'P60' Rotary Slope Climbing Rig utilised at Ulley Reservoir, Rotherham

Ulley Reservoir, near Rotherham, was in the news earlier in the year during the summer downpours, when a washout occurred in a spillway at the base of the downstream face of the 130-year old earth-fill dam. The story made the national news, with helicopters monitoring widespread flooding in the area and damage to the dam.  Emergency measures were undertaken for Rotherham Metropolitan Borough Council (RMBC) by contractors JN Bentley Ltd of Skipton (Bentley).  The aim was to contain the washout by blocking the spillway.  Fire Services from many parts of England attended the site to assist in the pumping operations at the time of the emergency, with this role being taken over by Bentley and their sub-contractors once the water level had been dropped to levels deemed safe by engineers on site.

Consulting Engineers Ove Arup and Partners Ltd (Arup) have been advising RMBC from the outset and have recently been appointed to oversee a ground investigation of the dam. This followed an inspection of the dam by All Reservoirs Panel Engineer Jim Claydon, under Section 10 of the Reservoirs Act 1975.

The ground investigation will assist Arup and the Panel Engineer with their assessment of the dam and associated structures and will provide details which can be checked against historical construction records.   Initial results of the ground investigation are due in December 2007 and Arup expect to report their findings to RMBC in early 2008 to help them with the future management of this asset.

RMBC have appointed Geotechnics Ltd of Chester to undertake the site investigation, and works started on site on the 26th November. The brief includes machine dug trial pits, concrete testing on cores from the spillway and the installation of vibrating wire piezometers in the dam face and core to establish pore water pressures. Geotechnics have in turn appointed Geotechnical Engineering Ltd (GEL) to carry out the boreholes using their P60 specialist slope-climbing rotary rig. GEL also mobilised a Terrier rig to dynamic probe to rockhead beneath the existing concrete spillway, and while it was on site it was 'co-opted' to undertake an additional borehole on the dam crest to prove the location and placing of the clay core of the reservoir.

In four days, the P60 rig completed 3 boreholes to depths of between 14.00 and 16.80m, using dynamic sampling to recover a continuous record of the materials used in the construction of the reservoir, and then changing over to rock coring to prove the underlying Coal Measures rocks. Undisturbed (U70) samples and SPT's were taken at regular intervals in all the boreholes. 'P' size casing was drilled in to rockhead to prevent collapse, and vibrating wire piezometers were installed in all the boreholes. Using the P60 meant that no scaffolding or cranes were needed to support a drilling rig on the slopes of the reservoir, and the rig was easily moved between boreholes under its' own power in complete safety.

 

 

 

 

'P60' rig coring on dam slope