Potentially Significant Impact
Would the Project: i)
Expose people or structures to a significant risk of loss, injury or death involving flooding, including flooding as a result of the failure of a levee or dam?
j)
Inundation by seiche, tsunami, or mudflow?
Less Than Significant with Mitigation Incorporated
Less Than Significant Impact
No Impact
SETTING Regional Hydrology The region is an alluvial plain that dips gently to the west from the Sierra Nevada Mountains toward the San Joaquin River channel. Surface water flow is generally to the northwest (Stanislaus County 2012). The main sources of water are the Stanislaus, Tuolumne, and San Joaquin River watersheds, all of which originate in the Sierra Nevada Mountains. The Tuolumne River, located approximately 10miles north of the proposed project area, originates in Yosemite National Park and flows east to west; eventually draining into the San Joaquin River, which flows north to the San Francisco Bay and the Pacific Ocean. TID provides irrigation water to the project area. TID’s canal system begins at La Grange Dam on the Tuolumne River, where water is diverted into TID’s Upper Main Canal for conveyance to Turlock Lake. Turlock Lake acts as a canal-regulating reservoir. From Turlock Lake, water is released into the Main Canal for distribution to downstream growers. TID owns and operates approximately 230 miles of canals and laterals, most of which have been concrete-lined. Water that is not utilized for irrigation purposes flows to the river system (TGBA 2008). Groundwater is often used to supplement irrigation supplies, and is the major source of domestic and industrial water in the vicinity (Stanislaus County 2012). Project Hydrology The proposed project is relatively flat with just a slight slope to aid storm water runoff. Storm water runoff is directed to a French drain consisting of coarse drain rock. Project Water Features The subject site has no water features. Precipitation The proposed project area is characterized by a Mediterranean-type climate with hot, dry summers and cool, wet winters. The majority of precipitation falls between November and March (TGBA 2008). Stanislaus County receives just over 12 inches of rain annually (Stanislaus County 2012). Erosion Potential
Turlock Irrigation District Washington Substation IS/MND
May 2016
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