Scart Reservoir

Project Summary

Coffey Construction undertook the construction of a 12,500m3 concrete water reservoir adjacent to an existing 5000m3 reservoir structure at Scart Reservoir. Ancillary project works included a new access road and the upgrade of the existing control and water treatment buildings. It was imperative that the current system was kept running during the construction of the new works. Our work included the installation of two centrifugal booster pumps with motors to replace the existing split case type pumps at the existing 3 phase 415V power pumping station at Coolcorcoran Pumping Station, which supplies the Reservoir at Scart. The works at Coolcorcoran involved Civil/M&E upgrades to the existing pumping station to provide a capacity over 310 (l/sec) and upgrading of the electricity supply.

The reservoir was built on a 75mm layer of no-fines concrete (to facilitate drainage), on a 200mm layer of clause 804. Filter drains were placed under the reservoir and around the perimeter of the reservoir at the bottom of the drainage layer.  A composite geotextile/drainage membrane drainage layer was placed along the sides of reservoir prior to backfill. Stormwater collected was discharged to the public sewer through a new 300mm storm drain.  Approximately 45,000m3 of shale was excavated over a period of 4 weeks using two 45-ton excavators. 30,000m3 of this material was removed from the site and the remainder was stockpiled for re-use.

Robust barriers were used at the Scart site to segregate ongoing operations works at the existing treatment building from our worksite. The majority of our works were carried out independent of the adjacent reservoir and control building. Interface with the existing plant was only necessary for tie-in works and upgrades to the control building and this was planned well in advance with the client’s operations team. Given the high volume of material being removed on a daily basis, traffic management both on site and on the public roads was fundamental to the success of this operation. Road sweepers were extensively used to keep public roads clean.

Two 600mm ductile iron pipes and associated fittings and valves were used to link the new and existing reservoirs. A key element of this work was the phasing of shutdowns through liaison with the local authority. New ducts/chambers were installed electrical cables linking the existing treatment building to the new and existing reservoirs.

MEICA works included the flow control to and from the new and existing reservoir cells, continuous alarm level measurement, turbidity analyser, chlorine dosing system and SCADA and PLC programming.  Design and construction of the complete MEICA installation were undertaken by our in-house personnel.

A high-quality finish was specified for the structure. A trial panel was constructed off-site in advance of the works and an acceptable standard was agreed with the clients representative. Close monitoring of these works on an ongoing basis throughout the project ensured this finish was achieved continuously.

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