RFI - Attachment C - Slope Stability Assessment and Geotechnical report · MCU20/0026

Project No. 1-22543                                                                                                           Page | 6
June, 2020
Ref: 1-22543, 2020-05-20, BR SSA VER 1
Sanya Holdings – Slope Stability Assessment and Geotechnical Report - Proposed Residence, 40 Park Crescent, Sunshine Beach




           The provided survey (refer Section 1.6) indicates a fall of approximately 11.5m across
            the site with an RL of approx. 27.5m at the western boundary corner and approx. RL
            16.0m at the eastern boundary corner (refer Plate E3, Appendix E).
           A small concave type feature exists near the centre of the eastern boundary of the site,
            extending into the site by approx. 15.0m.
           An approx. 2.0m wide Council easement runs along the north western site boundary
            from Park Cres to the easement at the rear of the site, understood to be for an
            underground stormwater service.
           Outside of the existing structure, the site is generally well landscaped and grassed with
            several small to medium sized trees and shrubs (refer Plate E4, Appendix E).

The site plan (1-22543-01) in Appendix H, shows an overlay of the provided survey (refer
Section 1.6), as well as the proposed residence location and test locations.

    3.6 Geotechnical Model

            3.6.1      Subsurface Profile

Given access was only available for one borehole at the front of the lot and hand equipment
was used due to the steep slope to the rear of the lot, a combination of drilling and DCP tests
were used to provide an assessment of the competency of the subsurface profile. Therefore,
the subsurface profile adopted from the testing program is summarized below:-

           Fill – Encountered in BH1 to 0.3m depth and in HA2 and HA3 to depths of 0.8m and
            0.6m respectively, and assume din DCP4 to approx. 0.3m depth. It was described as
            Silty SAND (SM) and SAND (SP), very loose to loose.
            In the absence of documentation to confirm that the filling was placed and compacted in
            accordance with AS 3798-2007, then the filling must be considered as being
            ‘uncontrolled’.
           Sand – Encountered in BH1 to total depth of 7.5m, in both hand augers to refusal depths
            of 1.8m (HA2) and 1.9m (HA3), and assumed beneath the fill in DCP4 to total depth.
            Described and assumed (where required) as being generally very loose to medium
            dense, increasing to dense at depths of 7.0m (BH1) and 3.6m (HA2).

A summary of the profiles encountered in the test locations is included in Table 1 with borehole
and hand auger logs and DCP results in Appendix F and the test locations shown on Drawing
No. 1-22543-01 in Appendix H.

TABLE 1             SUBSURFACE PROFILE SUMMARY
                                Fill - Very Hand Auger Consistency based on DCP Tests and
                          (3)   Loose to             assuming Full Sand Profile (m)       DCP Total                            Total
Location        RL (m)                                                                              (4)
                                  Loose      Very Loose to                                Depth (m)                          Depth (m)
                                                            Medium Dense          Dense
                                Sand (m)        Loose
  BH01            27.60         0.00-0.30      0.30-2.00       2.00-7.00         7.00-TD     7.50                              7.50
                                                                                                                                    5
  HA02            18.20         0.00-0.80      0.80-2.20       2.20-3.60         3.60-TD     4.00                              1.80
                                                                                                                                    5
  HA03            17.20         0.00-0.60      0.60-1.90        1.90-TD             NE       4.00                              1.90
 DCP04            20.00         0.00-0.30      0.30-1.90        1.90-TD             NE       4.00                               NA
Notes:-
       1.     NE - Not Encountered; NA - Not Applicable; TD - Total Depth.
                                                        th
       2.     All depths below existing ground level (20 May, 2020).
       3.     RL's based on provided survey data.
       4.     DCP refusal (i.e. blows >20 per 100mm) was not reached.
       5.     Hand Auger refusal.



                                                                                                               SOIL SURVEYS