High hazard dams

State records show that eight unsafe dams loom upstream from Salt Lake City. Three others sit above Provo. Four are above the Ogden area. Eleven sit above the wall-to-wall cities of Davis County.

In fact, state officials say 121 unsafe dams are perched above populated areas in 26 of Utah's 29 counties and would likely kill people if they fail. "It's not that they are crumbling and are ready to fall down immediately — they're not. But they don't meet minimum standards of safety. And in some sort of extreme event, like major flooding or an earthquake, they are not considered safe," said David Marble, assistant state engineer for dam safety.

That may be disconcerting as this year's mountain snowpack is far heavier than during the recent extended drought, posing a tougher-than-in-years test for dams during upcoming spring runoff. One dam in Utah has already partially failed this year (the first in four years), with tense moments occurring elsewhere amid early flooding.

But the good news is that big strides have been made to improve Utah dam safety over the past 15 years. The most dangerous dams have been repaired or replaced (and repair work disclosed they often were in worse shape than feared). Governments also vastly improved monitoring of major dams.

"But we still have a long way to go," Marble said. At recent spending levels, decades could be needed to fund all the upgrades needed at those 121 unsafe dams. Meanwhile, officials hope for no more repeats of the 89 full or partial dam failures that have occurred in Utah historically.

Making progress

A computer-assisted analysis of state records shows Utah has made much progress since the last time the Deseret Morning News looked in-depth at the condition of state dams — 17 years ago in 1988.

At that time, officials rated as safe a mere 7 percent of those dams classified as "high hazard," defined as those where failure would likely kill people and cause extensive damage. (Also, that 1988 story reported that several Utah dams had broken in the '80s after not acting on earlier federal studies that warned they were unsafe).

In comparison, now 44 percent of such Utah "high hazard" dams meet all minimum safety standards — more than a sixfold improvement. But that still means 56 percent of such dams are considered unsafe during extreme events.

A few months after the old 1988 Deseret News story, one of the few dams that was then considered to be safe — the then relatively new, 4-year-old Quail Creek Dike on the Virgin River — broke early on New Year's Day 1989.