(A) Unless otherwise required by the Engineer, when main sewer pipe cannot be installed by open cut methods, it must be installed in a casing as shown on the plans.
(B) The pipe casing size, material and thickness will be as specified on the plans.
(C) The casing material will be delivered to the job site with ends fabricated to a true right angle with the axis of the pipe to facilitate accuracy of jacking.
(D) Welded steel pipe casing shall conform to ASTM Designation A-53 Grade B, A-139 grade B or A-252 Grade 2.
(E) Where approved by the Engineer, four-inch and six-inch pipes can be bored. Larger diameters require casing. The minimum inside diameter of the pipe casing shall be eight inches greater than the maximum outside diameter of the sewer to be installed therein, with a minimum outside diameter of 30 inches for any casing unless otherwise approved by the Engineer.
(F) The casing sections shall be joined by a continuous watertight weld.
(G) The jacking pits shall be excavated and backfilled in accordance with §§ 33.175, 33.176 and 33.190 through 33.194, respectively. A submittal for, and inspection of, the jacking pit installation shall be required prior to the start of the jacking operation.
(H) The guide rails for the jacking machine shall be accurately set and checked by a licensed surveyor, so that the casing, while being jacked, will be guided to correct line and grade to enable the sewer pipe to be centered in the casing.
(I) The front of the casing pipe shall be provided with mechanical arrangements or devices that will positively prevent the auger from leading the pipe so that no unsupported excavation is ahead of the pipe. The auger and cutting head arrangement shall be recessed to prevent the flowing of material from the face of the casing into the casing. The auger and cutting head arrangement shall be removable from within the pipe in the event an obstruction is encountered.
(J) The contractor shall be responsible for surface subsidence and damage or disturbance to adjacent property and facilities that may result from the contractor’s construction method. In the event that loose material is encountered, and cave-ins occur or are anticipated, all jacking will be discontinued. Approved shoring shall be provided, and all voids filled by pressure grouting.
(K) It is recommended that the contractor make frequent checks on the casing grade during installation. Grade stakes indicating pipe invert elevations shall be located at both ends of proposed casing.
(L) Voids created between the outside of the casing wall and surrounding earth shall be filled with grout or sand.
(M) When the casing has been completed and before the sewer is installed, the casing shall be inspected and approved by the Engineer. Pipe material as shown on the plans shall then be joined and installed on proper grade through the casing.
(N) The sewer pipe shall be securely supported through the casing as shown on the standard plans. After the sewer pipe is installed, it shall be given a preliminary air test in the presence of the Engineer (see §§ 33.220 through 33.224), and internally inspected by closed circuit television (see § 33.235). After the test is satisfactorily completed and the television inspection favorably reviewed, the annular space between the pipe and the casing shall be filled with dry sand mechanically blown in or filled with grout so as to completely fill all voids, after which the space between the end of the casing and the pipe shall be sealed to a watertight condition. The pipe shall be anchored and secured to prevent movement during the filling of the annular space.
(Ord. 2019-02, passed 4-25-2019)