NEED OF ROCK EXCAVATION ON COUNTRY ROADS 67 



attempted that hand work cannot touch, because of the depth 

 to which the holes may be driven by steam power. 



The total cost of handling rock, including the work with the 

 drill, was very moderate, being at $1.11 per cubic yard less 

 than the average contract price, which is usually about $1.75 

 per yard. With the experience gained, the work could be 

 duplicated at a considerable saving of expense. Upon one job, 

 carried on since with our own help, an average of 4 feet per 

 hour was attained, with a labor account per day less than half 

 that in the former case. One run of S hours gave 42 feet with 

 14 holes. These are not record-breaking results, but what has 

 been actually done in very hard rock by amateurs. 



NEED OF ROCK EXCAVATION ON COUNTRY ROADS 



In order to investigate the question of the need of rock exca- 

 vation on our country roads various computations were made, 

 and a section of road 5^ miles long was carefully examined to 

 find what amount of rock work was required. 



1. Since it is evident from the table, page 62, that yard for 

 vard rock excavation is much more expensive than earth fill, 

 great care should be exercised not to handle rock when earth 

 can be easily drawn to cover the same. In the experiment 

 already related, if the grade had been carried two feet higher, 

 thus avoiding all rock excavation except for sidewalk, the fol- 

 lowing computation would hold : 



Extra embankment, 1,100 yds. earth, at 27^ cts. . $300.00 

 Extra embankment for sidewalk, 51 yds. earth, at 



27^ cts. ........ 14.00 



Total increase in expense .... $314.00 



Stone, replaced by earth at saving of 83^3 cts. per 



yd., 181 yds., ....... 151.00 



Net saving by larger use of steam drill . . . $16300 



If a grade one foot higher than that adopted had been used, 

 practically the same rock surface would have been covered and 

 the total expense have been still greater. Therefore, as a mere 

 matter of expense, a standard grade was attained in the best 

 way. 



