When the Maine General Hospital started construction on the Alfond Center for Health, they had some unique challenges to face.
To create level areas to build on the hilly site and deal with wetlands and drainage issues, eleven retaining and freestanding walls were required totaling 23,100 square feet (2,146 square meters). "There was 50-feet (15.2 meters) of grade difference across the site. This required significant cuts and fills," explained Jeff Benway, PE of SFC Engineering.
In addition to the site challenges, this project also faced a very tight construction schedule that needed to be completed over multiple phases.
Designers chose Redi-Rock to create the retaining walls for the project for several reasons.
Here's how the hospital used Redi-Rock walls throughout the new complex:
The hospital has two access points; one dedicated for emergency vehicles, and the other to all other traffic. The emergency entrance required Redi-Rock Cobblestone texture walls up to 15 feet (4.6 meters) high and up to 150 feet (45.7 meters) long. The main entrance required Redi-Rock walls up to 16.5 feet (5 meters) high and up to 270 feet (82.3 meters) long.
A stream runs through the property, which created unique challenges due to underlying soft clay soil where the road needed to cross the stream. "The steel arches for the bridge were on a pile foundation so settlement would be minimal, but the Redi-Rock walls on either side of the arches would be sitting on the natural soils. Settlement of these walls was anticipated to be up to two inches (51 millimeters)."
How did engineers solve the problem? "The blocks were laid out so that there would be a joint at each side of the arch. This would allow the side walls to move and not affect the walls on the arch," Benway explained.
Coordinating the walls with the arch required the precaster, Redi-Rock of Central Maine, to create special blocks to follow the curve of the arch.
An additional challenge for this portion of the project was creating a guardrail for the bridge. "The road needed to be as narrow as possible to limit the impact on the stream," Benway explained. "There was no room behind the blocks to put in a guardrail, so this necessitated the use of freestanding blocks with a poured-in-place concrete beam to act as a guardrail." Redi-Rock freestanding blocks were a great choice for this application. Weighing in at 1,345 pounds (610 kilograms) each, these reinforced freestanding blocks protect motorists and pedestrians.
Entrance and Detention Basin:
The most visible wall on the property stands at the main entrance of the hospital. This Ledgestone texture freestanding wall is a backdrop for the "Alfond Center for Health" sign. This wall stands 4.5 feet (1.4 meters) above grade and provides an aesthetic barrier on both sides. It is capped with a custom coping system to provide a coordinating look. The hospital chose colors for the wall to match the stone work throughout the complex.
On the back side of the entrance's freestanding wall lies one of the complex's detention basins. "This basin is somewhat unique in that it was at a relatively high point on the site with a significant slope below it. The wall was built to create an area for the basin on top of this slope. The wall 'hides' the basin from people driving up to the hospital and at the same time creates a nice entryway," Benway explained. On the basin side of the wall, a 4.5 feet (1.4 meters) tall retaining wall structure was designed to handle the anticipated 4.5. feet (1.4 meters) water rise.
"The wall had to be designed on the assumption that the basin would fill up, water would flow into the backfill and then the basin would drain out. The water behind the wall would then seep back into the basin or permeate down into the soil," Benway said.
Parking and Loading:
Creating parking areas and a loading dock also required extensive retaining walls. These areas utilized Redi-Rock Cobblestone texture blocks that were reinforced with geogrid.
"The tallest wall was up to 22.5 feet (6.9 meters) high and extended for 500 feet (152 meters). This wall had 10 courses of geogrid that extended 18 feet (5.5 meters) into the soil behind the wall," Benway explained.
The wall supporting the parking lot was only nine feet (2.7 meters) high, but had a 2:1 slope at its' toe. "Typically a wall of this height would be a gravity wall, but because of global stability issues a reinforced wall was necessary," Benway explained.
Redi-Rock has an extensive network of manufacturers across North America, plus Europe and Asia. This network was a benefit to this project's aggressive timeline.
"We were busy producing custom color Cobblestone walls for the main access road which was the primary objective of the project, so we requested assistance from Redi-Rock Walls of New England to meet the aggressive construction schedule for the Ledgestone freestanding walls," explained Carl Jordan of Redi-Rock of Central Maine. "Their cooperation was spectacular. They were excellent to work with and the cooperative effort was outstanding."
This project was the recipient of the 2013 Rocky Award for "Freestanding Wall of the Year" from Redi-Rock International. The Rocky Awards are an annual honor recognizing the best Redi-Rock projects completed each year across the globe.
Project: Maine General Hospital Entrance #165 Customer: Maine General Hospital, Alfond Center for Health Engineer: Jeff Benway, PE of SFC Block Manufacturer: Redi-Rock of Central Maine, Redi-Rock Walls of New England Installer: Sargent Corporation Location: Augusta, Maine Year Built: 2011-2012