If the annual influx of tourists wasn’t enough to make Exit 45 in Scarborough/South Portland important as a corridor to reach Casco Bay, Peak’s Island, Great Diamond, and Long Island add the Maine Mall to the mix and a smoothly functioning interchange becomes essential. In late 2019, Maine Turnpike Authority selected Sargent Corporation for the preload phase of what will be a reconfiguration and upgrade of the exit to add capacity, increase bridge clearance, replace on-ramps and toll plaza, and ready the exchange for a potential future Gorham by-pass. A Maine winter meant Sargent’s work was not easy.
After topsoil and unsuitable soils were excavated, 30 to 50 trucks per day hauled gravel and other materials for the “drainage blanket,” a 2- to a 3-foot layer of Type D roadway gravel that made a path for water to escape the clay layers. Subcontractor Hayward Baker used two wick drain machines, operating 24 hours, six days/week, to install 27,000 wick drains totaling 2 million vertical feet, later adding a third machine to meet the deadline. Crews constructed over 40 settlement platforms of plywood and a pipe flange, then placed 12 to 20 feet of pre-load fill on the clay layers to force water drainage. During the anticipated 9- to 12-month wait for settlement and stabilization, Sargent worked with Portland Water District to replace two 1949-vintage water lines – a 36” line through a 54” sleeve and a 24” line through a 42” sleeve. Then they began the stage 2 fills, which included 8 to 12 feet of fill at the new bridge approach locations. In total, Sargent placed 150,000 cubic yards of common borrow and 181,000 cubic yards of subbase gravel.
Despite snow, frost, and freezing conditions, wick drain placement and stage 1 of the fills continued on schedule, with only a single weekend shutdown. During a 10-day period in February, crews worked 24/7 to finish installing drains and filling 75,000 cubic yards in the preload areas. To replace the waterline crossings, workers spent 16 days inside the sleeves using jackhammers against the concrete and brick to remove the pipe sections one at a time.
ENVIRONMENT AND COMMUNITY
With wetland surrounding most of the site, stormwater BMP’s were installed, maintained, and inspected daily. Winter conditions necessitated a daily double application of mulch for stability. Construction entrances needed constant maintenance to avoid tracking material onto the Turnpike or ramps. The below-water-level excavation for the waterline install required constant dewatering for several months, and included containment and filtration devices for silt and sediment. The full Exit 45 project will improve both access and safety for the community. Over-height trucks frequently hit the bridge, which will be raised to a 16.5-foot clearance, and the new toll plazas will accept both cash and electronic payment. During the winter of a pandemic shutdown, Sargent is proud to have kept construction workers employed at a financially difficult time and to have completed each preload milestone early, with substantial completion 24 days ahead of schedule.
At the project’s peak, 60 trucks per day hauled preload material to the site, totaling 840 trips per day, with trucks merging in or out of traffic every 35 seconds. The 30,344 work hours had zero lost-time injuries or recordable.
Owner: Maine Turnpike Authority
Engineer: HNTB Corporation & Portland Water District
Contractor: Sargent Corporation
ï Herb Sargent, President
ï Eric Ritchie, Vice President Operations
ï Doug Morrison, Operations Manager
ï Craig Shorey, Project Manager
ï Adam Tenan, Project Superintendent
ï Pat Dubay, Project Estimator
ï Shaw Brothers
ï Bark Brothers
ï Hayward Baker
ï Comprehensive Land Technologies
ï Enterprise Electrical
ï Main Line Fence
ï On The Line
ï Project Flagging, Inc.
ï P.A. Lyford, Inc.