Archive for Thursday, April 24, 2008

Sewer breaks, washes waste into Hog Creek

Basehor Public Works crew tests the temporary pump attached to the city's primary sewer force main Monday afternoon. The line broke sometime Sunday night, bypassing sewage into nearby Hog Creek.

Basehor Public Works crew tests the temporary pump attached to the city's primary sewer force main Monday afternoon. The line broke sometime Sunday night, bypassing sewage into nearby Hog Creek.

April 24, 2008

Water quality along Hog Creek remains under the watchful eye of the Kansas Department of Health and Environment.

KDHE, along with the Kansas Department of Wildlife and Parks, issued a stream advisory for Hog Creek early Monday morning after it was discovered that the city of Basehor's primary sewer force main, which carries all of the city's sewage from the main lift station near 163rd Street and Parallel to the wastewater treatment plant, broke, sending sewage into the creek.

While water samples were taken yesterday to check pH, temperature, dissolved oxygen, ammonia and Escherichia coli bacteria levels, the collection of additional samples will be delayed because of Monday night's storms.

"We've had a bit of flushing from the rain," said Jeff Lamfers, an environmental scientist with KDHE, Tuesday morning. "Some might think that's the best time to take samples, but it's not, because after heavy rains sometimes counts go up even higher. We'll probably wait until tomorrow, but more likely Thursday. The last thing we want to do is lift it (the advisory) too soon."

The amount of sewage that leaked into Hog Creek is unknown, but Lamfers said he is fairly confident that only a small amount of the sewage passed into the creek, because of the appearance of the stream.

"If you start discharging hundreds of thousands of raw sewage, you're going to have dead fish," he said Tuesday. "There's going to be scum, there's going to be foam and we didn't see any of that yesterday."

Water samples taken Monday along Stranger Creek north of U.S. Highway 24-40 and Hog Creek revealed acceptable pH and dissolved oxygen levels. Higher levels of dissolved oxygen are desired and Lamfers said the lowest reading they collected was 8 parts per million.

"Less than 5 usually starts stressing fish, and we were up around 8 or 9," he said. "Eight is pretty decent quality of water so we were happy about that," he said.

Ammonia results may take up to a week, Lamfers said, but the E. coli levels are more important and results were in by Wednesday morning.

Streams are classified as primary contact, such as those used for swimming, diving and boating and secondary contact, such as fishing or hiking, Lamfers said. Since Hog Creek has limited public access, it is considered secondary contact. KDHE uses a guideline, which states that a health advisory should be issued in secondary contact streams if there is a concentration of more than 10,000 E. coli colonies, Lamfers said.

Water samples taken right where the bypass entered the stream yielded 8,664 E. coli colonies, while samples collected at 167th Street and Hog Creek, about a fourth of a mile downstream from the bypass, showed 129,060 E. coli colonies.

While streams will always contain E. coli, elevated levels suggest the presence of more harmful bacteria that can make humans and animals sick.

"If it's (E. coli) present, then you usually have pathogenic bacteria present and those are the ones that carry disease," he said.

Lamfers said samples are always taken upstream and from other side tributaries to allow scientists to compare the data collected to normal E. coli concentrations in the stream. Samples collected upstream from the lift station showed 95 colonies and those collected from a tributary near Parallel that would not have been affected by the bypass had 691 colonies.

"This justifies having placed the stream advisory in the first place and keeping it in place," Lamfers said. "We obviously had a pocket of contamination at 167th and Hog Creek, but for reference numbers, it's not unusual, especially in raw sewage, to get E. coli colonies in the millions. And, it's not unusual downstream of a discharge to find numbers in the hundreds of thousands."

Since test results showed elevated levels of E. coli, sample collections will continue once the creek flow has returned to normal, Lamfers said. The advisory will also remain in effect until desirable test results are obtained, which means people, pets and livestock should avoid contact with the water as a precaution until further notice, he said.

"We want to err on the side of caution and wait a few days for the stream to return to normal," Lamfers said. "Sometimes we have to sample several times before levels come down."

The sewage leak was under control by 7 a.m. Monday and the city of Basehor's Public Works crew has temporarily repaired the 12-inch force main break.

City Superintendent Gene Myracle said they went out to the site of the city's main lift station, 20005 163rd St., early Monday morning after noticing a lack of sewage flow in the ultraviolet disinfection system at the wastewater treatment plant just west of the city.

"We immediately came here and noticed that we had sewage coming up from the concrete structure," Myracle said Monday afternoon.

Power to the entire site, including from the backup generator, was cut, stopping the leak and allowing workers to begin excavating. Myracle suspected the main broke sometime Sunday evening.

The site consists of the lift station, which houses two underground pumps, a generator, a transfer station and odor control, all resting on a large 12-inch thick concrete slab. Excavating began just south of the slab - the suspected place of the main break. However, Myracle said they later found the crack in the pipe actually extended underneath the concrete slab.

Thompson Pump brought in a temporary pump and attached a temporary discharge line to the broken main to allow the station to continue functioning while repairs are made.

The lift station generator, odor control and transfer station were moved off the concrete slab Tuesday afternoon to allow workers to cut the concrete into pieces for removal. About three quarters of the slab was removed to allow access to the cracked main, Myracle said. The city will not replace the concrete because the lift station is scheduled to receive a major revamp in about three months, when construction is set to begin on the planned wastewater-treatment plant expansion. Myracle said repairs to the pipe should take about three days and he hopes to have the temporary pump off the site by the end of the week.

"Hopefully by Friday," Myracle said, about doing away with the temporary pump. "But, it's going to be tough. We have to have everything wired back in."

City Administrator Carl Slaugh, said this is the seventh break the force main has sustained since it was installed in 1999, but the current break is the worst, because the damage occurred underneath the concrete. The breaks always take place at the bell coupling, where the sections of pipe are joined together, and Slaugh said these breaks are most likely due to the sudden surge in pressure the main endures when the pumps begin a cycle. As a part of the treatment plant expansion, the lift station will receive a variable-frequency drive, which will slow the pumps and lessen that sudden snap in pressure, Slaugh said.

This break also occurred at the bell coupling, but then the pipe itself broke and the crack extended all the way up underneath the concrete slab. Slaugh said the original design plans for the lift station called for 42 linear feet of ductile iron pipe, and polyvinyl chloride plastic (PVC) was used instead.

"Generally, if it's under a road or some structure where you don't want to have to go back in to repair it, you specify a higher grade of pipe," Slaugh said. "Instead of PVC for 42 feet, it was specified as ductile iron. We don't know why it wasn't built as designed. I will be checking through the city attorney to see if there's any negligence involved through the engineering firm that inspected it or the contractor that put it in."

While Basehor Public Works considered the incident a worst-case scenario, the break will not cause sewer problems for residents.

"This will not affect any residents whatsoever," Myracle said.


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