25 WESSEX WATER SERVICES LIMITED
Introduction
Wessex Water supplies on average about 385 Ml/d of water to about 1.2 million consumers in most of the counties of Dorset and Somerset, and parts of Wiltshire and Hampshire and the former county of Avon. 20% of the Company’s water supplies come from surface water sources either as impoundments or lowland pumped storage reservoirs. 80% comes from groundwater sources, both boreholes and springs, mainly in the central and eastern regions of the supply area. The Company has 93 treatment works on 93 sites, and distributes water through 10,800 km of pipes and 325 service reservoirs to 103 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 152,149 determinations in 2000. Of these, 99.93% demonstrated compliance with the relevant PCV, but 105 showed a contravention to have occurred.
Coliforms were not detected at 86 (92%) of the Company's 93 water treatment works. At 323 (99%) of the Company's 325 service reservoirs, coliforms were absent from at least 95% of samples. Of the Company's 103 water supply zones in 2000, 102 (99%) 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 zone, breaches could result in enforcement action.
Microbiological quality of water leaving treatment works
The Company complied with the sampling frequencies required by regulation 17 all its treatment works in 2000.
Table 25.1 shows the Company's performance in 2000, with data for 1999 and 1998 for comparison. There has been a significant decrease since 1999 in the number of treatment works, and samples from treatment works, in which total and faecal coliforms were detected.
Contraventions of the microbiological quality standards at one works has resulted in the consideration of enforcement action, as shown in table 25.4. All other contraventions of the standards at works are considered trivial.
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 25.2 shows the Company's performance in 2000, with data for 1999 and 1998 for comparison. Differences the last three years in the number of service reservoirs, and samples from service reservoirs, in which coliforms were detected are not considered significant.
Contraventions of the microbiological quality standards at a service reservoir has resulted in the consideration of enforcement action, as shown in table 25.4. All other contraventions of the standards at service reservoirs are considered trivial.
Water quality in water supply zones
The Company complied with the required sampling frequencies for all parameters in all zones.
Table 25.3 shows the Company's performance in 2000, with data for 1999 and 1998 for comparison. There have been significant reductions over the last three years in the number of zones failing to comply with the standard for PAH. All other differences in zones are not considered significant.
Enforcement action is being considered in respect of a contravention of the standard, as shown in tables 25.3 and 25.4. All other contraventions of the standards in zones are considered trivial or are covered by undertakings.
Inspection
Follow-up of response to recommendations
Mr A Hallas, Inspector, followed up on the recommendations from the 1999 annual inspection. Mr Hallas concluded that:
the Company has made appropriate and positive response to the recommendations made in the 1999 report;
Audit trails of five samples
Mr R M Walls, Consultant, working under the direction of Mr W M Waite, Principal Inspector carried out audit trails on five samples chosen at random. Based on Mr Walls report Mr Waite concluded that:
The sampling is satisfactory in terms of frequency, but the sampler appears to have too much latitude to change the prescribed location. A number of infrequently required parameters were pre-scheduled in error and had to be descheduled at a later date. Analytical arrangements are generally satisfactory although there are some variations from Report 71. The analytical results have, with one exception, appeared on the Public Record in time.
Review of procedures for operation and maintenance of the distribution network
In December 2000, Consultants Binnie, Black and Veatch working under the direction of Mr W M Waite, Principal Inspector carried a follow up investigation of the recommendations made during the 1999 audit of the Review of Procedures for Operation and Maintenance of the Distribution Network. Based on their report Mr Waite concluded that:
It is recommended that to provide adequate responses to those responses to recommendations that are considered inadequate, the company extend its procedures to provide the following:
Guidance on flushing velocities that need to be achieved for mains of different diameters (Procedure for the Routine Operation of Valves - Recommendation R2.3 and Policy for the Pre-emptive Flushing of Mains and its Implementation - Recommendation R3.1).
Guidance on investigating what has caused the sediment disturbance that has resulted in discolouration (Procedure and Practice for Dealing with the Discolouration of Supplies - Recommendation R5.1).
Guidance and the sampling and analysis which should be carried out following a discolouration incident (Procedure and Practice for Dealing with the Discolouration of Supplies - Recommendation R5.2A).
A system for routinely monitoring the status (position) of valves and their site markers (System for Classifying, Recording, Marking and Monitoring Valve Status - Recommendation R8.3)
Inspection of distribution system improvement programme progress In September 2000, Consultants Parkman Ltd, represented by Mr P Spain, 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 Spain’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.
Audit of plumbosolvency treatment and control programmes of work
In November 2000, Consultants WS Atkins, represented by Mr M Kimber, 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 works to secure compliance with new lead standards. Based on Mr Kimber’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.
As a result of these inspections, nine recommendations were conveyed to the Company for formal response. The Company is taking action or has already taken action on a all of the recommendations.
Improvement programmes
No 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.
The ongoing distribution system improvement programmes due for completion in 2005, which have been implemented by the Company, have been progressing satisfactorily.
Relaxations
The Secretary of State had authorised relaxation of the PCV for colour, iron and manganese for properties with point of supply treatment, subject to review by 31 December 1999. As a result of the review initiated by the Inspectorate in November 1999 the relaxations were renewed for iron and manganese only, with revised values and subject to review by 25 December 2003.
Incidents
Four 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 drinking water quality demonstrably deteriorated.
In February 2000, an operational problem occurred at the booster chlorination station at Corfe Castle. This resulted in consumers in Swanage and parts of Purbeck receiving water with unacceptably high levels of residual chlorine over a period of several hours. In March there was a failure of the disinfection system at Batheaston water treatment work, but without a deterioration in water quality in the associated distribution system. In August low level bacteriological contamination was found at Churchingford service reservoir and in the associated distribution system. Also in August, discoloured water was supplied to consumers in the Sherford area of Taunton following planned work on part of the distribution system.
In each of the above incidents the problem was of short duration and the Company took all reasonable steps to protect consumers. The Company has also taken appropriate action on recommendations made by the Inspectorate.
No other events regarded as constituting incidents came to the attention of the Inspectorate in 2000.
Formal Caution
On 3 May 2000 the Company received a formal caution, which will remain on the files, having admitted an offence under Section 70 of the Water Industry Act 1991 for supplying water unfit for human consumption. This followed the investigation of an incident involving the supply of discoloured water to consumers in Market Lavington in August 1999.
Enforcement action
Table 25.4 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 25.1 Wessex WaterServices Limited
MICROBIOLOGICAL QUALITY OF WATER LEAVING TREATMENT WORKS2000 1999 1998 Number of water treatment works 93 96 101 Works with no sampling shortfall 93 96 101 COLIFORMS Total number of determinations 10,735 11,142 10,947 - number containing coliforms 8 19 19 - % containing coliforms <0.1 0.2 0.2 Treatment works with coliforms detected 7 15 17 - % of all works 8 16 17 FAECAL COLIFORMS Total number of determinations 10,743 11,164 10,947 - number containing faecal coliforms 2 9 5 - % containing faecal coliforms <0.1 0.1 <0.1 Treatment works with faecal coliforms detected 2 7 4 - % of all works 2 7 4
table 25.2 Wessex Water Services Limited
MICROBIOLOGICAL QUALITY OF WATER IN SERVICE RESERVOIRS2000 1999 1998 Number of service reservoirs 325 325 327 Service reservoirs with no sampling shortfall 325 325 327 COLIFORMS Total number of determinations 17,129 17,117 17,277 - number containing coliforms 25 33 22 - % containing coliforms 0.1 0.2 0.1 Service reservoirs with coliforms detected 19 27 18 Service reservoirs with coliforms detected in more than 5% of samples 2 0 2 - % of all service reservoirs <1 0 1 FAECAL COLIFORMS Total number of determinations 17,134 17,133 17,279 - number containing faecal coliforms 5 9 3 - % containing faecal coliforms <0.1 0.1 <0.1 Service reservoirs with faecal coliforms detected 5 9 3 - % of all service reservoirs 2 4 1
table 25.3 Wessex Water Services Limited
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 (103 in 2000)* Total Contravening PCV Non-compliant No. % CBU CBU E Number in: 2000 2000 1999 1998 Coliforms 4,689 21 0.4 0 0 0 0 0 0 Faecal coliforms 4,691 1 <0.1 0 0 0 0 2 4 Colour 1,579 0 0.0 0 0 0 0 0 0 Turbidity 4,679 1 <0.1 0 0 0 1 4 4 Odour 274 0 0.0 0 0 0 0 0 0 Taste 278 0 0.0 0 0 0 0 0 0 Hydrogen ion 4,664 0 0.0 0 0 0 0 1 0 Nitrate 4,356 2 <0.1 0 0 0 2 1 3 Nitrite 4,356 0 0.0 0 0 0 0 1 0 Aluminium 1.336 0 0.0 0 0 0 0 1 0 Iron 1,826 15 0.8 12 41 0 11 11 10 Manganese 2,195 4 0.2 0 0 1 3 2 0 Lead 788 0 0.0 0 0 0 0 2 5 PAH 651 19 2.9 18 49 0 12 30 30 Trihalomethanes 351 0 0.0 0 0 0 0 0 0 Total pesticides 694 0 0.0 0 0 0 0 0 0 Atrazine 472 0 0.0 0 0 0 0 1 0 Diuron 238 0 0.0 0 0 0 0 1 0 Simazine 472 0 0.0 0 0 0 0 1 0 Other pesticides 4,077 0 0 0 0 0 0 0 0 Benzo 3,4 Pyrene 647 2 0.3 0 0 0 0 0 0 All others 53,095 0 0.0 0 0 0 0 0 0 TOTAL 96,408 65 0.07 30 - - - - - *108 zones in 1999; 110 zones in 1998.
table 1.4 Wessex Water Services Limited
SUMMARY OF ENFORCEMENT ACTION CONSIDERED IN 2000Regulation reason for enforcement 3(7) Contravention of the coliform standard at one treatment works. 3(7) Contravention of the coliform standard at one service reservoir. 3(3)(c) Contravention of the standard for manganese in one zone.
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Published 11 July 2001
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