CASE STUDY

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Adelaide office: 53 South Terrace, Wingfield SA 5013 Queensland office: Lot 9 Cooper Street, Dalby QLD 4405

WATTLE PARK RESERVOIR LINER & COVER REPLACEMENT

Project: Wattle Park Reservoir Liner and Cover Replacement

Client: SA Water

Head Contractor: Fabtech Australia Pty Ltd

Location: Wattle Park, South Australia

Size: 27,000m2

Completed: March 2012

Project Type: Design, Supply, Installation, Site Remediation, Commissioning

Application: Potable Water Storage

Fabtech Australia’s successful completion of the Wattle Park Reservoir Liner and Cover Replacement was integral to Adelaide metropolitan’s water supply, as well as to the broader success of the North South Interconnection Sys-tem Project. This project encompasses part of the eastern transfer system providing SA Water with the capability to interconnect the southern and northern networks, ensuring security and versatility of water transfer is main-tained. 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 and included 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 ge-ometry 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 perform-ance 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 working to ensure safe working and weld integ-rity. 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 in 40 parcels weighing 3 tonne each, then elevated out by crane. To ensure the new lining system achieved the required design life, the concrete basin was remediated where necessary and a protective cush-ioned 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 compli-cated 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 asset life, the cover design in-corporates 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 cover ballooning from air entrapment, as well as 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 have also provided the water industry with working prototypes and installation methodologies for use on future water storages.

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 nil lost time injuries. The reservoir has been back in service since February 2012, functioning as per the design and client expectations.