Show Moon Lake Dam Outlet S Tunnel Holed Through Construction Progresses On Schedule Despite Loose Formation Drawback back I DIRT SLIDES CAUSE CHANGE IN DESIGN OF MAIN l SPILL SPILLWAY V A Y Construction of Moon Lake Dam took tools a long stride forward at noon Monday September 2 when the two tunnel headings met on ont on alignment and grade completing the pioneer bore for the full length of the 1100 foot outlet tun tun- nel Enlargement of the tunnel excavation to a 13 foot diameter and the contemporary Installation of steel liner plates will immediately immediate immediate- l ly r follow The structural condition of the tho ground through which the tunnel was driven is described by Dr Chas P P. P Berkey consulting geologist geologist geologist gist as quartzite and Md limestone limestone limestone lime lime- stone beds all badly jammed and deformed by the folding and faulting faulting faulting fault fault- ing that took place in f former farmer times The quartzite and lim lini tone formations were further sifted and badly broken in a late Ice Age by a tongue of glacial 1 ice that moved down the valley ana and plowed its way across the ilie spurs spurn extending out from the main valley valley valley val val- ley wall Tunneling through these stratas straw w was s hazardous the ground requiring careful timbering thru- thru out That the work Vas was was' accomplished accomplished accomplished without serious mishap reflects creditably on the efficiency efficiency effi effi- of th the contractors contractor's superintendents superintendents super super- and the skill of his hia workmen All labor was vas requisitioned requisitioned through the local Reemployment Reemployment Reemployment Agency An unusual condition developed in the tunnel excavation through the limestone formation Because of the ready t. t ady access of air through the seams s and open joints into Conti Continued on Page 8 MOON l LAKE TUNNEL HOLED THROUGH Continued From Page 1 the underground spaces tho the loose mass was frozen and attains a freezing below temperature on a large scale This condition apparently apparently apparently is unchangeable lasting throughout the summer months not only to maintain ice lee in the of the rock but to freeze water placed inside the tunnel l penetrating the ground It constitutes con- con a successfully operating natural refrigerator Excavation for the side channel spillway as originally designed developed that the shale formation above the proposed spillway structure is of a blocky character full Cull of checks mud gouges and leachy faults of disintegrated ma ma- erial A number of slides occurred as the the excavation excavation neared completion comple comple- tion raising serious doubts as to he stability of the permanent slopes above the spillway ture After a thorough investigation tion ion on the ground and careful by Reclamation engineers en en- from the Denver Office a change hange has been recommended to toan toan an m open channel type of spillway to be located on the right abutment abutment abutment abut abut- ment using thi three ee automatic radial gates for controlling the spillway discharge The spillway channel as recommended will be rectangular ular in section with sidewalls and of concrete construction tion With the adoption of the proposed change the inside diameter diameter diameter dia dia- meter of the lower portion of the tile outlet tunnel will be reduced from sixteen and one half feet to ten fe feet t making the tunnel of uniform uniform uniform uni uni- form section throughout Underground exploration made possible through the completion of the pioneer tunnel indicates that the outlet is entirely safe as now planned T. T E. E Con Connolly of San Francisco Francis FrancIs- co has contracted to complete the dam on or before December 31 1936 and progress to date would indicate that this time limit will not be exceeded not withstanding changes in design All major purchases purchases purchases pur pur- chases of material are made thru the office of the Chief Engineer of the Bureau of Reclamation Denver Colorado The work is under the direction of the Bureau of Reclamation with E. E J J. J West- West Construction Engineer in immediate charge of the project project project pro pro- |