||Tuesday, September 16, 2014
‘Dam stopped repeat of 1993’
by Gregory R. Norfleet · News · April 26, 2013
West Branch saw between 5 and 6 inches of rain in less than 24 hours April 17-18, and many city leaders credit the new “Hoover Dam” for preventing a repeat of 1993 flood levels in West Branch’s downtown.
Still, the rainfall led the City of West Branch and Hoover National Historic Site to close three streets, shut down historic buildings, place sump pumps in low-lying areas and bypass the sanitary sewer when it flooded with rainwater. City Public Works Director Matt Goodale worked all night to monitor pumps and flooded areas.
Wapsinonoc Creek — called Hoover Creek inside the historic park — and its branches rose to the bottoms of bridges, the road in front of West Branch Fire/Police Department was flooded, a retention wall collapsed behind Hilltop Condominiums and residents along Pedersen Street called the city for help when their basements began to flood.
Downtown businesses reported water getting basements, as did residents from all areas of the city. At least one youth sports event was relocated due to soggy conditions and the Earth Day tree-planing event was pushed back a week.
In December, a grade stabilization structure was built on farm acreage shared by Curt Friis and John Black. The structure is essentially a dam which captures water running down hill and slowly releases it. The dam is north and west of the city and sits in 311 acres of farmland that guides rainwater into the city.
“The stormwater retention basin made a difference,” Public Works employee Tim Moss said. “Otherwise, we would have been at 1993 flood levels. We might have had 6 more feet downtown.”
Mayor Mark Worrell visited the basin — which some have dubbed “Hoover Dam” — a few times to monitor its effectiveness. The dam can hold up to 14.5 million gallons — the equivalent of 1,800 truck tankers — and he said that last week’s rains filled to within 8 feet of the top.
“That’s pretty accurate,” Worrell said of Moss’ assessment. “It was a pretty good-sized lake, and the creek behind it (where it releases the water) was only half full.”
Moss said the rain gauge at his home measured 2 inches at noon on April 17, 3 inches by the time he got home at the end of the day, and 5 inches by the time the rain stopped the morning of April 18. He said his father, Howard, saw 6 total inches in his rain gauge.
Hoover Park Superintendent Pete Swisher said the flooding throughout the Hoover Complex “would have been worse” without the Friis-Black retention basin, and he wants to thank the landowners and agencies that helped get it built.
Friis said he checked on the dam and said “I think it did the job.”
“Without it, the creek (would have backed up) more in the park,” he said.
When he and Black agreed to make room for the structure, they “never dreamed” it would get tested so soon.
“This was a good test of it,” he said.
City Administrator Matt Muckler said the city closed First Street from Parkside to Green Street and the College Street bridge. The city and National Park Service agreed to close Second Street from Main Street to the bridge between the car wash and Families Inc.
Muckler said Patton Family Health, which sits along a closed section of First Street, cancelled appointments not because the water reached the building, but because patients could not.
Town Hall, at the corner of Main and Parkside, also had significant amounts of water in its basement. Worrell said the section of creek on West Main Street, near West Branch Ford, rose to within a foot-and-a-half of the trail that takes children to the high school.
The city had installed a larger pipe on the south end of Pedersen Valley in what was called the “bottleneck project” and that revealed “a new low point in the system,” Muckler said: the intersection of Green and First streets.
The city has also been trying to identify cracked sanitary sewer pipes that are letting rain — rain that should flow into the stormwater sewer — seep in. Muckler said the storm showed them that there is still a lot of work to do.
“This storm overwhelmed any progress we made,” he said. “It was a wake-up call.”
Ironically, he said, water also backed up where the city is building a new lift station, which is supposed to pump water to a higher elevation so gravity can drain it away.
Leaky sanitary sewer pipes, or “Influx and Infiltration,” are waiting for Phase II and III of the city’s sewer repair and replacement project. Muckler said those phases will go out for proposals soon and should get done this spring and summer.
“We can’t get lax,” he said. “We have to stay on it.”
Muckler said a family in the 200 block of Pedersen Street called in about basements flooding, and the city posted a sump pump to unload extra water from a manhole near their home, in hopes of helping everyone in that area. However, the water did get in and families were hauling personal items out of their basements.
Worrell said Fox Run Golf & Country Club had a river running through it that reached nearly 200 feet wide.
The afternoon of April 17, the NPS issued a press release that it was closing the historic buildings “as a precaution against flooding.”
Swisher said the buildings themselves were not in that much danger, though the Meetinghouse did get water in its basement, but that staff was needed in other parts of the park to fight back the water.
“We needed to move people into preservation mode,” he said.
The superintendent said visitors largely stayed away due to the storm, and he does not think they had to cancel with any school groups, so moving staff around did not cause any inconveniences.”
Hoover Creek experienced culvert damage and a couple of sump pumps quit working, and the soaked ground weakened the already damaged shoulders around Parkside Drive. He said Parkside’s shoulders were slated for repair, but last week’s rain may mean the project needs to take place sooner.
The NPS has a maintenance shed near the bottom of the hill on Second Street which is known to flood first in heavy rain, so staff were sent to pile up sandbags, but Swisher said that, surprisingly, they did not see any problems there.
The U.S. Geological Survey on April 17 was scheduled to study Hoover Creek, and they came on a peak day. Swisher said Hoover Creek normally flows about 6 cubic feet per second. With USGS workers standing on a foot bridge over the small branch, they recorded flow rates up to 322 cubic feet per second. A day later, the water slowed to about 100 cubic feet per second.
“We had two surges over 300 cubic feet per second,” Swisher said.
Water in the creek is usually less than two feet deep, but the heavy rains caused it to swell to more than 8 1/2 feet deep.
The Hoover Creek stream gauge data is on the Web at waterdata.usgs.gov/ia/nwis/uv?05464942.
At Hilltop Condominiums, the retaining wall that collapsed backs up to Hilltop Drive. Dozens of decorative cinder blocks that make up the wall fell into the back yard of the building, and large sections of the wall are protruding outward or leaning forward, with many more of the blocks coming loose.
Muckler said the condominium owners are arranging for contractors to replace the wall. The city, meanwhile, has blocked off that section of the road and sidewalk. There is large crack in the earth a few feet behind the wall where the ground has started to break away from the hill.
“We are concerned about further collapse of the wall,” the city administrator said. “We’re being cautious. We don’t know what is under there.”
West Branch Schools
While the April 17-18 storm was heavy and long-lasting, the storm that hit the Hoover Hometown Days last August was more powerful yet short-lived. That storm brought heavy winds that blew rain under doorways at the schools that do not typically have problems.
West Branch High School Principal Michelle Lukavsky said the Spanish classroom saw some minor leakage that was easy to clean up.
“It wasn’t bad at all compared to Hoover Days,” she said.
School Operations Director Joe Lande said some water leaked into the boiler room at Hoover Elementary and there were “a few roof leaks” throughout the three school buildings.
“But there was no flooding,” he said.
There was some wash-out behind the elementary school and a bit of runoff, “but nothing really damaging.”
Hoover Elementary Principal Jess Burger said the school has some minor leaking around windows and a bit of damp carpet, but no real damage. West Branch Middle School Principal Sara Oswald said their boiler room saw some water get in, but there was no damage.
New reference point
Swisher said that in his more than two years in West Branch, the weather has “essentially been a drought.”
“That’s been my frame of reference,” he said, though he has heard about the flooding of 1993 and 2008.
Muckler, who has been in the city since since summer 2010, said something similar. He remembers the heavy rains that first year, like at Hoover’s Hometown Days.
“This is my new point of reference,” he said.
Moss said fixing leaking sanitary sewer pipes is a “neverending process,” and while Muckler said the city hopes to find, by running cameras through the pipes, a “home run” repair, so far none have been found.
“We’re inundated in lots of different areas,” the city administrator said.
Muckler said the “silver lining” is that the city is making progress in its fight against flooding.
“We’re looking forward to brighter things,” he said, talking about the sewer repairs and lift station. “Thank goodness we had the Hoover Dam project. Those things really help.”
Worrell said the city has done a lot to repair and replace leaky sewer pipes, and it has made a difference.
“We didn’t pump nearly as much as we did in 1993,” when the Wapsinonoc backed up, he said. “But the water table was so full that anything that could leak did.”
The mayor said the rainfall was “all the proof we need” to press on with sewer repairs, which could exceed $300,000 this year.
“This was the perfect test,” he said.
On Thursday, after the rain stopped, the city kept a sump pump — and added a second — to the manholes at Main and Parkside, pumping water from the sanitary sewer to the storm sewer. The idea was to get ahead of another rainfall predicted for later in the week, but nothing significant actually came.