1970 Grading of Pubic Water Supplies.Pdf

1970 GRADING OF PUBLIC WATER SUPPLIES IN NEW ZEALAND BOARD OF HEALTH (under Health Act 1956) NA MOH Library - 575 NEW 1970 REPORT SERIES: No. 16 IIIIHflIll I 110185 Published November 1970 STACKJ Uz rrnnt of Hoafth ffintan 1970 GRADING OF PUBLIC WATER SUPPLIES IN NEW ZEALAND 45 WI BOARD OF HEALTH (under Health Act 1956) REPORT SERIES: No. 16 Published November 1970 TABLE OF CONTENTS PAGE Introduction - - - - - - 3 Method of Conducting 1970 Grading - - - - 3 Method of Marking - - - - - - 4 Comment— Grading of Public Water Supplies - - - - 6 Communities With No Public Water Supplies - - - 6 Fluoridation - - - - - - - 7 Conclusions - - - - - - - 7 Table 1-1962 and 1965 Gradings - - - - 9 Table 2-1970 Analysis by Type of Water Supply Authority - 10 Table 3—Analysis by Size of Communities Table 4-1965 Analysis of Types of Water Supply Authority - 12 Table 5-1970 Grading. Population Not on Public Water Supply 13 Table 6-1970 Grading. Public Water Supplies Fluoridated - 18 Table 7-1970 Grading. Grading and Source of Supplies - 21 Table 8-1970 Grading. Supplies Controlled by Government Departments - - - - - 37 Table 9-1970 Grading. Comparison Between Gradings in 1962; 1965-1970 - - - - - - - 45 Appendix A—Explanatory Notes Accompanying Circular Memo- randum 1969/290 - - - - 46 Appendix B—Specimen of Data Collection. Form - - 52 2 1970 GRADING OF PUBLIC WATER SUPPLIES A Report Prepared for the Board of Health by the Department of Health 1. Introduction The first grading of public water supplies was published by the Board of Health in 1962 as Report Series No. 5 entitled Provisional Grading of Public Water Supplies in .J"Iew Zealand. A second grading was undertaken in 1965 but was not published as a formal document. However, the data and associated papers were assembled in 1967 and made available to Government departments and to local authorities. In initiating the survey for the 1961 provisional grading the Board of Health decided that, if possible, surveys should be repeated every 5 years. This report is made in accordance with that decision. The assistance of the Public Health Engineering Section of the Civil Engineering Division of the Ministry of Works in the development of the grading system and the analysis of results is gratefully acknowledged. The purpose of these gradings in each case is to determine the extent to which public water supplies conform to the World Health Organisa- tions "International Standards for Drinking Water" which were adopted as the appropriate criteria by the Board of Health in 1960. The grading is intended to cover the public health aspects of the water supplies only and the award of the highest grading does not necessarily indicate that a supply is wholly satisfactory. There are aspects not considered which may seriously affect a consumers judgment of a supply— such as iron-staining of washing and hosing restrictions. The results of the first and second surveys are summarised in table I, but, because a different technique was used for each grading, the results are not directly comparable (see paragraph 2). 2. Method of Conducting 1970 Grading When the results of the 1961 provisional grading were studied it was found that anomalies in the gradings had developed, apparently because too much reliance had been placed on chemical and bacteriological testing which, in many cases, was so infrequent as to be useless. Sanitary surveys of the catchments supplying the water and examination of the water treatment processes in some cases indicated a much greater danger to health than was evident from the gradings. A different evaluation technique was adopted for the 1965 grading to enable proper emphasis to be given to all factors involved in the assessment of risk to health from all parts of the supply system. Assessment was made both of raw water quality and treatment, and of the distribution system to consumers. The latter assessment recognised the more obvious health risks associated with ball hydrants, uncovered service reservoirs, aged or poorly maintained pipework, and lack of adequate supervision where these factors applied. A truly comparative evaluation technique of all the water undertakings in New Zealand was expected to offer difficulty but the 1965 assessment was considered a much fairer assessment of the true health risks in water supplies. Thus the apparent deterioration in the national situation which seems indicated from an inspection of table 1 is more a result of variation of technique in the two gradings than a measure of relative inadequacy in water undertakings over the period. However, the 1965 grading was criticised by both the Municipal Division of the New Zealand Institution of Engineers and the Association of County Engineers, more particularly because of the apparent unfair emphasis on engineering management which a poor supply grading implied. Discussions were held with the local authority engineering groups which resulted in a revised evaluation form for the 1970 grading. This is basically similar to, but is an improvement upon, that used for the 1965 grading but with the important provision that the individual assessments were to be signed at the time of the survey by both the local authority official and the departmental official. The 1970 grading forms make provision for critical comment by the local authority official, usually the engineer, and in a small number of cases engineers have disagreed with the grading assessment for reasons specific to their own circumstances. The text of the explanatory notes issued to all medical officers of health in December 1969 is annexed in appendix A. A specimen of the data collection form is annexed in appendix B. 3. Method of Marking 3.1 Grading is based on a system of merit and demerit marks for the main features of the supply and distribution systems. 3.2 The supply grading assesses health risks associated with the quality of the water at source and the degree to which these risks are reduced by water treatment processes and other relevant factors. 3.3 For the distribution system demerit marks were given for a number of factors which affect the quality of the water in the distribution system and are consequently a risk to health. 3.4 In each case, marks were divided into categories of acceptability as follows: 4 Grading Marks Supply Distribution Description 2 or less A a Completely satisfactory. 3 to 6 B b Satisfactory. 7 to 10 C c Marginal—may have to be accepted in some small communities. 11 to 15 Ic d Not satisfactory—high degree of risk. 16 and over E e Completely unsatisfactory. For the national analysis the results were grouped into four general categories as follows: Column Heading 1. Least danger to health from water Satisfactory. source and distribution hazards (gradings: Aa, Ab, Ba, Bb) 2. Least danger to health from water Satisfactory source. source but some distribution hazards Unsatisfactory (gradings: Ac, Ad, Ae, Bc, Bd, Be) distribution. 3. Considerable danger to health from Unsatisfactory source. water source but satisfactory distribu- Satisfactory tion system (gradings: Ca, Cb, Da, distribution. Db, Ea, Eb) 4. Considerable danger to health from Unsatisfactory. water source and distribution system (gradings: Cc, Cd, Cc, Dc, Dd, De, Ec, Ed, Ee) Table 2 is an analysis of the 1970 grading showing the supplies in each of the four categories above and the types of water authority. Table 3 is an analysis on the same basis but related to population groupings. Table 4 is an analysis of the second grading (1965) showing water supplies on the same basis as table 3 for purposes of comparison. Table 5 shows that 248 communities with a total of 93,732 people are without a public water supply. Table 6 shows the 52 local authorities which are supplying fluoridated water to a total population of 1,335,596. Table 7 shows the gradings of local authority water supplies and the source. - Table 8 shows the gradings of supplies under the control of Government departments. Table 9 shows the comparison between the gradings undertaken in 1962, 1965, and 1970. 5 Inset 2 Comment Grading of Public Water Supplies The Board of Health is pleased to note the substantial improvement in public water supplies which has been made since the provisional grading in 1962. The standards on which the grading is based are minimal and there are no grounds for complacency in the condition of the countrys water supplies. Adequate treatment of all surface waters should be universal and all supplies should be under the supervision of professional engineers trained in water supply management. Table 9 shows that, since 1965, water supply authorities have provided satisfactory water supplies for more of the population and have made substantial improvements in the quality of water supplied to consumers. The population on public piped water supplies has increased from 75 percent of the total to 83 percent of the total. Eighty-five percent of the population on public water supplies now receive water from satisfactory sources, instead of 73 percent in 1965. Eighty-two percent of the population are now served by distribution systems with satisfactorily low health risks in comparison with 50 percent in 1965. The tables emphasise the difficulty in providing a satisfactory water supply to the smaller communities. Table 3 shows that 92 percent of completely unsatisfactory water supplies are for communities of less than 5,000 people. Of the 24,650 people on unsatisfactory supplies, 46 percent are within communities of less than 5,000 people. Fifty six percent of the unsatisfactory water supplies are for communities of less than 500 people. Table 2 shows that municipalities and Government are each responsible for 25 percent, and county councils responsible for 46 percent, of unsatisfactory supplies. The number of Government water supplies evaluated has increased by 67 because more of the existing supplies have come under surveillance.

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