• The $17.8 million project consists of replacing the Warren Avenue Overpass (NB & SB) I-95 bridges due to maintenance requirements of the existing bridge as well as the need to address collision damage from over-height vehicles on Warren Avenue. 

• The vertical clearance of the new bridges with Warren Avenue will be a minimum of 16’-6”, increased from a clearance of 13’-10” for the existing bridges.  Thus, an associated grade raise of 2 to 5 feet along northbound and southbound I-95 is required to meet the increased elevation of the new bridges.

• Additionally, the design called for the replacement of the existing three-span bridges with single-span integral abutment bridges.  This change results in new fill heights of approximately 12 feet at the approach embankments.

• A layer of marine clay between 35 and 60 feet thick was analyzed for settlement under the load of the new fill heights.  If normal weight fill was used to construct the approach embankments, settlements of up to 26 inches were expected over the 75-year design life of the bridge.

• Settlement mitigation with lightweight fill was selected because it could be accomplished within the lateral extents needed during construction staging and because it eliminated the need for the hold period required for surcharging.  The use of lightweight fill brought anticipated settlements within reasonable ranges over the design life of the bridges. 

• UL-FGA was selected as the lightweight fill for settlement mitigation because of cost, constructability, and fuel-compatibility concerns.