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Earth fissures indicate big problem
by Jamie Hansen
Mar 24, 2010 | 14481 views | 1 1 comments | 12 12 recommendations | email to a friend | print
A long crack down a street in Enoch is an earth fissure that indicates a dropping water table in the Cedar Valley. Fissures have also been identified near Quichipa Lake.
A long crack down a street in Enoch is an earth fissure that indicates a dropping water table in the Cedar Valley. Fissures have also been identified near Quichipa Lake.
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IRON COUNTY – Just east of Minersville Highway in Enoch, a 2.25 mile crack winds through the pavement, sidewalks, and empty lots of an abandoned subdivision.

At first, the crack appears another sign of a cast off building project. In reality, it represents a problem, lying under the earth, that’s implications could affect all the water users in Cedar Valley.

Earth Fissures and Groundwater Subsidence

“Did you feel that?” said Senior Utah Geological Survey Geologist Bill Lund recently, as his colleague Tyler Knudsen drove over what felt like a speed bump in the subdivision. “A year ago, this spot was smooth as a baby’s bottom.”

The “speed bump” is part of a long and growing crack, known as an earth fissure.

Fissures, which in the west are usually a symptom of a dropping water table, were identified both in the Enoch subdivision and near Quichipa Lake last summer. Last week, the geologists were out measuring growth and changes in Enoch’s fissures as part of a study commissioned by the Central Iron County Water Conservancy District.

In this arid region, earth fissures tend to result from something called groundwater subsidence. Subsidence describes the ground sinking because of a permanent drop in the aquifer, where a watershed’s groundwater is stored. The fissures result from sediment subsiding in an uneven way, sometimes along fault lines.

They have emerged as signals of groundwater over-pumping from Arizona to California, representing what Lund called a “major land-use planning issue.”

In Utah, aerial photos show that fissures – like the one in Enoch – could have existed as far back as the 1960s. Still, their existence wasn’t known until 2005. That year, flooding in the nearby Escalante Valley eroded what had been pencil-thin cracks into deep gullies. There could many such narrow cracks in this region, Lund said.

“Until now, they haven’t hit anything anybody cared about,” he said, explaining that Utah fissures have generally shown up in undeveloped rangeland or farmland.

“This fissure,” said Lund, pointing to a six-inch high crack in the Enoch subdivision’s pavement, “went right into the subdivision and started to damage the infrastructure. That’s when Enoch City called.”

City Manager J. Bryan Dial said the street department first reported the problem.

“At first we thought it was a fault line in the Park View subdivision,” he said. “We contacted the (Utah Geological Survey), who told us they were in fact fissures. At that point, the Central Iron County Water Conservancy District was kind enough to step in and fund the study.”

Last summer, the CICWCD matched the UGS 50-50 to fund a study to determine how bad the subsidence is and what can be done about it.

Board member Leon Hyatt said at a recent CICWCD meeting that he was glad they’d chosen to do so.

“With Iron County’s demand for water expected to grow each year, this could be a big problem,” he said.

The Problem with Fissures

In the UGS’s report, due at the end of June, Lund will dedicate a section to “why fissures are bad.” He describes them as canaries in the coal mine – in this case, warning that an area is over-using its water and causing subsidence. Subsidence permanently reduces how much water the aquifer can hold as what had been free-floating sediment compacts in a cement-like way where water has dropped.

Another main hazard, Lund said, is that the fissures can provide surface water direct access to the aquifer, from which we draw our drinking water. If the water becomes contaminated, it could present a health problem – although so far, this issue has not been reported.

Fissures can also upset development, as seen in Enoch. In Arizona, they’ve disturbed freeways. In Las Vegas, people have been forced to move from their homes in an affected area. While parts of the Enoch subdivision could possibly be built on in the future, growing cracks split the road in several places. In addition, the fissures have reversed the flow of the sewage lines.

The final problem, mentioned by several people interviewed, is that fissures are difficult to predict and can show up without warning.

They persist as pencil-thin cracks for decades, only becoming visible – and a significant problem – when a flood or other geologic event enlarges them.

CICWCD Manager R. Scott Wilson said this is particularly a problem for Iron County, whose larger urban area carries greater potential for economic loss.

“Earth fissures can happen anywhere,” Lund said. “That’s why they’re so insidious.”

What’s Being Done

Lund, Hyatt and Wilson all expressed surprise that fissures have appeared in Cedar Valley so early, and to such a great extent. They also emphasized that they’re trying to get ahead of the problem by commissioning the UGS study.

“The board is sufficiently concerned about the issue that we’re trying to scope how bad it is or may become in order get ahead of the game,” Hyatt said.

The report will include recommendations for what Cedar Valley can do to mitigate the problem.

“Groundwater subsidence and earth fissures are geologic hazards, but unlike others, they’re human caused,” Lund said. “Because of that, they’re also subject to human management.”

Management will be based on recommendations from the study, and likely, the state water engineer.

The CICWCD is not in a position to impose water policy changes, Wilson said. It can, however, act as a mediator between the many parties that have a stake in Cedar Valley’s aquifer.

The CICWCD hopes to bring together Cedar City, Enoch City and agricultural water users, for instance – to discuss solutions.

Dial also expressed a desire to work with other agencies on what he and others have described as a “regional” problem.

Both Cedar City’s Manager Ron Chandler and Dial said they are aware of the area’s groundwater issues, but are waiting for the report to see what steps will be best to take.

Dial added that Enoch’s sense of urgency is lessened by the fact that there are no occupied homes in the subdivision.

“We’re concerned about (the) aquifer,” Dial said, “but we’ll have to wait and see what we can do.”

Many acknowledged that the fix likely won’t be easy. Hyatt described the impacted parties as siblings with straws, drinking up the same supply of liquid.

It’s clear those siblings have been thirsty: UGS Groundwater Geologists Mike Lowe and Paul Inkenbrandt, who have been studying groundwater levels in Cedar Valley for the UGS report, say well levels have dropped an average of 40 feet since 1939, and, north of Enoch and near Quichipa Lake, they’ve dropped closer to 100 feet.

They couldn’t disclose what recommendations they’ll be making in terms of water use, but Lowe said, “We have a chance to catch this early and take some steps (to mitigate it).”

Hyatt predicted a variety of actions will compose the eventual solution: reducing water consumption, bringing in new water from sources like the Lake Powell Pipeline, and recycling water, to name a few.

“The easy fixes for solving water problems are done (with) in the west,” he said. “We’re going to have to take some significant actions.”

Wilson described the problem as a community issue.

“Once the aquifer’s gone, it’s gone,” he said. “I think we have an obligation to future generations to not saddle them with problems that are within our reach to fix.”

Comments
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anonymous
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March 25, 2010
What a well-researched, well-written article.
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