RIVERS COMMISSION.

Hauraki Plains Gazette, Volume XXXII, Issue 4307, 22 August 1921, Page 1

RIVERS COMMISSION.

Continuation of evidence. COMBINED EXPERIENCE. Robert Basil Dunlop, farmer; Nethei'ton, said he had had battery experience at Thames. He had been at Netherton since, 1911, when there was a fair deposit of tailings on the land. He had had charge of the old Rangiora ferry. This had been abandoned by the Ohinemuri County Council owing to the river silting up and making it unusable by the formation of a beach of 15 feet; the depth was lower ; in 19.10 bottom could not be touched with a long oar. Now one could wajk across. He had taken sand put of the channel of the river for ■ making concrete ; this sand was rough, intermixed with mining tailings. The deeper the bucket went the finer and more solid was the material. The banks of the river were composed of tailings. The bed of the river was coming up, the channel narrowing, and the river was not of the same carrying capacity as it was in 1910. The drains, owing to the mining deposits, had to be. cleaned ou,t annually, otherwise the tailings filled the drains up altogether. The same, effect took place in all the river drains from Netherton to Ngahina. The deposit m .the public drain, Laughlin’s outfal.k had been cleared out by him for three years. A floodgate had to be put on eventually to keep out the tailings. The land had had 'silt deposited oil it even as late as 1918. The silt spoiled the grass, the milk went down in quantity aha quality, and the standard, was not recovered during the season.

lb Mr Clendon : The area of his place, was 154 acres. He would take about £6O per acre for it. To Mr Richmond : He was president of the Netherton branch of the N.Z. Farmers’ Union. Mr Richmond : It is an article of faith with you, then, to insist that silt is thrown up on the land, etc ? It is an article of fact. Witness said h,e had bought his land for £2O per acre. He was not in any way connected with the agitation in respect to improvements. The bottom of the drains, for five chains or so back, contained mining silt. He denied that it was mostly ordinary Waihou River debris.

To Mr Porritt: Shingly matter was found where the current was, but,to either side the finer stuff, mining silt, grew progressively deeper out to the banks. •To Commissioner Buchanan : Water flooded a portion of hjs.pxoperty, to a depth of two feet of v.ater. The Ohinemuri deposited slimes, boot-top deep, but the Waihou water was .clear, except for a slight slime. Slimes were deposited up Laughlin’s ou - fall drain miles back.' Whenever there was a heavy fresh in the river now the land got flood water, but it did not do so five or six years ago. The evidence of .James Howie, farmer, Komata North, and Thomas J. V. Dunlop, same, was taken as corroborating that of R. B. Dunlop, without these witnesses being called, DEPTH OF TAILINGS, 45 FEET. William Turner, dredgemaster, now employed by the Public Works Department, said he* 1 had known the river for forty years. He knew it prior to the use of the Ohinemuri as a sludge channel. Great changes had taken place since 1895, it having got. deeper in some places and shallower in others. Boats used to come up to the Railway Wharf; the Ohinemuri was clearer .than the Waihou before tailings were put in, and grass and willows were growing to the water’s edge. The largest portion of. the tailings were taken put by the Extraction Co. Opposite the Criterion Hotel) the dredge had gone down 45 feet, and ,then’did not get to the bottom ofi the tailings another place 25 feet deep had been plumbed with the same result. , OF LEATHERY CONSISTENCY. The material latterly became so fine and slimy that it could not b.e kept in the barges, but .would escape with ,the .water. Some parts of the river had silted up again. There was difficulty at times in getting the d.r,edg.e to sink, as the lift would not go through nine inches or so of silt in places, which set in a kind of leathery mass where there was still water. In loose sand he had- got 14 seven-ton barges full in one hole without shifting. When the air-lift dredge was displaced by the Priestman, the serrated jaws of the latter would penetrate the slimes. The latter settled in all the still places in the river, and was noticeable on the surface covered and uncovered alternately by the rise and'fall of the tjde. A dredge was built at the old junction in 1915. but-the bank had built up to such an extent by debris that by the time the building of the dredge was completed ways had to be laid out across the sand to get the dredge into the stream; previously it could have been floated where built. The tide ran in for two hours and ran out during ten ; the. inward pace cut the channel out. When the tide was going out at Opani point it was just coming in al Paeroa, There was virtually no "slack water. ’ The tide dropped two inches before the upward run stopped, and then immediately started on the ebb run. One of the two dredges was always working on new slimes for six months out of 12. The old coarse tailings never shifted once they lodged on .the bottom. The 1918 flood was within a foot of the 1910 one 1 . Between the Criterion and railway bridges there

was five feet at least of water, but not so now. From the Junction to the top of Thorp’s orchard the .river had shoaled up a lot. 'He could not get to the old junction with a launch at low water. An Auckland-Thames boat used to go up to Cox’s before the Criterion bridge was built. The ‘‘Spitfire’ used to draw seyen feet, and got to the old junction. ”he river channel had silted up .considerably, and this process was still going on. Slimes were settling in tne Waihou in all si,ack water. To Mr Montague : Mining silt had built up the Waimarie bend. To Mr Hanna: The new slimes caused shoaling.

To Mr Richmond : The Lpwer Waihou was of the same depth of channel now as in the old days, i.e.,, where the current was. Back from that the “leathery- stuff” piled up ; at V' harepqa in a locality where a man would sink over his bead in mud in the old days Was now firm* and the c.attle could walk put to deep water on the .“leathery stuff./ To Mr Porritt: Witness - knew the river as well as anyone. Robert Mark Aitken, mining engineer, Auckland, also metallurgist, and was for 8% years director of School of Mining on the West Coast of the South Island, and manager of the Waihi-Paer.oa Gold Extraction Co., was the next witness.

Answering Mr Porritt, witfiess said he was in charge of .the Extraction Co.’s first work, at Waihi, where 100 tons of tailings were ground per day, in four tube-mills. The.Po'hley aiilift was im use then. Potholes were formed by this process, and in 1910 the flood water washed into these potholes and lifted the sand, car lying it right, down to Mackaytown and leaving the upper reaches of the river free of tailings. :

At this time the erection of the plant at Paerpa had been commenced, and the company then concentrated its efforts at Paeroa.

But it*was the .companys’ operations tha,t loosened the tailings at Waihi, otherwise the 1910 '.flood might not have shifted them.

Experience had taught him that the evidence given in 1910 was wrong at some points, but in the main was correct.

The air-lift dredge at Paeroa was of superior construction, and .the company at that time thought it would be able to deal with all the tailings in the river. Mr Blow The river sand was not auriferous ?—No. Mr Aitken said the company’s claim extended from the Junction to Mackaytown. The estimate of material was 2,200,000 tons on the bed, of which 1,700,000 tons- was under ’.he water, the other 500,000 being under and on the banks. ■

There was not the slightest 'doub

in the world that the flocculent material from the batteries would travel down on a less fall tiffin the fine sands required. Mr Grace estimated two per cent, fall for flocculent slimes, the Extraction Co. four percent.

GROUND “EXCEEDINGLY SMALL.” The slow grinding by the Extraction Co. ground finer than the mining companies did. The companies used their tube-mills for fine grinding, and the Extraction Co.' used theirs as sliming mills. z

DEMONSTRATION SUPPORTED. A very large percentage of the “natural” slime went out to sea. He quite agreed with Mr Couper’s test in respect to flocculency and in all other respects. Any man having api actical knowledge of milling must ta)te a similar view. The Extraction.y-'O-used five or six pounds of lime per ton' of ore to re-introduce the flocculent state. If too little lime was used the slimes would stick to the laundeis and sluicing had then to be resorted to.

During the dry season the Ohine-

muri was a settling pond for months at a time ; he had heard it said that there was a current of one foot per second, but he did not believe it. The air-lift dredge required eight feet depth to work satisfactorily. The Priestman removed obstructions. The greatest depth worked «jvas 45 feet. If the material from the mines had not lost its flocculency it would not have been deposited into the Ohinemuri River. The values got by the Extraction Co.* were mostly silver--11 of silver to 1 of gold. He agieed with Mr Couper that avpercentage of the slimes lost their' floOculency and were deposited on the bed of the Ohinemuri. A MACKAYTOWN FARMER. ' William-. George Marsh, farmer, Mackaytown, described to Mr Poiritt how he had. put in considerable time on his farm removing silt with a 'scoop, after the 1910 flood. Silt had been deposited lightly at various times since. she land heeded heavy manuring.' His paddocks had never recovered from the 1910 inundation. Ploughing the silt in was no benefit to the land ; it was simply a means of getting rid of the silt by turning the sub-soil up oh top.. Prior to siltation the islands at Mackaytown were covered in good rough feed. The channel had got filled with silt, wfiicn went on'increasing at every flood. The Government valuation on the 58 acres was £l6OO.

To Mr Clendon : The silt caused the land to dry up during summer. To Mr Hanna: There was any amount of tailings in the river up above. There were less tailings in the river above his land than in 1910. £BO would not pay for the damage done, not by a long way.

Mr Richmond : There is very failfeed on your farm ?

The commission did not visit the place mentioned to them. Did you scoop half of the silt off your place ? —Yes, more.

Over 31 acres the silt varied from 6 inches to 10 feet ?

The 10 feet was on the "low-lying land, and not on the paddocks. Th:s land was totally destroyed, and was about two.acres in extent. -

Mr Richmond made some calculation’s from which he deduced that, m 'the witness’ own figures, only 2% inches had been taken off 2% acres ; it was only a "spoonful,” and was the usual kind of thing met with in compensation cases.

Witness said his experience was that on the edge of the water the silt was loose. The hard;' leathery mass spoken about obtained under water, but a current running into it would shift it. i

To Mr Johnstone: An application for compensation, based on land valued at £5O per acre, was too high. There were 24 head of cattle and four horses on the 58 acres. Wairere had been ruined by silt. Mr Richmond : Do you know that your late father actually opposed the removal of sand from the land ? —I do not remember.

To Mr Porritt■: Otara„ and Wairere were worked as one farm, and both included in the area claimed as being totally destroyed. The river and Rewarewa farm separated Otara and Wairere. The total area was 95 acres. Mr Porritt: The 1910 Commission recommended the purchase of Wairere outright. There was too muci tailings on it.to be cleared off.

The 1907 flood, and previous ones, flooded the land, witness said.

Commissioner Blow (chairman) : Mr Hazard calculated that.in the 1910 flood. 42,500 tons of water passed through Karangahake gorge every minute. It is difficult to understand how 2% feet of solids were deposited from four feet of water. ’ MR RESUMES. At this stage the exam'nation in chief of Mr R. M. Aitken was resumed. If i;t were not for the action of the rapids the slimes would take longer to lose their flocculency. This flocculency was restored at the Extraction Works by the addition of lime. The ‘large deposit of tailings Used by the company had been entire-, ly deflocculated. / DISCONCERTING FIGURES.. Mr E. F. Adams had estimated that it would -take 608,000 tons of slimes to cover the tidal portion of the river bed, at high water, to a depth of one inch. Over an area of 12,78'5,000 yards of river bed from Mackaytown, the deposit of 2?2,000 tons of tailings would cover only to a depth of 9% inches. This estimate, ‘given before the 1910 Commission by Mr-Adams, bore out the Extraction Co.’s estimate.

Mr Richmond objected 'tc witness putting in the statement as evidence. Mr Johnstone also objected that the report was a wholesale criticism, and as such was to be discounted. Mr Porritt submitted that the witness was entitled the figure, as they supported his estimates of what tailings his company would have to handle.

The Commission supported Mr Porritt’s contention.

Witness continued that the company had started on a very low«grade proposition, and the rise in wages and cost of materials forced i. to cease.

At first the slimes and tailings rejected from the works were deposited just off the works, but the incoming current was so strong 'that .these materials were washed back up-stream to the dredge. A new* fluming, was then put in, and the slimes taken a mile further down. These slimes were the finest produced, and would carry down into the Lower Waihou, whether in a flocculent state or not. The flow of the tide ran at about two miles an hour ; it seemingly remained stationary for a half-hour or an hour, and for the balance of the ten hours it slowly flowed out. He could never understand the engineering statements that the river had a velocity of a foot per second when ebbing.. He would not think it more than six inches per second at the most, from his observation. Below Pereneki’s Bend the bed near the hanks was filling up, but not at the centre. Ac the mill the tailings averaged about ten per cent, of Sometimes .barges had no river sand ; at other times it made up to 20 per cen> The bank at the old junction had extended considerably since the Ngararalii cut was made. Before the dredge was built the bank was practically all river sand ; since the Waihou was cut off the proportion of mining tailings had increased greatly. The finer tailings would travel easier on .the bed of a stream when once they were shifted. After -settling they became more impervious to water —they a' greater density. As long as the tailings were in a flocculent condition they were not troublesome to handle. Light freshes, followed by a flood, only caused a light deposit. After a long’ spell of fine weather a flood would deposit large quantities of tailings on tfie banks. When the Waihou is in flood and the Ohinemuri not so high, there would be more deposits of mining tailings. Flood-gates now prevented deposits of tailings in the drains. A flood the equal! of that in 1910 was possible again. The Ohinemuri, usually rises before the Waihou. When opposite conditions occurred, dr both rivers became flooded at the same time, land round about would be flooded; A river high in flood would not be carrying much tailings. If mining operations were restricted the deposits would settle .better. His company had opposed Pereneki’s cut being made because if the willows were cut the water would remove the sands on the banks. Personally, he‘ considered -the cut would enable the

water to get away from the Ohinemuri more expeditiously. There was always a possibility of a revival of mining activity. Further deposits of mining tailings would not benefit the river. Improvements in mining meth- I ods were continually being made, but fine grinding would always b.e necessary for Waihi quartz. At Waiorpngomai the quartz would not need 'to be finely ground. He believed the Tui area was the same class as a.t Waiorongomai. He considered Mr Young’s cross-sections of the river, taken while his company was operating were quite misleading. The auger test was not as reliable for testing the finer deposits as a piece of bicycle tubing. Mr Morgan’s silica .test was probably quite’correct in theory, but in practi.ee it may not be exact. He would ’not expect to find more than two per cent, of mining tailings hi the Waihou. Deposits that would pass a 100-mesh screen/and refuse a 150' mesh would vary in value from time to time. He knew of no original cross-sections, of the Ohinemuri, He thought tailings would continue to b c I deposited in the Ohinemuri until the stream’s velocity was increased. Pereneki’s cut would assist the velocity by giving a straighter run. The river would not have too great a falU if the cut were made.

To the Chairman : The Waihou had enough velocity to keep all pumice sand continually moving. He considered the pumice sand 'meeting the tailings from the Ohinemuri tended to keep the lower reaches from- filling up with tailings. He confirmed Captain Ragg’s theory that when a river r<ises in flood time'the bed also rises ; and that when the flood recedes -he bed lowers.

To Mr Clendon: His .company s ■operations were confined to the bed of the river. Jle considered his estimate of 2,200,000 tons of deposits a fair one. Wheii his company ceased operations about -three years ago the river was fairly fit for navigation The offer to deposit the 2,000,000 tons on -the land after treatment was a genuine one. He thought that his company had won between £300,000 and £4oo*ooo worth of bullion from the river tailings. He did not agree with Mr Couper’s estimate of the amount of .tailings deposited in the sea. He believed there was timber growing on the banks of the Lowei Waihou many years ago. The Ngararahi cut was necessary to reduce damage done by floods in either river. The old island at the junction was almost wholly river sand when his company commenced operations. He agreed with Mr Adams’ statement that when operations ceasfed at Waikino for a day or so the river at Kopu became clearer. - ,

To Mr Richmond : Slimes was practically the material that would pass a 200-mesh screen.- He could not show flocculent material) in water , he might ,as well be asked to point out an atom! Slime deposited in the water a mile below the Extraction Works would form a bank extending the width of the stream and probably 200 yard-s. upstream and the same distance downstream. In flood time, as soon as the water penetrated this bank, the whole bank would soon be removed easily. When the river is in flood a large amount of the coarse sand is shifted. The banks of the Ohinemuri are steadily widening back to. their original positions. To Mi* Hanna : Even coarse tailings in the river would tend to become swampy or spongy in places, sufficiently so that they would not bear the weight of a man. If tailings from the new gold find near Mangaiti were similar in character to the quartz the Tui damage l to the river was likely? Paeroa Borough is only a small part of the area 'that it-is proposed to improve. - The stop-banks at Paeroa are part and parcel of the scheme and very necessary to the town itself.

To Mi* Gilchrist : He could not say that the cut at Ngararahi would lower the river as far upstream as Te Aroha, but ’there may be some slight effect even at Te Aroha.

To Mr Montague: The protective works were, he believed, designed partly to make the rivers effective as sludge channels. To Mr Clendon : No centre would be more benefited by the protection works, than Paeroa. Paeroa deserved the protection that is. being afforded. The damage was caused by mining tailings, and should be repaired principally by the mining interests. Some of the surrounding lands had been greatly improved. Paeroa had •suffered by the cessation of steamer 'traffic right up to the town. Counsel: The Northern Co. does not want to send boats right to Paeroa, and will not alter its plans even >f the river is improved. Mr Rhodes told us that. The boats could not spare the time between .tides to come right up. Continuing, witness said the stopbanks at Tirohia and Mangaiti would be of great benefit for they would confine the water to its proper channel and thus scour out a deeper channel. To Mr Johnstone : He could not indicate any improvement works that had increased the Ohinemuri’s velocity. The works are not yet sufficiently advanced. It is n&’ use turning all the water down one channel until provision has been made in the lower Waihou to d.ea’l with the .extra water.

Counsel: Public Works Department has no intention of putting in the Pereneki /Out, under the present

scheme. The Chairman: The Commission may recommend the cut being put through. Counsel : If so, the cost will be in addition to the £625,000 scheme.

Mr Aitken, continuing, said the construction of Pereneki’s cut and the removal of the willows would contribute largely .to the success of the improvement works. The Ohinemuri River is very much better to-day than it was ten years ago. He did not think slimes would settle in the river between the junction and the Extraction Works. The slimes re-deposited by the Extraction Company go out to sea; also the greater part of the slimes from Waikino and W.aihi. It would not have paid his company to le£ the tailings go' below the junction, for they would have become mixed with the Waihou River sands, making treatment unprofitable. The Ohinemuri brought down a great deal more, river sands than slimes. Currents change in rivers from time to time. Water flows faster in the middle of a stream. It was possible that Mr Morgan’s bullion test and silica test, though agreeing,',were incorrect. Even if Pereneki’s -eut w.ere made the willows cut, and the stop-banks completed, some dredging in the lower Waihou would be necessary to prevent flo.od causing damage. His company was the principal opponent to the scheme some years ago for cutting through at Pereneki’s.

x To Mr Porritt: He would not expect to find as much slimes in the river at Kopu as in the Upper'Ohinemuri.

To Commissioner Shortt: Farmers, on observing deposits on their land, had a tendency to assume it was all mining tailings. The mining companies were blamed for more than was their due.

To Commissioner Buchanan: A navigable. river was of very great importance to Paeroa. He knew of no other town similarly situated. Much of -the river trouble was caused by the'depositing.of mining tailings. Any industry should be prepared to pay for any damage it might do To put the tailings in the swamp half a mile from the ■ Extraction Works would have cost a jgiod deal more than to deposit them in the Ohinemuri 'the same distance away—about fourpence per ton. After nearly every flood there would be a deposit of up to about three inches of tailings on the land inside Pereneki’s/Bend. The primary causes of ceasing extraction work was the higher costs of materials and falling values. Courtney Kenny, licensed surveyor, Paeroa, said he knew the river near the old junction very well. He produced a photograph of his home and the river taken before the r e was any silt coming down the river. Another photograph taken from the same place years later also produced. When the first photograph was steamers used to come past. He had actually stood on the bank an touched the steamers as they went by. When there was 12ft of water then there is now from Bft to lOKof deposit. Witness described the state of a property (across the river) that was formerly leased by his father. A budget of photographs was produced to illustrate comparisons between the oldtime and present conditions ; 'also a survey tracing of the locality in 1890. He had surveyed the whole neighbourhood of the Waihou River from Tirohia down to Waimarie Bend/ Near the junction water that overflows the banks at flood time has very little run; it" is nearly stationary. H? knew of-deposits up to 3in Jn dept'ij on Mr Laughlin’s farm. The depth of deposit varied according to the length of grass, or size of obstacles. Thirty years ago the Patiki plied to Thames and the Kotuhu piled from Auckland to Paeroa and occasionally right up to Matamata. Trading cutters often came up to Paeroa wharf, being assisted by the tide and a rowing boat, or poling. The poles would be between 20ft and 25ft long, and frequently 'they could not touch bottom. Near the mouth of .the Kaoniti Creek he had seen the tide rise 4ft. The river has changed so much in 30 years that it is scarcely recognisable; the water is dirty and the banks have contracted. The old steamers, Paeroa and Ohinemuri, used to draw about sft to 6ft. His launch, only drawing 2ft, had difficulty in negotiating the same course nowadays. The Waihou was/ not so deep as the Ohinemuri. The o.ld island at the junction was formed by deposits round a large willow branch that had become stranded there. He had seen water from the flooded-Ohinemuri flowing up the Waihou on several occasions.. J To Mr Gilchrist: In the Matamata country, beyond Te Aroha, the river banks were soft and sandy, 30ft or 40ft above water between Te Aroha and Waiorongomai bridge. Upstream from Waiorongomai to Stanley Landing the banks were not so high. To Mr Johnstone : It was certainly not a fact that 'the whole place was a swamp 30 years ago. The swamp lands were being largely benefited by the stop-banks. The'flooding of th i

old Te Aroha road was because of the river being choked by the mining, occuring across the Moananui swamp. The men owning these lands had paid a lot alr.eady in putting in their own drains, but should pay a quota to the improvement’s. 1 Mr Richmond : And the settlers were too lazy to pull a willow out of the river ?

Have you eve’’ tried to pull out a willow ? (Laughter.) To Mr Richmond: He had never seen 9ft of water in Paeroa nor on old Te Aroha road. He had seen lit of water over the old Te Aroha road. To Mr Johnstone : The photographs taken years ago (produced) were typical of the neighbourhood. There were plenty of houses in the localityThirty years ago the whole Plains were not a swamp. Netherton was not a swamp. Most of the Awaiti was swamp. There were several hundred acres of swamp at Rotokphu, but not 4000 acres, as stated by an earlier witness. The water whicn flooded the old Te Aroha road came across Mpananui’s flat from jthe Ohinemuri, due to the mining debris choking the natural outlet. Stop-banking was improving a lot of ■ land. He did : not think any of the settlers had done one pennyworth of damage by depositing debris. He did not remove from his residence near the junction because of floods.

Mr Porritt here stated that the bulk of his further evidence would be documentary. He did . not think he wou'd occupy more than half a day. Mr Hanna thought a Sj day would be, sufficient for his evidence. Mr Gilchrist /suggested a day and a half as the time required ,to hear his witnesses.

The chairman thought a week would see the conclusion o r evidence. It was decided io adjourn until 11 a.m. cm Thursday, September 1, at Paeroa.