Rock Slough Water Quality Monitoring Instrumentation Improvements Project

This Project consists of the installation of upgraded water quality monitoring equipment at CCWD’s Rock Slough intake in the Sacramento-San Joquin Delta. Currently, water samples at this intake is pumped out of a wet well that pass through two-inch diameter piping, which is at high risk of being blocked by the spread of invasive golden mussels (Limnoperna fortunei). The purpose of this project is to install new water quality monitoring equipment that will provide more reliable monitoring data and will decrease the risk of being blocked by golden mussels. One multiparameter sonde will be installed behind the Rock Slough Fish Screen (RSFS). The sonde will be incased in a six-inch diameter HDPE pipe stilling well and mounted off of the existing sheet pile embedment and railing close to the equipment building, within the afterbay behind the fish screen, where they will extend into the water to collect water quality data. This larger diameter stilling wells will significantly decrease the risk of clogging due to golden mussels and will be easier to access and maintain. See Figure 1 for a Project vicinity map and Figure 2 for a Project location map. Data from the sonde will be transmitted back to the electrical building at the site through new and existing conduits. The Project is expected to take four months, with construction occurring between August and November 2026. Equipment laydown and vehicle staging will occur in previously disturbed areas, within the boundaries of the Rock Slough property. The following types of equipment are expected to be present at the project site: crew trucks, a boat or barge, and power tools. Project activities will occur in previously developed and disturbed areas on CCWD property. No vegetation removal or tree removal will occur. No ground disturbance will occur, and there will be no impact to the bank or bed of the river at the intake. Equipment installation will occur from land via the paved area around the equipment building and from a boat or barge in the water immediately below the platform. The Project is not anticipated to adversely affect natural resources or areas of known cultural or historic resources. CCWD will use the following standard CCWD Best Management Practices (BMPs) to protect the environment: 1. Trash - All trash will be properly contained, removed from the work site, and disposed of on a daily basis. 2. Construction Materials - CCWD will ensure that all raw construction materials, wastes, temporary fences, barriers, and/or flagging are removed and properly disposed of from the Project area immediately following the completion of construction. 3. Hazardous Materials - The storage and handling of hazardous materials within the Project site is prohibited and any unused or leftover hazardous products shall be properly contained and disposed of off-site. 4. Nesting Bird Survey and Buffers - Prior to the start of work, nesting bird surveys will be conducted at the project site by a qualified biologist. If any active nests are discovered before or during construction, the biologist will establish a work area buffer around the nest and monitor the nest for signs of disturbance. 5. Pre-Construction Biological Education Program - A qualified biologist will provide a worker environmental education program to all personnel working at the site prior to the start of construction.