UCC’s underwater inspection teams complete many FERC Part 12 inspections for the Hydroelectric industry throughout the U.S., working directly for the utility owner/operator or the independent consultant. Many times these inspections identify repairs or maintenance that UCC performs at a later date.
Following a summer 2020 inspection at a dam’s powerhouse in Michigan’s Upper Peninsula, it was determined that the removal of an excessive debris accumulation reported upstream of the units was required. UCC’s Wisconsin office began project planning, debris processing development and budget submittals in preparation for the upcoming 2021 season.
Removing the debris presented a challenge due to the site’s configuration. Debris identified for removal was located within the powerhouse, upstream of the units between the trash racks and head gates. Rather than assembling an upstream floating platform and removing the trash racks, UCC worked with the dam owner and found the most economical way to remove and process the debris was to complete diver-assisted dredging and move the material directly through the powerhouse.
Nearly 70 cubic yards of debris slurry was pumped through an assembled pipeline and discharged up to 200 yards away to a debris collection and dewatering location. Twenty cubic yard dewatering boxes collected the debris and separated the clean water. Debris was tested and hauled to an approved landfill in accordance with permit requirements. Much of the debris found was required to be removed by hand and transported via debris hoppers to the disposal area. Discharge water was also tested prior to dewatering.
Excellent communication and involvement with the site owner, perfect onsite safety, finishing ahead of schedule and meeting budgets resulted in another successful diver-assisted dredging project.