Hydro G Final report - Kildare.ie

Hydro-G FINAL REPORT
2. Desk Study
2.1. Environmental Settings
The Leixlip Spa site is located on the Leixlip-Maynooth local road R148, approximately 2km west of
the Leixlip town centre. The R148 constitutes the site’s southern boundary and an access to the site
is also provided from this road. The site is adjacent to the Intel Ireland factory, which is to the west,
and the eastern boundary runs along the Royal Canal. To the north, the site is bounded by the river
Rye Water. The site location map is presented in Figure 1.
2.1.1. Geological Settings
The bedrock geology underlying the site is discussed in the GSI publication “Geology of Kildare -
Wicklow, (McConnel et al., 1994). The 1:100,000 scale bedrock geology map for the area (Sheet 16)
indicates that the subject site is underlain entirely by rocks of Calp Limestone Formation (CD), which
was formed during Chadian age and belongs to Lower Carboniferous system (refer to Figure 2).
During the Carboniferous period, the eastern part of Ireland underwent uplift and erosion after which
there was a period of subsidence in the area. Throughout this time, the sea invaded the land
allowing marine sediments to accumulate across most of the Sheet 16 map, including Leixlip. The
Calp Limestone is a muddy limestone and was deposited in thick sequences in turns with muds in
deep sea basins with a limited fauna. It consists of dark grey, fine grained, graded limestone with
interbedded black, poorly fossiliferous shales. In later periods, subsequent erosions reworked the
upper end of the Calp and overlying younger limestone deposits allowing for localized karstification
(in places where the rock was temporarily exposed) and/or for deposition of granite boulders within
the Calp.
There are number of faults in this area. These are predominantly in an east-west direction. One of
these faults runs in close proximity to the site, along it’s southern boundary, Figure 2.
With respect to overlying strata, the majority of this area is covered by till of sea origin and derived
from limestone and overlain with Grey Brown Podzolics and Gleys (Gardiner, 1980). The GSI (GSI,
2007) reports these deposits to be less than 3m deep west of Lucan village and the groundwater
vulnerability rating, which classifies this area as ‘high’ vulnerability, suggests depths to bedrock of
approximately 3 - 5m.
2.2. Hydrogeology
2.2.1. Aquifer Characteristics
According to the GSI Groundwater Body description (GSI, 2007), the Leixlip Spa Site is underlain by
the Dublin Groundwater Body, which generally is low permeability and the majority of groundwater
flow occurs along faults where permeability is increased by dolomitisation of the rock. The majority
of flow occurs close to the surface and in isolated fractures at depths of up to 50m below ground
level (bgl). Relatively low permeabilities deem this bedrock to be of limited development potential
and therefore the Geological Survey of Ireland classified it as Locally Important aquifer, with
moderate potential in local zones only. Groundwater yield potential is therefore highly dependent on
Project No.: 07_136 -4-
Leixlip Spa