Testing will precede grout project

Grout removal from the Washington Avenue tunnel will not begin until a “simulated” test is conducted at a distant site, according to city engineer.

Ralph Swenson said the simulated hydraulic/water jet test is expected to be conducted even before plans are drawn up by a consultant for the specific removal of the grout causing blockage in the tunnel.

Swenson said that the test will be done to “see if the process works ... before we go out to bid on the actual [work].”

On Nov. 2, the Common Council voted 8-0 to borrow $150,000 to pay for the design of a project to remove grout that’s blocking the Washington Avenue sanitary sewer system, as well as to fund ongoing rental fees for a pump system to temporarily bypass the clogged section of pipe. The design is expected to be drawn up by the engineering firm Clark Patterson Lee.

Of the funding, $100,000 is to pay for designing the repair project, which would use a high-pressure water jet with a rotary cutting tool to remove the grout. It also would pay to solicit bids from companies that could perform the repair project, which is expected to cost more than $1 million.

The remaining $50,000 would be used to pay for the bypass pumping system.

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.

Timothy Moot, a principal with Clark Patterson Lee, told the Common Council’s Finance and Audit Committee last month that the high-pressure jet repair was one of several options his firm explored and that it probably will cost between $1.1 million and $1.3 million.

The city previously tried to jet the grout out of the pipe but did so from a greater distance than now is being proposed, Moot said. He said the closer the equipment is to the blockage, the more pressure can be generated.

Swenson has told the Finance and Audit Committee that it costs the city about $7,250 per month to rent the bypass pump. And he said money the council previously approved for the rental is nearly exhausted.