The City of Thousand Oaks retained m6 Consulting Inc. to provide consulting and engineering services for the Hill Canyon Treatment Plant (HCTP) existing retaining walls replacement and improvements project. The project will replaced approximately 650 linear feet of existing retaining walls that were non-uniform in construction and failing in several locations. The southeast border of the plant contained sections with no retaining walls, walls comprising of metal posts and stacked pressure treated lumber battens, and walls consisting of reinforced masonry units. The retained slope in several areas were overtopping the walls causing security fences to act as debris barriers, and this additional loading was causing several wall sections to fail. Added difficulty for retaining wall replacement included confined construction restrictions such as existing buildings and equipment within close proximity to the existing walls as well as above ground and underground utilities adjacent to the walls. Lastly, steep sloping conditions and limited access to the walls created additional challenges to the retaining wall replacement.

m6 created a preliminary design report which summarized the existing conditions, identified and evaluated alternatives for retaining wall improvement, provided recommendations for the preferred alternatives and provided a rough order of magnitude cost estimate. The recommended design alternative identified in the PDR was taken forward to final design. m6 performed all civil and structural engineering work to prepare PS&E for the project. m6 also provided bid period and construction period engineering support for the project.