Chapter II: Part 2

April and May were occupied in driving the sheathing down to rock, supporting the trestle, underpinning the adjoining brewery, and excavating the soft material above the rock. On June 2d, 1906, rock was reached, and, by July 31st, the excavation was down to subgrade over nearly the whole 50 ft. in the first length. In the meantime another length was opened up, and eventually a third.

The surface of the rock now seemed to be rising, and the heavy buildings had been passed, so that tunneling was reverted to for the rest of the work, though many difficulties were caused by soft rock in the roof from time to time.

When the excavation for the open-cut work of the Terminal Station had advanced to the line of Tenth Avenue, the contractor started a heading from this point and drove westward under Tenth Avenue until the headings driven eastward from the cut-and-cover portion, were met.

This was done to expedite the work under Tenth Avenue, where the ground was not very good, where there were several important gas and water mains in the street, and where, moreover, the tunnels were of exceptionally large span (24 ft. 6 in.), making a total width of some 60 ft. for the excavation. The excavation for the New York Tunnels was practically finished in January, 1908.

_Drilling and Blasting._--The foregoing short description will serve to show in a general way the scheme adopted in making the excavation. A few details on drilling and blasting methods may not be out of place.

Percussive drills run by air pressure were used. They were Ingersoll-Sergeant, Nos. 3½, A-86, C-24, and F-24. The air came from the high-pressure compressor previously described. This compressor, without assistance, could supply air for nine drills, but, when fed by compressed air from the lower pressure, its capacity was increased three or four times.

The air was compressed to 100 lb. per sq. in. in the power-house, and was delivered at about 80 lb. per sq. in. at the drills. A 3-in. air line was used. The drill steel was 1-1/8-to 1-3/8-in. octagonal. The holes were about 3¼ in. in diameter at starting and 2-5/8 in. at the full depth of 10 ft. The powder used on the New York side was 40% Forcite, the near presence of heavy buildings and lack of much rock cover necessitating light charges and many holes spaced close together.

To compensate the contractor for the inevitable excavation done outside the neat lines of the masonry lining, the excavation was paid for to the "Standard Section Line" which was 12 in. outside the neat lines on top and sides and 6 in. outside at the bottom of the cross-section. The actual amount of excavation done was about 11% greater than that paid for. The distance excavated beyond the neat line, because of the very heavy timbering necessary, was about 2.1 ft. instead of the 1 ft. allowed, and at the bottom about 0.85 ft. instead of the 0.50 ft. paid for.

For a period of 5 months detailed records were kept of the drilling and blasting. About 12,900 cu. yd. of excavation are included. A sketch and table showing the method of driving the heading, the number and location of the holes drilled, and the amount of powder used, is given in Fig. 5. From this and similar figures the information in Table 5 is derived.

TABLE 5.

+========================+=======+=======+=======+======+=======+======| | | FEET OF HOLE | POUNDS OF POWDER | | |DRILLED PER CUBIC YARD | USED PER CUBIC YARD | | | OF EXCAVATION. | OF EXCAVATION. | | +-------+-------+-------+------+-------+------| |Portion of excavation. |15-ft. |19-ft. |24-ft. | | | | | | 4-in. | 6-in. | 6-in. |15-ft.|19-ft. |24-ft.| | |span-- |span-- |span-- |4-in. | 6-in. | 6-in.| | | twin | twin | twin | | | | | |tunnel.|tunnel.|tunnel.| | | | |------------------------+-------+-------+-------+------+-------+------+ |Wall-plate heading[C] | 13.0 | 10.97 | 10.97 |3.77 | 2.85 | 2.85 | | | | | | | | | |Total heading[C] | 7.87 | 8.17 | 7.81 |2.31 | 2.02 | 1.78 | | | | | | | | | |Bench and raker bench[C]| 5.97 | 6.15 | 7.56 |0.94 | 0.93 | 1.13 | | | | | | | | | |Trench[C] | 9.82 | 15.96 | 18.10 |1.84 | 2.49 | 2.73 | |------------------------+-------+-------+-------+------+-------+------+ |Average for section[C] | 6.69 | 7.43 | 8.95 |1.28 | 1.30 | 1.45 | |------------------------+-------+-------+-------+------+-------+------| |Actual amount[D] | 6.82 | 7.27 | 8.95 |1.22 | 1.24 | 1.27 | +========================+=======+=======+=======+======+=======+======+

[C] Figures taken from typical cross-sections.

[D] This gives the actual amount of drilling done and powder used per cubic yard for the whole period of 5 months of observation, but as this length included 280 ft. of heading and only 220 ft. of bench, the average figures (for powder especially) are too low.

Table 6 gives the rate and cost of drilling, and the cost of powder. It will be seen that the average rate of drilling was 2.71 ft. per hour per drill or 27.1 ft. per drill per shift.

Table 7 shows the result of observation as to the time taken in various subdivisions of the drilling operations. These observations were not carried on for a long enough period to give correct results, but the percentages of time spent on each division of the operation are believed to be about right. The headings of this table are self-explanatory. The necessary delays include all time spent in changing bits, making air-line connections, etc. The unnecessary delays are stoppages caused by lack of supplies or insufficient air pressure.

By Table 6 it will be noticed that the cost of labor for drilling and sharpening steels was about $0.29 per lin. ft. of hole drilled. The total cost, including repairs, supply of air, etc., came to about $0.38, as will be seen from Table 8.

_Timbering._--On the New York side nearly the whole length of the excavation needed timbering, to a greater or less extent, and for the most part required timbering of quite a heavy type.

TABLE 6.--ROCK TUNNEL EXCAVATION UNDER 32D STREET, EAST OF CUT-AND-COVER SECTION. DRILLING AND BLASTING.--DETAILED COST OF LABOR IN DRILLING, ALSO QUANTITY AND COST OF POWDER USED.

+=====================================================================+ | DRILLING AND BLASTING. | |-----+-----+------+------+------+-----+-----+------+-----+-----+-----| |Type.|Date.|Total feet drilled. | No. drill shifts| Feet drilled | | | | | | | of (10-hour.) |per man per hour.| | +-----+------+------+------+-----+-----+------+-----+-----+-----+ | |1907 |Head- |Bench |Total |Head-|Bench|Total |Head-|Bench|Total| | | | ing | | | ing | | | ing | | | |-----+-----+------+------+------+-----+-----+------+-----+-----+-----+ |_Ke._|May | 2,971| 5,578| 8,549| 98 | 204 | 302 |3.031|2.734|2.831| | |June | 2,093| 6,194| 8,287| 85 | 223 | 308 |2.462|2.777|2.691| | |July | | 7,627| 7,627| | 268 | 268 | |2.845|2.845| | |Aug. | | 2,552| 2,552| | 95 | 95 | |2.688|2.688| | |Sept.| | 2,133| 2,133| | 79 | 79 | |2.700|2.700| | +-----+------+------+------+-----+-----+------+-----+-----+-----+ | |Total| 5,064|24,084|29,148| 183 | 869 |1,052 |2.767|2.77 |2.77 | |-----+-----+------+------+------+-----+-----+------+-----+-----+-----+ |_Ki._|May | 6,976| | 6,976| 216 | | 216 |3.229| |3.229| | |June | 4,089| | 4,089| 135 | | 135 |3.029| |3.029| | |July | | 3,733| 3,733| | 140 | 140 | |2.666|2.666| | |Aug. | | 6,715| 6,715| | 249 | 249 | |2.769|2.769| | |Estim| |14,742|14,742| | 46 | 546 | |2.700|2.700| | +-----+------+------+------+-----+-----+------+-----+-----+-----+ | |Total|11,065|25,190|36,255| 351 | 935|1,286 |3.152|2.694|2.819| |-----+-----+------+------+------+-----+-----+------+-----+-----+-----+ |_Ko._|May | | 1,617| 1,617| | 55| 55 | |2.921|2.921| | |June | | 2,948| 2,948| | 107| 107 | |2.755|2.755| | |July | | 3,734| 3,734| | 131| 131 | |2.850|2.850| | |Aug. | | 8,260| 8,260| | 290| 290 | |2.848|2.848| | |Estim| | 4,787| 4,787| | 285| 285 | |1.180|1.680| | +-----+------+------+------+-----+-----+------+-----+-----+-----+ | |Total| |21,346|21,346| | 868| 868 | |2.460|2.460| |-----+-----+------+------+------+-----+-----+------+-----+-----+-----+ |Grand|Total|16,129|70,620|86,749| 534 |2,672|3,206 |3.020|2.710|2.710| +=====+=====+======+======+======+=====+=====+======+=====+=====+=====+

+==================================================+=====================+ | DRILLING AND BLASTING | POWDER USED. | |-----+----------+------+--------------------------+--------+-------+----+ | | | | Cost of labor only. | | | | | | | | Drilling and sharpening. | | | | | | | +------+------+-------+----+ | | | | | | | | | Per | | | Cost | | | | | | | | cubic | | | per | | | | | | | | yard. | | | cubic | | | | | | | | | | |yard at| | | | | | | | | | | 11 | | | | | | | | | | | cents | | | | | | | | | | | per | | | | | | | | | | |pound. | | | +----------+------+------+------+-------+----+--------+-------+----+ |Type.| Quantity | |Total.| Per |Actual.|Paid| Total |Actual.|Paid| | | of | | |linear| |for |Quantity| |for.| | |excavation| | |feet. | | | | | | | | in cubic | | | | | | | | | | | yards. | | | | | | | | | | +----------+------+------+------+-------+----+--------+-------+----+ | | Actual. | Paid | $ | $ | $ | |Pounds. | $ | $ | | | [E] | for | | | | | | | | | | | [F] | | | | | | | | |-----+----------+------+------+------+-------+----+--------+-------+----+ |_Ke._| 1,736 | 1,664| 2,331| 0.27 | 1.34 |1.40| 1,595 | 0.10 |0.10| | | 809 | 698| 2,440| 0.29 | 3.01 |3.49| 1,960 | 0.27 |0.31| | | 1,022 | 960| 2,031| 0.26 | 1.98 |2.11| 966 | 0.10 |0.11| | | 743 | 716| 640| 0.25 | 0.86 |0.89| 430 | 0.06 |0.07| | | 238 | 238| 533| 0.25 | 2.24 |2.24| 280 | 0.13 |0.13| | |----------+------+------+------+-------+----+--------+-------+----+ | | 4,548 | 4,276| 7,975| 0.27 | 1.75 |1.87| 5,231 | 0.13 |0.13| |-----+----------+------+------+------+-------+----+--------+-------+----+ |_Ki._| 614 | 527| 1,604| 0.23 | 2.61 |3.04| 1,230 | 0.22 |0.26| | | 357 | 259| 1,234| 0.30 | 3.45 |4.76| 1,036 | 0.32 |0.44| | | 530 | 404| 1,084| 0.29 | 2.04 |2.68| 550 | 0.11 |0.15| | | 925 | 890| 1,901| 0.28 | 2.05 |2.13| 905 | 0.10 |0.11| | | 3,254 | 2,908| 4,570| 0.31 | 1.40 |1.57| 2,470 | 0.08 |0.09| | |----------+------+------+------+-------+----+--------+-------+----+ | | 5,680 | 4,988|10,393| 0.29 | 1.83 |2.08| 6,191 | 0.12 |0.14| |-----+----------+------+------+------+-------+----+--------+-------+----+ |_Ko._| 250 | 188| 471| 0.29 | 1.88 |2.50| 376 | 0.17 |0.22| | | 496 | 347| 883| 0.29 | 1.78 |2.54| 357 | 0.08 |0.11| | | 626 | 606| 1,003| 0.27 | 1.60 |1.65| 609 | 0.11 |0.11| | | 718 | 709| 2,161| 0.26 | 3.00 |3.04| 918 | 0.14 |0.14| | | 605 | 535| 2,397| 0.50 | 3.96 |4.48| 762 | 0.14 |0.16| | |----------+------+------+------+-------+----+--------+-------+----+ | | 2,695 | 2,385| 6,915| 0.32 | 2.57 |2.90| 3,022 | 0.12 |0.14| | |---------+-------+------+------+-------+----+--------+-------+----+ | |12,923 |11,649|25,283| 0.29 | 1.96 |2.17|14,444 | 0.12 |0.14| +=====+==========+======+======+======+=======+====+========+=======+====+

The work done during the 5 months when these analyzed cost figures were kept includes 280 ft. of bench and 220 ft. of heading. This excess of bench over heading causes the general average amounts per cubic yard to be too low.

[E] Actual amount of excavation.

[F] Amount of excavation paid for.

+---------+--------+--------+-----+-----+------+------+-------+ | Drilling and Firing Data for | | Each Sub-division of Section | |---------+--------+--------+-----+-----+------+------+-------| | Sub | Volume | No. of | No. | No. |Total |Linear| Total | |divisions|of each |sets of | of | of | lbs. | feet |length | | | sub- | holes |holes|times| of | of |drilled| | |division| | in |fired|powder|tunnel| | | |paid for| | set | | per |broken| | | | | | | | hole | | | | | | | | |fired | | | |---------+--------+--------+-----+-----+------+------+-------| | _a_ | _b_ | _c_ | _d_ | _e_ | _f_ | _g_ | _h_ | |---------+--------+--------+-----+-----+------+------+-------| | _A_ | 17.775 | {[G] 1 | 6 | 3 | 4.50 | | | | | | {[H] 1 | 9 | 1 | 1.50 | | | | | | {[I] 1 | 6 | 1 | 1.00 | | | | | | {[J] 1 | 6 | 1 | 0.75 | 6.0 | 195 | | | | | | | | | | |---------+--------+--------+-----+-----+------+------+-------| | _A'_ | 1.00 | 2 | 3-4 | 1 | 0.25 | 5.0 | 21 | |---------+--------+--------+-----+-----+------+------+-------| | _B_ | 5.925 | {[G] 2 | 3-4 | 1 | 1.00 | 4.0 | 35 | |---------+--------+--------+-----+-----+------+------+-------| | _C_ | | {[K] 1 | 3 | 2 | 1.125| | | | | 33.33 | 4 | 7 | 1 | 1.125| 5.0 | 186 | |---------+--------+--------+-----+-----+------+------+-------| | _D_ | 6.665 | 2 | 5-6 | 1 | 0.75 | 3.0 | 33 | |---------+--------+--------+-----+-----+------+------+-------| | | | | | | | | |=========+========+========+=====+=====+======+======+=======| | _E_ | 50.00 | | 5 | 1 | 1.50 | 5.0 | 405 | |---------+--------+--------+-----+-----+------+------+-------| | _F_ | 88.88 |{ 10.5| 4 | 2 | 1.50 | | | | | |{[L] 5.0| 4 | 1 | 1.50 | 4.0 | 682 | |---------+--------+--------+-----+-----+------+------+-------| | _G_ | 22.22 | 5.5| 4 | 2 | 1.00 | 5.0 | 132 | |---------+--------+--------+-----+-----+------+------+-------| | | | | | | | | |=========+========+========+=====+=====+======+======+=======| | _H_ | 9.77 |{ 5 | 3 | 1 | 0.50 | | | | | |{ 4 | 6 | 1 | 0.50 | 6.0 | 156 | |---------+--------+--------+-----+-----+------+------+-------| | _I_ | 26.66 | 8 | 5 | 1 | 1.00 | 6.0 | 252 | |---------+--------+--------+-----+-----+------+------+-------| | | | | | | | | | | |========+=====+=====+======+======+=======| | | | | | | | | | | | | | | |========+=====+=====+======+======+=======| | | | | +---------+--------+--------+-----+-----+------+------+-------+

+---------+------+-------+------+------+---------+-------+------+ | Drilling and Firing Data for | | Total Sections | |---------+------+-------+------+------+---------+-------+------| | Sub |Total |Length | Cu. | Cu. | Total | Total | Total| |divisions|length|drilled| yds. | yds. | lbs. of |lbs. of| lbs. | | | of | per | per | per | powder | powder| of | | |simi- |linear |linear|linear| per | per |powder| | |lar |foot of| foot | foot | linear | foot | per | | |head- |tunnel | of | of | foot of |drilled|cubic | | |ings | |tunnel|tunnel| tunnel | | yard | |---------+------+-------+------+------+---------+-------+------| | _a_ | _i_ | _j_ | _k_ | _l_ | _m_ | _n_ | _o_ | |---------+------+-------+------+------+---------+-------+------| | _A_ | |Sigma | | | | | | | | | c + d |b + i | j |c + d + f| m | m | | | | ----- |------| --- | ----- | --- | --- | | | | g | g | k | g | j | k | | | 2 | 65.00 | 5.925|10.97 | 17.00 | 0.261 |2.848 | |---------+------+-------+------+------+---------+-------+------| | _A'_ | 2 | 8.40 | 0.400|21.00 | 0.70 | 0.166 |1.750 | |---------+------+-------+------+------+---------+-------+------| | _B_ | 2 | 17.50 | 2.962| 5.90 | 3.50 | 0.200 |1.181 | |---------+------+-------+------+------+---------+-------+------| | _C_ | | | | | | | | | | 1 | 37.20 | 6.666| 5.58 | 6.975 | 0.187 |1.046 | |---------+------+-------+------+------+---------+-------+------| | _D_ | 2 | 22.00 | 4.444| 4.95 | 5.500 | 0.250 |1.237 | |---------+------+-------+------+------+---------+-------+------| |Total for| |150.10 |20.397| 7.81 | 33.675 | 0.227 |1.778 | | Heading | | | | | | | | |=========+======+=======+======+======+=========+=======+======| | _E_ | 1 | 81.00 |10.000| 8.10 | 13.500 | 0.167 |1.350 | |---------+------+-------+------+------+---------+-------+------| | _F_ | | | | | | | | | | 1 |170.50 |22.222| 7.67 | 23.230 | 0.136 |1.046 | |---------+------+-------+------+------+---------+-------+------| | _G_ | 1 | 26.40 | 4.444| 5.94 | 4.400 | 0.166 |0.990 | |---------+------+-------+------+------+---------+-------+------| |Total for| |277.90 |36.666| 7.56 | 41.150 | 0.150 |1.133 | | Bench | | | | | | | | |=========+======+=======+======+======+=========+=======+======| | _H_ | | | | | | | | | | 1 | 26.00 | 1.628|15.96 | 3.250 | 0.125 |1.995 | |---------+------+-------+------+------+---------+-------+------| | _I_ | 2 | 84.00 | 4.444|18.90 | 13.333 | 0.158 |3.000 | |---------+------+-------+------+------+---------+-------+------| |Total of | |110.00 | 6.072|18.10 | 16.583 | 0.151 |2.731 | | Trench | | | | | | | | |=========+======+=======+======+======+=========+=======+======| |Total for| |548.00 |63.135| 8.95 | 91.408 | 0.172 |1.446 | | Whole | | | | | | | | |Section | | | | | | | | |=========+======+=======+======+======+=========+=======+======| |Powder taken at 0.5 lb. per stick | +---------+------+-------+------+------+---------+-------+------+

[G] 6 Cut Holes-8 feet (Black circle)

[H] 9 First Side Rd. and Bottom-7 feet (Circle with dot in it)

[I] 6 Back Round-7 feet (Circle with line in it)

[J] 6 Top Back Round-7 feet (Circle with x in it)

[K] A' 7 Holes-3 feet (Open circle)

[L] line holes (Plus sign)

TABLE 7.--Analysis of Drilling Time on Section Gy-East.

+========+======+========+=====+=====+=======+========+========+=======+ | | | | AVERAGE TIME TAKEN: | |Position|Nature| No. of |-----+-----+-------+--------+--------+-------| | in | of | Drill | | | | | | | |Section.|Rock. | Shifts |Set- |Dril-|Neces- |Unneces-| Taking |Loading| | | |observed|ting |ling.| sary | sary | down | and | | | | for | up. | |delays.|delays. |machine.|firing.| | | |average.| | | | | | | |--------+------+--------+-----+-----+-------+--------+--------+-------| | | | |h. m.|h. m.| h. m. | h. m. | h. m. | h. m. | | | | |-----+-----+-------+--------+--------+-------| |Heading |Quartz| 8 |0:38 |4:52 | 1:40 | | 0:05 | 0:04 | | | | | | | | | | | |Heading | Hard | 1 |0:15 |8:00 | 1:45 | | | | | | mica | | | | | | | | | |schist| | | | | | | | | | | | | | | | | | | Bench |Quartz| 23 |1:23 |5:57 | 2:23 | 0:05 | 0:05 | 0:07 | | | | | | | | | | | | Bench |Medium| 16 |1:10 |6:08 | 1:50 | 0:12 | 0:07 | 0:07 | | | mica | | | | | | | | | |schist| | | | | | | | | | | | | | | | | | | Center |Medium| 10 |0:58 |5:53 | 1:33 | 0:06 | 0:12 | 0:30 | | trench | mica | | | | | | | | | |schist| | | | | | | | | | | | | | | | | | | Center | Soft | 9 |1:10 |6:40 | 1:17 | 0:10 | 0:20 | 0:23 | | trench | mica | | | | | | | | | |schist| | | | | | | | |--------+------+--------+-----+-----+-------+--------+--------+-------| |General | | 67 |1:08 |5:58 | 1:53 | 0:07 | 0:09 | 0:12 | |average | | | | | | | | | |--------+------+--------+-----+-----+-------+--------+--------+-------| | Per- | | |11.3%|59.7%| 18.9% | 1.1% | 1.5% | 2% | |centage | | | | | | | | | +========+======+========+=====+=====+=======+========+========+=======+

+========+======+=========+========+======+======+========+ | | | AVERAGE TIME TAKEN: | FEET DRILLED. | |Position|Nature|---------+--------+------+------+--------| | in | of | | | | | | |Section.|Rock. | Total |Mucking.|Total.| Per | Per | | | |drilling.| | |shift.|working | | | | | | | | hour. | | | | | | | | | |--------+------+---------+--------+------+------+--------| | | | h. m. | h. m. |h. m. | | | | | |---------+--------+------+------+--------| |Heading |Quartz| 7:19 | 2:41 |10:00 | 22.0 | 2.86 | | | | | | | | | |Heading | Hard | 10:00 | |10:00 | 42.0 | 4.20 | | | mica | | | | | | | |schist| | | | | | | | | | | | | | | Bench |Quartz| 10:00 | |10:00 | 25.9 | 2.59 | | | | | | | | | | Bench |Medium| 9:34 | 0:26 |10:00 | 22.22| 2.32 | | | mica | | | | | | | |schist| | | | | | | | | | | | | | | Center |Medium| 9:12 | 0:48 |10:00 | 22.0 | 2.39 | | trench | mica | | | | | | | |schist| | | | | | | | | | | | | | | Center | Soft | 10:00 | |10:00 | 26.44| 2.64 | | trench | mica | | | | | | | |schist| | | | | | |--------+------+---------+--------+------+------+--------| |General | | 9:27 | 0:33 |10:00 | 24.1 | 2.54 | |average | | | | | | | |--------+------+---------+--------+------+------+--------| | Per- | | 94.5% | 5.5% | 100% | | | |centage | | | | | | | +========+======+=========+========+======+======+========+

TABLE 8.--ANALYZED COST OF DRILLING.

+=============+===========================+===========================+ | | COST PER FOOT OF HOLE | COST PER DRILL SHIFT | |Item of Cost.| DRILLED. | | | +-------+-----+-----+-------+-----+------+------+-------+ | | 15 ft | 9 ft|24 ft|Average|15 ft|19 ft |24 ft |Average| | | 4 in | 6 in| 6 in| | 4 in| 6 in | 6 in | | |-------------+-------+-----+-----+-------+-----+------+------+-------+ |Drilling | $0.25 |$0.28|$0.31| $0.28 |$6.95| $7.75| $7.60| $7.45 | |labor | | | | | | | | | | | | | | | | | | | |Sharpening | 0.02 | 0.02| 0.01| 0.016| 0.58| 0.42| 0.34| 0.43 | | | | | | | | | | | |Drill steel | 0.007|0.007|0.006| 0.007| 0.19| 0.20| 0.15| 0.19 | |(5 in. per | | | | | | | | | |drill shift) | | | | | | | | | | | | | | | | | | | |Drill repairs| 0.02 | 0.02| 0.02| 0.02 | 0.61| 0.59| 0.42| 0.54 | | | | | | | | | | | |High-pressure|[M]0.05| 0.04| 0.07| 0.07 | 1.39| 1.86| 1.67| 1.82 | |air | | | | | | | | | |-------------+-------+-----+-----+-------+-----+------+------+-------+ |Totals | $0.35 |$0.38|$0.41| $0.385|$9.67|$10.82|$10.18|$10.43 | +=============+=======+=====+=====+=======+=====+======+======+=======+

[M] This is an estimated figure, ascertained by taking a proportion of the whole charge for plant running.

_General Methods._--Whenever any considerable support was needed for the ground, segmental timbering was used. In most cases, this was supported by wall-plates at the springing line, and was set with an allowance for settlement, so that it would be clear of the work when the masonry lining was put in. As the twin-tunnel section involved the excavation of the North and South Tunnels at the same time, the cross-section of the upper part of the excavation consisted of two quadrants rising from the springing line and connected at the top by a horizontal piece from 19 to 28 ft. in length. This made a rather flat arch to support by timbering.

The timber for the segmental work was 12 by 12-in. yellow pine. In light ground the bents were spaced at 5-ft. centers, in heavy ground 2-ft. 6-in. centers.

When the soft ground in the roof was struck, posts had to be used in the heading to support the caps. When the bench was removed, the posts were replaced by others down to the bottom of the excavation. These long posts were a great hindrance to all the work, and each replacement of short posts by long ones meant a settlement of the caps; consequently, it was decided to use in the section east of the cut-and-cover, where all the ground was heavy, a temporary inner bent of segmental timber, within and reinforcing the permanent bent, and resting on separate wall-plates. This is shown by Fig. 6. These temporary bents were inside the work, and were removed as the arch was built. However, the caps settled considerably in some cases, so that it was not possible to do away with posting entirely.

In heavy ground the caps were set about 1 ft. above the neat line of the crown of the brick arch, in some cases they were set only 6 in. above, but the settlement was often more than this, causing great trouble in cutting out the encroaching timber when the arch had to be built.

In the tunnels east of the cut-and-cover portion, wall-plate headings were driven (shown by areas marked _A_ on Fig. 5), and, when a length of wall-plate had been set, the full-width heading was advanced a foot or two at a time, the timber segmental bents being set up as soon as possible; lagging was then driven over the cap into the soft ground. Fig. 6 shows the double set of segmental bents adopted in the 15-ft. 4-in. twin tunnels east of the cut-and-cover section.

When the soft ground came down so low as to interfere with the excavation of the wall-plate headings, a small heading was driven into the soft ground on the line of the ends of the caps, and lagging was driven down from this to the wall-plate heading, as illustrated in Fig. 4.

In the 19-ft. 6-in. tunnels the wall-plate for the inner bent was supported by a side-bench, termed the "Raker" bench. This was left in position until the rest of the bench and the middle subgrade conduit trench had been excavated; it was then possible to support the caps by two rows of posts from subgrade level, take out the inner bents, and excavate the raker bench.

The 24-ft. 6-in. twin tunnels, which are at the extreme eastern end of this section, adjoining the open-cut work of the Terminal Station, and under Tenth Avenue, were driven from the Terminal Station-West, and the timbering had to be made very secure on account of the pipes and sewers in the street above. Detailed records were kept of the amount of timber used and the cost of labor and material expended in timbering. These records cover the same portion of tunnel as that for which the detailed records of drilling costs, previously referred to, were kept. These records are shown in Tables 9 and 10. It will be noted that the timber used in blocking, that is, filling up voids outside the main timbering, amounted to more than two-thirds of the total timber, and that the cost of labor in erecting the timbering exceeds the prime cost of the timber by about one-third. The following distinction is made between permanent and temporary timbering: The permanent timbering is that which is concreted in when the masonry is built; the temporary consists of the lower bents and posts, which have to be removed when the masonry is built.

_Force Employed in Excavation._--A typical day's working force for drilling, blasting, mucking, and timbering is shown in Table 11.

Where there was any large quantity of soft ground in the roof, the timber gang was much larger than shown in Table 11, and was helped by the mucking gang. The drillers did most of the mucking out of the heading before setting up the drills.

_Excavation of Weehawken Rock Tunnels._--This subject may be dismissed in a few words, as very few features of interest were called into play. The rock was of good quality, being the sandstone typical of this part of the country. Little or no timbering was needed, there were no buildings above the tunnel to be taken care of, and large charges of powder could be used.

TABLE 9.--SUPPLEMENTARY ANALYSIS OF TIMBERING, ROCK TUNNEL EXCAVATION UNDER 32D STREET, EAST OF CUT-AND-COVER SECTION. ANALYZED COST OF TIMBERING, PER FOOT RUN AND PER BENT.

+=============================+================================ | | _Ke_ | |--------+------------+---------- | |Per foot|Per bent, |Per cubic | |run of |3 ft, 6 in.,|yard | |tunnel |center to |excavation | | |center | |-----------------------------+--------+------------+---------- |PERMANENT TIMBERING. | | | |Lumber in feet, B. M. | | | | Upper Bent. | 274 | 685 | 7.8 | Blocking. | 294 | 735 | 8.3 | Total. | 568 | 1,420 | 16.1 |Cost, in dollars. | | | | Lumber. | 23.75| 59.38 | 0.67 | Labor. | 37.50| 93.75 | 1.06 | Total. | 61.25| 153.13 | 1.73 | | | | |TEMPORARY TIMBERING. | | | |Lumber in feet, B. M. | | | | Lower Bent. | 479 | 11.97 | 13.6 | Blocking. | 193 | 483 | 5.5 | Total. | 672 | 16.80 | 19.1 |Cost, in dollars. | | | | Lumber. | 29.13| 72.81 | 0.82 | Erection labor. | 28.85| 72.13 | 0.82 | Removal labor. | 8.29| 20.73 | 0.23 | Total labor. | 37.14| 92.86 | 1.05 | Total. | 66.27| 165.67 | 1.87 | | | | |GRAND TOTAL. | | | |Lumber in feet, B. M. |1,240 | 3,100 | 35.2 |Cost, in dollars. | | | | Lumber. | 52.88| 132.19 | 1.49 | Labor. | 74.64| 186.61 | 3.60 | Total. | 127.52| 318.80 | |-----------------------------+--------+------------+---------- | | _Ki_ | |--------+------------+---------- | |Per foot|Per bent, |Per cubic | |run of |3 ft, 6 in.,|yard | |tunnel |center to |excavation | | |center | |-----------------------------+--------+------------+---------- |PERMANENT TIMBERING. | | | |Lumber in feet, B. M. | | | | Upper Bent. | 227 | 830 | 5.3 | Blocking. | 164 | 601 | 3.8 | Total. | 391 | 1,431 | 9.1 |Cost, in dollars. | | | | Lumber. | 16.84| 61.56 | 0.39 | Labor. | 12.82| 46.88 | 0.30 | Total. | 29.66| 108.44 | 0.69 | | | | |TEMPORARY TIMBERING. | | | |Lumber in feet, B. M. | | | | Lower Bent. | 186.33| 681.25 | 4.33 | Blocking. | 42.80 156.50 | 0.99 | Total. | 229.13| 837.75 | 5.32 |Cost, in dollars. | | | | Lumber. | 9.65| 35.31 | 0.22 | Erection labor. | 10.38| 37.97 | 0.24 | Removal labor. | 9.74| 34.09 | 0.23 | Total labor. | 20.12| 72.06 | 0.47 | Total. | 29.77| 107.37 | 0.69 | | | | |GRAND TOTAL. | | | |Lumber in feet, B. M. | 6.20| 22.69 | 14.4 |Cost, in dollars. | | | | Lumber. | 26.49| 96.87 | 0.61 | Labor. | 32.94| 118.94 | 0.77 | Total. | 59.43| 215.81 | 1.38 |-----------------------------+--------+----------------------- | | _Ko_ | |--------+------------+---------- | |Per foot|Per bent, |Per cubic | |run of |3 ft, 6 in.,|yard | |tunnel |center to |excavation | | |center | |-----------------------------+--------+------------+---------- |PERMANENT TIMBERING. | | | |Lumber in feet, B. M. | | | | Upper Bent. | 261 | 962 | 4.1 | Blocking. | 408 | 1,508 | 6.5 | Total. | 669 | 24.70 | 10.5 |Cost, in dollars. | | | | Lumber. | 28.00| 103.38 | 0.44 | Labor. | 29.79| 110.00 | 0.47 | Total. | 57.79| 213.38 | 0.91 | | | | |TEMPORARY TIMBERING. | | | |Lumber in feet, B. M. | | | | Lower Bent. | 350 | 1,291 | 5.5 | Blocking. | 61 | 227 | 1.0 | Total. | 411 | 1,518 | 6.5 |Cost, in dollars. | | | | Lumber. | 18.45| 68.16 | 0.29 | Erection labor. | 20.83| 76.92 | 0.33 | Removal labor. | 12.16| 44.59 | 0.19 | Total labor. | 32.99| 121.51 | 0.52 | Total. | 51.44| 189.67 | 0.81 | | | | |GRAND TOTAL. | | | |Lumber in feet, B. M. |1,080 | 3,988 | 17.1 |Cost, in dollars. | | | | Lumber. | 46.45| 171.54 | 0.73 | Labor. | 62.78| 231.50 | 0.99 | Total. | 109.23| 403.04 | 1.72 +=============================+========+============+=========

TABLE 10.--TIMBERING:--DETAILED COST OF TIMBER, LABOR, AND SUPERINTENDENCE. ROCK TUNNEL EXCAVATION UNDER 32D STREET, EAST OF CUT-AND-COVER SECTION.

+====+=======+======================================+====================+ | | | | EXCAVATION | | | | | TIMBER USED, IN | IN CUBIC | COST OF | | | | FEET, B. M. | YARDS | TIMBER | | | |------------------------+-------------+--------------------+ | | | Main |Blocking| Total | | Paid | | | | | |Date |timber.|timber. |timber.|Actual| for. | Main |Block.|Total.| | |-------+-------+--------+-------+------+------+------+------+------+ | |1907 | _a_ | _b_ | _c_ | _d_ | _e_ | _f_ | _g_ | _h_ | | |-------+-------+--------+-------+------+------+------+------+------+ |_Ke_|May | 18,016| 15,234 | 33,250| 1,736| 1,664| $810| $565|$1,375| | |June | 14,048| 11,528 | 25,576| 809| 698| 680| 457| 1,087| | |July | 20,092| 7,339 | 27,431| 1,022| 960| 900| 300| 1,200| | |August | 6,485| 2,632 | 9,117| 743| 716| 290| 110| 400| | |Sept. | 1,632| 2,224 | 3,856| 238| 238| 73| 94| 167| | |Removal| | | | | | | | | | |-------+-------+--------+-------+------+------+------+------+------+ | |Total | 60,273| 38,957 | 99,230| 4,548| 4,276|$2,703|$1,526|$4,229| |----+-------+-------+--------+-------+------+------+------+------+------+ |_Ki_|May | | 3,537 | 3,537| 614| 527| | $150| $150| | |June | 300| | 300| 357| 259| $14| | 14| | |July | 7,776| 5,811 | 13,587| 530| 404| 350| 233| 583| | |August | 19,712| 5,702 | 25,414| 925| 890| 887| 220| 1,107| | |Sept. | 20,556| 9,218 | 29,774| 1,585| 1,501| 925| 325| 1,250| | |Removal| | | | 1,669| 1,407| | | | | |-------+-------+--------+-------+------+------+------+------+------+ | |Total | 48,344| 24,268 | 72,612| 5,680| 4,988|$2,176| $928|$3,104| |----+-------+-------+--------+-------+------+------+------+------+------+ |_Ko_|May | 4,332| 8,788 | 13,120| 250| 188| $175| $366| $561| | |June | 7,132| 10,017 | 17,149| 496| 347| 324| 396| 720| | |July | 3,070| 200 | 3,270| 626| 606| 134| 10| 144| | |August | 10,704| 2,102 | 12,806| 718| 709| 481| 80| 561| | |Sept. | 2,400| 245 | 2,645| 396| 324| 108| 8| 116| | |Removal| | | | 209| 211| | | | |----|-------+-------+--------+-------+------+------+------+------+------+ | |Total | 27,638| 21,352 |48,990 | 2,695| 2,385|$1,242| $860|$2,102| |----|-------+-------+--------+-------+------+------+------+------+------+ | |Grand |136,255| 84,577 |220,832|12,923|11,649|$6,121|$3,314|$9,435| | |total | | | | | | | | | +====+=======+=======+========+=======+======+======+======+======+======+

+====+=======+=======+=======+=======+=======+======+=======+=====+=====| | | | | | COST PER | COST PER | | | | | | CUBIC YARD | CUBIC YARD | | | |COST OF| TOTAL | (ACTUAL). | (PAID FOR). | | | | Labor | Cost. |-------+-------+------+-------+-----+-----+ | |DATE | | |Timber.|Labor. |Total.|Timber.|Labor|Total| | |-------+-------+-------+-------+-------+------+-------+-----+-----+ | | | | | _h_ | _i_ | _j_ | _h_ | _i_ | _j_ | | | | | | --- | --- | --- | --- | --- | --- | | |1907 | _i_ | _j_ | _d_ | _d_ | _d_ | _e_ | _e_ | _e_ | |----+-------+-------+-------+-------+-------+------+-------+-----+-----+ |_Ke_|May | $1,792| $3,167| $0.79 | $1.03 | $1.82| $0.82 |$1.07|$1.90| | |June | 1,576| 2,663| 1.34 | 1.95 | 3.29| 1.55 | 2.25| 3.81| | |July | 1,580| 2,780| 1.16 | 1.55 | 2.72| 1.25 | 1.64| 2.89| | |August | 300| 700| 0.53 | 0.40 | 0.94| 0.57 | 0.41| 0.98| | |Sept. | 60| 227| 0.70 | 0.25 | 0.95| 0.70 | 0.25| 0.95| | |Removal| 663| 663| | | | | | | | |-------+-------+-------+-------+-------+------+-------+-----+-----+ | |Total | $5,971|$10,200| $0.91 | $1.51 | $2.22| $1.00 |$1.40|$2.40| |----+-------+-------+-------+-------+-------+------+-------+-----+-----+ |_Ki_|May | $100| $250| $0.24 | $0.16 | $0.40| $0.28 |$0.19|$0.47| | |June | 44| 58| 0.04 | 0.12 | 0.16| 0.05 | 0.17| 0.22| | |July | 525| 7,108| 1.10 | 0.99 | 2.09| 1.44 | 1.30| 2.74| | |August | 1,018| 2,125| 1.20 | 1.10 | 2.30| 1.24 | 1.14| 2.38| | |Sept. | 1,028| 2,278| 0.79 | 0.65 | 1.44| 0.83 | 0.68| 1.51| | |Removal| 1,139| 1,139| | 0.68 | 0.68| | 0.81| 0.81| | |-------+-------+-------+-------+-------+------+-------+-----+-----+ | |Total | $3,854| $6,958| $0.55 | $0.68 | $1.23| $0.63 |$0.77|$1.40| |----+-------+-------+-------+-------+-------+------+-------+-----+-----+ |_Ko_|May | $303| $864| $2.24 | $1.21 | $3.45| $3.00 |$1.61|$4.61| | |June | 562| 1,282| 1.45 | 1.18 | 2.58| 2.07 | 1.61| 3.68| | |July | 156| 300| 0.23 | 0.25 | 0.48| 0.23 | 0.26| 0.49| | |August | 727| 1,288| 0.78 | 1.01 | 1.79| 0.80 | 1.02| 1.82| | |Sept. | 400| 516| 0.29 | 1.01 | 1.30| 0.36 | 1.23| 1.59| | |Removal| 535| 535| | 2.56 | 2.56| | 2.54| 2.54| | |-------+-------+-------+-------+-------+------+-------+-----+-----+ | |Total | $2,683| $4,785| $0.78 | $1.00 | $1.78| $0.88 |$1.12|$2.00| |----+-------+-------+-------+-------+-------+------+-------+-----+-----+ | |Grand |$12,508|$21,943| $0.73 | $0.97 | $1.70| $0.81 |$1.07|$1.88| | |total | | | | | | | | | +====+=======+=======+=======+=======+=======+======+=======+=====+=====+

+====+===========+======================+ | | | COST, PER 1,000 | | | | FT., B. M., OF | | | | TOTAL TIMBER. | | | |-------+------+-------| | | | Total | | | | | Date |timber.|Labor.|Total. | | |-----------+-------+------+-------| | | | _h_ | _i_ | _j_ | | | | --- | --- | --- | | | 1907 | _c_ | _c_ | _c_ | |----+-----------+-------+------+-------| |_Ke_|May |$41.35 |$53.89| $95.24| | |June | 42.50 | 61.62| 104.12| | |July | 43.74 | 57.60| 101.34| | |August | 43.87 | 32.90| 76.77| | |Sept. | 43.31 | 15.56| 58.87| | |Removal | | | | | |-----------+-------+------+-------| | |Total |$42.62 |$60.19|$102.81| |----+-----------+-------+------+-------| |_Ki_|May |$42.41 |$28.27| $70.68| | |June | 46.66 |146.33| 193.33| | |July | 42.91 | 38.64| 81.54| | |August | 43.56 | 40.06| 83.61| | |Sept. | 41.98 | 34.53| 76.51| | |Removal | | | | | |-----------+-------+------+-------| | |Total |$42.75 |$53.09| $95.84| |----+-----------+-------+------+-------| |_Ko_|May |$42.76 |$23.10| $65.86| | |June | 41.98 | 32.77| 74.75| | |July | 44.04 | 47.70| 91.74| | |August | 43.80 | 56.77| 100.57| | |Sept. | 43.85 |151.23| 195.08| | |Removal | | | | | |-----------+-------+------+-------| | |Total |$42.91 |$54.75| $97.65| |----+-----------+-------+------+-------| | |Grand total|$42.73 |$56.65| $99.38| +====+===========+=======+======+=======+

Work was begun on September 1st, 1904, immediately on the completion of the work on the shaft. The North and South Tunnels in this case are completely independent, as will be seen from Plate XXXIV. The procedure adopted was to drive a top heading on the center line of each tunnel and to break down the bench from this. The drilling was at first supplied with steam power from a temporary plant, as the contractor was at that time installing his permanent plant, which was finished at the end of November, 1904. At this time the rate of advance averaged 3½ lin. ft. of full section per day of 24 hours. By the end of January the Weehawken rock tunnels were completely excavated, and by the middle of April, 1905, the excavation for the shield chambers was finished; the erection of the shields was started at the end of that month.

TABLE 11.

==================+=========+========+=============+========+========== Grade. |Total No.|Rate per|Drilling and |Mucking:|Timbering: | | day. |blasting: No.| No. | No. ------------------+---------+--------+-------------+--------+---------- Superintendent | 1 | $7.70 | ½ | 1/8 | 3/8 Assistant engineer| 1 | 5.80 | ½ | 1/8 | 3/8 Electrician | 1 | 3.50 | ½ | 1/8 | 3/8 Engineer | 1 | 3.50 | | 1 | Signalman | 1 | 2.00 | | 1 | Foreman | 3 | 4.00 | 1 | 1 | 1 Driller | 5 | 3.00 | 5 | | Driller's helper | 5 | 2.00 | 5 | | Laborers | 14 | 2.00 | | 14 | Timbermen | 3 | 3.00 | | | 3 " helpers | 4 | 2.00 | | | 4 Machinist | 1 | 4.00 | 1 | | Blacksmith | 2 | 3.50 | 2 | | " helper | 2 | 2.00 | 2 | | Nipper | 2 | 2.00 | 2 | | Waterboy | 1 | 2.00 | 1 | | ------------------+---------+--------+-------------+--------+--------- Total | 47 | | 20½ | 17-3/8 | 9-1/8 ==================+=========+========+=============+========+=========

The general scheme of excavation is shown by Plate XXXIII. The bench was kept 50 or 60 ft. behind the face of the heading. The powder used was 60% Forcite. The general system of drilling was as shown in Fig. 7. The average length of hole drilled per cubic yard of excavation was 2.9 ft., as against 7.70 ft. at Manhattan; and the amount of powder used was 1.96 lb. per cu. yd., as against 1.24 lb. at Manhattan. There was little timbering. A length of about 30 or 40 ft. adjoining the Weehawken shaft was timbered, and also a shattered seam of about 17 ft. in width between Stations 262 + 10 and 262 + 27.

The two entirely separate tunnels gave a cross-section which was much more easily timbered than the wide flat span at Manhattan, and the segmental timbering was amply strong without posts or other reinforcement.

Table 12 is a summary of the cost of excavating the Land Tunnels, based on actual records carefully kept throughout the work.

TABLE 12.--COST OF EXCAVATION OF LAND TUNNELS, IN DOLLARS PER CUBIC YARD.

======================================+=========+=========+============= | | |Total yardage | | | and |Manhattan|Weehawken|average cost. --------------------------------------+---------+---------+------------- Cubic yards excavated |43,289 | 8,311 | 51,600 _Labor._ | | | Surface transport | $0.49| $0.87| $0.55 Drilling and blasting | 2.37| 1.55| 2.24 Mucking | 2.49| 2.08| 2.42 Timbering | 0.87| 0.18| 0.76 --------------------------------------+---------+---------+------------- Total labor | $6.22| $4.68| $5.97 --------------------------------------+---------+---------+------------- _Material._ | | | Drilling | $0.15| $0.15| $0.15 Blasting | 0.21| 0.21| 0.21 Timber | 0.39| 0.20| 0.36 --------------------------------------+---------+---------+------------- Total material | $0.75| $0.56| $0.72 --------------------------------------+---------+---------+------------- Plant running | $0.76| $0.65| $0.74 Surface labor, repairs and maintenance| 0.15| 0.08| 0.14 Field office administration | 1.05| 1.18| 1.07 --------------------------------------+---------+---------+------------- Total field charges | $8.96| $7.15| $8.64 --------------------------------------+---------+---------+------------- Chief office administration | $0.34| $0.38| $0.34 Plant depreciation | 0.66| 1.01| 0.72 Street and building repairs | 0.27| | 0.23 --------------------------------------+---------+---------+------------- Total average cost per cubic yard | $10.23| $8.54| $9.93 ======================================+=========+=========+=============

Masonry Lining of Land Tunnels.

Plates XXXII and XXXIV show in detail the tunnels as they were actually built. It will be seen that in all work, except in the Gy-East contract, there was a bench at each side of each tunnel in which the cable conduits were embedded. In Gy-East the bank of ducts which came next to the middle wall was carried below subgrade, and the inner benches were omitted.

The side-walls and subgrade electric conduits were water-proofed with felt and pitch. The water-proofing was placed on the outside of the side-walls (that is, on the neat line), and the space between the rock and the water-proofing was filled with concrete. This concrete was called the "Sand-Wall."

The general sequence of building the masonry lining is shown in Fig. 8. The operations were as follows:

1.--Laying concrete for the whole height of the
sand-walls, and for the floor and foundations for
walls and benches up to the level of the base of
the conduits;

2.--Water-proofing the side-walls, and, where there was
a middle trench containing subgrade conduits,
laying and water-proofing these conduits;

3.--Building concrete wall for conduits to be laid
against, and, where there was a middle trench,
filling up with concrete between the conduits;

4.--Laying conduits;

5.--Laying concrete for benches and middle-wall;

6.--Building haunches from top of bench to springing of
brick arch;

7.--Building brick arch and part of concrete
back-filling;

8.--Finishing back-filling.

The whole work will be generally described under the headings of Concrete, Brickwork, Water-proofing, and Electric Conduits.

_Concrete._--The number of types and the obstructions caused by the heavy posting of the timbering made it inadvisable to use built-up traveling forms at the Manhattan side, though they were used in the Weehawken Rock Tunnels.

The specifications required a facing mixture of mortar to be deposited against the forms simultaneously with the placing of the concrete. This facing mixture was dry, about 2 in. thick, and was kept separate from the concrete during the placing by a steel diaphragm. The diaphragm was removed when the concrete reached the top of each successive layer, and the facing mixture and concrete were then tamped down together. This method was at first followed and gave good results, which was indeed a foregone conclusion, as the Weehawken shaft had been built in this way. However, it was found that as good results, in the way of smooth finish, were to be obtained without the facing mixture by spading the concrete back from the forms, so that the stone was forced back and the finer portion of the mixture came against the forms; this method was followed for the rest of the work. All corners were rounded off on a 1-in. radius by mouldings tacked to the forms. The side-bench forms were used about four times, and were carefully scraped, planed, filled at open joints, and oiled with soap grease each time they were set up. When too rough for face work they were used for sand-wall and other rough work.

The mixing was done by a No. 4 Ransome mixer, driven by 30-h.p. electric motors. The mixer at Manhattan was set on an elevated platform at the north end of the intercepting arch; that at Weehawken was placed at the entrance to the tunnels. The sand and stone were stored in bins above the mixers, and were led to the hoppers of the mixers through chutes. The hoppers were divided into two sections, which gave the correct quantities of sand and stone, respectively, for one batch. The water was measured in a small tank alongside. A "four-bag" batch was the amount mixed at one time, that is, it consisted of 4 bags of cement, 8¾ cu. ft. of sand, and 17½ cu. ft. of broken stone, and was called a 1 : 2½ : 5 mixture. It measured when mixed about ¾ cu. yd.

The cement was furnished to the contractor by the Railroad Company, which undertook all the purchasing from the manufacturer, as well as the sampling, testing, and storing until the contractor needed it. The Railroad Company charged the contractor $2 a barrel for this material.

The sand was required by the specifications to be coarse, sharp, and silicious, and to contain not more than 0.5% of mica, loam, dirt, or clay. All sand was carefully tested before being used. The stone was to be a sound trap or limestone, passing a 1½-in. mesh and being retained on 3/8-in. mesh. The contractor was allowed to use a coarser stone than this, namely, one that had passed a 2-in. and was retained on a 1½-in. mesh.

The concrete was to be machine-mixed, except in cases of local necessity. The quantity of water used in the mixture was to be such that the concrete would quake on being deposited, but the engineer was to use his discretion on this point. Concrete was to be deposited in such a manner that the aggregates would not separate. It was to be laid in layers, not exceeding 9 in. in thickness, and thoroughly rammed. When placing was suspended, a joint was to be formed in a manner satisfactory to the engineer. Before depositing fresh concrete, the entire surface on which it was to be laid was to be cleaned, washed and brushed, and slushed over with neat cement grout. Concrete which had begun to set was not to be used, and retempering was not to be allowed.

The forms were to be substantial and hold their shape until the concrete had set. The face forms were to be of matched and dressed planking, finished to true lines and surfaces; adequate measures were to be taken to prevent concrete from adhering to the forms. Warped or distorted forms were to be replaced. Plastering the face was not allowed. Rock surfaces were to be thoroughly washed and cleaned before the concrete was deposited.

These specifications were followed quite closely.

A typical working gang, as divided among the various operations, is shown below:

_Superintendence._
½ Superintendent @ $250 per month
½ Assistant engineer " 150 " "
1 Assistant superintendent " 150 " "
_Surface Transport._
1 Foreman @ $2.50 per day
1 Engineer " 3.00 " "
1 Signalman " 2.00 " "
16 Laborers " 1.75 " "
3 Teams " 7.50 " "
_Laying._
1 Foreman @ $4.00 per day
8 Laborers " 2.00 " "
_Forms._
1 Foreman @ $4.50 per day
4 Carpenters " 3.25 " "
5 Helpers " 2.25 " "
_Tunnel Transport._
¼ Foreman @ $3.25 per day
¼ Engineer " 3.00 " "
¼ Signalman " 2.00 " "
4 Laborers " 1.75 " "
_Mixers._
¼ Foreman @ $3.25 per day
2 Laborers " 1.75 " "

The superintendent and assistant engineer looked after the brickwork and other work as well as the concrete. The surface transport gang handled all the materials on the surface, including the fetching of the cement from the cement warehouses.

The tunnel transport gang handled all materials in the tunnel, but, when the haul became too long, the gang was reinforced with laborers from the laying gang. Of the laying gang, two generally did the spading, two the spreading and tamping, and the remaining force dumped the concrete. The general cost of this part of the work is shown in Table 13.

The figures in Table 13 include the various items built into the concrete and some that are certificate extras in connection with the concrete, such as drains, ironwork and iron materials, rods and bars, expanded metal, doors, frames and fittings, etc.

_Water-proofing._--According to the specifications, the water-proofing was to consist of seven layers of pitch and six layers of felt on the side-walls and a ½-in. layer of mastic, composed of coal-tar and Portland cement, to be plastered over the outside of the arches.

By the time the work was in hand, some distrust had arisen as to the efficiency of this mastic coating, and a great deal of study was devoted to the problem of how to apply a felt and pitch water-proofing to the arches. The difficulty was that there was no room between the rock and the arch or between the timber and the arch (as the case might be) in which to work. Several ingenious schemes of putting the felt on in layers, or in small pieces like shingles, were proposed and discussed, and a full-sized model of the tunnel arch was even built on which to try experiments, but it was finally decided to overcome the difficulty by leaving out the arch water-proofing altogether, and simply building in pipes for grouting through under pressure, in case it was found that the arch was wet.

As to the arch built through the length excavated by cut-and-cover on the New York side, it was resolved to water-proof that with felt and pitch exactly as the side-walls were done, the spandrel filling between the arches being raised in a slight ridge along the concrete line between tunnels in order to throw the water over to the sides. The portions of arch not water-proofed were rather wet, and grouting with a 1:1 mixture was done, but only with the effect of stopping large local leaks and distributing a general dampness over the whole surface of the arch.

TABLE 13.--COST OF CONCRETE IN LAND TUNNELS, IN DOLLARS PER CUBIC YARD.

=======================================+==========+==========+========== | | | Total |Manhattan.|Weehawken.| yardage. ---------------------------------------+----------+----------+---------- Cubic yards placed |14,706½ | 3,723 |18,429½ ---------------------------------------+----------+----------+---------- LABOR. | Average Cost per Cubic Yard. ---------------------------------------+----------+----------+---------- Surface transport | $0.31 | $1.43 | $0.54 Superintendence and general labor at | | | point of work | 0.31 | 1.31 | 0.51 Mixing | 0.52 | 0.56 | 0.53 Laying | 1.38 | 1.45 | 1.39 Tunnel transport | 1.30 | 1.47 | 1.34 Cleaning | 0.21 | | 0.17 Forms: erecting and removal | 1.58 | 1.51 | 1.56 ---------------------------------------+----------+----------+---------- Total labor | $5.61 | $7.73 | $6.04 ---------------------------------------+----------+----------+---------- MATERIAL. ---------------------------------------+----------+----------+---------- Cement | $2.30 | $2.22 | $2.28 Sand | 0.34 | 0.40 | 0.36 Stone | 0.91 | 0.61 | 0.85 Lumber for forms | 0.47 | 0.45 | 0.47 Sundry tunnel supplies | 0.16 | 0.17 | 0.16 ---------------------------------------+----------+----------+---------- Total materials | $4.18 | $3.85 | $4.12 ---------------------------------------+----------+----------+---------- Plant running | $0.44 | $0.44 | $0.44 Surface labor, repairs and maintenance | 0.25 | 1.24 | 0.44 Field office administration | 0.50 | 1.72 | 0.75 ---------------------------------------+----------+----------+---------- Total field charges | $10.98 | $14.98 | $11.79 ---------------------------------------+----------+----------+---------- Plant depreciation | $0.62 | $1.57 | $0.81 Chief office administration | 0.24 | 0.31 | 0.25 ---------------------------------------+----------+----------+---------- Total average cost per cubic yard | $11.84 | $16.86 | $12.85 ---------------------------------------+----------+----------+---------- Cost of Miscellaneous Items in Concrete. ---------------------------------------+----------+----------+---------- |Manhattan.|Weehawken.| Average. Cubic yards |14,706½ | 3,723 |18,429½ Amount, in dollars |$6,184.83 | $1,756.79|$7,941.62 Unit cost | 0.42 | 0.47| 0.43 =======================================+==========+==========+==========

The 24-ft. 6-in. tunnel adjoining the Terminal Station-West was water-proofed by a surface-rendering method which, up to the present time, has been satisfactory. Generally speaking, the arches of the Land Tunnels, though not dripping with water, are the dampest parts of the whole structure from Tenth Avenue to Weehawken, and it would seem as if some form of water-proofing over these arches would have been a distinct advantage.