404 



REPORT OF THE COMMISSIONERS OF 



this puddling was merely to insure an extra precaution against leakage from possible 

 cracking of the core wall, as well as to prevent water from following along the surface 

 of the masonry. Special care was taken in laying both the core wall and embankment 

 to have them watertight. On the lower side of the dam, at the junction with the 

 main wall, the embankment is held in place by a wing wall, but on the upper side the 

 embankment is allowed to assume the two and one-half to one slope until it rests 

 against the main dam wall. 



MORTAR AND CONCRETE. 



The cement used in the work was delivered in barrels at North. Creek by railroad 

 and from thence hauled by wagon about twenty-two miles over a mountain road. 

 The sand used was obtained from a bank on the shore of the lake about two miles 

 from the dam and was transported to the work in a scow having a capacity of thirty 

 cubic yards per load. The scow was propelled by means of an anchor with a long 

 rope and a windlass, after the ordinary method of moving lumbermen's rafts on lakes. 

 Advantage was also taken of favorable winds by hoisting a large sail. In this manner 

 a crew of six men and a foreman were able to deliver about 720 cubic yards of sand 

 and 180 cords of wood, for the steam boilers, per month, the wood being taken from 

 points along the lake, in some cases several miles from the work. The sand obtained 

 was of excellent quality, being almost entirely free from loam and exceedingly sharp. 

 The mprtar was composed of three and one-quarter parts of sand to one part of 

 cement by volume, except for pointing and for bedding the lowest course of masonry, 

 where two to one mortar was used. The sand and cement were thoroughly mixed 

 dry on a platform by means of hoes until the mixture acquired a uniform color. It 

 was then mixed wet by passing through a mechanical mixer of the paddle type. 



The proportions for making concrete were experimentally determined by 

 measuring the voids in the broken stone to be used, and allowing a little more mortar 

 than necessary to fill the voids. The proportions by volume of the dry materials 

 were one part of cement, three and one-quarter parts of sand and seven and one-half 

 parts of broken stone. This was found to yield an excellent concrete. In making the 

 concrete, the sand and cement were first mixed dry as for mortar and then spread in a 

 layer over the broken stone. The whole was then shoveled into the mixer, where 

 the water was supplied through jets, and all thoroughly mixed by the paddles in 

 going through the mixer. The concrete dropped from the mixer directly into 

 wheelbarrows or derrick boxes and thence was taken to the work. 



