A number of commitments were made by the GBD with respect to water quality in connection with the use of a portion of the SLD referred to as the Grassland Bypass. These commitments were expressed in the consensus letter to the CVRWQCB, the UA, the FONSI and Supplemental EA. These commitments include meeting certain monthly and annual selenium loads, not degrading water quality in the San Joaquin River relative to the no-project condition (including the salinity standard at Vernalis), and metering drainage discharges so that they do not violate applicable state, federal, and local laws and regulations.

There are also a number of assumptions expressed in the aforementioned documents which require monitoring to determine their validity. The assumptions are that with the use of the GBP, concentrations of selenium will remain below 2 ug/L in 93 miles of wetland water supply channels (including Salt Slough); and that the increased frequency of exceeding selenium water quality objectives in Mud Slough (north) (5 ug/L) will be offset by a reduction of violations in Salt Slough.

Specifically, the objectives of water quality monitoring are to evaluate the impacts of the GBP on water quality in the San Joaquin River, Salt Slough and the wetland water supply channels. Additionally, it is the intent of the monitoring program to evaluate compliance with Basin Plan water quality objectives and selenium load limits established in the UA and in the CVRWQCB Basin Plan.