6 DEE VALLEY WATER PLC
Introduction
Dee Valley Water plc supplies on average about 73 Ml/d to about 257,100 consumers in Chester, Wrexham, Llangollen and surrounding areas of Denbighshire and Flintshire. About 80% of the Company’s water supplies come from the River Dee; 16% from upland surface water impoundments. The remainder comes from boreholes (2%) and a spring source (2%). Water is treated at eight treatment works and is distributed through 31 service reservoirs and 1,953 km of mains. The supply area is divided into 18 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 12,828 determinations in 2000. Of these, 99.90% demonstrated compliance with the relevant PCV, but 13 showed a contravention to have occurred.
Coliforms were not detected at seven (87.5%) of the Company's eight water treatment works. At 29 (93.5%) of the Company's 31 service reservoirs, coliforms were absent from at least 95% of samples. Of the Company's 18 water supply zones in 2000, all (100%) complied fully with the relevant water quality standards or had breaches of the standards which were either trivial or were fully covered by undertakings.
Microbiological quality of water leaving treatment works
The Company complied with the sampling frequencies required by regulation 17 at all of its eight treatment works in 2000. Shortfall at the other treatment works is regarded as trivial.
Table 6.1 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 or faecal coliforms were detected are not considered significant.
All contraventions of the standards at works are considered trivial or unlikely to recur.
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 6.2 shows the Company's performance in 2000, with data for 1999 and 1998 for comparison. Differences in the last three years in the number of service reservoirs, and samples from service reservoirs, in which coliforms or faecal coliforms were detected are not considered significant.
Contraventions of the microbiological quality standards at two service reservoirs are considered trivial or unlikely to recur.
Water quality in water supply zones
The Company complied with the required sampling frequencies for all parameters.
Table 6.3 shows the Company's performance in 2000, with data for 1999 and 1998 for comparison. Differences over the last three are not considered statistically significant.
All contraventions of the standards in zones are considered trivial or are covered by undertakings.
Inspection
Investigation of computer systems and associated data management for drinking water quality information appearing on the Public Record
Part of the 2000 inspection of Dee Valley Water plc was carried out by Messrs Chapman and Milsom of DERA; consultants working under the supervision of Mr W M Waite, Principal Inspector. Based on the DERA report Mr Waite concluded that:
The systems examined appear to provide appropriate support to the business.
While there are significant security concerns, these mainly relate to one specific PC.
Some computer hardware is inappropriately located.
Some parts of the LIMS software are fundamentally insecure and require attention.
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 and analytical arrangements are generally satisfactory, although fuller records should be kept of sample storage and system suitability by the subcontracted laboratory. The analytical results have appeared on the Public Record in time.
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 Kimbers’ 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.
Review of procedures for operation and maintenance of the distribution network
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 assessing discolouration risk from increased velocities and areas affected by the operation (Procedure for the Routine Operation of Valves – Recommendation R2.1)
Guidance on flushing velocities that need to be achieved for mains of different diameters and general guidance on valve operation speeds to reduce the risk of discolouration (Procedure for the Routine Operation of Valves – Recommendation R2.3)
Guidance on sampling requirements following a discolouration incident (Procedure and Practice for Dealing with Discolouration of Supplies – Recommendation R5.2)
Guidance on network model application with respect to assessing discolouration risk from increased velocities, flushing velocities to be achieved for mains of different diameters and general guidance on valve operation speeds. (The Use of Computer modelling and other techniques to assess potential discolouration problems from pre-planned operations – Recommendation R7.1)
Inspection of Dee Valley Water including arrangements for Cryptosporidium sampling and follow-up of recommendations made in the 1999 inspection report.
Mr A Hallas, Inspector, carried out an inspection of Dee Valley Water in a visit between 4 and 5 December 2000. Mr Hallas concluded that:
there were four recommendations made as a result of the 1999 inspection and eighteen recommendations following the DERA audit of computer systems during August 2000 into to which the Company has responded positively.
The public record, as audited, satisfies the requirements of Part VII of the regulations.
The arrangements for the regulatory monitoring for cryptosporidia were satisfactory.
The Compliance Programme operated by the Company was on target to comply with the undertakings by the due date.
The water treatment works at Boughton was being operated and controlled satisfactorily at the time of the inspection.
Inspection of distribution system improvement programme progress
In August 2000, Consultants Ewan Associates, represented by Mrs A Eggington and Mr G Shuker, 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 Mrs Eggington and Mr Shuker’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, 29 recommendations were conveyed to the Company for formal response, eighteen of the recommendations related to the investigation of computer systems and related data management. Five suggestions related to the investigation of computer systems and data management. The Company is taking action or has already taken action on all of the recommendations.
Improvement programmes
One undertaking in respect of an improvement programme accepted by the Secretary of State from the Company was due for full completion or the completion of major steps during 2000 and it was completed on schedule. The ongoing distribution system improvement programmes due for completion in 2004, which have been implemented by the Company, have been progressing satisfactorily.
Incidents
No events regarded as constituting incidents in which drinking water quality demonstrably deteriorated came to the attention of the Inspectorate in 2000.
Enforcement action
Table 6.4 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 6.1Dee Valley Water plc
MICROBIOLOGICAL QUALITY OF WATER LEAVING TREATMENT WORKS2000 1999 1998 Number of water treatment works 8 8 8 Works with no sampling shortfall 8 8 8 COLIFORMS Total number of determinations 1,376 1,405 1,402 - number containing coliforms 1 4 2 - % containing coliforms 0.1 0.3 0.1 Treatment works with coliforms detected 1 2 1 - % of all works 12.5 25 12.5 FAECAL COLIFORMS Total number of determinations 1,376 1,405 1,402 - number containing faecal coliforms 0 0 0 - % containing faecal coliforms 0.0 0.0 0.0 Treatment works with faecal coliforms detected 0 0 0 - % of all works 0 0 0
table 6.2 Dee Valley Water plc
MICROBIOLOGICAL QUALITY OF WATER IN SERVICE RESERVOIRS2000 1999 1998 Number of service reservoirs 31 31 32 Service reservoirs with no sampling shortfall 31 31 32 COLIFORMS Total number of determinations 1,580 1,612 1,607 - number containing coliforms 2 7 7 - % containing coliforms 0.1 0.4 0.4 Service reservoirs with coliforms detected 2 7 7 Service reservoirs with coliforms detected in more than 5% of samples 0 0 0 - % of all service reservoirs 0 0 0 FAECAL COLIFORMS Total number of determinations 1,580 1,612 1,607 - number containing faecal coliforms 2 0 2 - % containing faecal coliforms 0.1 0.0 0.1 Service reservoirs with faecal coliforms detected 2 0 2 - % of all service reservoirs 6.5 0 6
table 6.3 Dee Valley Water plc
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 (18 in 2000)* Total Contravening PCV Non-compliant No. % CBU CBU E Number in: 2000 2000 1999 1998 Coliforms 778 0 0.0 0 0 0 0 2 0 Faecal coliforms 778 0 0.0 0 0 0 0 0 0 Colour 112 0 0.0 0 0 0 0 0 0 Turbidity 126 2 1.6 0 0 0 1 0 0 Odour 112 0 0.0 0 0 0 0 0 0 Taste 112 0 0.0 0 0 0 0 0 0 Hydrogen ion 569 0 0.0 0 0 0 0 0 0 Nitrate 112 0 0.0 0 0 0 0 0 0 Nitrite 112 1 0.9 0 0 0 1 3 1 Aluminium 163 1 0.6 0 4 0 1 1 0 Iron 184 3 1,6 1 4 0 3 1 0 Manganese 158 1 0.6 0 3 0 1 1 1 Lead 82 0 0.0 0 0 0 0 1 0 PAH 72 0 0.0 0 0 0 0 0 0 Trihalomethanes 72 0 0.0 0 0 0 0 0 0 Total pesticides 96 0 0.0 0 0 0 0 0 0 Other pesticides 1,513 0 0.0 0 0 0 0 0 0 All Others 1,765 0 0.0 0 0 0 0 0 0 TOTAL 6,916 8 0.1 1 - - - - - *18 Zones in 1999; 18 Zones in 1998
table 6.4 Dee Valley Water plc
SUMMARY OF ENFORCEMENT ACTION CONSIDERED IN 2000Regulation Reason for Enforcement 3(3)c Contravention of the turbidity standard in one zone
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Published 11 July 2001
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