Michigan, Super Fund, Remediation Project
In 2003, Dredging Specialists designed,
built, and operated a unique Slurry Mixing & Pumping System.
PCB contaminated mud was dredged from
White Lake with a Cable Arm clam bucket and placed in a scow. The
scow was pushed to a barge flotilla anchored at the shore. At the
shore, a hydraulic excavator with a clam bucket removed the mud from
the scow and placed it in highway dump trailers.
Highway tractors pulled the trailers on a
road to the Slurry Mixing & Pumping System. The trailers were
backed up and the mud was dumped into the sloping Slurry Mixing &
Pumping System tank. A 6 inch dredge pump circulated the mud as a
controlled amount of water was added. When the mud and water were
mixed to a pumpable slurry the dredge pump pumped the slurry in a
pipeline under a highway, for a distance of 1,000 feet, and into
Geo–Bags where it dewatered.
The system handled mud, sand, gravel, and
a large amount of wood debris without major problems. The two other
contractors on the project, the owner, and the environmental
regulatory agencies, were extremely pleased with the operation of
this system and the performance of Dredging Specialists' personnel.
Madison, Wisconsin Metropolitan Sewerage District
The Madison Metropolitan Sewerage District (MMSD) services industries and approximately
250,000 people. From digesters the sludge goes to 88 acres of settling ponds. The district
owns and operates a VMI auger dredge to remove sludge from the ponds. During 10 years of
dredging the district has removed approximately 560 million gallons of sludge at an
average of less than 4% dry weight solids. The sludge is transported, up to 15 miles, in
tank trucks and land applied on farm ground as fertilizer.
MMSD advertised for bids on the dredging work. The specifications
required the contractor to dredge 350,000 gal. per day at a minimum of 3% dry weight
solids. Below 3% there was a price deduction.
Dredging Specialists submitted an alternate proposal. Our
proposal stated that on any day we did not average 6% dry weight solids, there would not
be any charges. That's right, we would work for free! Above 6%, there was an adder for
each 1/10th of 1%. If we dredged 1-gal at 6%, others would need to dredge 2 gal. at 3% to
remove the same amount of solids from the pond. If we could dredge above 6%, we would cut
their trucking, land application, and overhead cost by over 50%.
The district said it was impossible. They cited their ten
years experience as evidence. They said we would move in, find out we could not average
over 4%. We would then move out because we had no income. The district said, "If you
want a contract, we want a $50,000 bond." Now here's the deal. If we couldn't perform
we would dredge for two months without income and lose our $50,000 bond on top of that. We
gave the district the bond and they gave us a contract. On the first day of dredging we
averaged 7.24%. During two months we never went under 7%. First month average 7.84%,
second month average 8.38%. Peak day was 11.05%.
The following are the reasons we were able to make this
proposal and succeed.
Our exclusive 4 cable propelling and positioning system,
which keeps the pump inlet in the sludge and not in water.
Our Design 8 Dredge Head and Underwater Pump. With mould
board to force the sludge into the pump inlet.
Knowledgeable and experienced leverman and other on site
We were the only contractors that recovered samples and
sounded the pond. Therefore we knew the percent solids that was in the pond and the depth
of sludge. This information and knowledge of our dredging capabilities permitted us to
make this challenging proposal and exceed even the expert's predictions.
By dredging high solids slurry, Dredging Specialists
saved MMSD over $252,000 in trucking, land application and overhead costs on a two-month
contract. The saving was over and above the $50,000.00 bonus we received for solids above
Weeks Marine, Inc./City Of Philadelphia, PA
Dredging Specialists was contacted by Weeks Marine Dredging Division
of Camden, NJ. (Weeks is the #2 dredging contractor in the US) The
project consisted of removing 550,000 cu. yd. of ferric chloride and
river settlements from a settling pond at the Baxter water treatment
plant in Philadelphia, PA. The material was to be dredged into
4000-cu. yd. bottom dump hopper barges anchored in the Delaware
River. The barges would be towed 26 miles, down river, to a
permitted dumpsite. The barging required that the material be
dredged at high percent solids and with a minimum of carriage water.
Dredging Specialists had been recommended to Weeks Marine as a dredge builder and
contractor that could fulfill the high percent solids and minimum carriage water
requirements. Dredging Specialists entered into a contract with Weeks Marine to design,
build and operate, a purpose built, hydraulic dredge specifically for this project. The
Dredging Specialists exclusive 4-cable propelling
and positioning system
Our Design 8 Head and Underwater Pump and other features
to assure a high percentage of solids.
Specifications on the dredge Norma Lee II are: · 70,000
pounds · 60-ft. long · 20-ft. wide · Powered by a 420-hp. Cat diesel engine. The Norma
Lee II was designed and built in less than six months.
The project was completed within the specified time.
Dredging Specialists met the high solids requirements
necessary to make barging of the material cost effective.
Turbidity requirements were met without the use of any
turbidity curtains. Including when dredging within 50-ft of the cities water intake.
The Weeks Marine method of disposal along with Dredging
Specialists ability to dredge high solids material, with a minimum of carriage water saved
the City of Philadelphia over $7,000,000 on this project.
E. I. DuPont
Specialists received a call from Dave Smith, engineer at the E. I. DuPont, Seaford,
Delaware Nylon Plant. Dave explained that they had titanium hydroxide sludge with the
consistency of cheese, and percent solids of over 50. The sludge was in two fabric lined
ponds that measured 200-ft. X 200-ft. The ponds were 8-ft. deep. The material needed to be
removed, placed in tank trucks and transported 100 miles to the DuPont Deep Water, NJ
Wastewater Treatment plant. Prior operations by contractors had yielded slurry of 4%
solids or less. DuPont wished to raise the percentage of solids and thereby decrease their
Dredging Specialists recovered
samples of the sludge and made tests to determine the best methods to slurry and pump the
Dredging Specialists then made a proposal to design,
build and operate a system that would remove the sludge at 16% to 20% solids. After a
detailed review of the proposal by the DuPont engineering and purchasing departments a
contract was issued. Dredging specialists has operated the system on four contracts. The
average percent solids has been over 17%. DuPont has realized savings of over 75% on their
During one of the contracts we experienced high levels of
hydrogen sulfide gas. The levels exceeded 150 parts per million and were higher than
acceptable at the DuPont Deep Water Treatment Plant. Due to the high sulfides, the project
was shut down.
DuPont did not have any solutions for the sulfide gas
problem. With the project shut down, our income was cut off. This caused us to "get
on the ball" and figure out the solution. Three days after project shutdown, Dredging
Specialists had designed, built, installed, and tested a sulfide stripping system that
lowered sulfide levels from over 150 PPM to less than 5 PPM with only 15 minutes of