D.J. Scheffler, a deep foundation drilling contractor based in Southern California, began constructing the Lower Mission Creek retaining walls in mid June 2011 and completed its drilling work on October 31.
Led by the Santa Barbara County Flood Control District, the City of Santa Barbara, and the U.S. Army Corps of Engineers, the erosion control and beautification project will prevent the flooding of the channel into the community, and improve vegetation and wildlife habitat in and around the creek.
The retaining walls were needed to widen the creek and increase the flow capacity of the channel by approximately 3,400 cubic feet per second. The new walls were constructed by drilling 24” diameter concrete secant piles, each approximately 40 feet, into the ground. More than 250 piles were needed to construct roughly 450 linear feet of wall located on both sides of the inlet.
D.J. Scheffler used the continuous flight auger (CFA) method to construct the walls. CFA is a method where the auger is drilled to depth and is extracted under constant concrete pressure pumped through the hollow center of the auger tool. Therefore the drilled shaft is never unsupported and the surrounding area is not disturbed. Once the pile is concreted, a rebar cage is placed while the concrete is still fluid.
“CFA is ideal for environments with high water tables, caving soils, or possible subsidence issues. You can construct a finished pile without the potential problems and risks associated with an open shaft,” said Dale Scheffler, president of D.J. Scheffler. “We are seeing more public works projects specify the CFA method, as government agencies and their consultants are realizing how time and cost efficient, and reliable this method of pile construction can be.”