Slope failure repair to Lake Resort Drive expected to begin in October, cost less than initial estimates

Staff photo by Doug Strickland / A portion of Lake Resort Drive is reduced to a single lane following damage to the roadway, seen here on Thursday, May 23, 2019, in Chattanooga, Tenn.
Staff photo by Doug Strickland / A portion of Lake Resort Drive is reduced to a single lane following damage to the roadway, seen here on Thursday, May 23, 2019, in Chattanooga, Tenn.

Repairs to Lake Resort Drive's slope failure may come in significantly below the estimated cost.

According to a presentation to the Chattanooga City Council by city Department of Transportation Senior Engineer Katie Snyder, preliminary design estimates for repairs to a major slope failure on Lake Resort are around $5 million, a cut of about $4 million from the estimate provided in May.

"The original preliminary estimate of $9 million was a conservative estimate," Snyder said in an email Friday. "The current estimated repair cost is $5 million and this will continue to be refined as the design is finalized."

PROJECT TIMELINE

Notification of slope failure: Feb. 23, 2019City staff monitoring of site: Feb. 23 2019 and ongoingInitiation of emergency contract: March 6, 2019Lab analysis of samples and field data analysis: April 2019Preliminary design development: April-May 2019Detailed design development: May-July 2019Advertise for bid: August 2019Begin construction: October 2019Construction completed: June or July 2020

The stretch of Lake Resort has been down to a single lane of traffic since Feb. 24 when about 800 feet of the eastbound lane dropped by nearly 8 inches due. It is one of four city slope failures caused by 10 inches of rainfall in 10 days in February.

After enlisting the services of Geosyntec Consultants Inc., Snyder said the city has identified a shift in the entire hillside of the affected area, caused by the presence of bentonite clay.

"It's a material that, when it becomes saturated, effectively works like WD-40 and everything on top of it moves," Snyder said to the council. "So we think this is likely a mechanism for why the slope is moving."

According to Snyder, CDOT came up with several potential repair options, but only three that would accommodate traffic and repairs: a secant pile wall (which was estimated to cost $11 million), a bridge (which was estimated to cost around $7 million) or a soldier pile wall with anchors (which was estimated to cost around $5 million).

"It's a very fiscally responsible approach," Snyder said. "It has the advantage that if that entire hillside goes, the wall will still be here and so will our road."

Once estimated at $9 million, the Lake Resort project has been the city's priority due to its potential for further damage and impact on traffic.

"We don't know if it's going to move another six or eight inches in a week or if it's going to stay put for a week it's just our geology," Snyder said in May, explaining that the design will aim to prevent future failure at the volatile site."It is a top priority for us to try and maintain traffic through there as best we can. But paramount to that is public safety."

Snyder said the transportation department will continue to monitor the area for shifts, as it has weekly since February, and will make the most prudent decision on road closures closer to work time.

The city expects to button-up the design phase this summer in time to put the project up for bid in August, hoping to begin the roughly eight-month construction project in October.

Preliminary work on three other slope failures on Hamill Road, Elder Mountain Road and Wilcox Boulevard is underway and construction should begin within fiscal year 2020.

To repair for sudden road problems, the city is seeking and well into the process of receiving around $20 million in federal emergency road funding from the Federal Emergency Management Agency and the Federal Highway Administration.

Contact Sarah Grace Taylor at staylor@timesfreepress.com or 423-757-6416. Follow her on Twitter @sarahgtaylor.

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