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Notification #1600-2018-0342-R3 Streambed Alteration Agreement October 28, 2019 Page 8 of 24 Operations and Maintenance Activities Gate Operation The gate will remain open to allow for tidal movement, navigation, and recreation and will be closed only as needed for flood control purposes, testing, inspection, and maintenance. For flood control purposes, the gate will be closed only during high flow and tide events forecasted to exceed the design operating water surface elevation (8.0 feet), events that typically occur between November and April. The gate will be operated as needed during these times to prevent high tides from entering Smith Canal. If a high tide event were anticipated, the gate will be closed at the lowest tide prior to the forecasted high tide. The gate will remain closed until the water level in the San Joaquin River drops down to the water level in Smith Canal, at which point the gate will open. An urban area of approximately 3,430 acres drains into Smith Canal through nine storm drain pump stations. In the event that rainfall occurs while the gate is closed and causes the water level in Smith Canal to be higher than that in the Delta, the pump stations that pump into Smith Canal from the surrounding developed areas will be shut off until the gate is opened. The estimated number of closures between 1983 and 2013 would have ranged from 0 to 19 per year, with no closures occurring in 23 of those years. Based on this information it is assumed that there will be two closures per year on average for flood control purposes. In -general, the gate will not need to be closed at a precise point in the tidal cycle. SJAFCA will develop a gate operation plan. The plan will include procedures for predicting when river stage will be high and when local rain events might be significant. The gate operation plan will consider scenarios of combined high stage on the San Joaquin River and significant local storm runoff. Inspection and Maintenance of Structure and Systems Routine inspection and maintenance of the gate structure and associated equipment will be conducted on an annual basis to ensure that flood risk -reduction will be provided by the operation of the gate structure. Maintenance of the fixed wall structure corrosion protection system will take place every 2 years. Fill material in the fixed wall will be inspected annually, and fill material will be added as required. Water Quality Maintenance Floating debris that has accumulated behind the fixed wall will be regularly removed. The frequency of debris removal will depend on the rate of accumulation, to be determined by regular visual monitoring of the site and collection of information from adjacent residents. Based on the information gathered, SJAFCA will schedule and implement a regular debris removal program, removing debris from the site as frequently as needed to comply with direction in the Water Quality Control Plan for the Sacramento River and San Joaquin River Basins' (Basin Plan) direction that "water shall not contain floating material in amounts that cause nuisance or adversely affect beneficial uses." Water hyacinth (Eichhomia crassipes) will be regularly removed from the areas on the Atherton Cove/Smith Canal side of the fixed wall through development and implementation of a water hyacinth control program to ensure that the cover of water hyacinth in the project