By Rebecca Dopp
Times-News Correspondent
What was originally thought to be the cause of the Mona City sewer plant’s pumps going out more frequently—material and other objects being flushed down the toilet—has turned out to not necessarily be the case. While these items can, and still do, cause problems with the pumps, workers at the Mona City Sewer Plant have identified what they think is the major cause. “Sewage lift pumps are not designed to pump aggregates—rocks, asphalt, etc.,” said Jeff Elbert, sewer plant worker. “They’re not robust enough. The old pumps that we had in there—the volute, or the pump case—got holes in them, about a 2-inch diameter hole from a rock.” He said that they had lost two volutes that way and the impellers got worn out with pumping a slurry. So what was in the lines were peat gravel, rocks and asphalt. The pumps have a 3-inch inlet and a 4-inch discharge that goes up into an 8-inch line that goes up into a 10-inch line, he explained. It goes up about 15 feet and then turns 90 degrees and heads towards the plant in a 10-inch line after the valves. The velocity that has to go in that water has to be about 6 feet per second in flow in order to carry the solids towards the plant. “The problem is that when you get those heavy rocks, asphalt and debris that’s not sewage anymore—it’s just things that are too heavy for it to carry up there—you need to increase the velocity but the pumps can’t do that,” he said. Elbert thought that there was sediment in the line, but when they went to look with a camera recently, they couldn’t because they couldn’t drain the pipe. The camera could not see through the sewage water. He said that they would need to find a way to drain the water, but there is no clean-out in the line from the lift station to the plant. Typically, he said, they would hold the check valve open, turn the pump on and then hold the check valve open, and then turn the pump off. All that water would then come back into the wet well. He said he was reluctant to do that because the system is like a funnel. The big rocks would wedge into the smaller line and plug it off. The pump would no longer work. They would need to remove an entire 15 feet section of pipe in order to clean it. They do not have the equipment to do that nor the manpower. “Right now we can’t get the line clean,” he said. “We need to get a jet truck in there to clean it.” He said they were running into problems because the angles of the pipes would not allow a jet truck to get the job done. Katrina Long, council member, asked how the rocks and asphalt got into the line in the first place. Elbert said that anytime someone bore a hole to hook into the sewer line, rocks and gravel could fall in the line. The manhole covers that have holes in the top could also be a way the rocks are getting into the system. Mike Stringer, council member, wondered if there were some illegal connections to the sewer line with drains in people’s garages. He did not know how they would police that. Jay Mecham, council member, said that they would need to figure out a way to clean the line. They would need to dig out a spot, put in a “T” so they could get the jet truck to clean the line out. Then they could get a camera in periodically to check the line. The impellers cost approximately $5,000 to replace. Putting in a screen to catch the bigger material before it gets to the pumps would not be feasible, Elbert said. It would be too deep and not easily accessible. He felt that when they got the lines cleaned out, it would not be as big a problem like it is now. Mayor Bill Mills asked if they would start from the plant and work their way back to clean out the line. Elbert said that would be a good place to start. After the line was clean, the city could go back in three months to check and if it looked okay, come back in six months and then possibly once a year to check the line. Michelle Dalton, city secretary/treasurer, said she had posted in the city newsletter the “Do Not Flush” list of items and wondered if she should take it out now that it seemed like rocks were deemed the bigger problem. Mills said that they should keep that information in the newsletter. Elbert said that they continued to get items in the impellers, including little girl’s underwear. Items you should never flush down the toilet or drain include flushable wipes, paper towels, baby wipes, cat litter, fats, oils, grease, cigarette butts, dental floss, band aids, feminine hygiene products, prescriptions, hair, cotton balls and/or swabs, any plastic, latex or rubber products. “Your toilet is not a trash can!,” the newsletter stated. Brent Arns, sewer plant supervisor, showed some pictures of some of the items that got caught in the impellers. He said he had a box full of items they had pulled out of the pumps including a golf ball, pieces of a tarp, rags, etc. He said there were 14 pumps at the plant that ran all the time, 3 lift pumps, 2 permeate pumps that run 24/7. “If we lost any of those pumps,” he said, “we’d have to stop flushing.”
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