The National Rock Garden (NRG) will be a unique facility on a five hectare site on the shores of Lake Burley Griffin in Canberra. The garden is an initiative designed to celebrate the diversity of rocks that contribute to Australia’s landscapes, culture, history and prosperity.
The Masterplan for the site was developed in 2014, and work is currently underway to enable the preparation of detailed design and costing to implement the Masterplan. The initial work program comprises three geophysical surveys to support a geotechnical assessment of the site as to its suitability for construction of the proposed elements of the Masterplan, in particular the educational pavilion, gallery, entry wall and gorges, which require foundation work and excavations.
As there is no outcrop on the NRG site, there is a need to determine basement depth, regolith material characteristics, and the presence of any drainage channels and groundwater conditions prior to any excavation at the site. The program is being undertaken by Geoscience Australia (GA). The ground penetrating radar survey has already been completed over the entire site on a 50 m line spacing in both NE-SW and SE-NW directions. At the time of writing the interpretation of this survey was underway. The results of this work will be used to design a follow-up weight drop seismic refraction survey to determine material seismic velocity and layer thickness and depths, particularly where the GPR survey may have poor resolution due to thick or near-surface clay layers.
In addition, a passive seismic array is to be installed, which uses sound waves from random sources such as traffic noise and machinery. Although not as controlled as the refraction seismic survey, the receivers can be placed at any location on the site, and does not rely on vehicle access for the weight drop. The resulting information from the three surveys should provide a good understanding of the geotechnical characteristics of subsurface materials, the thickness of layers and geometry of paleo-drainage channels, and the geometry of the bedrock interface.
Progress on the acquisition of specimens for the National Rock Garden has also continued over the past six months, with seven new specimens acquired and delivered to Canberra. Because the construction work has yet to get underway at the NRG site, the committee discussed the storage of the rocks with GA, who agreed to store these at the GA TimeWalk. The rocks were donated by Mr Wolfgang Kraker von Schwarzenfeld, a German citizen who is developing his own Globalstone Project. He has acquired spectacular rocks from each populated continent, and had them placed geometrically in Berlin’s Tiergarten, in an arrangement that represents global peace and harmony. There is to be a mirror specimen of the Tiergarten specimens in a prominent site in each of the countries of origin. The steering committee has agreed that an Australian mirror specimen of banded iron formation can be housed eventually in the NRG.
The specimens donated comprise two banded iron formation specimens and five examples of orbicular granite that originated from the Boogardie commercial granite quarry west of Mount Magnet in WA. All of the specimens are polished on one side. The banded iron formation specimens were initially a single piece from the Mount Tom Price operation. The banded iron formation was initially donated by Rio Tinto, and the orbicular granite donated by the Jones family of Boogardie.
Fundraising has been slow over the previous few months, and this activity will form a major focus for the steering committee for the reminder of the year. The steering committee is looking for people in the geological community who can help this effort by making suggestions for funding activities or identifying potential funding sources. If there are any readers who can assist in any way, please contact me or visit the website to register your interest. Also if any readers are interested in providing ongoing assistance with the NRG funding activity, we are looking for people to contribute ideas on the Finance and Risk subcommittee. Donations to the NRG are tax deductible.