Newlands Cross Upgrade EIS - European Investment Bank

South Dublin County Council N7 Newlands Cross Upgrade
Environmental Impact Statement
14. SURFACE WATER AND DRAINAGE
14.1 Introduction
This chapter describes the potential impact of the proposed Newlands Cross upgrade on local
surface water resources. The N7 Newlands Cross Junction is located between two of Dublin’s
river catchments; the Camac River and the Dodder River. The majority of road runoff on the
N7 and the Belgard / Fonthill Road (R113) drain to these two catchments. Ballymount Park
in close proximity to the junction contains a surface water drainage system that drains to the
Camac River. The Poddle River is a significantly smaller system that flows between the
Camac and Dodder catchments and is located in close proximity to a portion of Belgard Road.
Arup Consulting Engineers
At the existing Newlands Cross Junction the eastbound N7 and the Fonthill Road drain
directly to the Camac River. The westbound N7 and the adjacent section of the Belgard Road
drain to the Ballymount Park watercourse and subsequently the Camac River. The southern
sections of the Belgard Road primarily drain to the Dodder River. Figure 14.1 indicates the
local surface water catchments.
The assessment of the proposed upgrade takes cognisance of the following:
• Drainage: the impact of the proposed upgrade on river flow and flooding;
• The aquatic environment: designated conservation areas associated with each catchment,
aquatic and riparian habitats and fisheries value;
• Water Quality: biological quality.
14.2 Methodology
Background information on the local surface network was reviewed from previous surveys,
including the M50 Upgrade Environmental Impact Statement 1 . Information was also obtained
from the National Parks and Wildlife Service. EPA water quality reports for the Camac and
Dodder Rivers were reviewed to obtain the most recent water quality status of local surface
water features. The Greater Dublin Strategic Drainage Study 2 was also reviewed for
information. The suite of Eastern River Basin District Reports 3 published to date, were also
reviewed for information. The local surface water network at Newlands Cross was also the
subject of a site visit.
14.3 Existing Environment
14.3.1 Existing Road Drainage
14.3.1.1 Culverts and Bridges
There are no culverts or drainage related bridges located within the boundaries of the
Newlands Cross scheme.
14.3.1.2 Carriageway Drainage
The road surface water drainage at Newlands Cross is currently provided by a system of kerb
and gullies, feeding into a network of carrier drains.
14.3.1.3 Outfalls
The existing N7 through the Newlands Cross area shows a constant fall longitudinally towards
the M50 in the East. The N7 mainline drainage network extends towards Newlands Cross
from the Boot Road overpass, for approx 1.2km. East of Newlands Cross, the eastbound verge
December 2007 Page 221