Posted on July 24, 2023
Inner City Diesel LTD successfully dredged 30,000 cubic meters of materials in extreme cold conditions, pushing people and equipment to higher levels of performance.
Their customer was under a short timeline and government restriction to clean up two closed coal mine lagoons. Working against freezing temperatures and a short clock created a project with no margin for error. Their decisions regarding manpower, machine performance and team coordination thrust them to success. Inner City Diesel LTD prevailed and conquered the challenges of dredging in icing conditions.
They chose the Crisafulli Rotomite 6000 dredge for the job. The nimble Rotomite 6000 performed well because of its superior maneuverability with no draglines or cables. It sped up the process of dredging in icing conditions.
“The Rotomite 6000 totally rocked it”, says Sean Mortimer of Inner City Diesel LTD. Cable dependent dredges cannot operate in these icing conditions. The cables freeze up and need time to thaw resulting in delays, and causing more challenges as the water thaws, runs and refreezes. Ice accumulation strains the cable system and results in loss of function, while anchor points severely limit the ability to break through ice. All those factors considered, the untethered Rotomite 6000 was the best choice.
The crew was tasked with clearing two ponds located at the coal mines. For pond one, (the bigger pond) they used dewatering bags. The crew laid out the dewatering bags near the shore of the pond. They mixed the mud with a flocculent to speed up the process of separating sediment and water. The flocculent was added to the slurry in pre-determined doses, via a flocculent dosing system. This causes the separation of the water and mud. The heavier particles settle to the bottom and the water bleeds out of the bag. Over time, the mixture completely separates and dries and the remaining sediment than can be used as fill for reclamation applications. After clearing the first pond, the crew moved all equipment to the second pond. Initially, they had a smaller remote-controlled dredge in place at this pond, but it was no match for the harsh weather conditions and was removed. The crew then placed the Rotomite 6000 into the second pond. At the end of October and early November, the weather conditions worsened with increasing winds and falling temperatures. The crews had to cut their way through 8 to 10 inches of ice. They used the weight of the cutterhead on the Rotomite 6000 dredge to break off large pans of ice. Then they removed the pans of ice from the pond using the long stick hoe. Removing the ice pans prior to submerging the cutterhead was necessary to freely move and operate the dredge.
When the temperatures dropped to below zero Fahrenheit (-18° Celsius) and lower, the slurry started to freeze and negatively affected the flow. Crews flushed the pipes regularly and used heaters when ice began building up at the metal collars. Ice also built up on the dredge itself, reducing buoyancy. To stay safe, the crew compensated for the additional weight by minimizing the fuel load and filling the tank to half-full levels. The Inner City Diesel team maximized machine operating time by
anticipating the need for replacement parts and ordering replacement parts in advance of failures. They knew the icing conditions would consume more wear parts. Their forethought enabled them to replace seals/parts in a timely manner and continue operations.
Inner City Diesel LTD asked for help from the people at SRS Crisafulli, Inc. who manufacture the Rotomite 6000. They supported Inner City Diesel LTD’s endeavors, provided expertise and warrantied five shipments of parts. Reinforcements from SRS Crisafulli, Inc. included late night calls to troubleshoot and solve problems. As Sean Mortimer says, “Chad (Schipman) helped the process and answered questions. Tony (Monson) was invaluable on providing maintenance expertise and Dave (Schipman) trained the crew on operating the dredge”.
The crews continued dredging and breaking ice until the project was complete. The crews performed difficult tasks in cold temperatures and windy conditions. They worked for 2 months on 12 hours/per day shifts. During the final 10 days, they worked around the clock on 24 hours/per day shifts until the job was complete.
Many minds, skilled labor and the right equipment combined to successfully complete this dredging project despite freezing temperatures and a short clock.
Figure 1 Rotomite 6000 & Dewatering bags on shore
Figure 3 Ice pans removed from the pond
Figure 4 Making a channel
