COMHAIRLE CONTAE ÁTHA CLIATH THEAS
SOUTH DUBLIN COUNTY COUNCIL

MEETING OF RATHFARNHAM AREA COMMITTEE

Tuesday, October 09, 2012

MOTION NO. 6

MOTION: Councillor J. Lahart

"That the Manager revisit Orlagh open space adjacent to Orlagh Avenue at times of heavy rain to ascertain why so much surface water seeps off the green during heavy rain onto the Avenue."

REPORT:

The most common reason for the run-off of surface water from an open space during heavy rain is likely to be the result of sub-surface compaction of the soil layers. Where compaction occurs, a layer impervious to water penetration is formed. The most common reason for compaction is a result of heavy machinery working on or with the soil during unsuitable (wet) ground conditions. 

Once compaction has taken place, the capacity of the soil above the compacted layer to hold and drain water deeper into the ground is significantly reduced or blocked entirely. During periods of heavy rainfall, the limited water storage capacity of the soil above the compacted layer is easily exceeded and the surplus rain falling on the ground then runs off under the influence of gravity. 

The solution to the problem is to relieve the compaction and/or intercept the surface water and direct it to a watercourse. The open space will be examined to determine the most cost effective way to relieve the situation. Any works of this nature are normally scheduled for the summer months in order to avoid working on wet ground, in order to minimise the risk of compounding the problem. Any proposed works will be subject to the availablity of the necessary resources at that time to carry out the works.