NOTE: This guide specification covers the requirements for work related to the installation of utility systems (i.e., electrical power, communications, water, gas, oil, petroleum products, steam, sewage, drainage, irrigation, and similar facilities) utilizing the microtunneling trenchless excavation methods.

Comments and suggestions on this guide specification are welcome and should be directed to the technical proponent of the specification. A listing of technical proponents, including their organization designation and telephone number, is on the Internet.

Recommended changes to a UFGS should be submitted as a Criteria Change Request (CCR).

Use of electronic communication is encouraged.

Brackets are used in the text to indicate designer choices or locations where text must be supplied by the designer.

NOTE: Microtunneling Horizontal Earth Boring is a process characterized as highly sophisticated, laser guided, remote controlled system providing the capability of continuous accurate monitoring and control of alignment and grade.

1. Microtunneling is ideally suited for placing a 450 to 1800 mm 18 to 72 inch casing pipe for containing utility lines. Distances between manholes can exceed 300 m 1000 linear feet. It is ideally suited for utility lines that must be buried in rock, sand, clay and contaminated soils in depths ranging from 1.8 to 30 m 6 to 100 feet below grade. Varied soil conditions can be dealt with a single cutting head and dewatering is greatly reduced. There are many manufacturers of equipment that can perform the work described in this specification.

2. Permanent pipe casing can be used as the carrier pipe or a separate pipe may be placed inside the casing. The designer has the option of selecting the casing pipe however it may limit the number of possible bidders.

3. Cathodic protection for steel pipes should be considered where the anticipated degree of corrosion is so great that coating systems, including polyethylene encasement, are not adequate to protect the piping for the desired life of the system.

NOTE: Project Drawings:

1. The following information should be shown on the project drawings:

a. Plan and location of all new pipelines, including size of pipe casing and carrier pipe.

b. Location and profiles of soil sampling and bore holes.

c. Location, size, and type of service of existing connecting, intersecting, and adjacent pipelines and other utilities.

d. Paved areas and railroads which pass over new pipelines.

e. Profile, where necessary to show unusual conditions.

f. Manhole and lateral piping bedding conditions.

g. Details for the connection of the pipe casing to manholes and infiltration control.

h. Location of surrounding structures and sensitivity to settlement, pile foundations, and subsurface structures that could be affected by the project.

i. Show traffic plans for work near roadways and possible equipment and spoils storage areas. Spoil storage and removal requires a large area for dewatering and must be strictly controlled in Section 01 57 19.00 20, TEMPORARY ENVIRONMENTAL CONTROLS. Refer the other sections for specific removal and disposal of hazardous materials. Spoil storage locations and construction need to consider possible runoff into wetlands, streams, or storm drains.

j. Maximum working pressure of the system.

k. Class or thickness of pipe, including material identification, and limits for same where class or thickness will differ along length of pipeline.

NOTE: This paragraph is used to list the publications cited in the text of the guide specification. The publications are referred to in the text by basic designation only and listed in this paragraph by organization, designation, date, and title.

Use the Reference Wizard's Check Reference feature when you add a RID outside of the Section's Reference Article to automatically place the reference in the Reference Article. Also use the Reference Wizard's Check Reference feature to update the issue dates.

References not used in the text will automatically be deleted from this section of the project specification when you choose to reconcile references in the publish print process.

NOTE: Design Requirements:

1. External loads shall include earth loads, truck loads, seismic loads, construction loads (i.e., sheetpile insertion/extraction at manholes and pipe ramming/jacking forces) and impact in the design stage of the project; also hydrostatic and buoyancy forces.

2. It is recommended that the following site information should be provided (at a minimum):

a. Grain size analysis of soil particles

b. Unconfined compressive strength of soils

c. Dry density

d. Cohesion

e. Shear strength

f. Plasticity of fill material

g. Classification of fill material

h. Rock type and color

i. Permeability

j. Moisture content

k. Water table depth

l. Nature of pollutants

m. Grain size

n. Core recovery TCR SCR

o. Fracture index

p. Standard penetration N value

q. Friction angle

r. Where possible, soil boring information should be provided at not more than 60 m 200 ft intervals outside the bore of the tunnel and at manhole locations.

3. Use equivalent pipe design for the project conditions (using the applicable criteria for each pipe material) for each different pipe material.

NOTE: Provide only those pipe sizes and materials applicable to the project requirements.

NOTE: Choose one of the following options.

NOTE: Where the casing will not serve as the actual carrier or utility line, specify the appropriate carrier pipe, joints and connections in other specification Sections 33 11 00 WATER DISTRIBUTION, and 02630, "Storm Drainage."

NOTE: Review submittal description (SD) definitions in Section 01 33 00 SUBMITTAL PROCEDURES and edit the following list to reflect only the submittals required for the project. Submittals should be kept to the minimum required for adequate quality control.

A “G” following a submittal item indicates that the submittal requires Government approval. Some submittals are already marked with a “G”. Only delete an existing “G” if the submittal item is not complex and can be reviewed through the Contractor’s Quality Control system. Only add a “G” if the submittal is sufficiently important or complex in context of the project.

For submittals requiring Government approval on Army projects, a code of up to three characters within the submittal tags may be used following the "G" designation to indicate the approving authority. Codes for Army projects using the Resident Management System (RMS) are: "AE" for Architect-Engineer; "DO" for District Office (Engineering Division or other organization in the District Office); "AO" for Area Office; "RO" for Resident Office; and "PO" for Project Office. Codes following the "G" typically are not used for Navy, Air Force, and NASA projects.

Choose the first bracketed item for Navy, Air Force and NASA projects, or choose the second bracketed item for Army projects.

NOTE: Use other specifications to require submittals for the actual carrier pipe unless the pipe casing is going to act as the carrier pipe.

NOTE: Suggested Submittals:

1. The following material should be submitted for review by the designer:

a. Manufacturer's literature describing in detail the microtunneling system to be used. Detailed descriptions of projects on which this system has been successfully used, giving total pipe length, project duration, and number of restarts.

b. Method of spoil removal.

c. Anticipated jacking loads.

d. Method(s) of controlling groundwater at shafts and by the microtunneling boring machine.

e. Shaft dimensions, locations, surfaced construction, profile, depth, method of excavation, shoring bracing, and thrust block design.

f. Verification that the pipe complies with the specification.

NOTE: Delete coatings not allowed for the project. AWWA M11 in the chapter on protective coatings contains information on the relative merits of cement mortar and coal-tar enamel coatings. See Forward to AWWA C210 for information on coal-tar epoxy coating.

NOTE: Allowable Materials:

1. The project specification should allow all carrier piping materials for the utility lines which are suitable for the project, each to be permitted as a Contractor's option. The structural support contribution of the casing piping and annulus grout may be considered when specifying the thickness of the utility piping. The casing may also greatly reduce infiltration of ground water.

2. Pipe materials which are known to be unsuitable for particular local conditions, (i.e., corrosion, deterioration, etc.) should not be permitted for the project for either the casing or the utility piping. However, consider use of more effective protective coatings, etc., where economically feasible. Consider the protective nature of the pipe casing and annulus grout with regards to exterior attack. [Cathodic protection of the casing may also be desirable.]

3. Utility piping material and size should be specified in their own appropriate sections of the specification.

4. Several methods of installing pipe casings are available to the Contractor. Different tunneling machines have different means of installing the casing. Many of the machines allow the pipe casing to be used as the jacking shield and are left in place after the tunneling head has reached the receiving pit. Other machines use a temporary jacking shield that is replaced with a lighter casing. The final casing material doesn't need to be as strong because it doesn't need to jack the cutting head. Fiberglass casing can be an appropriate alternative for these methods. The Contractor should have the option of selecting an appropriate alternative for the casing based on his tunneling method and the design requirements of the utility lines.

5. The annulus grout (e.g., the grout the fills the void between the casing and the utility line(s) is traditionally a lightweight grout that is designed to merely stabilize the utility line(s). The utility lines are usually temporarily supported on wooden shims to position them inside the casing prior to grouting.

NOTE: Insert the necessary Pressure/Thickness Class to meet project conditions, as determined from AWWA C151.

NOTE: Do not locate flanged, grooved, and shouldered joints on buried pipelines unless they are in valve pits or chambers.

NOTE: Polyvinyl Chloride Pipe (PVC): PVC pipe may be an ideal conveyance system for sewage and storm water, and for the construction of culverts installed and constructed by microtunneling methods. These pipes require microtunneling systems that generate low compressive loads on the pipe.

NOTE: This section covers reinforced concrete pipe intended for use as conveyance systems of sewage and storm water, and for the construction of culverts and industrial casings installed and constructed by jacking methods.

NOTE: Reinforced Concrete Pipe:

1. Nominal dimensions: Typical nominal dimensions for reinforced concrete pipe are detailed in ASTM standards [ASTM C 76MASTM C 76, ASTM C 361M ASTM C 361, ASTM C 655M ASTM C 655, ASTM C 822]. Pipe meeting these requirements is generally acceptable for jacking. The permissible variation allowed with respect to these and other dimensions should be in accordance with the variations listed in the section.

2. Pipe lengths: Concrete pipe manufactured for jacking operations should be typically manufactured in lengths of 2.25 to 2.4 m 7.5 to 8 feet. This is primarily a function of the size of the jacking equipment and the excavation. Lengths vary in any given geographical area.

3. Joint: Historical field data has shown that concrete pipe joint for jacking applications is commonly of two types, all concrete or concrete and steel. Factors influencing the selection of one of these joint types, or other alternative joints, include:

a. Magnitude of the anticipated jacking forces

b. Joint deflection characteristics

c. Joint shear strength required during the jacking operation

d. Specific site design parameters.

4. Joint description: Two primary types of joints are used:

a. Joint formed entirely of concrete that may utilize a rubber gasket or mastic to provide the seal. Rubber gaskets should be used where water tightness is needed. A compressive bearing strip is required between the faces of the adjoining pipes.

b. Joint includes an assembly of steel bands or steel bell ends with spigot rings and rubber gaskets. This type of joint also requires a compressive bearing strip.

5. Joint selection: Historical performance has shown that in instances of straight alignment under relatively low jacking forces, both types of joints can be used. Curved alignments and high jacking pressures may require the use of the second type of joint.

6. Axial load capacity: A factor of safety of at least 2.22 should be used for pipes installed by jacking methods. The axial load capacity should be based on the ultimate strength of the concrete and it assumes that the load is uniformly distributed over the bearing surface. Eccentric or concentrated load combinations on the pipe surface should be evaluated for effective surface contact area and reduction in the factor of safety.

NOTE: This section covers steel pipe used as an encasement for other carrier pipes or it may also serve as the carrier pipe for water, gas, sanitary sewer or other utility products.

NOTE: This section covers centrifugally cast fiberglass pipe for installation be pipe jacking and microtunneling for use in sanitary sewer, storm drain, wastewater collection and industrial effluent applications.

NOTE: This section covers the criteria for the manufacture, quality assurance testing, inspection, installation, and field acceptance testing of vitrified clay pipe to be used in jacking, sliplining, and in tunnels for the conveyance of sewage, industrial wastes, and storm water.

NOTE: Microtunneling Information

The minimum depth of cover over the pipe being installed using the microtunneling process is normally 1.8 m 6 feet or 1.5 times the outer diameter of the pipe being installed, whichever is the greater. Microtunneling work is executed so as to minimize settlement or heave. The overcut of the tunneling machine or method shall be determined by the need to satisfy settlement or heave tolerances. Overcut should not exceed 25 mm one inch on the radius of the pipe. The annular space created by the overcut usually can be filled with the lubricating material that is used to reduce the friction drag of the soil on the pipe (i.e., bentonite slurry).

NOTE: Select one of the following options. The first option restricts the Contractor to using an unmanned tunneling machine while the second option also permits the Contractor to use tunneling shields.

NOTE: Some microtunneling methods utilize a temporary jacking pipe or shield that is replaced by a permanent casing or carrier pipe. This section applies to all jacking pipes, but it intended to ensure that temporary jacking pipes are covered by this section.

NOTE: Jacking and Installation Information

1. The length of drive that is possible to achieve with particular equipment is dependent upon the jacking force required to push the pipe, the soil conditions and the depth of the pipe. The jacking force require is a function of many variables including the soil conditions, depth of the pipeline, annular space between the pipe and soil, lubrication of the pipe, material, diameter and strength.

2. When a slurry system is used by the Contractor, the composition of the slurry must be closely monitored for specific gravity and viscosity in certain soil conditions. With an auger soil removal system, the speed of rotation of the auger flight and the addition of water and/or compressed air must be closely monitored.

NOTE: Indicate appropriate Section number and title in blank below using proper format per UFC 1-300-02.