Page 386 - Trenchless Technology Piping Installation and Inspection

336 Cha pte r Ei g h t

Inspection Guide for Horizontal Auger Boring (HAB)
Preinspection Plan Review

Review geotechnical and soil reports.
Ensure DOT/agency facilities and nearby utility information are shown on the
plans and profiles and that the proposed alignment does not interfere with them.
Note the minimum cover above the top of the pipe and below the pavement surface,
or ground elevation (for longitudinal installations outside the influence of the
roadway) is _____ ft.

Note proposed pipe characteristics:
Casing material ___________________.
Casing material yield strength _____ksi.
Allowable pipe-jacking force _____ ksi.
Casing diameter _____________ in.
Overcut diameter ___________ in.
Casing wall thickness ________ in.
Casing spacers material ____________.
Spacer spacing ________________, carrier material ___________________.
Carrier diameter ____________ in.
Note the inside diameter of the casing pipe, and the outside diameter of the carrier
pipe. The difference is _______ in. (Typical minimum is 6 in., except for casing
pipes smaller than 8 in.)
Review contingency plan.

Review job-site layout including: distance from access pits to roadbed, proposed
sheeting and bracing, materials storage and fabrication area, safety devices (barrels,
guardrail, etc.), and dewatering pit locations.
Note unique or special items / circumstances: ___________________
Construction Inspection

Verify traffic control is consistent with the permit requirements, one call service
has been contacted, and the DOT/agency permit is on-site.
Verify job-site layout is consistent with the approved plans, especially the alignment
of the pipe and machine.
Verify continuous monitoring records indicate bearing and grade of the leading edge
of the pipe is consistent with the approved plans, dewatering effort is satisfactory, soil
volume removed is consistent with projection, and that workers understand the
contingency plan.

Verify pipe characteristics are consistent with permit requirements.
Verify the casing pipe is steel with smooth interior and exterior surfaces, is used
within the entire influence area of the roadbed, has clean and square ends, joints are
watertight, defective pipe is not used, and damaged pipe is removed.

FIGURE 8.18 Sample checklist for inspection of horizontal auger boring operations.