CASE STUDY ––––––––––––––––––––––––– CHAFFEY UPGRADE Tamworth, NSW, Australia

Reinforced Earth® Retaining Walls TerraPlus®, Wirewall & Structural Precast Products

Owner: WaterNSW Consultants: URS Australia Pty Ltd Contractors: John Holland Pty Ltd Construction: 2015 - 2016

Background Challenges

Chaffey Dam is located 43km south- The scope of works for the upgrade east of Tamworth on the Peel River, included: firstly, the installation of a

NSW. The dam provides water for vertical Reinforced Earth® wall irrigated agriculture, industry, town structure with an attached 1.8m water supplies, river flows and parapet wall on the crest of the domestic requirements, flood existing earth and rockfill mitigation and environmental flows. embankment to raise the dam wall by

Prior to the upgrade the dam could be 8m; and secondly to raise the water described as a 54m high, 430m long level by 6.5m by duplicating the clay cored rockfill embankment with a existing bell mouth crest of the combined morning glory spillway and morning glory spillway structure at a outlet works. higher level.

The objectives of the Chaffey Dam RECO was contracted to design and

Safety Upgrade and Augmentation supply 6950m² of Reinforced Earth®

Project was to augment the dam’s back to back walls. In addition, on the storage capacity from 62GL to 100GL top of the upstream wall is a 1.8m and upgrade the dam to comply with high parapet wall and at the base is

ANCOLD and NSW Dam Safety an L-shaped wall with a handrail.

Committee (DSC) safety standards This L-shaped walkway creates regarding flood mitigation and stability walkway access along the upstream of the structure. of the wall.

Stage 1 of the project was the RECO also designed and supplied a construction of a 35m auxiliary temporary Reinforced Earth® wire spillway with release plug which was wall which created a cranage completed in 2011. platform from which the morning

Stage 2 and augmentation involved glory spillway bell mouth crest was raising the dam wall by 8m and raising raised. the morning glory spillway bell mouth The design engineers were required crest by 6.5m. to assess stresses and deformations Main: View of the completed Reinforced John Holland Pty Ltd (JH) was under flood surcharge loading Earth® upstream wall. appointed as the Principal Contractor conditions, evaluate earthquake Above first picture: The precast concrete products delivered and stored on site. of Stage 2 by WaterNSW, URS response of embankment and Second picture: The placing of the first Australia Pty Ltd (now AECOM) vertical crest raise and evaluate panels of the back to back walls. Third picture: The compacted backfill designed the dam raising, The stresses at the base of vertical crest during construction. Reinforced Earth Company (RECO) raise for assessment of the bearing was subcontracted by JH to design capacity for load cases (static, flood, and supply the Reinforced Earth® earthquake loading cases). structures and Fusion Civil Pty Ltd installed the walls.

Hydraulic Structures

Above Left: View of the Reinforced Earth® downstream wall Above Right: View of Reinforced Earth® temporary wire wall

Solutions At RECO’s precasting facility in Project specifications The Reinforced Earth® technique is Tuggerah, approximately 1910 –––––––––––––––––––––––––––– perfect for forming a double-faced TerraPlus® precast concrete facing Systems Reinforced Earth® with structure to raise the height of an panels were cast to construct the TerraPlus® concrete facing panels, parapet & L shaped structural precast products existing earth dam and thus to upstream and downstream walls, –––––––––––––––––––––––––––– increase the spillway capacity and 124 L-units manufactured in Peri Finish Concrete Smooth Grey eventually the holding capacity of formwork for the walkway, 31 –––––––––––––––––––––––––––– Structure Back to Back the it impounds. The parapet units to match existing Reinforced Earth® walls uniform distribution of the loads units from the original dam for the –––––––––––––––––––––––––––– throughout the Reinforced Earth® upstream wall. The manufacturing Area 6950 m² –––––––––––––––––––––––––––– mass and the ability to increase the and storage of the precast Max. Height 7.3 m stability of existing embankments structural products and precast –––––––––––––––––––––––––––– make the method well suited for concrete facing panels for this Length 1002 Lm –––––––––––––––––––––––––––– construction on top of earthfill . large project was a logistical Design load 20kPa The precast concrete panels challenge. All materials were –––––––––––––––––––––––––––– combined with proper backfill transported and stored on site in Design life 100 years materials ensure adequate drainage, readiness for the rapid construction System Reinforced Earth® Wire wall especially if the structure may be inherent to these structures. –––––––––––––––––––––––––––– subjected to sudden rapid draw Structure Temporary wire wall down and other variations in water –––––––––––––––––––––––––––– Conclusion Area 110 m² level. To ensure adequate drainage The benefits from this project will –––––––––––––––––––––––––––– the select backfill chosen was be to secure a long term water Max. Height 6 m placed in multiple select fill zones –––––––––––––––––––––––––––– supply for Tamworth, improve the Length 20 Lm ranging from silty, to sandy, to security of water entitlements for ––––––––––––––––––––––––––– granular. The finer backfill was downstream users, and improve Design load 20kPa–100kPa (crane pads) ______placed on the upstream side so if the ability of the dam to withstand any water ingress occurred it would extreme flooding. be accommodated by the granular fill on the downstream side.

Right: View of the Reinforced Earth® wall during construction from the morning glory spillway

Reinforced Earth Pty Limited Reinforced Earth Limited Level 4, 20 George Street PO Box 72 734 Hornsby NSW 2077 Australia Papakura Auckland New Zealand Ph +61 2 9910 9910 Ph +64 9 236 3385 Fax +61 2 9910 9999 Fax +64 9 236 3385 www.reco.com.au www.reco.com.au