In its response to a mandate from the state of Florida to build a central sewer system for the city of Marathon, Weiler Engineering Corp. (WEC) went beyond the initial requirements and designed a comprehensive approach to wastewater management.
As a result, the costs of the overall wastewater collection/treatment system shrunk to $126.6 million, or less than half of the previously bid sewer-only project. With money saved by the engineer's plan, along with grant funding assistance, the city also was able to add a complete stormwater management system. The system is designed to treat and dispose of runoff from all 55 miles of city right-of-way and adjacent privately owned contributing areas, repave every city street and incorporate numerous other roadway improvements.
Construction included an innovative vacuum wastewater collection system that incorporated low pressure, force main and gravity technologies. The project also created a master stormwater system that reduces pollutant loading into near-shore waters.
The team had to tackle the site's hard rock and coral ground base and extremely low water tables. Large boring machinery was used to cut through the hard rock.
Trench safety was a major concern; stormwater exfiltration trenches often required excavation in excess of 7 ft. With narrow right-of-way and consistent encroachment of existing utilities, the sloping or stepping of trenches was often impossible.
To solve this problem, the contractor worked closely with WEC's construction engineering staff to assess and evaluate trench conditions and provide unique solutions; for example, trenches were immediately backfilled with FDOT No. 57 stone before any personnel were allowed to enter them.
These safety performance measures during construction contributed to an OSHA recordable incident rate of 0.01, no lost-time accidents and zero fatalities during the eight-year project.
In order to meet the state-mandated deadline, the project team also utilized strategically staggered construction schedules.
Best Water/Environmental Project
City of Marathon Sewer, Stormwater, Reclaimed Water and Road Rehabilitation, Marathon, Fla.
Contractor Lanzo Construction Co., Deerfield Beach, Fla.
Owner City of Marathon
Engineer The Weiler Engineering Corp., Punta Gorda, Fla.