The North Coast County Water District (NCCWD or District) proposes to replace a water tank (Sheila Tank) located off of Sheila Lane in the City of Pacifica. Sheila Tank was built in 1955, has reached the end of its useful life, and currently is out of service. The original Sheila Tank, constructed of redwood, has a volume of about 100,000 gallons, or 0.1 million gallons (MG). According to District records the existing tank is 13-feet high by 32-feet in diameter (these dimensions suggest an actual storage volume of less than 80,000 gallons). The Sheila Tank Replacement Project (proposed project) will include the demolition of the existing tank and the addition of a prestressed concrete replacement tank which will be partially buried and have a capacity of 0.6 MG and feature associated valves, vault, piping, power and other site improvements. See Figure 3 for the Final Grading and Paving Plan; See Appendix A for the full 100% Design Plans Package. The new concrete Sheila Tank would have an inside diameter of 55-feet, an outside diameter of 57-feet, a side water depth of 34-feet, and a 28-foot height above finished grade (Appendix B - Basis of Design Report). Partially burying the tank 5-feet below lowest adjacent grade will not only minimize the visual impact for surrounding neighbors but also reduce costly foundation enhancements in event of seismic activity (Appendix B). The projected design inlet and outlet flows to the tank will be 1,200 gallons per minute (gpm) for peak hour demand and 320 (gpm) for average day demand (Appendix B). The NCCWD is both the project applicant and CEQA Lead Agency.
As mentioned above, Sheila Tank has reached the end of its useful life and currently is out of service. The District has determined that the tank is no longer viable with its current capacity, it holds inadequate fire protection storage, cannot supply peak demands, and is seismically deficient. The existing tank is leaking, not anchored, and vulnerable to seismic events. The proposed project would replace the existing deteriorating tank to meet current standards of public health and safety, and would increase the size of the tank to address a storage deficit and a need for improved fire suppression in the area served by the tank. Discharge water flow rates would remain the same regardless of the increased tank size. The proposed project would not increase the capacity of the water system, as the pipeline connecting to the tank would not be increased. The proposed project would merely increase the storage volume to help meet existing daily demand as well as increase water storage for fire suppression. Sheila Tank currently services an area of approximately 265 acres that includes approximately 1,410 service connections, and also assists an additional zone which contains an additional 760 service connections. The service area and number of residences served would remain unchanged under the proposed project.