Boring - Trenchless International

A 20-inch steel pipe is elevated by cranes for pullback and the transition of product pipe back into the
opened hole. Because the pipe string-out and pullback was in a marshy area, a trench was excavated, which
caused ground water to fill in and provide a pullback floatation system in lieu of a typical pipe roller system.
A crane is floated on a barge as
bundled pipeline (12 inch/4 inch) is
floated across a main canal during
pipe pullback operations. The pipe is
supported by the crane and styrofoam
floats as it is being smoothly pulled
back through the earthen hole.
North america
April 2010 - Trenchless International
After the hurricane –
rebuilding New Orleans
In the aftermath of Hurricane Katrina, more stringent requirements resulted in the innovative use of Trenchless
Technology for the installation of underground infrastructure. Here we learn about a successful project involving
two crossings near levees.
Think of levees and you think of the
catastrophic consequences of their failure
when Hurricane Katrina came ashore
and rocked New Orleans in August 2005.
Over four years have passed since more
than 80 per cent of metro New Orleans
was left underwater when 53 of the levees
protecting the city failed. But while the city
has long since picked up the pieces and
returned to its vibrant self, the message
from the disaster has remained clear:
bolstering and preserving the surrounding
levee system is of the highest priority.
The images captured in the aftermath
of Hurricane Katrina resonate with people
around the world. For the underground
construction industry, those disastrous
results left a lasting impression, forever
changing the methods and procedures
associated with crossing a levee.
Michels Directional Crossings, a division
of Brownsville, Wisconsin-based
Michels Corporation, recently dealt with
this firsthand after being awarded a
contract by Chevron for work near New
Orleans that began in September 2009.
Michels signed on to complete two
separate crossings within two miles of
each other, both running beneath the
Mississippi River and the extremely
important protective levee system. The
first crossing was the 20-inch Fourchon
Pipeline, which consisted of 5,087 feet
of steel pipe running through silts, sands
and clay. The second crossing, the
4,708 foot Buras Bundle, ran through the
same soil conditions and consisted of one
12 inch and one 4 inch steel pipe.
Engineering challenges
In the aftermath of Hurricane Katrina,
the US Army Corps of Engineers
(USACE) adopted more stringent requirements
for construction around levees in
hopes of better preserving their protective
qualities.
For Michels and Chevron, this meant
meeting the USACE-established “Guidelines
for Installing Pipeline by Nearsurface
Directional Drilling under Levees,” which
required that: “…the entry or exit points,
when located land-side of a levee, should
be set back sufficiently from the land
side toe of the levee such that (a) the
pipeline reaches its horizontal level (max
depth), and/or (b) the pipeline contacts
the substratum sands or some other significant
horizon, at least 300-feet land side
of the levee toe.”
To discuss the plans to meet these
requirements, Chevron requested that
Michels meet directly with the USACE in
New Orleans several months prior to the
project start date.
Acting as a third-party engineer for
Chevron, Geo-Engineers provided Annular
Pressure Curve data based on representative
soils and proposed drill geometry,
which are just a few variables used for
estimating hydraulic fracture potential.
With this data, Geo-Engineers recommended
that downhole mud pressure be
limited to 92.7 psi in order to provide the
required 1.5 safety factor against fracture
within 300 feet on either side of the levee
toe (critical monitoring zone).
Armed with this information, Michels
developed and presented a comprehensive
drill plan that reflected many
innovative mitigative measures to reduce
annular pressure. While this consisted of
many specialised tactics, one particular
method involved performing a pilot hole
intersect just beyond the 700 foot long
critical levee monitoring zone to reduce
downhole pressures. Annular Pressure
Monitoring was also conducted through
this zone during both pilot hole drilling
and reaming operations, and the depth
of cover beneath the levee was also
maximised to minimise fracture potential.
The established target intersect zone was
1,800 to 2,200 feet from the levee side
entry point.
Construction challenges
Serving as project manager for Chevron,
Ralph Radomski oversaw the drilling,
pipe stringing and marine operations
conducted by the team of contractors.
To support Michels’ drilling operations,
Chevron hired a local contractor, Sunland,
who are familiar with directional drilling
procedures and have extensive experience
in local marine construction.
Sunland performed pipe string-out and
welding operations for both crossings,
and also provided marine support for the
HDD operations. This included barging
Michels’ resources to the exit sides and
excavating a temporary false ditch for
floating the pipe through a marsh area
before finding suitable water to float the
remaining section.
The first section of product pipe was
floated into the false ditch up to the main
canal, and the remaining pipe string was
staged in a tributary on the other side of
the canal, readied for attachment to the
first string. Both pipe strings were sunk to
the bottom and tied off for protection of the
coating. Once pullback operations were
initiated, the main canal was blocked off
and the two pieces were dewatered and
welded into one string. They were then
floated on top of the water for the duration
of pullback.
With the pieces in place and Tom
Breunig and Ray Viator overseeing the
project as managers for Michels, Michels
Project Manager Louis Barber and drillers
Paul Krings, Jeff Nehmer and Cale
Mullenix went to work.
The 20 inch crossing was conducted
first, with the pilot hole started in late
September. During vital drilling operations,
the flood stage for the Mississippi
River reached critical levels above eleven
feet, which was the established flood
level at the location. Because of this, the
USACE criteria required Michels to shut
down all drilling operations underneath
the levee on 21 October. Hurricane Ida
added more water to the mess when it
bullied its way ashore on 10 November,
and drilling operations were unable to
continue until 23 November.
The brackish water carried from the
Gulf of Mexico flooded the drill site equipment
and washed out the access roads.
To make matters worse, the floodwaters
also brought in an abundance of dangerous
reptiles, including snakes. Prior to
re-mobilisation of the entire crew, it took
a full week for mechanics to change out
oil, fuel, filters and electric motors for all
engines onsite, and for repairs to be made
to the access roads.
Once the repairs and maintenance were
complete, however, work on the crossing
went off without a hitch. The crossing was
designed to be 190 feet deep at the levee
and 68 feet deep at the lowest point of the
Mississippi River, and it was executed to
perfection by the two drill rigs performing
the pilot hole intersect. The crossing,
which Michels monitored for annular pressure
throughout pilot hole drilling and
reaming operations, was completed by
mid-December.
With that difficult stretch out of the
way, Michels began drilling for the
12 inch and 4 inch bundled crossing
in the first week of January. With the
co-operation of the weather this time
around, drilling and reaming operations
endured only minor difficulties
in maintaining the targeted pressure
beneath the levee. This was mitigated
by adding casing and thinning out
drill fluids at various stages of the
operation.
Once pressure was reduced to
acceptable levels, Michels was able
to successfully complete the drilling
and reaming operations for the bundle,
which was 180 feet deep at the levee
and 60 feet deep at the lowest point of
the Mississippi River. However, during
pipe pullback, it was discovered that
a portion of the 4 inch pipe was bent
and in need of repairs. Pullback operations
were temporarily delayed while
the repair was made. Once repairs
were made and X-ray, testing and coating
was conducted, pullback on the
crossing was complete by the end of
January.
Summary
With the devastation wrought by
Hurricane Katrina still fresh in many
minds, any work on any levee near New
Orleans is a sensitive endeavour with
a lot of eyes watching. But thanks to
close monitoring and the implementation
of specialised pressure reducing
methods, Michels was able to successfully
install both crossings within the
parameters set forth by the USACE and
protect the levee – and therefore the
city that has been billed as “The Big
Easy” – from any adverse impacts.
North america
April 2010 - Trenchless International
34
35