Clean Water Program

The Grasslands channels monitoring sites (Sites F and J through M) will be sampled at a weekly frequency. This frequency will be sufficient to characterize water quality conditions to assess changes in water quality at these sites as result of removal of drainage.

The San Joaquin River at Fremont Ford and at Hills Ferry will be sampled on a weekly basis. Weekly samples should adequately characterize temporal variations and provide an adequate assessment of the changes in water quality in the San Joaquin River as a result of continued discharge of drainage (Hills Ferry) and from the removal of drainage (Fremont Ford).

A daily composite sample will be collected at Crows Landing. This frequency is necessary for evaluation of compliance with water quality objectives. A weekly grab sample will also be collected for quality control purposes.

Weekly samples will be collected at Sites A and B for selected parameters. A sample will be collected on a daily basis for total selenium at Site B (outflow of the SLD) using a 24 bottle, integrating automatic sampler. Daily monitoring of selenium loads discharged is required for compliance evaluation. In addition, weekly depth-width integrated samples will be taken from the footbridges at Sites A and B for analysis of dissolved and suspended selenium concentrations in the drainage water.

Five monitoring sites have been selected in the Grasslands wetland channels. These sites include Site F (Salt Slough), Site J (Camp 13 ditch), Site K (Agatha Canal), Site L (San Luis Canal), and Site M (Santa Fe Canal). These sites are presently receiving agricultural sub-surface drainage, but will cease receiving drainage as a result of the GBP.

Three water quality monitoring sites have been selected on the San Joaquin River. Site G (San Joaquin River at Fremont Ford) is located downstream of Salt Slough and upstream of the Mud Slough (north) confluence. This site is presently impacted by agricultural subsurface drainage. With the use of the Grassland Bypass, drainage will be discharged to the San Joaquin River downstream of this site. Monitoring at this site will allow the assessment of the assumptions made regarding water quality benefits as a result of the use of the Grassland Bypass.

Four water quality monitoring sites have been selected on Mud Slough (north). Water quality data gathered at Mud Slough (north) will provide information regarding the impacts of the GBP on the Slough. Data will also be used to assess compliance with the CVRWQCB interim water quality goals and water quality objectives.

Two sampling locations in the SLD have been identified for monitoring. Site A will be used to monitor the inflow of drainage to the SLD. Drainage is presently dispersed through multiple wetland channels. Combining drainage flows into one channel, as a result of use of the GBP, will provide a better accounting of the quantity and quality of the drainage.

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.

The California Regional Water Quality Control Board, Central Valley Region (CVRWQCB) has been conducting water quality monitoring of the lower San Joaquin River and the wetland channels and principal sloughs within the Grassland Basin since 1985. The data gathered has been used in developing regulatory programs for the control of agricultural subsurface drainage discharges to surface waters.

The frequency at which flow is measured depends on the nature of the site, whether a control structure is present, the equipment available to measure and record flow measurements, and the budget allocated for flow measurement at each monitoring location. Where measurements are taken manually, daily or weekly measurements of flow using a staff gauge are most common. If a Stevens stage recorder is available at the site, it is possible to take hourly measurements. However, the chart from the Stevens recorder must be removed and read to determine stage.