-106 experienced a leak of 115,000 gallons, making it the largest leak in the history of the Hanford Site. A second barrier covers nearby TY Farm which as also the site of tank leaks. Unlike the T Farm barrier which was constructed of multiple layers of soil, geotextile fabric and a polyurea layer, the barrier over TY Farm is constructed of modified asphalt.
Surface Geophysical Exploration
Surface Geophysical Exploration (SGE) is helping to improve our understanding of the nature and extent of soil contamination beneath Hanford’s underground waste storage tanks. Our goal is to understand the contamination so action can be taken to protect public health and the environment. SGE requires no excavation. Instead, it uses steel probes inserted into the soil in a grid pattern over a suspected contaminant plume. The probes are connected to a central data collection system which passes electrical currents between them. A plume can be identified and its boundaries mapped because soil impacted by waste conducts electrical current differently than dry or uncontaminated soil.
Off-Riser Sampler System
The Off-Riser Sampler improves our ability to obtain residual waste samples from our underground storage tanks following completion of waste retrieval activities. Historically, sample collection was restricted to waste materials that could be accessed directly beneath a tank riser. Material not near a riser was out of reach. With the new Off-Riser Sampler, operators can reach in and around obstacles to collect residual waste material anywhere in a tank. The remotely-operated device is being further enhanced with an on-board camera so operators will not have to rely on separate in-tank cameras to locate the waste and control the device.
Direct Push Technology
Direct Push is a significant advancement over conventional cone penetrometer equipment to obtain data and soil samples of contaminant plumes around and beneath underground storage tanks and other structures. Penetrometers, which have been used for years to perform shallow soil investigations, rely on the 30-45 ton weight of trucks that force a hollow rod vertically into the soil. Direct Push, on the other hand, uses a hydraulic hammer mounted on a small backhoe unit to drive a rod into the soil either vertically or at an angle. Monitoring instruments can then be lowered into the rod to obtain data on soil contaminants. The rod can also be equipped with a special device to bring soil samples to the surface for more detailed analysis. Direct push can also install electrical probes to be used with Surface Geophysical Exploration techniques to map waste plumes in the soil. Direct push minimizes worker contact with contaminants. It also has the advantage of being able to obtain samples beneath structures, significantly improving our ability to obtain data in areas that would otherwise be inaccessible.
