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Jacking and Boring Pipe Policy

Item No. 501

Jacking or Boring Pipe

501.1 Description

This item shall govern furnishing and installing of encasement pipe by methods of jacking or boring as indicated on the Drawings and in conformity with this specification.  This item shall also include, but not be limited to other constructions activities such as traffic control measures, excavation, removal of all materials encountered in jacking or boring pipe operations, disposal of all material not required in the work, grouting, bulkhead installation, backfilling and re-vegetation.

501.2  Submittals

The submittal requirements for this specification item shall include:

A. Shop drawings identifying proposed jacking or boring method complete in assembled position

B. Trench Safety Plan including pits, trenches and sheeting or bracing if necessary,

C.  Design for jacking or boring head,

D.  Installation of jacking or boring supports or back stop,

E.  Arrangement and position of jacks and pipe guides, and

F.  Grouting plan,

501.3 Materials

A.  Pipe Carrier pipe and encasement pipe shall conform to Standard Specification Item Nos. 505, “Concrete Encasement and Encasement Pipe” and 510, “Pipe” and shall be size, type materials, thickness and class indicated on the Drawings, unless otherwise specified.

B.  Grout Grout for void areas shall consist of 1 part Portland cement and 4 parts fine, clean sand mixed with water. 

501.4  Construction Methods

A.  General The Contractor is responsible for:

1.     Adequacy of jacking and boring operations,

2.     Installation of support systems as indicated on the Drawings,

3.     Provision of encasement and carrier pipe, and     

4.     Execution of work involving the jacking operation, the wet or dry method of boring and the installation of encasement pipe simultaneously.  The Contractor shall have sole responsibility for the safety of the jacking and boring operations and for persons engaged in the work.  The Contractor’s attention is directed to the Construction Industry Occupational Safety and Health Administration (OSHA) Standards (29 FR 1926/1920) as published in U.S. Department of Labor publication OSHA 2207, latest revision, with particular attention to Subpart S.  The Contractor shall conform to the requirements in accordance with Standard Specification Item 509, “Trench Safety System” and shall provide an appropriate Trench Safety Plan. When the grade of the pipe at the jacking or boring end is below the ground surface, suitable pits or trenches shall be excavated to provide sufficient room to conduct the jacking or boring operations and for placement of end joints of the pipe.  In order to provide a safe and stable work area, the excavated area shall be securely sheeted and braced to prevent earth caving in accordance with the Trench Safety Plan. The location of the work pit and associated traffic control measures required for the jacking or boring operations shall conform to the requirements of the City of New Braunfels and TxDoT Manual on Uniform Traffic Control Devices. Where installation of pipe is required under railroad embankments, highways, streets, or other facilities by jacking or boring methods, construction shall be undertaken in such a manner that it will not interfere with operation of any railroad, street, highway, utility or other facility and shall not weaken or damage any embankment or structure.  All appropriate permits shall be acquired prior to the initiation of the work. During construction operations, and until the work pits are backfilled and fill material compacted, traffic barricades and warning lights to safeguard traffic and pedestrians shall be furnished and maintained by the Contractor.  The Contractor shall submit the proposed pit location and traffic control plan for review by the Engineer or designated representative.  The Review by the Engineer or designated representative, however, will not relieve the Contractor from his responsibility to obtain specified results in a safe, workmanlike manner. When grade of pipe at jacking or boring end is below ground surface, suitable pits or trenches shall be excavated for the purpose of conducting the jacking or boring operations and for joining pipe.  Work shall be securely sheeted and braced as indicated on theTrench Safety Plan to prevent earth caving and to provide a safe and stable work area.  The pipe shall be jacked or bored from the low or downstream end, if possible.  Minor lateral or vertical variation in the final position of pipe from line and grade established by Engineer or designated representative will be permitted at the discretion of Engineer or designated representative provided that such variation is regular and occurs only in one direction and that the final grade of the flow line conforms to the specified direction. When conforming to details indicated on the drawings, but the bottom of the work pit is unstable or excessively wet or the installation of water and wastewater pipe will result in less than 30 inches of cover, the Contractor shall notify the Engineer or designated representative.  The Engineer or designated representative may require the Contractor to install a concrete seal, cradle, cap or encasement or other appropriate action.  Immediately after jacking or boring is complete and the encasement pipe is accurately positioned and approved for line and grade, the clear space between the pipe and the surrounding excavated material shall be completely filled by pressure grouting for entire length of installation. After placement of the carrier pipe is complete, the ends of the encasement pipe shall be bulkheaded with brick, concrete blocks or stones of sufficient mass to prevent the intrusion of backfill, etc. into the encasement pipe.  The bulkhead shall also be provided with sufficient number and placement of weep holes to facilitate the escape of the contents of carrier pipe should failure occur. As soon as possible after the carrier pipe(s) and bulkheads are completed, the work pits or trenches, which are excavated to facilitate these operations, shall be backfilled.  The backfill in the street ROW shall be compacted to not less than 95 percent of the maximum density conforming to TxDOT Test Method Tex-114-E, “Laboratory Compaction Characteristics & Moisture-Density Relationship of Subgrade & Embankment Soil”.  Field density measurements will be made in accordance with TxDOT Test Method Tex-115-E, “Field Method for Determination of In-Place Density of Soils and Base Materials”. 

B. Jacking

Heavy duty jacks suitable for forcing the pipe through the embankment shall be provided.  In operating the jacks, an even pressure shall be applied to all jacks used so that the pressure will be applied to the pipe uniformly around the ring of the pipe.  A suitable jacking frame or back stop shall be provided.  The pipe to be jacked shall be set on guides properly braced together, to support the section of the pipe and to direct it in the proper line and grade.  The complete jacking assembly shall be placed in order to line up with the direction and grade of the pipe.  In general, the embankment material shall be excavated just ahead of the pipe, the material removed through the pipe and the pipe forced through embankment by jacking, into the space thus provided. The excavation for the underside of the pipe, for at least 1/3 of the circumference of the pipe, shall conform to the contour and grade of the pipe.  A clearance of no more than 2 inches may be provided for the upper half of the pipe.  This clearance shall be tapered to zero at the point where excavation conforms to contour of pipe. The distance that excavation shall extend beyond the end of the pipe depends on the character of material encountered, but it shall not exceed 2 feet in any case.  This distance shall be decreased, when directed by the Engineer or designated representative, if the character of the material being excavated makes it desirable to keep the advance closer to the end of the pipe. The Contractor may use a cutting edge of steel plate around head end of the pipe extending a short distance beyond the end of pipe with inside angles or lugs to keep cutting edge from slipping back onto the pipe. When jacking of the pipe is begun, all operations shall be carried on without interruption, insofar as practical, to prevent the pipe from becoming firmly set in the embankment. Any pipe damaged in jacking operations shall be removed and replaced by the Contractor at its entire expense.C.  BoringThe boring shall proceed from a work pit provided for the boring equipment and workmen.  Excavation for the work pits and the installation of shoring shall be as outlined in the Trench Safety Plan.  The location of the pit shall be approved by the Engineer or designated representative.  The boring shall be done mechanically using either a pilot hole or the augur method.  In the pilot hole method an approximate 2 inch pilot hole shall be bored the entire length of the crossing and shall be checked for line and grade on the opposite end of the bore from the work pit.  This pilot hole shall serve as the centerline of the larger diameter hole to be bored. When the augur method is used, a steel encasement pipe of the appropriate diameter equipped with a cutter head to mechanically perform the excavation shall be used.  Augurs shall be of sufficient diameter to convey the excavated material to the work pit. Excavated material will be removed from the working pit and disposed of properly.  The use of water or other fluids in connection with the boring operation will be permitted only to the extent to lubricate cuttings.  Water jetting will not be permitted. In unstable soil formations, a gel-forming colloidal drilling fluid, that consists of at least 10 percent of high grade carefully processed bentonite, may be used to consolidate the drill cuttings, seal the walls of the hole and furnish lubrication to facilitate removal of the cuttings from the bore.  D.  JointsIf reinforced concrete pipe is used, the joints shall be in accordance with TxDOT Specification Item 464, “Reinforced Concrete Pipe”.

501.5  Measurement

Jacking or boring pipe will be measured by the linear foot of pipe complete in place.  Such measurement will be made between the ends of the pipe along the central axis as installed.

501.6  Payment

The work performed and materials furnished as prescribed by this item and measured as provided under “Measurement” will be paid for at the unit bid price per linear foot for “Jacking or Boring Pipe” as the case may be, of type, size and class of encasement pipe indicated on the Drawings.  The price shall include full compensation for furnishing, preparing, hauling and installing required materials, encasement pipe, bulkhead, for grouting and for labor, tools, equipment and incidentals necessary to complete work, including excavation, backfilling and disposal of surplus material. The Carrier pipe shall be paid at the unit price bid for Standard Specification Item 510, “Pipe”. Payment when included as a contract pay item, will be made under one of the following: 

Pay Item:                          Jacking or Boring __ In. Pipe, Class ___ Per Linear Foot. 

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