ARAPUNI.

Auckland Star, Issue 38, 14 February 1929, Page 11

ARAPUNI.

"ON SURE FOUNDATIONS"

LARGE FACTOR OF SAFETY. COUNTRY PROVED BY ACTUAL TESTS. diminution of lkakauic. (Special to "Star.") AKAPL'NI. tnis -lav. public need have I!fear lor 11. >afeiy of Arapuni. Ibe foundations ot the dain are quite -ate." This reassuring -tatcuient was made to a "!jtar" reporter yesterday by Mr. T. Kabonc. Public Worics engineer, in charge at Arapuni. Public anxiety, with regard to the safety (if the Arapuni iiam lia- not been minimi.-ed by the recent r-tateinents oi Mr. IT. M. ( hry-tall. <on-ulting engineer of (_'hri?tchurch, tJiat the dam i- oit>tructed in country of a decidedly doubttill nature.

People resident in the area which would be affected in the e\ent of a rupture are decidedly uneasy, and one case is known where the wife of a .-.ettler ha.- reached su-'h a state ot nervous ]>ro>t ration over the prospect.-, of a burst dam that her hu>band hasbeen forced to place his property on the market for >ale. with a view 10 leaving the district as quickly as possible.

Discussing the situation at Arapuni, Mr. Kabone said the dam stands oil what L'eoligists describe as pumiceous breccia. Mr. Chrystall had referred to it as ash. He (Mr. Kabone) was not prepared to say that it was not ash, but what he did know was that it had a strength of 70 to 100 tons per square foot. The greatest pressure exerted on it by the dam when full or empty was eight tons per square foot, which provided a very large factor of safety. The country 011 which the dam stood had been proved by actual tests to be l."> 0 feet thick. The public could rest assured. therefore, that the ground on which the dara stood, was quite above reproach.

Mr. Rabone further stated that to prevent tlie water seeping round tlie sides or below the dam. provision had been made by excavating- deep, narrmv trenches, which had Wen filled wish high grade concrete. These cut-off wallwere very extensive compared with ruesize of the dam.

Ke >tated that the leakage at the dam at the present time was in tiie vicinity of -">OO gallons a minute. When the lake was first filled the leak wa--700 galions a minute. Each little leak was observed daily, and the only chan-je recorded had been this diminution of :1m I pallons per minute. For a dam of this size tiiis leakage was considered quite reasonable. The Californian Disaster. Comparing Avapuni v. it li the Si. t rancis dam. California, which burst !*.*- cent Iv, Mr. Kaboue sa;d the foundation of the two dams were totally" differed<. The country on which the St. Francis dam was constructed was what witknown as "hard-pan." which reallv was a mixture of stiff clay and shins: Prior to the construction of the dam. this land was high and dry. Immediately it became inundated, "however, i great change took place due to saturation. which >oftened the clay. A chemical change also occurred in ti> • ■ -otter matrix, which caused it to break readily under water. Mr. lfabone -aid he understood the St. liancis dam had only been filled a week when the -iructure (o]h;p-ed. in the case oi Arapuin the foundati"i,were under water pie* iou-I v . so that i.o change, chemical „r otherwise, was anticipated. The rock certainly had n-.t been weaken.-1 by any change. - ,^' L . ati: -" u : h t . had been on :/.- its very ' Juul sc. n j.raet ■>-«! Isy the «lio':- of 1 k/toundat !«■!]- unc>\ ei'ed. J),- i. e ,. ;| , -pon-ib!e f.,r ov ,. r the ground ~,i ha\.n« all 1 lie weak countrv remov..'! /"H e puldic can rc-t ! .eriV : -;iv as-n.' ; .J mat the Arapimi dam -iai;-l- ..m cxcci!,- Jt l i-hndation-. • he ((.included.