Ngununggula, Southern Highlands Regional Gallery, Retford Park

Ngununggula is the first regional art gallery in the Southern Highlands. The new state-of-the-art facility is housed in a sustainably re-purposed dairy structure located in the National Trust property of Retford Park. Northrop were engaged to provide civil and structural engineering services.

Construction of the gallery coincided with the opening of our Bowral office in mid-2020, which meant we were able to maintain a site presence and utilise local knowledge and long-standing working relationships with relevant authorities (Water NSW, National Trust and Wingecarribee Shire Council) to the benefit of the project.

Challenges & Resolutions

A new council road was required to be built for access to the gallery and the proposed route for the road was to traverse a flood plain for a tributary of the Mittagong Creek. Northrop carried out a flood study, modelling various culvert and road geometry options, ultimately deciding on a small culvert and causeway which minimised impact on flood levels and resulted in cost-savings for the client. The road alignment also crossed a high-pressure water main (which supplies water to most of Bowral). Working in conjunction with Council and the contractor, we designed a protection slab detail and construction methodology to allow a road to be built over the main, without posing a risk to the water supply of Bowral.

Located within the Sydney Drinking Water Catchment, the development was also subject to stringent Water NSW requirements. A network of swales and a bio-retention basin was required to meet water quality targets. Northrop worked closely with the Landscape Architect and Water NSW to ensure the landscape design intent for the basin was achieved, and Water NSW requirements were adequately met.

Another challenge to address included the discovery of poor subgrade during construction works. We acted proactively and quickly with the construction team and the Geotechnical Engineer to design a rock bridging layer under the road pavement, and redesign the road and carpark levels, to minimise the volume of subgrade replacement required, thereby minimising the cost impact of the sub-optimal ground conditions, and keep construction progressing.

All services had to consider heritage constraints within their designs (which limits the loss of heritage fabric). The client was keen to preserve as many heritage elements as possible and our structural team worked closely with the client to make this possible, both within the main gallery and the ancillary buildings on the property.

The resulting art gallery has been described as “museum-standard” and will attract shows from around the world. The Northrop team is incredibly proud to have worked on this project, which will make a significant contribution to the community, both locally and beyond. 

Client Name
Richard Crookes Constructions
Construction Value
$6 million

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