Manitou Springs officials hosted Gov. John Hickenlooper on Monday afternoon for a flood briefing and a tour of sites ripe for potential mitigation work.
Before the tour, which focused on Williams Canyon and areas along Canon Avenue, public works director Bruno Pothier filled the governor in on project designs that might help prevent a future catastrophe.
Pothier described recommendations by Wright Water Engineers of Denver, which has been working with town officials since flash floods in July and August poured down ash-laden slopes in the Waldo Canyon fire burn scar and sent water and debris spilling over the banks of Williams and Fountain creeks.
The plan centers around stopping as many rocks and other large objects as possible before flows reach a 7-foot-by-7-foot culvert where Narrows Road meets Canon Avenue. The early concept designs carry of price tag of $4.1 million, Pothier said.
"The game-changer for us has been the amount of debris," Manitou Springs Mayor Marc Snyder told Hickenlooper.
Snyder stressed that the town "feels quite vulnerable" after flows from three days of mid-September storms nearly filled the culvert that runs under the bottom section of Canon. He said the culvert is about 80 to 90 percent full of rocks - so full that cleaning it out will be like a mining operation.
To stop the invasion of large objects, engineers designed eight debris barriers to be built along Williams Creek.
The first barrier would be erected where Canon Avenue meets the Cave of the Winds' property, Pothier said. It features a reinforced steel grate to capture large rocks. Seven more barriers made of steel ring nets would continue to slow the flow through the channel before it reaches the culvert. All would be able to be cleaned out after each flood.
Pothier said the designs were made to withstand stream flows of up to 2,000 cubic feet per second (cfs). Normal flows in the area are less than 15 cfs, and peaked at 1,500 cfs on Sept. 12, according to the U.S. Geologic Survey.
Hickenlooper raised concerns about stream flow rates exceeding 2,000 cfs; Snyder said the rate is based on a flood that happens about every 10 years.
Pothier, Snyder and El Paso County fire recovery manager R.C. Smith said engineers are also working on projects farther up Williams Canyon on county land. According to Smith, the county plans to install sediment retention ponds that would "take some velocity out of the water" before raging toward Manitou's mitigation work.
Manitou Springs is also working to purchase land from property owners at the mouth of Williams Canyon. Manitou officials want to install sediment retention ponds in that location just south of the U.S. 24 bridge.
Hickenlooper also raised concerns about the potential costs of the proposed mitigation work. The mayor said Manitou Springs already has $2.5 million from the town's general and stormwater funds and from the Emergency Watershed Protection program. The county is sponsoring the town for the EWP money.
He said the plans likely will be refined, and the $4.1 million price tag could be reduced.
"I do cringe a lot when I hear that number," Snyder said. "But hopefully it will be a little south of that figure."
Snyder mentioned that he and other officials in the town will solicit "philanthropic groups" to help with costs when crunch time arrives.
"Sounds like a job for El Pomar," Hickenlooper said.
DISASTER RECOVERY CENTER
The Federal Emergency Management Agency will open a temporary Disaster Recover Center in Black Forest to assist anyone who lost property or suffered damage during storms and flooding that hit the Front Range Sept. 11 to 30.
Where: Black Forest Fire Department No. 1, 11445 Teachout Road.
When: 10 a.m. to 7 p.m. Tuesday to Saturday.
Note: People can save time by registering with FEMA before going to the recovery center. Registration can be done by phone at 800-621-3362 or online by going to disasterassistance.gov.