BUILD September 2017

30 BUILD / September 2017 , inducted water. All water returns to a tank, with the discharge flow being the excess water not used in the recirculation system. In low flow conditions, where a borehole pump has the risk of burning out, ejectors are effective as they can run dry and if effectively sealed and vacuumed can be created within the well and induce flow. Passive pressure relief wells & sand drains Dependant of ground conditions, it is sometimes possible to control groundwater in a confined aquifer below excavation level by installing passive pressure relief wells. Wells installed from a level above the piezometric head and typically backfilled with pea gravel. They act as bleed wells with groundwater in-flow removed by sump pumps. Sand drains act as a hydraulic connection between two aquifers. Typically, upper clay with sand layers and an underlying granular aquifer allow a flow path from the upper aquifer, to a ‘dewatered’ lower aquifer. Groundwater remediation Stuart Well Services Limited has a proven track record in groundwater remediation or treatment projects, either stand alone or as a part of a dewatering system. We undertake a remediation strategy and have an EA mobile treatment licence. Pump and treat is the most common form of groundwater remediation. In simple terms, groundwater is pumped to a water treatment system, from either abstraction wells or excavations. It is subsequently treated, before being pumped to the foul sewer and reinjected into the aquifer, or to a nearby water course with authorisation from the UK’s Environment Agency. The treatment system will incorporate a range of technologies, dependant on a number of factors including the contaminant, its concentration and the clean-up criteria. Typically, groundwater remediation is used where soil and or groundwater contains the following contaminants. • Hydrocarbons; • Volatile organic compound (VOC); • Dense non-aqueous phase liquids (DNAPLS) and; • Light non-aqueous phase liquids (LNAPL). Stuart Well Services Limited has an extensive stock of remediation equipment such as air-strippers, activated carbon units, oil/water separator tanks and sand filters. Together with equipment to undertake soil vapour extraction (SVE), air sparging and bio slurping. Pumping tests We undertake test pumping of boreholes in accordance with the Code of Practice for Test Pumping of Water Wells, BS ISO 14686:2003. Pumping tests are carried out to obtain information to: • Assess the hydraulic behaviour of a well; • Determine the hydraulic properties of the aquifer; • Determine the effects of pumping upon other water sources and; • Established dewatering design. In undertaking a pumping test it should be planned to ensure that the maximum information will be obtained about both the water well and aquifer. • Equipment test; • Step tests; • Constant discharge test; • Constant draw-down test AND; • Recovery test. Stuart Well Services can undertake a complete pumping test service including the drilling of abstraction and monitoring wells, groundwater analysis and report writing. We can also undertake a hydro geological assessment and feasibility studies. Water well drilling Stuart Well Services install water wells routinely on our contract dewatering works and therefore have experience of installing water wells for both commercial and private water suppliers, throughout the UK. We can offer a complete service including application of EA consent including water features survey, drilling of well and pump installation. Borehole decommissioning As well as installing water wells, we are also able to undertake decommissioning of wells, in accordance with the UK’s Environment Agency guidelines. Groundwater monitoring & testing We can provide groundwater level monitoring service either using data logger, where data can be downloaded on site or, vibrating wire piezometers. This is where data can be accessed remotely using a web-site based interface. This system can be enhanced to provide trigger level alarms and, offer a service to undertake groundwater sampling with subsequent laboratory analysis. Geotechnical materials With an extensive stock available for next-day delivery, Stuart Well Services offers a variety of geotechnical materials including: • Well liners – Well casing and well screen available in UPVC, HDPE and steel. PVC liners are available from a nominal diameter of 19mm up to 200mm. • Bentonite & grout products in 25kg bags. • Filter sand - washed, bagged and dried filter materials are available either as natural silica sands or glass media, made from recycled glass. • Sure-Loc riser pipe - for installation of submersible pumps in water wells. • Well covers - daisy covers, square well covers, upright steel covers and PVC flanged well head assembly. The water tight monitoring well covers are BS and EN rated. • Geothermal products - Ground source heat loops (single or double), standard HDPE manifold set-up, pilot weights, glass media and bentonites. All our ground source heat loops are supplied with factory assembled and tested. • Piezometers - Piezometer tip containing a porous element is connected via rigid tubing to ground level. Piezometric pressure at the tip is indicated by the head of water which develops inside the standpipe tubing. • Dipmeters - Tape type meters fitted with audio and visual alarm with sensitivity adjustment potentiometer, complete with reel break. Available in 10, 15, 30, 50, 100 and 150 metre standards lengths.