Water Supply Network Improvements – Apia, Samoa
Fraser Thomas were selected by the Samoa Water Authority to provide services for the development of a 20 year upgrade programme for bulk meters and valves on the Alaoa and Fuluasou network which serves the main city of Apia.
Initial inspections found that many present day difficulties of intermittent supply, low or excessively high pressures, excessive non-revenue water losses and unclear definition of pressure zones related to issues of lack of maintenance, service life, type, size, durability and spares availability of assets installed in the past under several different projects, and there is a need for uniformity of control valves across the entire network.
The next phase comprised running the EPAnet water supply network model for the Apia Master Plan to check pressure and flows through PRV and Bulk Water Meter locations, as well as carry out checks on design proposals.
Site inspections and meetings were undertaken with SWA managers, engineers, maintenance staff and operators in Apia to discuss and confirm the designs, followed by preparation of a formal design report. Key recommendations of this report include:
- Implementation of network upgrade works including:
-Upgrading 12 PRV assemblies, all with new chambers, comprising nine 150 mm PRVs, two 300 mm PRVs, and one new PRV assembly to split one zone into two
-Retrofitting Altitude Control Valves with backflow control on two reservoirs
-Replacement of multiple bulk water meters with new meters of specified sizes based on the EPAnet model results, some of which differ from the Apia Master Plan recommendations.
- Addressing significant health and safety issues observed in the field, including missing covers to chambers, unsecured fenced compounds and reservoir ladders accessible to the public
- Undertaking field investigations to confirm the extent of each zone, with corresponding update of the model
- Undertaking, with urgency, a leak detection and repair programme
- Systematic checking and revision of the network hydraulic model to address a number of issues identified during this study, including the model scenarios not including all shut valves, incorrect representation of some high flow nodes such as the hospital and brewery, and possible extension of the model to include time series analysis.
The report was well received by the Samoa Water Authority and is being implemented.
- Inception report
- Water supply network modelling
- Options analysis
- Preliminary design and capital and operating cost analysis
- Site Investigations
- Design report