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Madrid Working on Pensacola Bay Bridge Foundations

Madrid Engineering Group, Inc. (MEG) has mobilized and is working on water borings with a few land borings for the Pensacola Bay Bridge project, a FDOT District 3…

Madrid Engineering Group, Inc. (MEG) has mobilized and is working on water borings with a few land borings for the Pensacola Bay Bridge project, a FDOT District 3 design-build. Our partners are Skanska USA, one of the world’s largest contractors, andWSP│Parsons Brinkerhoff, an ENR top 20 engineering company. The project involves replacing the existing, 3-mile long bridge with two parallel bridges.

Madrid is completing soil borings, laboratory testing of soil samples, and foundation design for about 1/4 of the bridge supports. The project has an aggressive schedule and borings are to be completed by the end of January 2017. The scope includes 186 bridge SPT borings (176 over water) with an average depth of about 165 feet below water level, with an anticipated maximum depth of about 245 feet.

Jack-up barge with both SPT drill rig and CPT rig on board “We mobilized and attempted cone penetrometer testing (CPT), which would have cut significant time off the job, but encountered numerous difficulties due to the length of rod that had little to no lateral confinement and intermittent gravel layers at depth”, said John Delashaw, PE, Chief Geotechnical Engineer for Madrid Engineering. “It was worth it both from a cost and scheduling standpoint to try this technology. However, these sediments are very, very soft and extensive, and then underlain by a gravel layer that is difficult for the cone tip to penetrate. This caused the drill rod to “bow” when the downpressure increased. We went with a triple casing approach, and that increased the lateral stiffness allowing us to push deeper, but made other parts of the operation effort more difficult and time consuming which reduced the efficiency of the combined operation. Ultimately, we are just doing SPT borings.”

“Just” may not be the right word to describe this effort… the borings are being completed from jack-up barges that sit above the water, eliminating most of the effects of tide. Barges are supplied by ShallowDraft, a company that has supported many geotechnical investigations in the Panhandle over the years. Barges are up to 60 feet long and have sleeping cabins for barge staff. Soil samples are required to be obtained every 2.5 feet of depth, which means a lot of trips into and out of the borehole.

Madrid has enlisted subcontractor Amdrill, based in Orlando, to help meet the demanding schedule. Amdrill has been a partner of Madrid Engineering since we opened our doors 23 years ago. Tim Clarkson, President, relishes jobs like this – barges jacked up on spuds, located by GPS on open water, with deep borings required – the hardest jobs are the ones we (Madrid and Amdrill) like to do.

James Spoon, drilling operations manager for Madrid, talked about the challenges of this job – “It’s been a difficult one to work on so far because of the unique stratigraphy that limits what we can do. But we are getting it done and have worked out the kinks now, so we are making good progress and will meet the schedule.”

Madrid Engineering Group, Inc. offers services statewide and is a FDOT DBE certified company with over 23 years of experience and prequalified in both CEI and geotechnical engineering (10- and 9-series, respectively). If you would like to include Madrid Engineering on your team for the next project or proposal, please contact us!

Drilling Services – James Spoon 863-512-4055

Engineering Services – John Delashaw PE 863-533-9007