Water Monitoring   Background Water Quality Objectives and Criteria Aquatic Bioassay References

Background

This chapter presents a graphical and narrative summary of the Regional Monitoring Program (RMP) water monitoring results for 1997. This chapter also includes articles contributed by RMP investigators that provide interpretive summaries of specific water monitoring activities.

Water quality was monitored at twenty-two RMP Base Program stations. Parameters measured included conventional water quality parameters (salinity, temperature, total suspended solids, and others; Figures 3.1­3.3), trace elements, trace organic contaminants, and toxicity. Water was also sampled at two stations in the southern end of the Estuary in cooperation with the cities of San Jose (station C-3-0) and Sunnyvale (station C-1-3). In addition, the U.S. Geological Survey monitored water quality at shorter time scales to complement RMP monitoring activities.

Station locations are shown on the inside of the front cover. Water samples were collected in January, April, and August. Sampling dates and parameters measured at each station are shown in Table 1.2 in Chapter One: Introduction. For trace elements, dissolved (0.45 µm filtered) and total (arsenic, chromium, mercury, and selenium) or near-total (cadmium, copper, lead, nickel, silver, and zinc) concentrations are presented in Figures 3.4­3.23. Dissolved (1 µm filtered) and total concentrations of trace organic contaminants are also presented in Figures 3.24­3.39. In addition, long-term trends in trace element and trace organics for each Estuary reach are provided in Figures 3.41 and 3.42. Data for silver were not available. Detailed methods of collection and analysis are included in Appendix A.

In order to compare water monitoring results among the major reaches of the Estuary, the RMP stations are separated into five groups based on similarities in geography, water chemistry, and hydrodynamics: the Southern Sloughs (C-1-3 and C-3-0), South Bay (seven stations, BA10 through BB70), Central Bay (five stations, BC10 through BC60), Northern Estuary (eight stations, BD15 through BF40), and the Rivers (BG20 and BG30).

Water Quality Objectives and Criteria

In this report, comparisons to water quality objectives and criteria are made to provide a context for evaluating the condition of the Estuary in terms of contamination, and not for any regulatory purpose. Water quality objectives and criteria used for these comparisons (Tables 3.7) were selected based on guidance from the San Francisco Bay Regional Water Quality Control Board (SFBRWQCB; Kim Taylor, personal communication). Most of the criteria used were taken from the U.S. Environmental Protection Agency's proposed California Toxics Rule (U.S. EPA, 1997; CTR). U.S. EPA is scheduled to issue a final rule formalizing these California Toxics Rule criteria in the near future. Objectives for total (dissolved + particulate) trace elements were obtained from the San Francisco Bay Basin Plan (SFBRWQCB, 1995). Selenium criteria are region-specific criteria for total recoverable selenium that apply to the entire Estuary (National Toxics Rule, U.S. EPA, 1995). A criterion for diazinon was not included in the proposed CTR, but a guideline developed by the California Department of Fish and Game (Menconi and Cox, 1994) is used in this report to evaluate the degree of contamination in the Estuary.

Different objectives and criteria apply to saltwater, estuarine, and freshwater portions of the Estuary. As defined by the Basin Plan (SFBRWQCB, 1995), estuary locations are 1)freshwater when their salinity is below 5 parts per thousand (ppt) more than 75% of the time; 2)saltwater when their salinity is greater than 5 ppt more than 75% of the time; and 3) estuarine if salinity is intermediate, if estuarine organisms are present for significant periods, or based on an evaluation by the SFBRWQCB (1995).

For estuarine locations, the Basin Plan specifies that the lower of the freshwater and saltwater objectives apply. For this report, RMP stations were classified as freshwater, estuarine, or saltwater based on an evaluation by the SFBRWQCB (Kim Taylor, personal communication) of long-term data at RMP stations, and the characteristic benthic assemblages observed in the RMP Benthic Pilot Study (Lowe and Thompson, in Chapter 4 of this report). The following stations are classified as estuarine in this report: Sunnyvale (C-1-3), San Jose (C-3-0), South Bay (BA20), Petaluma River (BD15), San Pablo Bay (BD20), Pinole Point (BD30), Davis Point (BD40), Napa River (BD50), Pacheco Creek (BF10), Grizzly Bay (BF20), Honker Bay (BF40), Sacramento River (BG20), and San Joaquin River (BG30).

For some contaminants multiple criteria exist that apply to different target organisms (aquatic life or humans) or different lengths or routes of exposure (e.g., 1 hour or 4 days). For this report, RMP contaminant data are compared to the lowest criterion for each contaminant. In general, trace element concentrations were compared to 4-day average criteria for aquatic life, which are lower than the 1-hour average criteria. This is considered appropriate by the SFBRWQCB (Kim Taylor, personal communication) since RMP data are probably indicative of conditions that persist longer than one day. Trace organic contaminant concentrations were compared to human health criteria based on consumption of organisms only, since RMP stations are all seaward of drinking water intakes in the Delta.

Water quality guidelines for six trace elements measured at freshwater stations are related to water hardness. In the RMP, hardness data are only collected at stations where the salinity is less than 5. For these trace elements, freshwater guidelines at estuarine stations where hardness data were not collected were calculated assuming a hardness of 100 mg/L.

Aquatic Bioassays

Laboratory bioassays using Estuary water were conducted at ten RMP stations (Figure 3.40) during the wet-season sampling (January­February) and again in the dry-season sampling (July­August). Two laboratory bioassays were conducted. Mysids (Mysidopsis bahia) were exposed to Estuary water for seven days where percent survival was the endpoint. Larval mussels (Mytilus sp.) were exposed to Estuary water for 48 hours where percent normal development was the endpoint. Detailed methods are included in Appendix A. Significant toxicity was determined by statistical comparison (t-tests) of field samples with controls.

References

Menconi, M. and C. Cox. 1994. Hazard assessment of the insecticide diazinon to aquatic organisms in the Sacramento-San Joaquin river system. Administrative Report 94-2, California Department of Fish and Game, Rancho Cordova, CA.

SFBRWQCB. 1995. 1995 Basin Plan. San Francisco Bay Regional Water Quality Control Board. Oakland, CA.

U.S. EPA. 1995. Water Quality Standards; Establishment of Numeric Criteria for Priority Toxic Pollutants; States' Compliance Final Rule. Federal Register Vol. 62, No. 150, Dec. 22, 1992.

U.S. EPA. 1997. Water Quality Standards; Establishment of Numeric Criteria for Priority Toxic Pollutants for the State of California; Proposed Rule. Federal Register Vol. 62, No. 150, August 5, 1997.