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Planning and Safety Considerations for Trenchless Installation Methods 365
during the design phase of the project. Supplemental site visits by the
contractor are necessary to fully understand jobsite requirements and
limitations.
Detailed studies of trenchless machine production can be per-
formed only after the all the questions regarding surface and subsur-
face conditions and specific project conditions have been answered.
At that point, the contractor will be able to undertake production
analyses based on use of proposed trenchless equipment. This chapter
is devoted to two most important aspects of a trenchless project: plan-
ning and safety.
9.2 Planning for a Trenchless Project
A successful trenchless construction project requires surface, subsur-
face investigations, and safety considerations. Trenchless installation
methods require the design engineer to provide the contractor with
sufficient information to reasonably anticipate the obstacles that might
be encountered. During the design phase, surface and subsurface sur-
vey information will assist in determining the suitability of trenchless
installation by specific methods. Obtaining and providing accurate
surface and subsurface information will result in reducing the possi-
bility of installation problems and change orders during the work as
well as minimizing the possibility of litigations and disputes.
9.2.1 Surface Survey and Site Visit
A surface survey is required prior to designing of a trenchless con-
struction project. Each trenchless construction project has specific site
requirements. The surveys should be conducted along the center line
of the proposed bore path for a width of 100 ft. As a minimum, sur-
face surveys should include the following:
• Work area requirements
• Existing grade elevation data
• Surface features such as roadways, sidewalks, and utility
poles
• Boring or test shaft/pit locations
• Waterways and wetlands
• Visible subsurface utility landmarks such as manholes,
cleanouts, service laterals, or valve boxes
• Adjacent structures to bore path
Review of existing geological or geotechnical reports, maps, aerial
photographs, and review of depositional history are important in
developing a preliminary design survey. For example, if the area has
been subjected to glaciations, then cobbles, boulders, and gravel can