Part 2 Individual Water Company Performance in 2000
KEY POINTS:
- contents of individual company sections described;
- except where noted, all companies complied with the Regulations;
- How compliance with water quality standards is assessed;
- significance of contraventions of PCVs;
- triviality criteria and enforcement action
- what the tables mean;
- comparison of water quality between companies is not straightforward;
- limitations of "percentage of determinations complying"; and
- comparison of zones complying a better measure of progress.
Introduction
This part of the report contains a separate section on each of the 26 water companies, and a section on the one Inset Appointment (see the Regulatory Framework Section). The sections summarise the extent of compliance during 2000 with the requirements of the Water Supply (Water Quality) Regulations 1989, (the "Regulations") as amended. Each section contains:
- an introduction which gives a summary of the company's water supply arrangements;
- a general statement about overall water quality which shows the extent to which the company's water treatment works, service reservoirs and water supply zones complied with the Regulations in 2000;
- more detailed information on compliance with sampling frequencies and the extent to which the company met the relevant water quality standards in 2000 itself and in comparison with 1999 and 1998 (but see paragraphs 30 onwards);
- conclusions and numbers of recommendations and suggestions from inspections of the company;
- a summary of progress with improvement programmes associated with undertakings given by the company or with conditions of relaxations authorised under regulation 4;
- a summary of any events regarded by the Inspectorate as constituting incidents in which drinking water quality demonstrably deteriorated;
- where considered appropriate, details of any other notable events concerning water quality which came to the Inspectorate's attention in 2000; and
- a summary of the enforcement action (if any) considered for the company as a result of the Inspectorate's work in, or pertaining to, the calendar year 2000.
Except where stated to the contrary, the assessment of drinking water quality data for 2000, the findings of inspection in 2000 and the assessment in 2000 of any drinking water quality incidents showed that each company complied fully with the Regulations.
Assessment of compliance (general points)
Schedule 3 of the Regulations refers to the number of samples required to be taken for each parameter. In practice, water companies test each sample for several parameters so the text and the tables in the company sections relate to the number of determinations made of each individual parameter rather than to the number of samples taken.
The number of samples per annum specified in Schedule 3, is the minimum which a company is required to take in the various situations to which the Schedule refers. For 2000, the Inspectorate has looked for full compliance with the required sampling frequencies. Only where the annual requirement is for 50 samples or more has any shortfall been considered trivial, and then only to the extent of 2% of the requirement. Enforcement action is being considered in all other cases where shortfalls have been detected and the company has not taken steps to prevent a recurrence.
The term "total coliforms" refers to the parameter listed in Table C of Schedule 2 of the Regulations. It includes all coliform organisms whether faecal in origin or not. In the following sections, the term "coliforms" has been used for the total coliforms parameter to simplify the text. The detection of coliforms in a sample does not mean it is likely that the water supply will cause disease but is indicative of potential contamination which must be investigated immediately. The presence of faecal coliforms in the same sample would very probably mean that the contamination was of faecal origin and that, although disease was still very unlikely to result, urgent action must be taken to identify and eradicate the source of the contamination.
Water leaving treatment works and in service reservoirs and water supply zones is sampled for faecal streptococci and sulphite-reducing clostridia for investigative purposes only; there is no regulatory requirement to sample for these parameters. However, when a water company has carried out determinations for these parameters and supplied the information as part of its compliance information, the number of determinations and any breaches of the standards have been included in the assessment of water quality.
A few parameters specified in the Regulations have no prescribed concentration or value (PCV) assigned to them. These are: total organic carbon, colony counts, residual disinfectant, taste (qualitative) and odour (qualitative). Although all have an assigned sampling frequency, the absence of a PCV means that it is not appropriate to include the number of their determinations in the overall total of compliance determinations carried out by a company. However, any instances of failure to comply with the required sampling frequency have been included in the assessment of each company and, where not regarded as trivial, enforcement action is under consideration.
The parameters alkalinity and total hardness have a PCV assigned to them only for water which is artificially softened. The PCV in this case is a minimum value which must be exceeded. All determinations for these parameters made on samples taken to determine compliance have been included in the overall total of compliance determinations whether or not the supply has been artificially softened. The number and percentage of all individual determinations below the minimum value have been shown in the table on water quality in supply zones. However only those zones (if any) which received artificially softened water are included in the part of the table listing non-compliant zones.
Assessment of water quality at treatment works
Regulation 3(7) requires 100% compliance with water quality standards for coliforms and faecal coliforms at water treatment works. For 2000, the Inspectorate has generally regarded the detection of coliforms and faecal coliforms on a single occasion at most treatment works as a trivial breach of the standards unless there was a similar breach at that works in 1999. For works supplying more than 12,000 m3/d and not being sampled at the reduced frequency under the provisions of regulation 17(2), and thus being sampled daily for these parameters, a breach on a single occasion in 2000 has been regarded as trivial without reference to 1999 results. In the case of all other breaches, the Inspectorate is considering enforcement action unless the company has taken remedial action to prevent a recurrence.
Assessment of water quality at service reservoirs
Regulation 3(7), as amended by the Water Supply (Water Quality) (Amendment) Regulations 1991, allows that if no more than 5% of samples taken in the preceding 12 months from a service reservoir contain coliforms, compliance in respect of coliforms is achieved. Compliance in 2000 has been assessed on the basis of results on samples taken from each service reservoir in the 12 months of the calendar year.
The detection of faecal coliforms in 100 ml of sample on a single occasion has been regarded as a trivial breach of the faecal coliforms standard. All other breaches of this standard and all cases of non-compliance with the coliforms standard in 2000 may result in enforcement action unless the company has taken remedial action to prevent recurrence.
Assessment of water quality in water supply zones - 'wholesomeness'
Regulation 3 prescribes concentrations or values for 55 of the 57 parameters as listed in Tables A to E of Schedule 2 to the Regulations and also for trihalomethanes. The other two parameters, colony counts and total organic carbon, do not have concentrations or values prescribed but must show no significant increase over that normally observed. In general, to be wholesome, water must not contain a parameter in excess of a PCV; total hardness and alkalinity must not be below prescribed values if the water is treated by softening or desalination, and in the case of hydrogen ion the pH value must lie in a range defined by a maximum and minimum prescribed value.
- authorised relaxations
In particular cases, the Secretary of State for the Environment, Food and Rural Affairs, or the National Assembly for Wales ("the Authorities") may authorise, under regulation 4, the relaxation of a PCV. Relaxations may be authorised in emergencies, as a result of exceptional meteorological conditions or by reason of the nature and structure of the ground in the area from which the supply emanates. Regulation 5 places certain restrictions on the authorisation of relaxations - in particular, that public health shall not be jeopardised - and also requires the specification of the extent to which the PCV of any parameter is authorised to be contravened. Therefore, the granting of an authorisation for a relaxation does not change the PCV - it merely specifies the concentration or value of a parameter that can be allowed during the period of authorisation. In most remaining cases, authorisation is subject to the completion of improvement works to achieve compliance with the PCV from the date that the relaxation expires.
In assessing water quality in water supply zones, the Inspectorate takes into account the existence of authorised relaxations. Thus, throughout the text and tables within this report, reference to contravention of a PCV means that, where a relaxation is in place, a concentration or value greater than that authorised has occurred. Concentrations or values up to the authorised concentration or value are not included in the number or percentage of PCV contraventions.
- significance of contraventions of PCVs
Although the text and tables in the individual company sections and in Part 1 make extensive reference to contraventions of PCVs, there is no evidence that any of the contraventions resulted in detectable harm to the health of consumers. Only some of the parameters are of health significance and their standards are generally set with a wide margin of safety. The other parameters are of aesthetic significance, with standards set generally well below the level at which water would become unacceptable to consumers, and contravention of their standards is not necessarily indicative that the water is unfit to drink.
Contravention of a PCV, even for only one parameter and in only one sample out of the large number taken from each water supply zone in the course of the year, is of significance because the water supplied at the time the sample was taken cannot be regarded as wholesome. That does not mean that the water was harmful to health or otherwise unfit for drinking, but it may mean, when considered in the light of other results of monitoring, that the water quality needs improvement in order to meet the high standards which the Regulations specify.
- parameters with average or percentile PCVs
The general rule that any contravention of a PCV - even if revealed by only one sample - constitutes a breach of the Regulations and thus causes the water to be regarded as unwholesome, does not apply to a few parameters specified in regulation 3. Thus, zones have been regarded as non-compliant only if:
- for trihalomethanes, the average concentration in any three-month period has exceeded 100 µg/l, the concentration prescribed in regulation 3(3)(e) ('trihalomethanes' refers to the sum of the concentrations of trichloromethane, dichlorobromomethane, dibromochloromethane and tribromomethane);
- for sodium, 20% or more of the determinations carried out in the 36 months to the end of December 2000 exceed the prescribed concentration of 150 mg/l specified in Table A and regulation 3(5);
- coliforms were detected in 5% or more of the samples taken in the 12 months of the calendar year or, where fewer than 50 samples were taken in 2000, in three or more of the last 50 samples; or
- for Table D parameters, the average concentrations or values during the calendar year 2000 exceed the prescribed concentrations or values.
In all four cases, the number and percentage of individual determinations in excess of the relevant numerical PCV is shown for each company in the table on water quality in supply zones. This is in keeping with the practice adopted in previous Reports. However, only those zones (if any) which were non-compliant for those parameters on the basis described in the previous paragraph are included in the part of the table listing non-compliant zones.
- consideration of enforcement action
For 2000, the Inspectorate has generally regarded a breach of a standard for an individual non-microbiological parameter on a single occasion in a water supply zone as trivial, provided that ten or more samples have been taken in that zone or, if a smaller number has been taken, provided that there was not a corresponding breach in 1999. In other cases, the Inspectorate has taken into account the number of determinations carried out and the number and the extent of the breaches in deciding whether the breaches were trivial or not. The Inspectorate is considering enforcement in all cases where the breaches are not regarded as trivial, unless the company has already taken remedial action to prevent a breach recurring or the Inspectorate judges that the breach is in any case unlikely to recur. For contraventions of the lead standard the Inspectorate has taken into account all determinations since 1990, or since any treatment or other steps to reduce plumbosolvency were implemented, whichever is the later, when determining whether enforcement action is required.
A single breach of the faecal coliforms standard in a water supply zone has generally been regarded as trivial. Where more than 100 samples have been taken in a zone, two breaches of the standard have been regarded as trivial, provided that neither sample contained more than two faecal coliforms in 100 ml and there was no breach of the standard in 1999. No breach of the coliforms standard (see paragraph 16) has been regarded as trivial. The Inspectorate is considering enforcement in all cases where breaches of the standard for a microbiological parameter are not regarded as trivial, unless the company has taken remedial action to prevent a breach recurring or it can demonstrate beyond reasonable doubt that the breach arose solely as a result of the condition of the consumer's plumbing or tap from which samples were taken.
- parameters with no specified sampling frequency
Sampling frequencies are not specified in the Regulations for a few parameters which have prescribed concentrations or values (Kjeldahl nitrogen, dissolved and emulsified hydrocarbons, phenols, faecal streptococci, sulphite-reducing clostridia and substances extractable in chloroform). When a water company has carried out determinations for any of these parameters and supplied the information as part of its compliance monitoring, the numbers of determinations and any breaches of the standards have been included in the assessment of water quality.
- monitoring at supply points
Samples for certain specified parameters may be taken from supply points authorised by the Authorities instead of from sampling points (consumers' taps) provided that the concentration of the parameters is unlikely to change in the water during its passage from the supply point to consumers' taps. Sampling frequencies for the various parameters at supply points are specified in Table 5 of Schedule 3 of the Regulations. The number of determinations for the parameters are included in the information on compliance for all the supply zones to which the authorisation relates. Thus, for some parameters, the number of determinations recorded can greatly exceed the actual number of determinations made because one supply point can feed a number of supply zones. Similarly a non-significant change in the number of determinations breaching the standard at a supply point may give rise to an apparently significant change in the number of zones not complying with the Regulations.
- pesticide monitoring
The number of individual pesticides monitored by each company varies according to the monitoring strategy adopted by it. Companies establish those pesticides used within catchment areas and which could reach water sources. Atrazine and simazine have been widely used in non-agricultural situations and all companies have been advised to monitor for them.
Individual pesticides are only included in the water quality tables in the section on each water company if the prescribed concentration was exceeded in any of the three years 2000, 1999 and 1998. "Other pesticides" refers to all other pesticides which were sought but found not to exceed the prescribed concentration.
The total pesticides parameter is defined in the Regulations as the sum of the detected concentrations of individual substances. In practice, the detected concentrations of whatever pesticides were determined in a particular sample are summed and compared against the prescribed concentration for total pesticides of 0.5 µg/l.
- explanation of table
The third table included in the section on each water company gives a summary of the water quality in water supply zones for the following 17 key parameters:
Coliforms Aluminium Faecal coliforms Iron Colour Manganese Turbidity Lead Odour (quantitative) Polycyclic aromatic hydrocarbons (PAH) Taste (quantitative) Trihalomethanes Hydrogen ion Total pesticides Nitrate Individual pesticides. Nitrite It can be assumed that for all other parameters the company complied in 2000 with the PCV, except where a parameter is additionally included in the table. However, any other parameters for which a breach of the PCV was recorded in 1999 or 1998 are also included in the table, even though there was no breach in 2000, so as to facilitate comparison between the three years.
The table shows, reading from left to right, the following information for each of the parameters listed:
the total number of determinations reported for compliance purposes in the calendar year 2000;
the number of determinations and the percentage of the total number of determinations which showed the numerical PCV (or the concentration or value authorised in a relaxation under regulation 4 - see paragraphs 12 and 13) for the parameter to have been contravened;
the number of those determinations which contravened the PCV but which were made on samples from zones which were covered, for the whole or part of 2000, by an undertaking or enforcement order in respect of that parameter;
the total number of zones which were covered by an undertaking in respect of that parameter for the whole or part of 2000, irrespective of whether there were contraventions in those zones;
the number of zones for which new enforcement action is under consideration or was considered as a result of contraventions of the PCV for that parameter in 2000; and
the number of zones which did not comply with the Regulations because of contraventions (including trivial contraventions) of the PCV for that parameter in each of the three years, 2000, 1999 and 1998.
The table row described 'Other pesticides' shows the number of determinations of those pesticides which, although included in the company's monitoring programme for the reasons given in paragraph 22, have not caused any contravention of the prescribed concentration for individual pesticides in 2000, 1999 or 1998. Where a company has supply point authorisation, this number may be considerably higher than the actual number carried out, for the reason given in paragraph 21.
The penultimate row of the table, described 'All others', shows the total number of determinations carried out for all parameters having a PCV but not otherwise appearing in the table. Paragraph 6 has already pointed out that parameters for which there is no PCV are necessarily excluded from compliance assessment and therefore from inclusion in the total number of determinations carried out for that purpose. The bottom row shows the grand total of all determinations and the total number of determinations showing contravention of a PCV (as explained in paragraph 13). The total number of determinations showing contravention is also shown as a percentage of the total number of determinations. The limitations of this statistic as a means of comparison between years or between companies are discussed in the paragraph 30 onwards.
When calculating percentage values, the reported figures have been rounded to the nearest whole number, or where figures are given to one place of decimals, to the nearest first decimal number. However, where rounding in this way would result in a zero but there has been one or more contraventions, the figure is expressed as less than one (<1) or less than 0.1 (<0.1) as appropriate. In earlier years calculated percentages greater than 0.5 but less than 1, or greater than 0.05 but less than 0.1, were not rounded up but reported as less than one or less than 0.1.
Comparison of water quality
The information given in the sections about water quality in each company's area indicates the extent to which the company has or has not complied with the requirements of the Water Quality Regulations. It should not be used simplistically to make comparisons of the overall quality of drinking water between different company areas or of the relative efficiency of different companies. The quality of drinking water varies within and between company areas, and depends not only on the treatment processes employed and the condition of the distribution system, but also on the nature of the source from which the water is obtained. For example, water from a borehole in a chalk aquifer would normally be of better microbiological quality than water from many other types of source. In addition, it should be noted that for all parameters, the greater the number of samples taken the more likely it is that breaches of the standards will be detected. This is not to say that meaningful comparisons of water company performance cannot be made. The Inspectorate is developing statistical procedures for categorising water companies on the basis of quality of water supplied and on efficiency of managing treatment and distribution, and results obtained using these procedures are presented in Part 1.
Provided that monitoring frequencies at individual treatment works and service reservoirs have not differed significantly in each of the three years, the tabulated data for each company on the detection of coliforms and faecal coliforms in 2000, 1999 and 1998 can be statistically compared to identify any significant changes in water quality. The commentary in each section makes reference to such changes as appropriate.
For water supply zones, differences between the number or percentage of determinations exceeding the PCV in each of the three calendar years are not necessarily of any significance. From a purely statistical viewpoint, comparison of the data for any two years must be based on the hypothesis that any differences are attributable solely to changes in the overall quality of water supplied by the company and that no other factors have varied which may have influenced the detection of breaches of the water quality standards. However, other factors which may account wholly or in part for a particular difference must be considered before drawing any conclusion about possible differences in water quality. These factors include:
- the adoption of an increased sampling frequency in accordance with regulation 13(7) as a result of breaches of a PCV for a particular parameter, which is likely to change the percentage of the total determinations of that parameter exceeding the PCV until remedial work is completed;
- the adoption of a reduced sampling frequency in accordance with regulation 13(3) for a particular parameter in appropriate zones, which may have the effect of increasing the percentage of the total determinations of that parameter exceeding the PCV in the company's area as a whole if other zones continue to be non-compliant with the standard for that parameter;
- in respect of individual pesticides, modifications to the monitoring strategy for pesticides in the light of reassessment of pesticide usage within a company's catchment area; and
- improvements in analytical systems which may have reduced or eliminated the possible contribution to earlier data of results of uncertain accuracy.
Any or all of these factors may result in an observed difference in the number or percentage of determinations showing contravention of the PCV for a particular parameter being largely a consequence of the changed sampling programme, rather than indicative of any underlying difference in water quality.
However, comparison between the three years of the number of zones showing non-compliance with the PCV for a particular parameter is rather less affected by the factors set out in the previous paragraph. Although the first of the factors may result in an increased number of determinations showing contravention of the PCV, the increased sampling frequency will only have been adopted because of an initial contravention and the zone will be non-compliant regardless of the number of contraventions. The second factor should apply only to those zones in which contravention is unlikely. The third factor may significantly influence a comparison - but only in respect of pesticides. The fourth factor may have been important in the past but the Inspectorate's enforcement of high standards of analysis has ensured that all methods now used achieve the required performance. It is now considered unlikely to have a significant effect on the comparison of zone compliance.
In the light of this consideration, this Report shows for each company the number of zones non-compliant for each of the tabulated parameters in each of the three years, 2000 1999 and 1998, on the basis that this provides a reasonable illustration of any changes in water quality over those three years. However, it must still be borne in mind that zones in which only a single, trivial contravention of a PCV occurred will be included in the total number of non-compliant zones together with zones in which the contraventions were more extensive.
In order to focus attention on the extent to which water supply zones are compliant with the standards for water quality, this Report includes for each company, under the heading "Overall water quality", a statement of:
- the number of water supply zones which complied fully with the relevant water quality standards, had only trivial breaches of the standards, or had breaches which, while not trivial, were covered by an undertaking given by the company to the Authorities that work to deal with the breaches will be carried out; and
- the number of water supply zones which had breaches which were neither trivial nor covered by undertakings.
Zones in the second category may be candidates for enforcement action, or it may be that the Inspectorate is already satisfied that, for some or all of them, remedial work has already been carried out or that the breaches are unlikely to recur. The commentary on water quality in water supply zones provides more detail.
The fourth table included in the section on each water company records all instances, and only those instances, in which the Inspectorate has written formally to the Company advising it that enforcement action is under consideration. While the outcome of such notification may be the submission of an undertaking, the Company may be able to show that action has already been taken and enforcement is not required. This is explained in more detail in Part 3 E.
Because enforcement action can be initiated at any time during the year, zones may appear in the third table in the section on each water company both in column seven as having been the subject of consideration of enforcement action, and in column six as having been covered by an undertaking for all or part of the year.
Water and Sewerage Companies and Water-Only Companies of England and Wales
- Anglian Water Services Limited
- Bournemouth and West Hampshire Water PLC
- Bristol Water PLC
- Cambridge Water Company
- Cholderton and District Water Company Limited
- Dee Valley Water PLC
- Dwr Cymru Cyfyngedig
- Essex and Suffolk Water PLC
(part of Northumbrian Water Limited- Folkestone and Dover Water Services Limited
- Hartlepool Water PLC (part of Anglian Water Group)
- Mid Kent Water PLC
- North Surrey Water Limited
(part of Three Valleys Water PLC)- North West Water Limited
- Northumbrian Water Limited
- Portsmouth Water PLC
- Severn Trent Water Limited
- South East Water PLC
- South Staffordshire Water PLC
- South West Water Limited
- Southern Water Limited
- Sutton and East Surrey Water PLC
- Tendring Hundred Water Services Limited
- Thames Water Utilities Limited
- Three Valleys Water PLC
- Wessex Water Services Limited
- Yorkshire Water Services Limited
Inset Appointment- Albion Water Limited
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Published 11 July 2001
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