Bauer had successfully completed the main works piling for RWE Npower’s combined cycle gas turbine power station at Pembroke several months earlier (GE Oct 2009) and as the turbine
halls started to take shape the focus turned to the delivery and off-loading of the five 400-tonne turbines and the hundreds of smaller items of mechanical plant arriving by ship from Europe. With
the first of a long procession of ships booked for March, the pressure was on to deliver a foundations solution capable of supporting the Liebherr LGD 1750 and its 400- tonne superlift.
The jetty was built in the 1960’s and is constructed of an irregular sheet piled box held together by interlaced tie bars. These mild steel bars have borne the brunt of 50 years of wild Welsh weather
and the jetty was in no condition to support a 100-tonne Bauer piling rig. Tony Gee and Partners were engaged to develop a strengthening scheme that involved replacing the upper
tie bars; an automated monitoring system, supplied by CMCS, constantly monitored the critical sheet pile wall for movement. The ground conditions were highly variable; saturated silts and
sands turning to dense gravels, cobbles and layers of boulders overlying weak boulder clay. This suited the Bauer rotary system, using thick walled casing with tungsten carbide cutting teeth rotated
to toe using Bauer’s powerful BG28 rig. For the marine piles, 1220mm diameter permanent casings, 19mm thick, were fitted with Bauer spec cutting teeth to ensure penetration through the
A 2.5 tonne bespoke piling frame was fabricated to control positional tolerances and provide manned access to the marine piles during construction and due to the large tidal
swing the works were planned around three hour widows during low tides.
“Everything on this project was big, except for the working space” says Carl, “If we got it wrong, we could have a 1.2 million euro piling rig in the sea, and our rigs don’t float!” The risks were
not confined to failure of the jetty structure, although had they inadvertently cut through the uncharted lower tie rods, a possibility with such powerful piling equipment, there was a
real likelihood of catastrophic jetty collapse. The embankments either side of the jetty causeway were steep and one displayed evidence of an earlier slip. The Bauer rig movements and
piling locations had to be pre-planned weeks ahead, the tracks located on large crane mats embedded into the piling platform. Two safety boats patrolled the icy waters around the
jetty, in hourly contact with the Coast Guard. And the whole jetty was bunded to prevent an accidental discharge into the protected environment.
Due to the criticality of the works programme, Bauer worked 24 hours a day, 7 days a week to complete the piling before the first ships departed port in Rotterdam. All the hard work has
paid off as the 1700 tonne crane is now being erected in time for the first of the 200 plus heavy lifts required to build Europe’s biggest gas fired power station.
||Alstom Power Ltd
||BAUER Technologies Limited
||- Mid January to mid February 2010
- 24/7 working
|Bauer's Scope of Works:
||- Construction of a bespoke steel guide frame and access platform for the marine piles
- 14no. 880mm diameter reinforced rotary piles
- 2no. 915mm diameter permanently cased reinforced piles
- 4no. 1220mm diameter permanently cased reinforced marine piles
- Working load tests
- Pile attendances including 2 safety boats
||- 1no. BG28 piling rig