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San Francisco, CA, United States

The San Francisco Public Utilities Commission is a public agency of the City and County of San Francisco that provides water, wastewater, and electric power services to the city and an additional 1.6 million customers within three San Francisco Bay Area counties. Since its creation in February 2005, the SFPUC Power Enterprise Division has supplied power to many city facilities including Muni, San Francisco International Airport as well as the Modesto and Turlock Irrigation districts.The SFPUC is also the water, electricity and wastewater utility for occupants of Treasure Island and Yerba Buena Island. The SFPUC manages a complex water supply system consisting of reservoirs, tunnels, pipelines and treatment facilities and is the third largest municipal utility agency in California. The SFPUC protects its watershed properties with security utility trucks and fire apparatus painted white over green. The SFPUC provides fresh water from Hetch Hetchy Reservoir to 2.4 million customers for residential, commercial and industrial uses. Near one-third of its delivered water is sent to customers within San Francisco, while the remaining two-thirds is sent to Alameda, San Mateo, and Santa Clara counties. Aside from delivering water, the agency is also responsible for treating wastewater before discharging it into the San Francisco Bay and the Pacific Ocean. Wikipedia.

Sayama T.,Public works research institute | Mcdonnell J.J.,Oregon State University | Mcdonnell J.J.,University of Aberdeen | Dhakal A.,San Francisco Public Utilities Commission | Sullivan K.,Humboldt Redwood Company
Hydrological Processes

Subsurface runoff dominates the hydrology of many steep humid regions, and yet the basic elements of water collection, storage, and discharge are still poorly understood at the watershed scale. Here, we use exceptionally dense rainfall and runoff records from two Northern California watersheds (~100km2) with distinct wet and dry seasons to ask the simple question: how much water can a watershed store? Stream hydrographs from 17 sub-watersheds through the wet season are used to answer this question where we use a simple water balance analysis to estimate watershed storage changes during a rainy season (dV). Our findings suggest a pronounced storage limit and then 'storage excess' pattern; i.e. the watersheds store significant amounts of rainfall with little corresponding runoff in the beginning of the wet season and then release considerably more water to the streams after they reach and exceed their storage capacities. The amount of rainfall required to fill the storages at our study watersheds is the order of a few hundred millimeters (200-500mm). For each sub-watershed, we calculated a variety of topographic indices and regressed these against maximum dV. Among various indices, median gradient showed the strongest control on dV where watershed median slope angle was positively related to the maximum volume of storage change. We explain this using a hydrologically active bedrock hypothesis whereby the amount of water a watershed can store is influenced by filling of unrequited storage in bedrock. The amount of water required to activate rapid rainfall-runoff response is larger for steeper watersheds where the more restricted expansion of seepage from bedrock to the soil limits the connectivity between stored water and stream runoff. © 2011 John Wiley & Sons, Ltd. Source

Downs P.W.,University of Plymouth | Dusterhoff S.R.,Stillwater science | Sears W.A.,Stillwater science | Sears W.A.,San Francisco Public Utilities Commission

Understanding the cumulative impact of natural and human influences on the sensitivity of channel morphodynamics, a relative measure between the drivers for change and the magnitude of channel response, requires an approach that accommodates spatial and temporal variability in the suite of primary stressors. Multiple historical data sources were assembled to provide a reach-scale analysis of the lower Santa Clara River (LSCR) in Ventura County, California, USA. Sediment supply is naturally high due to tectonic activity, earthquake-generated landslides, wildfires, and high magnitude flow events during El Niño years. Somewhat typically for the region, the catchment has been subject to four reasonably distinct land use and resource management combinations since European-American settlement. When combined with analysis of channel morphological response (quantifiable since ca. 1930), reach-scale and temporal differences in channel sensitivity become apparent. Downstream reaches have incised on average 2.4. m and become narrower by almost 50% with changes focused in a period of highly sensitive response after about 1950 followed by forced insensitivity caused by structural flood embankments and a significant grade control structure. In contrast, the middle reaches have been responsive but are morphologically resilient, and the upstream reaches show a mildly sensitive aggradational trend. Superimposing the natural and human drivers for change reveals that large scale stressors (related to ranching and irrigation) have been replaced over time by a suite of stressors operating at multiple spatial scales. Lower reaches have been sensitive primarily to 'local' scale impacts (urban growth, flood control, and aggregate mining) whereas, upstream, catchment-scale influences still prevail (including flow regulation and climate-driven sediment supply factors). These factors illustrate the complexity inherent to cumulative impact assessment in fluvial systems, provide evidence for a distinct Anthropocene fluvial response, and underpin the enormity of the challenge faced in trying to sustainably manage and restore rivers. © 2013 Elsevier B.V. Source

Dhakal A.S.,Humboldt Redwood Company Formerly Scotia Pacific Company | Dhakal A.S.,San Francisco Public Utilities Commission | Sullivan K.,Humboldt Redwood Company Formerly Scotia Pacific Company | Sullivan K.,U.S. Environmental Protection Agency
Hydrological Processes

The pore water pressure head that builds in the soil during storms is a critical factor for the prediction of potential slope instability. We report findings from a 3-year study of pressure head in 83 piezometers distributed within a 13-ha forested catchment on the northern coast of California. The study's primary objective was to observe the seasonal and storm-based dynamics of pressure head at a catchment scale in relation to observed rainfall characteristics and in situ topography to better understand landscape patterns of pressure head. An additional goal was to determine the influence of the interaction between rainfall and forest canopy in altering delivery of water and pressure head during the large storms necessary to induce landsliding. We found that pressure head was highly variable in space and time at the catchment scale. Pore pressures peaked close to maximum rainfall intensity during the largest storms measured. The difference between rainfall and throughfall delivered through the canopy was negligible during the critical landslide-producing peak rainfall periods. Pore pressure was spatially variable within the catchment and did not strongly correlate with surficial topographic features. Only 23% of the piezometers located in a variety of slope positions were found to be highly responsive to rainfall. Topographic index statistically explained peak pressure head at responsive locations during common storms, but not during the larger storms with potential to produce landslides. Drainage efficiency throughout the catchment increased significantly in storms exceeding 2 to 7months peak pressure head return period indicated by slowing or cessation of the rate of increase of pressure head with increasing storm magnitude. This asymptotic piezometric pattern persisted through the largest storm measured during the study. Faster soil drainage suppressed pressure head response in larger storms with important process implications for pore pressure development and landslide hazard modelling. © 2012 John Wiley & Sons, Ltd. Source

Miot A.,San Francisco Public Utilities Commission | Pagilla K.R.,Illinois Institute of Technology
Water Environment Research

This research identified suitable conditions for long-term inhibition of nitrite-oxidizer bacteria (NOB) in a sequencing batch reactor for the treatment of centrate by over-nitrite pathways. The NOB were inhibited by free ammonia concentrations greater than 20 mg NH 3-N/L combined with a dissolved oxygen concentration less than 0.3 mg O 2/L and a temperature of 30®C. The experiments were performed in a laboratory-scale 2.5-L reactor fed with synthetic and actual centrate from a full-scale wastewater treatment plant (800 to 1500 mg NH 4 +-N/L). The influence of influent-alkalinity-to-ammonium ratio (AAR) on the effluentnitrite-to-ammonium ratio (NAR) also was investigated. The control of the effluent NAR was possible by adjusting the influent AAR when NOB inhibition was maintained and when total alkalinity depletion took place before the end of the cycle. The maximum nitritation rate of 860 mg NO 2 --N oxidized/L·d was obtained when the influent NH 4 +-N concentration was 800 mg NH 4 +-N/L and the hydraulic retention time was 1.7 days. © 2010 Publishing Technology. Source

Labonte J.L.,San Francisco Public Utilities Commission
Journal - American Water Works Association

The article describes how the San Francisco Bay Area has embarked on a monumental upgrade to regional water system to prevent severe water infrastructure damage from an earth quake of magnitude 6.7 or greater. With the level of funding involved in large infrastructure projects, politics as well as social and economic factors in a community can often influence how projects are delivered. In 2008, the US Geologic Survey estimated the overall probability of magnitude 6.7 or greater earthquake in the greater San Francisco Bay Area to be 63%. Although no seismic expert can predict exactly when the next big one will strike the Bay Area, everyone agrees that it is only a matter of time. For many, compliance with newly promulgated and anticipated federal and state mandates for higher environmental and water quality standards will not be possible without some infrastructure improvements. Source

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