23 THAMES WATER UTILITIES LTD
Introduction
The Company supplies an average of 2,600 Ml/d to some 7.5 million people. The supply area includes London and a large proportion of central southern England. Approximately three quarters of the Company’s water supplies are derived from surface water sources, principally the Rivers Thames and Lee. The remainder is drawn from groundwater sources. Water from these sources is treated at 99 water treatment works. Treated water is distributed through 371 service reservoirs and over 31,500 km of mains. The supply area is divided into 236 water supply zones.
Overall water quality
At water treatment works and service reservoirs and in water supply zones, the Company carried out a total of 452,694 determinations in 2000. Of these, 99.89% demonstrated compliance with the relevant PCV, but 498 showed a contravention to have occurred.
Coliforms were not detected at 76 (77%) of the Company's 99 water treatment works. At 368 (99%) of the Company's 371 service reservoirs, coliforms were absent from at least 95% of samples. Of the Company's 236 water supply zones in 2000, 229 (97%) complied fully with the relevant water quality standards or had breaches of the standards which were either trivial or were fully covered by undertakings. In the other 7 (3%) of the zones, some breaches are regarded as unlikely to recur, but others could result in enforcement action.
Microbiological quality of water leaving treatment works
The Company complied with the sampling frequencies required by regulation 17 at all its treatment works in 2000.
Table 23.1 shows the Company's performance in 2000, with data for 1999 and 1998 for comparison. Differences over the last three years in the number of treatment works, and samples from treatment works in which coliforms were detected are not considered significant.
Contraventions of the microbiological quality standards at one works has resulted in the consideration of enforcement action, as shown in table 23.4. All other contraventions of the standards at works are considered trivial or unlikely to recur, or are covered by undertakings.
Microbiological quality of water in service reservoirs
The Company complied with the sampling frequencies required by regulation 18 at all of its service reservoirs in 2000.
Table 23.2 shows the Company's performance in 2000, with data for 1999 and 1998 for comparison. Differences over the last three years in the number of service reservoirs, and samples from service reservoirs, in which coliforms were detected are not considered significant.
All contraventions of the standards at service reservoirs are considered trivial or unlikely to recur because of remedial action undertaken by the Company, or are covered by undertakings.
Water quality in water supply zones
The Company complied with the required sampling frequencies for all parameters in all zones.
Table 23.3 shows the Company's performance in 2000, with data for 1999 and 1998 for comparison. Differences over the last three years are not considered significant.
Enforcement action is being considered in respect of some contraventions of standards, as shown in tables 23.3 and 23.4. All other contraventions of the standards in zones are considered trivial or unlikely to recur as a result of actions taken by the Company, or are covered by undertakings.
Inspection
Inspection of work being carried out on the distribution system In January 2000, Mr M Rouse, Chief Inspector, carried out an audit of work being carried out on the distribution system. Mr M Rouse concluded that the contractor working for and on behalf of Thames Water was meeting the requirements of Regulation 25 on epoxy lining.
Inspection of work being carried out on the distribution system In October 2000, Mrs Ceris Malhotra, Inspector, carried out an audit of work being carried out on the distribution system. Mrs C Malhotra concluded that:
that both excavations inspected were dry, clean and tidy;
the level of hygiene on-site was not satisfactory and the contractors working on behalf of Thames Water were not carrying out work in accordance with health and hygiene practices;
the condition of the van was poor, untidy and dirty;
there was no disinfectant on-site.
Audit trails of five samples
Mr R M Walls, Consultant, working under the supervision of Mr W M Waite, Principal Inspector, carried out an inspection of Thames Water Utilities Ltd in October 2000. Based on Mr Walls' Report Mr Waite concluded that:
the sampling and analytical arrangements are generally satisfactory;
the temperature of water in distribution is only recorded to the nearest whole degree, which is inadequate to meet the accuracy of ±0.5° in the Guidance Document; and
the analytical results have generally appeared on the Public Record in time.
Mr Walls found a contravention of regulation 21(2)(d)(iii) in respect of one parameter. However, remedial action was taken speedily and so enforcement action was not necessary.
Audit of plumbosolvency treatment and control programmes of work
In November 2000, Consultants WS Atkins, represented by Mr S Ntifo, working under the direction of Mr P Halton, Inspector, carried out an audit of the Company as part of the Inspectorate’s work in agreeing with water companies’ their programmes of work to secure compliance with new lead standards. Based on Mr Ntifo’s report, Mr Halton concluded that:
the Company’s process of sites/scheme selection for plumbosolvency treatment and/or optimisation measures is sound;
the integrity of the data submitted to the Inspectorate and used for assessing plumbosolvency was confirmed;
the schemes audited are justified on water quality reasons; and
the Company’s proposed steps to be taken and the proposed completion dates are generally sound.
Follow-up of response to recommendations
Dr K J White Inspector, carried out an inspection, by correspondence, of Thames Water Utilities Ltd in December 2000. Dr White concluded that:
the Company made a positive response to the recommendation made in the early 2000 inspection report.
Review of procedures for the operation and maintenance of the distribution system Mr P Scott, Consultant of Binnie, Black and Veatch, working under the direction of Mr W M Waite, Principal Inspector, carried out an inspection of Thames Water Utilities in December 2000. Based on Mr Scott's report Mr Waite concluded that:
the Company has made substantial responses to most of the recommendations made in the previous audit of water company procedures for operation and maintenance of distribution systems but there are still areas where the company responses are considered to be inadequate.
Inspection of distribution system improvement programme progress
In August 2000, Consultants Parkman Ltd, represented by Mr G Carlisle, working under the direction of Mr P Halton, Inspector, carried out an audit of the Company’s progress with the mains renovation set out in the distribution Undertaking submitted by the Company. Based on Mr Carlisle’s report, Mr Halton concluded that:
the objectives of the undertaking remained valid;
the steps to be taken were defined with adequate precision;
a practicable timetable had been set; and
the Company was likely to meet the target renovation length by the date for completion of the work.
As a result of these inspections, 13 recommendations were conveyed to the Company for formal response. No suggestions were made. The Company is taking action or has already taken action on these recommendations.
Improvement programmes
Ten undertakings in respect of improvement programmes accepted by the Secretary of State from the Company were due for full completion or the completion of major steps during 2000 and all of these were completed on schedule.
The ongoing distribution system improvement programmes due for completion in 2002, which have been implemented by the Company, have been progressing satisfactorily.
Incidents
Seven of the events notified during 2000 by the Company to the Secretary of State under the terms of the Water Undertakers (Information) Direction 1998 were regarded by the Inspectorate as constituting incidents in which either drinking water quality demonstrably deteriorated.
Four incidents have been assessed. Two of these incidents involved the supply of discoloured water affecting consumers in Merton, in August and Kidlington, in September. A further incident involved a failure of the disinfection system at Dorney water treatment works in May. The remaining incident involved wholesomeness concerns following low level bacteriological failures in the water leaving Noke Service Reservoir in September. The Company took all reasonable steps to protect consumers during each of the above incidents and has taken action to prevent similar incidents occurring in the future.
Three incidents, all involving the supply of discoloured water, together with two from 1999 and one from 1998 remain under consideration.
No other events regarded as constituting incidents came to the attention of the Inspectorate in 2000.
Enforcement action
Table 23.4 summarises enforcement action under consideration for the Company as a result of the Inspectorate's work in, or pertaining to, the calendar year 2000.
table 23.1 Thames Water Utilities Ltd
MICROBIOLOGICAL QUALITY OF WATER LEAVING TREATMENT WORKS2000 1999 1998 Number of water treatment works 99 104 96 Works with no sampling shortfall 99 104 96 COLIFORMS Total number of determinations 18,816 19,520 18,778 - number containing coliforms 32 39 48 - % containing coliforms 0.2 0.2 0.3 Treatment works with coliforms detected 23 28 31 - % of all works 24 27 32 FAECAL COLIFORMS Total number of determinations 18,816 19,520 18,778 - number containing faecal coliforms 1 5 4 - % containing faecal coliforms <0.1 <0.1 <0.1 Treatment works with faecal coliforms detected 1 5 4 - % of all works 1 5 4
table 23.2
MICROBIOLOGICAL QUALITY OF WATER IN SERVICE RESERVOIRS2000 1999 1998 Number of service reservoirs 371 381 372 Service reservoirs with no sampling shortfall 371 381 372 COLIFORMS Total number of determinations 18,730 19,236 18,901 - number containing coliforms 57 75 80 - % containing coliforms 0.3 0.4 0.4 Service reservoirs with coliforms detected 50 56 63 Service reservoirs with coliforms detected in more than 5% of samples 3 7 3 - % of all service reservoirs 0.8 2 1 FAECAL COLIFORMS Total number of determinations 18,730 19,236 18,901 - number containing faecal coliforms 3 2 2 - % containing faecal coliforms <0.1 <0.1 <0.1 Service reservoirs with faecal coliforms detected 3 2 2 - % of all service reservoirs 1 1 1
table 23.3
WATER QUALITY IN SUPPLY ZONESColumns 'CBU' show, for determinations, contraventions covered by undertakings and, for zones, the total number of zones covered by undertakings in 2000. Column 'E' shows the number of zones for which new enforcement action is under consideration as a result of contraventions of the PCV in 2000. Please refer to the Introduction to Part 2 for more detailed explanation of this table. PARAMETER DETERMINATIONS in 2000 ZONES (236 in 2000)* Total Contravening PCV Non-compliant No. % CBU CBU E Number in: 2000 2000 1999 1998 Coliforms 19,714 259 1.3 17 6 1 4 3 5 Faecal coliforms 19,714 10 0.1 0 0 0 9 10 13 Colour 2,500 0 0.0 0 0 0 0 0 0 Turbidity 2,537 1 <0.1 0 23 0 1 1 0 Odour 1,354 1 <0.1 0 0 0 1 3 2 Taste 1,321 0 0.0 0 0 0 0 3 1 Hydrogen ion 3,782 0 0.0 0 0 0 0 0 0 Nitrate 2,575 4 0.2 0 2 1 2 2 1 Nitrite 6,135 86 1.4 0 0 0 40 55 64 Aluminium 2,504 1 <0.1 0 8 0 1 0 0 Iron 2,756 7 0.3 7 69 0 6 7 11 Manganese 2,513 0 0.0 0 5 0 0 1 0 Lead 1,267 5 0.4 0 0 0 4 3 3 PAH 1,232 28 2.3 21 51 0 15 18 16 Trihalomethanes 979 0 0.0 0 0 0 0 0 0 Total pesticides 13,862 0 0.0 0 2 0 0 0 0 Atrazine 13,891 0 0.0 0 2 0 0 10 4 MCPA 7,602 0 0.0 0 2 0 0 0 2 Other pesticides 222,615 0 0.0 0 2 0 0 0 0 Benzo-3.4-pyrene 1,240 2 0.2 0 29 0 1 0 0 Mercury 243 0 0.0 0 0 0 0 0 2 Nickel 254 0 0.0 0 0 0 0 1 0 Potassium 243 0 0 0 0 0 0 0 1 Sodium 236 0 0.0 0 0 0 0 0 1 Surfactant 255 0 0.0 0 0 0 0 1 0 Zinc 1,267 1 0.1 0 0 0 1 0 0 All others 45,011 0 0.0 0 0 0 0 0 0 TOTAL 377,602 405 0.1 - - - - - *236 zones in 1999; 233 zones in 1998.
table 23.4 Thames Water Utilities Ltd
SUMMARY OF ENFORCEMENT ACTION CONSIDERED IN 2000Regulation reason for enforcement 3(3)(c) Contravention of the total coliform standard in one zone. 3(3)(c) Contravention of the nitrate standard in one zone. 3(7) Contravention of the total coliform standard at one treatment works
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PPublished 11 July 2001
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