City South CASE STUDY-CITY SOUTH City South is an International business park located two miles south of Aberdeen City Centre alongside the A90, the main arterial route to Aberdeen from Edinburgh. Both City South and the housing estate next to it are new developments. SuDS (Sustainable Urban Drainage Systems) have been integrated into the design of the developments and they share a large detention pond (as shown in the image below): Aerial view of City South business park, the detention pond and A90 arterial route. The failed augur borehole is clearly visible above the directional drilling exit pit Fissured rock at the entrance to the directional drilling borehole Adaptor welded to the reverse of the reamer to support the hole The developer’s plan was to link the detention pond to a public stormwater sewer via a pipe installed under the A90. The first drilling contractor engaged by the client, Dandara Group, opted to use augur boring but the ground conditions meant that this approach had to be aborted. The delay in resolving the problem over several years meant that to avoid the detention pond from overtopping water had been pumped over the surrounding ground. The proximity of the housing estate meant that this was unsatisfactory and Dandara appointed Nicol in March 2017 to complete the project. The project presented several challenges. The new drill path would have to run alongside the original augur borehole with the concomitant risk of fragmentation. The shifting ground conditions were some of the worst Nicol had encountered for many years with shattered and fissured rock, shale and sand along the drilling path. Furthermore, the levels had been set up before the project had started and this left only 500mm of elevation to create a fall over the 110m pipe length. Responding to this challenge using a Ditch Witch JT100 rig the Nicol drilling team ended within one mm of its target. A 22” TCI backreamer hole opener was used to create the borehole. During the subsequent multi-stage reaming the hole frequently collapsed. The failed augur bore meant that the new borehole was frequently awash with ground water which diluted the drilling mud. At one stage, there was a concern that the project may, once again, have to be aborted. One of the solutions to these challenges developed by Nicol was to weld an adaptor to the reverse of the reamer to support the hole as the pipe was pulled through. This proposal was only adopted after extensive risk evaluation. To ensure effective drainage, Nicol also undertook some reshaping of the detention pond. In summary the City South project is a perfect example of Nicol living up to its unofficial motto: ‘We get the job done’. KEY BENEFITS Innovation Nicol fabricated and welded an adaptor to the reverse of the reamer to enable the pipe pull to be completed. This was needed because of the shifting ground conditions and, in particular, the fragmented and shattered rock. The power and control of the Ditch Witch JT100 all-terrain rig was fundamental to the successful implementation of this innovation. Environment The overall aim of the project was to protect the environment by ensuring that the SuDS system, primarily the detention pond, operated as it had been designed to do. Community impact and customer care Completion of the project ensured that ground conditions next to the housing development were stabilised. The pumping of water over widespread areas to prevent the detention pond from overtopping had led to sodden ground conditions. The area is now returning to nature and improving the local environment. Project management Nicol worked closely with the client, Dandara Group, to ensure the project was completed successfully. Detailed risk evaluation was undertaken before the proposed solution (see ‘Innovation’ above) was implemented. Legislative compliance Due to the proximity of housing developments site safety was of paramount importance. All work was undertaken in compliance with relevant legislation, including CDM. The Nicol difference Persistence in the face of adversity. The project had proved too challenging for a previous drilling contractor but Nicol continued to look for a solution to the problem and successfully implemented it. We got the job done!