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4.0 MG Forbes Hill Reservoir Cover Replacement Study/Preliminary Design Report, Corte Madera, California

Forbes Hill is a 120-year-old concrete reservoir and due to age, rain, ultraviolet rays from the sun, and other factors, the roof needed replacement. As prime consultant, Beyaz & Patel prepared a Preliminary Design Report (PDR) for the Forbes Reservoir Cover Replacement Project. The PDR describes an independently supported clear-span roof and multi-span roof structures that minimize roof height and visibility, evaluates the potential to support a solar photo-voltaic system, project cost estimates, project constructability, and project schedules.

The purpose of the PDR was to explore the possibility of replacing an existing floating cover roof with an independently self-supporting clear-span or multi-span roof. Both steel and aluminum roof systems were considered. The report identified and studied alternate roof types, evaluated those alternatives, including their cost, and made a recommendation of the roof type for detailed design. The roof alternates included: (1) Steel Multi-Span Concept, (2) Aluminum Multi-Span Concept, (3) Steel Clear-Span Concept, and (4) Aluminum Clear-Span Concept. Based on our evaluation, the Aluminum Multi-Span Concept was selected because it provided corrosion resistance, was almost maintenance free, and was the most cost-effective long-term solution. This alternative also provided the lowest life cycle cost and a low-profile roof-line. The project also included the preparation of contract plans and specifications for the removal of the existing floating cover and liner, design of a new multi-span aluminum roof, design of a new CSPE geomembrane liner system and solar PV system, repair to the damaged reservoir floor, and site/civil design.