3.0 Sediment Monitoring

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3.1 Background

Sediments are monitored because they are a fundamental ecosystem component of the Bay, and they play a key role in the adsorption and transport of contaminants. Sediments serve as contaminant sources and sinks, and most contaminants are usually found in concentrations orders of magnitude higher in the upper few centimeters of sediments than in the water column. Information about sediments addresses aspects of all RMP Objectives (listed in the Introduction). In this section, patterns and trends in sediment contamination are described (Objective 1) and compared to several sets of sediment quality guidelines (Objective 4), while sediment bioassays address contaminant effects (Objective 3). Synthesis and interpretation of sediment information (Objective 5), and inferences about sources and loadings (Objective 2) will be addressed in a new RMP Technical Report, Atlas of Sediment Contamination, Toxicity, and Benthic Assemblages in San Francisco Bay.

Information about sediment contamination is used in making decisions related to many important management issues: the identification of sediment "toxic hot spots," currently a priority for the State and Regional Water Quality Control Boards; the clean-up of numerous military bases in the region which requires information about background contaminant levels; and the continuous dredging of the Estuary which requires testing and comparisons to some reference, or background, concentration. The RMP provides information that may be used by others to assess the condition of Estuary sediments. This information is also used in evaluation and redesign efforts for the RMP itself.

The geochemistry of sediments is complex, and in order to interpret contaminant concentrations measured in sediments it is necessary to understand how hydrology (flows) and other non-contaminant sediment properties may affect contaminant concentrations. An overview of Estuary hydrology and water quality was presented in the Introduction. CTD (conductivity, temperature, depth) profiles of the water column were collected at all RMP sediment stations. Those data are not presented in this report, but are available from the San Francisco Estuary Institute upon request. Several sediment quality parameters that may affect sediment contaminant concentrations (grain-size, organic carbon, ammonia, and sulfides) are also monitored, and are listed in the Data Tables.

Sediment contaminant monitoring includes trace elements and trace organic contaminants at 22 RMP Base Program stations. Sediments were also monitored at two stations at the southern end of the Estuary in cooperation with the Regional Board and the cities of San Jose (station C-3-0) and Sunnyvale (station C-1-3). As part of the Estuary Interface Pilot Study, sediments were monitored at two additional stations in the southern end of the Estuary: Standish Dam on Coyote Creek (station BW10) and Alviso Slough on the Guadalupe River (station BW15). For more information on this Pilot Study see RMP Technical Report #19 by Daum and Hoenicke, 1998.

Station locations are shown on Figure 1.1. Sediment samples were collected during the wet season (January-February) and dry season (August). Sampling dates are shown on Table 1.3 in the Introduction. Detailed methods of collection and analysis are included in the Description of Methods. Table 1.2 in the Introduction lists parameters measured in sediment. Sediment quality parameters including station depths, and all contaminant concentrations are tabulated in the Data Tables.

In order to compare sediment monitoring results among the major sub-regions of the Estuary, the RMP stations are separated into seven groups of stations (six base program plus Southern Sloughs) in five Estuary reaches based subjectively on geography, similarities in sediment types, and patterns of trace contaminant concentrations. The Estuary segments are: the Southern Sloughs (C-1-3 and C-3-0), South Bay (seven stations, BA10 through BB70), Central Bay (five stations, BC11 through BC60), Northern Estuary (eight stations, BD15 through BF40), and Rivers (BG20 and BG30). In addition, the Estuary Interface Pilot stations (BW10 and BW15) were included for comparative purposes. Stations with coarse sediments (>60% sand: three stations in the wet season and five in the dry season) generally have considerably lower contaminant concentrations and were identified on Figures 3.1-3.15.

Concentrations of total DDTs are not reported due to matrix interference. Total organic carbon (TOC) concentrations and the majority of % solids data for sediment cruise 16 in August have just been received and are currently being processed.

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3.2 Sediment Quality Guidelines

There are currently no Basin Plan objectives or other regulatory criteria for sediment contaminant concentrations in the Estuary. However, several sets of sediment quality guidelines (Table 3.1) may be used as informal screening tools for sediment contaminant concentrations, but hold no regulatory status.

Sediment quality guidelines developed by Long et al. (1995) are based on data compiled from numerous studies in the United States that included sediment contaminant and biological effects information. The guidelines were developed to identify concentrations of contaminants that were associated with biological effects in laboratory, field, or modeling studies. The effects range-low (ERL) value is the concentration equivalent to the lower 10th percentile of the compiled study data, and the effects range-median (ERM) is the concentration equivalent to the 50th percentile of the compiled study data. Sediment concentrations below the ERL are interpreted as being "rarely" associated with adverse effects. Concentrations between the ERL and ERM are "occasionally" associated with adverse effects, and concentrations above the ERM are "frequently" associated with adverse effects. Effects range values for mercury, nickel, total PCBs, and total DDTs have low levels of confidence associated with them. The effects-range values used for chlordanes and dieldrin are from Long and Morgan (1990). There are no effects-range guidelines for selenium, but the Regional Board has suggested guidelines of 1.4 ppm (Wolfenden and Carlin, 1992), and 1.5 ppm (Taylor et al. 1992).

A set of sediment quality guidelines developed by the Regional Board and introduced in the 1997 RMP Annual Report were also used. Ambient Sediment Concentration (ASC) values are based on samples collected between 1991-1996 from the RMP and the Bay Protection and Toxic Cleanup Program (BPTCP). Samples collected from sites representative of the cleanest portions of the Estuary were used in deriving the "ambient" concentrations. This approach is thought to define contemporary ambient contaminant levels given the fact that virtually no San Francisco Bay sediments in the active layer are free of anthropogenic pollutants. Resulting ambient sediment concentrations are above pre-industrial "background" levels but below "toxic hot spot" levels. ASC values are different for sandy (< 40% fines) and muddy (> 40% fines) sediments. For more information on the ASC guidelines see Gandesbery and Hetzel. (1999) or Smith and Riege (1998). Both the Long et al (1995). and ASC guideline values are shown on the sediment contaminant concentration bar charts for comparative purposes.

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3.3 Sediment Bioassays

Sediment bioassays are conducted to determine the potential for biological effects from exposure to sediment contamination. Two sediment bioassays were conducted at 14 of the RMP stations (Figure 3.16) in February and again in July-August of 1998. Sampling dates are listed in Table 1.3 in the Introduction. Amphipods (Eohaustorius estuarius) were exposed to whole sediment for ten days with percent survival as the endpoint. However, the elutriate test using Strongylocentrotus purpuratus was initiated during the February bioassays after Mytilus broodstock failed to spawn, and are included in the Data Tables. Larval mussels (Mytilus galloprovincialis) were exposed to sediment elutriates (water-soluble fraction) for 48 hours with percent normal development as the endpoint. The control sediment used in the Eohaustorius test was from the site near Newport, Oregon where the amphipods were collected. The control used for the Mytilus (mussel) test was clean seawater from Granite Canyon, California. The Description of Methods contains detailed methods of collection and testing and the QA Tables contains quality assurance information.

When a sample is found to be toxic, it is interpreted as an indication of the potential for biological effects. However, since sediments are mixtures of numerous contaminants, it is difficult to determine which contaminant(s) may have caused any toxicity observed (see 3.5 Discussion).

A sample was considered toxic if:

1. there was a significant difference between the laboratory control and test replicates using a t-test, and
2. the difference between the mean endpoint value in the control and the mean endpoint value in the test sample was greater than the 90^th percentile minimum significant difference (MSD).

The MSD is a statistic that indicates the difference between the two means that will be considered statistically significant given the observed level of between-replicate variation and the alpha level chosen for the comparison. The 90^th percentile MSD value is the difference that 90% of the t-tests will be able to detect as statistically significant. Use of the 90^th percentile MSD is similar to establishing statistical power at a level of 0.90, and is a way to insure that statistical significance is determined based on large differences between means, rather than small variation among replicates. MSDs were established by analysis of numerous bioassay results for San Francisco Bay (Anderson and Hunt, unpubl.; Hunt et al. 1996). Based on those analyses, the 90^th percentile MSD for Eohaustorius was 18.8% and for the bivalve larvae test 21%. For the 1998 sediment bioassays, an amphipod bioassay was toxic if it had below 78.2% survival in February and 79.2% July-August respectively. A larval bivalve bioassay was toxic it if had below 63% or 81% normal development in February or July-August, respectively.

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3.4 Sediment Trends

Sediment contaminant concentrations have been measured at most of the RMP sites since 1991. Samples were collected by the State’s Bay Protection and Toxic Clean-up Program (BPTCP) in 1991 and 1992, and by the RMP since 1993. Combining data from these two programs provides a time-series of 14 sampling periods over 8 years. Average and ranges of concentrations for several trace elements are shown for each major Estuary reach (Figures 3.18-3.27). Arsenic, cadmium, and mercury are not included for 1991 and 1992 due to quality control problems in the analyses.

Except for the Rivers, plots for the various Estuary segments represent only muddy sediments (<60% sand). At the River stations, one or both stations had coarse sediments in each sampling period. A separate plot is presented for stations with coarse (>60% sand) sediments that also includes the Rivers when sandy. Contaminant concentrations were generally lower in the coarse-grained than in the fine-grained samples.

In considering the trends in these plots, it is important to recognize that concentrations may be influenced by physical sediment factors as well as proximity to sources. In general, sediments with more silt and clay (percent fines) and higher TOC have higher concentrations than sediments with sandy sediments and low TOC. Therefore, some of the variation represented in the plots could be attributable to spatial and temporal variations in sediment type rather than in changes in concentrations per se. A draft RMP Technical Report to be released in the coming year examines sediment trends which take into account covarying factors of TOC and grain size.

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3.5 Discussion

3.5.1 Discussion

Bay sediments are evaluated through comparisons to several sets of sediment quality guidelines described in Section 3.2. Although these guidelines hold no regulatory status, they provide concentration thresholds that may be used to assess the status of the Bay's sediments. They also provide one of three elements in a sediment quality assessment approach known as the Sediment Quality Triad (the other two being sediment toxicity and benthos (see Section 3.5.4).

High contaminant concentrations in sediments usually reflect a proximity to a source, anthropogenic or otherwise. This was illustrated by the RMP's Estuary Interface Pilot Study in Coyote Creek and Guadalupe River in South Bay (SFEI, 1999). However, concentrations can vary not only due to proximity to sources but also by the many and complex processes involved in sediment dynamics. For example, sediments with more silt and clay minerals contain higher concentrations of most contaminants than coarser, more sandy sediments because of their geochemical properties (Luoma, 1990; Horowitz, 1991). The strength and magnitude of freshwater inflows, through the transport of sediments and contaminants in both the dissolved and particulate fractions of the flows, may alter sediment type and contaminant distribution, particularly in estuarine regions such as San Francisco Bay (Krone, 1979). These kinds of relationships should be kept in mind in reviewing this summary.

3.5.2 Spatial Distributions

The southern sloughs and South Bay exhibit elevated contaminant concentrations when compared with the other reaches, as observed in previous years. The Estuary Interface Pilot Study stations located upstream from the southern sloughs also showed concentrations higher than those in the Central Bay, Northern Estuary, and river reaches, further emphasizing this pattern (SFEI, 1999; SFEI, 2000). Limited sampling points also hint at concentration gradients in some of the BPTCP sites (Mission Creek, Islais Creek, Peyton Slough), but more data are needed to confirm this. Concentration gradients of arsenic, cadmium, chromium, lead, selenium, zinc, PAHs, and PCBs were seen in channelized creeks draining to San Leandro Bay in an intensive, localized study (Daum et al., 2000).

Average concentrations of cadmium, lead, silver, zinc, PAHs, and PCBs were highest in sediments of the Southern Sloughs. The Estuary Interface sediment samples had the highest concentrations of chromium, copper, mercury, nickel, and selenium. Conversely, all contaminants except arsenic and dieldrin were lowest in the River and Central Bay reaches. As in previous years, arsenic was an exception to these trends with the highest average concentrations in the Northern Estuary and the lowest in the southern sloughs. Most of the high concentration values for individual stations were found at either southern slough or Estuary Interface stations.

Estuary Interface Study sites, and the southern slough sites near the outfalls San Jose and Sunnyvale usually had the most Effects Range exceedances (see Table 3.1). This is probably due to the fact that the watersheds which drain to this Bay reach cover a large area and consist of large percentages of urban land uses. The lowest sediment contaminant concentrations and number of guideline exceedances occurred at Richardson Bay, Red Rock, and Pacheco Creek stations, all of which are either Central Bay and/or coarse sediment stations. The 1998 El Niño produced observable changes in chlordanes in the Central Bay and PCBs at the Rivers (SFEI, 2000).

3.5.3 Trends

Two time scales are included in the current RMP sampling design: seasonal (wet and dry) and year to year. Trends in sediment contamination have been observed at both scales. Seasonal variation in some contaminants occurred at some sites, although only arsenic (Figure 3.1), mercury (Figure 3.6), and selenium (Figure 3.8) showed consistent variation throughout the Estuary based on seasonality (higher during dry weather sampling).

There were significant long term trends at a dozen RMP sites throughout most of the Estuary for one or more contaminants after normalizing for grain size and total organic carbon (TOC) (Thompson and Daum, 1999). Chromium and nickel showed significant increases at 9 and 7 of these stations respectively. Other contaminants showed increases or decreases at three or fewer stations. Coyote Creek, Pinole Point, and Petaluma River showed numerous significant changes in contaminant concentrations over time. Overall, significant long-term (five to eight years) trends have been observed in less than 10% of RMP samples collected through 1997. The coarse sediment stations generally had the lowest range of variation over time for metals, but not organics.

Interestingly, the Southern Sloughs and River Stations showed no significant trends. This may be due to the inherently dynamic hydrologic conditions in these areas. Time trends analyses require a large enough sample size i.e. enough measurements over time at a given location, to produce statistically significant results. The majority of RMP samples showed no significant changes in contaminant concentrations over time. This may be due to the fact that there were indeed no changes, or that there was not a large enough sample size to make a determination.

Sampling at a series of depths in the sediment can reveal trends in historical contamination levels. Such sampling indicates that most contaminants have dropped from peak levels seen in the 1960s and 1970s (Venkatesan et al. 1999) probably resulting from wastewater treatment improvements, product bans, and other regulatory actions.

Changes in sediment concentrations over time reflect a complex set of processes that include deposition, resuspension, mixing and transport, and biogeochemistry. The interplay of these processes determines the "active sediment layer" and any burial rates. The actual depth of the active layer was determined to be a key factor in the mass balance, and flux of chlorinated hydrocarbons in sediments (Davis et al. 1999). Active mixing and low deposition rates generally account for the long resident times of contaminants in surface sediments in the Bay.

Our understanding of sediment contamination trends in the Estuary were placed in a historic perspective by recently published USGS sediment coring studies (Van Geen and Luoma, 1999). The earliest evidence of contamination associated with human occupation and industrialization was found for mercury, in sediments deposited between 1850 and 1880 as a result of gold mining activities. Maximum concentrations were 20 times the baseline (i.e. pre-anthropogenic) concentrations. Silver, lead, copper, and zinc contamination first appeared after 1910 in the Bay sediment record. Most contaminant concentrations have decreased from the peaks seen in the 1960s and 1970s (Hornberger, et al. 1999).

3.5.4 Sediment Toxicty

Toxicity tests were conducted to indicate whether sediments were toxic to sensitive organisms, and are described in Section 3.3. Because these bioassays were conducted using non-resident organisms in laboratory exposures, the results may not necessarily indicate that actual ecological impacts occurred.

Bay sediments were toxic to either amphipods or bivalve embryos in 70% of the RMP samples tested between 1991 and 1998. The two tests showed different patterns of toxicity at the different RMP sites. Toxicity at sites near the confluence of tributaries showed higher incidence of bivalve embryo toxicity, and sites in the South Bay showed higher incidence of amphipod toxicity. Sediments were usually more toxic during the wet, than the dry sampling period. Other than an increasing trend in toxicity at Yerba Buena Is., there have been no significant increases or decreases in the incidence of toxicity at the RMP sites.

The exact causes of the toxicity to the amphipods and bivalve embryos are not known. However, analyses using several years of monitoring data suggested that the cumulative effects of mixtures of contaminants was associated with amphipod toxicity (Thompson et al. 1999c). A few individual contaminants were identified at some sites as probable determinants of toxicity. For example, toxicity at Grizzly Bay was related to covarying patterns of total chlordane, silver and cadmium between 1991-1996. At Alameda and San Bruno Shoal, seasonal variation in PAHs were related with percent survival. For the bivalve embryos, TIEs were conducted on the sediment elutriates from the Sacramento, and San Joaquin rivers and Grizzly Bay in 1997 and 1998, and indicated that dissolved metals (divalent cations) were probably responsible for the observed toxicity. Non-polar organic contaminants were also implicated at the Sacramento River site (Phillips et al., 1999). The above results have suggested that sediment toxicity may be related to different contaminants at the various RMP sites, and may change over time.

Another major study of sediment toxicity was conducted as part of the Bay Protection and Toxic Cleanup Program (BPTCP) in 1997 (Hunt et al. 1998). Toxicity tests of reference sites showed results in survival, growth, and larval development similar to those observed in laboratory controls.

During the past two years RMP investigators have conducted additional sampling and experiments focused on discovering the cause(s) of sediment toxicity. Those studies have demonstrated the complex nature of sediment toxicity owing to the numerous contaminant and non-contaminant factors in estuary sediments. Solid phase sediment toxicity to amphipods has been frequently observed at Redwood Creek and Grizzly Bay. Exposure to pore water from those sites did not produce toxicity, but exposure to bulk sediment did, suggesting that the toxicity is associated with ingestion of sediment particles. Amphipods accumulated PAHs, organochlorine pesticides, and PCBs from exposures to both bulk sediment and pore water, but not to levels known to cause mortality. Accumulation of PAHs accounted for most of the accumulation and may be a key causitive agent. However, mixtures of contaminants are also believed to be important agents (Anderson et al. 2000).

Sediment elutriates (water soluble fraction) have been toxic to bivalve larvae at the Sacramento, and San Joaquin River, and Grizzly Bay sites since 1993. TIEs have been conducted to evaluate which contaminants were responsible. Trace metals, particularly copper were shown to be, at least partially responsible for the toxicity, but organic contaminants were also identified as toxic components at the Sacramento River site (Phillips et al. 2000).

3.5.5 Effects of Sediment Contamination

The only RMP component that has addressed actual ecological effects of contamination in the Bay has been the Benthic Pilot Study. Preliminary screening of benthic samples (n=501) collected between 1994 and 1997 indicated that 16.6% percent of those samples had some evidence of contaminant impacts (Lowe et al. 1999). The remaining samples were considered to be reference, or unimpacted benthic samples and used in comparisons with samples collected by BADA near three large wastewater discharges and samples collected by the BPTCP. Only a few samples from near the BADA outfalls (1994-1997) were considered to be slightly impacted (Thompson et al., 1999a). BPTCP samples from several locations along the margins of the Bay were moderately to severely impacted (Hunt et al. 1998).

In another EPA funded study of the role of introduced species on benthos, sites with elevated sediment contamination and slightly to moderately impacted benthos had lower proportions of introduced species the reference sites (Lee et al. 1999).

The USGS has also been studying the effects of sediment contamination on benthic organisms. Bioaccumulation of metals by clams near the Palo Alto wastewater discharge (Hornberger, et al., 2000has shown that concentrations in their tissues has decreased as emissions of metals have decreased from those POTWs. The reproductive cycle and condition of the introduced Asian clam Potamocorbula amurensis, the dominant species in the estuarine portions of the Bay, were impaired by exposure to cadmium in sediments in the north Bay. The RMP Sediment Workgroup has recommended that the RMP undertake studies of resident, deposit feeding bivalves to improve our understanding contaminant uptake and effects on the benthos.

3.5.6 Assessment of Sediment Conditions using the Sediment
Quality Triad

Assessments of sediment condition are often conducted using an approach that considers information about sediment contamination, sediment toxicity, and benthic community conditions; bioaccumulation or other biomarkers may also be used. That approach is known as the Sediment Quality Triad (Chapman et al., 1997). RMP results from 1998 marked the first year that a triad assessment could be accomplished for the RMP sites (Table 3.2).

Sediment contamination in each sample was evaluated by considering the number of contaminants that exceeded the San Francisco Estuary Ambient Sediment Concentration (ASC, Smith and Riege, 1998), Effects-Range guidelines (ERL and ERM, Long et al., 1995), and the ERM quotients (Long et al., 1998, see Sediment chapter of the 1998 RMP Annual Report for details). The number of sediment contaminants above the ERL or ERM guidelines has been used to predict potential sediment toxicity (Long et al., 1998). More than four ERM exceedances predicted toxicity in 68% of the tests, and when 10 to 14 ERLs were exceeded more than 89% of the samples were toxic. Therefore, to evaluate the 1998 RMP sediment results, sediment samples were considered possibly toxic if 4 or more ERMs or 10 or more ERLs were exceeded, or if half (22) of the ASC values were exceeded.

The mean ERM quotient (mERMq) may be considered to be a cumulative index of sediment contamination related to adverse ecological effects. Amphipod toxicity was significantly, and inversely correlated to mERMq (Thompson et al., 1999). Analysis of RMP data collected between 1991 and 1997 showed that mERMq values below 0.178 were never toxic toxic to amphipods, while mERMq values above 0.288 were toxic in 64% of the tests. Those values were used to evaluate potential for toxicity in the 1998 RMP samples.

Benthic assessments were made for nine sediment samples each season by comparing key benthic attributes at test sites to "ambient" reference conditions resulting in a qualitative comparison of each benthic community to "ambient" reference communities. The preliminary benthic assessment method used was developed under the RMP Benthic Pilot Study (Lowe et al., 1999). The sediment assessment showed that 29 of 52 samples had mERMq values above 0.288, suggesting a potential for toxicity. Of those, thirteen were shown to be toxic by the RMP toxicity tests, three were not; thirteen were not tested. Eight of the 29 samples had more than ten ERL exceedances (one of these had more than four ERM exceedances), which added to the weight-of-evidence for potential toxicity or impairment at those sites.

Three samples from the benthic assessments indicated slight ecological impacts even though toxicity tests were not toxic, mERMq values for two of the samples predicted toxicity (were above 0.288). Six benthic samples showed no impact but the sediments were toxic. Only two samples had mERMq values that predicted toxicity. Redwood Creek (BA41) and San Bruno Shoal (BB15) had no discernable benthic impact although samples had elevated mERMqs and were toxic to amphipods in three of the four samples. Only one sample, Davis Point (BD41), showed no evidence of in pacts in sediment chemistry, toxicity, or benthos.

Sediment assessments are useful tools that integrate sediment contamination, toxicity and ambient ecological condition into a weight-of-evidence evaluation of condition of the sediments in the Estuary. Each component of the triad is analyzed independently and should be related, but as shown, they not always provide similar answers. This kind of ecological complexity demonstrates the need to consider as much data as possible in sediment assessments and to undertake studies to try to reconcile and understand apparent contradictions.

3.5.7 References

Anderson, B., Hunt, J., Phillips, B., Sericano, J., 2000. Investigations of chemicals associated with amphipod mortality at two Regional Monitoring Program stations. Draft RMP Technical Report. SFEI, 16 pp.

Chapman, P. M., Anderson, B, Carr, S., et al.,1997. General Guidelines for using the Sediment Quality Triad. Marine Pollution Bulletin. 34:368-372.

Daum, T., and G. Bartow. 2000. Sediment Contamination in San Leandro Bay, CA: a Watershed-based Investigation. Draft Report to SFBRWQBC, San Francisco Estuary Institute. Oakland, CA.

Davis, J.A. 1999. Technical Report of the Chlorinated Hydrocarbon Workgroup. San Francisco Estuary Institute, Oakland, CA.

Gandesbery, T. and F. Hetzel. 1999. Ambient concentrations of toxic chemicals in San Francisco Bay sediments: Summary. In: 1997 Annual Report: San Francisco Estuary Regional Monitoring Program for Trace Substances. San Francisco Estuary Institute, Oakland, CA. pp. 140Ê147.

Hornberger, M., S. Luoma, A. van Geen, C. Fuller, and R. Anima. 1999. Historical Trends of Metals in the Sediments of San Francisco Bay, California. Mar. Chem. 64: 39-55.

Hornberger, M., S. Luoma, D. Cain, F. Parchaso, C. Brown, R. Bouse, C. Wellise, J. Thompson. 2000. Linkage of Bioaccumulation and Biological Effects to Changes in Pollutant Loads in South San Francisco Bay. Environmental Science and Technology. 60.

Horowitz, A. 1991. A Primer on Sediment-Trace Element Chemistry, 2nd rev. ed. Lewis Publishers/CRC Press, Inc. Boca Raton, FL. 136 pp.

Hunt, J.W., B.S. Anderson, S. Tudor, M.D. Stephenson, H.M. Puckett, F.H. Palmer, and M. Reeve. 1996. Marine Bioassay Project, Eighth Report: Refinement and implementation of four effluent toxicity testing methods using indigenous marine species. Report #94-4. State Water Resources Control Board, Sacramento, CA. pp. 85-104.

Hunt, J., B. Anderson, B. Phillips, J. Newman, R. Tjeerdema, K. Taberski, C. Wilson, M. Stephenson, H. Puckett, R. Fairey, and J. Oakden. 1998. Bay Protection and Toxic cleanup Program Final Technical Report. California State Water Resources Control Board, Sacramento, CA.

Krone, R. 1979. Sedimentation in the San Francisco Bay system, In: San Francisco Bay, the Urbanized Estuary. T. Conomos, ed. Pacific Div. of the Amer. Assoc. for the Advancement of Science, San Francisco. pp. 85-96.

Long, E.R. and L.G. Morgan. 1990. The potential for biological effects of sediment-sorbed contaminants tested in the National Status and Trends Program. NOAA Tech. Memo NOS OMA 52. National Oceanic and Atmospheric Administration, Seattle, WA. 175p.

Long, E.R., D.D. MacDonald, S.L. Smith and F.D. Calder. 1995. Incidence of adverse biological effects within ranges of chemical concentrations in marine and estuarine sediments. Env. Mgmt. 19:18Ê97.

Long, E. R., L. J. Field, and D. D. MacDonald. 1998. Predicting toxicity in marine sediments with numerical sediment quality guidelines. Environmental Toxicology and Chemistry. 17:714-727

LTMS. 1996. Draft Environmental Impact Statement/Programmatic Environmental Impact Report, Vol. 1. Long Term Management of Sediments, Oakland, CA.

Luoma, S.N. 1990. Processes affecting metal concentrations in estuarine and coastal marine sediments. In: Heavy metals in the marine environment. R.W. Furness and P.S. Rainbow, (eds.). CRC Press, Inc., Boca Raton, FL.

Lowe, S., B. Thompson. 2000. A Preliminary Assessment of Benthic Responses to Sediment Contamination in San Francisco Bay. Regional Monitoring Program Technical Report. San Francisco Estuary Institute, Oakland, CA.

Phillips, B., Anderson, B., Hunt, J. 2000. Investigations of sediment elutriate toxicity at three estuarine stations in San Francisco Bay, California. Draft RMP Technical Report. SFEI, 16 pp.

SFEI. 1999. 1997 Annual Report: San Francisco Estuary Regional Monitoring Program for Trace Substances. San Francisco Estuary Institute, Oakland, CA.

SFEI. 2000. In Preparation. 1998 Annual Report: San Francisco Estuary Regional Monitoring Program for Trace Substances. San Francisco Estuary Institute, Oakland, CA.

Smith, R.W. and L. Riege, 1998. San Francisco Bay Sediment Criteria Project Ambient Analysis Report. Report prepared for the CRWQCB by EcoAnalysis, Inc. Ojai, CA.

Taylor, K., W. Pease, J. Lacy, and M. Carlin. 1992. Mass Emissions Reduction Strategy for Selenium. San Francisco Regional Water Quality Control Board, Oakland, CA. 61p.

Thompson, B., Anderson, B., Hunt J., Taberski K., Phillips B. 1999. Relationships Between Sediment Contamination and Toxicity in San Francisco Bay. Marine Environ. Research.

Thompson, B. and T. Daum. 1999. Atlas of Sediment Contamination, Toxicity, and Benthic Assemblages in San Francisco Bay. Draft Regional Monitoring Program Report. San Francisco Estuary Institute. Oakland, CA.

U.S. EPA. 1991. Proposed sediment quality criteria for the protection of benthic organisms: 5 draft reports: Acenaphthene; Dieldrin; Endrin; Fluoranthene; Phenanthrene.

van Geen, A., and S. Luoma. 1999. The Impact of Human Activities on Sediments of San Francisco Bay, California: an Overview. Mar. Chem. 64: 1-6.

Wolfenden, J.D. and M.P. Carlin. 1992. Sediment screening criteria and testing requirements for wetland creation and upland beneficial reuse. California Environmental Protection Agency and California Regional Water Quality Control Board.

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3.6 References

Barrick, R., S. Becker, R. Pastorok, L. Brown, and H. Beller. 1988. Sediment quality values refinement: 1988 update and evaluation of Puget Sound AET. Vol. I. Prepared for Tetra Tech Inc. and U.S. EPA Region 10. PTI Environmental Services, Bellevue, WA.

Gandesbery, T. 1998. Ambient concentrations of toxic chemicals in sediments. MEMO: Regional Boards Staff, from Tom Gandesbery, March 1998, File No: 1150.00.

Gandesbery, T. and F. Hetzel. 1999. Ambient concentrations of toxic chemicals in San Francisco Bay sediments: Summary. In 1997 Annual Report: San Francisco Estuary Regional Monitoring Program for Trace Substances. San Francisco Estuary Institute, Oakland, CA. pp. 140Ê147.

Hornberger, M.I., S.N. Luoma, A. van Geen, C. Fuller, and R. Anima. 1999. Historical trends of metals in the sediments of San Francisco Bay, California. Marine Chemistry, 64:39Ê55.

Hunt, J.W., B.S. Anderson, S. Tudor, M.D. Stephenson, H.M. Puckett, F.H. Palmer, and M. Reeve. 1996. Marine Bioassay Project, Eighth Report: Refinement and implementation of four effluent toxicity testing methods using indigenous marine species. Report #94-4. State Water Resources Control Board, Sacramento, CA. pp. 85Ê104.

Long, E.R. and L.G. Morgan. 1990. The potential for biological effects of sediment-sorbed contaminants tested in the National Status and Trends Program. NOAA Tech. Memo NOS OMA 52. National Oceanic and Atmospheric Administration, Seattle, WA. 175p.

Long, E.R., D.D. MacDonald, S.L. Smith and F.D. Calder. 1995. Incidence of adverse biological effects within ranges of chemical concentrations in marine and estuarine sediments. Env. Mgmt. 19(1):81Ê97.

Pereira, W.E., F.D. Hostettler, S.N. Luoma, A. van Geen, C.C. Fuller, and R.J. Anima. 1999. Sedimentary record of anthropogenic polycyclic aromatic hydrocarbons in San Francisco Bay, California. Marine Chemistry 64:99-113.

Smith, R.W. and L. Riege, 1998. San Francisco Bay Sediment Criteria Project Ambient Analysis Report. Report prepared for the CRWQCB by EcoAnalysis, Inc. Ojai, CA.

Taylor, L., W. Pease, J. Lacy, and M. Carlin. 1992. Mass Emissions Reduction Strategy for Selenium. San Francisco Regional Water Quality Control Board, Oakland, CA. 61p.

Wolfenden, J.D. and M.P. Carlin. 1992. Sediment screening criteria and testing requirements for wetland creation and upland beneficial reuse. California Environmental Protection Agency and California Regional Water Quality Control Board.

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