Protecting Portland from floods New trash rakes meet deadline – despite the pandemic
Automated trash rakes with frequent equipment failures to be replaced by a much more efficient new system – all very carefully scheduled for a fast-track completion ahead of the November to June flood season – and then along comes a pandemic. For the Multnomah County Drainage District No.1 (MCDD) in Port - land, Oregon, who help protect lives and property from flooding, robust pumps and trash rakes are essential, so from what was already a major, time-sensitive equipment upgrade, the all-important deadline suddenly became a challenging journey into the unknown. MCDD, in conjunction with three other districts, operates and main - tains flood management systems for nearly 13,000 acres of land along the Columbia Slough and the lower Columbia River. These systems include: 27 miles of levee, 12 pump stations, and 45 miles of sloughs, streams, and culverts – maintaining the river corridor levee system and vitally removing stormwater, which protects tens of thousands of jobs and residences, hundreds of acres of parks and natural areas, places of cultural and historical significance, and public infrastructure such as Portland International Airport. One cannot underestimate MCDD’s level of responsibility to keep all the water moving and under control. Since its inception in 1917, there have been five major high-water events, with the most devastating being the flood in 1948 that killed 15 people and destroyed the city of Vanport. In recent years, during heavy rainstorms and debris accumulation, frequent equipment failures were causing the existing, automated trash rakes at MCDD’s Pump Station #1 to shut down. Brian Eberhardt, MCDD’s Project Manager said: “With the old rakes at the end of their service life, we had the opportunity to invest in better, looking at how we could improve the performance of the pump station – and have a system that would also allow the debris gates to handle larger items such as trees. We also wanted to have trash rakes designed with quicker self-cleaning that would in turn be easier to maintain.” Randy Lyons, MCDD’s Operations Manager, added: “We were having to undertake far too much supplemental removal of debris, which for 6 to 8 days of the year meant us having to have a two-man team go out on a barge to collect larger debris with an excavator, which apart from taking up valuable time, also raised health and safety concerns.” Replacing in kind wasn’t an option when Brian Eberhardt and his MCDD team began looking for a new system with mechanical design
firm, Murraysmith, and their Senior Engineer, Austin Rambin. A much bigger mechanism with a larger rake head was required to increase ef - ficiency over the previous units, which had a three-and-a-half-foot rake head. Also, a trash rake that could lift 2,000 lbs or more was needed, versus an existing lifting capacity of 1,250 lbs. “We spoke to operators in our region and went to see them”, said Austin Rambin from Murraysmith. “These included one at a hydroelectric dam and another at a power generating site. The fact that the Lakeside Muhr trash rake was scalable for our required widths was a big advantage, rather than some manufacturers, who could only provide fixed sizes.” ‘Cleaning time reduced to less than five minutes’ He continued; “MCDD has a very good, experienced team, who cer - tainly know how to maintain and troubleshoot, but when we were con - sidering the design of the system around the rakes, we knew we wanted to improve on the cycle time for cleaning, which for two traversing rakes on a chain system, was taking half an hour. With five Lakeside Muhr stationary Model T-260 Hydronic T Trash Raking Mechanisms, this cleaning time would be reduced to less than five minutes.” MCDD’s Asset Maintenance Specialist, Josh McNamee, added: “The Lakeside rakes allowed us to achieve our aims by providing the in - creased redundancy we’d gain from having one rake per bay; also, with fewer moving parts to maintain and less movement. Less wear and tear
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csengineermag.com
June 2022
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