History of Rutland Water.
This article was first published in the club magazine, The Big Puddle. It describes the building of Rutland Water and the engineering that surrounded the project.
If you are interested in learning more, the Rutland History & Record Society has an excellent publication ‘The Heritage of Rutland Water’. The entire book is available online, chapter by chapter, here: The Heritage of Rutland Water
Of interest to all Rutland anglers, here is another instalment on the history of this great lake. Planning and Constructing the Reservoir – Robert Ovens and Sheila Sleath. This chapter is primarily based, with full permission, on the personal recollections of John Winder, and The Empingham Reservoir Project (Rutland Water) by A J H Winder MA FICE (formerly Chief Resident Engineer, Empingham Reservoir Project), R G Cole FICE (formerly Project Manager, Empingham Reservoir Project), and G E Bowyer BSc FICE (Director of Operations, Anglian Water) which was presented to the Institution of Civil Engineers on 14th May 1985 and published in the Proceedings of the Institution of Civil Engineers, Volume 78, April 1985.
The project to build Rutland Water was originally known as the ‘Empingham Reservoir Project’, or more correctly, the ‘Empingham Pumped Storage Project’. It was completed in 1976, being one of the largest water supply schemes undertaken in the United Kingdom, and certainly the largest civil engineering project in Rutland. It involved the construction of an earth fill dam to form an impounding and pumped storage reservoir with a capacity of 124 million cubic metres in the valley of
the River Gwash.
The reservoir is filled partly by impounding water from the Gwash, but mainly by pumping water from the much larger Welland and Nene. The pumped supply system to the reservoir required river intakes, pumping stations, 14km of tunnelling in Upper Lias clay, and large-diameter pipe lines. More pipelines were laid to connect the reservoir to a new water treatment works at Wing, and one major and two minor roads were constructed to replace those lost to the flood. Finally, a great deal of trouble was taken over the landscaping in order to make the reservoir worthy of its setting and suitable for a range of water based and other outdoor leisure activities.
Large reservoir schemes have a reputation for long gestation periods before their final commissioning, and Empingham was no exception. After completion of the Pitsford Reservoir Scheme in Northamptonshire in 1956, Leonard Brown, then Engineer to the Mid-Northamptonshire Water Board (MNWB), and Thomas Hawksley, a consultant civil engineer, started searching for a suitable site for the next major water development that, in their opinion, would undoubtedly be needed in the area. The need arose from a steady increase in demand for water in the East Midlands in the 1960s, accelerated by the expected requirements of the five planned expansion areas of Corby, Daventry, Northampton, Peterborough and Wellingborough.
Leonard Brown set out the criteria for the new reservoir site: ‘The valley must have a suitable shape, so that the reservoir will hold plenty of water, the ground must be strong enough to bear the weight of the dam, and the dam of course mustn’t leak so the geology must be right. There must be plenty of local material from which to build the dam, there must be a river reasonably near so that a large quantity of water can be obtained to fill the reservoir, and lastly of course the site must be sufficiently near the centres of population where the water is wanted, so that the pumping costs are not too high.
By 1967 the Gwash valley upstream of Empingham and the nearby Chater valley to the south-west of Manton had been selected as the most suitable sites for storage reservoirs to provide for the predicted demand, estimated at that time to exceed the capacity of available resources by over 300 million lites per day in the year 2001 (see Chapter 14 – Rutland Waters).
Preliminary geological investigations proved that both the Empingham and Manton sites were suitable for dam construction, and in 1968 a decision was made to proceed with promotion of the reservoir scheme. The original proposal was to promote both reservoirs, but it was eventually decided to proceed only with the Empingham Reservoir, in the knowledge that Manton Reservoir could be developed in the future, as a second stage, if required. The Welland and Nene River Authoritv (WNRA) took the lead in the ioint promotion of the scheme with the Mid Northamptonshire Water Board.
During the construction of the reservoir they were replaced by the Anglian Water Authority, which came into existence as a result of the 1973 Water Act. In 1983 this Authority was renamed Anglian Water.
Despite a concerted campaign by local groups, including Rutland County Council, the National Farmers Union, the Country Landowners Association, the Council for the Preservation of Rural England and Oakham Rural District Council, the Welland and Nene (Empingham Reservoir) and Mid-Northamptonshire Water Board Bill received Parliamentary approval in May 1970.
The Empingham Pumped Storage Project
An overall plan of the reservoir. Note that a new fishing lodge and restaurant has been built at Normanton since this plan was prepared. The original fishing lodge at Whitwell is now a café.
Responsibility for the design and construction of the reservoir was divided between the Welland and Nene River Authority and the Mid- Northamptonshire Water Board, the joint promoters of the scheme, and T & C Hawksley, the appointed consulting engineers. The organization of all aspects of the project was under the control of the Empingham Project Committee appointed by the River Authority.
This committee was closely involved with the progress of the work and was charged with taking quick and positive decisions. Liaison between all the organizations and contractors involved was provided by regular meetings attended by all parties. Such close cooperation was essential to ensure that the overall project programme was maintained and that technical matters were not overlooked or duplicated.
Because of uncertainties regarding the precise geology of the area near the dam and along the line of the supply aqueduct, final designs could not be completed until after construction had commenced. The successful design was to rely heavily on test results and other data from boreholes and a trial embankment which were to be completed in the first year of the project. Monthly design and construction meetings chaired by John Winder, Chief Resident Engineer, and attended by his team, design staff, and geotechnical and soils consultants, reviewed instrumentation and test results, decided upon further investigation work, and made design decisions and modifications. Any construction instructions or implications resulting from the meetings were conveyed to the contractors within 24 hours.
John (A J H) Winder – Chief Resident Engineer for Rutland Water
John Winder spent the first five years of his life in Poona, India, where his father was an Army Medical Officer. Returning to the UK (United Kingdom) in 1927, his family lived at Folkestone, Kent, until his father was posted abroad again in 1932. He then attended boarding schools and from 1935 he was at Shrewsbury. On leaving, he enlisted in the Royal Signals and spent some time on a short course at Oxford on electronics and mathematics. Little did he know it at the time, but a contact made on this course was to have an important effect on the direction of his future career.
After passing out at Catterick, North Yorkshire, in 1941, he joined the Royal Signals and was appointed Signals Officer to 90th (City of London) Field Regiment Royal Artillery. The Regiment was sent in turn to India, Northern Iraq, Palestine and Egypt, where he was transferred to the ‘Desert Rats’ (the 50th Northumberland Division). He also took part in the invasion of Sicily before returning to the UK in January 1944. On Monday 5th June 1944, John was crossing the English Channel on a landing craft, his destination being Sword Beach where he was about to take part in the D Day landings.
By the end of hostilities the Royal Signals were very busy restoring communications in Germany. This important work meant that he was unlikely to get early release from the army. However, he managed to obtain 48 hours leave, and made his way to Oxford University where he visited A H Smith, Warden of New College, whom he knew from his course there in 1940. On his return to Germany, he received a telegram from the War Office giving him immediate release from the Army and instructing him to report to New College at the beginning of October.
In 1949, at the age of 28, he graduated with an honour’s degree in Engineering Science, but opportunities for young engineers in the UK were very few at that time, and salaries were low. So, he looked abroad and early in 1949 he joined the Colonial Engineering Service as a junior engineer in Northern Rhodesia, now Zambia. Here he worked on water supply schemes, roads and bridges before resigning and returning to the UK in 1954. John now joined consulting engineers Binnie, Deacon and Gourley in London who specialised in water supplies and dams.
Until 1957 he served as a Senior Assistant Resident Engineer on the Tai Lam Chung Water Supply Scheme in Hong Kong, building a large concrete dam and three smaller earth dams. Following his return to London, he married Cherry Lewis in May 1959, and later that month, he left for Nigeria to supervise water supply projects as a relief engineer. In 1960, he again returned to London and his next project was Diddington Dam, now known as Grafham Water (Cambridgeshire), where he was Chief Resident Engineer, living with his family in the village of Brampton, near Huntingdon, a few miles away from the project.
His next move was to Herbert Lapworth and Partners in Westminster who wanted him as their resident engineer for the construction of Scammonden Dam, high in the Pennines, near Huddersfield, West Yorkshire. Again, he and his family moved to be near the job, this time to an old vicarage in a remote Yorkshire valley. The project involved working closely with the County Council, who were building the M62 motorway, Britain’s first mountain highway, which was to cross the valley on the crest of the dam. It was to be one of the highest dams in the UK, and was constructed using rock fill removed from the bottom of the valley. The M62 and reservoir were formallv opened by the Queen on 14th October 1971, by which time John had moved to a new project in Rutland.
In December 1969 he was interviewed by T & C Hawksley (later Watson Hawksley), a small but much respected firm of consulting engineers. He was appointed as Chief Resident Engineer, to be in charge of the construction of a large earth dam and water supply scheme at Empingham – the future Rutland Water.
On 13th October 1970 he started his new job, living at a hotel in Oakham, by which time there was already a great deal of activity on the site. Again, wishing to have his family with him, they moved to ‘Stone House’ in Wing in 1970. John says, referring to Rutland Water and Graham Water, I am proud to have played a part in both these projects. His last day at Empingham was 31st January 1975, but he returned for a ceremony at the outlet shaft on 6th February 1975 for the closing of the scour (outlet) valve and the start of impounding water in the reservoir. For him ‘… it was a moment to remember . . . something important had just taken place, after years of effort by hundreds of people’.
One special aspect of the project that he was pleased to be involved with was the saving of Normanton Church. ‘This was due to be demolished, but several local people wanted it to be preserved and I was one of them, and undertook to look into how it might be saved. We formed the Normanton Tower Trust, to put proposals before the Water Authority which firmly maintained that it must be demolished, and there was no money available to preserve it. ‘We considered excavation all round it, and jacking it up, and moving it bodily, foundations and all, to a higher level. I contacted a firm which specialised in moving historic or important buildings, and they submitted outline plans for how it could be done, and a price for doing it – but the cost was way beyond what might be available.
I looked into other alternatives, and realised that it would be very much cheaper to fill round the church with compacted earth to a level higher than the top water level of the reservoir, fill up the crypt and lower levels of the church interior with stone and compacted gravel, put in a false floor at a higher level, and new sills for the windows at a level well above the water level. The cost of doing all this at contract rate prices was reasonable and I discussed it in detail with the Contractor’s Agent, who was looking for a site to dump soil from excavations being carried out from other nearby works, and a low price was quoted.
The cost of demolishing the church was also, of course, saved and the client eventually agreed with our new plan.’ The Normanton Tower Trust raised the money to cover the cost of saving the church building which has become a prominent landmark on the shores of Rutland Water.
After Rutland Water, John was offered a partnership with Watson Hawksley at their new offices in High Wycombe, and continued to work on water supply and reservoir projects.
On 30th April 1985, he retired, but continued working as an Inspecting Engineer under the Reservoir Act for a few more vears.
John Winder at the scour valve closing ceremony on 6th February 1975 to mark the start of impounding water in the reservoir (Brian and Elizabeth Nicholls)
Boreholes were drilled to prove the sequence of strata shown on Geological Survey maps and to provide more localised detail.
The most significant geological components are the Upper Lias clay and the Marlstone Rock Bed. The Marlstone Rock Bed is a confined aquifer 22m below the valley floor in the vicinity of the dam, and extends under the whole of the reservoir area. It is covered by Upper Lias clay which gradally reduces in thickness along the twin Gwash valleys until the Marlstone eventually outcrops at the head of the reservoir
The Marlstone Rock Bed also underlies the route of the tunnels. A ‘valley bulge’, which runs approximately along the line of the wash, results in considerable localised disturbance to the strata above the Marlstone Rock Bed. This was to result in some serious problems for the dam builders. The layer of Upper Lias clay was to provide most of the material for building the earth embankment which was to form the dam and also offered a fairly easy excavation route for the supply aqueduct tunnels.
Above: The geological section at the dam site, looking upstream. The layer of Upper Lias clay was to provide most of the material for building the earth embankment which was to form the dam and also offered a fairly easy excavation route for the supply aqueduct tunnels. The Marlstone Rock Bed is too deep to be affected by the valley bulge at this point, but the Upper Lias Clay is severely disturbed (after the Institution of Civil Engineers).
The Work Begins
A very rapid start on the construction was necessary because there was a predicted shortfall in water supply by 1976. Consequently, detailed site investigations and site clearance started in June 1970, only a month after Parliamentary approval, and the first major contract, for the River Gwash diversion tunnels, was let in December 1970.
By far the greatest task in the site clearance programme was the removal of trees, hedges, shrubs and fences. This started in the dam area near Empingham, and continued along what was to become the south arm of the reservoir. It included the complete removal of Mow Mires Spinney, Cocked Hat Spinney, Brake Spinney and Snowdrop Spinney, and the partial removal of Hambleton Wood, Gibbet Gorse and Half Moon Spinney.
Much of this had been completed by mid-1973. Within the next twelve months much of Armley Wood and Barnsdale Wood in the future north arm of the reservoir had been removed, as well as part of Burley Wood for the A606 Barnsdale Hill diversion.
Another aspect of site clearance was the demolition of all the dwellings and farm buildings in Nether Hambleton, eight dwellings and numerous farm buildings in Middle Hambleton which were below the high water level, two dwellings at the foot of Barnsdale Hill, and Mow Mires farmhouse in Normanton Park. Some of the demolition rubble was used to create the Nature Reserve lagoons at the western end of the reservoir.
In order to start work in the bottom of the valleys it was first necessary to divert the River Gwash round the dam construction site. For this purpose a tunnel, which would later become a part of the permanent works, was driven from near the upstream toe of the embankment into the hillside on the south side of the valley at the reservoir outlet shaft location. A second tunnel was then driven back from the outlet shaft to the river near the downstream toe.
The work was carried out by Edmund Nuttall Ltd before work on the main embankment had started. It also allowed removal of the surface material down to the Upper Lias clay on the embankment site immediately at the start of the main contract.
Shafts & Tunnels
The outlet shaft, which is 10.7m internal diameter, was sunk first, followed by the two tunnel by drives, all three being lined with concrete segments. The upstream and downstream tunnels are 3.7m and 4.4m internal diameter respectively. The upstream tunnel was lined with concrete infill panels and sprayed with an epoxy paint to provide protection against anaerobic water lying for long periods in this section of the tunnel.
The downstream tunnel, which was completed later under the main contract, is divided by a platform. In the top half, a 1.2m diameter steel pipe delivers the raw reservoir water to the outlet pumping station from where it is pumped to the water treatment works at Wing, or to Colsterworth, Lincolnshire.
The remaining space is used as an access walkway, for power and control cables, and for other services. The bottom half of the tunnel carries the overflow from the reservoir and also any additional water necessary to maintain the minimum downstream flow of the River Gwash, known as the regulation water. It also carries water discharged through the scour pipe. The scour valve can be opened to let water out of the Reservoir very quickly. For example, it can be used in an emergency if the dam is damaged or if it is necessary to lower the water level for any reason.
The scour valve is also opened to flush sediment out of the reservoir when too much has collected behind the dam. The fast flowing water carries the sediment through the scour and downstream.
Excavating the reservoir outlet shaft. It is 10.7m in diameter and over 30m deep (Brian & Elizabeth Nicholls Photography)
At the tunnel exit, there is a stilling basin and tailbay which incorporates a weir for measuring the river regulation water and the overflow water. Water is also discharged here from the Marlstone relief wells. A new river channel has also been constructed downstream from the tailbay to Church Bridge, Empingham, where the total water released is measured.
Lowering the tunnelling machine into the outlet shaft (Brian and Elizabeth Nicholls Photography)
Empingham Dam, an earthfill embankment 37m high, 1,200m long, and 810m wide at its foundation level, is an important component of the Empingham Reservoir Project. The main geological features of the valley were established before Parliamentary approval by a prelimnary site investigation.
The Upper Lias clay was the controlling geological factor and it was known that the valley sides were extensively disturbed. It was also expected that the Upper Lias clay in the valley floor would be affected by valley bulging. The strength of the clay foundation was known to be inadequate to support the weight of an embankment of the specified height. This was the controlling factor in its design and resulted in a wide cross-section with extensive slopes.
Building the dam, must be excavated from inside the reservoir area. The Upper Lias clay would therefore be used to build the embankment. At 37m high it would be one of the highest ever built of clay on a clay foundation.
If the Manton Reservoir project had gone ahead, the earth embankment there would have been 43m high, and this was considered to be the absolute maximum for this type of dam. It would also have to have been wider at the top to accommodate the 37m necessary for the A6003 which crosses the Chater Vallev at this point, resulting in a very high volume of clay being required.
A feasibility study for the Empingham Dam indicated that, even with long slopes, sand drains would be required to ensure the stability of the clay foundation. The sand drains would collect water forced out of the pores of the clay by the weight of the dam above and drain via the drainage blankets within the dam structure.
Before the dam could be designed in detail a site investigation was necessary to gain a detailed understanding of the geology. This had to be completed within the twelve months before the set date for the start of the construction. It was carried out by Soil Mechanics Ltd between August and December 1970 and included drilling boreholes to investigate the structure and properties of the clay foundation beneath the sites of the dam and borrow pits, as well as consolidation and bearing tests.
Core samples were initially tested off site, but a well-equipped site laboratory, commissioned during this period, allowed very quick analysis of samples. While the site investigation was taking place, the availability of suitable materials for drainage, filters and riprap was investigated. Riprap is rock used on the dam face to reduce erosion by dissipating wave energy. An understanding of the geology of the valley developed progressively during the investigation. The Institute of Geological Sciences carried out a fossil study of the core samples in order to establish a zoning system within the clay. This enabled the identification of the different types of clay required for the embankment.
It was established at an early stage that, although the valley bulge penetrated 20m below the valley floor, the Marlstone Rock Bed at the dam site was not affected. This was an important discovery as, in this area, it is a confined aquifer containing water under pressure. If a rupture was ex-
posed it would behave as an artesian well and flood the area very quickly. In order to reduce this pressure it was necessary to install relief wells on the downstream side of the dam to control the uplift pressure.
The test results enabled the design of the dam to progress, although considerable uncertainty remained concerning the strength of the foundation clay and the behaviour of the embankment fill material under heavy loading. The solution was to build a trial embankment, but the tight programme meant that this could not be done until after the construction start date. The aim at this stage was, therefore, to progress the design sufficiently to enable tenders to go out for the selection of a main contractor for the construction of the dam and ancillary works.
To enable tenders to be made on a reasonably firm basis, it was decided that the contract should include provisional elements to cater for the uncertainties, with dates by which final decisions must be made. These elements were: the extent of the slopes, the number of drainage layers within the dam, and the spacing of the sand drains. Tenders were invited in May 1971 and Gleeson Civil Engineering Ltd was appointed as the main contractor on 14th September 1971.
A major feature of the contract was the construction of the large trial embankment within the upstream slope and this was to be retained as part of the final embankment. By using steep slopes, a shear stress in excess of that imposed by the final embankment could be imposed on the
foundation clay. The trial was to be carried out during the first year of construction, and the slope design was to be fixed four months after its completion.
The trial embankment was built near the south side of the valley floor to avoid the main valley bulge. A trench was excavated into the valley side to ensure that it had a constant height over alength of about 70m, and calculations proved that the stress imposed on the foundation clay would be well in excess of that imposed by the final embankment.
Three failures of temporary steep clay embankments in the borrow pits occurred while the trial embankment was under construction.
Data from these failures reduced the need to take the trial bank to failure, and construction ceased when the mean height was 21m. The dynamic performance of the bank and underlying strata was then observed for the next four months.
After excavation of the soft alluvium in the valley floor down to the Upper Lias clay, the material being taken to spoil heaps or used to make up the lower part of the slopes, the dam site was ready for the installation of sand drains. It is interesting to note here that the engineers were able to map in detail some of the shear surfaces apparent on the face of the newly exposed Upper Lias Clay. Peter Horswill, the site geologist, realised that this had occurred at the end of the last Ice Age, some 100,000 years ago, due to the bottom of the valley bulging upwards as a result of the immense pressure from the weight of the thick ice on the shoulders of the valley.
The sand drains were installed by Soil Mechanics Ltd who commenced work in January 1972. They drilled 10,873 600mm diameter drains to a maximum depth of 18m, using crane mounted augers, within the six-month contract period, a rate of approximately 60 sand drains per day. The drains were filled with sand and the area was flooded between clay bunds or saturated by spray irrigation to ensure consolidation. The drains were made up with additional sand before embankment fill placing started.
The final design for the dam was decided early in 1973. It incorporated extra information obtained from the trial embankment and borrow pit slips, and the observations of sand drain performance. The slopes needed were found to be smaller than those predicted by the initial design assumptions.
More importantly, construction could be completed with much less uncertainty. Material for the main embankment (dam) was placed using 12 Terex TS24 16 cubic mete twin-engined motor scrapers, ideal for the terrain and short haul distances between the borrow pits and the embankment site.
Installing sand drains in the foundation of the dam (Brian & Elizabeth Nicholls Photography)
Bulldozers were used as pushers for the motor scrapers when collecting clay in the borrow pits. Cut-off trenches, to prevent water leakage round the ends of the embankment, were excavated into the valley sides until the top of the Upper Lias clay was 1.7m above the reservoir top water level. These were then filled with clay to 2.2m above this level. Above this, the excavated surface material was replaced.
Natural gravels from pits in the Fens were used as filters and drainage materials within the embankment, and because of sporadic high demand these were stockpiled on site. The Upper Lias clay used for the embankment construction was extracted from borrow pits located below top water level upstream of the dam. They were excavated to full depth in sections, surface material being placed in worked-out areas.
The drainage of the underlying Marlstone Rock Bed (see later) allowed the borrow pits to be deepened without risk of uplift through artesian pressure. However, a section brought upwards by valley bulging was unexpectedly exposed in the south borrow pit. It was subsequently blanketed with clay to prevent leakage from the reservoir.