SA Water - Wattle Park Reservoir Liner and Cover

Projects ~ Covers

Principal: SA Water
Head Contractor: Fabtech
Location: Wattle Park, SA
Date: January 2012

Project Scope:

Fabtech Australia’s successful completion of the 27,000m² Wattle Park Reservoir Liner and Cover Replacement was integral to Adelaide metropolitan’s water supply and the broader success of the North South Interconnection System Project. As the head contractor, Fabtech supplied, designed, installed and electronically tested the liner and cover to meet the specifications of the client SA Water.

Additional Information:

This project encompassed part of the eastern transfer system providing SA Water with the capability to interconnect the southern and northern networks, ensuring security and versatility of the water transfer was maintained. With the potable water storage’s peak operational period fast approaching, SA Water contracted Fabtech Australia to carry out the design, site remediation, construction and commissioning of the new liner and floating cover for the 27,000m² potable water storage. The storage was an irregular shape including floor structures and mixers, which presented design challenges to achieve a taut cover surface when in service for effective on cover water and solids management. A complex central plate design was used with primary and secondary defined sump features. To support the requirement and minimise on site time the design also incorporated large area segments, allowing prefabrication of critical geometry and bulk area segments. A number of liner and cover geomembrane materials were considered for this project. Fabtech selected an unreinforced high performance geomembrane material with high elongation performance and flexibility with exceptional UV resistance and chlorine performance. The site activities were undertaken during the South Australian summer, with daytime temperatures inside the storage above 50 degrees celsius. This necessitated night time shifts to ensure safe working and weld integrity. As the storage was located in a residential area specific strategies were necessary to manage noise and light pollution.   Following removal of electrical fencing and other redundant facilities, the existing liner and cover was cut and rolled into 40 parcels weighing 3 tonne each, which were subsequently elevated out by a crane. To ensure the new lining system achieved the required design life, the concrete basin was remediated where necessary and a protective cushioned geotextile layer installed. The lining system was required to operate with an Action Leak Rate, based on the relevant technical paper and verified with regard to this performance by hydrostatic testing. As repair of any liner defects would be complicated by the need to empty the storage and to work under the installed cover, the completed lining system was validated by electrically testing to ASTM 7003. This process assisted in the lining system being commissioned without the need for any repairs. To facilitate cleaning and maintenance during the asset life, the cover design incorporated capability of inflation in addition to the inspection hatches and sampling ports. Fabtech engineered an industry leading design featuring a unique active vent system to avoid the cover ballooning from air entrapment, an innovative mixing system to enhance water consistency and reduce required chlorine levels and a cover that functions at all water levels. These Fabtech engineered outcomes not only served as solutions to project challenges, but also provided the water industry with working prototypes and installation methodologies for use on future water storage projects. Fabtech Australia’s installation crew delivered the liner and floating cover installation with minimal disruption to the community and environment, while achieving a project safety accomplishment of zero lost time injuries. The reservoir has been back in service since February 2012, functioning as per the design and client expectations.