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Hydraulic jacking is a serious threat to concrete spillway chutes, demonstrated by the catastrophic spillway chute failure at California's Oroville Dam in 2017. To improve the understanding of uplift pressure and joint flow developed at open, offset joints and enable design and evaluation of anchors, drain systems, and joint remediations that could help prevent such failures, laboratory tests were performed in a supercritical flume furnished with a model joint where the gap width to offset height ratio was varied over a 725∶1 range. The tests included measurement of boundary layer velocity profiles approaching the joint. Uplift pressures were normalized to the velocity head near the boundary, which is related to the depth-wise velocity profile exponents determined in the experiments and can be estimated for field applications from the chute friction factor. The normalized uplift varies with the joint aspect ratio and the flow depth to offset height ratio. The new relations reduce the uncertainty of modeled uplift pressures by a factor of 2.87 over previous methods. Example applications demonstrate practical upper limits for potential uplift pressure. Subsequent articles will address discharge into offset joints, the dissipation of uplift via drainage, and the effect of different methods for remediating existing offsets to reduce uplift. Practical Applications: Concrete spillway chutes develop cracks and must necessarily be constructed with joints, both of which are prone to displacement over time that may create offsets into the flow. Flow striking such offsets is brought suddenly to rest, similar to a pedestrian tripping on a sidewalk crack. The local stoppage of flow at the offset creates dangerously high pressures that can be injected into the foundation, leading to erosion beneath the slab and potential uplift failure, often called 'hydraulic jacking'. This mechanism has caused several notable failures including the Oroville Dam spillway in 2017. Protection against such failures is usually provided by a combination of the weight (thickness) of the slab itself, anchors that hold the slab down, and subsurface drains that reduce the buildup of pressure. This paper provides experimentally based equations for predicting uplift pressure to enable effective design of new spillways and evaluation of existing spillways. The new equations are significantly more accurate than previous methods because they account for the roughness of the chute surface and the reduced flow velocity near the boundary. Subsequent papers will address flow rate through joints, pressure dissipation by drainage, and methods for treating existing offsets to reduce potential uplift. [ABSTRACT FROM AUTHOR]

Communities in the U.S. fund stormwater management programs to reduce flooding and improve and protect water quality. Few studies have attempted to quantify municipal storwmater management expenditures. This task is important given efforts to meet increasing water quality standards and develop new revenue sources. The purpose of this study was to evaluate trends in municipal stormwater management expenditures across the state of California. The study identified and compiled publicly-available data on reported stormwater expenditures (spending) and budgets for local governments in California. Data were extracted from annual reports for over 160 public agencies. A standardized rubric of activities was developed and used to create a first-of-its-kind database of municipal stormwater budgets and expenditures. The results indicated that there is over $700 million in annual municipal stormwater spending, but this total does not represent all spending due to gaps in publicly-available data. Counties and flood control districts often have the largest total expenditures in a region, but in aggregate cities reported more spending statewide. Available data are not sufficient to adequately evaluate whether current spending meets regulatory requirements. Additionally, publicly-available data are inconsistent across geographic regions regulated by different agencies. The analysis offers a template for improved cost reporting of stormwater programs in U.S. municipalities, which can help answer key questions such as the sufficiency of current funding. Future research can use the method to evaluate spending in other states and regions, evaluate trends over time to improve outcomes, and refine the spending categories based on examples from other states. [ABSTRACT FROM AUTHOR]

Soils in the San Joaquin Valley of California have been a source of selenium (Se) release through dissolution into agricultural drainage, requiring treatment before discharge to the environment. A full-scale primarily anaerobic, granular activated-carbon (GAC) bioreactor with an empty bed contact time ranging from 3.4 to 5.0 h was fed 757 L/min of second-pass agricultural drainage water (ADW) at the San Luis Demonstration Treatment Plant (SLDTP) in Firebaugh, California, for 1,062 days. This study summarized startup of an actual water treatment plant with a process scheme that had never been designed or operated at this scale. ADW nitrate (NO3−) and dissolved oxygen (O2(aq)) concentrations largely dictated the externally dosed carbon (EDC), or glycerin dose, which served as the electron donor to achieve selenate (SeO42−) reduction to elemental Se (Se0). Total Se (SeT) influent concentrations between 111 and 332 μg/L were treated to average effluent SeT concentrations of 7.4 μg/L across the bioreactor. Bioreactor effluent SeT concentrations were further reduced across a downstream ultrafiltration membrane system (UFMS) to an average permeate SeT concentration of 2.9 μg/L. It was determined that most of the SeT removed from the ADW was retained on the bioreactor GAC and was not amenable to removal through backwashing, rendering it hazardous waste by both California and federal standards. Removal of other trace metals such as chromium and uranium were investigated. [ABSTRACT FROM AUTHOR]