ARTESIAN WATER

Dominion, Volume 38, Issue 4, 29 September 1944, Page 3

ARTESIAN WATER

Effect Of Proposed Hutt Works On Supply WARNING BY ENGINEER “Deterioration either in qualify or quantity of the artesian water supply onwhich the Hutt Valley is almost entirely dependent, while Wellington city has obtained one-third of its supply during dry weather from the underground sources, would be a very serious matter for the city and for the local authorities in the valley. itself. These supplies are now committed to the extent of some 10,000.000 gallons daily,” said Mr. E. R. MeKillop, deputy city engineer for Wellington, when giving evidence before the Hutt Harbour Commission of Inquiry yesterday. “This deterioration could be occasioned by interference at the mouth of the Hutt River. It is difficult to estimate the financial value of these supplies to those authorities using them, but it is certain that if a' substitute supply had to be obtained from some gravity source, this could not be done for much less than £750,000. The artesian supply is considered to be capable of further development by the Hutt Valley authorities, so that the loss, if the supply were prejudiced. would represent a much higher figure. From dredging or pile-driving operations the interference would arise suddenly and. without an alternative supply available, might create a condition of emergency in the areas now supplied from these underground sources. “No plans are available to the city engineer of the proposed works at the mouth of the Hutt River, but it is unlikely that these can be constructed with the Wellington City Council’s auxiliary installation in its present position. The proposed river diversion shown in the ATawson report passes through the location of the council’s present station. The well system would also be interfered with. This would mean moving the installation to another part of the_valley at a roughly estimated cost of £35.000. “It is considered that the construction of an overseas shipping port at the mouth of the Hutt River would constitute a grave danger to the maintenance of the artesian system —at least if the construction of port facilities were attempted by orthodox means. Except for isolated pockets, the water-bearing strata at varying depths throughout the valley appear to be inter-connected, so that a major disruption affecting the uppermost stratum would affect the whole of the underground supply.” Bores put down by the Wellington Harbour Board at Point Howard'in July, 1929, before the construction of the wharf there, said Mr. MeKillop, penetrated the sealing layer and produced an np-current of artesian water of such velocity that for some time the diver.was unable to approach the bole, subsequently found to be 41ft. deep, with a minimum diameter of three feet at the bottom. The use of draglines by the Government in 1937 for the reclamation round Scabey Island, operating in the Hutt River on the site where it was now proposed to construct, the harbour berthage. reduced the flow by 25 per cent, from artesian wells in Gear Island, and a greater drop in the head was reported from the pumping station at Gracefield. Some valley users were completely robbed of water through pressure loss, which was restored by refilling the hole made. Responsibility for disturbance of the sealing layer was not at the time officially accepted by the Government. There were depths recorded by soundings over local areas considerably below the adjacent harbour fioor off the mouth of the Hutt River. It was probable that these indicated flows from the artesian strata which might’have been caused by dredging operations in connexion with the Thorndon reclamation.