Attachment 5 - Geotechnical Assessment · MCU18/0015

 

RTI 11/055 Folio B399

 

November 2003 -15- 03632248-001

 

7.5 Drainage & Erosion Control

In general, site drainage should be designed to readily remove surface water and to prevent
ponding of water on subgrade areas during construction and also adjacent to foundations and
perimeter slabs once construction is completed. ,

Erosion can be prevented by minimising vegetation disturbance and by avoiding concentrated
high velocity surface water flows by localised grade control and collection of roof runoff in
holding tanks. Also, average gradients of finished surface profiles should not be made steeper
than the existing surface.

To minimise site erosion and maintain stability of slopes after completion of construction, it is
recommended that the denuded banks of the creek should be revegetated. The investigation
results indicate that groundwater seepage may be encountered‘in areas.along and above the
creek banks following periods of heavy or prolonged rainfall.

Excess stormwater collected from the site (eg. tank. overflow) should be directed by pipes to
an engineer designed dissipation structure(s) located within the creek.

As a precautionary measure to prevent instability ofthe creek bank, a subsurface cut-off drain
is recommended along the up slope. side of proposed Cabins 1A, 2A and 3A. The cut-off
drain should penetrate into the upper intetface of the inferred residual clay underlying the
colluvium. It should be noted that this drainvis not required for long-term stability of the
proposed structures, whiclwill be supported by footings designed to resist lateral forces, but
is a precaution to prevent. slumping and. erosion of the creek bank. Golder Associates should
review the design of the drain)

7.6 Construction Management

It will be necessary to implement a Construction Management Plan (CMP) for the proposed
development. The CMP should include control measures for each component of the proposed
construction works to maintain stability of the sand dune in compliance with the
recommendations of this report. Golder Associates should prepare relevant parts of the CMP
or review the document prior to finalisation.

Golder Associates