4 - Haul Route Response - B14101TL001

25 May, 2015                                 -3-
Our File Ref: B14101TL001
Contact: Steve Williams



Pavement Design Concept
We note that the Concept Design as now represented in the plans has been based on
Councils requirement to provide a pavement design in accordance with the Councils
Planning Scheme Policy 5 Section 3.19 with the minimum overall pavement depth of
200mm.

We note that initial plans included a pavement design that had been based on detailed
analysis undertaken from first principles. As part of the pavement design process we
had initially adopted the following key parameters:
•       Design Life                          -      20 year
•       Design Vehicle Loadings (ESA’s)      -      7.69 x 104
•       Design Subgrade CBR                  -      15%

The result of our detailed CIRCLY analysis and design resulted in an overall pavement
depth of 160mm. We attach the previous detailed CIRCLY analysis for reference.

The design vehicle loading were calculated based on the existing vehicle movements
along Top Forestry Road (based on count data collected as part of our assessment) with
the “worst case” design traffic added to this existing background traffic.

Furthermore, we note that at the time of completing the pavement design we did not
have access to the results of the detailed geotechnical assessment. Subsequently the
Geotechnical investigation has been undertaken and found a subgrade CBR of 11 for
the underlying subgrade material below the existing pavement. We note that the intent
of the design concept is to effectively “build up” the road and make use of the existing
pavement. The geotechnical report has identified that taking this approach and based
on limited excavation of the existing road formation the design CBR could be as high as
CBR20.

As previously noted however, in the interests of working with Council to achieve their
preferred outcome, we note that that our client has accepted the requirement to provide
a minimum pavement depth for rural roads as outlined in PSP5 of 200mm. We note that
we have also assumed a bitumen seal along the length of Top Forestry Road. We have
done a further detailed analysis of the pavement based on the Council pavement depth
requirements with subgrade CBR values of 10 and 12 to demonstrate the adequacy of
the pavement design and attach these for reference.


Ecology Impacts
This is addressed under a separate letter appended to this correspondence. The
primary finding is that while the upgrade will necessitate the removal of some large trees
this is not expected to result in any substantial loss of habitat. It is noted that following
direct discussions with Council Manager Planning & Environment it was clear that a full
and comprehensive “tree identification” survey was not required at this point and Council
was after a more general assessment to identify any potentially significant issues that
may arise that would be a major barrier to any upgrade of the corridor.