Gates

The structural/physical components of the alternatives include the construction and operation of fish and/or flow control structures (gates) and maintenance activities for gates. Up to three flow control gates, one each at Middle River, Grant Line Canal, and Old River, and one fish control gate at the head of Old River would be constructed and operated as a part of the SDIP. The operation of the three flow control gates would vary over the course of the irrigation season. The fish control gate is intended to prevent migrating and outmigrating salmon from entering Old River from the San Joaquin River, thus minimizing exposure to the SWP and CVP pumping facilities. The flow control structures are intended to assist in maintaining water levels and water quality for south Delta agricultural users.

Gate Construction Methods
There are two potential methods of constructing the gates: (1) using cofferdam construction, which creates a dewatered construction area for ease of access and egress; and (2) in-the-wet construction, which allows the river to flow unimpeded and eliminates the time, material, and cost of constructing a cofferdam. The construction window necessary for in-channel activities would vary for each, as outlined below.

Gate Operations

Gates Operations Committee
A multi-agency committee will be convened to specify the operations of the fish control and flow control gates to minimize impacts of sensitive fish species and to meet water stage and water quality requirements of south Delta water users. The multi-agency committee will include representatives of DWR, Reclamation, USFWS, NOAA Fisheries, DFG, and SDWA and possibly others as needs change. The committee will meet through a conference call, roughly every 2 weeks. DWR will be responsible for providing predictive modeling, and SWP will provide operations forecasts and the conference call line. Reclamation will be responsible for providing CVP operations forecasts, including San Joaquin River flow and current water quality. Other members will provide the committee with the latest information related to south Delta aquatic species and agricultural crop conditions. The committee may defer operations to DWR and Reclamation if all agree there is no need to confer and gates can be operated to protect water quality and stage for south Delta agricultural water users.

Head of Old River Fish Control Gate
The operation (or closing) of the head of Old River gate is intended to benefit the fall-/late fall–run Chinook salmon by reducing the straying of the salmon into the south Delta channels via the Old River. Because the gate is functional, operations can be more flexible in response to the detection of fish presence and/or water quality. Gate operations can provide more net flows from Victoria Canal into Middle River and from Old River at Clifton Court Ferry into the Old River channel upstream of the Tracy Pumping Plant. This will lower the EC of the western portion of these channels. However, the gate that can have the largest effect on south Delta salinity is the head of Old River gate. The salinity in the south Delta channels can be reduced to approach the electrical conductivity (EC) of the SWP exports if the San Joaquin River diversion flow into the head of Old River is reduced.

VAMP/Spring Operations
Operation (closing) of the head of Old River gate is proposed to begin at the start of the VAMP spring pulse flow period, typically April 15, plus or minus a few days. Spring operation is generally expected to continue for 30 days following the start of operation.

Summer and Fall Operations
During the summer and fall months, the gate would be operated to improve flow in the San Joaquin River, thus assisting in avoiding historically present hypoxic conditions in the lower San Joaquin River near Stockton. Gate operations during this period would be at the request of DFG, NOAA Fisheries, and USFWS and would not occur if the San Joaquin River flow at Vernalis is greater than 5,000 cfs. The gate would be operated to allow some flow into Old River to maintain water quality while keeping a majority of the flow in the San Joaquin River.

Maintenance
All four proposed gates would be owned, operated, and maintained by DWR. Periodic maintenance of the control gates would occur every 5 to 10 years. Maintenance of the motors, compressors, and control systems would occur annually and require a service truck. Maintenance dredging around the gate would be necessary to clear out sediment deposits.