The Hodder and Thirlmere Aqueduct Access Gates
Compiled & Researched by the Nutters Mobile Surveillance Unit

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Summary Report for 1999 on North West Water Limited

see also lostock/rivington works contract

(for archive/historical purposes, these documents have not been updated)

Index of Contents:

  1. Introduction
  2. Bacteria
  3. Lead
  4. Iron and Manganese
  5. Cryptosporidium
  6. Drinking Water Quality Incidents
  7. Prosecutions
  8. Determinations in 1999

1. Introduction

The Drinking Water Inspectorate (DWI) checks that water companies supply water that is safe to drink when it reaches your home. This document summarises the results of our checks on North West Water Limited during 1999 and should be read in conjunction with DWI's "How Good is the Drinking Water?" leaflet which is available here and also from us free of charge from the address at the end of this document.

North West Water continues to supply you with drinking water of a high quality. In 1999, 99.69% of more than 354,000 tests met the standards. This is below the overall figure for England and Wales of 99.82%.

None of the failures in 1999 were likely to harm consumers' health. We assessed each one and, where necessary, we have required North West Water to take action to prevent further failures.

Although the 1999 results are good, we know that there are some matters of everyday concern to consumers. These are detailed below including the steps taken by North West Water to further improve its performance.

2. Bacteria

Whenever bacteria are found in water samples North West Water investigates immediately. Low numbers of bacteria were detected on 42 occasions in 1999 in water leaving treatment works and on 40 occasions in water leaving service reservoirs. These figures represent a significant decrease over previous years. Bacteria were detected in 0.5% of samples from consumers' taps. The bacteria found were not harmful to consumers' health. Many of these detections could be due to the condition of the taps and not the water itself. Although the Company has taken some remedial action to prevent further failures, the Inspectorate has required the Company to carry out improvements in respect of bacteria in one zone, and in respect of bacteria at five treatment works.

3. Lead

Samples occasionally fail the standard for lead, even where additional treatment has been installed to reduce the amount of lead picked up by water from pipework. In many cases this is due to the consumer's water pipes being made of lead. In all cases the householder has been informed of things they can do to reduce lead levels at their tap. The Inspectorate has required the Company to take action to reduce the risk of failing the standard in a further 11 zones. The Drinking Water Inspectorate advises consumers living in properties with lead pipes to seek advice from their water company. A DWI leaflet about lead in drinking water is also available from the address at the end of this document.

4. Iron and Manganese

These two parameters provide a good indication of the overall condition of the mains used to distribute drinking water through the region.

The number of zones failing the standard for iron and manganese has shown a steady decrease since 1996. This reflects the programme of work being carried out by North West Water to renovate the distribution system. The programme is ongoing with the Company being required to renovate more than 7688km of mains by 2010.

5. Cryptosporidium

Cryptosporidium is a tiny micro-organism that can sometimes cause a form of diarrhoea called cryptosporidiosis. There are a number of sources of Cryptosporidium other than water but due to new regulations water companies are now required by law to sample continuously and analyse daily for Cryptosporidium in the treated water at those sites which have a potential vulnerability. All water companies had to initially conduct risk assessments at their sites to identify if there was any significant risk of contamination. North West Water identified that there was significant risk at 54 of its sites. It has installed continuous sampling and monitoring of the treated water at some of these sites and will complete the remainder by the end of this year except for 11 sites which the Company considers it likely will be shut down. At all sites where monitoring is installed, the Company is required to ensure adequate treatment is in place and it is an offence if the new treatment standard for Cryptosporidium is exceeded. In addition to the regulatory requirement, the Company is able to get early warning of any treatment problems from this monitoring system.

6. Drinking Water Quality Incidents

Twenty seven incidents were notified to the Inspectorate during 1999. Of the 15 incidents that have been assessed, 14 involved the supply of discoloured water. Those which affected parts of Bolton (January), Bootle (January), Brampton (March), Culcheth (February), Darwen (May), Liverpool (January), Manchester (November), South Wirral (January) and St Helens (April) arose as a result of burst mains or planned work on the distribution system. The incident at Little Sutton (May) was associated with an increased output from the water treatment works and that at Preston (May) with a failure of a valve. Two incidents arose as a result of a deterioration in raw water quality and affected Newchurch-in-Pendle (September) and Hausegill (December). Discoloured water supplies to parts of Lancaster (October) were associated with trials at a water treatment works. One further incident involved the detection of Cryptosporidium oocysts in treated water at Forest Farm pumping station (September). In each of the above incidents the problem was of short duration and the Company took effective remedial action.

The assessment remains to be completed for the incidents involving the supply of water with a taste and odour to Nantwich (January), Oldham (May), Preston (January and December) and Warrington (July); the supply of discoloured water to Atherton (December), Blackburn (July), Macclesfield (January), Rainford (February), Wallasey (December) and Wigan (May). The assessment also remains to be completed of the outbreak of cryptosporidiosis in the North West Region in April 1999.

During 1999, assessment was completed of incidents which occurred in 1997 involving the supply of discoloured water to parts of Coniston (September); Carlisle (December); Freckleton (December) and Preston (November). Assessment was also completed of incidents which occurred in 1998 involving the supply of discoloured water to parts of Allerdale (August); Barrow (May); Great Sankey (April); Manchester (April); Preston (July); Preston (September); Thornton Cleveleys (September); Walney Island (October); parts of Preston supplied from Whitebull water treatment works (May); and parts of Stockport supplied from Wybersley water treatment works (January). Assessment was also completed of the incidents involving detection of bacteriological contamination in Bollington (October 1998); an increase in the number of cases of cryptosporidiosis in Wigan (June 1997); and a failure of disinfection at Burton water treatment works (August 1998).

7. Prosecutions

During 1999, the Inspectorate completed its assessment of the discoloured water incident in Preston in November 1997 which arose as a result of problems with the clarification stage of the treatment at Franklaw water treatment works. The Inspectorate initiated legal action and the Company pleaded guilty to supplying water unfit for human consumption at Preston Magistrates Court on 15 November 1999 and was fined a total of 3,000 with 3,646 costs.

The incident in Freckleton in December 1997 also involved the supply of discoloured water and arose when valves were operated to isolate a main to be rehabilitated. Water flowed in a direction opposite to normal and when cross connections were opened, discoloured water was supplied. The Inspectorate initiated legal action and the Company pleaded guilty to supplying water unfit for human consumption at Blackpool Magistrates Court on 3 November 1999 and was fined a total of 6,000 with 4,455 costs.

In Rainhill in December 1998, discoloured water was supplied following the return to service of one compartment of Crank Service Reservoir following cleaning. Deposits were disturbed and discoloured water supplied. The Inspectorate initiated legal action and the Company pleaded guilty to supplying water unfit for human consumption at St Helens Magistrates Court on 25 January 2000 and was fined a total of 2,500 with 5,036 costs.

Following the incidents the Company revised its procedures and has since taken remedial action to prevent them recurring.

8. Determinations in 1999



Contravening PCV
No %
Coliforms 22170 107 0.5
Faecal coliforms 22170 13 0.1
Colour 13618 0 0.0
Turbidity 13632 19 0.1
Odour 2980 2 0.1
Taste 2969 0 0.0
Hydrogen ion 7937 11 0.1
Nitrate 4379 5 0.1
Nitrite 4381 5 0.1
Aluminium 15819 18 0.1
Iron 15819 345 2.2
Manganese 15820 42 0.3
Lead 15574 325 2.1
PAH 1991 19 1.0
Trihalomethanes 3281 85 2.6
Total pesticides 2703 1 < 0.1
2,4-D 1761 0 0.0
Atrazine 1758 0 0.0
Dichlorprop 1765 1 0.1
Diuron 1524 0 0.0
Gamma-HCH 1759 1 0.1
MCPA 1761 0 0.0
Mecoprop 1761 1 0.1
Other pesticides 18462 0 0.0
Ammonium 4379 2 < 0.1
Benzo 3,4 pyrene 1989 1 0.1
Cadmium 322 0 0.0
Copper 1416 1 0.1
Oxidisability 581 1 0.2
Phosphorus 16749 11 0.1
Potassium 392 1 0.3
Surfactants 334 0 0.0
Temperature 4056 0 0.0
All others 38418 0 0.0
Total 264430 1017 0.4

Drinking Water Inspectorate,
Floor 2/A1, Ashdown House, 123 Victoria Street, London, SW1E 6DE
Telephone : 020 7944 5956 - Facsimile : 020 7944 5969

Published 12 July 2000 / Updated 11 July 2001