City eyes pricey prevention of flooding off Aspen Mtn. |

City eyes pricey prevention of flooding off Aspen Mtn.

John Colson

Aspen’s elected leaders have long been convinced that some day Aspen Mountain could come sliding into the lap of the city.

But now, for the first time, the city is poised to do something about it.

A majority of the City Council this week informally endorsed a multimillion-dollar plan to deal with that possibility by enlarging the city’s storm-sewer system, so it can direct a flood of mud and debris to the Roaring Fork River.

And ultimately the city hopes to forge agreements with Pitkin County and the Aspen Skiing Co. to look for ways to prevent the mountain from sliding in the first place.

Four members of the council got their first look at what is known as the Aspen Drainage Basin Master Plan on Tuesday, presented by the WRC Engineering consulting company and city engineer Nick Adeh.

Basically, Adeh said this week, the council is being asked to adopt the master plan, which includes a set of “drainage criteria” and “mud zone regulations” that outline the most seriously threatened parts of town and what can be done to deal with those threats.

As part of the overall plan, Adeh continued, the City Council will be asked to approve a $4 million, five-year capital improvements plan to upgrade the city’s storm sewers so that they can uniformly handle a “10-year flood event.”

Currently, Adeh said, storm sewers in different parts of the city have different maximum handling capacities, ranging from a “two-year flood event” to a 10-year event. These terms refer to statistically predicted floods that happen on the average every two years, five years, 10 years, 50 years or 100 years.

The flood that inundated the Ute Avenue area in August 1999, for example, was a 10- to 15-year flood event. In that flood, roughly two inches of rain fell in a half-hour’s time or so, spilling down the eastern gulches of Aspen Mountain and causing considerable property damage.

Another recent flood was at the Aspen Music School campus on Castle Creek Road, where in 1996, a natural dam gave way on the mountain and dumped several feet of mud into a parking lot.

In addition to finding ways to deal with the potential mudflow, Adeh said, the city is being asked to open negotiations with the county and the Skico to come up with a plan for stabilizing the mountain to prevent slides from getting started.

Adeh said the projected price tag for stabilizing the mountain, in very preliminary terms, is somewhere between $11 million and $14 million.

It has taken the city three years of study, and roughly $60,000 in fees to consultants, to get to this point, Adeh said, adding that the final drainage plan is expected to cost between $150,000 and $160,000.

The city has been aware for years that there is a potential for mudslides and floods rushing down Aspen Mountain as a result of sudden heavy rainstorms when the ground is already saturated by spring runoff.

Much of the money being spent on the studies has come from the development company Savanah Limited Partnership, which built the former Ritz-Carlton – now the St. Regis Hotel – a decade ago and is now proposing to build luxury housing at the base of Aspen Mountain. The city and Savanah have been talking about what to do about the mountain’s potential to slide into the bowl where that luxury housing is planned.

“They can see there’s a problem there,” said City Manager Steve Barwick, referring to Savanah and its Top Of Mill project.

As for the overall drainage plan and projects aimed at preventing or containing the flood, Barwick said, “It’ll play out over the next few years in the budget process, mostly.”

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