Viridian III Technical Specification OPW1 [As Published] · 142008.256

                                                                        VIRIDIAN III - Landscape Works

4.      STORMWATER DRAINAGE


4.1     SUBSOIL DRAINS

4.1.1   GENERAL

Subsoil drainage shall be constructed in accordance with the Drawings and will be ultimately
in accordance with the site engineer’s recommendations and or drawings.

Unless specified otherwise, subsoil drainage trenches shall incorporate geotextile material
lining the trench. In areas where the natural soil could cause blockage of the geotextile
material and the ultimate failure of the Subsoil Drainage system, the Builder may advise the
following if applicable.

The trench shall not incorporate geotextile material.

Alternative subsoil drainage backfill material (in accordance with this specification) shall be
used.

No construction equipment shall stand or travel directly on subsoil drain material or
constructed drains without approval.

Minimum cover for various compactors over the drain shall be unless approved otherwise:

        Hand Held Units       100 mm

        Units <15 Tonnes      200 mm

        Units >15 Tonnes      300 mm

All subsoil drainage shall be connected to the stormwater drainage system.



4.1.2   MATERIAL REQUIREMENTS

Trench backfill material shall be crushed or granular material that conforms to the grading
requirements shown below:


                  AS Sieve Size (mm)             Percentage Passing By Mass
                                                 Column 1
                  19.0                           85 - 100
                  9.5                            0 - 20
                  4.75                           0-5
                  1.18                           -
                  0.30                           -
                  0.15                           -
                  0.075                          0-2

Column 1 backfill material may be used in trenches either incorporating geotextile material
or not incorporating geotextile material. This material is consistent with the requirements for
a 20 mm concrete aggregate in accordance with AS 2758.1 - 1985.




EDAW Aust                              Page 13                       February 2008