Hydro G Final report - Kildare.ie

Hydro-G FINAL REPORT
drain (monitoring point 24) was also sampled and showed temperature of 8.34°C and electric EC of
651µS/cm suggesting water originating from surface runoff.
With respect to total dissolved solids (TDS), these were found generally high at all terraces ~700-
1000 ppm and its distribution at different locations is similar to that of electric conductivities.
pH Level
All the sampling locations showed alkaline conditions ranging from 7.15 to 9.48 pH on the 10th of
December 2007 and from 7.29 to 8.74 on the 16th of January 2008. In the Spa Well (monitoring
point 9) the pH was recorded at 7.15 and 7.99 and was relatively low in comparison to other
locations. Subsequently, lower pHs were also found in places linked to the underground discharge
from the Spa Well (monitoring points 8 and 11), where they were measured at 7.27-7.75. The Royal
Canal (monitoring point 10) sample showed pH of 8.25 and the ‘irony spring’ (monitoring point 7)
7.29. In the ‘filtering ponds’ (monitoring points 12-17) pH tended to exceed 8 on both occasions.
Similar pH was found at the entrance to the Roman Bath (point 5) where it was measured at 8.52
and 8.32 respectively. Higher pH in places associated with cold springs supports the hypothesis that
this water originates from the shallow system which is in contact with the alkaline bedrock. At lower
terraces, the pH was generally higher, above 8.
Chloride
Results of the hydrochemical analysis show very high chloride levels in the majority of samples,
which explains relatively high EC and TDS values measured in situ. The highest chloride levels (~350
mg/l Cl) were recorded at the Spa Well (monitoring point 9) and the discharge from the Spa Well
(monitoring point 8). The high chloride level in the Spa Well was expected, following the literature
review. Chloride concentrations decrease in a northerly direction. Samples from the bottom of the
fourth terrace have Cl concentrations of ~ 260 mg/l Cl. This suggest that water collected at down
gradient locations from the Spa Well represent mixing conditions of water coming from the Spa Well
and from other sources (rainfall, surface runoff) that have lower chloride concentrations. Relatively
low concentration of chloride was found in a sample taken from the Intel drain (monitoring point 24)
and was found at 65.94 mg/l. This suggests that water gathered in the ditch collects the rainfall
runoff rather than groundwater that could contribute to wetlands on the site. The high chloride
concentrations within the study site, abnormal for Irish conditions, are associated with water coming
from deeper, warmer rocks, where chloride dissolves from certain stratographies.
Sodium and Potassium
Sodium concentrations on the Leixlip Spa site range from 158-203 mg/l Na and followed similar
pattern to that presented by chloride, i.e. the highest concentration was found in the Spa Well
(monitoring point 9) and these decrease along the south-north gradient. The Intel drain had lowest
sodium concentration (35 mg/l Na) which suggests that water in the Intel drain does not come from
the Leixlip Spa site. Potassium concentrations were relatively stable across the Leixlip Spa site (7-10
mg/l K). Significantly lower concentration of potassium was found in the Intel drain (monitoring point
24, 2.8mg/l K).
Calcium and Magnesium
Calcium and magnesium concentrations were generally similar across the whole Leixlip Spa site. The
magnesium concentration was significantly lower in the Intel drain (monitoring point 24) with
comparison to other sampling points.
Project No.: 07_136 -29-
Leixlip Spa