Summary of a brief given to Oxfordshire County Council in 1981 by the Central Electricity Generating Board, South West Region

The following is extracted from a document provided by the CEGB and which is paraphrased to avoid copyright breaches.

In 1981, the CEGB, proposed a series of measures to dispose of the material for the remainder of the life of Didcot Power Station because of the limited life of their existing tipping facilities at Sutton Courtenay for PFA.

This included:

1. Filling and restoration of gravel workings at Radley with ash transported by pipeline from Didcot.
2. Construction of a working stockpile of ash on land owned by the CEGB adjacent to the Power Station.
3. Payment of a contribution towards the cost of a new bridge over the London to Bristol Railway line to improve access to the Power Station for Ash Lorries.
4. Investigation of the potential for the establishment of an ash processing plant adjacent to the Power Station.

The planning application in 1981 covered points 1 and 2 and was submitted to the Vale of White Horse District Council.


INTRODUCTION

In this section of the brief the CEGB stated that the waste ash comprises 80% PFA and 20% FBA (Furnace Bottom Ash) The FBA is suitable for direct application for construction block making and in practice all of the material produced is sold for that purpose.

The original consent granted to the Power Station in 1964 by the then Minister of Power stated that PFA should not be disposed of by any other method except by a pipeline, unless agreement had been obtained from the County Council.

The County Council granted a relaxation of this stipulation to allow disposal of the material by road over private roads to the Sutton Courtenay site, which belonged to Amey Roadstone.

Because the gravel pits at Sutton Courtenay were also being used for the disposal of London’s rubbish, and were being filled faster than the gravel was being extracted, in February 1984 the CEGB agreed to cease depositing fuel ash at Sutton Courtenay with two years.

The embargo for transportation of PFA by road restricted the potential for commercial sale of the PFA. The CEGB felt that it was not economically viable to use the railway because of the double-handling required, and also that road transport would be required at its final destination, adding to the cost.

With the completion of improvements to the A34 in 1978, relaxation of the embargo was granted to allow 40 lorries a day, provided that access was made via the Milton Trading Estate. The permission to pass through this area was subject to termination at short notice and whilst the CEGB made substantial sales of PFA this restriction did not facilitate a long term marketing policy.

Oxfordshire County Council were planning construction of a new road from Milton Heights into Didcot from the A34, and was to be completed in 1983. The CEGB said that the construction of a new bridge over the railway line linking the Power Station with the new road would solve access problems and so restrictions on the number of vehicles leaving the Power Station would no longer be relevant. As part of the Planning Application in 1981 the CEGB agreed to make a contribution to Oxfordshire County Council towards the cost of the bridge.

FUTURE REQUIREMENTS OF THE CEGB

In 1981 the CEGB felt that Didcot Power Station would be generating until at least the year 2000. They had to find alternative methods of disposal of the PFA. They said that when the station was operating at full load, the annual output of ash was in the region of 500,000 tonnes per annum. They also said that as power stations get older the load factors reduce and the ash it would make would drop correspondingly.

The CEGB said that commercial ash sales were restricted by the level of road transport and relaxation of this control by provision of alternative access would allow a substantial increase in sales. They also said that there would be an opportunity to create an ash-processing plant on or adjacent to the Didcot Site, with the end product being able to transported by road.
 

ALTERNATIVE DISPOSAL METHODS/TRANSPORTATION

The CEGB felt in 1981 that even with optimum sales of PFA by road transport or to a processing plant, there would be some surplus requiring disposal and an alternative site to Sutton Courtenay must be found. They had considered large scale tipping of PFA above ground level between the Power Station and Sutton Courtenay and whilst this had been a practical possibility they felt the environmental considerations and the presence of unworked minerals caused it to be excluded as long as there was an economical reclamation possibility available.

The CEGB consulted with the County Planning Officer and four reclamation sites were identified with potential for future ash disposal. These were Dorchester, Shipton upon Cherwell, Stanton Harcourt and Radley. They considered all the options of how to get the PFA to these sites.

ROAD TRANSPORT was dismissed because the use of public roads for the disposal of fuel ash would not be accepted by the Highways Agency or the residents of villages close to the proposed sites.

RAIL TRANSPORT was dismissed because the CEGB had problems with scheduling of coal trains which had caused interference with rail services to and from Bristol. Further train movements would accentuate these difficulties. There was no rail link to Stanton Harcourt and Radley would not be suitable for a rail siding.

HYDRAULIC PIPELINE was chosen and the CEGB decided that the RADLEY site was most suitable because it is 8km from the Power Station and had a capacity of at least 8-9 years ash-fill at full production, EVEN WITH NO COMMERCIAL SALES. The pipeline would be straight and level and there was the River Thames adjacent to return ash pond water. The CEGB admitted that the capacity at Radley was insufficient by itself to accommodate the total PFA for the remainder of the life of the Power Station (2000) but would prove adequate in conjunction with commercial disposal proposals. They considered other sites at Dorchester, Shipton on Cherwell and Stanton Harcourt but dismissed these on grounds of cost and engineering difficulty.

The CEGB provided details of the pipeline which would be a single pipe approximately 17.5” (440mm) diameter. Above ground it would not have any external protection and it would go below ground with a minimum soil cover of 4ft (1.22m) being protected where it crossed under roads. Where the pipeline crossed the River it would be under the bed of the river.
METHOD OF OPERATION

The CEGB proposed to operate the pipeline for a maximum period of 12 hours per day discharging 30% PFA slurry at a rate of 236 litres per second. The proposed using a settling process which had previously been used at Cottam Power Station in Nottinghamshire, which discharged into the River Idle

The CEGB provided a drawing showing the levels of the ground and to protect the flood plain they had agreed with Thames Water to have a secondary wall between ponds not being filled and for flood water to enter and leave over weirs set at agreed levels. For the same reason, restored land levels had to be as near as possible that existed prior to the opening of the gravel pits.

The drawings submitted gave details of the positions of weirs and proposed and existing water levels. Another drawing shows the weirs, with two options to return water to the Thames. One involved the utilisation of an existing ditch – to be lined with concrete and the second to involve the installation of a buried pipe. Both options would discharge water into the river adjacent to the Rail Bridge.

The CEGB proposed that they would start the pipework in 1983 and commence engineering works at Radley in 1984.

The CEGB proposed to maintain a high level of site management and also proposed setting up a Liaison Committee with the CEGB and local residents.

RECLAMATION OF FILLED LAND AND LANDSCAPING
In 1981 the CEGB only prepared details for the land east of the Railway Line. They considered that this would be the first area to be reclaimed and it would be several years before the western land would come into use, as large areas were still unexcavated. The CEGB felt that whilst restoration of a similar type would be proposed the Planning Officer should be consulted closer to the period of working.

The CEGB concluded that there was insufficient topsoil available on the site to permit immediate agricultural restoration. Import of topsoil would be too expensive. Therefore they thought two types of surface reclamation would be suitable, part agriculture and part forestry. After a forest crop they considered the area could then be restored to agriculture if required.

The first lake they intended to fill was Lake B, They agreed to plant hedges to the north and north east sides of the lakes and early establishment of the bunds would allow consolidation planting of grass and sallow. During the process of filling Lakes B&C the areas of existing hedge between these lakes would be conserved and infilled to create a new permanent hedge line.

CENOSPHERES
The CEGB was aware that the lightness of these “floaters” would result in their escape in the wind. They concluded that if a depth of more than 1ft (300mm) formed then they would apply a suppressant of Curasol Polymer.

The CEGB felt that fencing would be dealt with as a “reserved matter” i.e. they did not need to apply for further planning permission to erect fences.

They stated that when the ash reached the water level of the lake and the surface became muddy, they would use a method called hydroseeding to spray 200ft (60M) from the edges of the lakes and if they could not reach the centre of the lake then they would construct sandy promontories on which to access the area. This was to prevent dust blowing off the ash into the environment.

TOPSOIL and AGRICULTURAL/FORESTRY Restoration.
The CEGB stated that once Lakes B&C had a grass cover and had dried out, and confirmed stable by soil engineers, they would cover them with a minimum of 10” of sandy overburden and 6” of topsoil. This topsoil would then be cultivated in early autumn or late spring with grazing type grass mixture, after checking the ground levels

The Forestry Land would have a blind of 50-85mm of sandy overburden, if there is sufficient quantity available. Manure would be available to each group of 10 tree sites for mixing with PFA. A back hoe would take out a pit a metre square for each tree. After settling, the mix of pfa, manure and fertilisers would be placed in to a depth of 330mm and firmed, and two year rooted stock of populous tacho tricha were to be planted in the pit backfilling with the prescribed mix to 50mm above ground level.

The CEGB concluded that after many years of filling and establishment of pasture and agricultural land, the last thing they would do would be to spread the original bunds, made to retain the ash during flood periods, restoring them to the original flood plain of 1981. The bund material would be spread over adjacent land and seeded with grass and wild flower seeds.

WORKING STOCKPILE


The CEGB said in 1981 they needed a working stockpile to meet demands for PFA and provide flexibility for marketing. Without the stockpile it would be necessary to install a second pipeline to Radley as a standby and without a stockpile the use of PFA as a construction material could not be maximised.

The CEGB showed a proposed Stockpile site, which would have a height of 25ft (8M) and would hold 500,000 tonnes of PFA. They intended to build a permanent V shaped bund to take a deposition of dampened ash by lorry.

The CEGB also stated that they were actively considering leasing land for the establishment of a PFA Processing Plant, next to the Power Station. This would be operated by a commercial company to provide suitable material for block making or aggregate for the construction industry. The finished products would leave this site via the new road bridge they were helping the Council to provide.

The CEGB had stockpiled PFA at other locations for marketing purposes, or in the case of DRAX Power Station in Yorkshire and ABERTHAW in South Wales for permanent restoration,

Finally the CEGB concludes that they had given careful consideration to all options available for future disposal of PFA. They believed the stockpile and possible processing factory would provide a solution for the remainder of the life of the Power Station.

The CEGB refer to something called “The Radley Water Park Scheme” and conclude that “As all of the excavations may be required for PFA, it is clearly incompatible with the Board’s long term proposals. However, where engineering and safety considerations permit, the Board will not object to limited use for water sport purposes until the tipping in the particular area commences”

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