CONSTRUCTION RESPONSIBILITIES 6-7
2.12 DRILLING REQUIREMENTS
7-8
2.13 PIPE INSTALLATION
8-9
2.14 BUTT FUSION PROCEDURE
9-10
2.15 CONNECTING TWO ADJOINING SECTIONS OF
DIRECTIONALLY BORED PIPE
10
2.16 GENERAL POST-CONSTRUCTION
10
2.17 AS-BUILTS
10-11
APPENDIX A DIRECTIONAL BORE DESIGN FACTORS
12-13
APPENDIX B DIRECTIONAL BORE GUIDELINES
14
APPENDIX C DIRECTIONAL BORE LOG
15 CITY OF LAKE WALES
DIRECTIONAL BORE STANDARDS
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Revised 2/8/2008
2.1 GENERAL DESIGN/PRECONSTRUCTION
The purpose of this standard is to provide guidelines for use by the development community
during the design and installation of underground water mains and wastewater force mains
using horizontal directional bores integral to the development of commercial, industrial or
residential subdivision properties.
2.2 REFERENCES
References for horizontal directional drilling include Mini-Horizontal Directional Drilling
Manual (1995), North American Society of Trenchless Technology (NASTT), Chicago, IL;
PPI Handbook of Polyethylene Piping (1998), Plastics Pipe Institute, Washington, D.C.;
PLEXCO Polyethylene Industrial Piping Systems; Technical Information; Technical Note:
Horizontal Directional Drilling (Guided Bore) with PLEXCO Pipe, et al.
2.3 ENGINEERS RESPONSIBILITIES
2.3.1 The ENGINEER should determine if the soils at the site are suitable for directional drilling
based on previous experience with the site soils or a geotechnical investigation.
2.3.2 All existing utilities, surface and subsurface structures must be located (in three dimensions)
for the design.
2.3.3 The minimum ground cover over a directionally bored water or wastewater utility line shall
be 36 inches. There shall be at least 18 inches vertical clearance when crossing under any
existing water main with a wastewater force main.
2.3.4 The ENGINEER should limit curvature in any direction to lessen force on the pipe during
pullback. Ideally, the directional bore should lie in a vertical plane.
2.3.5 The ENGINEER shall submit, as part of the permits application plans submittal package,
design calculations indicating predicted/permissible (maximum safe) pull force shall be
shown on the project design drawings. The ENGINEER assumes all responsibility for
proper design of the directional bore. Some factors to be considered in calculating the safe
pull force follow. Additional discussion can be found in Appendix A.
The pullback force is calculated at the leading end of the pipe behind the pulling head.
The frictional resistance is highest just prior to movement and decreases with movement. CITY OF LAKE WALES DIRECTIONAL BORE STANDARDS
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Revised 2/8/2008
When pullback ceases, frictional forces and drag forces increase due to the
thixotropic nature of drilling mud. The mud starts to gel when it is undisturbed.
Buoyant force pushes the pipe up against the top of the borehole, creating frictional drag
between the pipe and the borehole.
Minimum curvature at the entry and exit pits is limited by the steering capabilities of the
boring equipment.
When the bending radius is too small, the safe pulling strength of PE pipe may be
significantly reduced by the additional tensile stresses due to curvature.
All bending stresses due to various curvatures in the boring path are additive and should be
subtracted from the safe pull force.
The safe pull-load is time dependent.
2.3.6 The ENGINEER must show the directional bore in profile view on the plans, showing the
pipe, as it should be installed. Maximum pull strength and minimum radius of curvature
shall be listed. All existing utilities shall be shown on the plans.
2.3.7 The ENGINEER shall provide signed and sealed As-Built drawings of the constructed
bore path, including any abandoned in place bores. The ENGINEER shall certify that the
pipe was installed within acceptable limits per the pipe specifications.
2.4 CONTRACTOR RESPONSIBILITIES
2.4.1 The CONTRACTOR shall supply all labor, supervision, tools and equipment, and materials
necessary to install carrier pipe by directional bore method for potable water or wastewater
systems. Installation of the carrier pipe system includes the installation of water mains or
wastewater force mains and/or any other devices or materials deemed necessary for the
respective systems. For CITY projects, materials may be supplied bye the City.
2.4.2 The CONTRACTOR shall provide experienced operators to perform directional boring.
The operator shall have performed at least three directional bores of similar pipe diameter
and bore length.
2.4.3 The CONTRACTOR shall be fully responsible for placement of the pipe per the
ENGINEERs specifications. See Paragraph 2.11.7 for tolerances.
2.4.4 The CONTRACTOR shall supply experienced persons who have received proper training in
the use of the fusion equipment according to the recommendations of the pipe manufacturer
and fusion equipment supplier to perform thermal fusion of the specific HDPE pipe to be
used.
2.5 EQUIPMENT
2.5.1 The directional drilling equipment shall consist of a directional-drilling rig of sufficient
capacity to perform the bore and pullback the pipe. CITY OF LAKE WALES DIRECTIONAL BORE STANDARDS
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Revised 2/8/2008
2.5.2 The steerable, directional-boring equipment shall produce a stable fluid lined tunnel with a
minimum burial depth of 36 inches for the carrier pip installation.
2.5.3 The tunneling equipment shall employ a fluid cutting technique. The soil shall be cut by
small diameter, high pressure jets of drilling fluid. The jets shall cut the soil in advance of
the boring tool, impregnating and lining the tunnel wall with drilling fluid. The drilling
fluid shall be inert and pose no environmental risk, such as bentonite or a polymer-surfactant
mixture producing a slurry of proper consistency.
2.5.4 The hydraulic power system shall be self-contained and free of leaks, with sufficient
pressure and volume to power the drilling operation.
2.5.5 The boring tool (head) shall be remotely steerable by means of an electronic detection
system. The toll location shall be monitored in three dimensions and logged every 10 feet
from the drilling rig. The boring tool shall pull the carrier pipe through the fluid lined
tunnel as it traverses the surface being crossed.
2.5.6 The rig shall have means to monitor and record the maximum pullback force during the
pullback operation. The pulling strength of the boring equipment shall not exceed the
HDPE pipe safety pull strength as per the manufacturers recommendation.
2.5.7 The butt fusion machine used to join sections of HDPE pipe shall have controls and gauges
for setting pressures used for facing, heating, and fusing.
Facing should be conducted at a pressure that produces properly faced pipe ends.
Heating pressure should be set so that the pipe ends maintain contact against the heater, but
are not forced against the heater (zero contact pressure).
Fusing pressure shall be as recommended by the pipe manufacturer and fusion equipment
supplier.
Heater surfaces must be clean and free of contaminants such as dirt, oil, grease and melted
or charred plastic. To clean the heater, only wooden implements and clean, dry, lint-
free non-synthetic cloths should be used.
The heater should be checked periodically for uniform surface temperature using a surface
pyrometer.
2.6 DIRECTIONAL BORE PIPE
2.6.1 Pipe shall be High Density Polyethylene (HDPE) as per AWWA C906.
2.6.2 Carrier: HDPE pipe shall be DR 11, working pressure rating of 160 psi. The following are
approved pipe manufacturers.
CRS, PolyPipe PE 3408, 4 to 24 diameter.
PLEXCO PE 3408, 4 to 24 diameter
Driscopipe 4000 Series, 4 to 24 diameter.
2.6.3 Material for pipes to be used for potable water application shall be approved by the National CITY OF LAKE WALES DIRECTIONAL BORE STANDARDS
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Revised 2/8/2008
Sanitation Foundation (NSF).
All fittings, sizes 4 inch and larger shall meet the requirements of AWWA Standard C 906-
90 (or most recent revision).
All fittings shall be ductile iron pipe size.
All fittings shall meet the requirements of ANSI NSF Standard 61.
All fittings shall be made of materials conforming to polyethylene code designation PE
3408.
Standard dimension ration shall be DR11
Pressure Class shall be 160 psi.
2.6.4 Color Coding: The piping shall be permanently coded to provide service identification.
Stripes along the entire outside length of the pipe, 120 degrees apart, shall be made by co-
extrusion or impregnation in accordance with the following schedule. Fully colored pipe
co-extruded from permanently pigmented HDPE is also acceptable.
SERVICE
STRIPED PIPE
SOLID COLORED PIPE
Potable water
Blue Stripes
Blue
Reclaimed water
Purple Stripes
Purple
Wastewater
Green Stripes
Green
2.6.5 Marking on the pipe shall include the following:
Nominal size and OD base.
Standard material code designation.
Dimension ratio.
Pressure class.
AWWA designation (AWWA C906).
Material test category of pipe.
2.7 TRACER WIRE
2.7.1 All piping shall be installed with a continuous, insulated, solid #10 gauge copper wire for
water main or force main location purposes by means of an electronic line tracer.
2.7.2 The wire insulation shall be solid color in accordance with the coding described in 2.6.4,
above. Blue coated (for water mains), or green coated (for wastewater), number 10 gauge
UF (Underground Feeder per National Electric Code Article 339) solid tracer wire must be
taped along all pipes. Sections of wire shall be spliced together using Buchanon connectors
or a similar approved method for splicing. Twisting the wires together is not acceptable.
Spools of #10 wire are available in 500-foot rolls.
2.7.3 Upon completion of the directional bore, the CONTRACTOR shall demonstrate to t