Kokosing Working Indiana Harbor Superfund Job
Workers assemble a recirculation pump on the CDF levee for the Indiana Harbor Shipping Canal maintenance dredging project.
In 2012, Kokosing Construction Co./O’Brien and Gere, Inc. joint venture started a long awaited Corps of Engineers maintenance dredging project, within the Indiana Harbor Shipping Canal. Over the past 112 years, the canal has been home to heavy industry, which has led to historic contamination of the surrounding waters and sediments.
Located in the southwest corner of Lake Michigan, the Indiana Harbor Shipping Canal (IHSC) services some of the largest steel and oil refining companies in the nation. As much as 15 million tons of cargo can be delivered to the port in a given year, making the harbor the 46th busiest in the U.S., as of 2011. The channel was constructed in 1901 and is federally maintained under the Rivers and Harbors Act of 1913.
The Komatsu PC1250 excavator equipped with a seven-cubic-yard Anvil environmental clamshell loads debris into a front end loader for transfer to the CDF.
The canal is two miles long, with navigational depths ranging from 22 feet at the inland end to 29 feet at the turning basin at the canal entrance from Lake Michigan. Transit is complicated by the presence of six low bridges, all of which must be opened to allow the barge to pass. The process can take from two to three hours.
The CDF is at the farthest inland point of the canal, on the site of a former Sinclair refinery. Dredging started next to the CDF, the location of extreme oil contamination. The dredge consists of a barge-mounted Liebherr 895 crane using a 15-cubic-yard Cable Arm environmental Workers assemble a recirculation pump on the CDF levee for the Indiana Harbor Shipping Canal maintenance dredging project. Workers adjusting the 15-cubic-yard CableArm environmental clamshell bucket on the dredge. The over-square 14 foot long by 15-foot wide footprint allows the bucket to dredge a generous level cut of material without windrowing, and it rises through the water bucket, which has a large footprint and reduces suspended solids. The dredge digs within a moon pool outfitted with oil absorbent to capture any oil sheens generated from dredging, with two turbidity buoys flanking the operations for environmental monitoring.
Workers adjusting the 15-cubic-yard CableArm environmental clamshell bucket on the dredge. The over-square 14 foot long by 15-foot wide footprint allows the bucket to dredge a generous level cut of material with reduced windrowing, and it rises through the water column creating little suspended sediment.
Dredged sediment varies from clay to oily sediments, but most is a sloppy muck, laced with tons of debris that was not expected prior to the start of the project.
Once a barge is filled, it is moved by tug to the CDF and moored next to an excavator barge equipped with a Komatsu PC1250 excavator, using a seven-cubic-yard Anvil environmental clamshell. This excavator unloads the dredged material into a third barge topped by a steel woven mesh, which catches the debris, allowing the sediment to drop into the wet well beneath.
Choosing the correct mesh opening was a difficult challenge because of the need for the sediment to flow through the mesh while leaving the debris behind. The first screen size used was too large, and allowed rope, plastic, clay, wire and lumber to pass through, jamming the submersible pumps that emptied the material into the CDF. After trial and error, the correct mesh size was discovered, and a manifold system that sprayed water across the mesh washed most of the sediment into the wet well. Periodically, the screen needs to be repaired or replaced because of wear generated from digging off of the screen using the excavator and from heavy debris being dropped onto the screen.
Two submersible pumps in the well pump move the material into the CDF, moving it as far as 3,000 feet with the help of boosters.
Periodically, the excavator loads the debris into an adjacent hopper barge, which when full is moved to a nearby crane pad and unloaded into seven-cubic-yard front end loaders, which dump the debris into the CDF.
During the 2012/2013 seasons, more than 4,000 tons of debris was found in 400,000 cubic yards of dredged sediment.
All personnel in the transit and unloading stages must wear Tyvek suits, and the process involves extensive cleanup of the equipment following unloading.
The dredge digs in a moon pool outfitted with oil absorbent to capture any oil sheens generated from dredging, with two turbidity buoys flanking the operations for environmental monitoring.
To store contaminated material at a CDF, the structure must have a low permeability to prevent groundwater contamination and a means for covering the dredged sediment so it cannot become airborne in dry, windy conditions. Starting at the pumping operations, a slurry of water and sediment is pumped over the CDF dike walls into one of two cells inside of the CDF. The two cells are created by a lower center dike, splitting the 90-acre facility into roughly two 45-acre cells. The slurry is pumped into either the east or west cell and discharged from one of 10 discharge pipes. The HDPE piping used for the system provides flexibility for barge movement, adequate pressure allowance and easy repairs and modifications if necessary. For sections of pipe outside of the CDF walls, dualcontained HDPE pipe prevents leakage onto the site, if one occurred within the inner pipeline.
In order to slurry the sediment for pumping, water must be added from a source. To maintain consistent water levels within the CDF without adding water from the canal, the water creating a two-foot water cap for emission prevention is used to feed the hopper barge pump bay. Two 12-inch DPC300 Godwin electric pumps pull water from the CDF into the hopper barge, where two submersible pumps create the slurry. The barge pumping operation employs two discharge trains consisting of two DP 150B Toyo electric submersible pumps to gather the slurry and two 500hp electric booster pumps to adjust the flowrate for more distant discharge locations.
Aerial view of the Indiana Harbor Canal shows the entrance at Lake Michigan and one of the six bridges that must be raised for the barge to transit the two miles to the CDF.
One of the biggest decisions during the fabrication of the debris separation barge was whether to install diesel fueled pumps or electric powered pumps. By going electric, the pumps run cheaper and quieter. Also, PLC software operates and data mines the flow operations with a SCADA system, so the electric pumps can be regulated. By employing variable frequency drives in the system, the pumps will regulate themselves to a desired velocity or flow rate designated by the pump operator through the PLC programming. Using this information, operators can compare daily production with the dredging totals estimated from hopper barge counts.
This system also evenly distributes material within the CDF by using in-line flowmeters and density gauges. Using the information compiled in the SCADA system from these gauges, the dredging team knows the exact amount of sediment placed at each discharge location. In order for the CDF to seal, the dredged material must be deposited evenly across each 45-acre cell. This is accomplished by changing discharge locations every few thousand cubic yards.
After depositing the first 400,000 cubic yards through August 2013, all indications show that the CDF is maintaining its water levels without excessive loss. The facility is surrounded by a network of 88 groundwater monitoring wells and pumps, which determine the elevation of groundwater around the site and feed any excess groundwater back into the CDF. The goal is to maintain a negative inward gradient, meaning that water is flowing to the site, not away from it.
The CDF site also has multiple air monitoring stations to determine if the stored sediment is generating any harmful emissions or particulate matter. The best way to manage the potential contaminates in the CDF is to maintain a two-foot water cover over the discharged sediments and to reduce discharge agitation and aeration during sediment placement. Readings through December 2013 show negligible emissions through all stages of the project.
Air quality is measured with handheld photo ionization detectors (PIDs).
Monitoring local worker air quality is also a major priority. The extended exposure to the pumping operations makes workers more susceptible to coming in contact with contaminated emissions. In order to protect the safety of the workers, handheld Photo Ionization Detectors (PIDs) monitor the local emissions.
Through 2013, PID monitoring has detected only a handful of times where respirators became necessary, while offloading dredged material. PIDs are also employed on the dredge rig where readings have been consistently low due to limited aeration and agitation caused by clamshell digging operations.
Finally, the instream water quality of the canal is monitored to determine if reintroducing the sediment into the water raises environmental concerns. Fondriest Environmental, designed a system to monitor the real-time turbidity produced by dredging with two environmental monitoring buoys equipped with monitoring sondes.
Any turbidity greater than 50 NTU over background turbidity over a 30-minute period will cause a shutdown of dredging operations for a minimum of 15 minutes or until turbidity levels drop below the threshold. Normal turbidity in the canal ranges from eight to 15 NTU. USACE is using the data collected from real-time and yearly physical sampling to determine if there is a correlation between turbidity and the total suspended solids present during dredging operations.
The dredge working in front of ArcelorMittal Steel, digging in an absorbent-surrounded moonpool and loading into the green-sided barge.
Because this is a maintenance dredging project, dredging can occur only to the authorized depth of 22 feet, though in places contamination is as deep as 40 feet. In future years, there will be the potential to remove Toxic Substance Control Act (TSCA) materials from the canal. TSCA sediments are defined by the presence of high concentrations of more dangerous substances, including PCBs and heavy metals. Several smaller hot spot locations have been found from environmental sampling. After being dredged, these locations will require additional preventive maintenance to prevent the release of contaminants.
The Indiana Harbor Shipping Canal maintenance dredging project will be entering its second option year in March 2014, with a possibility of having funding to dredge as much as 400,000 cubic yards.Edit Module