HDD Provides Solution to Florida Storm Drain Outfall

City of Pensacola, Fla.When the City of Pensacola, Fla., was facing a difficult challenge re-routing an existing storm drain outfall to Pensacola Bay, horizontal directional drilling (HDD) provided the answer.

The City needed to construct new storm structures and conveyance pipe in an area of a known HAZMAT plume associated with an adjacent EPA-managed Superfund Site. EPA mandates required that the new pipe could not be direct-bury due to the presence of a contaminated high groundwater table.

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A direct-bury pipe application would have required extensive groundwater de-watering of the contaminated area and the near by treatment facility could not accept such a high volume of pumped groundwater for treatment of the contaminants and proper disposal. Therefore, HDD technology was chosen as the most viable option for installing the conveyance pipes with less returns that could be quantified, containerized and properly disposed of.

City of Pensacola engineer Derrik Owens contacted both Gator Boring & Trenching Inc. and the EPA to discuss the feasibility of constructing three parallel 26-in. HDPE pipes using HDD with only 4 ft of vertical cover, only 2 ft of separation and less than 1 percent of fall over a 400-ft run.

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“This was a very challenging situation that required us to apply technology that is not typically utilized for this type of application and the result was a successful project that was beneficial to everyone,” said Owens.
Roads Inc. of Pensacola, Fla., was the successful bidder on the project. “Finding a good HDD sub-contractor was key to building this project. Gator Boring & Trenching was able to fulfill all of the project specifications for HAZMAT certification, equipment requirements and gravity experience,” said Roads Inc. vice president Robby Williams.

City of Pensacola, Fla.The first two bores were completed when on June 17, 2012, an unexpected flashflood hit Pensacola. Flood waters rose to within inches of vital engine components of a UNI 160×240 Universal HDD drilling rig. As quickly as the waters receded, the Universal HDD rig was up and running. Construction of the 400-ft HDD portion of the project was completed on time, on grade and on alignment.

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Carter Cranes stepped in to assist in installing the manholes custom-fabricated by Southeast Precast. “It was a great experience to build this project for our community and to work with local contractors and suppliers,” said Gator Boring & Trenching Inc. vice president Eric Lyons.

All HDD returns were collected and disposed of as required and supervised by the EPA. Horizontal directional drilling can be a viable solution for gravity pipeline installation, as well as a variety of HAZMAT remediation/containment

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Lisa J. Lyons is general manager at Gator Boring & Trenching.

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