Clarksville, TN – This is the latest report the Clarksville City Council has received on the College Street Repair Project from the engineers involved. The sinkhole was first discovered on July 15th 2011 at the intersection of College Street and North Second Street, when the roadbed began to cave in. The intersection has been closed since that time.
The Progress Report begins below.
The deep excavation has been slowed recently by significant deep rock excavation and frequent mud seams, but our work has progressed fairly well to date. We had a moderately productive week last week and a very productive day yesterday. Today we hit another sink hole, making it four (4) holes to date within approximately 200 linear feet of excavated trench.
The good news is that we have fully excavated below the AT&T duct banks now and expect to have the new 66″ pipe laid beyond the ducts by late tomorrow. This has been a significant milestone for the project.
We expect to complete the remaining deep excavation, set the second junction box, and finish the 66″ pipe installation by the middle of next week.
There is still a significant and sizable sink hole east of North 2nd Street to deal with before completing the deep pipe installation. Once we get the deep excavation and pipe laid, we can focus on re-establishing all the shallow utilities and infrastructure that has been affected by the emergency repairs.
The Tennessee Department of Transportation has been very timely in furnishing the No. 57 stone and surge stone that we need for backfill. They are also cooperating with me fully in securing the other materials such as shallow storm drain pipe and junction boxes that are needed to complete the storm drain portion of the work. They are also eager to assist with the engineering staking of the subgrade that will be required prior to their repaving the streets.
The City of Clarksville’s traffic control as well as our onsite security has been effective in minimizing unsafe access to the site by the public, while still being sensitive to the needs of the local business owners, and in particular the University Package Store and Insta-Cash establishments along the corner of North 2nd Street and College Street. The Street Department, and in particular Mr. Jack Frazier has been routinely involved with site visits and assistance with sinkhole remediation. Gas and Water Engineering and Operations staff has been very helpful and accommodating our schedule and immediate requirements with regards to isolation of affective utilities and timely decision making. We are currently working with Gas & Water Engineering staff on effective plans for isolation of the sanitary sewer and storm piping along the limits of our project, not to mention finalizing plans for water and gas main replacement.
I have attached a few photos from today for your review (due to file size one photo is included in this article for your review). To give you a little perspective, the bottom of the steel beam (AT&T duct bank support) in the photo is approximately 10′ below existing finish grade and the approximate depth of excavation below this beam is 25′. It is also quite interesting to see that the original brick sewer was apparently hand tunneled through both solid rock and mud seams. This was not the case along 4th street as we discovered approximately 10 years ago in a separate emergency excavation and repair. The 4th Street portion of the existing brick sewer apparently had been excavated by conventional trenching in that all the rock above the pipe had been blasted or otherwise previously excavated.
The AT&T duct bank has also presented different kinds of challenges, but all AT&T staff we have dealt with thus far has been very effective and timely with assistance and direction. They have also agreed to share some of the expenses of the work around the duct banks to keep their customers and service from being interrupted during the repairs. In effect and in fairness to the City, we discussed with AT&T the extra work required to keep ducts in service that should not be billed to the City and they have accordingly agreed to compensate us for such extra work which in turn will not be billable to the City.
This project has certainly been the challenge in subgrade diversity that we expected, but we are confident in what we have completed thus far and that we have the tools, experience and expertise to complete the remaining work effectively and efficiently.
