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Soil Stabilization With Grout
“Grouting commenced in an alternate pipe (staggered) sequence, and from top to bottom,” Dickes said. “Specifications required three grouting passes. Each pass on each pipe required about 160 individual episodes -- that’s 11 pipes, 160 ports and three passes for nearly 5,280 grout episodes. The first pass required 30 gallons per port, the second pass seven gallons, and the third pass, between three and 10 gallons. In total, nearly 80,000 gallons of sodium silicate were pumped.”
The grout plant operation included three 3,000 gallon storage tanks, two sets of dual grout pumps, two transfer pumps and two mixing pumps.
Dickes said crews faced two major challenges.
The first occurred shortly before operations began when equipment planned for the project became unavailable. Working together, team members assembled necessary equipment and parts.
“The second challenge was changing ground conditions for installing the SPPs,” Dickes said. “Upper ground conditions were sand/gravel making SPP installation easy. The lower ground conditions included larger stone and required the change to steel sleeve port pipes.”
Grouting operations required eight weeks. Northeast Remsco installed the 72-inch PCCP outflow pipe in late fall 2010, and tied it into manholes located at each end of the tunnel.
When completed, grouting reduced water infiltration into the tunnel from 60 to 80 gallons per minute (gpm) to less than 5 gpm.
There was no appreciable settlement of the railroad track, meeting the less than one-half-inch specification.
The Constellation Group is a construction consulting business and has worked on numerous major projects in the United States, Canada and Spain, providing expertise in helping contractors self-perform specialty tasks, such as on this project. Dickes has 30 years experience in the construction field.
Established in 1956, the Somerset Raritan Valley Sewerage Authority is located in Somerset County, NJ, and serves seven communities: Branchburg, Bridgewater, Hillsborough, Manville, Raritan, Somerville and Warren. The authority operates a 21.3 mgd secondary wastewater treatment system with sludge managed with a fluidized bed incinerator.
In addition to processing wastewater, the authority accepts graywater, septage and sludge.