OPEN-CAST MINES

Greymouth Evening Star, 9 August 1946, Page 3

OPEN-CAST MINES

PROGRESS IN HUNTLY DISTRICT

NEARLY 200,000 TONS WON [SPECIAL TO STAR.] AUCKLAND, August 7. Nearly 200,000 tons of brown subbituminous coal have been won from the three State open-cast mines in the Huntly district. In. spite of the unusually heavy rain, the coal is still being dug from the sodden country at Kimihia and Glen Massey, but a slip has covered a large face of coal at Glen Afton and production has temporarily ceased there. Much of the slack coal is being used by the King’s Wharf and Huntly steam power stations, but the lumpy coal is going to the railways. The Huntly power station is burning only coal from Glen Massey for test purposes and has found it eminently suitable. At Lake Kimihia,.the largest opencast mine in the North Island is being worked over the site of one of the oldest orthodox mines in the Waikato. The work there is being conducted by a private contracting firm for the Mines Department, and representatives of the company are confirmed believers in the value of the open-cast method. Criticisms of open-cast coal have been based. on the poorer qualities obtained in some of the other districts and it is unfortunate that Huntly open-cast coal has been regarded as being in the same category. Lake Forced Back

Lake Kimihia has been forced back 35 chains from its original shore by stopbanks still being strengthened by spoil removed in strippings the average overburden of 40ft from the coal. The area being stripped and mined is 25 acres, but a Mines Department punt is taking further test bores over the south-eastern part of the lake, and should this prove suitable the acreage will be considerably increased and the life of the mine probably trebled. A tentative estimate has been made that 610,000 tons of coal lie under the proposed new portion. The first two bores taken have revealed seams of 29ft and 24ft. The 25 acres at present under development are estimated to have a life of three years.

Stripping work at Kimihia has been abandoned for nearly three weeks because of the wet conditions and the huge electrically-driven shovel, whose grab has a capacity ol five cubic yards and which can shift 2500 yards of clay a day, is lying idle. The overburden stripping is now moving away from the old mine workings and soon the shovel will be able to move about and dig solid coal. The first of the 14 sections has been worked out, but a large part ol the next two sections has been uncovered and the coal is being dug by a “flying-fox” or slack-lime grab, which conveys it to hoppers above the railway line. Seams of Varying Thickness

Seams of thicknesses varying from 10ft to 29ft. exist all over the present field. In the ten acres under which the old orthodox mine runs the seams range from 2311 to 29 ft. An inch of coal over an acre is estimated to yield 100 to 120. tons of coal. Nearly 90,000 tons of coal have been taken already from earlier open-cast hillside workings at Kimihia and from the lake site. Thirty-two of the 50 acres at Glen Massey, about 20 miles from Huntly, have been stripped of overburden, and 54,000 tons of coal have been taken out. This hillside mine is being developed with bulldozers arid a steam shovel, the Public Works Department stripping the overburden and a private firm removing the coal. Three seams have been revealed, the main bottom seam being sft thick. Only the second and third seams are being worked. During last summer a fire-break was made to prevent dangerously close bushfires from eating into the revealed coal. Glen Afton has produced 40,000 tons of coal, but difficulties have arisen with the wet weather. All the work there is being done by the Public Works Department. A whole hill has been eaten into with huge earth-moving machinery to disclose seams of 9ft to 16ft in thickness. The overburden of soil has an average depth of 40ft, but in places is as high as 110 ft. Spoil removed from the hill will be returned to fill the efivity when the coal has been mined.