John Deere, PING Collaborate for Big Hole-in-One

Preferred Alternative Selected for Falls Bridge in Blue Hill

Thu March 14, 2019 - Northeast Edition #6
MDOT


The preferred alternative is to replace the existing Falls Bridge superstructure with an enhanced girder bridge superstructure.
The preferred alternative is to replace the existing Falls Bridge superstructure with an enhanced girder bridge superstructure.

Over the past 20 months, the Maine Department of Transportation (MaineDOT), the Federal Highway Administration (FHWA) and a local Bridge Advisory Committee have reviewed alternatives for the renewal of the Route 175 crossing over the Salt Pond in Blue Hill.

In accordance with the National Environmental Policy Act (NEPA), the MaineDOT, FHWA and the 11-member Bridge Advisory Committee established a purpose and need statement for the project and identified and investigated rehabilitation of the existing Falls Bridge, replacement of the bridge on its current alignment and construction of a new bridge at an alternate location over the Salt Pond. In addition, the team explored various construction and maintenance of traffic methods, identified site safety needs for commuters and pedestrian traffic and discussed the potential impacts to archaeological, historical and environmental resources.

After a thorough investigation of options, including rehabilitation of the existing Falls Bridge, the preferred alternative is to replace the existing Falls Bridge superstructure with an enhanced girder bridge superstructure. The existing stacked stone substructure will remain and will be rehabilitated to include new cast-in-place bridge seats and new roadway approach knee walls to assist in raising the bridge and road profile to accommodate sea level rise and improve traveling conditions.

To limit site impacts, a temporary bridge will not be used to maintain traffic through the project site, rather, accelerated bridge construction methods will be used along with a short-term road closure of up to 60 days with traffic detoured around the project site on State Routes 172 and 175 during bridge removal and replacement.

During the process to identify the preferred alternative, the department weighed heavily upon impacts to historical, archaeological and natural resources within the project limits, as well as issues identified in the Purpose and Need statement such as commuter and pedestrian safety during and after construction, impacts to commuting traffic and local businesses and construction cost and service life cost.

The rehabilitation alternative was not selected because it has substantially higher construction and service life costs than the replacement alternative and only provides a 50-year life expectancy compared to a 100-year life expectancy for replacement.

In preferring to construct a new enhanced girder bridge instead of a new tied arch bridge, the enhanced girder bridge provided the safest structure for commuter and pedestrian use by removing the arch, lateral bracing and hangers, provided the lowest construction cost and construction risk, and provided the lowest cost for long-term inspection and maintenance.

Finer details, including aesthetic enhancements, pedestrian and parking accommodations, construction schedule and cost, maintenance of traffic, and minimization of impacts, will be incorporated into the final design which will continue through 2020. Members of the bridge advisory committee and the public are encouraged to continue advising the department through the final design process.

MaineDOT's preferred alternative will continue to be reviewed under the National Environmental Policy Act (NEPA). A final selected alternative will result from agency consultation and efforts to mitigate impacts to archaeological, historical and natural resources.