Over 500,000 cubic yards of soil has been treated
By Aram Kalousdian
The majority of fill needed on a site near Edwardsport, IN where a coal gasification plant is under construction, is extremely wet and highly plastic clay. There is no time for suspending work due to weather or soil conditions.
In order to counter the problems that soil conditions and weather pose, Mt. Carmel Stabilization Group Inc., of Mt. Carmel, IL is using Lime Kiln Dust (LKD) to dry and modify massive stockpiles of cut that can later be used as fill for the site. To date, Mt. Carmel has treated over 500,000 cubic yards on the project with over 40,000 tons of LKD and has helped to keep its customer, Ryan, Inc. Central on schedule throughout the difficult fall, winter and spring months. Ryan, Inc. Central is the excavating company for the project. Duke Energy Corporation is the project owner.
Coal gasification plants convert coal into a synthetic natural gas that’s processed to remove pollutants such as mercury and sulfur dioxide. The plant under construction will use a methanation process to produce pipeline quality substitute natural gas (SNG), which has an identical molecular structure to that of natural gas. It is expected to produce 40 billion cubic feet of pipeline quality SNG annually, which is enough to supply 15 to 20 percent of Indiana’s residential and commercial gas demand. Its use is expected to save consumers more than $3.7 billion over the next 30 years versus the price of conventional natural gas, according to a study by Carnegie-Mellon University faculty.
The plant will operate with extremely low emissions of regulated air pollutants and will isolate carbon dioxide so that it can be captured.
The project is being constructed on a 200-acre greenfield site. There is approximately 1.8 million cubic yards of earthwork on the project.
“Ryan, Inc. Central had a lot of dirt to move. There is a lot of cut and fill. The material is somewhat silty and very wet, so lime was put into the bid in order to keep the project moving along,” Doug McPherson, vice president of Mt. Carmel Stabilization Group Inc. said.
“We saved Ryan, Inc. Central months on its schedule. Ryan, Inc. Central’s dirt work schedule would not allow the company to miss one or two weeks let alone months. The entire winter would’ve been lost, based on the soil conditions out there, the temperatures and the wet spring that we had,” Neil Ryan, marketing manager for Mt. Carmel Stabilization Group Inc. said.
McPherson explained that LKD not only attracts water and needs water in order to react, but it creates heat during the reaction as a thermal exchange, which dries additional moisture. “So, you get the benefit in the winter of not only moisture reduction, but heat in order to keep the material from freezing,” McPherson said.
“They tried to get by without lime for quite sometime, but then when we got out there and did a test strip, they saw what it could do. The rest is history. We’ve been working there for several months.” Mt. Carmel Stabilization Group Inc. began working on the project in the fall of 2008. The company has been working on the project on an as-needed basis.
“A lift of material that is very wet is brought in and we place LKD on it in order to dry it. We blend it and get a good homogeneous mixture of soil and lime in order to take out the moisture. We are actually changing the characteristics of the soil,” McPherson said.
Mt. Carmen Stabilization Group points out that if a site is properly stabilized wet weather will have virtually no effect on the final condition of the site. In fact, many project owners stabilize their sites to help protect against construction and weather damage over a winter season prior to final surfacing.
Six-wheel drive Mack tandem trucks that have spreader boxes on the rear are being used on the project in order to spread the LKD material on the ground. The spreader boxes have dust collection systems on them in order to limit the amount of dust on the project. The material is then mixed in place with a Wirtgen WR 2400 recycler/stabilizer and a Cat RM 350 reclaimer. These soil stabilizers pulverize the soil 16 inches deep so that the lime and soil is blended together.
The Wirtgen WR 2400 is suitable for all kinds of terrain. The machine features a 420 horsepower engine. Its lifting column design with hydrostatically and individually driven wheels provides ample ground clearance and enables the machine to work with the desired longitudinal and cross slope. A hydraulic differential lock additionally provides the WR 2400 with optimum traction properties.
The Wirtgen WR 2400 is equipped with hydraulic all-wheel steering, enabling it to be maneuvered easily even in extremely confined conditions. An elevated position prevents the working cylinders from getting soiled, which ensures improved operational readiness. The machine’s chassis remains clean, as it does not come into contact with the soil to be stabilized.
The volume of the mixing chamber on the WR 2400 increases automatically in accordance with the current working depth. The rotor can be raised and lowered continuously. In the final analysis, the design provides a consistently homogeneous mixing quality.
The Cat reclaimer’s rotor options provide versatility for stabilization and reclamation applications. The load-sensing propel system helps prevent overloading while allowing continuous work near the rated horsepower.
The Cat reclaimer provides consistent blending due to automatic depth control, a mid-mounted mixing chamber and a multi-speed rotor drive. Excellent maneuverability and operator visibility to the tire edges and mixing chamber allow the machine to perform well in urban environments. Daily service points are accessible from ground level and grouped on one side of the machine.
This article appeared in the July 2009 issue of Construction Digest, an ACP publication