DARWIN RURAL AREA WATER POLLUTION SURVEY REPORT … · DARWIN RURAL AREA WATER POLLUTION SURVEY REPORT TO DEPARTMENT OF LANDS SEPTEMBER 1981 ... This report concerns the survey of

Technical Report WRD81041

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DARWIN RURAL AREA

WATER POLLUTION SURVEY

REPORT TO DEPARTMENT OF LANDS

SEPTEMBER 1981

Department of Transport and Works Water Division

( i)



4-17-64

Director, Water Division.

Darwin Rural Area - Pollution

Following Cabinet decision No. 1875 of August 17th, 1981 the attached report has been prepared on water pollution in the Darwin Rural Area using information collected since August 26th, 1981 and previously collected data which has been used in earlier reports. This is an interim report on the earliest results of a systematic twelve month programme and foreshadows the production of a final one at this time next year.

N.A. WATSON

Chief Engineer INVESTIGATIONS BR&~CH

(ii)



Synopsis

This report concerns the survey of water pollution in the Darwin Rural Area (planning zone RL 1) and explores the implications of subdivision, land use and the standard of private water supply facilities on the safety of drinking water for rural and city users. It concludes that much could be done by better water resource management practices.

(iii)



DARWIN RURAL AREA - WATER POLLUTION

REPORT TO DEPARTMENT OF LANDS

SEPTEI'IBER 1981

CONTENTS

1. Background

1.1 Hydrogeology study 1.2 Planning Authority 1.3 Augustre-survey 1.4 Twelve month survey programme

2. Water pollution survey to September 1981

2.1 Hethod 2.2 wells and bores 2.3 Size of land holding 2.4 Land use 2.5 Sanitary conditions - septic tanks etc. 2.6 Results

3. Interpretation of survey data to date

3.1 statistical requirements 3.2 Criteria 3.3 Sanitary conditions 3.4 Land use and block sizes 3.5 Season of the year 3.6 Hydrology, supplies at risk 3.7 Threat to McMinn's borefield

4. Existing controls

4.1 Public Health Act 4.2 Control of Waters Act

5. Interim actions

5.1 Strategies considered 5.2 Cabinet decision 5.3 Action taken

6. Conclusions to date

(iv)



LIST OF FIGURES

Figure 3.1.1 Hydrological unit No. 1 Area 'East Howard' 3.1.2 " n " 2 n 'Pioneer' 3.1.3 " n n 3 " 'Wanderrie' 3.1.4 " n " 4 " 'Edwin' 3.1. 5 " " " 5 " 'Horns' 3.1.6 " " " 6 " 'Burdens Creek' 3.1. 7 " n " 7 n 'Brookings' 3.1. 8 " n " 8 " 'Girraween' 3.1.9 " n " 9 " 'Whitewood' 3.1.10 " n " 10 " 'Howard Springs' 3.1.11 Darwin Rural Area zone RL 1

(v)



LIST OF TABLES

Table 2.6.2 Classification of results Area 'Pioneer' (HU2) 2.6.4 " n " " 'Edwin' (HU4) 2.6.5 u " " n 'Horns' (HU5) 2.6.6 " " " " 'Burdens Ck. (HU6) 2.6.7 u " u " 'Brookings' (HU7) 2.6.S u " " " 'Girraween' (HUS) 2.6.9 u " " " 'Whitewood' (HU9) 2.6.10 u " " " 'Howard Springs (HUlO)

(vi)



1. BACKGROUND

1.1 Hydrogeology study The Water Division by virtue of the Water Supplies Development Act, has a responsibility to provide advice and assistance to landholders engaged in agricultural and pastoral pursuits with the provision of water supplies for those pursuits. Since many people have recently taken up land for these purposes in the freehold subdivision 20 to 50 kilometres southeast of Darwin there has been considerable pressure for advice for individual water supplies on these holdings. To meet this demand the Division undertook a project to study the hydrogeology of the area and produce a guideline document to facilitate the provision of this advice. The study would also show the position of the water resource available to the landholders in relation to the Coomalie Dolomite which as a lower aquifer in the eastern part of the region offers water supply potential for economic augmentation of the Darwin city water supply.

The study involved the collection of data from existing bores in the area which was possible with the co-operation of the owners of these bores to supplement data already to hand under the Regulation 8 requirements of the Control of \Vaters Act. In the course of the survey, and as a service to owners, a bacteriological test of water supplies was carried out free for those blockholders who requested it. No testing was done at supplies other than where requested.

The results of the bacteriological testing indicated a high incidence of pollution. Concern was expressed for the health of residents and ultimately the pollution of the McMinn's aquifer and part of Darwin's future water supply. Typical smallholding layouts were examined to arrive at a block size such that little risk would remain of unsanitary conditions on any block seriously polluting the water supply of a neighbour. The Water Division had been objecting to closer subdivision for some time and ultimately put a recommendation to the Planning Authority on May 14th, 1981 that subdivision of blocks below this size (8 hectares) should be restricted unless reticulated water was made available pending a more detailed investigation of the pollution problem.

1.2 Planning Authority The recommendation caused concern since significant areas were already subdivided below the recommended size and more approvals were in progress. Predictably the grounds for the recommendation were thrown into question. The Planning Authority's concern was to have firm evidence of the extent of pollution, its causes and the implications of subdivisions as a basis to make recommendations to the Minister on subdivision proposals over the Whole area. It was then necessary to state that from a statistical point of view, even though the unsanitary conditions of many bore and well sites was quite obvious even to persons without knowledge of bacteriology, the available data could have a bias.



As mentioned above, tests had only been done where requested. The biases coul~be countervailing. As testing was done on supplies for which the owners had grounds for concern it could be biassed to an unfavourable conclusion. On the other hand since concerned owners could be expected to follow better practices it could be biassed in a favourable direction. Without a better statistical approach to the survey of water quality the implications would not go unquestioned. The Water Division therefore reported on the statistical significance of the data considered at that stage and what the requirements were for a completely satisfactory survey, what it would cost, and the minimum length of time over which it must be done.

1.3 August re-survey In view of the urgency which the N.T. Government felt the matter held, and t2e fact that the samples tested had been taken mainly under wet season conditions, re-testing of the supplies in the original data set was undertaken. For various reasons access was not gained to all the bores~in question but out of the 23 supplies 14 were re-tested during August 1981. It was found that, on a percentage basis, the proportion of supplies not meeting current health criteria was not much less than previously in one~. given month than it was in the samples taken over different times. Results are given in Table 1.3. In addition to the bacteriological sampling sanitary conditions pertaining to the water supply and land use practices were noted.

1.4 Twelve month survey ~rogramme As a result of the conflrmed presence of pollution in the re-survey and consistent with the original recommendation and Cabinet's directions, comr[lencement of a 12 month broad based survey was ordered. This was to take into consideration the following factors:

size of landholding type of supply, bore or well sanitary conditions land use, animals, fertilizers regional hydrology

2. WATER POLLUTION SURVEY TO SEPTEMBER 1981

2.1 Method The results should be capable of interpretation in relation to certain land areas. The Planning Authority's zone RL 1, Darwin Rural Area was taken as the survey boundary and it was divided into ten 'hydrological units' in such a way that each unit had some hydrological integrity. These units approximate to interfluvial zones, that is the boundaries more or less follow creeks. As a general rule pollution of phreatic water (upper aquifers are usually phreatic) would not pass between zones defined in this way. Within each hydrological unit sufficient locations are being sampled



to allow for the randomness of .the occurence of bacteria in a sample taken from an individual supply; the randomness of theoccurence of pollution throughout the hydrological unit and the randomness of the use of good sanitary practice amongst the landholders of the district. A minimum of nine locations was set per unit and the number of sampling locations allocated to each unit would loosely correlate to the subdivision/population density in each unit hence the potential for pollution in that unit.

Since the survey is to show variation over time by monthly re-sampling an adequate number of locations is needed to allow for failure to repeat tests at some sites for various reasons such as pump failures, landholders circumstances, accidents with samples, etc. 50% extra locations are taken as the initial target for these reasons.

Within each hydrological unit the subsurface geology, the potenticnmetric contours for January 1981 and the hydrogeologists interpretation of groundwater flow direction and major recharge areas have been compiled on a scale of 1:25 000. Combined with an overlay plan of the subdivisions and bore registration numbers this enables a check to be made that the coverage provides.· for s.ignificant changes in subsurface geology. For example hydrological unit eight (HU 8) is bounded by the Howard River, the Howard River West Branch, secticns 296 and 297 Stuart Highway and Pioneer Road. Beneath the western third of that area is the Masson Formation and beneath the eastern two thirds is the Coomalie Dolomite. Sufficient locations are being selected to reflect the different effects cf this geology.

Arrangements to take samples from private bores have been made by telephoned requests in the first instance. Coverage by this means being insufficient, access to further bores is being arranged by visits to properties close to points selected by a random scatter carried out on the map. Until now the co-operation of owners has beeL excellent and most have shown interest in improving the quality of their water supplies. Field officers provide assistance with water supply problems if they are in a position to do so when requested and test results are being supplied to owners free of charge in respect of their own supplies. Gratuitous written advice is not, however, being attached to these complimentary copies of results.

Before sampling supplies, the bore or well pumps are run for ten minutes to purge stagnant water. The tap from Which the samples are drawn is then flame sterilized, purged again and then sampled into autoclaved sterile bottles. These bottles are transported on ice to the Water Division bacteriology laboratory on Hudson Fysh Avenue where they are processed by membrane filter technique in accordance with APHA Standard Methods (13th Edition). The filtration and culturing commences within 8 hours of sampling.



2.2 Wells and bores Although the hydrology of water extraction, and the elements of good bore or well construction practice are the same in principle, the survey is distinquishing between bores and wells. In this context wells are being taken as anything from a two metre square hand dug hole in the ground to a one metre diameter augered shaft lined with concrete. Wells with a rough casing formed from "44 gallon" drums tack welded together ar.e not uncommon. The basis of the distinction is that wells are generally more susceptible than bores to things falling down them and even the most poorly constructed drilled bore usually has at least a casing of some sort. In general it is considered wells are more susceptible to contamination via surface inflow than bores.

2.3 Size of land holding Whereas eight hectares was recommended as a safe size for separation of private water supplies the survey is categorising blocks greater or less than five. The reason for this is that the larger figure would have given insufficient data for the larger block size.

2.4 Land use The field officer is recording where possible the kind and number of animal stock on the properties surveyed. Th.is is intended to provide an overall picture of preferred pursuits of smallholders as an aid to improving the general advice given to the rural population on water supply management. No commercial piggeries are within the zone of the survey. In the case of small pig keeping practices owners are advised by field officers of the pigs ability to host pathogens harmful to humans. Information as to the use of herbicides, pesticides, chemicals or other toxic substance on the properties is also being requested.

2.5 Sanitary conditions - septic tanks etc. At the time of sampling the field officer is noting whether sanitary conditions at the bore or well head are satisfactory as far as it is possible to tell. Although it is not possible im many cases to be completely sure the well casing is impermeable to 3-5 metres below the surface, the adequacy of the coping, covering and fencing can be noted. The requirements of Regulation 58 (Night soil, garbage, cesspits, wells and water) of the Public Health Act are a guide to the requirements. Beyond that it is also worth noting that the trimming around the bore ensures surface water drains away from it. The distance of septic tanks and their soakaways from the bore or well, it noted;

2.6 Results Tables 2.6.2 and 2.6.4 to 2.6.10 present a classification of results obtained. These tables comprise results for the locations tested in the systematic programme only and are being compiled for dry season conditions which are being defined as June to October for the purpose of this survey.



A separate set of tables will be prepared for wet season conditions November to May inclusive. other observations made on the first visit to the participating properties are not presented with the report to maintain confidentiality but are being used to indicate trends in the area as a whole. This data is available in Water Division if required.

3. INTERPRETATION OF SURVEY

3.1 Statistical requirements Figure 3.1.11 shows the break up of planning zone RL 1 into ten hydrological units. The sampling achievement so far of number of bores and wells in each unit participating in the survey are as follows:

unit Bores Wells Springs

1 0 0

2 7 2 3 0 0

4 7 0 5 6 1

6 3 0 7 4 2 8 12 4 9 8 1

10 8 0 1

None of the areas is yet adequately covered but work is continuing with the objective of achieving an adequate number before the end of september. This is not expected to be possible in hydrological units numbers one and three since very little settlement and drilling has taken place in these units which lie east--of Howard River.

In the categorising it seems unlikely that adequate statistics on wells will be obtained unit by unit but may be enough to base a conclusion regarding wells over the whole survey.

3.2 criteria The criteria in use to decide whether supplies meet long term (i.e. appropriate for planning purposes) objectives have been adopted recently by the Department of Health and the Department of Transport and Works. They are the guidelines developed jointly by the Australian Water Resources Council and the National Health and Medical Research Council and published in 1980 as 'Desirable Quality for Drinking Water in Australia'.



The criteria (hereinafter referred to as NTLTO/80) are:

1. T"nroughoutany year, 95% of samples should ;wt contain any coliform organisms in 100 ~ili.

2. No sampZe shouZd contain more than 10 coliform orga:aisms per 100 mL.

3. Coliform organisms shouZd not be detectabZe in 100 mL of a:ay two consecutive samptes.

4. No sampZe should contain E. CoZi. in 100 mE.

Results of the current survey already to hand have failed to satisfy these criteria in fourteen cases out of twenty eight results available. A comparison of findings on the basis of NTLTO/80 criteria shows:

available data 1976-1980 78% fail criteria

re-survey of August 1981 44% " " current systematic survey from August 26th 1981 to date 50% " "

Previous to the adoption of the present criteria those of the World Health Organisation had been in use. Therefore the 1976 to 1980 data has been quoted as having a different failure rate in earlier reports but henceforth NTLTO/80 will be used for comparisons.

3.3 Sanitary Condit~ons Of the bores inspected very few had fencing at a suitable distance from the bore to keep livestock away although in one case having a shed over the bore served the same purpose. Only four bores were 200 metres or more distant from the nearest septic tank as reco~~ended by Reference (I). References (2) and (3) tend to shorter distances which lead us to recommend a minimum distance of 20 metres. Apart from those aspects twenty eight out of sixty bores (47%) inspected so far had generally satisfactory sanitary conditions. The most frequent inadequacy so far is the height of coping to the bore or well for which a height of 450 mi11imetres is desirable to be above the height at which dogs habitually pass water. The standard of casing appeared to be good in 90% of bores although it has not been possible to determine the depth of the casing. At 15% of locations the drainage of surface water away from the bore or well head has been unsatisfactory. 74% of supplies which had generally satisfactory sanitary conditions yielded water which met the NTLTO/80 criteria.

3.4 Land use and block size For the bacteriological results so far to hand twenty two out of twenty eight (78%) are for blocks less than five hectares in size. The ratio for the whole survey is not yet available.



The keeping of animals figures prominently in the land use pattern. The. percentage of blocks providing information on livestock resulted in the following pattern of livestock:

Poultry 43% of blocks pigs 8% n " Horses & Donkeys 21% n n

Cow & Buffaloes 8% n n

sundry 5% n n

Sundry animals include goats, rabbits and commercial dog kennels but does not include normal pet dogs.

Agricultural pursuits as indicated by fertilizer usage, are practiced on 47% of blocks of which 18% use manure to some extent and 36% use chemical fertilizers. Pesticides and herbicides figure in 28% of the land use returns.

3.5 Season of the year It is not possible to make any interpretation of results in this regard as yet. The occuxrenceof two heavy falls of rain in August could have rendered conditions untypical for the time of year.

3.6 Hydrology, supplies at risk Figure 3.1.8 shows hydrological unit B which we may refer to as Girraween. It is bounded on the north by the west branch of the Howard River and Sections 296 and 297 on the west side by the Stuart Highway, the south side by Pioneer Road and the east side by the Howard River proper. The eastern two thirds is underlain by the Coomalie Dolomite and the western third by the Masson formation. Recharge is general over the area. For an area outlined by dotted line in the south, according to the bicarbonate to chlorine ratios found in the waters the recharge rate may not be as rapid as elsewhere. This has not been confirmed by any .. !!!lQJ::e strict technique such as use of tracers. The movement of the groundwater in the area is towards the,northeast although local variations may be expected in the case of the upper (phreatic) aquifer. Therefore as a general, not infallible, rule water supplies may be at risk from pollution occurring to the southwest only as far as the Stuart Highway which happens. to coincide with a hydrological divide.

It is usual to anticipate rapid movement of groundwater to occur in karstic rock types such as the Coomalie Dolomite, that is a soluble rock with solution channels formed in it. Groundwater movement in soils such as clays, silts and loams on the other hand is normally so slow that bacteria do not survive for more than a fe'7 metres of travel. However, it has been noted that the process of lateritisation is capbale of forming passages in the soils and such soils are known to exist in the study area.



The phenomenon known as 'crabholes' has been frequently encountered in lateritised subsoils in the Darwin area, lateritic soils exposed to alternate wetting and drying and accessible to oxygen are subject to this down to as much as 4 metres and result in easy and rapid passage of water at individual spots. So despite the overall average movement of groundwater through the soil being slow, the occurrence of an individual rapid flow path occurring for a pollutant should not be totally discounted. The complete impermeability of the casing to 3.7 metres depth should normally obviate problems from this cause and a minimum distance of 20 metres between bores and any septic tank, soakaway, garbage t-ip, manure heap or other pollutant source should be maintained.

Figures 3.1.1 to 3.1.7, 3.1.9 and 3.1.10 similarly show the other nine hydrological units comprising zone RL 1 and in most cases the general direction of groundwater movement is known. As for Girraween, the general movement of groundwater does not rule out local variations in movement in the upper (phreatic) aquifer. The standing water level in bores which defined the potentiometric contours shown in the figures was in many cases that of the lower aquifer.

3.7 McMinn's borefield There is no evidence at this stage of pollution in the deeper aquifers being tapped to supplement Darwin water supply. This main aquifer is a basal gravel conglomerate overlapping cavernous dolomites and, with fissures and solution channels in the overlapping clayey gravels and laterites. The threat of contamination entering the main aquifer and travelling rapidly through it to a production bore location is very real. Bacteriological contamination in the Darwin supply from several sources is highly unlikely due to the fairly rapid death of coliform bacteria and the protection afforded by chlorination, however the longer term threat to the MCMinn's supply through persistent bacterial strains and toxic chemicals associated with human habitation is of some concern.

Water Division has engaged Coffey and Partners to investigate the further development and management of the McMinn's groundwater supply. Their final draft report was received on 8.9.81 and indicates that augmentation of the borefield will be concentrated west of Benham's Lagoon and east of the Howard River. The interaction therefore between private supplies in the currently defined rural area and future groundwater supplies for Darwin will be diminished.

4. EXISTING CONTROLS

4.1 Public Health Act Regulation 58 under this Act gives the Chief Medical Officer (C.M.O.) powers with respect to night soil, garbage, cesspits, wells and water.



",,,ell n is defined as including "any underground water storage, tank or reservoir", and it is interpreted that this would also include a bore, however, steps are being taken to alter the Act to cover bores explicitly.

The Regulation requires a person who wishes to construct or alter a well to make application, beforehand, to the C.M.O. He is required to ensure that the well is:

(aJ surrounded with at Zeast a 450mm (18 inches) coping of impePmeable material

(b) lined with imvePmeable lining to a level of not less than 3.5i'!l (12" feet) below the sV2'face

(c) SU1'Pounded by cm impePmeable covering p1'ovided with a moveable tZ'crp door not more than 2.514 (8 jeet) in ci1'cumjerence

and

(d) constructed to the satisfaction of an Inspector 01' is su-"'1'ounded with a fence at least 4. 5H (15 feet) f1'om the Qutep edge of the welZ and co:pahZe of resisting the trespass of all livestock and poultry.

A pe1'son shall not construct a well 01' v.se the wate1' from a new well without fi1'st obtaining from an bwpector his app1'oval in writing.

The C.M.O. can, if he is satisfied that danger to health exists, or is likely to exist owing to the use of water from a well prohibit the use of water from the well, order it closed, and/or order such work to be done to the well or its surrounds as deemed necessary. Penalty for offences under the appropriate section of Regulation 58 is $100 (50 pounds) .

The C.M.O. under this legislation has wide powers to enforce controls on the construction of wells and use of water from them. The Department of Health agrees that the Regulation could also be applied to bores but the Department never has (nor is it currently in a position to do so) enforced the Regulation. Regulation 58 also requires the C.M.O. to exercise controls on septic tank installation. This function is carried out and inspectors do take account of the siting of septic tanks with respect to the water supply source.

4.2 Water- Control District The Minister under Section lOA of the Control of Waters Act can prohibit discharge of specified substances in order to protect the water contained in a water course, lake or aquifer. The application of this power is more appropriate to point rather than nonpoint pollution sources.

Under section 16A of-the Act the Minister may constitute a Water Control District (W.C.D.), as a means of protection of the water resources. within this District he may then prohibit specific Acts including,



16 B (1) (i) "sinking, constructing 01' ·using a well or water oore"

(jJ "causing OP suffering a TiJell or water bore to be sunk;) aonst"P1.-lci;ed 011 used"

He may not however prohibit,

16 B (1B) (a) "the sinkir>.g of a well or uJater bore for domestic purposes"

or

Cb) "ihe use of water f~om a welZ or wai:er bore upon lemd less than 2 lia (5 acres) in extent if the we ZZ or ,,)ater oore is equipped w"ith machinery which is not capabZe of pumping more tha:tl 0.63 Z-/sec (5/)0 ga7.."lons/ho1fl')."

Whilst the constitution of a Water Control District does not inhibit the riparian right of the landholder to have access to water for domestic purposes the Controller of Water Resources under Section 16E(e) can require the landholder within a W.C.D. lito refrain from causing 01" permitting the S01fl'ce of supply of a well 01' water bore to be contamip.ated or become likely to be contamip.ated by cay waste water~ cesspit~ or other source of contaraination beZonging to 01'1 W7.der the conr.flo-Z of the owner or oaaupiep. n

The Water Division intends to proceed with developing a proposal for the Minister to declare a W.C.D. The boundary of this District will be identified when the consultants recommendations regarding future development of the McMinn's/ Benham borefield are to hand.

5. INTERIM ACTIONS

5.1 Strategies considered

The following strategies were considered by the N.T. Planning Authority:

5.1.1 ALLOW UNRESTRICTED DEVELOPMENT BUT WARN OF THE HEALTH

RISK AND RECO~~END INDIVIDUAL WATER TREATMENT AND/OR

RAINWATER STORAGE TANKS

The result of this approach would be rapid escalation of the pollution problem and an increased probability of it being a vector in an epidemic. This approach clearly sheds the responsibility from Government to the individual and whilst the majority of people may accept the risk and take the necessary steps to ensure their own protection some people may either not understand or may not care sufficiently to bother.

5.1. 2 ALLOW DEVELOPMENT DOWN TO 2 Ha BUT WARN OF HEALTH

RISKS AND IMPOSE CONDITIONS ON BORE AND WELL CONSTRUCTION



If future bores and wells are constructed to acceptable standards and existing installations are brought up to standard it is probable that the incidence of contamination particularly during the wet season will be reduced. There is however suspicion that pollution exists which may not be avoided through improved construction standards and thus any increase in population density (brought about by closer subdivision) will amplify the problem.

There are a few options available to enforce satisfactory construction standards of water supply installations.

5.1. 3

Department of Health has existing powers under Regulation 58 although it is understood that additional manpower resources would be required by them.

Subdivisional approvals could be conditional on water facility construction standards being maintained although an inspection agency would still be necessary within Government.

The Controller of Water Resources could, by notice under Section 16E(e) require action to be taken to prevent pollution.

ALLOW DEVELOPMENT TO 2 Ha ONLY WHERE RETICULATED

WATER IS MADE AVAILABLE BY THE SUBDIVIDER AND

ELSE~~ERE TO 8 Ha MINIMUM

This would be an interim policy dependent on the comprehensive survey, and the outcome of that survey. Reticulation has been installed successfully by one subdivider in the area.

Imere trunk mains are installed the subdivider ,.ould be responsible for the distribution system at an estimated cost of abou~ $5000 per 2 Ha allotment. The Government should not proceed with major headworks extension pending the result of the pollution survey and assessment of the need for an overall commitment to water reticulation.

A further strategy not previously considered is:

5.1.4 ENCOURAGE THE FORMATION OF CO-OPERATIVES TO MAKE

A PARTICIPATORY ARRANGE~rnNT WITH THE GOVERNMENT

FOR THE CONSTRUCTION OF A SAFE SUPPLY TO AN AREA

An approach of this type is used in rural areas of South Australia where supplies are poor.



Although the contribution of participants would be more than urban residents would expect to pay for a water connection it-may be considerably less than their individual costs of obtaining a high quality supply. This would require a petition by a specified quorum of blockholders in an area to initiate a water supply project.

5.1.5, An approach was made to Cabinet on August 13th, 1981 with a recommendation to implement strategy 5.1.3 above as Cabinet submission No. 1594.

5.2 Cabinet decision Cabinet decision No. 1875 of August 17th, 1981 was that:

5.2.1

5.2.2

5.2.3

5.2.4

5.2.5

the Control of Waters Act be amended to provide that a Water Control District, where so prescribed by the Minister, apply to domestic bores;

the Controller of Water Resources embark on a 12 month survey of domestic bores in the Darwin rural area;

the Planning Area 3 Authority embark on an enquiry into the extent of pollution in that area and report to the Minister for Lands and Housing within one month, with a final report in 12 months;

pending receipt of the final report all future subdivision of less than 8 Ha in Planning Area 3 be subject to the proviso that water be retioulated to them; and

the Health Act be amended where necessary to enable enforcement of good housekeeping of groundwater supplies and septic tanks in the Darwin rural area.

5.3 Action taken Drafting of the amendment to the Control of Waters Act has been put in hand.

The twelve month survey of domestic bore in the Darwin rural area (RL 1) has commenced and about half the number of locations required in eight out of tea sub-areas have been tested as part of the September round. Of sixty five locations surveyed analysis results are ready for twenty eight and have been used in the preparation of this interim report.

This report has been prepared in response to the decision 5.2.3 above and will be updated to form a final report to the Department of Lands in twelve months.



Provision of decision 5.2.4 has been adopted.

Drafting of amendment to the Health Act has been put in hand.

6. CONCLUSIONS TO DATE

Nothing in the data so far collected in the systematic survey gives any grounds for the hope that earlier water pollution data was misleading. It appears that faecal pollution of domestic bores in the rural area is frequent and random throughout the area.

Bores which, in most regards, met the sanitary standards of Health Regulation 58 had a higher percentage occurrence of- satisfactory water quality.

Fencing of bores was the sanitary requirement most frequently neglected. The keeping of animals is so common in the rural area that the fencing of bores is seen as the most-important single factor for the area as a whole.

From the point of view of epidemic potential, pollution of groundwater from activities in the area surrounding the western end of Girraween Road are seen as the most critical.

The area between WanderrieRoad, the east branch of the Howard River and Benham's Lagoon is potential pollution source for Darwin's future water supply and development in that area should be managed accordingly.

The residents of the Darwin Rural Area are aware and concerned about water pollution. They are generally receptive to information and advice on water pollution matters and willing to carry out remedial measures if they are within their resources.

8.9.81



REFERENCES

1. PARKER, H. W. ftaste-water Systems E:%Jineering, Prentice Hall (1975)

2. WORLD HEALTH ORGANISATION EXOJ'eta Disposal for Fhrr-al Areas «ad SmaZl !}ommwdties, W.H.O. Geneva (1958)

3. WORLD HEALTH, ORGANISATION r-late1' SuppZy for Rural Areas and Small Communities, W.H.O. Geneva (1959)

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BORB OR

WELL

BORE:

bORE

BORB

WELL

WJi'LL

BORE

WELL

BORE

BORE

WELL

BORE

BORB

W£tJ,

WELL

II PREVIOUSLY SAMPLED

. 8 Sect. 364 BORB .I.~, .

" ~O " ·175 BORE!

DARWIN RURAL AREA WATER POLLUTION

._.RESUL'l'S Of.,RESURVEY AUGUST 1981

CON'fll.MINA'fION CHJillGE

PREVIOUST,Y CURRENT

NO YES DETERIORATED

YES YES SAME

YES NO IMPROVED •

.YES NO IMPROVED

NO YES DETERIORATED

NO NO IMPROVED

YES NO IMPROVED

NO NO SAME

NO YES DETERIORATED

YES NO IMPROV1W

NO NO DIPROVED

NO YES DETERIORATED

YES NO II1PROVED

YES NO IHPROVED

•

NO

. f i NO'

TABLE 1.3

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D81041

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age 24 of 28.

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age 25 of 28.

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Technical R

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D81041

View

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age 26 of 28.

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DRY -----.--- ~

BOHE I~ELL

--------------------; Lf.:SS THAN 5 Ha GHEA'!'EH THAN 5 Ha LESS THAN 5 Ha GREATEH THAN 5 II

. i)Ul<CE MEETS HEGULA'l'ION 58 YES NO YES NO YES NO YES NO

· ..• Tlm QUALITY

'.u(~l\rrlON

MI,ETS ODJEC'l'IVES YES NO YES NO

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