Currently, work at the NDA involves the installation of a slurry wall to reduce ground water inflitration. To install the slurry wall a trench is being excavated along the west and south sides of the NDA. The trench trench is being backfilled with a mixed slurry of soil and bentonite clay, which has elastic properties that make it nearly impermeable to water. A membrane cover will be placed over the NDA later this year, to further reduce runoff infiltration. In the photo to the right, a bag of bentonite clay is being emptied into a portable mixer to make the slurry.