Response to Information Request - REC13/0015

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Incidents    ::   Bioretention systems not installed correctly                                                   ::                                     ::

             ::   Sediment builds up on the surface of systems.

             ::   The vegetation dies off.

             ::   Pondage of water is in excess of one hour.
             ::   Erosion occurs.

             ::   Pondage of water occurs at every minor rainfall event.
             ::   Weed growth occurs.


Corrective   ::   Contractor to amend installation to ensure it complies with Operational Works drawings.        ::       Contractor                    ::   As required
Action
             ::   The Contractor will check up stream sediment control and fix failures. The sediment build up
                  will be shovelled off the non-woven geotextile of the Bio-Retention Systems. The geotextile
                  will be replaced at the beginning of the defects liability period

             ::   Unsuccessful plantings will be replaced as required. A normal allowance of 10% should be
                  made for unsuccessful plantings. Ensure watering rates are adequate and increase if
                  necessary.

             ::   Replace geotextile where used, check and if necessary replace sand media with coarser
                  sand. Check that slotted pipe is not blocked and outlet free draining. Replace and repair
                  where necessary.

             ::   Erosion should be repaired and investigate measures to reduce erosion e.g. install rock
                  spalls upstream of the erosion so as to dissipate the flow across a broad area.
             ::   Dominating weeds should be removed by hand and taken to the Council’s Refuse Centre.
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                                             Operational Phase

Objective    The Council is to include the Bio-Retention Systems into their maintenance program.


             Description                                                                                         Responsibility                         Timing

Actions      Inspect Bio-retention systems every three months for first year of operation to determine           Contractor                             Three monthly
             maintenance requirements.