Boulder Avenue resident Marc Horwitz demonstrated how high floodwaters rose inside a retention dam above Boulder Avenue during a Sept. 14 rainstorm. [Photo by Rudy Herndon / Moab Sun News]

When it rains above Boulder Avenue and Jackson Street during monsoon season, it pours.

Floodwaters often inundate the two streets and neighborhoods along the west side of South U.S. Highway 191 during the late summer and early fall period. After a brief – yet intense – rainstorm swept through the area on Sept. 14, and a similar deluge struck on Sept. 30, Grand County Road Department Manager Bill Jackson thinks the time is right to talk about budgeting for drainage improvements.

That turns out to be an expensive proposition, though.

“Essentially, the bottom line is it comes down to funding,” Jackson told the Grand County Council during its regular meeting on Tuesday, Oct. 3.

The county’s storm drain master plan, which was updated in 2011, has identified about $16.21 million in higher-priority drainage improvements, plus another $23.58 million in lower-priority projects. Both estimates are based on construction costs circa 2009 – when the country was in the midst of a recession – so the actual amounts are likely to be even higher.

“In the past, when projects are brought up in dollar amounts, everybody’s jaw drops,” Jackson said.

While localized flooding can be a problem throughout the county – and the county has identified other improvement projects – Jackson’s attention turned to drainage problems in the Boulder Avenue and Jackson Street area, in particular.

Since the early 2000s, the county has built 12 retention basins to capture storm runoff – including one that sits in the drainage directly above Boulder Avenue.

In Jackson’s estimation, the retention basin above Boulder Avenue is just too small, based on the Sept. 14 storm that dumped a still-undetermined amount of rain around a fairly localized area. National Weather Service estimates for the area were significantly less than the 1-inch-plus amounts that rain gauges in Moab and Castle Valley measured that day, according to Jackson.

As the downpour raged, Jackson said that water topped right over the dam and then came right down the drainage below.

“I think it was evident in that storm,” he said. “We have another storm drainage basin on top of Overlook Road just southeast of there – same storm – it handled the water fine.”

The dam was built to the engineering specifications, Jackson said, but it doesn’t have the capacity it needs for the drainage area.

Longtime Boulder Avenue resident Marc Horwitz, who granted the county an easement for the dam on his property, disagrees, and he doesn’t see any need to enlarge the dam.

It’s his understanding that the dam was designed to hold debris, and he believes that debris loading into the dam could be reduced by installing a series of inexpensive fabric microdams every 100 feet or so.

“Water is not the problem,” Horwitz said. “The problem is the debris.”

Horwitz believes that the current dam is serving its purpose, estimating that it kept more than four dozen 10-yard truckloads of debris off the highway. He believes the system would be more effective if the microdams were in place to keep rocks, mud and other material from filling up the basin during major storm events.

“The dam would flow water much better if it didn’t get clogged with debris,” he said.

Based on Horwitz’s personal observations, the Sept. 14 storm event may have been one for the record books, even if it only lasted for five to 10 minutes from start to finish.

“It was like someone was throwing buckets of water in my face,” Horwitz said.

“This is the first time that we ever saw water rushing by our house,” he added. “It was raging past there – for five minutes.”

While Horwitz’s property was unscathed, neighbor Eddie Guerrero and his family bore the brunt of the storm.

Floodwaters from a different neighbor’s property rushed in through the Guerrero home’s dog door and filled the entire downstairs level of their home with 4 to 5 inches of water, silt and mud.

Guerrero and his family moved into the home in 2003, yet he said they never had any problems with flooding until 2013, after a neighbor removed a line of trees near the property line.

There was a break in the flooding last year, but the Sept. 14 storm brought the floodwaters back with a vengeance.

“This has been the worst I’ve ever seen,” Guerrero said.

His family can’t buy flood insurance because the area isn’t classified as a flood zone, and Guerrero said that his homeowner’s insurance doesn’t cover anything, either.

Cleanup costs have already totaled about $6,000, and he anticipates that they’ll have to spend another $5,000 to replace their carpets.

“As it stands right now, we’re on our own,” he said.

County seeks more funds for Jackson Street drainage

On the surface, at least, drainage improvements might appear to be further along on nearby Jackson Street, where a 48-inch culvert was installed about seven years ago.

But that culvert was put in before the county adopted its master plan criteria specifications, and according to Jackson, a more recent update from 2011 calls for the installation of a 72-inch culvert.

“They just put it there for future use,” Jackson said.

There are no pipes below the culvert, and no pipes above it, he said, so it isn’t serving any function right now.

“It’s plugged (at) both ends,” he said. “It’s not in use.”

Even if it were functional, Jackson said the 48-inch culvert is not big enough to accommodate the kinds of flows that were rushing down the street on Sept. 14.

“It wouldn’t have handled all that water,” he said.

Moreover, he said, the county would be exposing itself to liability if it used an undersized culvert.

According to Grand County Council Administrator Ruth Dillon, the county has set aside $200,000 for drainage improvements on Jackson Street. It can’t spend that money without matching funds, but Jackson said that county officials plan to approach Utah’s Permanent Community Impact Fund Board (CIB) for additional funds.

Boulder Avenue and Jackson Street neighborhoods among areas prone to flash flooding