The major freeway project now underway in downtown Chattanooga included a herculean effort to stabilize the adjacent side of Cameron Hill.
Julie Alcantara, of the Volkert engineering firm, told members of the Chattanooga Engineers Club on Monday that a major shoring up began in May of last year after it was found that the side of the oft-disturbed historic hill was not so stable.
"There was a hodge-podge of material on the hill," she said.
She said crews worked 24 hours a day, six days a week, for six months drilling over 2,600 holes. Some were as deep as 120 feet. The holes were then filled with grout.
It took another six months of day shift work on the hillside stabilization until the project was finally finished in June.
Ms. Alcantara said, as part of the stabilization of Cameron Hill, a retaining wall is being built all the way from the Olgiati Bridge to Sixth Street. It will be 1,600 feet long. The wall will be 65 feet at its highest point.
Almost 900 "anchors" are being installed on the complex project, and this work is about one-third through. They go down from 100 to 120 feet.
The speaker said the project, which includes building 33 retaining walls, is being conducted "in a really tight area." TDOT acquired only two businesses along the route, keeping mainly within the established US 27 bounds.
She said at one point the roadway is only a few feet from one of downtown's oldest industries, Eureka Foundry.
One problem encountered was foundry sand, which is considered environmentally hazardous and had to be safely removed. She said contractors expect to find more foundry sand as the project goes forward.
Ms. Alcantara said the construction firm, because of the unforeseen problems that were encountered, got a six-month extension to complete it. It is now due to be finished by Jan. 28, 2020.
The work began soon after the contract was awarded to Dement Construction in November 2015.
It is now in the second of four phases.
She noted that the exit for northbound traffic to the Convention Center at Carter Street is now in use. Drivers are also able to use new northbound lanes, while the work shifts to the median area. The next phase after that will focus on the southbound lanes.
The project will remove the S Curve near the Olgiati Bridge and add a new southbound collector road going near the First Baptist Church from Fourth Street to MLK Boulevard. There will also be a flyover ramp at MLK.
Design of the project began in 2006 when it was estimated to cost $85 million. It came in at $126 million. She said, not counting the addition of two lanes on the Olgiati Bridge ($18 million), the price is about the same for the downtown part as it was for the work between the bridge and Signal Mountain Boulevard.
She said when the freeway was built in the 1950s it was designed for 15,000 to 20,000 vehicles a day. It now carries over 73,000 vehicles per day. She said over 26,000 use the Fourth Street exit and 20,000 the MLK exit.
In addition to all the retaining walls, the work includes 10 new bridges.