Wallers Haven Study, East Sussex, UK, 2003
[South East Water]
The aims of the study were: (i) to gain a detailed understanding of the water resources of the upland catchment of the Wallers Haven; (ii) to assess the impact of the Haven’s augmentation from boreholes, on the Pevensey Level wetlands, a designated SSSI. Since the 1950's wells in the catchment were used to augment summer streamflow and public water supply abstractions.
The main questions tackled by the study were: Have the flow augmentation and river abstraction reduced the surface and groundwater flow reaching the Pevensey Levels? What is the natural and altered flow regime? Should the present method of calculation of abstraction be revised?
Independent GIS-based models were made of both the surface and groundwater systems, to determine elements of the groundwater flow system. The main conclusion was that although the impact on summer low flow was positive, deep groundwater outflow was so large in relation to amount abstracted for augmentation that ecological impacts would be minimal, as augmentation results in a net annual gain in flow into the Pevensey Levels.
Cockhaise Groundwater Study, Sussex, UK, 2003[South East Water]
The primary aim was to assess the yield and deployable output of an Ashdown Beds and Tunbridge Wells Sandstone [TWS] groundwater source in the headwaters of the Sussex Ouse, as part of abstraction licence review. At Holywell-Cockhaise, an ancient Chalybeate spring had been exploited for public water supply, using an elliptical large diameter well chamber. The footing of the chamber sits on the Ardingly Sandstone [TWS].
The Chloride mass balance technique was used to estimate recharge using rainfall at Barcombe Mills characterized by 7.06 mg/l Cl. The mean groundwater Cl from all Holywell data was 19.9 mg/l and it was shown from geochemical plots that this is overwhelmingly derived from marine aerosols. Streamflow averages of 19.9 mg/l Cl from a nearby site suggest that baseflow predominates and that the groundwater Cl signal is derived by evapotranspiration. Mean recharge rate was found to be 269 mm/yr.
An aquifer test was carried out in 2003, which involved pumping out the well chamber at variable rates, and the drawdown results provided a good basis for assessing performance of the well. The dry year average Deployable Output was calculated using both new and historical records, and the long-term yield of the existing well/spring was estimated to be 1.5 Ml/d.
Lasham Groundwater Yield Assessment, 2003[South East Water]
Deployable Output assessment of Lasham groundwater source involved re-assessment of the multiple well source at Lasham, near Alton, in Hampshire, using new pumping test data, and advanced step test analysis, using WRA’s software, PtFit, which has been developed for analysing pumping tests at multi-well sites. It can cope with multi-well pumping, complex pumping regimes and automatically determines the well–loss factor which determines well step drawdown behaviour.
The Lasham source comprises three separate well configurations: one with two interconnected wells, and two distant individual wells, 300m and 560m away from the main site. On the main site, wells are 1800mm in diameter, drilled to a depth of 90 mbgl, and connected by a 91m-long adit at 27.7mbgl. The other two boreholes are 762 and 914mm in diameter drilled to a depth of 91 to 97m.
Step-Drawdown tests were carried out at all three sites, and software used to analyse the results. Having determined aquifer and well performance characteristics, deployable output was calculated for the required multi-well pumping regime assumed, following UKWIR methodology.
Well performance was shown to have deteriorated since prior testing in 1988, and the well-loss factor had increased. Acidisation was recommended along with a new pump delivery system. Subsequently, Stow plc was contracted to carry out this work and well retesting showed that performance was restored to pre-1988 levels.
The calculated DO, assuming wells 1 or 2 provide first delivery, give a yield of 12.5 Ml/d: If well 3 and well 4 are pumped continuously at half the rate of wells 1 and 2, the DO exceeds 30 Ml/d.
Pembury Springs Investigation, 2004[South East Water]
Pembury springs has been the main water supply for the city of Tunbridge Wells in Kent since the mid-1800’s. The aim of the investigation was to identify ways in which the winter abstraction from the aquifer could be controlled without detriment to the streamflows occurring during the summer.
The hydrogeology of the principal aquifer, the Lower Tunbridge Wells Sands, was studied, HYSIM modelling to relate daily rainfall to springflows, examination of surface flows, and ecological surveys of the two main streams, Tudeley Brook and Alder Stream. A detailed survey and inspection was also made of all the individual spring locations, tunnel, adits and catchpits and V-notch.
The chloride mass balance technique was applied to determine the regional recharge rate, and complete the water balance calculations.
A survey was made of the condition of the tunnel joining springs in the Tudeley catchment with spring-flow in the Adler catchment, noting the presence of leakage, and carrying out flow measurements. As the tunnel is built through the aquifer, the tunnel both gains flow from fractures as well as losing water through the broken clay-pipe aqueduct. Five work components were carried out: groundwater modelling, revisions to the abstraction licence, field monitoring of spring flows, applicability of the chloride mass balance technique, and engineering refurbishment options for the spring system.
Nutfield Marsh Hydrogeological Appraisal, 2007 [Nutfield Marsh Residents Group]
A study was made of sand extraction at Mercers Farm, Nutfield Marsh [east of Redhill] to support a local residents group in questioning the viability of proposals in the Draft Surrey Minerals Plan for the period 2004-2016, and investigate the potential impact on public water supplies.
WRA’s task was to carry out an appraisal of past and proposed quarrying activities in the Redhill area. The surface-groundwater regime of the Nutfield Mineral Planning Consent area is complex due to the extensive history of mineral workings in the area, in particular, for sand and Fullers Earth.
The Surrey Minerals Plan [SMP] recognises that the hydrology and restoration of quarried areas are key issues in the selection of sites. At Nutfield, consideration was given to the potential impact on groundwater resources and possible contamination of the site. It was found that Sutton & East Surrey Water’s groundwater source at Brewer Street would most likely be affected by the proposals, although contradictory mapping of EA source protection zones highlighted the need for further evaluation, before the County Council finalised the new Minerals Plan.
Pinfold Groundwater Development, 2008-2011 [Bedford Estates, Woburn]
The project included planning studies, preliminary drilling investigation and monitoring, construction of test and production boreholes and delivery system of the new water supply for irrigation of Woburn Golf Club’s three 18-hole championship courses.
Water level monitoring was carried out to provide baseline data for the aquifer pumping tests. The new production well captures water from the area of the Woburn Sands draining into the Thames Basin, which falls outside the CAMS defined catchment of the Broughton Brook. The work included the process of abstraction licence application and associated surveys.
The aquifer at this location is semi-confined with downward leakage, resulting in a transmissivity of 35 to 50 m2/d and 0.0035 storage coefficient. The well required extensive development, including high velocity jetting. The aquifer test data were highly influenced by barometric pressure and were corrected using a multiple regression technique prior to analysis by different methods using AquiferWin32.
GMDL drilled eight small diameter boreholes for installation of piezometers in the Woburn Sands aquifer, in order to investigate the depth of groundwater along the Broughton Brook. This work formed part of the groundwater development programme and Water Strategy project for the Bedford Estates.
Nitrate Vulnerable Zones [NVZ], 2009[Moundsmere Estates, Waterfield and White]
Hydrogeological assessments were made for farms across the Oxfordshire, Buckinghamshire and Hampshire counties, to provide support for appeal against the extension of the NVZ boundaries. A number of hydrogeological reports were prepared, to assist farmers in southern England to appeal against the revised designation of nitrate vulnerable zones [NVZs].
The NVZ is an area of surface water or groundwater that has, or is at risk of having, a high nitrate concentration [>50mg/l NO3-N]. In order to combat nationally-increasing trends of nitrate, farmers within a NVZ must reduce their nitrate input to land, by limiting application of livestock manures and by observing closed periods for the application of organic manure.
NVZs were established by the EC in areas where agricultural nitrates pose a pollution risk, and are designated by the Environment Agency using best available data, but information is not necessarily adequate across all parts of the country. In 1996, 66 NVZs were identified to protect drinking water sources, amounting to 8% of England’s land area, and this was increased in 2002 to cover 55% of England. In 2009, the NVZ area was increased still further, bringing the total cover to 70% of England.
The appeals were based on evidence to demonstrate that the farmland does not drain into water identified as nitrate-polluted, and/or the water to which the land drains should not have been identified as polluted.
Following an examination of the topography, soils, geology and groundwater movement to public water supply boreholes, the WRA reports for each farm provided hydrological justification for excluding specific areas from the new NVZs. The reports demonstrated that farm runoff did not drain into a problematic high-nitrate river, and this constituted the main grounds for appeal.
Barlaston Mineral Water Study, 2010[John Sanders Farms Ltd]
Barlaston is a small village in Staffordshire [England], located on a hill overlooking the valley of the Upper Trent. An area of groundwater springs was assessed to determine the feasibility of developing a bottled groundwater supply, based on capture of the spring water, which flows into the Hartwell stream.
The underlying geology is Sherwood sandstone at lower elevations, and Keuper marl and Keuper sandstone at higher points in the catchment, with Upper Coal Measures outcropping to the north-east of Barlaston. The sandstones form a significant regional aquifer, and groundwater provides significant baseflow contribution to the local streams.
The WRA assignment assessed the feasibility of developing a bottled water at the proposed spring, including a broad review of regulatory matters and hydrology:
- Review of Environment Agency regulatory constraints
- Hydrogeological and water quality assessment, to assess the yield of the spring, and hence water volume available for abstraction
- Assess physical conditions at the site, and identify the engineering and costs that would be required to develop a safe and sustainable capture system for the bottling plant.
Soho Farmhouse groundwater investigation, Cotswolds, UK, 2014[Soho Group]
Soho Farmhouse is an old farm on the Great Tew estate which was the subject of conversion into a modern country club retreat. The Soho studies focused on both deep groundwater for potable supply taken from the Marlstone Rock Bed and shallow groundwater in the Chipping Norton limestone and Clypeus Grit Formations. The work involved water features survey and abstraction licencing considerations, pump testing existing wells, yield analysis and design of potable supply boreholes and monitoring.
Activities also involved a flooded farmhouse basement area with four rooms requiring dewatering, and an intricate network of old wells, catchpits and drains. Fluorescein was carefully injected at key points in the drainage system to trace interpreted links between various catchpits and manholes, and the river system. GMDL provided the on-site pumping and testing equipment.
Briary Lodge Private Water Supply, Midlands, UK, 2016[Jackson-Stops Estate Agents]
Briary Lodge was a disused farm at Lillingstone Lovell in Northamptonshire, in a shallow valley at the head of Deanshanger Brook, a tributary of the Great Ouse.
The primary objectives of the project were to assess the feasibility of obtaining groundwater in sufficient quantity and quality for potable supply, and prepare the preliminary design for costing of a private water supply scheme of up to 20 m3/day.
The work involved Acquisition of data, Reconnaissance and measurement, Hydrogeological analysis and yield assessment, Procurement of drilling contractors and evaluation of quotations, Preliminary design of boreholes and water supply system.
The farm lies in close proximity to the junction between the Blisworth Clay and Blisworth Limestone Formations and the target water supply aquifers are the Blisworth and Estuarine Series limestones.
