LOCATION: MANISTIQUE, MICHIGAN
DATES: APRIL 2019 – DECEMBER 2019
CONTRACT VALUE: $10,500,000
ROLE: PRIMARY CONTRACTOR
This project involved the dredging of approximately 42,000 cubic yards PCB impacted sediment. Approximately 1,100 cubic yards was TSCA level hazardous material. The materials were removed from various dredge management units within the outer harbor and river in the Manistique, AOC. The average cut thickness was approximately 18” over the entire project and less than 1% non-pay yardage was generated.
Following the completion of the dredging activities, White Lake Dock & Dredge was responsible for installing an activated carbon remedial cap over several of the DMUs and in areas of harbor previously dredged in 2016. In total, White Lake installed approximately 12,000 cubic yards of GAC-Sand blended material. The material was placed in 9” lifts with a 3” tolerance for over-placement.
The capping materials consisted of .5% by weight granular activated carbo mixed with 2NS sand. White Lake blended this material utilizing a precise system of belt feeders that fed a precise quantity of GAC for each pound of 2NS sand. The material was fed onto a central conveyor where it could blend and then was re-blended via mechanical means before loading into trucks. White Lake blended this material within a .02% tolerance.
TRANSPORTATION & DISPOSAL
All materials removed from the AOC were impacted with PCBs and disposed of at a Class II landfill or, in the case of the 1,100 cy of TSCA material, at a hazardous waste facility permitted to receive TSCA waste streams.
All materials were loaded into lined trucks for transportation to the disposal facility. Trucks were loaded in a lined truck loading area that allowed White Lake to capture any drips prior to the site leaving the lined area to avoid spreading of contamination.
In total, over 2,000 trucks loads of material were loaded and disposed of over a 3.5 month period of dredging operations.
To further solidify the sediments, a combination of sawdust and Portland cement was used to assure materials were dry enough for transport and to assure they met landfill disposal requirements. These materials were mechanically mixed with dewatering dredge spoils with a long reach excavator before being loaded out.
To handle the large quantity of PCB impacted sediments being removed from the AOC, White Lake built an integral lined dewatering pad that was sized for approximately 2,000 cubic yards of material. All materials were stockpiled in one of two cells for a minimum of 24 hours prior to be loaded out for final disposal.
All water drained from the sediments as well as all contact water that fell in the pits, on the transloading dock, within the truck loading area, or in the water treatment area was collected and ran through an on-site carbon pre-treatment system before being tested and discharged to the City of Manistique WWTP. Water was first collected in a weir tank too allow primary clarification, then pumped through a system of sand filters skids, before being pumped through a 400 GPM carbon pre-treatment system.