Strategy for Protecting Aqueducts in the Sacramento-San Joaquin Delta

The East Bay Municipal Utility District (EBMUD) relies on three (3) large aqueducts, known as the Mokelumne Aqueducts, crossing the Sacramento-San Joaquin Delta (the Delta) to convey over 90% of its water supply from its source in the foothills of the Sierra Nevada Mountains to its 1,300,000 water users on the east side of San Francisco Bay. EBMUD has interconnections with the San Francisco Public Utilities Commission and the Contra Costa Water District, making the aqueducts a linchpin in an increasingly integrated regional water system. The Delta is a large area of interconnected waterways surrounding numerous "islands" that are all below sea level. These "islands" are protected by fragile levees up to 100 years old, many constructed without the benefit of current engineering practices. EBMUD decided to evaluate its levees due to: 1) increased vulnerability to island flooding due to sea level rise; 2) increased flows in adjacent rivers and sloughs resulting from climate changes, 3) island consolidation due to oxidation of the underlying peat soils, and; 4) recently recognized seismicity from newly documented faults. This evaluation was made to better understand the reliability of its aqueducts through the Delta and to develop possible long-term mitigation strategies for the risks identified. The evaluation was done in response to, and concurrently with, the State of California's Delta Vision and Delta Risk Management process (DRMS). The recommendations of the Delta Vision and DRMS process will have a significant part in determining the future of the Delta as a whole and may or may not have a positive effect on the security of EBMUD's water conveyance system.