Newlands Cross Upgrade EIS - European Investment Bank

South Dublin County Council N7 Newlands Cross Upgrade
Environmental Impact Statement
NTS5. TRAFFIC AND TRANSPORT
Arup Consulting Engineers
The purpose of this transportation assessment is to quantify the effect of the proposed scheme
in terms of its operational performance, value for money and its effect on the transport
network in Dublin. The steps in the process were traffic data collection, preparation of an
existing (2005) area-wide traffic assignment model, preparation of forecast Opening Year and
Design Year models, and preparation of LINSIG capacity model of the N7 / R113 junction
proposals in order to test the junction layout.
The scheme developed for Newlands Cross is based on a grade separated interchange – with a
free flow N7 passing over an at-grade R133 / N7 slip roads junction. The at-grade layout
consists of two adjacent signal controlled junctions, which will operate as a single entity to
ensure co-ordination of signal timings and hence movements through the junction.
Capacity analysis was undertaken which indicated that without the scheme in place (the Do-
Minimum scenario), significant delay and congestion is forecast to occur. With the scheme in
place (Do-Something), the at-grade signal controlled junction has appropriate capacity to
ensure that queuing does not occur on key links (eg. N7 off-slip roads, R113 link across N7
mainline). N7 through-traffic will operate under ‘free-flow’ conditions and will not be
affected by operation of the R113 / N7 junction.
The cost benefit analysis for the Newlands Cross scheme proposals demonstrates clearly that
significant economic travel benefits would accrue from the proposed Scheme, by far the
largest element of the benefits being the value of the time savings resulting from the reduction
in traffic congestion on the network.
The impact of construction traffic will not be significant when compared to the levels of
general vehicle traffic at the junction.
NTS6. SOILS, GEOLOGY AND HYDROGEOLOGY
Newlands cross junction is located in an area underlain by man made fill, glacial drift deposits
and limestone bedrock. An understanding of the sub-surface conditions was built up using a
scheme specific ground investigation. This information was supplemented by desk study
information gathered from public sources including the Geological Survey Ireland, Ordinance
Survey Ireland and the Environmental Protection Agency.
Impacts predicted for this development include potential contamination of soils and
groundwater / bedrock aquifer during construction and operation, the excavation of surficial
and rock deposits, disposal and reuse of excavated material, and the compaction of sub-grade
materials.
Mitigation measures include appropriate controls and working methods to prevent spills and
dust generation from plant/tanks, appropriate profiling, falls and drainage of earthworks
operations to promote safe run-off, appropriate foundation construction techniques to
minimise noise, vibration and soil/groundwater contamination, maximum reuse of excavated
material where appropriate, minimum handling and suitable storage of soils intended for
reuse, and capping of placed fill material to minimise dust generation and dermal contact.
If the recommended mitigation measures are followed, it is anticipated that there will be no
significant residual negative impacts on the soil, geological or hydrogeological environment.
December 2007 Page NTS5