Gailey Reservoir Leak Repairs

Civils Penkridge 0.03M 3 Weeks March 2009

Gailey Reservoir Leak Repairs

Gailey Reservoir Leak Repairs

Background

The existing brick headwall / access road of the dam is showing evidence of a significant leak. The exact position of the leak was unknown although the leak does spring up through the existing brickwork spillway downstream of the headwall. The water level in the reservoir was being maintained at a 500mm below normal water level to prevent leakage.

The works had been instructed on the basis of plugging the leak with a puddle clay bung. The extent of the works instructed was a 20m run adjacent to the back of the existing reservoir wall from the wing wall heading north.

The works commenced by grading off the embankment and excavating a short trench along the back of the wing wall and a short length along the side wall. This excavation revealed that the brickwork wing wall is in relatively poor condition in terms of heavy mortar loss and cracking at the rear of the wall. A small void was uncovered running along the back of the brick wall towards the outlet channel at the rear of the headwall.

The brickwork was carefully pressure washed to remove all traces of clay and debris. The water from this operation travelled along the void and began to emanate from the crack in the outlet channel as previously witnessed when the reservoir was full.

The works were amended in that a 300mm thick concrete backing to the existing wing wall was instructed accompanied by grouting to the void. Some minor repointing works were required to the spillway.

Following the repair to the wing wall and spillway the resevoir was reflooded to normal water level. However the water ingress in the spillway resumed. The concrete and clay works had not stopped the leak.

Further dye testing was carried out and it became apparent that the leakage was through the existing brickwork apron. The brickwork was showing signs of substantial mortar loss across its entire length.

It was instructed that the apron be repointed. A temporary clay dam was constructed across the front of the apron in order to dewater the brickwork apron.

It was decided to use an instarmac grout maetrial specifically designed to fill mortar joints quickly and cost effectively without staining the existing brickwork.

The repointing works were completed and the clay dam removed. The repointing was a success and the leak has been stopped.
and were completed on time depsite the additional work required.

Location: Penkridge Cost: 0.03M Duration: 3 Weeks Completion: March 2009