Information Resources: Conventional seepage cutoff walls are typically constructed using an excavator with a long-stick boom capable of digging a trench to a maximum depth of approximately 85 feet. Excavated soil is then mixed with bentonite clay (and sometimes cement) to achieve the required cutoff wall strength and permeability properties, and is backfilled into the trench. The deep-mix method of seepage cutoff wall construction differs from the conventional trench method in that the existing subsurface soils are mixed in place with cement and bentonite injected through augers to provide the low permeability barrier. Most seepage cutoff walls are constructed using the conventional method with a deep stick excavator. If it’s determined that a seepage cutoff wall deeper than 85 feet is required, then the deep-mix method will be applied if there’s sufficient working space. For Sacramento River East Levee Contract 3 work this summer, we’ll be using both of these methods.