EYE-SORE: A Sewerage Agency Summary of Rehabilitation Experience

P ublic awareness of the importance of the sewerage network is inevitably highlighted when the system suffers malfunction. Associated with surface collapse or increased pollution to a local watercourse the effects are more widely felt, whilst even programmed work is not without significant environmental impact. With its history of deteriorating and failed sewers, the rehabilitation work already implemented and the introduction of a strategic sewerage policy, the paper outlines aspects of the City of Manchester's experience and effort to eradicate the consequential scars of its heritage whilst also looking to the future.     

Economic Optimization of Distribution Leakage Control

E vry WATER DISTRIBUTION system has an economic optimum level of leakage. To maintain that optimum level of leakage there is a corresponding optimum level of leakage control activity.
Despite much work on this subject, particularly in recent years with publication of DoE Report No. 26¹, many undertakers remain unclear about their economic optimum leakage level and how much effort is required to maintain that level.
This paper describes development of an economic model which attempts to quantify optimum leakage through measurement of parameters which should be readily available or obtainable.
The model was originally developed specifically for routine sounding. However, extension of the basic principles allows development of a general optimization theory. The paper then shows how the theory can be applied to optimization of district metering     

The Effect of Borehole Sealing on the Southern Lincolnshire Limestone Catchment

The Southern Lincolnshire Limestone is an important groundwater resource; however, for many years water has been lost from the aquifer system through uncontrolled artesian flow from wild-bores in the Fenland area. During 1991–92, there was an extensive programme of sealing or controlling the wild-bores, and compensation flows for ecological and farming purposes were provided at some sites.
This paper describes a field study which was designed to identify the important features of part of the catchment; this was followed by the development of an existing groundwater model to provide an improved representation of the uncontrolled and controlled wild-bores. The model is used to assess the consequences of controlling or sealing the wild-bores.     

Managing Water Services Through Service Differentiation and Pricing in an African City

A key challenge for managers of water utilities in developing countries is to provide services to the rising urban population in a financially sustainable manner. The paper examines the management of water services in an African city which piloted service differentiation and pricing. Among the key findings was that substantial improvement in the provision of water services to the urban poor was attained. Cost recovery was achieved through innovative structuring of public/private partnerships, an appropriate pricing policy, and flexible payment systems. The project demonstrates that (a) by structuring service delivery with appropriate pricing, utilities could serve more customers (including people living in informal settlements) at affordable cost and achieve financial sustainability, and (b) service differentiation and appropriate pricing has the potential to improve urban water services in low-income countries.     

The Effect of Overbank Flow in a Meandering River on its Conveyance and the Transport of Graded Sediments

A large-scale model hydraulic study of inbank and over-bank river flow, using a regular sinuous river channel with a mobile bed, was carried out in the Flood Channel Facility at HR Wallingford, UK. The selected sediment had a wide range of particle sizes present over the 'fine sand to coarse sand'range. Flow velocity, local and global sediment transport rates, and channel conveyance were all measured. The resulting bed forms were determined and used to explain the secondary circulation in the sinuous channel as well as the size sorting of the sediment. The paper gives an early overview of this major project.     

An Assessment of Water Demand Management Options from a Systems Approach

A systems approach is used to model the urban water and wastewater system. Scenarios are developed for the implementation of a range of water demand management measures, including (a) leakage reduction, (b) the increasing use of water metering, (c) the replacement of standard WCs by low-flow WCs, and (d) the introduction of greywater recycling systems. These measures are assessed according to the water saving, cost per unit of water saved, and other indicators of the relative contribution to the sustainability of the system. Preliminary assessments of selected environmental costs and benefits are also included.     

Laboratory Investigation into the Performance of an In-Sewer Vortex Flow Regulator

Aspects of the hydraulic performance of an in-sewer vortex regulator have been studied. These devices are increasingly used in stormwater management schemes, but their characteristics under a variety of prototypical situations have not been widely disseminated. The study used a full-size laboratory mockup of a section of sewer and associated manhole with facilities for measuring discharges of up to 60 1/s. The performance of a typical vortex flow regulator was investigated under both steady and unsteady flow conditions. The steady head-discharge relationship revealed the expected 'kick back'region (during rising head); however, this was less pronounced during falling head. Under unsteady conditions, vortex initiation was affected and a hysteresis effect was noted. The influence of downstream surcharge was significant at lower upstream heads. Theoretical comparison showed that to obtain equivalent performance, an orifice of 62% of the diameter of the vortex regulator would be required, and 25% savings in storage could be made.     

Digital Mapping for Watermains in Torbay

T he development of a digital mapping and database system for water supply and distribution is described. The procedures adopted in producing the User Requirement Specification and preparing the existing records for conversion to digital form are outlined, and the manual digitization methods used for data conversion are detailed.     

Design and Implementation of the River Sheaf Comprehensive Flood-Alleviation Scheme

The River Sheaf Comprehensive Flood-Alleviation Scheme is a flood-defence scheme promoted by the Yorkshire Region of the National Rivers Authority. The scheme will improve 5.2 km of main river from a 1-in-5 year standard to a 1-in-50 standard at an overall cost of £3.1 million over the next four years. The hydrological, hydraulic and benefit/cost analyses have been carried out by the National Rivers Authority. Balfour Maunsell were commissioned to carry out the detailed structural design, prepare and administer contracts and supervise construction. The paper covers the preliminary design work and the detailed design of Phase I of the scheme.