Clean Water Program

Flow is an important parameter in the measurement of selenium, boron and salt loads in the Grassland Basin. Loads are calculated by multiplying the concentration of the contaminant of concern (expressed in ppb or ppm) by the flow (in cubic feet/second) and then multiplying by an appropriate constant to convert the mass flux into lbs or tons, depending on the constituent. In previous monitoring programs, flow has been the most inconsistently monitored parameter. Flows within the Basin can fluctuate quite widely and are especially susceptible to rainfall runoff events.

Data will be reported in several formats, depending on the needs of the data users. Screening-level data (i.e., water quality and toxicity data) will be reported on a monthly basis to provide GBP participants with a timely picture of site conditions. Compliance data and data measuring environmental impact will be reported on a quarterly basis with biological data incorporated in every other quarterly report. The quarterly reports will provide GBP participants with a comprehensive view of site conditions.

The frequency of monitoring proposed in this plan varies depending upon 1. objective, 2. station location and 3. technique. The sampling schedules will be evaluated as the program proceeds to verify that seasonal or event driven changes are being captured, and adjustments to the schedule made as appropriate.

The study area is located in the Grassland Subarea (SJVDP, 1990): the GBP study area is bounded on the east by the San Joaquin River from the Mendota Pool to Crows Landing; the Westlands Water District to the south; Interstate 5 to the west; and approximately the Stanislaus/Merced county line to the north.

The GBP monitoring plan is intended to provide the data necessary to evaluate the degree to which the commitments of the UA, EA, Supplemental EA, FONSI and consensus letter have been accomplished. To this end, flow, water quality, sediment, biota, toxicity and bioaccumulation monitoring have been identified as the tools for assessing the impacts of using a portion of the SLD to convey agricultural drainage water around the North and South Grasslands wetland areas.

The monitoring plan is designed as a coordinated effort among USBR, USFWS, USGS, CVRWQCB, CDFG, and SLD-MWA. The monitoring plan has been designed to incorporate, where possible, the existing monitoring efforts of participating agencies. The monitoring plan is conceived as a working document which will be modified periodically, based on a review of the data relative to the project objectives and commitments. Should certain monitoring efforts appear to add little to the understanding of conditions resulting from this project, they may be reduced or eliminated.

The distinction between compliance monitoring needs for the GBP, and research/investigation needs to improve selenium and drainage management, has been and will likely continue to be blurred. The compliance monitoring plan is designed to measure whether the GBP meets the commitments made in the UA, EA/FONSI, and consensus letter to the CVRWQCB and to improve, where possible through the monitoring program, the current scientific understanding of selenium fate and transport.

The plan provides for the collection of data that will monitor the selenium load from the GBP that is delivered to the San Joaquin River. The selenium load targets that must be achieved in the compliance program for the next five years are presented in Section 1.0, Table 1.1.