As a subconsultant to GeoPentech, Bennett Trenchless designed a 2,960-foot HDD bore for installation of a 12-inch steel recycled water pipeline to supply a new recycled water storage tank at the top of Griffith Park. The design of the HDD bore was especially challenging due to the 510-foot elevation difference between entry and exit. Ground conditions consisted of predominantly granodiorite with Monterey Formation (silty shale), with a section of potentially unstable landslide deposits near the exit point. The available work area near the exit point was severely limited due to dense vegetation and steep topography, resulting in a maximum pipe layout area of approximately 175 feet. The resulting design required 17 intermediate welds during pullback.
Bennett Trenchless evaluated the feasibility of HDD, conducted hydrofracture risk analyses, provided input to planning level cost and construction schedule estimates, prepared drawings, provided technical specifications, and co-authored a Geotechnical Baseline Report for the trenchless components of the project. Bennett Trenchless also provided engineering services during construction, including submittal review, response to RFIs, and full-time on-site specialty trenchless construction inspection. Construction was successfully completed on the HDD bore in the late summer of 2017.