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The proposed 110-million-gallon reinforced concrete Headworks Reservoir structures are planned by the Los Angeles Department of Water and Power (LADWP) to be part of the water supply system of the City of Los Angeles, and resilience of the water supply system is crucial for continued water supply in the event of a disaster, such as an earthquake. The seismic resilience of the reservoir structure is a function of the cracking and associated leakage that would be expected due to static loading and during the design level earthquake. Evaluation of the seismic deformation of the structure was accomplished utilizing a soil-structure interaction (SSI) model to evaluate performance of the reservoir structure in an earthquake, after the initial design based on standard code-based design procedures. SSI was used to provide information on the structural behavior of the reservoir, and to understand relative movement of inlet and outlet pipelines. In addition, a leak detection system was incorporated into the design. PROJECT DESCRIPTION AND GEOLOGY The proposed Silver Lake Complex Replacement Project consists of the Headworks Reservoir Complex (East and West Reservoirs), a Hydropower Plant to be constructed on approximately 12 acres within the Headworks Spreading Grounds, and a series of new water conveyance pipelines to and around the existing Silver Lake Reservoir (not at the location of the proposed reservoir site). The current proposed location of the reservoir complex including major project components planned are

Coastcare is Yorkshire Water's £120 million coastal waste-water treatment improvement programme. It involves installing modern treatment plants to serve the popular east coast resorts of Scarborough, Filey, Whitby, Bridlington, Hornsea, Staithes, Robin Hood's Bay, Sandsend and Runswick Bay. Developed in close consultation with the local communities, the programme takes account of potential future changes in legislation. It thus moves away from the old solution of long sea outfalls towards inland treatment technologies, including UV disinfection.

A two-year pilot study involving the recharge of a ground water basin with reclaimed water was completed in the city of Los Angeles. The city's Department of Water and Power is planning to initiate several ground water recharge projects using reclaimed water in the near future. One such project is the Headworks Recharge Project, the focus of this paper, Approximately 1 cfs of the Los Angeles (LA) River water comprised of 70% tertiary treated reclaimed water was recharged on a two-day wet and five-day dry cycle. The recharge water was then extracted from the basin approximately 1000 feet downgradient. Results showed greater than 4-log removal of coliform bacteria, up to 87% reduction in TOC, and compliance of the product water with federal and state drinking water standards. Model simulation showed after 15 years of recharging 3000 acre-feet per year of the LA River water and extracting about 10,000 acre-feet from the basin, the product water would contain from 5% to 15% reclaimed water. This is well below the maximum allowable limit of 20% stipulated by the California regulation.

The Leon Creek Water Recycling Center (WRC) and Dos Rios WRC facilities, owned and operated by the San Antonio Water System (SAWS), treat the majority of wastewater produced by the City of San Antonio. The Leon Creek WRC Interconnect Project (the “Interconnect”) has been planned to allow for the diversion of flows of up to 51-MGD through a new 60-inch pipeline that connects to the new Southwest Bexar Sewer Pipeline (SBSP), which ultimately ties in at the Dos Rios WRC headworks. This project will delay the need for further expansion of the Leon Creek WRC while maximizing SAWS’ current investment in the expansion and rerating of the Dos Rios WRC from 125-MGD to 217-MGD. This project also allows SAWS to shift more of the raw wastewater supply to the Dos Rios WRC, which services the leg of the recycled water system with the highest demand. In 2010, SAWS contracted with CP&Y, Inc. to study and design the Interconnect. PURPOSE The Leon Creek WRC Interconnect to the SBSP consists of the design and construction of approximately 9,350 LF of 60-inch gravity sanitary sewer line that will convey peak flows from the Leon Creek WRC to a tie-in point along the 96-inch SBSP at the Toyota Manufacturing Facility site. The Interconnect will allow the Leon Creek WRC to continue treating flows from the Western Sewershed, up to its existing capacity of 46-MGD average daily flow (ADF) and peak 2-hour flows (P2HF), of 92-MGD. The Interconnect will delay the need for further expansion of the Leon Creek WRC, which is currently required to convey peak flows by diverting peak flows and future flows generated by a growing upstream system to the Dos Rios WRC. The Dos Rios WRC is currently undergoing a phased re-rating, which will allow the Dos Rios WRC to continue providing treatment for the Central and Eastern Sewersheds while handling flows from the Western, Far West, and South Sewersheds. The proposed Interconnect will allow SAWS to maximize the treatment

Digital ground penetrating radar (GPR) was used to detect and measure the displacement of the Wasatch fault zone at Brigham City, Utah. Optimum radar results were obtained from clean, fluvial-deltaic sand and gravel (quartz-rich) of the late Pleistocene, Lake Bonneville, Box Elder Creek delta (Provo level), which straddles the fault. From the north side of the Box Elder Creek delta, results clearly show three vertically-stacked radar facies of subsurface lithofacies; the middle and lower facies are displaced 7 to 8 m in post-Provo (14,000 years) and pre-Provo-aged sediments of Lake Bonneville. The upper radar facies of continuous broad concave reflections represent post-fault, slope-wash sediment eroded from the upthrown block which infilled the graben on the downthrown side. Two micro faults are also present. Less promising GPR surveys were conducted in and along several stream beds of the Weber River at Ogden, Little Cottonwood Creek at Sandy, American Fork River near Lehi, and Spanish Fork River near Spanish Fork. The main problem in the Wasatch fault zone was the large amount of human disturbance (highways, dams, hydroelectric turbines, high voltage powerlines, pipelines, irrigation headworks, buildings and access problems) near the mouths of mountain canyons where streams cross the fault. Many of these features cause severe noise problems especially with unshielded antennae.

[1] The issue of drought security is of paramount importance for cities located in regions subject to severe prolonged droughts. The prospect of “running out of water” for an extended period would threaten the very existence of the city. Managing drought security for an urban water supply is a complex task involving trade-offs between conflicting objectives. In this paper a multiobjective optimization approach for urban water resource planning and operation is developed to overcome practically significant shortcomings identified in previous work. A case study based on the headworks system for Sydney (Australia) demonstrates the approach and highlights the potentially serious shortcomings of Pareto optimal solutions conditioned on short climate records, incomplete decision spaces, and constraints to which system response is sensitive. Where high levels of drought security are required, optimal solutions conditioned on short climate records are flawed. Our approach addresses drought security explicitly by identifying approximate optimal solutions in which the system does not “run dry” in severe droughts with expected return periods up to a nominated (typically large) value. In addition, it is shown that failure to optimize the full mix of interacting operational and infrastructure decisions and to explore the trade-offs associated with sensitive constraints can lead to significantly more costly solutions.

A significant feature of Pakistan's agriculture is that it is served by the Indus irrigation system, which is one of the largest contiguous irrigation systems in the world. The system comprises of the Indus River and its tributaries, three major storage reservoirs, 19 barrages/headworks, 43 canals, and 12 link canals and 43 canals covering about 43,000 chaks or village settlements. The total length of the canal system is about 40,000 miles with over 80,000 water courses, field channels and ditches running for another million miles. About 100-106 million acre feet (MAP) of surface irrigation supplies are diverted annually into the canal system. Only 60 percent of this water reaches the farmgate due mainly to low efficiency in the delivery of water. The historical review of the area, production and yield trends shows that agricultural production in the past has increased mainly due to expansion in irrigated acreage while the contribution of changes in yields has been insignificant. In general, agricultural production can be increased by either expanding the irrigated cropped area or by raising the crop yields. It is highly unlikely that Pakistan will be able to satisfy the food needs of the rapidly increasing population through yield increases alone. This means that there ia a need to increase the irrigated cropped area through additional water supplies and by improving the efficiency of water use through using the water resources in a scientific manner. The possibilities of increasing irrigated area by developing more land and new surface water supplies in the short-run are limited as it requires huge capital

Sediment entry into irrigation and hydropower canals may be controlled by a sediment excluder at canal headworks and/or a sediment ejector on the canal downstream of headworks. These devices take advantage of the fact that the bed-load part of transported sediment in a stream moves near the bed and the suspended-load part is distributed nonuniformly in a vertical column, with heavier concentrations near bed. The sediment ejector consists of a horizontal diaphragm slab, positioned slightly above the canal bed, and of ducts below the diaphragm flush the heavy sediment-laden water into an escape channel. The present study concerns determination of diaphragm height of the ejector for uniform sediment, based on principles of sediment transportation. The diaphragm height should be such that suspended sediment load in the canal approaching the ejector above the diaphragm level should be equal to the total sediment transport capacity of the canal downstream of it. A correction factor is suggested to account for the effect of flow disturbance at the nose of the ejector. A design example has been worked out.

There is a class of water supply headworks models that uses network linear programming to assign water within the network. The choice of algorithm and computer code to solve the network linear programs formulated by such models becomes important when doing planning studies that may involve thousands of replicates of future stream-flow and demand conditions. The computational performance of two public-domain FORTRAN codes, NETFLO and RELAX, representing efficient implementations of the primal-simplex and primal-dual algorithms, were compared for two headworks systems. The results showed that for the two small network linear programs typical of headworks modeling, the RELAX code used without prior flow information was about 100% faster than the NETFLO code. When prior flow information was employed further substantial gains in speed were realized. The second and subsequent iterations within a time step were solved in about one-third of the time for the first iteration. The actual overall speed gain depends on whether the prior information is used across time steps or just between the iterations in a time step.

Northumbrian Water Limited has thirty-four bathing waters and a substantial investment programme to ensure that these waters meet EC standards by 1995. One project within this overall programme is the Seaton Carew Sewerage Scheme. Seaton Carew lies on the southern edge of Hartlepool which has a population of 95000. The scheme will combine existing flows into new foul and storm-sewage outfalls. The headworks will incorporate screening, grit removal and pumping stations with substantial measures for odour control. Hydraulic operating regimes using active pump control and passive flume control have been investigated to ensure efficient treatment for a wide range of flows. The onerous design, manufacture and construction programme has required the development of new approaches to procuring the work, whilst maintaining a substantial element of competition. The various programmes have been substantially overlapped to ensure that the scheme is completed by April 1993.

Simulation is used to evaluate the future performance of water supply headworks systems. Typically, most of the uncertainties associated with the use of demand models are ignored in the simulation. A simulation methodology is presented which makes allowance for the uncertainties associated with the use of demand and streamflow models. The demand uncertainties considered are natural, climatic, socioeconomic, and model parameter uncertainty. The methodology is illustrated using two case studies which consider a simple stationary demand model and the widely used trend extrapolation demand model. The results show that ignoring demand uncertainties (as well as streamflow model parameter uncertainty) can significantly bias the expected reliability. This bias depends on the magnitude of demand uncertainty which in turn depends on model structure, length of data available for calibration, and uncertainty in future socioeconomic variables. Moreover, this bias tends to increase as streamflow variability decreases. To guard against overoptimistic assessment of system performance, it is suggested that allowance be made for demand uncertainty (as well as streamflow model parameter uncertainty) in headworks simulation.

Often the design, permitting, construction and startup of an in-situ mechanical device in wastewater open channels is not the hardest task — demonstrating its performance against very stringent criteria after installation is a major challenge and may require a very creative design and delivery approach of its own. Most grit removal systems are not tested after installation and if there is a problem, operators find out only after the system breaks down or large quantities of grit are deposited in systems downstream of the grit removal process, affecting the entire wastewater treatment plant. In most instances these deficiencies cannot be rectified until the entire headworks is up for redesign. As a result of unreliable performance of prior (often conventional style) grit removal systems, some municipalities and clients are requesting that the efficacy of new, proprietary grit removal systems be proven either before they are installed or after installation. The testing usually consists of lab testing, pilot testing, field verification or a combination of these. A system that is unable to meet the treatment goals is either replaced or modified, usually at a cost to the supplier. This paper describes the test methods and sampling procedures used to evaluate two grit removal systems installed at two treatment plants in Clearwater, Florida. The work includes pilot testing for assessing the gradation of the incoming grit and in-situ device verification after the installation of the full-scale unit. The results from the testing indicate that using a multi-pronged approach to characterize grit and size treatment systems is an effective way of ensuring that the installed system is capable of meeting the design goals. The paper recommends adopting this test methodology for assessing installed grit removal systems.

Many studies have been carried out regarding the development of optimum operating policies for multiple reservoir systems but few of these have considered water quality as an objective. This study considers operations of the headworks system for Adelaide, Australia. The system is rather unusual because of its high salt concentrations which impose large economic costs on the consumers. In addition, a significant fraction of the supply is pumped from a distant river. An existing linear programming model for operation of the Adelaide system is modified to identify policies which minimize total system costs (including salt damage costs). These changed procedures can reduce the average salinity of the supplied water significantly but at some increase in annual pumping costs. The benefit-cost ratio of the changes is estimated to be 3.0 for the entire system.

A water supply headworks simulation software package called WATHNET is described. It uses a simulation model based on a network linear programming formulation which makes the model independent of system configuration, avoids the need to define detailed operating rules, and allows simulation of systems changing over time. Particular emphasis is given to describing the user environment which consists of a portable, mouse-based graphics interface and the tools to which it provides access. This environment helps realize the potential of the model, providing tools which streamline the complex task of system definition and data preparation, and which present results in a readily comprehended form. A case study is used to illustrate significant features.

Urban water supply headworks systems are usually designed to provide high security against drought. The best way to evaluate this security is to use Monte Carlo simulation which is computationally expensive. The advent of parallel computing technology in conjunction with genetic algorithms (GAs) has made it practicable to optimize operation for drought security. Nonetheless, computation turnaround times remain long. This paper presents a simple heuristic called replicate compression to improve Monte Carlo efficiency. It exploits the well known concept of a critical period. In a high reliability system there should be few critical periods. Therefore, restricting simulation to such periods should bring about substantial savings in computational effort. It was found for problems where the objective function evaluation is only affected by what happens during critical periods, replicate compression provides an effective means for substantially reducing simulation effort. The case study involving a nine-reservoir urban headworks system showed the actual reduction in effort depended on the stress experienced by the system, which in turn affected the frequency of critical periods. Even when the objective function is affected by decisions outside the critical period, replicate compression may provide a useful result by helping to guide the specification of a reduced search space for the genetic algorithm. This strategy can bring about substantial savings in turnaround time.

The paper describes the design and construction of a comprehensive drainage scheme which is based on a system of intercepting sewers, headworks, and a long sea outfall. Details are given of the fabrication, discharge arrangements and construction of the outfall, together with measures used for long-term protection of the pipeline. The layout and design of the headworks and the changes made to the original design to meet changing environmental requirements are given. The paper briefly outlines the existing sewerage system and goes on to describe the proposed interceptor sewerage system for the connection of the flow from the existing outfalls to the headworks. Difficulties encountered in construction are highlighted. The authors indicate their view on the suitability of the present design, and recognition is given to the likelihood that additional facilities may be required in future. The difficulties which could arise in the provision of such facilities are also highlighted.

In the presence of conveyance losses, the efficient quantity of water applied falls with distance from the water source, but the amount of water "sent" (including conveyance losses) actually increases with distance from the source, except toward the tail end of the inigation system. This implies that if marginal cost pricing were implemented, farmers at the middle and lower reaches of the system would have to pay more money for less water received. The model is illustrated and alternative financing schemes compared for an empirically derived demand function for imgation water. Despite massive public investments in irrigation infrastructure, ex post evaluations of irrigation projects in developed and developing countries indicate that actual benefits are substantially below projected levels. Considerable evidence suggests that these low benefits are largely the result of poor on-farm water use efficiencies and rent-seeking activities that result from water charges that are low and often unrelated to water use (Chaudhry, Repetto, Bowen and Young). For example, farmers near the system headworks are said to consume a disproportionate share of irrigation water, while tail farmers are left with scanty and unreliable residual supplies (Reidinger, Wade). Many governments, faced with increasing political pressure to conserve water and reduce fiscal deficits are considering higher water charges to decrease waste and increase cost recovery from project beneficiaries. There is also increased awareness that low water charges and loosely enforced water rationing guidelines lead to environmental damages and excessive mining of groundwater resources. In general, the problems of water allocation and low user charges contribute to derivative problems in achieving efficiency, equity, fiscal stability, and environmental sustainability.

The Calgary Bow River Weir Project is intended to remove an existing safety hazard created by an ogee weir, while maintaining the weir’s ability to divert water for irrigation and not increasing upstream flood levels. The river reach downstream of the weir will be transformed into a high water channel and a low water channel, each comprised of multiple pool-and-drop features to provide recreational opportunities for boaters and improve fish passage at the site. Computational fluid dynamics models were developed to evaluate hydraulic conditions of design modifications to HWC Drop #1. In this study, a volume-of-fluid (VOF) model was employed to predict the water surface profile and to assess whether a hydraulic jump would form downstream of the drop structure. The CFD models were validated by comparing CFD results with qualitative and quantitative data collected in the physical models. The comparisons indicated that the CFD models were able to correctly predict hydraulic jump formation immediately downstream of the weir for the existing design, and demonstrated satisfactory hydraulic conditions for the proposed design at flows at which boat passage is expected to occur. This study demonstrated that CFD modeling is a viable tool for predicting flows involving highly deformed water surfaces, such as those associated with hydraulic jumps. Introduction The existing Western Headworks diversion weir (Calgary Weir), located on the Bow River within the City of Calgary, was constructed in 1975 and is operated by Alberta Environment for the purpose of supplying water to the Western Irrigation District (WID). The weir is located within the Inglewood District, adjacent to Pearce Estate Park on the right bank and Deerfoot Trail on the left bank. Left or right refer to directions as seen by an observer looking downstream. A Canadian Pacific Railway World Environmental and Water Resources Congress 2008 Ahupua'a © 2008 ASCE Copyright ASCE 2008 World Environmental and Water Resources Congress 2008: Ahupua'a 2 (CPR) bridge crossing is located approximately 350 m upstream from the weir and Cushing Bridge (17 Avenue) is located approximately 900 m downstream. The headworks facility includes the WID canal intake structure, a three-bay gated sluiceway, a fish ladder and the diversion weir, as shown in Photo 1. a) View looking north (flow is from left to right) b) View looking upstream (CPR bridge and downtown Calgary in background) Photo 1: Calgary Weir on Bow River – Existing Site Although the weir functions well to satisfy the intended purpose of diverting flow to the WID intake, the design of the weir creates a dangerous hydraulic condition that has claimed several lives over the years, and currently represents an impassable barrier to boaters and fish under most flow conditions. A pre-design study was undertaken to determine the feasibility of modifying the weir to allow small boat passage and to eliminate the dangerous hydraulic roller created by the existing structure (Golder, 2003). Other potential benefits include enhanced fish passage, channel restoration, and the creation of a whitewater recreational facility. The preferred alternative involves modifying the existing weir crest and replacing the existing concrete stilling basin with a series of smaller drops and pools to mimic a “natural rapids” in the reach downstream of the weir. It was proposed that the existing island downstream of the weir be raised and extended to create a separate high water channel (HWC), with multiple pool-and-drop features for whitewater recreational use, and low water channel (LWC) for downstream passage of beginner and novice boaters. Two physical models were utilized in developing the proposed design for the project: a “comprehensive model” was constructed at a scale of 1:50 to provide an overall assessment of how the facility will perform; and a “flume model” was constructed at a 1:15 scale to provide better insight into flow characteristics at specific in-channel drop structures (nhc, 2007). Although the proposed preliminary design met the study objectives, various options for filling in the downstream portion of the weir (HWC Drop #1) were conceptually developed, after the physical models were dismantled, to reduce construction costs. Additional modeling was deemed necessary to confirm whether hydraulic conditions remained satisfactory for the proposed modified design, and this modeling was carried out using computational fluid dynamics (CFD) simulations. World Environmental and Water Resources Congress 2008 Ahupua'a © 2008 ASCE Copyright ASCE 2008 World Environmental and Water Resources Congress 2008: Ahupua'a 3 Study Objectives The objectives of the CFD study were to: (i) assess whether possible design modifications to HWC Drop #1 create hydraulic conditions considered satisfactory from a boat passage perspective; and (ii) provide supporting information for assessing the need for additional erosion protection at the downstream end of the weir structure. CFD Model Description The CFD modeling software, FLUENT (version 6.3.26), was utilized to evaluate hydraulic conditions of the possible design modifications to HWC Drop #1. The model reproduced a narrow “slice” of river channel through HWC Drop #1 with simplified upstream and downstream bathymetries selected to be representative of the prototype. The CFD model employed the volume-of-fluid (VOF) model to predict the water surface profile and to assess whether a hydraulic jump forms downstream of the drop structure (FLUENT, 2007). The κ−e turbulence model was used in the numerical calculations of all simulations. The CFD model was capable of predicting the velocity distribution, water surface profile, vorticity, and boundary shear stresses throughout the model extents, which were used to assess the safety of boat passage and the need for additional erosion protection downstream of the weir. Although CFD models cannot be relied upon for the prediction of detailed standing waves in a river, they are capable of predicting the formation of hydraulic jumps (if present). In addition, qualitative data available from the physical models were used to provide guidance in interpreting CFD model results related to such a flow phenomenon. Geometries in the CFD model were comprised of approximately one million computational elements, which are considered sufficient for providing accurate predictions of flow patterns and velocities. Baseline Simulations (Model Validation) CFD model validation was conducted by comparing CFD modeling results for the existing weir and preliminary design to quantitative and qualitative observations on the comprehensive and flume physical models. Table 1 summarizes operating conditions for the two baseline simulations conducted for the existing weir. Table 1: Operating Conditions for Baseline Simulations Discharge (m/s) Unit Discharge Water Levels at Weir (m) Run No. Flow Condition Total River To WID Intake Below Weir (m/s/m) Upstream Downstream 1 Typical summer flow 150 13 137 0.91 1035.

A brief review of recent developments in biological nitrogen and phosphorus removal technology is presented. Guidelines are outlined of how current understanding of these two removal mechanisms can be applied in the upgrading of existing wastewater treatment plants for biological nutrient removal. A case history dealing with the upgrading of the conventional activated sludge process located at Penticton, British Columbia, to a biological nutrient removal facility with a design flow of 18,200 m3/day (4.0 IMGD) is presented as a design example. Process components requiring major modification were the headworks, bioreactors and sludge handling facilities.

[1] Realistic optimization of the operation of urban water supply headworks systems requires that the issues of system complexity and stochasticity be addressed. A promising way of achieving this is to couple probabilistic search methods such as genetic algorithms (GAs) with Monte Carlo simulation models. However, the objective function surface, characteristic of this genre of problem, exhibits piecewise flat regions separated by steep slopes. The size of these flat regions is affected by the frequency of droughts sampled in the Monte Carlo simulation. Although an earlier study proposed a GA variant that appears to robustly negotiate such objective function surfaces, the assessment was limited to a simple one-reservoir system. There remains therefore a legitimate concern that for more complex systems the GA may converge prematurely producing decisions of little practical value. This study assesses the ability of the GA to optimize key operating rules for a complex urban headworks system with nine reservoirs and interbasin transfers subject to a highly variable climate. Eight decisions affecting restriction rules, pump marks, and contingent desalination were optimized using an objective function that minimized expected annual costs. It is shown that the GA produced results that are judged consistent with the strategy that minimizes total expected costs. In addition, the sensitivity of the GA results to the length of the Monte Carlo simulation was investigated.

The irrigation systems of the Amu Darya basin are characterized by the following features. Water is withdrawn from the river through a cut along which the water enters the main canal having a length of 4-5 km. At the end of the canal are the headworks with outlet works, in some cases they are absent. Most headworks were constructed in 1930-1950 and do not have additional grooves for parts which could be used for installing various devices. There are no operating and highway bridges for delivering mechanisms, there are no approaches and roads to the gate sections. On examining the entire intake complex from the river to the reclamation system, we can distinguish three possible places of installing trash-cleaning and -retaining devices: on the headworks, on a stretch of the influent main canal, and in the river before the entry to the influent main canal. We developed a trash-cleaning complex installed on the headworks and enabling the retention and removal of foating debris beyond the limits of the intake. When operating this complex it is necessary to remove debris on time, not allowing its large accumulation. A number of trash-retaining and -removing devices installed on a stretch of the influent canal have been developed. P. V. Boguslavskii [1] suggested placing latticed panels in the canal at an angle to the direction of flow. Floating objects are directed into a storage basin. However, in connection with the fact that the basin is nonflowing and the velocity of the water moving into the basin is small, floating debris enters it slowly. Trash is removed from the basin by mechanisms located near it. The basin should be small, otherwise it will be impossible to remove the debris by mechanisms. At the same time, a small basin cannot be constructed, since the velocity of the flow at the entry will drop to zero and entry of debris will cease. A variant of constructing a flowing storage basin is possible here, which will make it possible to create favorable conditions for entry of debris into it as a result of an increase of the flow velocity. A part of the debris can be removed by mechanisms and a part can pass through the discharge canal into the river. Then the cost of all measures increases owing to the need to construct a discharge canal. Furthermore, under conditions of the Amu Darya, where its floodplain and channel intensely meander, destruction of the place of emptying of the discharge canal into the river, siltation, and even destruction of the canal are possible. A third variant is the creation of trash-removing devices in the manner of stream-directing systems [2, 3]. However, fixing them in the necessary position under conditions of marked meandering is approximate. It is necessary to create designs of devices of the given type which could be operated successfully under the specific conditions of the Ainu Darya. This will promote a cardinal solution of the problem: debris will not enter the headworks and, consequently, the reclamation system and influent main canal. In the new proposed design, representing floating devices (Fig. 1), the known suggestions are taken into account [1-3]. The main part of the design is a pontoon used for creating buoyancy of dredges and shorelines. The length of the pontoons is 540 cm, the width along the outer plane of the ellipses of the tanks is 253 cm, and the distance between tanks is 93 cm. The maximum height of the ellipsoidal (in cross section) tanks is 47 cm; the draft of the unloaded pontoon is 16 cm. The idea of the device is that the chain of pontoons secured in the river blocks the inlet to the influent main canal. The chain of pontoons should be placed downstream such that the direction of movement of the floating debris is tangential to the outer edge. In that case the floating debris does not enter the main canal but moves downstream. The pontoons are hinged together to form a single flexible system. So that debris does not get clogged under the concave part of the pontoon and between individual pontoons, deflecting panels 3 are fastened on the outer side (on the river side), and cord plates 7 riveted to the deflecting panels are placed in the space between individual pontoons.

1. Corrosion of the inside surfaces of pressure conduits leads to substantial head losses and to wear of these structures. During design and operation of these expensive objects, it is necessary to take measures to protect them from corrosion. 2. The inside surface of pressure conduits and surge towers can be successfully protected by means of cathodic protection. The following protective current densities are recommended: 2.75–3.5 mA/dm2 for the power conduits and 2.25–3.0 to 3.25–4.0 mA/dm2 for surge towers. 3. Tests of cathodic protection on actual objects of headworks show the possibility of its periodic connection.

The SS-18 ICBM silos and associated structures in the Republic of Kazakhstan, at the Leninsk, Derzhavinsk, and Zhangiz Tobe missile bases, and the test silos at Balapan, were dismantled under the provisions of the START I Treaty of 1991. Upon abandoning the bases, the Russian military destroyed the silos with explosives. The blasts destroyed the headworks structure, and left craters 6 meters deep and up to 25 meters across at each silo. In dismantling the sites, the remaining above ground and near-surface structures were demolished, with the rubble pushed into the empty silo tubes or adjacent pits. A reinforced concrete cap was placed over the filled silo tube. Additional building rubble was then pushed into the crater, over the cap. The rubble was covered with clean earth and topsoil. Metal and concrete were salvaged for recycling or for use in the surrounding communities. Once a site was cleared of all structures, it was graded to match the topography of the surrounding countryside. The reclamation process was completed by the acceptance of a finished site by the local, regional and state authorities. These authorities may then sell or rent the land to the local community, who will use the land for farming or pasture.

Embankment preloading, in conjunction with prefabricated vertical (PV) drains, was used to accelerate primary consolidation and to eliminate most of the anticipated secondary settlements of the soft clay foundation due to loading from a proposed wastewater treatment plant (WWTP). Subsurface exploration conducted during preliminary design indicated the presence of up to 60-m thick deposit of soft to very soft clay underlying the site. Estimates of settlement due to filling of the existing lagoon and construction of the WWTP indicated that the soft clay deposits will undergo up to 150 cm of settlement. Approximately 80 cm of this settlement was estimated to occur in the first 10 years of the plant operation and an additional 60 cm was estimated to occur during the following 30 years. UP to 19 settlement plates were installed under the embankment fill to monitor the preload performance. The measured settlements were then used to analyze the behavior of the soft clay foundation, and to develop recommendations regarding the time for preload removal and subsequent construction of the proposed WWTP. This paper discusses the results of settlement analyses and highlights the procedure that was used to predict the magnitude and time-rate of settlements based on field measurements. I N T R O D U C T I O N The city of Chewelah is located approximately 75 km northwest of Spokane, Washington along U.S. Highway 395. As a part of its ongoing improvement, the City has proposed the construction of a new wastewater treatment plant (WWTP). The new facility will consist of biological secondary treatment system providing nitrification, a disinfection facility, sludge handling and treatment facilities, headworks, a laboratory building, and related electrical and instrumentation control equipments. The proposed WWTP will be constructed by filling an existing sewage lagoon (called Lagoon #3) by as much as 2 m of soil to bring the grade to the current top elevation (El. 500 m) of the perimeter dikes. The lagoon covers and area of roughly 90 m by 135 m (see Figure 1). From the as-built drawings provided by the City, it appears that Lagoon #3 was constructed by building the perimeter dikes 1.5 to 2.4 m above the original ground surface. tProject Geotech. Engr., CH2M Hill, Bellevue, WA; 2Sr. Geotech. Engr., CH2M Hill Inc., Corvallis, OR; 3Project Manager, CH2M Hill Inc., Spokane, WA; 4principal, Campbell Services Group, Spokane, WA; SSr. Geotech. Engr. and Staff Manager, CH2M Hill Inc., Bellevue, WA; 6Senior Geotech. Engr., CH2M Hill Inc., Bellevue, WA; 7President, Drainage and Ground Improvement Inc., Bridgeville, PA

The following paper provides information for understanding the significant parameters that determine the reliability, functionality, and total costs for spillway and headwork gate hoists. The technical information covers the unique situations encountered for spillways and headworks. Specific topics include excessive hoist speed and capacity; advantages of low-efficiency, self-locking equipment; motor selection; controls (remote, local, overload, position, and low tech. vs. high tech.); and wire rope selection and lubrication.

Effective water policy is informed by thru distinct levels of analysis. First-best economics determines the optimal outflow from an irrigation system headworks, optimal distribution, optimal lining and optimal water pollution, all in the absence of transactional costs. The first-best optimum then serves as a benchmark for (second-best) comparative institutional analysis (such as evaluating prices) versus quantity mechanisms for efficient water management. Third-best principles allow the analyst to consider the rent-seeking consequences of alternative institutional designs, thereby highlighting the advantages of devolution.

Effectivness was evaluated of the Dryden Fish Screening Facility in the Wenatchee Reclamation District Canal near Dryden in north central Washington State. In situ tests were conducted by releasing groups of hatchery reared salmonids of different ages and sizes. Spring chinook salmon smolts (110-165 mm) were not injured or descaled in passing through the canal forebay. Smolts were not delayed as they migrated in the canal. Most fish released at the canal headworks exited the screening facility in 99% of the test fish captured in the fish bypass in

The three degrees-of-freedom in a straight alluvial canal can be represented by Froude number F ; width-depth ratios, and energy gradient S . They also can be represented by the coefficients in regime equations. The physical interpretation of these regime coefficients is investigated and thus the basic structure of Lacey's regime equations is explained. The Canal and Headworks Data Observation Program (CHOP) data on Pakistan Canals are analyzed in the framework of regime theory and it is shown that: (1) the width of a stable channel section is related to the maximum operational discharge with α 3 α 3 = 2.87; and (2) the regime coefficients, α 1 and α 4 , are related as the bed material load and resistance functions of sand-bed channels. It is concluded that in their day to day operation, the sand-bed alluvial canals have only one degree-of-freedom that is related to their bed material load.

1. The experience of operating the Pamir hydroelectric stations shows the general reliability of their use for supplying energy to remote regions; this experience must be taken into account not only when designing and constructing hydroelectric station in the mountainous regions of Pamit but also in other regions of the country. 2. Hydroelectric stations operating in remote, difficultly accessible regions should be highly reliable, especially against the effect of natural calamities. This reliability should be provided by a thorough study of plants with the use of model investigations and high quality of construction. 3. The experience of operating the Pamir hydroelectric stations leads to the following specific recommendations: a) As a rule, under the complex conditions of Pamir, especially in areas subject to mud flow, rock fall, and avalanches, the diversion canals should be enclosed, and in the Eastern Pamir, closed over the entire length to avoid prolonged forced shutdown of the stations during intense shuga flows. b) To protect intakes at the headworks from disastrous discharges occurring upon breakthrough of lakes formed by the damming of rivers by snowslide and mud flows, it is recommended to construct at the intakes deflector walls rising above the normal pool level; c) The personnel operating hydraulic structures of the Pamir stations should be provided with small mechanized equipment for controlling bed and suspended loads, mud flows, snow, and ice. 4) Both in the Eastern and Western Pamir long downtimes of the stations may occur owing to unfavorable natural phenomena; therefore, they should have a backup—a diesel-electric station provided with fuel to last at least two months.

The UK approach to pollution control in tidal waters places considerable emphasis on balancing the contrasting needs of utilization of the waters for the assimilation of effluents with the protection of all identified uses, i.e. the Environmental Quality Objective/Environmental Quality Standard (EQO/EQS) approach. In order to protect uses of the waters for bathing and general amenity, this approach in the design of improvement schemes necessary for marine sewage discharges is examined. However, recent guidelines for consent applications dealing with schemes designed to protect bathing use suggest a departure from the EQO/EQS approach towards an emission standard when dealing with the solid phase of the sewage effluent. The implications of these approaches are discussed from the design (scientific and engineering) viewpoints. A summary of headworks processes and the current practice for preliminary treatment at marine outfall sites in the UK is reviewed, together with comments on their effectiveness. The terms of reference and work of a joint working group to examine the efficiency of screening equipment at marine outfall headworks is described, together with a technical summary of results collected at a range of sites and with various types of equipment. Recommendations for future research are given, and a strategy for screening is developed.

The Isle of Thanet in South East England is an important holiday area with a total summer population of 180,000 in the four seaside towns of Birchington, Margate, Broadstairs and Ramsgate. Sewage is discharged to sea through short sea outfalls causing pollution of local beaches. The feasibility study into possible solutions showed that marine treatment is generally the most cost effective solution for coastal towns and that local solutions were cheaper than area solutions due to the significant impact of transfer costs. The marine treatment schemes now being built provide preliminary treatment of fine screening and grit removal in enclosed headworks with high velocity, plug flow, operation of the outfalls. Special structures have been provided to protect the tapering manifold multi-port diffusers and to provide access to the outfalls. Installation of the outfalls was successfully achieved from difficult clifftop sites.

In 1982, the Government of Alberta began a program to rehabilitate and expand existing irrigation headworks systems within southern Alberta. Particular emphasis was placed on effectively minimizing future seepage from these canal systems. To fulfill this requirement, Alberta Environment undertook an extensive study of methods of seepage control that would be most appropriate for use in this program. The study concluded that the installation of a complete canal buried membrane lining was one of the most effective methods for controlling seepage. The geomembrane material selected for use as the buried liner for this installation was 0.5 mm (20 mil) thick polyvinyl chloride (PVC). This paper presents the basis on which the complete canal buried membrane lining system was selected, the reasons for selecting the 0.5 mm (20 mil) thick PVC as the lining material, the quality control program for monitoring the purchasing of the PVC material, and the installation procedures used for placing the membrane within the canal cross section. The design criteria and construction procedures relevant to the earth cover material being placed on the membrane liner are also presented. Key words: irrigation, canals, seepage, lining, geomembrane, performance.

By the year 2000 the requirement for water in India is expected to increase from 310 to 590 km3 per year. A case has been made out to tap ephemeral streams by providing small reservoirs, water harvesting tanks and headworks for spate irrigation. Ephemeral streams in India flow in almost all the states and are characterized by the steep slopes, high peaks and short durations of flood flows, and high sediment transport rates. The short effective life of such reservoirs and factors such as stream flow variability and stream mobility warrant economy in design. To this end a few measures found suitable during investigations of two dam projects on such streams are presented.

The Melbourne and Metropolitan Board of Works in Melbourne, Australia operates two principle models of its water supply system. The first of these is a headworks model that simulates the major reservoirs and transfer mains of Melbourne's water supply system. This model uses monthly data for both the long-term planning of the water supply system and in assisting in operational decisions regarding transfers of water between headworks storages. The second model is a network model that solves for heads and flows within Melbourne's water supply distribution system. The model can be run over a 24-hour period and is used for investigating ways of improving the distribution of water within the system and for assisting and training operational staff. This paper describes the application of this network model to Melbourne's water supply system, including the implementation of computer graphics techniques. Examples demonstrating the application of color graphics to different parts of the system are given together with a discussion of the present integrated modeling, operation, and telemetry capability. The models will be continually modified and improved as both new systems are added to Melbourne's water supply system and greater knowledge of the existing system is ained. The implementation and use of the 24-hour network simulation program by the Board has already resulted in a current savings in excess of $30 million. This is more than six times the total cost of the modeling and telemetry system. Future benefits are expected to add to this savings.

The study area lies on the northern limb of the Mahabharat Synclinorium. It consists of the crystalline rocks of the Kathmandu Complex with underlying metasedimentary rocks of the Nawakot Comples, separated by the Main Central Thrust. The reservoir area of the project reveals the good site for the large storage capacity and seems feasible. The headworks site is fairly suitable for the dam structures. The intake canal, desander basin and the approach canal will be located on flat alluvium terrace. Common rock types along the headrace tunnel are slate, quartzite, phyllite, dolomite, dolomitic limestone and chlorite-schist. Generally rock belongs to poor to good class. The semi-underground powerhouse lies on gently dipping terrace deposits. The rock support recommended for the headrace tunnel is combination of local to systematic bolting and reinforced shotcrete as per requirements.