A closed landfill in Antioch, California, potentially had contaminates of concern migrating off-site and moving toward a residential neighborhood. SEC designed a methodology that utilized a pilot-study intercept wall, comprised of installing an impermeable barrier as deep as 120’ below grade. The trench necessitated a slurry support method, that allowed the trench to remain open until the appropriate depth was reached, and then allow for the installation of the membrane. The unique excavation method, utilizing a hydraulically-driven clamshell mounted upon a cable crane, required precise equipment placement, and intricate preparation of the excavation borders.
When combined with the engineered bentonite and Portland slurry wall, these two elements would ensure no offsite migration of liquids or gases would occur. This deep-trench excavation method, combined with the membrane installation, had never before been performed in the Western Hemisphere, and it was the single deepest application ever completed in the world. By teaming with a long-term partner, we were able to introduce the methods and equipment and operators from Europe, and successfully completed the pilot study, in furtherance of installation of a wall to completely surround the site.