MCU16.0099.01, RAL19.0036 & OPW 19.0282.01 - Response to Information Request (final) 10.03.2020 · MCU16/0099.01

3        Geotechnical investigation
A geotechnical site investigation was undertaken at specific locations within the investigation area to
collect geotechnical information pertaining to the subsurface conditions of the waterway crossing.
The site investigation comprised:
◼     Three (3) boreholes to a maximum depth of 3.0 m
◼     In-situ testing
Soil descriptions have been determined by an experienced engineer in the field through tactile
assessment and in situ testing.
All aspects of the site investigation were carried out in accordance with AS1728-2017 “Geotechnical
site investigations”. The site work was undertaken according to the Aurecon Health and Safety Plan
and Environmental Management Plan developed for the project. In adherence to these plans, Aurecon
undertook Dial Before You Dig (DBYD) searches for services in the local area. A third-party contractor
cleared each borehole location for the presence of buried services before commencing soil augering.
All test locations were recorded using a hand-held GPS (+/- 5m accuracy) to the UTM GDA94 format.
Ground elevation data was retrieved from the State of Queensland’s Department of Natural
Resources, Mines and Energy online mapping tool “Queensland Globe”.

3.1      Boreholes
A total of three (3) boreholes were augered on the site using a hand auger. Two (2) boreholes were
augered on the western side of the crossing, and one (1) was augered on the eastern side (Figure 5).
The boreholes were backfilled with soil cuttings and compacted upon completion. Bore logs are
presented in Appendix A.

3.2      In-situ testing
DCP testing was undertaken at each borehole location to a maximum depth of 3.0m bgl to assess the
in-situ strength of the subsurface soil profile. DCP testing was undertaken in accordance with AS
1289.6.3.2-1997. The DCP test results obtained at each borehole location are presented in the logs
provided in Appendix A.

3.3      Subsurface profile
The site subsurface profile comprised of topsoil underlain by typically stiff clay soil that increases in
consistency with depth. In BH2 the soil was saturated at 1.9m bgl, and the water would recharge as
the remainder of the hole was being completed. Borehole locations are presented in Figure 5. A
summary of the strata encountered within the boreholes is presented in Table 1.




                                           Project 239146 File 247473 Cooroibah Waterway Crossing_Rev0.docx 2020-02-192020-02-19 Revision A Page 6