1. Introduction
Alpha Archaeology Pty Ltd (Alpha) is working with the Archaeology and Anthropoloical Society of Victoria (AASV) to carry out a geophysical survey of the Viewbank Homestead, Heidleberg (Map 1). The aim of this survey is to assess the extent of the boundary for the homestead tip site. An EM survey was performed to measure the resistivity of the ground as well as the induced current.
1.1. Location and Description of Study Area
The study area is located in Heidleberg, Victoria (Banyule City) and is currently a heritage listed area. The area is used as a recreation park and the plenty river trail crosscuts the park. The homestead is positioned on the junction between the Plenty River and the Yarra River.
On the property the homestead has been identified, the footings of the house, garden terraces and some plants still survive. It is possible that terraced areas to the south and east of the house are locations for cellars, stables and servants quarters. Rubbish tips located to the east of the homestead have also been identified. The purpose of this paper will be to identify the size, number and boundaries for the rubbish tips.
Global Positioning System coordinates defining the boundaries of the study area are given in Table 1
Table 1: GPS coordinates defining the study area for the Viewbank tip
Corner of the study area / Easting / NorthingNE / 332160.9 / 5820498
SW / 332112.3 / 5820477
NW / 332110.8 / 5820492
SE / 332164.1 / 5820469
Map 1: Location of Study Area
2. Background
The Viewbank homestead is a respectable residence. The Viewbank residence was originally settled by Edward Willis in 1839. The final owner of the Viewbank Homestead was Dr. Robert Martin, who undertook extensive renovations and alterations to the original house. When Dr. Martin passed away there was no heir to the property. In the 1920s it was sold to the Bartram family, where the house was demolished. The property is now owned by Parks Victoria (Smith 2001).
Robert Martin was borne in Skye, England in 1978. His early life before moving to Australia is not well known. In 1839 he migrated to Australia where he owned a number of stations and properties before moving to the Viewbank residence. It is unknown when he lived at any of his four properties. Martin’s wealth makes the Viewbank residence an interesting insight into the lifestyle of the upper class during the late 19th century in Melbourne. (Kenyon & Billis, 1974).
There have been extensive studies completed on the Homestead, and much of the architecture of the building has been mapped (Figure 1). The area was geophysically mapped in 1996 by Heison et al, using a variety of techniques including GPR and resistivity methods. This survey covered the whole area identifying the main tip site which will be covered in this survey.
Previous studies of the homestead have been completed. Sarah Hayes catalogued in excess of 20,000 artifacts from the area. However there has been a lack of suitable reports which have been produced.
Figure 5: Floor plan: Viewbank Homestead
3. Geophysical methods
To identify the bounds of the tip area a geophysical survey was conducted. Using an EM31 geophysical device it was possible to measure the conductivity of the ground as well as detect magnetic objects. The device creates circular eddy current loops which induces a magnetic field which is proportional to the conductivity of the ground. The conductivity is determined by looking at the quadrant-phase component. The inphase component is more sensitive to metallic object and can be used to determine the presence of buried metal objects. The conductivity of the ground can be used to identify variations in the composition of the underlying ground. EM surveys have been used in the environmental industry to identify the boundaries of decommissioned tips.
The results were collected in a grid pattern with lines every four meters from the center and readings taken every two meters. The area near the known dig site had line spacing of two meter. Where anomalies were identified during the initial survey smaller lines were followed to refine these data points. This pattern was chosen to gain the highest spatial resolution possible within the time available for completing the survey. All data points are marked with a small cross on both Figure 2 and Figure 3.
4. Assessment of Geophysical results
Figure 2: Inphase component (metallic object detection) for Viewbank homestead
The inphase components indicate that there is a significant anomaly around the known tip site. At some points the values changed depending on the orientation of the boom. At these points it is highly likely that there are pieces of metal rubbish such as horse shoes, flower tins and other cans. The magnetic object detection is a very good way to identify some of the waste which would have been produced by the household. These measurements will not identify nonmetallic waste such as china, burnt objects and any waste produced by renovations or modifications to the house.
At some points within and near to the tip site there were local anomalies where the inphase component was different depending on the orientation. These locations have been mapped on Figure 2 as red crosses. To be classified as a significant change the anomaly must have varied by ±.3 which is approximately 10% of the lower values recorded. These local anomalies are most likely influenced by the geometry of the objects which are buried. However it is also possible that they are not related to the Martin settlement and are a result of the Bartram farm as there is a fenceline running very close to the known tip site.
Generally the conductivity values are a good indicator for the boundaries of modern tip sites. However the result of the conductivity survey (Figure 3) does not show any anomalies over the known tip site. There are no variances between the conductivity of the tip site and the surrounding ground. However it is possible that the low in conductivity seen near the known tip and to the east of the tip is influenced by the burning of rubbish which was commonplace during this period.
Figure 3: Conductivity readings from the Viewbank homestead area
As the results from the conductivity survey did not indicate a viable tip site the inphase component was primarily used to identify a target location. The main anomaly is identified and a suggested dig site is highlighted in Figure 4. The area mapped out is approximately 4mx15m. This is consistent with the reports from the previous geophysical survey.
Figure 4: Suggested dig site
5. Conclusions and Recommendations
Due to the strong geophysical response seen from the inphase component it is recommended that the area showing a distinct boundary be investigated. If more resolution is required prior to excavation it would be appropriate to use a GPR survey to further define the geometry of the tip site. A GPR survey would also allow the depth to be constrained. Due to time and funding constraints a GPR survey was not conducted, the EM31 survey providing adequate information for the community dig to occur.
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