The U.S. Bureau of Reclamation (USBR) signed a Finding of No Significant Impact (FONSI) No. 96-01-MP on November 3, 1995 for use of a 28-mile segment of the San Luis Drain (SLD). This segment, known as the Grassland Bypass, will convey agricultural drainage waters from the Grasslands Subarea to the San Joaquin River via a 6 mile segment of Mud Slough (north). An Environmental Assessment (EA) dated April 1991 was prepared in support of the FONSI. A Supplemental EA dated November 1995 updates the 1991 EA, including a discussion of several changes to the previously proposed project as described in the 1991 EA. These changes include a modification of the point of entry to the SLD and an increase in the length of the SLD to be utilized by the project from 19 to 28 miles. An overall map of the area is presented in Figure 1.1.

A Use Agreement (UA) No. 6-07-20-w1319 was signed on November 3, 1995 between USBR and the San Luis & Delta-Mendota Water Authority (SLD-MWA). The UA allows for the use of 28 miles of the SLD for a two year duration. The UA allows for renewal of this interim use for no more than 3 years, if certain conditions are met.

Specifically, renewal is allowed only if the California Regional Water Quality Control Board, Central Valley Region (CVRWQCB) adopts and implements an approvable Basin Plan Amendment/Implementation Plan and has issued a Waste Discharge Requirement, which must be consistent with the recommendations contained in a letter dated November 3, 1995, signed by USBR, U.S. Fish and Wildlife Service (USFWS), U.S. Environmental Protection Agency (USEPA) and the SLD-MWA. Further, renewal is only allowed if the SLD-MWA agrees to specific load limitations contained in the November 3, 1995 consensus letter, and has developed a long term drainage management strategy and plan of implementation consistent with the Basin Plan Amendment. Finally, renewal will be based on an assessment of whether use of the SLD has been consistent with the requirements of the Basin Plan Amendment and the draining parties' approved long-term drainage management plan.

The UA establishes the parameters within which the use of the SLD is allowed. For example, the UA incorporates by reference the load reduction targets included in the November 3, 1995 consensus letter (Table 1.1). The UA establishes a SLD Incentive Fee system by which monetary incentives will be applied to encourage compliance with these load limitations. Exceedence of the annual load targets in excess of 20% will result in closure of the SLD if no acceptable explanation is provided. The UA also incorporates by reference the environmental commitments contained in the FONSI and includes a provision for termination upon a determination that unacceptable adverse environmental effects occur due to the use of the SLD.

These various changes and refinements of the GBP have made necessary certain revisions to an existing monitoring plan, which was finalized after public review in June, 1993. This revised plan incorporates the various changes, including updates of the monitoring stations and sampling and analytical techniques.

1.1 Description of the Project Area

The project is located in the Grasslands Subarea as defined by the San Joaquin Valley Drainage Program (SJVDP, 1990). The area is a valley floor sub-basin of the San Joaquin River Basin. The Grasslands Subarea is an area of approximately 370,000 acres and is generally bounded on the north by the alluvial fan of Orestimba Creek and by the Westlands Subarea to the south. The San Joaquin River forms the eastern boundary and Interstate Highway 5 forms the approximate western boundary. The San Joaquin River forms a wide flood plain in the region. Approximately 90,000 agricultural acres within the Grasslands Subarea have historically discharged subsurface drainage water through the Grassland Water District channels and ultimately to the San Joaquin River. It is these discharges which are the focus of the Grassland Bypass Project and this Monitoring Plan.

The Grasslands Subarea is comprised primarily of agricultural lands and federal, state and private wetlands. The area is a highly managed hydrologic system due to the diversion of perennial flows out of the basin. Thus, agricultural irrigation water must be supplied via supply canals, as must the wetland irrigation water required to manage the wetlands. Similarly, drainage water must be managed in the absence of perennial receiving water flows and the accompanying assimilative, or dilution, capacity.

1.2 Background on Selenium

The Grasslands soils are derived largely from the erosion of the marine rocks that form the California Coast Ranges. They contain abundant salt and other trace elements such as arsenic, boron, selenium and molybdenum. Depth to water can be quite shallow, often inundating the root zone of agricultural fields.

The SLD is located in the west side of the San Joaquin Valley. Authorized by Congress in 1960, an 188-mile concrete drain was to connect the San Francisco Bay Delta to the west side of the valley for the purpose of conveying agricultural drainage water for disposal outside of the basin. The drainage water was to come primarily from tile drains which were installed in fields to remove elevated salts and shallow groundwater from production areas.

Approximately 85 miles of the SLD was completed when construction was halted in 1975. Drain water was conveyed from Westlands Water District south of the Grasslands Subarea through the completed section of the SLD to its terminus at Kesterson Reservoir between 1978 and 1986. Tile drain discharges from the alluvial fan lands on the west side were discovered to contain elevated levels of selenium and boron in addition to having high salinity. Selenium is a highly bioaccumulative trace element which, under certain conditions, can be mobilized through the food chain and cause both acute and chronic toxicity to fish and wildlife. Conditions at Kesterson were such that selenium in the Drain water bioaccumulated causing, most notably, deaths, and deformity in birds. With the closure of the SLD, the Westlands Water District does not export drainage water outside district boundaries.

1.3 Water Distribution: Agricultural Drainage and Wetlands

Historically, no other drainage districts in the area have used the SLD for the conveyance of drainage water. The Grassland Basin Drainers (GBD) discharge drainage water through a more circuitous route, utilizing the wetland water supply channels, Salt Slough and Mud Slough, for disposal of the drainage water to the San Joaquin River upstream of its confluence with the Merced River. Agricultural return flows, including GBP drainage water, dominates the flow in the San Joaquin upstream of the Merced for most months of the year.

Since 1985, when wetlands ceased to use water with selenium concentrations greater than 2ppb, wetland managers have used a complicated "flip-flop" system to alternately transport agricultural drainage and wetland supply water through the Grasslands conveyance system. This system requires a high level of coordinated water management and requires that channels be flushed of selenium contaminated drainage water before being returned to conveying wetland supply water. This results in inefficient water use, and the potential for contaminating wetland water supplies with drainage water during this "flip-flop" operation. In addition, scheduling restrictions inherent in this system restrict, and sometimes prevent, wetland managers from utilizing otherwise available water supplies to optimize habitat and wildlife benefit. The passage of the Central Valley Project Improvement Act (CVPIA) has recently required that an increased volume of fresh water be allocated to wetlands. These increased allocations have made the development of a program which allows for the more efficient supply of freshwater to the managed wetlands all the more crucial.

1.4 Grassland Bypass Project (GBP)

Agricultural subsurface (tile) drainage water from irrigated lands currently enters the Grassland Water District (GWD) from the south, where it is mixed with variable quantities of surface return flows (tailwater) from the Central California Irrigation District (CCID) and the other riparian diverters.  The commingled water flows northward through the GWD in ditches and canals leading to Mud and Salt Sloughs and eventually to the San Joaquin River.  The proposed GBP would intercept this drainage water at a point between Dos Palos and Russell Avenue, south of the GWD, and convey it through the existing SLD for discharge into Mud Slough (north). This system would allow agricultural drainage flows to bypass the GWD altogether.

The GBP is expected to remove contaminated agricultural drainage from approximately 90 miles of wetland water supply channels, but will introduce all of the drainage waters into 6 miles of Mud Slough (north).

Approval of the GBP was granted with the understanding that certain benefits and risks are associated with the Project. The anticipated benefits are as follows:

1. Agricultural drainage water will be removed from the GWD water delivery channels, thus allowing refuge managers to receive and apply all of their fresh water allocations according to optimum habitat management schedules.
2. Removal of agricultural drainage water from the GWD channels will reduce the selenium exposures to fish, wildlife, and humans in the wetland channels and Salt Slough. Concentrations of salinity and other constituents may also be reduced within the wetland channels and Salt Slough.
3. Combining agricultural drainage flows within a single concrete-lined structure, the SLD, will allow better measurement, potentially leading to a more detailed evaluation and effective control of selenium and agricultural drainage.
4. The establishment of an accountable drainage entity will provide the framework necessary for responsible watershed management in the Grassland Basin.