Appendix E - Wastewater Report

                                             PROPOSED RESIDENTIAL SUBDIVISION
                                             9A JIRRIMA CRESCENT, COOROIBAH

6.0             SUBSURFACE INVESTIGATION FINDINGS

6.1              Regional Geology
Published geological information 1 indicates that the soil profile at the subject site consists of predominantly
residual soil derived from the Triassic to Jurassic aged, Tiaro Coal Measures (Jdt (w)). This formation
typically comprises weathered lithofeldspathic labile and sublabile to quartzose sandstone, siltstone, shale,
coal, ferruginous oolite marker quartzose sandstone, siltstone, shale conglomerate, coal. Alluvial clay, silt
sand and gravel may also overly the western end of the site. An extract of the geology map is shown in Text
Figure 7 below.

                                                                               Jdt (w) - Tiaro Coal Measures

                                            Qa-SEQ                             Age         Triassic - Jurassic

                                                                                           Weathered lithofeldspathic labile
                                                                                           and sublabile to quartzose
                                                                               Lithology
                                                                                           sandstone, siltstone, shale, coal,
                                                                                           ferruginous oolite marker
                                                                               Dominant
                                                                                           ARENITE-MUDROCK
                                                                               Rock
                                                       Jdt (w)
                                                                               Qa-SEQ – Tertiary Basalt

                                                                               Age          Quaternary

                                                                                            Clay, silt, sand, gravel; flood plain
                                                                               Lithology
                                                                                            alluvium

                                                                               Dominant
                                                                                            ALLUVIUM
                                                                               Rock

Text Figure 7: Extract of Geology Map with Annotations by Tectonic

6.2              Subsurface Conditions
Subsurface conditions encountered in the borehole generally supports the mapped geology for the site,
comprising:
             Stiff clayey silt with some organic fines (topsoils) to depth of 0.3 m BGL; overlying
             Very stiff to hard silty clays to borehole termination at 1.5 m BGL.


The soil profile is considered primarily residual soil, derived by the weathering of the parent formation (Tiaro
Coal Measures).

Groundwater was not encountered in the completed borehole. It should be noted that ‘perched’ groundwater
seepage may develop at the interface between upper silts and underlying clays (0.3 m BGL) following
periods of heavy or prolonged rainfall.
For detailed descriptions of the soils encountered in the borehole, refer to the borehole report and
explanatory notes attached in Appendix A.




1
    State of Queensland, Queensland Globe Geology Map, 2017



4 November 2020
Report No. 20333-001-Rev0                                        5