WET News

14 WET NEWS MARCH 2017 Directional drilling prevents the A38 traffic jam • When a leaking pipe under a busy commuter road needed to be repaired, directional drilling helped alleviate disruption. A n innovative solution involving directional drilling has helped Severn Trent Water (STW) to overcome a leaking main beneath the A38, a busy commuter road near the city of Derby. Over recent years, a number of bursts in the city's Mickleover area had been linked to a troublesome 12-inch trunk main beneath the A38. Having established the problem location, Severn Trent Water faced the prospect of conducting the required repair works beneath the inside lane of the carriageway and the inevitable disruption it would bring to commuters. Bob Taylor, from Severn Trent, and one of the project managers on the scheme, explains: "We knew where the problem was but we really didn't want to have to close the A38 to complete the repairs that were needed. We know how difficult that would have been for local people and anyone commuting into and out of Derby." With some innovative thinking required, a number of options were considered during discussions with contractor partner Morrison Utility Services (MUS), and the decision was taken to conduct a directional drill. The drill would enable the insertion of a new 14-inch diameter plastic pipe under the full width of the dual carriageway, bypassing the leaking section of the original pipe. Access points A joint team was assembled to manage the project, headed up by project managers Bob Taylor (STW) and Robin Coombes (MUS). The feasibility and design for the works was conducted by MUS regional technical manager Chris Harris, whilst Luke Edkins (MUS) was appointed to install the new pipework. The proposed crossing was located to the south of the road's Kingsway roundabout, with the directional drill purposed to cross from east to west, perpendicular to the A38, in itself a challenge as the site included two access points; one from the car park of the nearby Royal Derby Hospital; the other from an access point through council-owned land some 800m from the road. The Bramble Brook stream located to the west of the road presented an additional challenge. A Ground Penetrating Radar (GPR) investigation was undertaken on the road's northbound and southbound carriageways, principally to establish the presence of voiding beneath the road prior to the water main replacement. Borehole one was positioned as close to the proposed launch pit on the east side of the A38 as possible. The borehole progressed by dynamic sampling to a depth of 1m. Soil samples were extracted and the borehole was also monitored for groundwater ingress throughout the drilling procedure. With the directional drill requiring associated vegetation clearance and excavation, independent, specialist ecological consultancy Peak Ecology was appointed to carry out a Protected Species Survey to determine the ecological value of the site and identify any constraints that could affect the works. Great crested newts With habitats within the vicinity deemed critical to great crested newts, badgers and breeding birds, vegetation clearance was supervised by an Ecological Clerk of Works and a method statement produced in relation to great crested newts. The first step of the seven- week programme of works included vegetation clearance, as well as development of the launch and reception pits at each end of the site, with a lagoon to store any potential breakout of drilling fluid. As an additional safety measure, the surplus drilling fluid was removed by vacuum tanker from both the launch and reception pits and transferred to a licensed disposal facility. The drill head used a digitrack F5 locating system, The drill head can be monitored without the need for the operator to enter live roadways or cross waterways ONSITE AsseT MAinTenAnCe

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