[Report 1968] / School Medical Officer of Health, Dorset County Council.

  • Dorset (England). County Council.
Date:
1968
Catalogue details

Licence: Attribution 4.0 International (CC BY 4.0)

Credit: [Report 1968] / School Medical Officer of Health, Dorset County Council. Source: Wellcome Collection.

    60/84 (page 52)
    The pressure pipeline between Bridport and Beaminster was completed some months ago - as were the two main pumping stations - and to prevent continuation of the pollution which had occurred for many years in the River Brit, below Beaminster, the pressure pipeline will be brought into operation early in 1969. This is possible, by arrangement with the Bridport Corporation, who have agreed that sewage from Beaminster may be discharged, with that from Bridport itself, by means of the existing short sea outfall near East Beach, West Bay. This, for the time being, will aggravate the pollution of East Beach which occurs from time to time but when the new outfall is brought into use it is confidently expected that this will put an end to beach pollution problems in this part of Dorset. In last year's report, reference was made to the Suggested East Dorset Trunk Sewerage Scheme. This was devised by the County Public Health Engineer as a means of providing a long term solution to main drainage problems in parts of the county where the need was urgent, either because of new housing estates or because existing services were badly in need of re- placement or major overhaul. The scheme was designed to deal with a total population of 264,650 by the turn of the century and the estimated cost, in 1967 was £4,800,000. Mr. King's report on the scheme showed considerable savings both in capital costs and running costs com- pared with conventional schemes based on local sewage disposal works. However, although the County Treasurer agreed that in the long term there were likely to be considerable economic advantages, the burden imposed upon the ratepayers of Dorset in providing, as it were for posterity was, he felt, greater than they should be asked to bear and primarily for this reason, the scheme was put into abeyance. Nevertheless, the County Public Health Engineer felt convinced that trunk sewerage was the right long term solution to main drainage problems and it was agreed that he should prepare, in conjunction with Messrs. L.G. Mouchel and Partners, Consulting Engineers of Bath, a report on a modified scheme to serve South-East Dorset, involving, in substance, the laying of trunk sewers to serve the Wimborne area, the Wareham and Purbeck Rural District and eventually, the Borough of Wareham; the sewage would be taken out to sea by a submarine pipeline near Arish Mell. The actual discharge point could not be determined until detailed hydrographical surveys had been carried out but it was expected that the outfall would be at least one mile long. Mr. King completed his report in July and the amended scheme provided for a population of 225, 240 by the year 2001 at a total estimated cost of about £3, 000, 000. This allowed for a trunk sewer from Verwood to the outfall at Arish Mell, costing about £1, 824, 000, together with the necessary rising mains inter-connecting sewers, pumping stations and a 48 diameter submarine pipeline, one mile in length. This showed a capital saving compared with the altern- ative of providing conventional works to serve the same population (less that already served by existing sewage disposal works) of about £1,482, 425. As far as running costs were concerned, it was estimated that the saving would be nearly £100,000 per annum. The economic factors which would be involved in carrying out the suggested South East Dorset Trunk Sewerage Scheme were investigated, in detail by the County Treasurer. In his report, the County Treasurer pointed out that the same economic factors would apply to this revised scheme as to that prepared, in 1967, for the whole of East Dorset. He said that on the basis of the assumptions made by the County Public Health Engineer in his report, the annual saving from the trunk scheme might be of the order of £440, 000 in terms of cost in the year 2001. The break-even point would occur in about 1988 - several years earlier than in the case of the East Dorset Trunk Sewerage Scheme as a whole. The County Treasurer pointed out, however, that an economic advantage accruing over a period of eighteen to thirty years in the future had considerably less value than would have been the case if it accrued during the seventeen years immediately ahead. Accordingly, it was necessary to apply the discounted cash flow technique to ascertain the current value of both the aggregate excess cost and the