BUILD September 2017

28 BUILD / September 2017 , Drill Down Through the Facts Formed in 1982, Stuart Well Services Limited is a leading specialist dewatering subcontractor, offering professional and cost effective solutions to groundwater problems in the UK& overseas. The firm recently received two prestigious awards, the Best in Dewatering & Dewatering Designs - UK&Geotechnical Material Supplier of the Year. Tomark this success, we invited Contract Director DavidWright to profile the firm’s impressive range of work in their major projects such as Crossrail and theMersey Link Crossing. Stuart Well Services Limited employs around 70 staff and has an annual turnover in the region of £12 million. Our firm has a proven track record of successful dewatering and groundwater remediation projects that includes major works such as; Crossrail, Hinkley Point C, UCLH, Sizewell C and the Mersey Link Crossing. Our firm’s work also encompasses numerous other groundwater related projects, ranging from domestic basements, water wells to utility works. With an extensive range of pumps, plant and equipment, we are well resourced and have the capability for response to and the management of a wide range of applications. We have a skilled and experienced technical team to undertake design and estimating, together with a skilled and trained site workforce to carry out works to a high standard and within programme. With depots in Attleborough, Immingham and Birmingham, our firm is able to operate and service sites effectively, throughout the UK. Our firm’s principal areas of work are: Construction dewatering; Groundwater remediation; Pumping tests and; Provision of geotechnical materials. Our firm has ISO accreditation in areas of Quality (ISO 9001: 2004), Health & Safety (OHSAS 18001:2007), Environment (ISO 14001:2004) and Contaminated Land Remediation. This complements our list of industry accreditations, which include UVDB Verify (Achilles) CHAS, FORS and Constructionline. Stuart Well Services are committed to safety, quality and service, having a dedicated HSE manager together with a skilled and trained workforce including NEBOSH, SMSTS, SSSTS, CSCS and National Water Hygiene certification. We are committed to further reducing hazard, risks and improving working practises and actively participate in health and safety initiatives and can undertake site tool box talks. Construction dewatering Stuart Well Services Limited carries out temporary or permanent dewatering works, under a sub-contract agreement to reduce and maintain a groundwater level that enables construction works to be undertaken in dry and stable conditions. We undertake the design, installation and supply of equipment (hire or sale), which includes the provision of RAMS, site records and drawings. We offer supervision and management throughout with servicing of plant and equipment and a 24-hour call-out service. The most common methods used in construction dewatering today are: Vacuum well pointing; Deep wells; Ejector wells; Passive pressure relief wells and; Vacuum well pointing. Wellpoints use vacuum and are installed a close spacings. We typically generate drawdown to 5m-6m in sand & gravels and 3.5m-4.5m in fine sands & silts from working level. To work at greater depths, wellpoints can be installed in stages. Disposable wellpoints consist of 40mm diameter UPVC tubes, with a filter element at the bottom. They are installed using ‘jetting’ method with a steel placing tube, suspended by a 360 excavator. When required, we can install using hollow-stem augur or drilling methods as well as in restricted access situations and manually by using ‘self- jetting’ wellpoints. Wellpoints are coupled by control swings to a horizontal vacuum header main, that in turn is connected to diesel or 415V 100mm/150mm centrifugal or piston vacuum pump(s), to be discharged via a v-notch settlement tank. Deep wells Deep wells are principally used where drawdown beyond 5.0m BGL is required, with drawdown only limited by well-depth and stratigraphy. Deep wells are installed using cable percussive and/or rotary drilling methods typically with an 8”-12” finish, Ø to depths of 10m to 40m depths at 6m to 25m centres. An UPVC well-liner is installed with a designed filter pack and developed prior to the installation of a submersible borehole pump. Individual wells are connected to a common collection main, usually located around the perimeter of the works, for final discharge. Ejector wells Ejector wells are used to depressurise and improve the stability of low-permeability silts and fine sands, where drawdown requirements are greater than ~5m BGL. Ejectors work by recirculating high pressure water (typically 7-8 bar) through the supply and return pipeline (supply 32mm pipe & 50mm return pipe), via a nozzle and venturi in the ejector unit to create a vacuum, inducing water through a strainer and non- return valve. The return water is a combination of supply and CE170036