RIVER POLLUTION

Hauraki Plains Gazette, Volume 58, Issue 4169, 5 August 1949, Page 9

RIVER POLLUTION

PROBLEM IN DISTRICT REVOCATION OF ACT HAURAKI CATCHMENT BOARD Concern at the pollution of rivers known as sludge channels in the Hauraki catchment area was expressed by several members at the July meeting of the Hauraki Catchment Board, and the Soil Conservation and Rivers Control Council is to be urged to adopt a remit, carried at the 1948 conference of the New Zealand Catchment Boards’ Association, urging the abolition of sludge channels. Support for the revocation of the proclamation, under which the Waihou and Ohinemuri rivers and their tributaries were made sludge channels, was given by the Paeroa Chamber of Commerce in a letter to the board, while the support of the various local bodies in the district is to be solicited by the catchment board. ,

“ I am very concerned with this river pollution business, and I think that we should not leave the matter in abeyance any longer,” said Mr H. R. Thorp. “ Even though mining is dying out in this district we cannot leave it at that; we have got to be sure that our rivers are not under the Act.”

“The time is very opportune, now that they are talking about closing the Martha mine,” said Mr E. Clark. “We might not get much opposition now.” “I am not too sure that the .mine is closing down,” interjected Mr O. G. Thornton. The miners showed no signs of leaving the district, he added.

Mr J. Davidson pointed out that mining was not the only cause of water pollution; factories and tanneries could also be troublesome.

History of Rivers

The following report, on the preparation of which the secretary, Mr C. H. Walsh, was congratulated by Mr Thornton, was adopted, and is to be circulated to those local bodies whose support of the board’s action is being solicited:— “The use of watercourses for the disposal of mining debris in the Hauraki catchment district dates back to 1895 when the Waihou and Ohinemuri rivers with their respective tributaries (excluding the Komata and Tarariki streams) were declared sludge channels. This proclamation has been varied by the exclusion of the Puriri stream in 1928 and the Omahu stream in 1929.

“In 1907 the farmers whose land adjoined the Ohinemuri river and part of the Waihou river, became alarmed at the silting of those rivers by tailings and other mining debris being discharged into the rivers and tributaries by mining concerns, particularly as each flood deposited layers of such tailings and other mining debris over productive river flats. On the instigation of these farmers a commission was appointed to investigate the matter. This commission sat during September, 1907, when evidence was taken from farmers and mining representatives. In November 1907 the commission reported to Parliament that it had no recommendations to make on the matter.

“The farmers were far from satisfied at. the result of this commission’s finding so that in 1910 a further commission was appointed to investigate this matter. The commission sat from May to July, 1910, when evidence was taken from farmers arid mining representatives, also from local authorities, on the silting of the rivers. In its report to Parliament the commission recommended, among other things, that the proclamation of 1895 be revoked within six months, and an amended proclamation issued. This proposed amended proclamation was to permit slimes to be discharged into the Ohinemuri river, and into the Waihou and Komata stream (this latter having been excluded from the original proclamation) from existing mines only. No mining debris was to be discharged into the Ohinemuri river at Karangahake except under special permit, and the fine grinding of slimes was to be enforced. The commission recommended the setting up of a river board to be known as the Waihou and Ohinemuri River Board. While the Waihou and Ohinemuri Improvement Act, 1910, made provision for the constitution of such a board, no provision was made to give effect to the other recommendations of the commission. A river board as provided by this Act was never elected.

“ In 1919 and 1921 further commissions investigated the matter of silting of the Waihou and Ohinemuri rivers. The latter commission sitting

from August to September, 1921, expressed regret that'the recommendations of the 1910 commission had not been put into effect. “Considerable river improvements were carried out on the Ohinemuri river near Paeroa and on the Waihou river from a point slightly south of Paeroa to the Hauraki Gulf, by the Ministry of Works. This work comprised mainly the erection of stopbanks. Mining Activities “ Minihg activities in the Hauraki catchment district at the present date are only a fraction of what they were 20 or 30 years ago, when the commissions were investigating the silting problem. At the present time the only mining concern of any importance operating in this district is the Martha Goldmining Company, whose battery is situated at Waikino. The ore is mined at Waihi and transported to Waikino via a tramway. Here the gold is extracted by the cyanide process and the waste matter discharged into the Ohinemuri river. “ In 1907 there were three major mining concerns operating on the Ohinemuri river, and according to evidence submitted to the commission in that year (see page 31, minute 199 of the evidence) the averkge tailings being discharged into the Ohinemuri river between 1895 and 1907 was 391,167 tons per annum- “ With only the Martha Goldmining Company operating today the average amount of debris discharged into the Ohinemuri river is 100,000 tons per annum. Although this figure represents only 25 per cent, of the 1907 figure, nevertheless it is considerable, and silting of the river continues.

“ According to recent Press reports it is probable that the Martha Goldmining Company will cease operations in the near future, and should this eventuate large-scale mining in" this district may be finished. “ However, in August-September, 1948, the Dunsheath Mining Company made application for a license to mine lead ore on Mount Te Aroha and to suitably treat it at a site near Te Aroha. This board opposed the application in the Warden’s Court on the grounds that mining debris may be discharged into the Waihou river, thus causing additional silting, and that removal of vegetation from the claim on Mount Te Aroha may cause soil erosion. The Dunsheath Mining Company agreed to a clause being inserted on their license to the effect that no mining tailings or other debris was to be discharged into the Waihou river, and it is understood that the warden made such recommendation when making his recommendations to the Minister. The board has in mind that, with the application of the Dunsheath Mining Company, there may yet be a considerable revival of mining this district. . Effect of Tailings “ The discharge of mining wastes, such as tailings, slimes, etc., has the following effects on watercourses: (a) silting, (b) pollution. “ The effluent from mining batteries may be composed of many types of debris. Where the ore is being treated by the cyanide process, the debris is composed in the main of crushed quartz, with lesser quantities of cyanide, minerals and water. The crushed quartz is heavy, and unless the level of water in the river is high with a consequently swifter current, the tendency is for this matter to settle on the bed of the river. Although “ freshes ” in the river from time to time will carry away quantities of this substance, it may be carried only a few miles and be again deposited in the bed of the river. Only a percentage of this substance gets out to sea, and the greater amount must lodge on the bed of the river. It is significant to note that the 1910 commission regarded the mining industry as primarily, if not wholly, responsible for the damage that had occurred to the Ohinemuri river.

“ While, to the best of our knowledge, the water from the Waihou and Ohinemuri rivers is not used by any persons for human consumption, in many instances farmers rely on this water for their farm water supplies. The treatment of ore by the cyanide metho’d, particularly, renders the water in the river between the site of the battery and the sea unfit and unsafe for human consumption, and probably dangerous for animal consumption. The depositing of any mining waste in a watercourse must of necessity pollute the w’ater. The depositing of any mining waste in watercourses must also have a considerable effect on the fish life, but the board is not concerned ab this aspect. Further Pollution “ Pollution of watercourses can be caused by other factors besides mining: (a) Farmers can contribute to this problem by discharging waste matters and drainage from cow bjres,

piggeries, etc.; (b) dairy factories can offend by discharging effluent from milk, when manufacturing such commodities as casein; (e) borough councils and householders in rural areas can pollute watercourses by discharging sewage into them, without the sewage material being properly treated. “ The board is not seriously concerned at this problem at present, as it is understood that these types of pollution can be controlled by by-law. By-laws are at present being prepared, and when operative, the board considers it can x adequately deal with this problem.

“ However, legal opinion obtained advised that the board’s bylaws in this respect cannot be effective in dealing with pollution and silting by mining concerns, where the watercourses in question have been declared sludge channels under the Mining Act, 1926. The following may also be contributors to silting of watercourses: (a) drains—this is those dealing with land drainage; (b) soil erosion. Annual cleaning of drains must of a necessity disturb the banks and material off the banks must fall into the drains. “ Freshes ” must carry this material into the river, causing silting. Where soil erosion occurs, the eroding materials generally find their way into a watercourse, with the result that further silting must occur.

However the board is not seriously concerned at this aspect, for it has power under the Soil Conservation and Rivers Control Act, 1941, to deal with such matters, and can take steps to stop or at least to minimise silting caused by these agents. Board Concerned The object of the Soil Conservation and Rivers Control Act, 1941, is to prevent or minimise soil erosion damage by flooding and to promote soil conservation. This work in the Hauraki catchment district has been delegated to the. Hauraki Catchment Board by the Soil Conservation and Rivers Control Council.

Soil erosion in this district is not very evident and our main problem is river control and prevention or minimising of flooding. Prevention or minimising of flooding can be accomplished only by efficient river control, for unless the river channels are kept at adequate dimensions, such channels are unable to cope with the extra water following'heavy rains and flooding of the river flats and the plains must result. Silting of watercourses has the effect of agrading the river beds thus seriously reducing the river’s carrying capacity. In order to deal with this flooding menace the board will haae to devise a scheme of increasing the capacity of the rivers, by: (a) widening and/or deepening the existing channels or (b) erecting stopbanks or where stopbanks are already in existence heightening those banks where necessary; or t (c) creating additional flood channels. At the present time investigations have not reached a sufficiently advanced stage for the board to decide which method will be adopted, but whichever method is adopted will entail a considerable expenditure. In view of this expenditure steps will have to be taken to ensure that the work is adequately maintained and that silting is kept to a minimum by the rigid enforcement of soil conservation practice. Remit Carried * ' The board has taken the following action in an endeavour to solve the problem: At the annual conference of the N.Z. Catchment Boards’ Association held in May, 1948, the following remit, instigated by the board was carried:—

“ That the Soil Conservation and Rivers Control Council be requested to make the necessary arrangements by which any river which was proclaimed to be a sludge channel under the Mining Act, 1926, may, on the application of the catchment board concerned be deleted from such proclamation and any miner or mining company at present holding a license be permitted to use the said river as a sludge channel until such license is revoked or expires.” >

The board feels that the discharging of any mining debris into a watercourse is directly opposed to soil conservation and river control practice, and that the provisions of the Mining Act, 1891, as consolidated by the Mining Act, 1926, relating to sludge channels, are out of date. While the board considers that it is possible or even probable that goldmining in this district, on a major scale, is nearing its end, it is concerned that, with legislation remaining as it is in respect to the use of watercourses as sludge channels, any revival in mining may mean disaster to its schemes for river control.

The board submits that tha terw the above remits should be adoptaA and that the present is an oppartsßa time to carry this out. Tha existing, mining concerns can experianca na hardship by this action, as the proriao in the remit covers this. It will be appreciated that the board must have an assurance that it wiß not be handicapped by mining concents discharging matters into watercowsea before it expands public funds on improvement works on rivers and other watercourses.