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This article is a case study for an energy savings performance contract (ESPC) at the wastewater treatment plant for the City of Riverbank in California. The existing plant has an average of 1.67 million gallons per day (MGD) flow and consists of the headworks, four treatment ponds, and seven percolation ponds. Prior to the project, the treatment ponds used surface aerators to provide oxygen for the biologic process. The plant was primarily operated manually with limited dissolved oxygen control. The utility bills showed excessive energy use—annual usage was 5,673 kWh/MG/yr. Schneider Electric and the City of River-bank entered into a construction contract to retrofit the treatment ponds with blowers and fine-bubble diffusers for more efficient oxygen transfer. Additionally, a control system was installed to maintain a dissolved oxygen set point. This scope of work is estimated to save 75% of the electricity consumption at the wastewater treatment plant and will save the city 65% of their electric...

The SHAFDAN is the largest wastewater treatment plant in Israel and currently treats 360,000 m3/day of municipal wastewater, about 92% of its treatment capacity. Waste sludge from the plant is discharged to the Mediterranean Sea through a marine outfall. The SHAFDAN is committed to ending the disposal of its sludge to the sea by the end of 2016 by providing a land-based biosolids management program that produces a Class A biosolids for agricultural use. In order to implement this strategy, a number of large-scale construction projects were undertaken. These projects include a new sludge thickening and dewatering facility, updated headworks, a new primary treatment facility, and a new 3-stage thermophilic anaerobic digestion facility. The total capital cost of these projects is estimated to be US $300 million. This paper describes the principal components of these projects and their design parameters.

Large numbers of perennial rivers flowing through steep gradient has made Nepal an ideal place for hydropower development. Development of hydropower project in most economical way possible is the first prerequisite to get maximum benefit from harnessing water resources. The maximum benefit can be achieved only through optimal design of the project. Each project component must be designed considering the required level of factor of safety, performance standards of each component and economy. On this backdrop, this paper intends to optimize the location of cutoffs in headworks to get maximum benefits from use of it in terms of safety and economy. Improper placement of cutoff not only reduces the factor of safety against piping but also curtails the project benefits due to excessive seepage flow. Piping (internal erosion of soil particles under structure) is associated with high exit gradient. It threatens the structural stability and ultimately leads to failure of structure while as excessive seepage flow limits the availability of flow for power generation and reduces the project benefits. So, the optimal design of headworks is an attempt to identify the best location of cutoff to control seepage flow and reduce exit gradient. Five different cases representing different location of cutoff were analyzed and their roles in controlling seepage flow and reducing exit gradient was evaluated to optimize the cutoff location. 2D Finite Element Method (FEM) was used for the seepage analysis. The analysis showed that cutoffs are essential to control seepage flow when dam/weir is founded in pervious soil. However, the best location to place cutoff must be adroitly identified to reap maximum benefit from use of cutoff. The analysis reveals that the role of central cutoff in controlling seepage flow and reducing exit gradient is very limited. Likewise, the u/s cutoff has minimum effect in reducing exit gradient but the d/s cutoff seemed very effective in reducing exit gradient resulting increased factor of safety against piping. Hence, this paper concludes that the d/s end is the optimal location to place cutoff to improve safety and economy of the project. In addition, the use of both u/s and d/s cutoffs extend positive roles both in controlling seepage flow and reducing exit gradient. However, in author’s opinion the construction cost of two cutoffs must be compared with benefit added by use of two cutoffs over use of single d/s cutoff. HYDRO Nepal Journal Journal of Water Energy and Environment Issue: 21, July, 2017 Page: 42-44 Upload Date: July 18, 2017

Grit is a nuisance material that causes abrasive wear to mechanical equipment increasing maintenance and operational costs while reducing equipment performance and useful life. Grit that is not captured in the headworks accumulates in processes throughout the plant, reducing capacity and detention time, and adversely influencing flow and circulation patterns 2 . Deposited grit must be manually removed, handled, hauled and disposed. Abrasive wear, process inefficiencies and basin cleaning operations increase treatment plant operating expenses. Choosing a grit removal technology has often been based on equipment price with little regard for device efficacy and consequent grit removal efficiency. The industry has lacked an unbiased side-by-side comparison of the currently available technologies. As a result, owners and engineers are forced to navigate a field of, what can be conflicting, performance claims made by various equipment manufacturers. This situation is perpetuated by the fact that there is no accepted, peer reviewed test standard for grit sampling and analysis. The purpose of this paper is to encapsulate various grit removal system performance data generated by a consistent and repeatable sampling and analysis methodology for the purpose of comparing virtually all grit removal technologies in terms of their effectiveness. Results determined with this sampling method corroborates with the operating history and performance at the tested plants with respect to grit removal, suggesting the accuracy of the test method 6. The data provides an unbiased side-by-side comparison of the actual performance of grit technologies based on a repeatable sampling and analysis methodology that owners and engineers can utilize to protect plants from deposition, abrasive wear and associated costs from this nuisance material.

Demand-based irrigation systems are operated according to crop water requirements. As crop water requirements remain variable throughout the growing season, the discharges in the canal also vary to meet demands. The irrigation system under study is a demand-based semi-automatic irrigation system, where flows in the main canal are automatically controlled and secondary canals manually operated. The main canal headworks have been equipped with the SCADA system with proportional integral (PI) discharge controllers and the canal itself has been provided with self-regulating AVIS/AVIO downstream control gates for flow regulation in the canal. The secondary canals have manually operated sliding gates, which are opened or closed as per crop water requirements of the command area following a crop-based irrigations operation (CBIO) schedule under which they remain closed for one week after one or several weeks open, depending upon water needs. The flow in the main canal is then automatically adjusted according to the number of open or closed secondary offtakes. These operations result in fluctuating flows in the main canal and if not properly planned can cause serious implications for canal safety and its hydrodynamic performance. The PI discharge controllers regulate discharge releases to the canal in order to satisfy demands. The proper selection of PI coefficients ensures system safety and efficient water delivery. The operation of the secondary canals also plays a key role in defining the performance of the automatic operations. The planned opening and closure of a cluster of offtakes ensures safety of the self-regulating structures and stability of the flows in the main canal. In this paper various options have been tested using hydrodynamic modelling and we found some optimal values of PI coefficients and defined some rules for secondary canal operations to enhance the operational performance and sustainability of downstream-controlled irrigation canals.

The objective of the present study was to demonstrate the effect the environment's entitlement configuration has on the volume of water supplied to the environment, and the overall efficiency of the water supply system under the historic climatic sequence and climate change. The modelling work is undertaken using the REALM simulation package, with the results presented in case study form based on the Wimmera-Mallee system, outlining the changes in the total system water balance post-Wimmera Mallee Pipeline, changes in the environment's reliability of supply, and exceedance plots for environmental flows and headworks loss. The outcomes of this study demonstrate the need to consider the trade-offs between large entitlements of low reliability and small entitlements of high reliability as part of the system reconfiguration process, given the effect it has on total system efficiency, particularly in an uncertain climate future.

The paper reviews the problems being faced by the Upper Chenab Canal (UCC) and reports on the existing conditions assessed during various site visits. The water availability in the River Chenab at the Marala Barrage has been analysed based on the previous 20 years of recorded data in order to explore possible options for remodelling this canal. The visit report indicated that the UCC is faced with numerous problems such as bank erosion, bed scouring, side embayment, inadequate freeboard, abnormal behaviour and the deterioration of old hydraulic structures. Deferred maintenance and lack of proper and timely monitoring seem to be the main factors in the continuation of these problems in the canal. The water requirements at the head of the canal have been worked out as 562 m3 s−1, nearly 20% higher than the present capacity (477 m3 s−1). The study shows that the required amount of water is available for more than 90 days during the peak demand at 80% reliability for irrigation, hydropower generation and inter-river transfer to the River Ravi upstream of Balloki headworks for feeding its offtaking channels. The analysis also shows that the existing canal section is insufficient to pass the required discharge and needs to be remodelled to meet the requirements. This can be achieved by revising the canal section using a comprehensive design approach best suited to the local conditions. Copyright © 2010 John Wiley & Sons, Ltd. RESUME Le document passe en revue les problemes rencontres par Upper Chenab Canal (UCC) et rend compte des conditions existantes evaluees lors des visites d'inspection. La disponibilite de l'eau dans la Riviere Chenab au Barrage de Marala a ete analysee sur la base des vingt dernieres annees de donnees pour explorer les options possibles pour le remodelage de ce canal. Les rapports d'inspection montrent que l'UCC est confrontee a de nombreux problemes tels que l'erosion des berges, sedimentation importante, recul et echancrure des berges, insuffisance des franc-bords, un comportement anormal et la deterioration des anciennes structures hydrauliques. Le defaut d'entretien et l'absence de surveillance adequate semblent etre les principaux facteurs explicatifs des defauts constates. Les besoins en eau a la tete du canal sont estimes a 562 m3 s−1, soit un excedent de pres de 20% par rapport a la capacite actuelle (477 m3 s−1). L'etude fait ressortir que la quantite d'eau necessaire est disponible pour plus de 90 jours au cours de la demande de pointe a 80% de fiabilite pour les differents usages que sont l'irrigation, la production hydroelectrique et un transfert inter-fleuve vers l'amont de la riviere Ravi Balloki. L'analyse montre egalement que la section du canal actuel est insuffisante pour passer le debit requis et doit etre remodele afin de satisfaire aux exigences. Ceci peut etre realise par la revision de la section de canal en utilisant une approche de conception adaptee aux conditions locales. Copyright © 2010 John Wiley & Sons, Ltd.

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 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 urb...

The Dujiangyan Irrigation Scheme is located in the middle reach of the Mingjiang River in Sichuan Province. It was initiated by Li Bing, the governor of Shu Prefecture, in the Qin Dynasty in 256 BC. It is a great scheme with a long history of 2260 years in ancient China, and has been very well operated until today. The headworks of the Dujiangyan Irrigation Scheme are composed of three major parts, i.e. Dujiang Yuzui (fish mouth), Feishayan, and Baopingkou. Dujiang Yuzui is a diversion dam, dividing the Mingjiang River water into two rivers, the Outer River and the Inner River. Feishayan is a spillway used for removing sand and excess water from the Inner River into the Outer River during flood. Baopingkou is an intake of the irrigation system, which automatically controls for a steady flow. These three parts are combined as an organic and complete whole with multiple functions of diverting water, spilling flood, releasing sediment, silt sedimentation, and automatic control of irrigation water. The whole headworks are reasonably planned and ingeniously coordinated with obvious effectiveness. In particular, this scheme has successfully treated the silt problem, therefore the possibility of being damaged by silt sedimentation is to a great extent avoided, and thus it can continue to flourish. In addition, the system of yearly maintenance also has its specialty: the construction technique is easily mastered by farmers, and all the construction materials came from local places. Therefore, the Dujiangyan Irrigation Scheme can normally be operated generation after generation. The Dujiangyan Irrigation Scheme encapsulates the scientific intelligence and civilization of Chinese nationality, and it still plays a vital role in the economic, social, ecological and environmental benefits for Sichun Province nowadays. It is a model of harmonious coexistence between mankind and nature, and is also included as a World Heritage Site by the United Nations Educational, Scientific and Cultural Organization (UNESCO) as the first water project in the world. Copyright © 2006 John Wiley & Sons, Ltd.

Simulation models in conjunction with synthetic multiple hydro-climate replicates provide the most realistic assessment of the performance of urban water supply headworks systems. However, optimization using such models is computationally very demanding. To appreciate the challenge, a simple case study system is presented. The system consists of one reservoir, has three decision variables to be optimized, and uses an objective function based on reservoir costs and economic penalties for water shortages. Enumeration revealed that the objective function surface has piecewise flat regions that arise from operating rule thresholds and the infrequent sampling of severe droughts. Two search methods capable of dealing with such flat regions, the genetic algorithm (GA) and the shuffled complex evolution (SCE) method, were investigated. For the GA to be robust (i.e., avoid premature convergence on flat regions), it was necessary to employ two lesser-known genetic operators, inversion and population selection strategy. The SCE method was found to have comparable robustness, but required fewer evaluations. Nonetheless, the GA method was preferred because of its inherent advantage in parallel computing.

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

[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.

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.

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.

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.

[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.

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.

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.

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.

1:20 scale model of interchange structure at junction of two outfall sewers approaching Hyperion Sewage Treatment Plant, Los Angeles, Calif, was tested in accordance with Froude law, to determine effects of various flow distributions among two influent sewers and channels leading to new and existing headworks; configuration of throat was studied.

The irrigation infrastructures in Farmer’s Managed Irrigation Systems (FMIS) of Nepal were mostly built from the local materials of mud, stone, and forest products with rudimentary traditional methods, practiced over many centuries. These systems are operated and maintained solely by the community farmers or an individual family. The Nepal Irrigation Sector Project (NISP), funded under the credit assistances of the World Bank, sponsored the modernization of these FMIS in the three western regions of Nepal from 1998 to 2004. The paper gives an account of the infrastructures built under the project to modernize the FMIS, and presents some facts about the impacts of the assistances to FMIS in relieving problems faced by farmers. The structures in the FMIS differ nominally according to the ecological region, due to the terrain and characteristics of the conveyance systems. In the hills, generally, lining and cross drainage structures are common; whereas, in the Terai, it is mostly the headworks structure due to lack of traditional materials as shrubs and forest products. The NISP assisted these FMIS with the participation of the users and their contribution in the civil works from seven to 15 percent. The users were involved in the design and construction of the infrastructures from the very initiation of the schemes. The project had good impacts on system performance and, thus, in agriculture production. Key words: FMIS; Irrigation; Participatory development; Water distribution; Modernization; Nepal DOI: 10.3126/hn.v6i0.4196 Hydro Nepal Journal of Water, Energy and Environment Vol. 6, January 2010 Page: 55-60 Uploaded Date: 24 January, 2011

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The main object of the paper is to describe the development, layout and construction of the Ceannacroc and Glenmoriston underground power stations in Inverness-shire which form part of the Moriston Scheme of the North of Scotland Hydro-Electric Board. Certain features of the headworks are of special interest and these are dealt with briefly.