Dam should hold back 14.5 million gallons
by Gregory R. Norfleet · News · January 02, 2013
In 2008, a very heavy rainfall brought flooding to West Branch not seen since the 1993 flood.
Water overran the banks of the Hoover Creek and stretched to within 15 feet of the Hoover Library-Museum’s northwest corner, among other things.
The Library-Museum moved historic documents another 18 inches off the floor, knowing it was only treating the symptom, not the problem.
But for the past 2 1/2 years, the Cedar Soil and Water Conservation District focused efforts on the Hoover Creek Watershed, which extends miles north and west of West Branch. The city is at the bottom of that array of hills, thus the flooding. The way the contours of the Hoover Creek watershed lay, water flowing from downhill would first reach the Greenview subdivision and houses along Orange Street.
During that time, Hoover Creek Watershed Coordinator Judy Hagan worked with numerous land owners, mostly private, using I-Jobs funding to help build 18 rain gardens, basins, terraces, waterways, soil quality restoration projects, native plantings, terraces and grade stabilization structures. All of them slow down the rate of water running downhill, toward the city.
On Dec. 19, Hagan and others invited the community to see the largest of all those projects — a grade stabilization structure — essentially, a dam — that collects rain from 311 acres of the Curtis Friis farm south of Oasis, just a mile or so west of the Cedar-Johnson county line.
So how much water can it handle? Kent Rice, engineer with French-Reneker of Fairfield, who designed the structure, said it can hold 14.5 million gallons. That much water is equivalent to:
• 1,800 semi-tanker truck loads of water
• 60,000 tons of water
• Six trains of 100 tanker cars or
• A 40-acre field covered with water more than a foot deep
Both the City of West Branch and the Hoover Complex will benefit from the $120,000 project, so they both have pitched in about $11,400 each — just under $22,800 so far — and have committed to a total of $26,200.
“The whole National Historic Site is at risk of flooding,” Hoover Library-Museum Assoc. Promotions and Academic Programs Manager Delene McConnaha said. The Hoover Assoc. donated the funding on behalf of the Complex.
Hagan has been working in water management for 32 years, and this is the largest project she has ever built. However, while she said the Friis project should make a difference, she considers it only “a start.”
“There are still measures that need to be done,” she said.
City Administrator Matt Muckler agrees.
“The amazing thing is if we just do five or six more of these we wouldn’t get slammed in West Branch,” he said while viewing the trenches and pipework laid out across several acres of the Friis farm, just east of Oasis Road.
The Friis dam is also the last of the 18 projects, Hagan said, because all of the I-Jobs money is gone. It was all supposed to be used by July 1, though she got a six-month extension on the Friis project.
The SWCD did get a break on the price from the contractor, she said, after half a dozen picked up the specifications but only one turned it back in.
She hopes to find more funding, since former Gov. Chet Culver — who created I-Jobs — and current Gov. Terry Branstad both expressed interest in watershed management practices.
“We’re constantly looking for money,” Hagan said.
Branstand created a Watershed Improvement Review Board that is currently taking applications and is expected to award the first grants in February.
“We’ve got momentum,” Hagan said. “It would be nice to continue that momentum. There is a lot more that needs to be done.”
According to a handout on the Friis dam, the structure can reduce the peak flow from a 100-year storm by 89 percent, releasing the water in a day or two, reducing the chances that streams will overflow.
• The dam includes 170 feet of 30-inch-diameter aluminized pipe culvert for the outlet.
• It includes 22,340 cubic yards of earthfill (dirt).
• As a “high hazard dam” it can withstand a probable maximum rain of 26 inches in six hours.
• Water from the Curtis Friis farm would, if unhindered, flow first to Greenview subdivision and the houses north of Orange Street.
• To construct the dam, the farm needed to acquire permits from the Corp of Engineers and Iowa Department of Natural Resources.
The Hoover Creek Watershed Committee includes Hagan; Muckler; Hoover Association directors Ken Fawcett and Bruce Barnhart; MaryBeth Stevenson, who works for the DNR and lives in West Branch; Hoover Park Superintendent Pete Swisher; and Natural Resources Conservation Service’s Jon Matz.