Fourteen monitoring stations have been established within the study area from which to assess changes in conditions from pre-project conditions (Table 4.1). These stations, labeled A through N, are located within the SLD (A and B), Mud Slough (C, D, E, and I), Salt Slough and the wetland channels (F, J, K, L, and M), and the San Joaquin River (G, H, and N). Figure 4.1 is a schematic showing the general routing of flow through the project area and the relative locations of the sampling stations.

Stations in the SLD are located at the drain inlet (A) and drain outlet (B). Data from these stations will be used to assess selenium loads, selenium transport (flux), water quality, sediment quality, tissue concentrations, toxicity and bioaccumulation. Selenium analysis will include both total selenium and dissolved selenium according to CVRWQB protocols. Also, at sites A and B, both total and dissolved selenium will be determined on a weekly basis to aid in addressing questions about selenium fate and the seasonality of selenium partitioning between dissolved and suspended.

Substations have been identified in the SLD to measure sediment volume and chemistry so as to make informed sediment management decisions. These substations have been identified by their locations: 1. between checks 17 and 18; 2. between checks 14 and 15; 3. between checks 10 and 11; and 4. between checks 1 and 2. Estimates of sediment concentration will be made to determine if and when sediments must be removed for disposal.

Stations in Mud Slough are located upstream of the discharge from the SLD (C), downstream of the discharge from the SLD (D), upstream of the confluence with the San Joaquin River (E), and in a seasonal backwater area (I). Data from some or all of these stations will be used to assess selenium loads, selenium transport (flux), water quality, sediment quality, tissue concentrations, toxicity, bioaccumulation, and aquatic community structure. Sampling in Mud Slough is intended to be comprehensive. In particular, it is intended to address the issue of "adverse environmental impact," as described in the UA.

Station F is the only station located in Salt Slough. Data from this station will be used to assess selenium loads, water quality, sediment quality, tissue concentrations, toxicity, bioaccumulation, and aquatic community structure. Since agricultural drainage from the GBP will be eliminated from Salt Slough as a result of the GBP, "upstream" and "downstream" sampling stations were not identified. Data from Salt Slough will be compared to historic data from the site in order to evaluate environmental improvement from removal of agricultural drainage water.

Stations in the wetland channels are located in Camp 13 Canal (J), Agatha Canal (K), San Luis Canal (L), and the Santa Fe Canal (M). Data from these stations will be used to assess selenium concentrations in order to assess and verify removal of agricultural drainage water and suitability of the channels for year round wetland water supply delivery. The connections from the Main Drain to the South Grasslands Agatha and Camp 13 canals are shown severed in Figure 4.1 indicating the rerouting of the combined agricultural drainage flow to the San Luis Drain.

Water quality and flow data from the drain outlet (B), Mud Slough (D), Salt Slough (F), and the San Joaquin River near Crows Landing (N) will be compared to historic flow and water quality data to evaluate and verify that there are no adverse impacts to San Joaquin River water quality due to the project.

Stations in the San Joaquin River are located upstream of the confluence with Mud Slough (G), downstream of the confluence with Mud Slough (H), and downstream of the confluence with the Merced River (N). Data from these stations will be used to assess selenium load, water quality, and tissue concentrations. Selenium loads and water quality have been identified as relevant indicators of change to the San Joaquin River system resulting from GBP. Tissue concentrations will provide confirmation of these parameters as indicators of system health. Sampling in the San Joaquin River is intended to serve as both compliance with CVRWQCB objectives for the river and trend monitoring.