J.F. Brennan Uses 335,000 Cubic Yards of Aggregates For Capping in Little Lake Buttes des Morts
The sand is channeled to two spinners that spread it evenly over still water.
One of two spreader systems Brennan developed for precise placement of caps on the Fox River PCB cleanup job.
On the barge, dewatered gravel moves to the dual spinners.
At the land staging area, a load of sand and gravel is delivered from one of two aggregate producers, and a loader places material in the hopper for slurrying and transport to the spreader barge.
Gravel is delivered to the slurry tank by conveyor.
The banks of the Fox River hold the largest collection of paper mills in the world. From 1957 through 1971, these operations discharged 25,000 pounds of PCB’s into the river – a legal activity at the time, and accepted practice by manufacturers throughout the world. Upon identification of PCB’s as a carcinogen the discharge stopped, and the area is now a Superfund cleanup site. The OU1 cleanup took six years and was completed in June. By July, OU 2-5, consisting of 39 miles of river to its mouth in Green Bay, had begun. The second stage is expected to take 10 years.
The paper mills who are financing the cleanup include: WTM1 (formerly Wisconsin Tissue Mills), P.H. Glatfelter Co., Appleton Papers Inc./ NCR, U.S. Papers, Riverside Paper Company and Georgia-Pacific.
The capping was accomplished with two specially-designed spreaders that placed the material to accurate depths and footprints in the designated areas. These areas ranged in thickness from a minimum of 1½ to nine inches. The capping in some areas includes a layer of gravel on top of the sand. This gravel is 1¼ inch in diameter and acts as an armor layer protecting the sand from eroding.
The sand and gravel was purchased from two local producers – Michaels Material and Faulks Brothers. Brennan used 234,000 cubic yards of sand and 101,000 cubic yards of 1¼-inch gravel to cap a total of 110 acres of contaminated river bottom in the OU1 project.
GREG SMITH EXPLAINS
Greg Smith, J.F. Brennan project manager, described the capping process:
The delivery and placement of the sand cover can be broken into three major categories. They include the land plant and transport, spreader barge dewatering, and the spreader broadcast delivery.
The system begins with the land plant, which transfers the material from the shore to the spreader barge. A wheel loader and a metering hopper convey the cap material at a set rate into an adjacent slurry hopper. The material is metered by the feed opening and/or the variable speed of the belt. Lake water is injected into the hopper to create a slurry, which is moved by a slurry pump through an eight-inch SDR 17 HDPE pipeline to a booster pump and finally to the spreader. An overflow weir allows excess water to be discharged back into the lake during the slurrying process.
Once the slurry arrives at the working barge it is pumped into a material separator or a velocity box depending on if it is sand or gravel. The material separator provides the primary material / water separation, then discharges the material to the shaker screen with a weired retention tank underneath it to capture the fines lost from the dewatering screen.
These fines are pumped to a recovery separator on the end of the screen. The water that overflows the tank weir and the overflows from the separators is discharged into the spreader bay which is surrounded by a turbidity curtain. The dewatered material from the dewatering screen falls down a chute into a gravity feed hopper placed over a conveyor that delivers the material to dual broadcast spinners on the bow of the barge. These spinners broadcast the material in a uniform overlapping pattern. When the material hits the water, it falls at a reduced velocity to cover the soft sediment or preceding sand layer of the cap.
The material spreader consists of two barges. One is the working barge and the other is the guide barge. The two barges work in unison, walking back and forth parallel to each other. The spreader barge is 40 feet by 80 feet and the guide barge is 20 feet by 120 feet, both equipped with hydraulic powerpacks, winches and spuds. One barge is spudded down at all times. When the spreader barge steps back, the guide barge has both of its spuds down on the river floor. The spreader barge moves along the guide barge until reaching its stopping point. At this time, the spreader barge spuds down and the guide barge steps back. The material continues to be spread during these steps.
The spreader barge is outfitted with Real-Time Kinematic Global Positioning Systems (RTK-GPS). Similar to the dredges, the onboard computer use DredgePack™ and Wonderware for the operator interface software. DredgePack displays and tracks the barge’s position while Wonderware tracks and records the amount of material spread.
The system was custom-designed by Kruse Controls, who explains the operation below:
The sand spreader uses RTK GPS for position and elevation tracking. The RTK GPS system uses satellite links to two spreader-barge-mounted receivers, a fixed location receiver with known coordinates, and a geometric method known as trilateration to determine the real-time position and elevation of a point on the sand spreader to within one centimeter accuracy. This point is configured to be located at the sand discharge location. As the spreader barge travels, turns, and rises and falls on the lake, the system continuously updates the northing and easting coordinates, heading, and elevation of the sand discharge position.
The coordinates of the sand spreader are sent to DredgePack, Hypack’s survey software. DredgePack serves two purposes: it provides a continuous log of coordinates and elevations for the sand discharge location, and provides tools to help the operator locate the spreader barge at the required coordinates. The system accepts and displays existing survey information in both plan and elevation views.
A belt scale on the sand spreader discharge conveyor monitors the tons per hour (TPH) of sand discharged from the sand spreader. The belt scale controller integrates the TPH value and provides an electrical pulse for every 0.01 tons that passes by the scale. A programmable logic controller (PLC) on the sand spreader monitors the pulses and calculates the total tonnage spread. The PLC also monitors the spreader barge location coordinates (as determined by the RTK GPS) and the desired discharged sand setpoint (as entered by the operator). When the desired amount of sand for a specific location has been reached, the PLC sounds an alarm to signal the operator to move the spreader barge to a new location. Once the spreader barge has been relocated, the PLC starts tracking spread sand tonnage for the new location.
Wonderware’s Intouch software interfaces with the PLC to allow an operator to enter the spread sand setpoint along with other variables such as sand spreading volume and sand density. It also monitors the spreader barge coordinates and displays all operating conditions on a screen for the operator.
For each sand spreading location, the Intouch software system inserts sand spreading information into a Microsoft SQL Server database, including time and date, position coordinates, actual sand tonnage spread, sand density and spreading time duration for that spreading step. All of this information can be viewed via an Internet web browser in the form of a pre-developed report.
This system has been effective in tracking the amount of material spread over the lake. The project team’s hard work and quality control efforts have allowed the client – GW Partners – and the Wisconsin Department of Natural Resources (DNR) to reduce the amount of third party sampling performed. This is estimated to have saved the client more than $1 million dollars in sampling costs.
Two aggregate producers provided all the sand and gravel for the capping project.
Michels Materials, a division of Michels Corporation, provided 220,000 tons of sand and 60,000 tons of ¾-inch gravel to the project.
A family-owned construction conglomerate with 18 divisions in the U.S. and Canada, Michels Corporation’s Materials Division operates exclusively in the State of Wisconsin, mining from 100 quarries and sand and gravel pits.
For the OU1 project, Michels used material from its Meyers pit, 65 miles from the project. They provided all the material in a 10-month period, an extremely short time for this much material, said Moe Bohrer, sales manager. This project required natural gravel, which, along with sand, was in the Meyers pit, he said.
A Cat 988 front end loader digs material from the bank, and loads into an Allis Chalmers 3248 jaw crusher. From there, the gravel moves into a Cedarapids MBP 280 cone crusher and over a 6X20-foot screen deck, screening 450 tons per hour. Specifications required all material to be washed, and this was accomplished with a Kolberg-Portec wash plant with six by 20-foot screens, spray bars and washing screens. Dewatering was through two 44-inch-diameter, 32-foot-long dewatering screws.
Michels is number 53 in Engineering News Record’s list of top 400 contractors. Dale Michels founded the company 50 years ago, and after his untimely death in 1998, his wife and four sons took over operation of the company. Pat Michels, the oldest son, is president, and his brothers head the other divisions. Headquartered in the town of Brownsville, Wisconsin (population 267) an hour north of Milwaukee, the Michels headquarters spans 80 acres. The company runs 2000 vehicles and 5000 pieces of heavy equipment and employs about 4000 people during construction season. They have 18 mobile crushing spreads that move to where they are needed, processing 12 million tons of material a year.
Faulks Brothers Construction is owned by Robert and Randy Faulks, and headquartered in Waupaca, Wisconsin. They provided 97,000 tons of washed sand and 71,000 tons of 1¼-inch washed stone from July through October 2008 and in the Spring of 2009. Faulks mined the material from a sand and gravel pit that contains materials from basketball-sized cobbles to all sizes of sand. Volvo front end loaders move the material from the deposit in a 30-foot-high bank into a primary crusher – a Cedarapids 30/40 II jaw plant. From there it goes to a secondary crusher, a Cedarapids 6X20 triple deck wash plant with dual Eagle screw, and then to a wash tank. The material was transported by truck approximately one hour to the project site.
Faulks has one quarry and four sand and gravel pits, and has a total of 80 employees.
Gene Frederickson Trucking handled all the materials transport, and also the removal of PCBs from the processing site to the landfill, in trucks that carried 24 tons per load.
J.F. Brennan was the general contractor on the OU1 phase, and Boldt Co. and Natural Resources Technology (NRT) were the oversight teams.
The next phase of the project includes Operable Units 2 through 5 and is expected to take 10 years. TetraTech is general contractor and J.F. Brennan is a subcontractor for this phase, which began with mobilization and site construction at the end of 2008.