The Alaska daily empire., 1916-01-31
 CAUSED BY
 BLUNDER

of the chief topics of conversation in Juneau yesterday. Many residents have been visitors at some time to San Diego. Many have known of the great engineering feat of the otay dam. There are many engineers now in Juneau and companies also who are interested in the dam and reser- voir construction.
 D. D. Stewart, one Of the well known local mining engineers and a United States mineral surveyor, as well. has at the request of The Elm pore prepared the following interest ing article on the Otay Dam which will be read by interest, not only in Juneau but elsewhere. Mr. Stoyart writes as follows:
 The recent failure under flood con. ditions of the Lower Otay dam In San Diego County, California, with it's at- tendant great loss of life and destruc. ton of valuable property, renders in. tercsting and significant the account of the structure as given by MT. Jas. Dix Schuyler. civil engineer in his treatise on Reservoirs. published in 1909:
 That the possibility of such failure as has occurred was not unforeseen by competent engineers at the time the dam was being built Is rendered apparent by @ perusal of NIT. Schey ler's account of the dam. which fol lowed a visit to the site during the period of construction. This failure may no doubt be justly attributed tc an ill-advised change in the plans oi the builders. whereby the original de sign, as prepared by the engineers was abandoned after the commence ment of the work and new type oi structure, heretofore unknown to the engineering profession. erected upor tho foundation already prepared.
 Dam Originally Designed
 The dam as originally designed was to be entirely of masonry. The site which is but % miles southeast oi San Diego and within 10 miles of the coast line. is an ideal one for ma-on ry construction. as the narrow gorge cutting through the porphyry dikc which forms the exit of the San Ysid TO and San Miguel mountains. fur nishes excellent bedrock foundations and an abundance of suitable rocl and sand for a masonry type struc ture.
 Hcwever.-presumably from mo tives Of economy-after an excellent foundation of masonry. measuring 6 feet in width. S5 feet In length on tor and 40 feet in height. set in trencl axcavated in bedrock to Q depth O. s1.4 feet below the stream bed hac Teen erected. the change in plan: was decided upon. The credit for tn new type of structure finally erecte' was given to Mir. E. S. Babcock of Sar Diego. former president of the water company who built tue dam.
 Completion of Dam
 The completion of the dam was car ried out as follows: Heavy "T" Iror was anchored to the top of the com ple;ed foundation by means of 1-incl bolts. The vertical leg of the T-iror was then perforated with rivet hole
 paced three inches center to center for the entire length of the dam. IT this was riyited web or sheet stee consisting of plates from to 8 feel wide and from 175 to 30 feet in lengtf and ranginy from O.SS to OPS inche or less in thickness all riveted togeth CT. extending the full length of tho dam end carried up to It's full height
 This sheet of steel was designed to render the dam water tight. Tc give 1t support and to protect 1t from later Injury during construction tho entire sheet was incased in a wall O rubble masonry. 9 feet in thickness except at the base. the lower eight feet being feet In thickness. The forms in which this masonry was placed were left standing in order to lessen the liability to damage to the centrol core by possible settling O the loose rock which later formed the upstream and down stream faces Of the dam.
 With the exception of the centra' core, two feet in thickness, and the foundation of masonry. no portion O. the dam was hand placed. but con sisted merely of loose rock-fill em bankment lying just as 1t was dump ed from buckets carried on cable communicating with the quarrics or the hilisides adjoining the site.
 irregular Alignment
 "The expansion of the steel plates in the central core after they were rivited together. and the obtuse an gle upstream on which they were a ''rst started. which gradually was ob. 'terated by an approach to a straight ''ne toward the top of the dam, gave them a very irregular alignment"
 During the winter of 1s06-7 the wa. tor in the reservoir attained a height of 1O9 feet above the base or 15 feet below the spillway level the greatest recorded height since the completion