Project At-a-Glance
- Record Setting design/build for HDD 5,400-ft crossing beneath St. Andrew Bay using 24-inch diameter Fusible PVC Pipe for new resilient water main.
- Limited pipe layout area was solved by implementing a three pipe string approach with two intermediate fusions during pullback.
- Subsurface conditions along drill path consisted of loose sandy soils that posed inadvertent drill fluid release concerns
- Evaluation of drill path, subsurface characteristics combined with hyrdrofracture analysis led to successful installation and no fluid losses.
Recognition
- Watch the video of this record setting HDD installation provided by Underground Solutions, Inc.
Project Narrative
Originally situated on the Hathaway Bridge spanning St. Andrew Bay, the primary main supplying water to eastern Panama City Beach was found to be leaking in 2018. Although a temporary line was installed on the sidewalk of the eastbound lane of the bridge, a resilient long-term solution was needed. Subsequently Bay County Utilities and Florida Department of Transportation developed this design/build project to install 5,400 LF of 24-in Fusible PVC Pipe® below St. Andrew Bay by Horizontal Directional Drilling (HDD) to replace the temporary line.
Brierley Associates served as Trenchless Specialist subconsultant to Dewberry, the lead designer of the Design/Build Team. Brierley Associates’ design work included drill path geometry evaluation, developing the HDD engineering report with pull load calculations along with completing pipe stress calculations, hydrofracture analysis, and a risk evaluation. Brierley also contributed on the technical specifications and project planning for the HDD installation
One of the project challenges was limited pipe layout area that was solved by implementing a three pipe string approach with two intermediate fusions during the pullback. Additionally, loose sandy soils within the drill path posed some concern about inadvertent releases of drilling fluids within the bay. Through careful evaluation of the geotechnical report, profile design iterations, hydrofracture analysis and drilling methodology, a successful plan was developed that resulted in no losses of drilling fluid and a pipe installation with very low tensile loads.
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