Augusta Boat Harbour breakwaters

This paper outlines the construction of rock armoured breakwaters for a small boat harbour in the south of Western Australia using an onsite granite quarry. The Augusta Boat Harbour provides a safe haven for vessels in the south west corner of Western Australia. The facility includes a public boat launching facility, a land-backed service wharf, forty boat pens, land development lots and parking. The harbour was constructed by the West Australian Department of Transport and opened in November 2014. Geotechnical investigations of the onsite quarry were undertaken prior to construction. Quarry establishment required consideration of steep slopes, limited working areas, clay and environmentally sensitive areas, including declared rare flora. Rock structure was more variable than expected throughout the quarry, however the Contractor was able to successfully yield the required rock tonnages, classes and production rates to construct the breakwaters. The onsite quarry limited carting distances, costs and construction impacts on the town of Augusta and local roads; and allowed for the provision of future parking and development areas. Breakwater construction challenges included placement of armour across a variable tidal rock shelf, alternate toe configurations to accommodate variable underlying bed conditions, consideration of long-wave penetration and the construction of a high, narrow parapet for wave overtopping protection and future pedestrian access. Initial concerns about limited quarry yield translated into an oversupply of material toward the end of the project. The management of armour yield, tracking of volumes placed, and identification of immediate offsite uses for the excess rock was challenging but ultimately resolved through supplying armour to a nearby breakwater project at Port Geographe, Busselton. Careful placement of armour rock by experienced operators was considered to be fundamental to the quality of the constructed breakwaters. The new harbour is well received by the local community and leaves a lasting legacy for marine safety. Whilst some innovative approaches to breakwater construction were adopted, the use of onsite quarries for breakwater construction is a very traditional method of harbour construction that is considered to provide significant financial and logistical benefits.