22 Three Valleys Water Plc
Overall Water Quality supplied by Three Valleys Water Plc in 2001
- A total of 93,440 tests were carried out by Three Valleys Water Plc in 2001.
- Of these tests, 99.85% complied with the Regulations.
Company Information
Amount of Water Supplied: 876 Ml/d
Consumers Supplied: 2.9 million
Areas of Supply: Parts of Bedfordshire, Berkshire, Buckinghamshire, Essex, Hertfordshire, Surrey, Middlesex and several London Boroughs
Water Composition: 42% from rivers and reservoirs
58% from boreholes and aquifers
Treatment Works: 83
Service Reservoirs: 137
Km of Mains: 13,500
Water Supply Zones: 110Water Quality in Water Supply Zones, at Treatment Works, and in Service Reservoirs
Water supply zones
- To be wholesome, water must comply with the standards set out in the Regulations. The Company carried out a total of 59,776 tests on samples taken in its 110 water supply zones. The table below includes only the parameters that breached the standard; all other parameters were fully compliant. A list of these parameters and their significance can be found at the beginning of this section.
- The last column indicates the number of failures in zones already covered by legally binding undertakings given by the Company. These undertakings required remedial works to be carried out to ensure compliance with the individual standard.
Parameter Total samples taken Samples not meeting the standard Percentage Number of failures already covered by undertakings Total coliforms 7880 27 0.34 0 Faecal coliforms 7891 7 0.09 0 Turbidity 5970 1 0.02 1 Nitrate 936 3 0.32 0 Nitrite 936 68 7.26 0 Iron 2051 6 0.29 4 Lead 572 1 0.17 0 PAH 282 3 1.06 0 Chlorotoluron 227 1 0.44 0 Oxidisability 122 1 0.82 0 Surfactants 117 1 0.85 0
Treatment works
- Of the Company's 83 treatment works, 78 (94%) complied fully with the relevant standards. Failures of the standards at a total of five works were considered trivial, or unlikely to recur as a result of remedial action taken or being taken by the Company. 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 were not considered significant.
Service reservoirs
- At all of the Company's 137 service reservoirs, coliforms were absent from at least 95% of samples. Failures of the faecal coliform standard at two service reservoirs were considered trivial or unlikely to recur. Differences over the last three years in the number of service reservoirs, and samples from service reservoirs, in which coliforms or faecal coliforms were detected were not considered significant.
Cryptosporidium
- The Company carried out a total of 2,621 tests on samples taken from nine sites. Very low numbers of oocysts were detected in 42 (1.6%) samples taken from eight sites. All results were well below the treatment standard and there were no associated outbreaks of cryptosporidiosis.
Company Audit and Inspection
- The Company was inspected or audited by the Inspectorate or its appointed consultants on a number of occasions during 2001. Where relevant, report summaries are available in the 'Business and Technical' section of the web site under 'Audit and Inspection'.
Audit or Inspection Date Audit of operation and maintenance of the distribution system
January Audit of incident notification procedures
February Review of plumbosolvency treatment and control programmes of work
October Audit trails of ten samples
October Review of progress with the distribution system undertaking
October Review of policies and procedures on contaminated land
November Inspections of one water treatment works and one service reservoir
November Audit of procedures for compliance with Regulation 25
November Audit of sampling programme
November Audit of arrangements for Cryptosporidium analysis
November Audit of all Cryptosporidium sampling sites
Various dates during the year
- Twenty-one recommendations were made in respect of action required to avoid the risk of a breach of a regulatory duty. These recommendations were mainly in relation to the operation and maintenance of the distribution system.
- Eleven recommendations for improvements were made in respect of the distribution system undertaking and plumbosolvency treatment for lead.
Incidents
- The Inspectorate regarded 11 of the events notified during 2001 by the Company as incidents. For further details on the classification of incidents see Chapter C, 'Events affecting Water Quality', in Part 3.
- All incidents have been assessed by the Inspectorate. They were of short duration and the Company has taken appropriate remedial action. Five recommendations were made to the Company regarding operations and maintenance of records.
Nature of incident
No.of incidents
Assessment completed by DWI
Areas affectedSupply of discoloured water
1
Yes
Epping (August)
Microbiological contamination of supplies
6
Yes
Stevenage (August); Colesdale (August); West Horsley (August); Winkfield (September); Barnet (November); Ware (August)
Supply of water with objectionable taste & odour
2
Yes
Stapleford (June); Great Kingshill (October)
Wholesomeness concerns
2
Yes
Finchley (October); Wraysbury (November)
Improvement Programmes
- No remedial programmes of work were due for completion during 2001.
- The Inspectorate is currently discussing with the Company progress made to date with its ongoing distribution system improvement programme, which is behind schedule in respect of length of mains renovated. During 2000 and 2001, 135 km of mains were renovated. The Company is required to renovate a further 1,073 km of mains by March 2008.
- The Company has improvement programmes to meet the new and revised standards set down in the new Water Supply (Water Quality) Regulations 2000, which will come into force on 25 December 2003. These relate to bromate at five sites and solvents at two sites, plus additional work required to meet the new standard for lead. The Company also has programmes of work to reduce any potential risk from Cryptosporidium oocysts at 14 sites; four of these have now been completed. Progress with delivery of the remaining programmes is monitored by the Inspectorate and has been satisfactory.
Enforcement Action
- The table below indicates areas where, in 2001, the Inspectorate considered taking enforcement action for regulatory breaches, and where an undertaking was submitted or where the Company took appropriate action.
Parameter/Area Regulation breached Location Outcome Nitrate Reg 3(3)(c) Baldock/Letchworth and Royston zones Undertaking received
table 22.1 Three Valleys Water plc
MICROBIOLOGICAL QUALITY OF WATER LEAVING TREATMENT WORKS2001 2000 1999 Number of water treatment works 83 77 76 Works with no sampling shortfall 81 73 72 COLIFORMS Total number of determinations 9,788 7,857 7,351 - number containing coliforms 6 10 5 - % containing coliforms <0.1 0.1 <0.1 Treatment works with coliforms detected 5 8 5 - % of all works 6.0 10.4 6.6 FAECAL COLIFORMS Total number of determinations 9,795 7,857 7,351 - number containing faecal coliforms 2 2 0 - % containing faecal coliforms <0.1 <0.1 0.0 Treatment works with faecal coliforms detected 2 2 0 - % of all works 2.4 2.6 0.0
table 22.2 Three Valleys Water plc
MICROBIOLOGICAL QUALITY OF WATER IN SERVICE RESERVOIRS2001 2000 1999 Number of service reservoirs 137 117 117 Service reservoirs with no sampling shortfall 135 116 114 COLIFORMS Total number of determinations 7,038 5,928 6,069 - number containing coliforms 8 10 4 - % containing coliforms 0.1 0.2 <0.1 Service reservoirs with coliforms detected 8 9 3 Service reservoirs with coliforms detected in more than 5% of samples 0 0 0 - % of all service reservoirs 0.0 0.0 0.0 FAECAL COLIFORMS Total number of determinations 7,043 5,928 6,069 - number containing faecal coliforms 2 1 1 - % containing faecal coliforms <0.1 <0.1 <0.1 Service reservoirs with faecal coliforms detected 2 1 1 - % of all service reservoirs 1.5 0.9 0.9
table 22.3 Three Valleys 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 2001. Column 'E' shows the number of zones for which new enforcement action is under consideration as a result of contraventions of the PCV in 2001. PARAMETER DETERMINATIONS in 2001 ZONES (110 in 2001)* Total Contravening PCV Non-compliant No. % CBU CBU E Number in: 2000 2001 2000 1999 Coliforms 7,880 27 0.3 0 0 0 0 0 0 Faecal coliforms 7,891 7 0.1 0 0 0 7 1 2 Colour 569 0 0.0 0 0 0 0 0 0 Turbidity 5,970 1 0.0 1 26 0 1 3 2 Odour 656 0 0.0 0 0 0 0 0 0 Taste 656 0 0.0 0 0 0 0 0 0 Hydrogen ion 5,940 0 0.0 0 0 0 0 0 0 Nitrate 936 3 0.3 0 0 0 2 0 0 Nitrite 936 68 7.3 0 0 0 9 7 11 Aluminium 599 0 0.0 0 0 0 0 0 0 Iron 2,051 6 0.3 4 26 0 6 5 5 Manganese 576 0 0.0 0 0 0 0 0 0 Lead 572 1 0.2 0 0 0 1 5 4 PAH 282 3 1.1 0 0 0 3 3 9 Trihalomethanes 256 0 0.0 0 0 0 0 0 0 Total pesticides 620 0 0.0 0 0 0 0 0 0 Atrazine 420 0 0.0 0 0 0 0 3 0 Chlortoluron 227 1 0.4 0 0 0 1 0 0 Dichlobenil 142 0 0.0 0 0 0 0 0 1 Other Pesticides 4,141 0 0.0 0 0 0 0 0 0 Copper 198 0 0.0 0 0 0 0 0 1 Oxidizability 122 1 0.8 0 0 0 1 0 0 Surfactants 117 1 0.9 0 0 0 1 0 0 Temperature 7,788 0 0.0 0 0 0 0 0 1 All others 10,231 0 0.0 0 0 0 0 0 0 TOTAL 59,776 119 0.2 5 - - - - - *98 zones in 2000; 95 zones in 1999. [ Previous ] [ Contents ] [ Next ]
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Drinking Water Inspectorate,
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Telephone : 020 7944 5956 - Facsimile : 020 7944 5969
E-mail: dwi.enquiries@defra.gsi.gov.uk
Published 10 July 2002
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