16 SEVERN TRENT WATER LIMITED
Introduction
The Company supplies on average 2,000 Ml/d of water to a population of approximately 7.36 million people within a region that broadly covers the catchment areas of the Rivers Severn and Trent and their tributaries. The region thus stretches from the Humber estuary in the north to the Bristol Channel in the south and from Llyn Clywedog in Wales in the west to Lincolnshire in the east. The region includes the cities of Birmingham, Coventry, Derby, Gloucester, Leicester, Nottingham, Shrewsbury, Stoke-on-Trent and Worcester.
Underground sources, river derived sources and impounding reservoirs each provide 35%, 40% and 25% respectively of the total volume of water put into supply.
The Company operated 164 water treatment works in 2000. The average volumes of water treated at works ranged from 335 Ml/d at Frankley, which supplies Birmingham, to small plants which treat less than 1 Ml/d. Treated water was distributed via 614 service reservoirs and 41,000 km of water mains. The area was divided into 286 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 231,111 determinations in 2000. Of these, 99.90% demonstrated compliance with the relevant PCV, but 243 showed a contravention to have occurred.
Coliforms were not detected at 153 (93%) of the Company's 164 water treatment works. At all of the Company's 614 service reservoirs, coliforms were absent from at least 95% of samples. Of the Company's 286 water supply zones in 2000, 284 (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 2 (1%) of zones, breaches have resulted in consideration of enforcement action.
Microbiological quality of water leaving treatment works
The Company complied with the sampling frequencies required by regulation 17 at 163 of its 164 treatment works in 2000. The shortfall is regarded as trivial.
Table 16.1 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.
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 328 of its 614 service reservoirs in 2000. Shortfalls at the other 286 resulted from difficulties encountered in collecting samples during the fuel crisis and are regarded as trivial and unlikely to recur.
Table 16.2 shows the Company's performance in 2000, with data 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.
All contraventions of the standards at service reservoirs are considered trivial or unlikely to recur as a result of remedial actions taken by the Company.
Water quality in water supply zones
The Company failed to comply with the required sampling frequencies for copper, lead and zinc in one zone and iron, turbidity, or both, in 10 zones. All shortfalls in zones were considered trivial and unlikely to recur.
Table 16.3 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 lead. All other differences in zones are not considered significant.
Enforcement action is being considered in respect of some contraventions of standards, as shown in tables 16.3 and 16.4. All other contraventions of the standards in zones are considered trivial, or a covered by undertakings.
Inspection
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 Severn Trent Water in October 2000. Based on Mr Walls' report Mr Waite concluded that:
the sampling and analytical arrangements are generally satisfactory;
there are deficiencies in the analysis of fenpropimorph and iron on occasions which the Company did not investigate at the time;
issuing exception reports may be longer than desirable when it relies on transfer of files between data bases; and
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 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’ programmes of works to comply with the new lead standards. Based on Mr Ntifos’ 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 (by correspondence only) of response to recommendations made in 1999 inspection reports
Dr K J White, Inspector, carried out an inspection of Severn Trent Water in December 2000. Dr White concluded that:
the Company made a positive response to the recommendations made in the 1999 inspection report.
Inspection of distribution system improvement programme progress
Consultants John Champion Ltd, represented by Mr N Jones, working under the direction of Mr P Halton, Inspector, made two visits to the Company in October 2000 and January 2001 to carry 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 Jones’ 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, 10 recommendations were conveyed to the Company for formal response, most concerning analytical arrangements. The Company is taking action or has already taken action on a number of the recommendations.
Improvement programmes
Two 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 both of these were completed on schedule.
The ongoing distribution system improvement programmes due for completion in 2003, which have been implemented by the Company, have been progressing satisfactorily.
Relaxations
The Secretary of State had authorised relaxations of the PCV for iron and manganese in zones supplied by one treatment works and for magnesium in zones supplied by another works, subject to review by 31 December 1999. As a result of the review the relaxations were renewed subject to review by 25 December 2003.
Incidents
Nineteen 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
Fifteen incidents have been assessed. Twelve of these involved the supply of discoloured water. Areas affected were parts of Sutton-in-Ashfield and Wolverhampton in January; Malvern, Ilkeston and Derby in February; Walton in May; south Birmingham in June; Ripley and Hackenthorpe in August; Leamington Spa in September; and Broxtowe and Droitwich in December. Two incidents involved wholesomeness concerns following low level bacteriological failures, one relating to the distribution system in Whitchurch in June the other at a service reservoir in Church Stretton in November. One incident concerned loss of supply and discolouration following a sensor failure at a service reservoir at Selston in October. In each of the above incidents the problem was of short duration and the Company took effective remedial action.
Four incidents remain under consideration. Three of these relate to the supply of discoloured water and one to a sensor failure.
No other events regarded as constituting incidents came to the attention of the Inspectorate in 2000.
Also during 2000, assessment was completed of an incident in Leicester in February 1998. Discoloured water occurred in a small area of Aylestone. Over the next few days several hundred people in the area suffered illness in the form of diarrhoea and vomiting. The cause of the discolouration of water supplies and the illness and whether the two are linked is uncertain.
Enforcement action
Table 16.4 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 16.1 Severn Trent Water Limited
MICROBIOLOGICAL QUALITY OF WATER LEAVING TREATMENT WORKS2000 1999 1998 Number of water treatment works 164 168 179 Works with no sampling shortfall 163 168 179 COLIFORMS Total number of determinations 15,571 19,646 20,580 - number containing coliforms 15 19 16 - % containing coliforms 0.1 0.1 0.1 Treatment works with coliforms detected 11 15 15 - % of all works 7 9 8 FAECAL COLIFORMS Total number of determinations 15,571 19,646 20,579 - number containing faecal coliforms 0 0 1 - % containing faecal coliforms 0.0 0.0 <0.1 Treatment works with faecal coliforms detected 0 0 1 - % of all works 0 0 1
table 16.2 Severn Trent Water Limited
MICROBIOLOGICAL QUALITY OF WATER IN SERVICE RESERVOIRS2000 1999 1998 Number of service reservoirs 614 645 656 Service reservoirs with no sampling shortfall 328* 645 656 COLIFORMS Total number of determinations 31,241 32,234 33,314 - number containing coliforms 44 38 53 - % containing coliforms 0.1 0.1 0.2 Service reservoirs with coliforms detected 37 34 47 Service reservoirs with coliforms detected in more than 5% of samples 0 1 4 - % of all service reservoirs 0 <1 1 FAECAL COLIFORMS Total number of determinations 31,241 32,234 33,316 - number containing faecal coliforms 4 4 11 - % containing faecal coliforms <0.1 <0.1 <0.1 Service reservoirs with faecal coliforms detected 4 4 10 - % of all service reservoirs 1 1 2 * Company unable to collect samples during the fuel crisis. These shortfalls are considered trivial and unlikely to recur.
table 16.3 Severn Trent Water 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 (286 in 2000)* Total Contravening PCV Non-compliant No. % CBU CBU E Number in: 2000 2000 1999 1998 Coliforms 20,028 83 0.4 0 0 0 0 0 0 Faecal coliforms 20,028 5 <0.1 0 0 0 5 5 5 Colour 1,488 0 0.0 0 0 0 0 0 0 Turbidity 4,038 3 <0.1 1 105 0 3 1 0 Odour 1,281 0 0.0 0 0 0 0 0 2 Taste 1,407 1 <0.1 0 0 0 1 0 0 Hydrogen ion 1,682 0 0.0 0 0 0 0 0 1 Nitrate 5,309 0 0.0 0 0 0 0 0 0 Nitrite 1,568 4 0.2 0 0 0 2 1 3 Aluminium 1,602 2 0.1 0 0 0 2 0 2 Iron 4,748 29 0.6 16 105 2 20 17 30 Manganese 1,636 3 0.2 0 0 0 3 2 3 Lead 624 3 0.5 0 12 0 2 7 17 PAH 956 42 4.3 0 9 0 17 16 21 Trihalomethanes 692 0 0.0 0 0 0 0 0 0 Total pesticides 1,310 0 0.0 0 0 0 0 0 0 Atrazine 1,300 0 0.0 0 0 0 0 0 1 Mecoprop 0 0 0.0 0 0 0 0 0 1 Other pesticides 5,078 0 0.0 0 0 0 0 0 0 Benzo-3,4-pyrene 958 5 0.5 0 0 0 0 2 0 Phosphorous 755 0 0.0 0 0 0 0 1 0 Oxidisability 329 0 0.0 0 0 0 0 1 0 All others 60,670 0 0.0 0 0 0 0 0 0 TOTAL 137,487 180 0.1 17 - - - - - *289 zones in 1999; 303 zones in 1998.
table 16.4 Severn Trent Water Limited
SUMMARY OF ENFORCEMENT ACTION CONSIDERED IN 2000Regulation reason for enforcement 3(3)(c) Contravention of the standard for iron in two zones.
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Published 11 July 2001
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