SWS-San Jose Hills 1910205 Replace existing Plant 128-R1 0.5 MG Reservoir with a new above ground 0.5 MG welded steel reservoir

SWS-San Jose Hills 1910205 Replace existing Plant 128-R1 0.5 MG Reservoir with a new above ground 0.5 MG welded steel reservoir

Plant 128 is a critical facility that is the primary source for the Hacienda Heights service area. The 0.5 MG buried concrete reservoir at Plant 128 doesn’t meet current seismic requirements, and has reached the end of its useful life. The reservoir will be replaced with above-ground welded steel reservoirs with the same 0.5 MG capacity. The existing concrete reservoir was built sometime between 1914 and 1925 by the La Grande Source Water Company (La Grande.) It is assumed that the reservoir was first built around the 1920s after La Grande purchased the land in 1913. The age of the reservoir is suspected to be nearly 100 years old. It has a capacity of 500,000 gallons with dimensions of approximately 100 feet x 100 feet x 7.5-feet. The reservoir was first used as an irrigation reservoir for agricultural crops in the City of La Puente. In 1956 a roof was added to the reservoir as its use of it was changed to serve a potable water system. The reservoir roof is supported by steel columns, steel beams, and wood beams. The roof is covered with corrugated steel sheets that are in poor condition. Plant 128 was acquired by Suburban by a Corporation Grant Deed from La Grande in 1973. The risk of earthquake in Southern California is high and damage to the reservoir in such an event is likely. Dive inspections performed by Dive Corr, Inc. and a seismic evaluation performed by Tetra Tech, a third-party structural engineering consulting firm, demonstrated that this reservoir is vulnerable and needs to be replaced. The pump station electrical equipment is in poor condition, unsafe, and does not meet reliability standards because it is not equipped with a backup power supply. The dive inspection pictures were provided to Tetra Tech so they could perform an evaluation of the reservoir. Tetra Tech is a leading provider of specialized consulting engineering and management services, complemented by Engineering Report Page 2 September 30, 2024 technical capabilities encompassing research and development, applied science, engineering, and architectural design, surveying, construction management, and operations and maintenance. Tetra Tech's report noted "the overall condition of the reservoir interior seems to be in poor condition due to cracks and spalling which is expected for a structure of this age with potentially insufficient temperature and shrinkage reinforcement." The report also notes that tree root intrusion along the reservoir walls is detrimental to the structural integrity of the reservoir and can decrease the strength of the reservoir structure. Tetra Tech proceeded to perform a structural integrity analysis in accordance with the accepted structural analysis methodology. The analysis took into consideration three different scenarios. In the first scenario, the structure was analyzed with only static loads during normal operations when the tank is filled with 4-5 feet of water. The second scenario considered the static load when the tank is empty during maintenance. The third scenario considered the seismic loads on the roof structure and the reservoir structure when the water is filled with 4-5 feet of water.

La Puente

Los Angeles

Southern California

Los Angeles