Progress of Excavation.
Owing to the numerous sections of poor rock, interspersed throughout the work with stretches of sound rock, the progress of the excavation was very irregular, especially in 32d Street. The rate of excavation in good ground is shown in Table 1. In the sections of bad ground, the operations of excavation, timbering, and lining were often carried on alternately, and it is impracticable to include them in the table.
TABLE 1.—Progress and Methods of Excavation in Good Ground.
Thirty-Third Street.
| Type of excavation. | Tunnels. | Worked from: | Dates. | Time elapsed, in days. | Length of tunnel excavated, in linear feet. | Average advance per day, in linear feet. | Methods and conditions. | |
| From | To | |||||||
| Full-sized single tunnel | B | 1st Ave. shaft. | Feb. 28, 1906. | May 12, 1906. | 74 | 346 | 4.7 | Top heading and bench. Muck loaded by hand. |
| Full-sized single tunnel | A | 1st Ave. shaft. | Feb. 28, 1906. | Apr. 30, 1906. | 62 | 255 | 4.1 | " " " " " " " " |
| Full-sized twin tunnel | A and B | 1st Ave. shaft. | Aug. 23, 1906. | Jan. 5, 1907. | 136 | 789 | 5.8 | Top full-width heading and bench. Muck loaded by steam shovel. Working exclusively on this heading. |
| Full-sized twin tunnel | A and B | Intermediate shaft. (West of shaft.) | Apr. 4, 1906. | Oct. 31, 1906. | 210 | 730 | 3.5 | Top center heading and bench. Muck loaded by steam shovel. Working alternately in headings east and west of the shaft. |
| Full-sized twin tunnel | A and B | Intermediate shaft. (East of shaft.) | Apr. 4, 1906. | Oct. 31, 1906. | 210 | 783 | 3.7 | Top center heading and bench. Muck loaded by steam shovel. Working alternately in headings east and west of the shaft. |
| Full-sized twin tunnel | A and B | Intermediate shaft. (East of shaft.) | Nov. 1, 1906. | Dec. 26, 1906. | 56 | 311 | 5.5 | Top full-width heading and bench. Muck loaded by steam shovel working exclusively on this heading. |
| Exploration drift | A and B | Intermediate shaft. (West of shaft.) | Mar. 1, 1907. | July 23, 1907. | 145 | 947 | 6.5 | Exploration drift about 9 ft. by 12 ft. Mucking by hand. Fourteen timber bents were placed in March, and seven in April, 1907. |
| Twin tunnel. Enlargement of exploration drift | A and B | West shaft. (East of shaft.) | Sept. 6, 1907. | Dec. 4, 1907. | 89 | 603 | 6.8 | Drift excavated to full width and bench. Muck loaded by steam shovel. |
Thirty-Second Street.
| Type of excavation. | Tunnels. | Worked from: | Dates. | Time elapsed, in days. | Length of tunnel excavated, in linear feet. | Average advance per day, in linear feet. | Methods and conditions. | |
| From | To | |||||||
| Full-sized single tunnel | C | 1st Ave. shaft. | Jan. 25, 1906. | Apr. 30, 1906. | 95 | 367 | 3.9 | Top heading and bench. Muck loaded by hand. |
| Full-sized single tunnel | D | 1st Ave. shaft. | Jan. 27, 1906. | Apr. 30, 1906. | 93 | 354 | 3.8 | " " " " " " " " |
| Full-sized twin tunnel | C and D | 1st Ave. shaft. | May 22, 1906. Aug. 11, 1906. | July 24, 1906.[E] Nov. 29, 1906. | 173 | 810 | 4.7 | Double heading and bench. Muck loaded by steam shovel. Stretches aggregating 200 ft. narrowed to about 25 ft. and later enlarged are included. |
| Narrowed twin tunnel | C | Intermediate shaft. | Mar. 19, 1906. | May 28, 1906. | 70 | 58 | 0.8 | Excavation about 30 ft. wide. Top full-width heading and bench. Muck loaded by hand. Steam shovel not installed. |
| Full-sized twin tunnel | C | Intermediate shaft. (East of shaft.) | May 29, 1906. July 18, 1906. Aug. 12, 1906. Jan. 15, 1907. Feb. 17, 1907. | July 3, 1906[E] July 31, 1906. Nov. 23, 1906. Feb. 5, 1907. Mar. 21, 1907. | 208 | 1,206 | 5.8 | Excavation about 30 to 35 ft. wide. Top full-width heading and bench. Muck loaded by steam shovel. |
| Full-sized twin tunnel | C and D | Intermediate shaft. (West of shaft.) | Dec. 1, 1905. | May 10, 1906. | 161 | 225 | 1.4 | Double heading and bench. Part of the muck handled by hand and part by steam shovel. |
| Exploration drift | C and D | Intermediate shaft. (West of shaft.) | Feb. 1, 1907. | Sept. 13, 1907. | 225 | 1,033 | 4.6 | Exploration drift about 10 ft. by 13 in. Muck loaded by hand. 14 ft. timbered. |
| Twin tunnel. Enlargement of exploration drift | C and D | Eastward from open cut. | Feb. 1, 1908. | Feb. 14, 1908. | 14 | 65 | 4.6 | At portal of twin tunnels. Drift excavated to full width and bench. Muck loaded by hand. 12 ft. timbered. |
| Twin tunnel. Enlargement of exploration drift | C and D | Eastward from open cut. | Feb. 15, 1908. | Apr. 14, 1908. | 59 | 524 | 8.9 | Drift excavated to full width and bench. Muck loaded by steam shovel. Full-width tunnel timbered for 26 ft. independently of the main excavation. |
[E]Time and distance omitted while working through timbered stretches.