Sentinel Butte Mutual Water Company (SBMWC) Flood Capture Basin Project

Sentinel Butte Mutual Water Company (SBMWC) Flood Capture Basin Project

Project Background and Purpose Sentinel Butte Mutual Water Company (SBMWC) has received funding through the Department of Water Resources (DWR) to construct a multi-cell flood capture basin (Project). The funding will allow the SBMWC to construct several basin cells that would allow for approximately 80-acre-feet of storage. This Project would increase the flood water capture/storage capacity for the City of Woodlake which in recent years has suffered heavy damages, the storm season of Winter 2023 being a prime example. Flood hazards in the area are further exacerbated by the lack of a Flood Control District in Woodlake, making this type of Project vital for the city and surrounding area. Project Description The Project is located in Woodlake, Tulare County. The Project would entail constructing a new multi-cell flood water capture basin on an approximate 27-acre site and connecting to existing infrastructure. The proposed basin Project would capture high flows during flood periods primarily from the Kaweah River through the Wutchumna Ditch. The Project would consist of the construction of a cells excavated to an approximate depth of 6’ below existing grade, and the basins would have the capacity to store approximately 50 acre-feet (AF) of water. The Project will also include a new turnout structure within Wutchumna Ditch to divert water into the proposed basin cells. The turnout structure will connect to a basin inlet structure through 120 LF of piping, equipped with a metered connection and rip rap. The turnout structure will be located northwest of the proposed basin cells along the south bank of the existing ditch. Three interbasin connection structures will also be constructed to connect the proposed cells, each connection will be equipped with two structures, rip rap and approximately 50 LF of piping. A basin outlet connection will also be incorporated through the construction of a basin outlet structure, equipped with approximately 45 LF of piping and rip rap. The basin outlet pipeline will terminate at an existing control box operated by SBMWC. In the future when water is available, SBMWC will set a temporary sump pump in the outlet pipeline to pump into the existing standpipe for delivering the flood water to their existing system.. Construction activities will include excavating to an approximate depth of 6’ below existing grade with a basin cut of approximately 90,000 cubic yards. The Project will also include three stockpile locations to store excess dirt on site. Over time, the basin footprint may grow as additional dirt is removed from the stockpiles on site and that area could be utilized for additional storage volume. Once initial excavation is completed the basins will be graded and constructed as per design specifications. Through these improvements the project is anticipated to capture 30 AF/y of flood waters. This estimate assumes that the basin cells developed will provide 50 AF of volume. During wet years it is assumed the cells will completely fill and empty approximately three (3) times providing for 150 AF in those years. Estimating two (2) wet years in 10 years, the average annual is 30 AF/y. Construction Schedule Construction activity for the Project is anticipated to be completed over approximately 4-6 months, beginning in Fall of 2024 (estimated December) and ending by May of 2025. The Project includes mobilization, site preparation, earthwork and structures placement; turnout structures, interbasin and basin outlet structures. After construction completion, performance testing and demobilization would occur. Equipment Construction equipment will likely include the following equipment used during construction: • Excavators, • Backhoes, • Graders, • Skid steers, • Loaders, • Hauling trucks, • Scrapers, • D9 dozer, • Large tractor and large discing unit, • Water trucks supplying water for dust control and conditioning soil for compaction, and • Large watercannon and hoses. Post-construction activities will include system testing, commissioning, and site clean-up. Construction will require temporary staging and storage of materials and equipment. Staging areas will be located onsite. Operation and Maintenance Operation and maintenance of the stormwater capture basin will be performed by SBMWC existing maintenance staff.

Woodlake

Tulare

Southern California

Tulare