DUST PEEVEISTTION AND ROAD PRESERVATION, 1915. 



Gcciured. in three pits adjacent to the road, namely, the Zimmerman 

 pit near station 18 + 00, the Garfield pit near station 95 + 00, and the 

 Haney pit 1,500 feet to the right of station 116 + 00. The free haul 

 of gravel was fixed at 1 mile and overhaul was practically negligible. 

 The gravel was excavated by means of a steam shovel and distributed 

 in rows from dump-bottom wagons. Stones over 2 J inches in 

 size were raked out at the pit or during the spreading. The gravel 

 contained 8.5 per cent of water and weighed approximately 3,000 

 pounds to a cubic yard, measured loose in a dimensioned box. Gravel 

 from the Zimmerman and Haney pits, which were cross-sectioned, 

 increased about 20 per cent in volume when loosened. The loose 

 depth necessary to obtain the requisite compacted depth of 6 inches 

 averaged 7.92 inches and the weight per station averaged 58.5 tons. 

 The spreading was controlled by means of 6-inch blocks and lines, 

 and the gravel was rolled with a 10-ton roller. The mechanical 

 analyses of the gravel are sho"wn in Table 3. 



Table 3. — Mechanical analyses of gravel used for foundation course. 



Zimmer- 

 man pit. 



Garfield 

 pit. 



Haney 

 pit. 



Passing 2-inch, retained on IJ-inch screen 



Passing 1 J-inch, retained on 1-inch screen 



Passing 1-inch, retained on ^-inch screen 



Passing i-inch, retained on |-iach screen 



Passing ^-inch, retained on J-inch screen 



Passing J-inch, retained on y'^-inch screen 



Passing 10-mesli, retained on 20-mesh screen . . 

 Passing 20-mesh, retained on 30-mesh screen . . 

 Passing 30-mesh, retained on 40-mesh screen . . 

 Passing 40-mesh, retained on 50-mesh screen . . 

 Passing 50-mesh, retained on 80-mesh screen . . 

 Passing 80-mesh, retained on lOO-mesh screen . 

 Passing 100-mesh, retained on 200-mesh screen 

 Passing 200-meshscreen 



Per cent. 



11.2 

 4.6 

 5.0 

 9.1 



11.4 

 8.5 

 5.2 

 3.6 

 2.6 

 4.3 

 8.6 

 1.1 

 6.7 



18.1 



Per cent. 



Per cent. 



1.3 



8.9 

 11.3 

 17.2 

 13.3 

 4.8 

 5.8 

 8.3 

 7.3 

 6.4 

 .5 

 2.8 

 13.1 



1.4 

 15.7 

 25.7 

 19.6 

 10.1 

 5.1 

 3.2 

 3.8 

 3.2 

 .8 

 2.4 

 9.0 



100.0 



100.0 



The base of Section II (station 153 + 50 to station 192 + 00) was 

 an old bituminous-macadam surface. It was scarified and reshaped 

 without diflficulty. Where excess material was found it was used to 

 stiffen the shoulders immediately outside the new surface. Where 

 a deficiency of material occurred, new 1^-inch broken trap rock 

 (passing a 2|-inch screen and retained on a 1^-inch screen) was sup- 

 plied. An average depth of about three-quarters of an inch of such 

 stone was added to the penetration course continuously from station 

 153 + 50 to station 158 + 50, and from station 187 + 00 to station 

 190 + 50 a layer 4 inches deep, loose, was used to stiffen the base. 

 The entire base, with added stone, was thoroughly rolled with a 

 10-ton roller. 



The base of Section III (station 192 + 00 to station 235 + 50) was 

 an old "water-bound" trap-rock macadam surface badly out of 

 shape. It had apparently been repaired with limestone. It was 



