Underground Construction - October 2019 - 23

the engineering consultant and Bennet Mechanical constructed
the pig launcher.

Timeline
The project scope of work specified that pipe cleaning had to be
accomplished between Oct. 15 and Dec. 15, 2018, even though
weather conditions during that time of year could complicate
marine operations. However, weather was expected to be even
worse later in the winter, and could affect all work operations,
particularly the pumped water delivery necessary to propel pigs
through the intake lines.
"The two largest challenges," said Ryan Vogt, project manager
with Galcon Marine, "were completing the project within the allocated time frame, due to poor weather conditions, and constructability of the project, which required maintaining full access on the
island for resident and emergency vehicles."
Vogt said the time frame chosen was good for the city because
it was the lowest usage interval for its clients. But from a marine
standpoint, the prevailing winds at that time of year are predominantly from a bad direction, making the retrieval of pigs, ROV
operations and drawing water for the operation very difficult.
"Using smaller gear for retrieval, proper planning, outside-thebox thinking and lots of luck from the weatherman," Vogt continued, "we were able to launch and retrieve pigs in a higher sea state.
The water used to push the pigs through the line had to come from
the inner lagoon. This forced us to run three 18-inch HDPE lines
across the main road for the island, resulting in having to construct
a highway-rated, temporary bridge to allow continued roadway
access." (The lines couldn't be buried due to underground utilities.)

"This was a large undertaking and very unconventional," he
said. "In addition, we had to construct the launcher and support
system, pour a concrete reinforcing pad for the launcher, manage
the pumping operations, facilitate the pig launching and retrieval,
coordinate site revetment, construct a display for the launcher,
ensure the system could handle the pressure requirements of the
operation, and produce a pigging manual for future reference."

Pigging operations
Rex Murphey, Montauk Services CEO, explained the actual pigging
operations.
"In order to be prepared for any cleaning contingency, we
provided 18 pigs for the project," said Murphey. "Pigs were
constructed of open cell polyurethane foam with various densities.
We used standard pigs but selected their sequence and diameters
to gradually clean the pipelines. The 2.5 pcf density swab utilized
a blue elastomer foam, which was new to the market and gave us
the flexibility of a standard swab, but with a much better cleaning
ability. Standard swabs are usually one-pound density and shot
only to 'prove' the pipeline prior to the utilization of harder pigs."
The three intake pipes converged downstream from the common
inlet. The chamber had three 60-inch connection flanges where
the pig launcher was attached. The launcher design was a joint
effort between Montauk Services, Galcon Marine and Associated
Engineering, with the local fabrication managed by Galcon.
All pigs were easily inserted into the oversized bore of the
horizontal launcher and then pushed forward against a tapered
barrel section, which reduced the diameter to 60 inches,
corresponding to the nominal pipe size. When water was pumped
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Underground Construction - October 2019

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