Dec 09, 2003

Walls of Steel

Company recommissions wastewater lagoon when faced with time crunch

Fisher Tank Co.

3131 W. Fourth St. * Chester, PA 19013

Phone 610/494-7200

www.fishertank.com

DSM Chemicals North America, Inc., had to make a decision
fast. The company was about to open a new facility to recycle caprolactum from
used carpeting when management realized their 10-year-old wastewater treatment
plant could not handle the additional wastewater generated by the recycling
operation.

"We needed to increase our treatment capacity very fast
because we didn't want to block the recycling operation," said Reese
Bridges, maintenance manager for Augusta Service Co., DSM's service
organization.

One option was to erect another storage tank. Not only was
the cost a deterrent, time was running out. A second option was to reactivate a
1.5-acre onsite lagoon, which had been formerly used for wastewater treatment.

The good news--it was big enough to do the job--260 ft
diameter, 14 ft deep and a capacity of 10 million gallons. Moreover, all the
ancillary pumps, piping and processing equipment was already there.

The bad news--the walls and bottom, lined with one-inch
thick gunnite over a polyethylene liner had weakened. This was why the company,
rather than risk a leak, had taken the lagoon out of service years earlier.

"We figured it would be much more cost-effective,
saving perhaps as much as $1 million, to use the existing impoundment rather
than build a new tank above ground," said Bridges.

To help them make a decision, DSM sought the opinion of the
Fisher Tank Co., a builder of above ground steel storage tanks.

Management decided if the lagoon alternative were feasible,
they insisted the walls and bottom of the earthen impoundment be covered with a
leak-proof steel lining.

Steel belly

Contract Engineer Ron Liljegren and Operations Manager Jack
Whiting journeyed from Fisher Tank to the site to size up the project. They
worked out a budgetary price and, by the end of the week, Fisher Tank got the
go-ahead to proceed on the $500,000 project.

Within days, FTC's Liljegren, who served as project
supervisor, mobilized two, 10-man crews under foreman Tom Limperous. Working in
two, 10-hour shifts, Fisher Tank personnel began lowering the 8 ¥ 20-ft
carbon steel plates into the excavation and positioning them against the
embankment walls. Because specs called for a liner that was 100% steel to guard
against any possible leakage, Fisher Tank employed only continuous welding
along the seams and vacuum.

The underlying gunnite, with its polyliner, remained in
place, functioning as a secondary containment system in compliance with
environmental regulations. In the unlikely event of a leak, the secondary
system would drain the water through the bottom. For back-up protection, the
entire liner was coated with an anti-corrosion epoxy.

"They met all expectations and validated our decision
to use the old impoundment," Bridges said. "We haven't had any leaks
at all and no liner problems."

With the steel-lined lagoon online, DSM almost doubled its
treatment capacity.

Converting the impoundment increased the capacity by 4.5
million gallons, bringing the total at the site to more than 10 million
gallons. The new facility, like the other two tanks, handles about 850,000
gallons of water each day.

The wastewater has a residence time of only one day
throughout the plant before it is discharged it into a river, absolutely clean.

About the author

expand_less