Sacramento West Side levee finishes ‘seepage project’

The Sacramento River West Side Levee District (SRWSLD), acting as the California Environmental Quality Act (CEQA) lead agency and project proponent, has reviewed the proposed project described below to determine whether substantial evidence supports a finding that project implementation could have a significant effect on the environment. “Significant effect on the environment” means a substantial, or potentially substantial, adverse change in any of the physical conditions within the area affected by the project, including land use, air, water, minerals, flora, fauna, ambient noise, and objects of historic or aesthetic significance.

Name of Project: Sacramento River West Bank Seepage Mitigation Project, Levee Miles 3.41 to 6.45

Project Location: The proposed project is located along the landside toe of the Sacramento River west levee between levee miles 3.41 and 6.45, approximately 3 miles north of the community of Knights Landing in Yolo County, California. The right (west) bank of the Sacramento River in the project area is a Sacramento River Flood Control Project (SRFCP) levee. The entirety of the project area is on the landside of the levee.

Project Description: SRWSLD is proposing the Sacramento River West Bank Seepage Mitigation Project, Levee Miles 3.41 to 6.45 (proposed project) to construct approximately 3.25 miles of permanent drained seepage berm over several construction seasons along the landside toe of the Sacramento River west levee. The proposed project would be constructed in response to seepage that occurs periodically along the levee toe during high water events in the Sacramento River, as well as to prevent future seepage problems along the levee. The seepage berm would provide additional weight needed at locations where seepage has historically been observed. The additional weight and internal rock drainage layer would help to counteract and contain upward seepage forces from under-seepage during high water events.

If left unaddressed, seepage can lead to erosion of the landside levee toe and possibly levee failure. Drained seepage berms are landside earthen embankment structures that resist accumulated water pressure and safely release seeping water at the landside toe of the berm through an internal rock drainage layer.

The first 1.3 miles of berm would be constructed in 2018, with additional sections being constructed over the next 5-7 years as additional funding becomes available. Berm construction would occur between April 15 and November 1 in any given year, with the actual duration dependent on the length of berm to be constructed in each individual construction year. No known hazardous waste sites exist in the project area.

The Sacramento River West Side Levee District has completed the levee widening of 500 feet of the Sacramento River West Side Levee near Cecil Lake. The work was completed to combat seepage during flood events. The budget for the project is approximately $200,000. The project included constructing ramps up and down the levee, a water side levee toe road and widening the levee by approximately 8 feet. After the construction was completed, the levee top road was re-graveled. The Reclamation District No. 108 crew completed the maintenance on time and within budget. The photographs below show the site before the project and through construction.

Before Construction	Loading Trucks
Building Ramps	Levee Toe Road
Widening the Levee	Widening the Levee Continued

Reclamation District No. 108 has invested heavily into recycling infrastructure over the years. The unique topographic features of the district, mainly being completely surrounded by flood protection levee’s, allows all the irrigation drain water to be captured and can be either pumped back into the river or recycled within the district. The disadvantage of recycling is the accumulation of salts, which is why in normal years much of the water is pumped back into the river. However, in dry years recycling water is a priority and allows the district to fully farm with just a 75% supply. It is estimated that the district can recycle well over 50,000 AF of water in a normal year. In a drought year such as 2014, the amount of recycling can be significantly increased by reducing the water quality standards within the district.

The recycling facilities in RD 108 include:

Riggs Ranch Pumping Plant

Lateral 8 Check Pumping Plant

Lateral 8 Pumping Plant

Sycamore Slough Pumping Plant

Distribution canals in the Eastern area of the District are concrete lined with low volumes and high velocities, making them difficult to manage with flash board check structures.  Prior to the project, approximately 10 cubic-feet per second of additional flow was required throughout the irrigation season in order to ensurer sufficient flows were delivered to the farm turnout.

Previously, an adjustable flash board structure was located slightly downstream of each farm turnout.  In order to maintain a stable canal water surface elevation, every time the flow in the canal was changed, boards were added or removed.  The benefit to installing Long Crested Weirs in place of adjustable flash board structures is that for cost fluctuations in canal flow rate, the change in water surface elevation at the turnout remains nearly constant.  This provides a constant flow to the irrigated field.  It also substantially reduces labor and the chance of human error.

The same characteristic of the Long Crested Weir that makes it useful in canals for water level control eliminates the weir as a measurement device.  Therefore, the District was required to add measurement methods at key locations throughout the conveyance system.

Reclamation District No. 108 diverts irrigation water from the Sacramento River.  In order to protect the fish populations in the Sacramento River, RD 108 was one of the first irrigation districts to invest and install a fish screen on its primary river diversions.

Wilkins Slough Pumping Plant and Fish Screen

The Wilkins Slough Positive Barrier Fish Screen culminates nearly 8 years of planning, agency coordination, testing alternative barriers, feasibility study, design and construction.  The Wilkins Slough Positive Barrier Fish Screen was put into operation in March 1999 at the start of the irrigation season.

The objectives of the project were to make the Wilkins Slough Diversion “fish friendly,” minimize the impact of water diversions on winter-run chinook salmon and meet current resource agency criteria for fish protection facilities.  A critical goal that was successfully met was to construct the fish screen structure without interrupting irrigation water deliveries or interfering with fish migrations in the Sacramento River.

Wilkins Slough Positive Barrier Fish Screen is one of the largest fish screening facilities in the Sacramento River Basin.  The facility has a design flow capacity of 700 cubic feet per second but can accommodate flows up to 830 cubic feet per second.  The structure is positioned along the right bank of the Sacramento River in front of the Wilkins Slough forebay.  The screens are continuously cleaned by a single-arm mechanical brush mechanism that sweeps across the entire screen surface every 5 minutes.

Emery Poundstone Pumping Plant

Reclamation District No. 108 consolidated three of its river diversion pumping plants into a single facility with a state-of-the-art fish screen.  The initial project investigation confirmed that it would be less costly to build a new combined pumping plant with a fish screen than to install separate fish screens on each of the three existing pumping plants.  Further, it was determined that combining the three pumping plants would result in a lower water diversion requirement, thereby lessening the effects on protected fish species.