EN Engineering has designed hundreds of Horizontal Directional Drilling
(HDD) crossings and is an industry leader in the identification, planning,
design, and support during installation of HDDs. The use of HDD in the
pipeline industry began in the 1960s and was fully established by the 1980s
as a way to install pipelines while utilizing trenchless technology with
minimal impact to the feature being crossed. These features, including
roads, railroads, waterbodies (rivers, streams, and wetlands) or other
environmentally or culturally significant areas are typically sensitive in
nature and cannot be disturbed by conventional open trench construction
methods.
Whether part of a larger overall pipeline installation or a stand-alone
maintenance/replacement project, EN Engineering completes a preliminary
front-end assessment of all HDD crossings. Due to the potential risk and
cost associated with an HDD, the assessment checks to see if other
construction techniques (including open cutting and conventional boring) can
be utilized instead. If it is determined that because of construction,
permitting, or other issues a conventional crossing technique is not
feasible, our team will begin its HDD planning process.
Utilizing maps, drawings, aerial photography, elevation data, and other
technology, we will develop possible HDD alignments, workspace layouts
(including pipe pull back), entry and exit points, considerations for
drilling mud management, and a preliminary plan and profile. Once this
desktop analysis is done, we typically conduct a site visit to confirm
actual site conditions support this preliminary design and adjust it as
necessary.
Based on the location and complexity of the HDD, EN Engineering determines
the quantity, locations, and depths of exploratory soil bores needed to
complete the detailed design of the HDD crossing. These borings show the
depth of the water table and identify soil and rock properties. A hydraulic
fracture analysis may be performed using geotechnical data to minimize the
risk of inadvertent mud release during the drill. This analysis is sometimes
required by the governing permitting and/or regulatory agency and uses the
Delft equation as described in the “Guidelines for Installation of Utilities
Beneath Corps of Engineers Levees Using Horizontal Directional Drilling”
USACE, 2002. EN Engineering partners with geotechnical service firms that
can complete the geotechnical field investigations, laboratory testing, and
associated reports we needs to complete the HDD design.
EN Engineering will coordinate a topographic survey of the proposed project
area based on the recommended alignment for the final engineering design
effort. In addition, a boundary survey can be performed to accurately
identify the property owners affected by the project. If required, property
plats can be developed for land negotiations. EN Engineering also provides
the survey support to assist the construction contractor and to capture any
as-built information. We maintain relationships with established survey
firms that can complete the required design, boundary, pre-construction
staking, and as-built survey activities.
Next, EN Engineering will advance the preliminary engineering for the HDD
through the detailed design phase. This includes determining the appropriate
drill path to ensure that bending, pullback, and testing stresses are within
industry standards. For challenging or unique crossings, we can have layouts
for each HDD location and workspace reviewed by a reputable HDD contractor
to ensure that constructability is optimized.
EN Engineering utilizes the Pipeline Research Council International (PRCI)
guidelines in its design of HDDs, which involves modeling the drilled path
to define its shape and properties during installation. Utilizing these
guidelines, we develop a design that governs pipe specifications (wall
thickness, grade, and corresponding D/t ratio), depth of drill, entry/exit
angles, radius of curvature and tangents, and overall drill length. Based on
the pipe specifications, operating pressures, and site elevations, we can
develop pre- and post-installation hydrostatic testing parameters. Our team
will also develop a detailed material list (primarily pipe and coating),
identify qualified vendors, develop bid packages, analyze quotations, and
cut requisitions as needed, with purchase orders typically issued on
client’s letterhead.
When requested, EN Engineering provides the drawings, exhibits, data tables,
and other information required in support of the permitting process. Our
team understands the permitting process as it relates to the Federal Energy
Regulatory Commission (FERC), the US Army Corps of Engineers (USACE), US
Fish and Wildlife Service (USFWS), and other state and local agencies
related to environmental, historic preservation, and non-environmental
permits. We can also provide exhibits, sketches, and plats needed for the
acquisition of both temporary and permanent easements for the construction
and operation of the installed HDD crossing. Using a subcontracted land
services company or the client’s internal land department, we can
investigate current ownership of all affected properties the project may
encroach on where amended or new easements may be required. This
investigation includes the study of tax maps, property deed records, and
similar sources of information.
EN Engineering provides support related to the construction bid phase,
including the identification of qualified contractors, development of a
scope of work and overall bid package, responding to RFIs, and selection of
a construction contractor. We can also help with the pre-bid meeting, the
associated job site review, and staking of the final route and workspace
layout for the bidders.
We also review the HDD design and drilling plan with the awarded contractor
to determine if the method and equipment meet the project’s requirements.
Risk mitigation strategies may be implemented at this time, including but
not limited to: increasing the annular space during the pilot hole,
decreasing drilling fluid density and/or fluid pump rate, specifying mud
additives to maintain tunnel stability, or lowering the alignment.
When requested, EN Engineering can review the drill pilot-hole profile prior
to pullback of the pipe string in order to determine if the drill
alignment/geometry appears to be acceptable and the pipe will not be
overstressed. We can review the pilot-hole drill data daily in order to
monitor the progress and ensure the drill is being installed per the design
plan.
Our team can provide an as-built plan and profile and pipe joint/weld map,
utilizing information from the HDD contractor, including the X, Y, Z
location (or the azimuth/inclination and distance) of each drill string
joint. We will record the entry and exit points for the pilot-hole drill
string and any exposed drill string joint ends, and capture the top
centerline of pipe along the portion of the pipeline from the tie in points
to the entry and exit points of the HDD.
Upon completion of the HDD, EN Engineering can
assemble and provide a project completion package,
consisting of the as-built drawings, boring logs,
design calculations, material test reports (MTRs) and
other documents necessary to meet the client/owner
recordkeeping requirements.
(630) 353-4000
info@entrustsol.com