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The Regional Monitoring Program for Water Quality in San Francisco Bay (RMP) started implementing a new design for North Bay selenium (Se) sampling in 2019 after a long-term USGS program was terminated in 2017. To determine if the RMP sampling and analysis methods are producing similar results to the USGS study, we compared Se concentrations and stable isotope values in clams at two stations in Suisun Bay, California, that were sampled by the USGS long-term monitoring program from 1995-2010 and the RMP in 2019-2020. We also compared Se concentrations in water (dissolved and particulate) from the RMP Status and Trends sampling in Suisun Bay (1993-2019) to the samples collected as part of this study. 

Spatial patterns in clam Se concentrations between the USGS and RMP studies were similar, with lower concentrations at Station 4.1 (Suisun Bay) than at Station 8.1 (Carquinez Strait). Se concentrations at both stations were consistently lower for the RMP samples than those reported in the long-term USGS dataset. Stable isotope values for δ13C and δ15N were similar for the USGS and RMP samples with δ13C and δ15N more enriched at Station 8.1 than 4.1. However, there was not close alignment of the RMP samples to the USGS long-term average, particularly at Station 8.1. Average dissolved Se concentrations in water were consistently lower than the long-term average at Station 4.1 and similar to or above the long-term RMP Status and Trends (S&T) average at Station 8.1. Particulate Se concentrations at Stations 4.1 and 8.1 were nearly one-third of the long-term S&T average in Suisun Bay, likely due to a change in methods for calculating particulate Se. 

Additional information is needed to evaluate whether the lower Se concentrations measured in clams as part of the RMP study could be suggestive of declining Se concentrations in North Bay clams between 2010 and 2019 or an artifact of the new analytical lab. Additional data from samples collected by the USGS from 2011-2017 should be examined to fill the gap between the datasets. Continued RMP monitoring will also be valuable in evaluating long-term trends.

This report presents the findings from a study evaluating selenium concentrations in white sturgeon (Acipenser transmontanus) tissues collected during the 2015-2017 Sturgeon Derby events in North San Francisco Bay. The goal of this study was to investigate the distribution of selenium among sturgeon tissues to inform the toxicological and regulatory interpretation of selenium measured in non-lethally collected tissues, including muscle plugs and fin rays. This technical report provides documentation of the study and presents its major findings.

The response of shallow groundwater to sea-level rise is a relatively new field of study. For low-lying coastal communities, sea-level rise adaptation efforts must consider the potential for groundwater rise to avoid maladaptation. The need to better understand this slow and chronic threat was identified as a critical data gap in the San Francisco Bay Area’s (Bay Area’s) adaptation efforts during the Bay Area Groundwater and Sea-Level Rise Workshop in 2019.

Pathways Climate Institute LLC (Pathways) and the San Francisco Estuary Institute (SFEI) gathered and analyzed multiple data sets and collaborated with city and county partners to analyze and map the existing “highest annual” shallow groundwater table and its likely response to future sea-level rise. This effort covers four counties (Alameda, Marin, San Francisco, San Mateo) and was funded by the Bay Area Council’s California Resilience Challenge. The study focused on the San Francisco Bay side of each county and does not include the Pacific coastline of Marin, San Francisco, nor San Mateo Counties. An advisory committee composed of city and county representatives provided essential support by gathering data and reviewing depth-to-groundwater maps. Additional academic and agency advisors participated in project team meetings and informed project direction. This effort produced the following publicly available data and online tools to support adaptation efforts:

• Existing and future condition depth to groundwater GIS data available for download (geodatabase format).
• A StoryMap providing background information and graphical representations of the processes and impacts of groundwater rise.
• Web maps showing: (1) existing depth to groundwater; and (2) a comparison of the extent of emergent groundwater to the extent of coastal flooding under various sea-level-rise scenarios.

EXECUTIVE SUMMARY
As sea level rise accelerates, our shores will be increasingly vulnerable to erosion. Particular concern centers around the potential loss of San Francisco Bay’s much-valued tidal marshes, which provide natural flood protection to our shorelines, habitat for native wildlife, and many other ecosystem services. Addressing this concern, this study is the first systematic analysis of the rates of marsh retreat and expansion over time for San Pablo Bay, located in the northern part of San Francisco Bay.

Key findings:
• Over the past two decades, more of the marshes in San Pablo Bay have expanded (35% by length) than retreated (6%).
• Some areas have been expanding for over 150 years.
• Some marsh edges that appear to be retreating are in fact expanding rapidly at rates of up to 8 m/yr.
• Marsh edge change may be a useful indicator of resilience, identifying favorable sites for marsh persistence.
• These data can provide a foundation for understanding drivers of marsh edge expansion and retreat such as wind direction, wave energy, watershed sediment supply, and mudflat shape.
• This understanding of system dynamics will help inform management decisions about marsh restoration and protection.
• This study provides a baseline and method for tracking marsh edge response to current and future conditions, particularly anticipated changes in sea level, wave energy, and sediment supply.

Recommended next steps:
• This pilot study for San Pablo Bay marshes should be extended to other marshes in San Francisco Bay.
• These initial marsh expansion and retreat findings should be further analyzed and interpreted to improve our understanding of system drivers and identify management responses.
• A program for repeated assessment should be developed to identify and track changes in shoreline position, a leading indicator of the likelihood marsh survival.

Stormwater agencies in the San Francisco Bay Area are identifying watershed areas that are polluted with PCBs in order to prioritize management efforts to reduce impairment in the Bay caused by PCBs carried in stormwater. Water sampling during storms has been used to characterize PCB concentrations but management prioritization based on the comparison of concentrations between watersheds is made difficult due to variations in flow and sediment erosion between storms and in relation to varying land use. In addition, identifying PCB source areas within priority watersheds has proven complex and costly. To address these challenges, the San Francisco Bay Regional Monitoring Program (RMP) has developed two new interpretive methods based on storm-event PCB yields (PCBs mass per unit area per unit time) and fingerprints of Aroclors (commercial PCB mixtures) that make existing data more useful for decision-making. 

The objectives of this study were to: 

• Apply the yield method to the regional stormwater dataset and provide new rankings, 
• Estimate the presence of Aroclors in samples where congener data are available
• Evaluate data weaknesses and recommend watersheds to resample, and
• Classify watersheds into high, medium, and low categories for potential management.

Sediment bulk density is the total mass of mineral and organic sediment within a defined volume. It is a key variable in many research questions pertaining to Bay sediment studies but one that is often poorly quantified and can be misinterpreted. The motivation for this report comes from a recommendation by Schoellhamer et al. (2018) to compile more accurate estimates of bulk density of Bay sediments to convert between volume and mass with a higher level of certainty. Through funding and guidance from the Bay Regional Monitoring Program Sediment Work Group, this report is a first step towards compiling the available data on sediment bulk densities across Bay habitats and along salinity gradients to provide better information for resource managers and others working on sediment-related issues. This report discusses the need to know the bulk density of Bay soils to convert between sediment mass and soil volume; clarifies general definitions and common points of confusion related to sediment bulk density; compiles primary sources of bulk density measurements, secondary sources of bulk density estimates, and standard engineering estimates of bulk density for different habitats in San Francisco Bay; and, provides a database where practitioners can track, analyze, and share bulk density measurements.
 

This report presents a strategy and multi-year workplan for modeling polychlorinated biphenyls (PCBs), contaminants of emerging concern (CECs), and sediment in San Francisco Bay (the Bay). Robust in-Bay fate modeling is needed to address priority management questions that have been identified for these constituents.

The strategy for in-Bay modeling presented in this report is a major element of a broader, integrated strategy that is being developed across RMP Workgroups for modeling contaminants flowing from the Bay watersheds and other pathways into the Bay. The broader project is expected to yield an integrated strategy in 2022, followed by implementation of a pilot effort in 2023. Coordination of the in-Bay modeling effort with the broader integrated strategy and other modeling work (e.g., nutrient modeling under the Nutrient Management Strategy) will be critical to optimizing use of the funds allocated to modeling.

This data release presents digital surface models (DSMs) and orthomosaic images of the Whale's Tail Marsh region of South San Francisco Bay, CA. The data were created using structure-from-motion (SfM) processing of repeat aerial imagery collected from fixed-wing aircraft. The raw images were acquired from an approximate altitude of 427 meters (1,400 feet) above ground level (AGL), using a Hasselblad A6D-100c camera fitted with an HC 80 lens, resulting in a nominal ground-sample-distance (GSD) of 2.5 centimeters per pixel. The acquisition flight lines were designed to provide approximately 50 percent overlap between adjacent flight lines (sidelap), with approximately 70 percent overlap between sequential images along the flight line (forelap). Survey control was established using an onboard camera-synchronized dual-frequency GPS system as well as ground control points (GCPs) distributed throughout the survey area and measured using survey-grade post-processed kinematic (PPK) GPS. Both the data from the onboard GPS and from the GPS used to measure the GCPs were post-processed using a nearby Continuously Operating Reference Station (CORS) operated by the National Geodetic Survey (NGS). Structure-from-motion processing of these data was conducted using a "4D" processing workflow in which imagery from each of the different acquisition dates were co-aligned to increase relative spatial precision between the final data products.

The Dredged Material Management Office (DMMO) is responsible for annually approving dredging and disposal of millions of cubic yards of sediment to maintain safe navigation in San Francisco Bay. Dredged sediment is characterized for physical, chemical, and biological characteristics to ensure sediment disposed of in the Bay or at beneficial use locations does not cause adverse environmental impacts. Bioaccumulation thresholds and total maximum daily loads (TMDLs) have been established for several contaminant classes, including PCBs, and are used by the DMMO to determine whether sediment contaminant levels trigger subsequent bioaccumulation testing. Sediment with contaminant concentrations above any TMDL levels cannot be disposed of within the Bay but may be further evaluated for upland reuse and ocean disposal. The objective of this study was to evaluate PCB bioaccumulation data from navigational dredging projects to assess the existence of correlations between sediment chemistry and bioaccumulation test results. The motivation for this study was to determine whether the current PCB bioaccumulation trigger is effective in differentiating sediment bioaccumulation concerns. The DMMO may use the results of this study to inform evaluation requirements for PCBs, particularly in support of modifying the terms of the Long-term Management Strategy for San Francisco Bay (LTMS) programmatic Essential Fish Habitat (EFH) agreement concerning PCB bioaccumulation testing. 

Urban-wildland interfaces in the western US are increasingly threatened by the growing number and intensity of wildfires, potentially changing the type of contaminants released into the landscape as more urban structures are burned. In October 2017, the Tubbs, Nuns, and Atlas wildfires devastated communities in Northern California (Figure 1), burning over 8,500 buildings and 210,000 acres of land in the span of 24 days (California Department of Forestry and Fire Protection 2017). Together, these wildfires were the most destructive and costliest fires in the history of California at that time (California Department of Forestry and Fire Protection 2019). 

Post-wildfire monitoring efforts in impacted watersheds typically focus on a few well-established water quality and chemistry concerns (McKee et al. 2018). Few studies go beyond these limited targeted analyses and attempt to identify the multitude of other fire-related compounds that are released from or form as the result of combustion of residential, commercial, and industrial structures in urban-wildland interfaces. Some of these unidentified compounds may be toxic to aquatic ecosystems or human health, and may pose risks to wildlife or in water bodies that act as drinking water supplies to nearby communities.  

This report summarizes the precipitation, discharge, and sediment conditions observed from October 1, 2016 to September 30th, 2017 (Water Year (WY) 2017) in the Arroyo de la Laguna watershed, with a focus on the Arroyo Mocho watershed. This information was collected by the Zone 7 Water Agency to support operation and maintenance of their flood control facilities. Additionally, this and similar information collected in WY 2018 and 2019 will be utilized to update the Arroyo Mocho watershed sediment budget (Pearce et al, 2020).

Recent modeling has demonstrated that sediment supply is one of the primary environmental variables that will determine the sustainability of San Francisco Estuary tidal marshes over the next century as sea level rises. Therefore, understanding the environmental controls on sediment flux within the San Francisco Estuary is crucial for optimal planning and management of tidal marsh restoration. Herein, we present suspended-sediment flux estimates from water year (WY) 2009–2016 from the San Francisco Estuary to investigate the environmental controls and impact of the record 2013–2016 California drought. During the recent drought, sediment flux into Lower South Bay, the southernmost subembayment of the San Francisco Estuary, increased by 345% from 114 kt/year from WY 2009 to 2011 to 508 kt/year from WY 2014 to 2016, while local tributary sediment flux declined from 209 to 51 kt/year. Total annual sediment flux from WY 2009 to 2011 and 2014 to 2016 can be predicted by total annual freshwater inflow from the Sacramento-San Joaquin Delta (R2 = 0.83, p < 0.01), the primary source of freshwater input into the San Francisco Estuary. The volume of freshwater inflow from the Sacramento-San Joaquin Delta is hypothesized to affect shoal-to-channel density gradients that affect sediment flux from broad, typically more saline and turbid shoals, to the main tidal-channel seaward of Lower South Bay. During the drought, freshwater inflow from the Sacramento-San Joaquin Delta decreased, and replacement of typically more saline shoal water was reduced. As a result, landward-increasing cross-channel density gradients enhanced shoal-to-channel advective flux that increased sediment available for tidal dispersion and drove an increase in net-landward sediment flux into Lower South Bay.

This study investigates the relative distribution, health, and regeneration patterns of two major stands of sycamore alluvial woodland (SAW), representing managed and natural settings. Using an array of ecological and geomorphic field analyses, we discuss site characteristics favorable to SAW health and regeneration, make recommendations for restoration and management, and identify next steps. Findings from this study will contribute to the acquisition, restoration, and improved management of SAW as part of the Santa Clara Valley Habitat Plan (VHP).

This document supports planting-based approaches for sycamore enhancement by providing site-level revegetation techniques for installing, maintaining and monitoring sycamore plantings.

The “Sycamore Alluvial Woodland Restoration and Enhancement Suitability Study” addresses distribution and regeneration patterns and restoration strategies of sycamore alluvial woodland (SAW) habitat, a unique and relatively rare native vegetation community adapted to California’s intermittent rivers and streams. The report was produced by SFEI and H. T. Harvey & Associates, as part of the US EPA Water Quality Improvement Fund Preparing for the Storm grant, led by Zone 7 Water Agency.

California Senate Bill 1263 (2018) tasks the Ocean Protection Council (OPC) with leading statewide efforts to address microplastic pollution, and requires the OPC to adopt and implement a Statewide Microplastics Strategy related to microplastic materials that pose an emerging concern for ocean health. Key questions remain about the sources and pathways of microplastics, particularly to urban runoff, to inform an effective statewide microplastics management strategy. The OPC funded this work to inform these microplastics efforts. The purpose of this project was to build conceptual models that synthesize and integrate our current understanding of microplastic sources and pathways to urban runoff in order to provide future research priorities that will inform how best to mitigate microplastic pollution. Specifically, we developed conceptual models for cigarette butts and associated cellulose acetate fibers (Section 2), fibers other than cellulose acetate (Section 3), single-use plastic foodware and related microplastics (Section 4), and tire particles (Section 5), which were prioritized based on findings from the recent urban stormwater monitoring of microplastics in the San Francisco Bay region. Conceptual models specific to each of these particle types are valuable tools to refine source identification and elucidate potential source-specific data gaps and management options.