Skarry Removal

California State Lands Commission (SLC) | May 1st, 2025

The Commission’s contractor will remove booms, winches, and other superstructures from the crane barges on site. This equipment will be cut into pieces and placed on a

The Commission’s contractor will remove booms, winches, and other superstructures from the crane barges on site. This equipment will be cut into pieces and placed on a materials barge for recycling. Floating booms will surround the work site and contain any debris. Once lightened of equipment, a crane will remove the two smaller barges directly from the water. The largest barge will be refloated and towed by water to the Mare Island shipyard, where it will be removed from the water and demolished. Scrap metal will be recycled, and other debris will be hauled to a landfill for disposal. Click here for the staff report that accompanied the plan.

Small Populations in Jeopardy: A Delta Smelt Case Study

Social Science Research Network (SSRN) | February 21st, 2021

Under §7 of the federal Endangered Species Act, federal agencies must ensure that actions they authorize, fund, or carry out are “not likely to jeopardize the continue

Under §7 of the federal Endangered Species Act, federal agencies must ensure that actions they authorize, fund, or carry out are “not likely to jeopardize the continued existence of any endangered species or threatened species or result in the destruction or adverse modification of habitat of such species.” For species with low and declining populations, applying this standard is legally and scientifically difficult. The U.S. Fish and Wildlife Service (FWS) faced this problem in its recent biological opinion (BiOp) analyzing impacts to threatened Delta smelt from water project operations in the California Delta. FWS concluded the “species’ recent abundance trends strongly suggest it is in the midst of demographic collapse,” and most recent surveys to locate smelt have failed to find them. Nevertheless, FWS approved agency actions that will likely increase extinction risk for Delta smelt. This Comment illustrates, through a case study of the Delta smelt BiOp, the difficulties in making ESA jeopardy determinations for species on the brink of extinction. We conclude that the myriad challenges inherent in conservation of some small and declining populations make reasoned §7 analysis difficult, bordering on impossible.

Small Tributaries Pollutants of Concern Reconnaissance Monitoring: Application of Storm-event Loads and Yields-Based and Congener-Based PCB Site Prioritization Methodologies

San Francisco Estuary Institute (SFEI) | January 12th, 2022

With RMP funding allocated in 2017 and 2018, a pilot study was completed using a subset of data from watersheds in San Mateo and Santa Clara Counties to build new methods

With RMP funding allocated in 2017 and 2018, a pilot study was completed using a subset of data from watersheds in San Mateo and Santa Clara Counties to build new methods for organizing and analyzing the existing stormwater reconnaissance data that will provide further evidence to support decisions about which watersheds may be of interest for prioritized management focus. The pilot study resulted in two new analysis methodologies outlined in two companion reports: Davis, J.A. and Gilbreath, A.N., 2019. Small Tributaries Pollutants of Concern Reconnaissance Monitoring: Pilot Evaluation of Source Areas Using PCB Congener Data. SFEI Contribution No. 956. San Francisco Estuary Institute, Richmond, California. McKee, L.J., Gilbreath, A.N., Hunt, J.A., Wu, J., Yee, D., and Davis, J.A., 2019. Small tributaries pollutants of concern reconnaissance monitoring: Loads and yields-based prioritization methodology pilot study. SFEI Contribution No. 817. San Francisco Estuary Institute, Richmond, California. In this final report, we describe a few enhancements to the storm-event loads and yields method and then apply both methods to a much larger data set and provide the resulting database to support stormwater management and decision making.

Small Tributaries Pollutants of Concern Reconnaissance Monitoring: Loads and Yields-based Prioritization Methodology Pilot Study

San Francisco Estuary Institute (SFEI) | October 1st, 2019

Watershed yields (mass exported per unit watershed area) can be used as an indicator variable to help identify watersheds or source areas of higher management interest i

Watershed yields (mass exported per unit watershed area) can be used as an indicator variable to help identify watersheds or source areas of higher management interest in relation to mass loads that impact the Bay. When prioritization includes an analysis of uncertainty, a recommendation can also be made for priority investigations necessary to reduce uncertainties. A method is presented for generating comparable yield estimates for small industrial watersheds where only a single storm has been sampled and for which a watershed boundary has been generated. The method generates standardized storm-based yields for each sampled site for a 0.5-year annual return frequency storm with 2-hour peak rainfall intensity. No attempt has been made to estimate annual average yields (the metric upon which the TMDL was based).

Small Tributaries Pollutants of Concern Reconnaissance Monitoring: Pilot Evaluation of Source Areas Using PCB Congener Data

San Francisco Estuary Institute (SFEI) | October 1st, 2019

PCB congener profiles can be used to help identify source areas that contribute most to the PCB mass exported from the watershed via stormwater and to illustrate variabi

PCB congener profiles can be used to help identify source areas that contribute most to the PCB mass exported from the watershed via stormwater and to illustrate variability in PCB mobilization from source areas over time. A method is presented for estimating the contributions of different Aroclor mixtures to the congener profiles of samples of stormwater and sediment. The method is based on the use of indicator congeners that are representative of each of the four most commonly used Aroclors. In this report, the method was applied in three watersheds. In the Pulgas Pump Station watershed, stormwater and sediment had high concentrations with a unique congener profile, dominated by congeners indicative of a combination of Aroclors 1242 and 1260. The concentrations and congener profiles in sediment suggest that there are two distinct source areas in the watershed that combine to create the mix of 1242 and 1260 that is dominant in stormwater at the Pump Station. The data indicate that if PCB flux from one of these areas could be eliminated, loads from the watershed would be reduced by 50% or more. For the Coyote Creek watershed, the similarity in congener profiles for the highest concentration sediment samples and the stormwater samples suggest that the important source areas in the watershed have been identified, and that reduction of loading from an area at the south end of the Charcot Avenue Storm Drain watershed would yield the greatest reduction in export at the Coyote Creek station. The concentrations and congener profiles in stormwater and sediment from the Guadalupe River watershed indicate the presence of one source area that is likely a substantial contributor to PCB export from the watershed, but that all of the significant sources areas may not yet have been identified.

Smartphone-based turbidity reader

Nature Portfolio (Springer Nature) | December 27th, 2019

Water quality is undergoing significant deterioration due to bacteria, pollutants and other harmful particles, damaging aquatic life and lowering the quality of d

Water quality is undergoing significant deterioration due to bacteria, pollutants and other harmful particles, damaging aquatic life and lowering the quality of drinking water. It is, therefore, important to be able to rapidly and accurately measure water quality in a cost-effective manner using e.g., a turbidimeter. Turbidimeters typically use different illumination angles to measure the scattering and transmittance of light through a sample and translate these readings into a measurement based on the standard nephelometric turbidity unit (NTU). Traditional turbidimeters have high sensitivity and specificity, but they are not field-portable and require electricity to operate in field settings. Here we present a field-portable and cost effective turbidimeter that is based on a smartphone. This mobile turbidimeter contains an opto-mechanical attachment coupled to the rear camera of the smartphone, which contains two white light-emitting-diodes to illuminate the water sample, optical fibers to transmit the light collected from the sample to the camera, an external lens for image formation, and diffusers for uniform illumination of the sample. Including the smartphone, this cost-effective device weighs only ~350 g. In our mobile turbidimeter design, we combined two illumination approaches: transmittance, in which the optical fibers were placed directly below the sample cuvette at 180° with respect to the light source, and nephelometry in which the optical fibers were placed on the sides of the sample cuvette at a 90° angle with respect to the to the light source. Images of the end facets of these fiber optic cables were captured using the smart phone and processed using a custom written image processing algorithm to automatically quantify the turbidity of each sample. Using transmittance and nephelometric readings, our mobile turbidimeter achieved accurate measurements over a large dynamic range, from 0.3 NTU to 2000 NTU. The accurate performance of our smartphone-based turbidimeter was also confirmed with various water samples collected in Los Angeles (USA), bacteria spiked water samples, as well as diesel fuel contaminated water samples. Having a detection limit of ~0.3 NTU, this cost-effective smartphone-based turbidimeter can be a useful analytical tool for screening of water quality in resource limited settings.

Social Disparities in Nitrate-Contaminated Drinking Water in California’s San Joaquin Valley

National Institutes of Health (NIH) | September 1st, 2011

Source area management practices as remediation tool to address groundwater nitrate pollution in drinking supply wells

Journal of Contaminant Hydrology (Elsevier) | July 19th, 2019

Nitrate in drinking water may cause serious health problems for consumers. Agricultural activities are known to be the main source of groundwater nitrate contaminating ru

Nitrate in drinking water may cause serious health problems for consumers. Agricultural activities are known to be the main source of groundwater nitrate contaminating rural domestic and urban public water supply wells in farming regions. Management practices have been proposed to reduce the amount of nitrate in groundwater, including improved nutrient management practices and “pump and fertilize” with nitrate-affected irrigation wells. Here, we evaluate the feasibility and long-term impacts of agricultural managed aquifer recharge (Ag-MAR) in the source area of public water supply wells. A numerical model of nitrate fate and transport was developed for the Modesto basin, part of California's Central Valley aquifer system. The basin is representative of semi-arid agricultural regions around the world with a diversity of crop types, overlying an unconsolidated sedimentary aquifer system. A local public supply well in an economically disadvantaged community surrounded by farmland was the focus of this study. Model scenarios implemented include business as usual, alternative low-impact crops, and Ag-MAR in the source area of the public supply well. Alternative nutrient management and recharge practices act as remediation tools in the area between farmland and the public supply well. Improved agricultural source area management practices are shown to be an effective tool to maintain or even enhance groundwater quality in the targeted supply well while remediating ambient groundwater.

Source, movement and age of groundwater in the upper part of the Mojave River Basin, California, USA

Proceedings of the 1994 International Symposium on Application of Tracers in Arid Zone Hydrology | August 22nd, 1996

Water samples from wells were collected and analysed for oxygen-18, deuterium, tritium, carbon-14, and carbon-13 to determine the source, movement and age of groundwate

Water samples from wells were collected and analysed for oxygen-18, deuterium, tritium, carbon-14, and carbon-13 to determine the source, movement and age of groundwater in the upper part of the Mojave River basin. Water in the alluvial aquifer has a median deuterium composition of — 66% and contains tritium, and was recently recharged by water from the Mojave River. Water in the regional aquifer near the Mojave River, near Summit Valley, and underlying several small washes has deuterium compositions heavier than — 60 %. Although some water in the regional aquifer near the Mojave River contains tritium, most of this water does not contain tritium. Carbon-14 data indicate that this water was recharged less than 2400 years ago. Water in the remainder of the regional aquifer has a median deuterium composition of — 84 %, which is as much as 20 % lighter than the volume-weighted deuterium composition of present-day precipitation. These data show that this water was recharged under climatic conditions different from average conditions today. Carbon-14 data indicate that some water in the regional aquifer was recharged more than 20,000 years ago.

Sources of high-chloride water and managed aquifer recharge in an alluvial aquifer in California, USA

Hydrogeology Journal (Springer) | July 3rd, 2015