Newlands Cross Upgrade EIS - European Investment Bank

South Dublin County Council N7 Newlands Cross Upgrade
Environmental Impact Statement
Arup Consulting Engineers
These figures are out-turn costs and exclude risk items, fees and land acquisition costs.
The following assumptions have been made in developing the construction costs:
• Construction will commence in early 2009 and take up to two years for the overpass and
up to three years for the underpass
• The procurement method for the works will be Design and Build
• No lane rental costs have been included
• No special phasing requirements have been included
• The costs include for construction inflation of 4% per annum until early 2009 and 5% per
annum thereafter
• The costs include the costs of all temporary traffic management
It should be noted that the construction costs presented here represent the main cost difference
between the two options. The permanent and temporary land costs are assumed to be equal as
the landtake is assumed to be the same, even though in the case of the Underpass option, the
temporary land will be required for a longer period.
The principal reasons for the difference in construction costs between the options are:
• The underpass includes for the excavation of a significant quantity of competent limestone
bedrock
• The cost of the retaining structures required for the Underpass is significantly greater that
the cost of those required for the Overpass.
• The cost of the pavement for the Underpass includes a concrete base slab to resist
groundwater pressures
• The longer construction duration of the Underpass option increases the Conractor’s
Preliminaries costs
3.15 Conclusions and Recommendations
In this report we considered two proposed options i.e. Underpass and Overpass, in the context
of their respective construction and operational impacts. A summary of the impacts is
presented in the Options Matrix (See Figures 3.11a – 3.11c).
In summary however, our examination of both options revealed the following issues.
Firstly, there are significant construction issues with the Underpass Option when compared
with the Overpass Option. To construct the Underpass, approximately 6 metres of rock would
need to be excavated, which given the location of the junction, would be a time consuming
and onerous task. As a result of this issue construction of the underpass could take
approximately 1 year longer. This increased duration in turn has a number of knock on effects
with regard to traffic disruption, severance, noise and dust. On a national road of such
importance these issues equate to significant impacts.
Conversely, the Overpass Option has greater operational impacts. Noise levels will increase
slightly at approximately 5 No. receptors. However, this impact can be mitigated back to at
least existing levels. There will also be an increased visual impact with the overpass option
particularly at a number of residences along the northern boundary east of the junction, at
Bewleys Hotel and at the Golf Club. These impacts can also be mitigated somewhat through a
combination of materials selection and landscape design. Following mitigation, the impact
will be moderate and neutral.
December 2007 Page 65