Adjusting to Tight Places, Remediation in Trumbull, CT.

Remediation project in Trumbull, CT challenges contractor due to limited space

Being the proud owner of a Grove TMS760E certainly helped recently when AMCO co-owner, Anthony Clark found himself in a tight space.

AMCO was recently hired to help furnish the shoring for Petroleum Services, Inc. (PSI) – a company providing remediation work on a small gas station in Trumbull, CT. Gasoline tanks had leaked and contaminated the soil on the site.

Seen here is the Grove TMS760E - a 60 ton capacity hydraulic truck crane. Next to the building, the Foster 1050 vibratory hammer is being suspended by the crane cable and is being used to drive the sheet piles. In the foreground, is Tom Feeny attaching the wale to the sheet pile. The man in the background is Russ Marchildon directing the operation of the vibratory hammer. The vibratory hammer is being operated via remote control by Derek George who is not seen in the picture.

Due to site space limitations, this project is being phased in three parts. The project is currently in Phase I, which consists of the building of a cofferdam approximately 36-feet by 60-feet, dug to depths of 17 to 22 feet.

“We went in and installed the system so that PSI can remove the contaminated soil and replace with clean soil,” Clark said. “We had a unique system that has an up and down wale system that allows us to do any size hole.”

In order to facilitate the work and prevent cross contamination between cells, the sheet pile wall, common to adjacent phases, will be left in place until remediation is complete on both sides.

Petroleum Services (PSI) Kobelco SK350 is seen here excavating the soil from within the cofferdam and digging to a level about 12 feet below grade. When this level is attained, AMCO will return and install the lower wale systems. These will brace the lower sections of the sheet piles. The pictures show how the Kobelco was modified to provide a 45-foot reach. The original bucket was removed and an attachment was added to the stick. This attachment allows for the quick connection of the extension. It is better than the usual long stick in that the digging capacity is not reduced very much and it allows for better access in tight areas.

“The sheet piles along the front of the building will be left in place permanently upon completion of the work,” said AMCO Project Engineer, Jay Kaknes. “This will limit settlement, if any, to a minimum. In this case, a ledge was encountered at depths ranging from 17 to 22 feet. The sheet piles are being driven to refusal.”

In order to install the cofferdams, the existing pavement and canopy were removed. Trenches of not more than 4-feet deep and about 8-feet wide were excavated before the shoring was installed.

Kaknes explained that during Phase I, the wale system was installed and the sheet piles were driven against the wales. The sheet piles were then attached to the wales and PSI began the excavation process.

“PSI will dig to about 12-feet deep and AMCO will then install the lower wale systems,” Kaknes said. “PSI will then complete the excavation and backfill to the bottom of the lowest wales. AMCO will then remove the lower wale systems. PSI can then backfill to the bottom of the top wales. AMCO will remove the top wales.”

Kaknes said the wales and the sheet piles from one 36-foot long wall and one 60-foot long wall will be re-used to construct the Phase II cofferdam.

“Additional sheet piles and wales will be brought to the site as needed,” Kaknes said.

An AMCO tractor trailer hauling the 60 foot and 36 foot long wales.

“The process then repeats itself for the remaining two phases. The cofferdams for phases II & III will be similar to phase I.

In phase III the cofferdam will be used to remediate the site as well as to install the new 6,000 gallon and 12,000 gallon double wall, fiberglass underground storage tanks.

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