Gwendraith, Wales
March >> August 2003

Site Location:
>> Gwendraith
>> Welsh Water
>>Grundoburst 1000G
Project Duration:
>> 6 months

Gwendraith Capital Project

The Gwendraith capital project consisted of approximately 7 kilometres of sewer upsize. Although the existing concrete pipeline was in good condition the system could not cope with the flows and had been discharging through the combined sewer out falls (CSO) into the river that run adjacent for a number of years. The existing pipeline runs down the valley to the treatment works through heavily ancient woodlands, and areas of special scientific interest. The initial scheme was detailed as an open cut off line replacement which would have had significant effect on both the local ecology and residents of the area. From the outset it beca- me evident that traditional open cut methods were not an option in a large section of the scheme without significant environmental impact.

Part of the scheme passed through a golf course, this resulted in understandable anxiety from club members concerning damaage, however the surface and condition of the fairway is still in its original condition.

The design requirements were that the existing 9" and 12" sewer were to be replaced with 450 mm and 560 mm pipe. A presentation was drafted detailing the location of pits, method of works and proposed solutions which was presented to the Environment Agency(EA), Countryside Council for Wales(CCW) and the local ecological representatives. In addition, it was felt that that a physical demonstration witnessed by all parties would further demonstrate both the capabilities of the company and the significant redu- ced effect of the replacement option on the surrounding area. This demonstration proved to be the deciding factor in the method proposed pulling in over 100 mts of butt welded 560 mm Diameter new pipe in forty five minutes with no damage or disruption caused.

On the strength of the above K'nex were awarded the on line replacement contract through the more sensitive areas of the Gwendraeth Scheme. This involved th replacement of approximately 3 km of main with a contract value of approx £750,000. Due to the environmental constraints imposed by the adjacent watercourses and the local wildlife habitat the scheme was programmed to be carried out through the winter months.
Whilst this provided access constraints these were minimised by the bursting option with plant movements and excavation etc kept to an absolute minimum. The advance investigation works, which included a full 3000 m camera survey and flow monitoring analysis, ensured that we had thought through and prepared for every eventuality.