The material penetrated was red sandstone varying all the way from very hard and close-grained like marble to a tough red clay. It was originally proposed to penetrate 50 ft. into the material with a diaphragm wall built in a cut-off trench, but the scheme was changed to a 30-ft. diaphragm wall extended by 30 ft. of grouted zone underneath. In the cut-off trench were placed 5-in. diameter pipes, of No. 24 gage galvanized iron with stove pipe joints; 26 ft. of such pipe, supplemented at the top by 4 ft. of 4-in. wrought-iron pipe, completed the casings to the depth of the trench. The pipes were placed 3 ft. apart in two rows and staggered so that the effective spacing was 18 in. The boring and grouting were done through these pipes after the trench had been filled with concrete. Two Ingersoll-Rand class G-0 Davis Calyx type drills were employed for doing the boring, using the Calyx bit in the clay and the chilled shot equipment in hard rock.

The scheme of stream diversion required the work to be prosecuted in two sections; on the first section alternate holes 6 ft. apart were drilled, tested and grouted, then drills came along again on intermediate holes; on the second section holes 12 ft. apart were treated first, followed up by an equal number half way between, and then by double the number to reduce the spacing to 3 ft. The material was very seamy and much trouble was encountered from pieces which dropped in from the side, thus choking and binding the drilling tools. Grouting had a marked effect in stiffening up adjacent ground so that subsequent drilling was easier.

Drilling was prosecuted continuously in three shifts with two men on each drill. Drillers received 40 cents an hour and helpers 30 cents. The outside diameter of the bits was 2 3/8 in. and of the core 1 13/16 in. The maximum eight-hour progress on drilling was 19 ft. and the average was 6 ft., but omitting some of the earlier experimental work would make the average 8 ft. After the holes were drilled they were tested for leakage, a nearby canal being a convenient source for water at 127 ft. head.

The grouting was done with the Caniff machine described, a small motor-driven compressor furnishing air at 100 lb. pressure.

Leakage of water under

127-ft. head, gal. per min. per boring

Sacks of cement used in grouting, average per boring

Primary holes, 18 first section......

33.1

10.3

Secondary holes, 17 first section.....

5.5

12.7

Primary holes, 10 second section.....

71. 5

42.3

Secondary holes, 10 second section...

28.3

17.6

Tertiary holes, 11 second section.....

11.2

4.5

Second tertiary holes, 11 second section

6.4

3.7

Lin . ft. of cut-off treated...................

220

Number of holes drilled and grouted................

83

Average depth holes drilled and grouted, ft......

32

Total depth holes drilled and grouted, ft..................

2593

Total sacks cement used...........

1174

Total cost per ft. of hole............

$3.57

Total cost per ft. of cut-off wall....

42.12

Total cost of boring and grouting..............

9267.17

Cost of equivalent length of cut-off by trenching and concreting, based on figures for 30-ftt. trench, probably minimum of.......

12,590.00

Saving by boring and grouting process..................

$3,322.83

FEATURE COSTS

Total

Ft. of hole

Foreman......................

$753.77

$0.29

Making forms,placing pipe.............

474•94

0.18

Drilling.............

2397.81

0.93

Grouting............

742.68

0.29

Corral expense...........

98.00

0.04

Supplies, fuel and oil.............

19.60

0.01

Supplies, lumber..............

75.03

0.03

Supplies, miscellaneous..............

192.32

0.07

Material, cement............

814.45

0.31

Material, pipe...............

1121.38

0.43

Repairs.......................

186.74

0.07

Power....................

86.83

0.03

Repair plant.............

138.46

0.05

Equipment depreciation.......................................

911.87

0.35

Total field cost......................

$8013.88

$3.08

Engineering...............

487•03

0.19

Superintendence.............

195.43

0.08

Clerical....................

165.45

0.06

Camp maintenance...................

306.54

0.12

General office expense................

98.84

0.04

Aggregate cost.........................

$9267.17

$3.57