Reclamation District 1500 Flood Control and Flood Safety Rehabilitation Project

The Project would rehabilitate and modernize the existing Karnak Drainage Facility to continue to provide flood protection for the Sutter Basin similar to current operations. The Project’s Area of Potential Effects is approximately 7.6 acres in size. The existing Karnak Drainage Facility discharges water from the Sutter Basin into the Sacramento Slough and consists of three antiquated pump stations that have been well maintained but much of the equipment is nearing the end of its useful life. Pumping Plant 1 (PP1) on the north bank of the drainage canal was constructed in 1914 and provides the ability to discharge 1,200 ± cubic feet per second (cfs) of drain water out of the Sutter Basin utilizing six centrifugal pumps during above normal winters and large storm events. Pumping Plant 2 (PP2) was constructed in 1929 and has never operated correctly and is not utilized. PP3 is located adjacent to PP2 and has been in operation since 1952 and is used in day-to-day operations to remove excess precipitation in the winter months and seepage water during the entire year, utilizing four vertical pumps with a capacity of 700 ± cfs. These pumping plants have no automatic controls or a backup power system. All three pumping plants have concrete pump houses and have existing culverts through the flood control levee that discharge the water into the Sacramento Slough. The Project would overhaul and modernize the existing drainage and flood protection facility to increase reliability and efficiency, leveraging to the extent possible, the existing facilities that RD 1500 already owns. The Project would also result in the installation of a backup power source and increased pumping capacity to provide redundancy and provide for anticipated climate change impacts. Project design would result in maintaining the PP1 building and discharge culverts but modernizing the pumping equipment and electrical system; removing the existing PP2 building and equipment; constructing a gravity outlet structure with fish barrier that utilizes the existing PP2 culverts for gravity drainage; and the removal of the existing Pumping Plant 3 (PP3) building and equipment and constructing a slightly larger, new Pumping Plant 4 (PP4) with submersible pumps that utilizes the existing PP3 discharge culverts. Electrical equipment would be located above the base flood elevation. Fill would be added onto a portion of the outer levee slope to make an equipment pad to facilitate installation of an engine generator set above the base flood elevation to serve as a backup power source. The Project would provide a long-term flood management solution by efficiently and reliably continuing current operations. An inflatable bladder cofferdam, or comparable watertight barrier, will be used temporarily during construction to isolate the discharge culvert outlets in the Sacramento Slough to prevent water from obstructing the installation of protective liners and flowmeters in the discharge culverts and installation of new flap gates on the existing culvert outlets. Construction activities in the Sacramento Slough would occur when the water level is at its lowest stage, likely in the summer and fall months. In developing the Project design, a preliminary structural evaluation of the existing Karnak Drainage Facility pump station buildings was conducted by a licensed California structural engineer to determine their suitability for continued use. Initial Structural Evaluation reports for all three of the existing buildings at the Karnak site are contained in the Watershed Plan-EIS, with the findings summarized below: • The PP1 pump house building (PH1) is impressively sized and reinforced, and it appears the building has performed well and is currently performing in general conformance to the original intent of the design. However, there exist some issues that are recommended for further evaluation to determine if remedial efforts are needed and/or if structural strengthening would be beneficial for further long-term use of the structure. • While not currently being used, the PP2 pump house building (PH2) has significant geometric characteristics of the structure that cause a high level of concern for the structure to resist moderate to major seismic event forces. • The PP3 pump house building (PH3) appears to be performing in general conformance to the original intent of the design, however, similar to the PH2 building, the structure has significant geometric characteristics that cause a high level of concern for the structure to resist moderate to major seismic event forces. It is anticipated at this time that Pacific Gas & Electric Company (PG&E), the local electrical utility, will want to discontinue providing the existing 2300V electrical service to the facility once the modernization has been complete, and that PG&E will want to bring in 4160V or higher voltage to serve the site in the future, although this assumption needs to be verified with PG&E during the final design process. The Project design can accommodate the upgraded PG&E service by installing District owned transformers to step the voltage down to 480V to power the new submersible pumps at the new pump station as well as the rebuilt motors on the existing centrifugal pumps at PP1. The Project has been divided into four Measures that correspond to the major work items. The table below presents the various components of each measure of the Project. Modernization Alternative Project Activities Summary: Measure 1 - Modernize Existing Pumping Plant 1 (PP1) • Installation of permanent sheet piling near PP1 to construct a foundation pad for a new electrical control building and area adjacent to the new gravity outlet structure. • Construction of a new, larger, and slightly higher platform structure near PP1 with the installation of a new air—conditioned electrical control building. • Refurbish the six existing 200 cfs centrifugal pumps. • Rebuild the six existing centrifugal pump 800 Hp motors for 480V service. • Modify the existing centrifugal pump priming system for easier operation. • Replacement of valves and actuators on pump discharges. • Install protective liner and add flow measurement inside all 3 existing discharge culverts. • Replacement of existing flap gates and slide gates on discharge culverts in existing access chamber. • Rehabilitate existing PP1 building by sealing concrete cracks and recoating roof. • Remove all electrical equipment that serves PP1 from the existing platform structure. • Installation of all new electrical equipment, switchgear, and motor controls for PP1. • Installation of step-down transformers adjacent to the control building on the elevated platform to reduce PG&E high-voltage down to 480V to power the pumping equipment. Measure 2 - Utility Upgrade • Construction of an elevated platform for new transformers. • Installation of new PG&E high-voltage electrical transformers. Measure 3 — Construct Gravity Outlet Structure • Relocation of powerlines serving the existing PP3 station (which currently cross the existing PP2 building). • Installation of a temporary cofferdam in the drainage canal to facilitate dewatering the area around the existing PP2 building. • Removal of all equipment and demolition of the existing PP2 building. • Removal of existing concrete stopblocks and sediment lodged in discharge culverts. • Construction of a concrete gravity outlet structure and fish barrier, consisting of: • reorientation of discharge culvert inlets; • slide gates on culvert inlets; • pleated long-crested weir for level control in the drainage canal, outlet measurement, and prevention of juvenile fish from migrating into the drainage canal during gravity flow operations; • fish barrier screen to prevent migration of adult fish into the drainage canal during gravity flow operations; • bypass slide gates in long-crested weir if drainage canal needed to be drained; • installation of a water level sensor; and • maintenance hoist to clean the fish barrier screen. • Installation of protective liner inside all 3 discharge box culverts. • Replacement of flap gates on discharge culvert outlets. Measure 4 – Construct New Pumping Plant 4 (PP4) • Installation of a temporary cofferdam in the drainage canal to facilitate dewatering the area around the existing PP3 building. • Removal of all PP3 equipment and demolition of the existing PP3 building. • Construction of a new concrete PP4 pump structure. • Installation of protective liner and flow measurement inside all four existing PP3 box culverts. • Replacement of slide gates inside access chamber on existing PP3 discharge culverts. • Replacement of flap gates on the existing PP3 discharge box culvert outlets. • Construct pad for backup generator on a portion of the outer levee, with fill material installed on the levee. • Installation of permanent sheet piling between the PP4 pump structure and the gravity discharge structure. • Miscellaneous grading around structures and approach roads. • Installation of six submersible VFD (variable-frequency drive) controlled pumps with a discharge capacity of approximately 1,000± cfs. • Installation of electrical controls inside the air-conditioned control building at PP1. • Installation of a SCADA (Supervisory Control and Data Acquisition) system for automated operation and monitoring of the pump stations. • Installation of backup generator on outer levee to power PP4 in the event PG&E power is lost. Construction of the Project would need to be conducted in phases since drainage service must continue to be provided at the Karnak Facility at all times. Construction would likely need to occur in the following sequence: Year 1 (PP3 operational) • Installation of new elevated platform, control building and electrical system at PP1, keeping power to existing PP3 station • Modernization of pumping equipment at PP1 and rehabilitation of existing PP1 discharge culverts while PP3 is still operational • Installation of new PG&E high-voltage transformers on elevated platform • Demolition of PP2 building, renovation of PP2 discharge culverts for gravity drainage, and construction of gravity outlet structure with fish barrier while PP3 is still operational Year 2 (PP1 and gravity drainage operational) • Demolition of PP3 building, rehabilitation of existing PP3 discharge culverts, and construction of a new PP4 pump station • Installation of backup generator on a portion of the outer levee • Installation of a SCADA system Modernization of the existing facility meets the purpose and need of the Project, provides safety and protection for the community of Robbins and surrounding area, protects farmland and emergency access roads, maintains the local economy, maintains environmental benefits, and is the most logistically reasonable option for maintaining flood protection for the Sutter Basin.