Clean Water Program

Current plans require monthly sampling and toxicity testing at the selected sites. However, should data over several months show little variability, testing frequency will be reduced. The information required to make such a decision will be based on specific species response to the SLD water and comparison between sites. The initial monthly sampling schedule should allow for a determination of the toxicity of SLD and its potential toxicity to Mud and Salt Sloughs.

Grab samples will be collected at the following sites for use in laboratory bioassays:

Site B - SLD at new bridge

Site C - Mud Slough upstream of SLD discharge

Site D - Mud Slough downstream of SLD discharge

Site F - Salt Slough at Highway 165

Control - Delta-Mendota Canal

Rationale for the selection of these sites have been previously described.

The purpose of the toxicity testing program is to evaluate potential toxicity of agriculture drain water as it is conveyed through the SLD to Mud Slough and removed from Salt Slough. The toxicity testing program includes a combination of laboratory methods using standard protocols and field methods. At the same time, water samples will be collected for selenium and sulfate analysis. In addition, at the end of the test, control and exposed algae will be analyzed for selenium bioaccumulation.

The objective of the laboratory toxicity testing program is to evaluate the potential toxicity of the SLD discharge and the receiving water after discharge, using standardized bioassay protocols conducted under controlled environmental conditions.

Fish communities assessment will be used to improve the resolution of whether or not impairment or enhancement of the aquatic community is occurring.

To ensure fish survey data is representative of the fish assemblage within the pre-project area, it will be necessary to examine historical databases. Data comparability will be maintained by using similar collection methods and sampling effort at sites having similar depth and flow regimes. Precision, accuracy, and completeness will be evaluated along with sampling methods and site size.

Fish assemblage information will be qualified by using the 8 integrated metrics defined by the Index of Biotic Integrity (IBI) developed for the Sacramento-San Joaquin Drainage. The metrics developed for this region are based on two premises: 1. native fish species predominate in undisturbed habitats, and 2. salmonids are generally associated with high quality water and habitat (Moyle et al. 1986).

Fish collection techniques employed will depend on stream size and whether or not the stream is wadable. Stream sample reach length will be determined by stream size and subsequent reach length needed to obtain a representative fish assemblage. Fish will be collected using both standard electrofishing and seining techniques. Regardless of capture techniques utilized, all fish will be pooled together to sort afterwards by species and age class (juvenile or adult).

Sampling will be conducted a minimum of twice annually during the summer (June, August). Collecting fish community samples during the summer months is important, as a primary constraint of the Index of Biotic Integrity (IBI) developed for the Sacramento-San Joaquin Drainage (Moyle et al. 1986) is that it be applied to summer fish populations.