TRENCHLESS CONSTRUCTION
(BORING, JACKING, AND TUNNELING)

1.01 SECTION INCLUDES

A. Trenchless installation of carrier pipe with casing pipe.

B. Trenchless installation of carrier pipe without casing pipe.

1.02 DESCRIPTION OF WORK

A. Excavate launch and receiving pits.

B. Install casing pipe.

C. Install carrier pipe.

D. Backfill excavations.

E. Reference is made to the Iowa Department of Transportation Standard Specifications for Highway and Bridge Construction, Series 2001, and all current General Supplemental Specifications and Materials Instructional Memorandum by the term "Iowa DOT Specifications " and/or "Iowa DOT I.M.".

F. Possible methods of trenchless installation (refer to Section 3020, 3.05 for restrictions);

1. Auger Boring: A boring method that utilizes a rotating cutting head to form the bore and a series of rotating augers inside a casing pipe to remove the spoil.

2. Compaction Method: Boring methods that displace soil radially rather than removing spoil. Bore hole may be formed with a push rod or impact mole.

3. Directional Drilling: A boring method for installing pipe from a surface launched drilling rig. A pilot bore is formed and then enlarged by back reaming. The product pipe is then pulled in.

4. Pipe Ramming: A boring method that involves driving a steel casing pipe with a percussive hammer. The front end of the casing pipe may be open ended or closed. If open, remove spoil from the pipe.

5. Slurry Boring: A boring method that first forms a pilot bore by forcing a drill tube through the ground. The pilot hole is then enlarged by reaming. As the hole is enlarged with the reamer, drilling fluid (slurry) is pumped into the hole to hold the soil cuttings in suspension. After reaming, the product pipe is pulled into place.

6. Microtunneling: A boring method that consists of a remotely controlled pipe jacking operation utilizing a tunnel-boring machine. Personnel entry is not required.

7. Pipe Jacking: A jacking method in which pipe is pushed into the ground with hydraulic rams while soil is simultaneously excavated. Excavation is normally completed with a tunnel boring machine. This method requires personnel to enter the tunnel during the excavation process.

8. Utility Tunneling: A method of forming large diameter tunnels. As excavation takes place at the front of the tunnel, a liner is constructed to temporarily support the tunnel. Upon completion of the tunnel, the product pipe is pushed in place.

9. Other proven methods not described here may be allowed upon approval of the Jurisdictional Engineer.

1.03 SUBMITTALS

A. Submit under provisions of Division 1.

B. Proposed installation methods and equipment.

C. Samples, granular bedding material: submit 10 pound samples, if required.

D. Samples, granular backfill material: submit 10 pound samples, if required.

E. Gradation reports for fill materials and bedding materials unless the material used has been submitted and approved for related work on the project.

F. Results of Standard Proctor and in-place density tests on pit backfill, if required.

G. Construction sequence.

H. Catalog cuts, samples, and manufacturer's data and listing of applicable standards for special, unique or proposed substitute materials, if requested by Jurisdictional Engineer.

I. Certification that materials being provided meet the requirements of these specifications or that alternate materials or substitutions have received written approval of the Jurisdictional Engineer. Include shop drawings of casing spacers and proposed spacing.

J. Project Record Documents.

K. Contractor will provide Material Certifications to the Jurisdictional Engineer.

1.04 SUBSTITUTIONS

A. Use only materials conforming to these specifications unless permitted otherwise by Jurisdictional Engineer.

B. Obtain approval of Jurisdictional Engineer for all substitutions prior to use.

1.05 DELIVERY, STORAGE, AND HANDLING

A. Deliver only materials that fully conform to these specifications, or for which submittals have been provided to Jurisdictional Engineer and approved for use.

B. Store delivered materials and excavated materials in locations that will not interfere with operations or public use of adjacent streets and minimize environmental damage. 

C. Grade and shape stockpiles for drainage and protect adjacent areas from runoff. Provide erosion control around stockpiles.

D. Remove unsuitable and excess materials from the site.

1.06 SCHEDULING AND CONFLICTS

A. Construction Sequence:

1. Attend a preconstruction meeting if required by Jurisdictional Engineer.

2. Submit plan for construction sequence and schedule prior to commencing construction.

B. Conflict Avoidance:

1. Expose possible conflicts in advance of construction, such as utility lines and drainage structures.  Verify elevations and locations of each and verify clearance for proposed construction.

2. Complete other elements of the work that can affect line and grade in advance of other open cut construction unless noted on the plans.

3. Notify Jurisdictional Engineer of conflicts discovered or changes needed to accommodate unknown or changed conditions.

1.07 SPECIAL REQUIREMENTS

A. Stop Work: Stop work and notify Jurisdictional Engineer immediately if contaminated soils, historical artifacts, or other environmental or historic items are encountered.

B. Use of Explosives: Submit detailed plans outlining all proposed blasting operations, locations, methods, and use of mats and other safety measures to the Jurisdictional Engineer.

1. Obtain written approval before using explosives.

2. Use personnel experienced with explosives.

C. Conform to local, state, and federal requirements.

1.08 MEASUREMENT FOR PAYMENT

All measurements for payments will be made by the Jurisdictional Engineer or authorized representative.

A. Boring, Jacking, or Tunneling with Casing Pipe:  Measurement of the length of casing pipe and carrier pipe properly installed will be along the centerline of the casing. Payment will be made for both the carrier pipe and casing pipe as a combined single bid unit for the appropriate method of installation.

B. Jacking or Boring without a Casing Pipe:  Measure the length of the carrier pipe properly installed along the centerline of the carrier pipe.

C. Incidental Items: Unless otherwise specified in the contract documents the following items will be included in the unit price for boring, jacking, or tunneling.

1. Launch or reception pits or other construction excavations.

2. Placement compaction, and testing of backfill material in excavations and pits.

3. Casing spacers, annular space fillers, levels, backfill, casing end seals, and other appurtenances necessary to perform specified functions.

3.01 PREPARATION

A. Verify suitability of excavated materials for reuse as backfill.

B. Locate, mark, and protect existing utilities and facilities in the work area.

C. Provide access to utility service locations, such as valves, manholes, and utility poles.

D. Identify owners of utilities on or near the site, and notify them of operations to occur.

E. Protect existing facilities and landscaping features or replace as shown on the plans.

F. Protect bench marks, control points, and land survey monumentation or replace at Contractor's expense.

G. Select a method of installation that is appropriate for the soil conditions anticipated; will allow the pipe to be installed to the desired line and grade within the specified tolerances; and will prevent heaving or settlement of the ground surface or damage to nearby facilities.

3.02 EXCAVATION

A. Notify Jurisdictional Engineer prior to the start of tunneling activities.

B. Remove and stockpile the top 8 inches of topsoil for subsequent reuse. Do not mix topsoil with other excavated materials.

C. Place excavated material  away from trench.  Grade spoil piles to drain. Do not allow spoil piles to obstruct drainage.

D. Remove rock, rubbish, debris, and unsuitable materials.

E. Excavate the minimum size pits necessary to safely and properly perform the work.

3.03 SHEETING, SHORING, AND BRACING

Provide and install sheeting, shoring, and bracing or trench boxes as required to safely perform work, protect nearby structures, and work under construction.

3.04 DEWATERING (See Section 3010, 3.05)

3.05 TRENCHLESS INSTALLATION

A. General:

1. Install pipes by boring, jacking, or tunneling only where required by the plans.

2. Place bedding and backfill of carrier pipe beyond the end of the casing pipe, in tunneling pits, and in casing pipes installed by open-cut trenching according to Section 3010.

3. Install pipe at line and grade that:

a. Will permit the carrier pipe to be installed at its true starting elevation and grade within a maximum alignment deviation of the pipe centerline as specified in the contract documents.

b. When no deviation tolerances are specified in the contract documents, apply the following maximum deviations:

1)    Gravity Pipe:
       Horizontally: ± 1.0 foot per 100 feet;
       Vertically: ± 0.2 feet up to 100 feet; an additional ± 0.1 foot per 100 feet thereafter.
       Do not allow backfall in the pipe.
2)    Pressurized Pipe:
       Horizontally: ± 2.0 feet
       Vertically: ± 1.0 foot.  Maintain the minimum depth as specified by the local jurisdiction.

c. Greater deviation or interference with other identified facilities may be cause for rejection.

4. Provide any additional fittings, manholes, or appurtenances needed to accommodate any horizontal or vertical misalignment, if allowed by Jurisdictional Engineer, at no added cost.

5. Contractor shall be allowed to correct errors in grade of a casing pipe in order to achieve design grade of the carrier pipe by pouring an invert in the casing pipe, or by shimming the carrier pipe to a uniform grade, provided adequate clearance remains for proper installation of the carrier pipe.

6. Replace rejected tunnels at the Contractor's expense. This will include any additional fittings, manholes, or appurtenances needed to replace the rejected work.

B. Casing Pipe or Un-cased Carrier Pipe Installation:

1. Install pipe by auger boring, pipe jacking, microtunneling, open-ended pipe ramming, directional drilling (back-reaming required), or utility tunneling.

2. Do not use methods that displace excess soil, rather than removing it, such as impact moling, push rod, or closed end pipe ramming, unless specified in the contract documents or permitted by the Jurisdictional Engineer.

3. Water jetting will not be allowed.

4. Use a jacking collar, timbers, and other means as necessary to protect the driven end of the pipe from damage.

5. Fully support borehole at all times to prevent collapse. Insert pipe as earth is removed, or support bore with drilling fluid.

6.Fully weld all joints or use interlocking connection system according to Section 3020, 2.02.

7. Fill annular space between the inside of the bore hole and the outside of the pipe if the space is greater than one inch. Use flowable mortar CLSM (See Section 3010) or 3,000 psi concrete.

C. Carrier Pipe Installation Through Casing:

1. Clean dirt and debris from the casing pipe after installation.

2. Install casing spacers to pipe sections as necessary to support pipe barrel according to pipe manufacturer's recommendation.

a. Space according to pipe manufacturer's recommendation. As a minimum, place a spacer within 1 foot of each side of the joint and a maximum spacing of 6 feet.

b. Do not allow pipe to be supported by joint bells.

c. Lubricate casing spacers with drilling mud or flax soap. Do not use petroleum-based lubricants or oils.

3. Ensure that thrust loads will not damage carrier pipe joints. Provide thrust collars between joint shoulders of concrete pipe.

4. Provide timbers for sufficient cushioning between the end of the pipe pushed and the jacking equipment to prevent damage to the pipe.  Do not allow steel jack face to thrust against unprotected pipe end.

5. Position jacks so the resulting force is applied along the centerline of the pipe and the force is applied evenly to the entire end of the pipe.

6. Assemble pipe joints in the jacking pit before pushing the carrier pipe into the casing.

7. Close end of casing pipe around the carrier pipe with a casing end seal. Do not use PCC casing end seals with flexible pipes.

8. Fill the annular space between the carrier and casing pipe, only if required on the plans, with flowable mortar or CLSM per Section 3010, 2.11.

3.06 FIELD QUALITY CONTROL

Provide compaction testing of backfill materials and embankment, if required, as part of the field quality control for the carrier pipeline being constructed. Ensure that at least one compaction test site occurs at each pit.

END OF SECTION