SECT. 21.2 The stone to be used under Item 21 shall be Materials and general clean, sound stone from the tunnel or elsewhere, not smaller methods. than 4 inches in any diameter, except where thin stones may be required for wedging. Special care shall be taken to exclude all mud, stone chips or other fine material, and the stones shall be washed, if required. Unless the Engineer shall especially direct a more open packing with the idea of permitting easy filling with grout, the packing shall be placed so as to fill as completely as possible, all voids over the tunnel arch or elsewhere. In any case, the packing shall be wedged tightly and, over roof support, evenly so as to prevent distorting the support and throwing it out of line.

dry packing.

SECT. 21.3 Suitable stops of wood or other acceptable Wood stops for material shall be inserted in tunnel of Types C3 and D3 at the bottom of the space to be dry packed. These stops shall have sufficient strength and shall be so securely wedged as to prevent any settlement of the dry packing placed upon them. The stops, if of wood, shall consist of slats not exceeding 4 inches in width and of such thickness as may be required. These slats shall be placed with open joints, and if of wood shall not occupy more than 8 inches in any 2 feet measured along the tunnel.

at cut-off walls

SECT. 21.4 In supported tunnel adjacent to grouting cut- Special work off walls specified under Sections 17.19 and 17.20, the Con- and pipes. tractor shall terminate the dry packing in vertical walls. Certain weeper pipes and grouting pipes, furnished and placed under Item 28, are to be built into the dry packing, and shall be properly surrounded with dry packing in such a way as not to stop their outer ends. Typical arrangements of cut-off walls and pipes are shown on Sheet 29.

and payment.

SECT. 21.5 The quantity to be paid for under Item 21 Measurement shall be the number of cubic yards of dry packing measured in the tunnel as extending from the upper surface of the concrete, as defined in Section 17.26, to the "B line" (see Section 43), and in supported ground to the stops on either side. No deductions will be made for steel roof support. The stops will be considered as having been included in the price stipulated for Item 21, and no allowance will be made for them under other items or otherwise.

Work included.

Description of drainage interlining.

Furring.

Erection.

DRAINAGE INTERLINING IN SECTION VALVE

SHAFTS

Item 22

SECT. 22.I Under Item 22 the Contractor shall furnish all materials and construct a drainage interlining between the outer and inner concrete linings of each section valve shaft including the enlarged chamber at the bottom. The work to be done shall include all required precautions to prevent the clogging of the drainage channels, and the thorough cleaning out of the horizontal header channels, and clean-out and discharge openings at the top and bottom of the enlarged chamber at the foot of the shaft.

SECT. 22.2

Unless an acceptable alternative construction be permitted, the drainage interlining shall be constructed in accordance with that one which is ordered of the two methods hereinafter described. In both of these methods the interlining consists of a lining of burned clay furring blocks, so laid as to form continuous vertical channels against the inner surface of the outer concrete shaft lining, as shown on Sheets 22, 27 and 28. The inside of this lining is to be covered or otherwise. so made tight as to prevent the mortar from the concrete of the inner lining leaking through the joints of the furring blocks and obstructing the channels.

SECT. 22.3 The furring shall consist of specially molded. terra-cotta wall furring or tile of the dimensions shown on Sheet 28. The material shall be of the best quality of hardburned fire-clay terra-cotta equal to the dense terra-cotta wall furring manufactured by the National Fireproofing Company. The tile shall be true to shape, the ends cut truly square with the length of the tile. No split, cracked or warped tile shall be used. The tile shall be free from fins, burrs or other projections either such as would obstruct the waterway, interfere with good bearings or break through the felt and permit leaks of grout.

SECT. 22.4 The furring blocks shall be erected in close. contact with the outer concrete shaft lining and in successive

complete rings. When the blocks of each ring are in place, the whole ring shall be keyed and wedged tight by suitable wooden or other wedges cut off flush with the surface of the blocks. In erecting these blocks great care shall be taken to maintain the channels continuous and without offset from the bottom to the top of the shaft, and all necessary precautions shall be observed to prevent material of any kind falling into the channels. In one method the blocks are to be laid dry and in the other method the blocks are to be laid with thin joints of stiff cement and lime mortar to improve the strength of the lining in supporting its own weight and at the same time close the joints against the mortar from the inner lining of shaft. Joints shall be carefully pointed. If mortar is used, a mandrel shall be kept constantly in each vertical passage to positively prevent any considerable projection of mortar within the passages. These mandrels shall be of ample length and shall be raised as the lining progresses.

for furring

SECT. 22.5 To prevent the mortar from the concrete of Waterproofing the inner lining leaking into the channels in the method in laid dry. which the furring blocks are laid dry, the blocks shall be faced on the inside with one thickness of acceptable waterproof asphalt or coal-tar felt equal in all respects to the "Hydrex waterproof felt manufactured by the Hydrex Felt & Engineering Company. This felt shall be applied in horizontal strips and, except as otherwise permitted or required, shall have not more than two vertical joints in each ring. The felt shall be secured in place, in close contact with the furring blocks, by means of a sufficient number of the brass clips shown on Sheet 28, or other acceptable devices. Circumferential joints shall be given a lap of at least 4 inches, and vertical joints shall be given a lap of at least 12 inches. The two thicknesses of felt at these joints shall then be sealed or welded together by heating and pressing with suitably shaped tools heated by electricity. This heating and pressing shall be continued until all parts of the joints are substantially water-tight. The electric tools used shall be so constructed and the current supplied so governed as to produce a surface heat of about 300° F. when in use, but not produce a temperature sufficient to set fire to the felt if allowed to remain upon it indefinitely.

Time of construction.

Intermediate supports for interlining.

Measurement and payment.

Work included,

Quality of materials.

An abundant supply of water, with buckets, hose or other effective means for applying it, shall always be maintained at any place where such work is in progress, in order that any fire may be promptly extinguished.

SECT. 22.6 The drainage interlining shall be constructed in short lengths and immediately in advance of, or simultaneously with, the inner concrete shaft lining. It shall, in no case, be constructed until after the grouting of the outer shaft lining and of the surrounding rock shall have been completed. (See also Section 17.13.)

SECT. 22.7 One or more sets of bronze brackets may be ordered under Item 49 to be set in the concrete of the outer lining as supports for the tile interlining, thus permitting several shorter columns of tile to be substituted for one long column.

SECT. 22.8 For each square foot of drainage interlining, measured to the lines ordered, at the surface of contact with the inner masonry lining, the Contractor shall be paid the price stipulated for Item 22.

STEEL INTERLINING IN RISERS AND TUNNEL

Items 23 and 24

SECT. 23.1 Under Item 23 the Contractor shall furnish and erect steel interlining in the risers of all shafts, substantially as shown on Sheets 22 to 27; and under Item 24, steel interlining in the tunnel and at the section valves, Shafts 13 and 18, substantially as shown on Sheet 28. The work to be done shall include all transportation, storage, protection from rust, erection and calking.

SECT. 23.2 The structural shapes, the plates and the rivets for the fabrication of the steel interlining, shall fulfill all the requirements for structural steel, flange steel and extra soft steel, respectively, of the Standard Specifications for Structural Steel for Bridges, and for Open-Hearth Boiler Plate and Rivet Steel, adopted by the American Society for Testing Materials, August 16, 1909.

SECT. 23.3 Unless otherwise ordered or allowed, the in- Manufacture. terlining in risers shall be built up in the shop in lengths of about 15 feet. The thickness of any part shall not be less than 5/16 inch nor more than 1⁄2 inch. If ordered, the top section, which aids in anchoring the shaft cap, shall be longer to avoid stress on a flange joint, and angles may also be required on the outside of this section to aid in gripping the shaft concrete. All parts of the interlining shall be accurately formed to the shape and dimensions shown on approved working drawings. Flange angles shall be truly straight or bent accurately to the curves required, and the faces which will come in contact with the flanges of adjacent lengths or panels when erected shall be truly plane and free from burrs due to punching, or other irregularities which would prevent close fitting and the making of water-tight joints. The work shall be accurately laid out, and all rivet holes spaced with precision. Only slight drifting of rivet holes will be permitted.

SECT. 23.4 All shop riveting shall be done by steam, com- Riveting. pressed air or hydraulic machinery exerting a pressure of not less than 40 tons on the rivet. Field riveting shall be done by suitable hydraulic or pneumatic tools. Before any rivets are driven, the parts to be united shall be perfectly clean and shall be brought into close contact by suitably applied pressure, which shall be maintained until the rivets are driven.

SECT. 23.5 The edge of each plate shall be properly bev- Calking. eled for calking all around. All shop seams and all joints between plates and angles shall be shop calked, both inside and outside. Field joints of riser interlining shall be made water-tight by the use of an approved metallic gasket. If necessary at the corners of panels or elsewhere in the interlining at the section valves, soft steel or wrought iron wedges shall be driven into the joints to better insure water tightness.

protection

SECT. 23.6 During fabrication, all steel plates at each Cleaning and joint where one plate covers another, shall be entirely free from rust. from mill scale, from any but light rust and from all dirt, grease, or other foreign matter. Furthermore, when concrete