Committee backs million-dollar fix for grout problem
KINGSTON >> A Common Council committee favors pursuing the use of a highpressure water jet with a rotary cutting tool to remove grout blocking the Washington Avenue sanitary sewer system, an effort that’s expected to cost more than $1 million.
The Finance and Audit Committee voted Wednesday to borrow $100,000 to fund the design of the repair project using the water jet, as well as to solicit bids from companies that could perform the work. The committee also endorsed borrowing another $50,000 to pay ongoing rental fees for a pump system used to temporarily bypass the clogged section of pipe.
The borrowing must go to the full council for approval. The council next meets Nov. 1.
The grout blockage occurred during the project to repair the sinkhole that opened on Washington Avenue in April 2011. During the repair, grout somehow penetrated a new sewer lining, blocking a portion of the pipe.
The city still is looking into how that happened and who is responsible for the blockage.
Timothy Moot, a principal with Clark Patterson Lee, said Wednesday that his firm had been hired to look at options for removing the grout from the sewer line. He said the firm considered using a directional drill to go through the grout, but that option was risky because the drill could deviate out of the pipe entirely. Moot said the firm also looked at installing a new access shaft in the system, which would be the most costly option at $1.7 million to $2.1 million.
High-pressure jetting was the option recommended, with the cost estimated between $1.1 million and $1.3 million, Moot said. He said the city tried to jet the grout out previously but did so from a greater distance than now proposed. The closer the equipment is to the blockage, the more pressure can be generated, Moot said.
“The vendor of the equipment is pretty certain that it can annihilate that grout that’s in there because it’s not really structural concrete,” he said.
City Engineer Ralph Swenson said the previous attempt was unsuccessful because the pressure and horsepower of the equipment were too low due to the remoteness.
That attempt was made from an access point on Elizabeth Street.
Moot said whatever contractor the city chooses could access the blockage from the Tannery Brook shaft, which is close to the affected portion of the tunnel. He said it would take six to eight weeks for the project to be completed and would require a portion of one lane of Washington Avenue to be closed. Moot said the project would involve bypassing the sewer during the work, as well as getting water out of the tunnel.
If the high-pressure jetting does not work, the city would need to consider installing a new shaft, Moot said.
Moot said once the blockage is removed and the tunnel is cleared of debris, the city could consider some long-term options for improving the safety and condition of the overall tunnel system.
As for the bypass pump, Swenson said it costs the city about $7,250 per month to rent. He said money the council previously approved for the rental is nearly exhausted but the new funding will cover the rental for the next several months.