Hydro G Final report - Kildare.ie

Hydro-G FINAL REPORT
The general flow pattern noted during the site visits is that water discharges from the Spa Well
(monitoring point 9, Figure 4) and drains underground in northern direction towards the two ‘filtering
ponds’ (monitoring points 12-17) which create a small fen wetland on the eastern side of the first
terrace. At the point where the underground drain from the Spa Well surfaces (monitoring point 8),
a man made structure houses a 16” diameter pipe and a loud sound of cascading water was recorded
to come from inside this pipe. A small spring (monitoring point 7) was noted immediately adjacent
to the east of the 16’’ pipe (monitoring point 8). A large deposit of precipitated iron was recorded at
the monitoring point 7. These two water sources (monitoring points 7 and 8) constitute a stream
that flows for approximately 10 metres and then disperses into the wetland area (monitoring points
12-17). There are two distinct ponds here, referred to as Upper and Lower; however, the eastern
side of these ponds (at the Canal’s boundary) remains also waterlogged (monitoring point 18). From
the Lower Pond water flows through a narrow stream (monitoring point 6), splits into two smaller
streams (monitoring points 19 and 20) and flows over the ground into the second terrace. An
underground pipe connects the Roman Bath (monitoring point 5) with either the Lower Pond directly
or with the small stream discharging from it. The Roman Bath is located between (mid-way) the first
and the second terrace. Water outflows from the Roman Bath into the second terrace through a
sluice and then flows over ground into the third terrace. Additional groundwater sources were
recorded at the third terrace and included a big opening in the rock face (monitoring point 3), which
reveals the conduit nature of a very shallow bedrock with groundwater discharge into the site.
Fractures are common in upper horizons of limestone bedrock and this assists discrete distribution of
numerous springs at this level, which flow into and throughout a shallow ‘tufa pond’ located in the
central area. From here, water flows on the surface through numerous small streams and seeps
through the shallow soil. The general high topographic gradient of the site extorts relatively fast flow
rates and this facilitates escape of CO2 from water at all terraces, which in turns causes calcite
precipitation from groundwater. It is apparent though, that although calcite precipitation occurs in
the vicinity of the ‘filtering ponds’ at the first terrace, it is much more abundant at the second and
third terraces where big consolidated pieces of tufa can be found. This is usually associated with
high topographic gradients. At the base of the fifth terrace, water was found in two streams at both
western and eastern boundaries of the site (points 1 and 2). These streams discharge into the river
Rye Water.
3.3. Hydrochemical Analyses
3.3.1. Introduction
Water samples were collected from a variety of monitoring locations in December 2007 and January
2008. However, the 2007 sample results were compromised by laboratory equipment failure.
Therefore, only the January 2008 results could be used. The parameters were chosen in order to
distinguish hydrochemical signatures of analysed water samples. Eight (8 no.) water samples were
collected and the parameters analysed included ions of calcium, magnesium, nitrate, sodium,
potassium, sulphate, ortho-phosphate, chloride, iron (dissolved and total), carbonate, bicarbonate,
alkalinity and total hardness. In addition, Hydro-G carried out a physiochemical monitoring at 23
locations throughout the site. Sampling locations are presented on Figure 4. The analysis was
undertaken along the south - north transect. Field and laboratory data as well as the full
interpretation of hydrochemical analyses are presented in Appendix B. The interpretive summary is
presented below.
Project No.: 07_136 -10-
Leixlip Spa