Cecelia Williams, principal investigator for the Environmental Measurement While Drilling system, is enthusiastic about EMWD because of its proven ability to obtain real-time data on cesium contamination levels during drilling operations. The demonstration took place in April at the U.S. Department of Energy's Savannah River Site in South Carolina at the F-Area Retention Basin. DOE's Office of Science and Technology through the subsurface contaminants focus area, or SCFA, financed the demonstration. Work was conducted by personnel and crew from Sandia National Laboratories, Westinghouse Savannah River Company, and Geneva Corporation using Ditch Witch equipment. SCFA was recently formed by combining the landfill stabilization and plume focus areas.

Williams said, "We integrated commercially available, off-the-shelf sensors with a telemetry system, coaxial cable coil, and data reduction and display software transitioned from defense programs, to develop an innovative tool for site characterization in real-time while drilling. The tool allows for on-the-spot field screening, which means we can identify clean areas from contaminated areas and advise DOE's Environmental Restoration personnel where to obtain soil samples that are sent for off-site confirmatory analyses. This [technology] has the potential of significantly reducing the number of samples sent off-site for analysis, thereby saving money and time."

According to Williams, EMWD's real-time collection and analysis of data means that information on contamination is available in minutes, as opposed to weeks or months from an off-site laboratory. Having immediate access to data speeds up the environmental restoration operation, contributes to safer working conditions, and reduces the costs of restoration. Sensors located behind the drill bit are linked by a high-speed data transmission system to a computer at the surface. Sandia National Laboratories developed the Microsoft Windows-based software that is used for data display and storage. As drilling is conducted, EMWD collects data on the nature and extent of contamination, drill bit location, and temperature, enabling on-the-spot decisions regarding subsequent drilling and sampling strategies.

During its demonstration at the Savannah River Site on April 22-25, 1996, the EMWD system was outfitted with a gamma ray spectrometer. The team drilled one background bore at a cold site and two bores into the F-Area Retention Basin. The team determined its drilling strategy by examining sampling data previously obtained from the site and by surveying the sampling locations. They selected the appropriate depth as 12 to 14 feet, since this was the depth showing the highest cesium-137 contamination from previously taken samples.

The crew began its horizontal drill from an entry trench dug by a Ditch Witch machine. They drilled approximately 66 feet from the wall of the trench and intersected a sampling point from which Westinghouse Savannah River personnel had previously obtained the highest cesium-137 gamma samples. Using a gamma ray spectrometer located behind the drill bit, the team recorded data continuously while drilling. At the WSRC sampling point location, the EMWD system detected cesium-137 counts 25 times that of background, thus agreeing with off-site analysis data previously obtained from the site. The team observed the counts of cesium-137 increase as they approached the hot spot and drop off as they moved away from it.

The crew continued drilling to a second sample point, but the EMWD system did not detect any cesium-137 in that area. However, at 10 feet from this sample point, the team detected cesium-137 at a level five times that of background--a new hot spot not previously mapped. As they drilled another 10 feet, the count dropped. The crew ended its drilling operation at this point and began their pull back, or retreat, through their subsurface path.

The pull back was as successful as the environmental-measuring-while-drilling operation had been. Due to the possibility of contamination, the crew dressed out in full protective clothing for the pull back. All the pull back soil on the drill rod was contained in the trench, which was both the entry and exit point for the demonstration. The Ditch Witch crew used a drill rod wiper, an instrument they engineered, to remove most of the soil; and then they used paper to wipe the rods clean. The radiation control officer checked for contamination on the drill rods using a gamma detector and a beta/gamma detector. She also took swipes from each drill rod and other critical areas in the trench. All results were negative. The pull back operation successfully concluded with contaminated soil contained in the trench and drill rods completely decontaminated.

This demonstration was one step in the overall project to produce a prototype system that costs less than $15,000. Operations and maintenance costs are likely to be low, while recurring costs will be limited to a spool of coaxial wire for each drilling operation. Its low cost and generic design offer maximum flexibility to integrate additional sensors. Charles Machine Works, Inc. of Perry, Oklahoma (makers of Ditch Witch) is collaborating with Sandia National Laboratories to develop the EMWD system.

Sandia has analyzed the market to determine EMWD's potential use in the environmental, oil, and utility industries. The system will be available for licensing in late 1996.