Hydro G Final report - Kildare.ie

Hydro-G FINAL REPORT
the Intel boundary drain does not currently act as a drainage channel drawing groundwater from the
wet-grassland habitat which has been reported to be drying out. Mitigation measures for this habitat
could include reengineering of the present pipe layout to restore the original discharge from the Spa
Well to the north – north westerly direction. However, this will result in reduction of groundwater
flow towards the cold springs (‘filtering ponds’) and is likely to impact on the local ecology
surrounding the ponds, which have adjusted to present conditions over time. Considering a probable
local recharge of the cold springs, redirection of the groundwater discharge from the Spa Well might
cause an increase in seasonal variation in water levels in the ‘filtering ponds’ area and subsequently
could cause seasonal drying of this fen-wetland. Hydrochemical changes could also occur. Further,
redirection of the outflow from the Spa Well away from the ‘filtering ponds’ will decrease a volume of
water cascading to the 2nd terrace at the eastern side and this will affect distribution of water at
down gradient terraces. This is likely to be compensated by more water flowing on the western side
but is likely to lead to habitat transformations on a local scale. The potential risks posed to the
healthy existing wetland habitat on the east side of the upper terrace suggest that it does not seem
prudent to interfere again with the pipe layout, from a hydrological perspective. The other potential
option for the grassland habitat restoration is to reengineer the ex-parking area south to the Leixlip
Spa SAC. This area currently comprises compacted soil/hard standing surface with a topographic
gradients towards the north and the west. Measures to harvest surface runoff water from hard
standing surfaces and redirect collected water towards the western grassland habitat has potential to
partially re-wet the area. These stormwater design measures are possible and require collaboration
between Hydro-G and other project partners.
With respect to the lowest terrace, which was reported to be drying out, Hydro-G’s investigation has
not revealed any structural changes either in local hydrology or hydrogeology. Therefore, the most
probable cause of these changes is natural habitat transformation resulting from plant growth,
increased evapotranspiration needs and accumulation of organic matter, which has caused an
increase in ground level on this terrace. Cessation of grazing may have contributed to the vegetation
overgrowth of this floodplain. Future ecological characteristics of the floodplain rely upon
management strategies with respect to the plant growth and accumulation of organic matter rather
than management of water flows within the Leixlip Spa site.
Project No.: 07_136 -v-
Leixlip Spa