The Del Puerto Creek Sediment Removal Project is located between Interstate 5 and the Governor Edmond G. Brown California Aqueduct, approximately 4 miles northwest of the city of Patterson, Stanislaus County, California.
Del Puerto Creek, an intermittent creek that historically drains into the San Joaquin River, passes under the California Aqueduct (CAAQ) through a concrete underchute structure approximately 6 miles downstream of the creek. The concrete underchute structure for Del Puerto Creek consists of a 16-foot diameter culvert, wing walls, a head wall, an end wall, and concrete aprons on the inlet and outlet. The inlet apron extends approximately 53 feet from the opening of the culvert, upstream into the creek. Additionally, 278 feet of the channel was engineered and altered as part of the original structure. During high flow events, sediment and gravel are deposited in front and on top of the inlet apron via natural fluvial processes thereby reducing channel capacity and the ability of the underchute to convey natural streamflow past the CAAQ, which in turn threatens the integrity of the CAAQ levee.
In 2015, DWR prepared an ISMND to analyze the potential environmental effects of maintenance activities to Del Puerto Creek to remove the silt/cobble from 200 feet upstream of the underchute’s inlet and returning the drainage to its intended condition at or slightly below the level of the concrete apron. The project included improvements to access roads, sediment removal, access ramp improvements, bank stabilization, and improvements to an adjacent drainage ditch that channels runoff from the CAAQ levee directly into the creek. After the initial sediment removal, DWR intended that biennial maintenance would occur to keep the drainage to its intended condition.
As a result of delays to the planned biennial maintenance, DWR proposes to extend sediment removal and bank stabilization by 278 feet for a total of 478 feet of the channel sediment removal directly adjacent to the inlet apron on the upstream portion of Del Puerto Creek. Sediment removal will include bank stabilization efforts, removal of an invasive tree, and the stabilization of 50 feet of impacted area with clean imported soil and rip-rap. Additionally, a ramp will be repaired and temporarily extended into the channel during the project to allow equipment access into the channel; the rock drainage adjacent to the channel will be repaired as needed; the access road will be improved as needed; and spoils will be disposed nearby.