Luedtke Engineering Company is using a state-of-the-art bucket positioning system in a project to remove PCB-contaminated sedimentation from the Saginaw River and Saginaw Bay Michigan.
The project is part of a $28.5 million settlement between agencies in the State of Michigan the United States of America and the Saginaw Chippewa Indian Tribe and plaintiffs General Motors and the cities of Saginaw and Bay City Michigan for discharging PCB’s (polychlorinated biphenyls) into the Saginaw River. $10.9 million has been earmarked for dredging with the remainder to be used for habitat restoration for fish and wildlife in the Saginaw Bay watershed. Luedtke’s contract with the Corps of Engineers is for $6464450. Kurt Luedtke company president prepared the bid which required assembling high-technology precision dredging equipment for the contract entitled Environmental Dredging Saginaw Bay and River Michigan.
The GM plants GM Powertrain of Bay City GM Gray Iron/Nodular Iron (now Saginaw Metal Casting) and GM Malleable Iron of Saginaw used PCB’s as a fire retardant in their cooling oils in the 1950’s and 1960’s and discharged through the wastewater treatment plants of Bay City and Saginaw Michigan. At that time the government encouraged use of PCB’s for this purpose said Gerry Holmes General Motor’s director of media relations for facilities and community impact. In the 1970’s it was found that PCB’s did not break down that they settled into sediment drainlines and pipelines and that they might be carcinogenic in humans. Use of PCB’s was outlawed at that time and the GM plants stopped using them.
In 1994 the State of Michigan sued GM in state court for PCB contamination of the Saginaw River and Saginaw Bay. As the case moved through the settlement process the parties lodged the consent judgement in federal court to encompass all parties involved which expanded to include the state of Michigan the United States Fish and Wildlife Service and the Saginaw Chippewa Indian Tribe against plaintiffs General Motors and the cities of Saginaw and Bay City.
On November 24 1998 the $28.2 million settlement was signed the largest resolution of natural resources damages awarded to date in Michigan. The money was put into an account for the sediment cleanup and land and shore-based mitigation projects. $10.2 million was allocated for he dredging project. The remainder was set aside for land acquisition.
Five PCB “hot spots” were located in the Saginaw River and Saginaw Bay comprising about 350000 cubic yards of contaminated sediment. The Detroit District Corps of Engineers managed the project writing the plans and specifications and bidding and managing the project.
Bill Rito is project manager in the Contract Administration Branch of the Corps Detroit District. Because the dredging was outside the federal shipping channel the Corps required a Section 10 dredging permit which was issued after an environmental assessment report was completed for the disposal portion of the project. The Corps prepared the plans and specs with the aid of the Michigan Department of Environmental Quality which had taken hundreds of borings in the area to identify the hot spots. The Corps took additional borings mainly to identify the type of material which is a silty sand said Rito. The PCB’s adhere to the small silt particles and lodge between the sand particles he explained.
The plans and specs for IFB DACW35-99-B-0005 were issued on February 11 1999 and stated that “the method of dredging shall be by mechanical means using an environmental bucket except in Area Three (outfall area) where a hydraulic dredge can be used. The environmental bucket shall be a gasketted clamshell or similar design Cable Arm or equal with a proven field performance record which shall preclude loss of material between point of excavation and placement in scows.”
The execution section of the plans described the required dredging cycle in detail:
“In order to reduce turbidity the contractor shall 1. swing to dredge location; 2. slowly lower fully opened bucket at dredge location; 3. stop at required vertical depth cut line as signaled by position equipment; 4. close bucket; 5. confirm bucket closure via visual signal; 6. slowly lift bucket; 7. stop at water surface and allow excess water to drain; 8. swing the closed bucket into position over disposal scow; 9. slowly open bucket to fully discharge spoils (sic); 10. wash bucket in wash tank; 11. repeat cycle.
Luedtke Engineering Company was low bidder in a field of five bidders and was awarded the contract DACW35-99-C-0038 on September 21 1999. By the middle of April 2000 they were on the job with their Derrickboat #16 a Clyde 28 crane with a 55000 pound line pull. The bucket is a 16 cubic yard Cable Arm Clamshell custom-designed for this job.
The bucket is 18 feet wide with a 16-foot span when open. Ray Bergeron president of Cable Arm Clamshell uses lightweight high tensile strength steel so this 6.5 cubic yard bucket weighs 20000 pounds.
Instrumentation on the bucket includes two pressure transducers that indicate water depth; two Simrad altimeters that measure the amount of sediment entering the bucket to eliminate overflow; two closing switches one on each end of the bucket so if an obstruction in either end keeps the bucket from closing the operator will know; and one opening switch. The ClamVision software provided by Cable Arm records and logs all the data from the sensors along with boom angle and swing of the crane and tide information from a Hazen Tide Gauge.
Lyman Burk produced a custom dredge and bucket positioning package especially for this project. Three DGPS receivers are mounted on the dredge to provide a scaled true geodetic image of the dredge boom and bucket for the operator to use in real time. The modification of Burk’s WINOPS positioning software gives the operator a radial dig pattern superimposed over the dredge image that allows the operator to position the bucket precisely over each bucket target. (See cover.) A tide/wire function that Burk calls the “Langdon feature” after Brian Langdon field manager for A.H. Powers Inc. who suggested it shows digging depth and tide and plainly displays the wire length needed for that tide eliminating the need for the operator to constantly calculate the correction for tide. Several cuts are needed from each target to reach grade said Tom Zatkovic project manager for Luedtke Engineering.
Other features of the WINOPS are the GPS-based geodetic system NAD 83 a parameter function that puts all information from the job in one file. This includes information such as hardware interfacing channel crosscuts color coding job number and date.
“This is one of the reasons for my success” said Burk. When a technician goes into the field he or she has all the information on the project on one disk so nothing is missing.”
The software gives a two-foot overlap on each cut and a two-foot athwartships overlay when the dredge moves to a new pattern assuring complete coverage of the dredging area said Burk.
The dredging cycle can be as long as five minutes said Tim Kibby project superintendent for Luedtke. The operator lowers the bucket into the material watching the gauges as it closes taking a level cut off the bottom. When he ascertains that the bucket is fully closed he raises it slowly then allows the excess water to drain after it breaks the surface. If the bucket is not fully loaded this may take time but if the bucket is fully loaded there will be no runoff. He then swings to the side where a deck barge is moored. This barge has been fitted with watertight sides approximately six feet high. He releases the load onto the barge then swings to the stern of the dredge and dips the bucket into a water-filled scow to rinse it. He then swings into position to take the next cut. The cycle time averages two to three minutes but can be as long as five minutes depending on time necessary to decant the water from the bucket said Kibby. Digging depth is from five to 24 feet.
The material is placed on a dredged material disposal island in Lake Huron a mile offshore three to four miles from the project site. The round trip is 2 ½ hours with an unloading time of six hours. Derrick boat #10 with a 4000 Manitowoc crane uses an eight cubic yard Cable Arm bucket to load the material into trucks which move it into the interior of the island. By the time the scow returns to the dredge the other one is almost filled so there is no downtime waiting for scows. The tug Kurt Luedtke is used to move the two scows while the tug Karl E. Luedtke is the dredge tender.
The project is run in two 12-hour shifts six days a week. The shift foremen are Les Morr and Don Mills. Four Corps of Engineers inspectors are on the job six days a week at the dredge and at the disposal site. The job is weather-dependent. High winds can prevent the tug and scow from travelling across open water to the disposal site.
The Saginaw River has a 200-foot-wide shipping channel which is used by ore and cement ships that ply the Great Lakes. Because this project is outside the channel there is little downtime due to avoiding ship traffic.
The dredging area is completely enclosed in a silt curtain which is deployed in a U pattern against the bank. The Elastec/American Marine rough water screen is in 100-foot lengths linked together in depths varying from 10 to 29 feet with a reefing system to shorten it if necessary.
The curtain crew headed by foreman Richard Arnold uses several boats and a barge with a small hydraulic crane to set anchors and move and deploy the curtain. When the project began the silt curtain enclosed an area 100 by 250 feet and at the beginning of June the area was 200 by 1200 feet.
The survey boat does the layout for the curtain crew. The 26-foot MonArk tri-hull aluminum boat is equipped with a Raytheon Fathometer using an Odom Digitrace to digitize the soundings. It is integrated into Hypack software and positioning is by a Starlink 212 D-Nav GPS system. Computations are on a Dell computer.
The contract includes turbidity testing six times every 24 hours. Luedtke performs the tests under Corps supervision. The air quality was tested on the first five days of the project.
Other environmental mitigation funded by the settlement includes restoring and protecting wildlife habitat in the area which is one of the premier walleye and waterfowl locations in the Great Lakes area. It includes acquisition restoration and protection of more than 1600 acres of habitat which will be owned and managed by the State of Michigan the Fish and Wildlife Service’s Shiawassee National Wildlife Refuge and the Saginaw Chippewa Tribe. The tribe while happy with the dredging and other habitat restoration and protection views the settlement as a compromise after a terrible loss to Native Americans. Frank Cloutier public relations manager for the tribe said that the contamination “cost our people and history a tremendous amount. We are as satisfied as we can be with the dredging and the other cleanup but the land can never be restored to its natural state.” A 10+-acre parcel of shorefront land adjacent to tribal land near Standish Michigan was given to the tribe and this will be set aside forever as wildlife habitat protected from development and human incursion he said. The tribe had no interest in receiving any money from the settlement said Cloutier.
Restoration is planned for acquired lands that were drained for agricultural use for fish habitat between Saginaw Bay and Tobico Marsh and for the Green Point Environmental Learning Center in Saginaw. Boat launches and nature-viewing opportunities will be provided at two sites on the river in Bay City and at one site on Saginaw Bay near Essexville.