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Earth fissures becoming commonplace
Curtis Elliott
San Pedro Valley News-Sun
Desiccation cracks, which can wreak havoc for property owners, may exist in St. David according to Todd Shipman, research geologist with the Arizona Geological Survey.
"Earth fissures are now going through some people's properties," said Shipman. "I'm not giving you all doom and gloom. The best thing is to know that fissures are there. You can prevent water from getting to them by adding dirt."
The San Pedro Basin is attracting a lot of attention these days among geologists. The Community Watershed Alliance gathered last Wednesday to discuss concerns that affect property owners. Shipman was one of a host of guest speakers, most of whom are involved in projects monitoring the San Pedro Basin.
Shipman explained that earth fissures are the result of decades of groundwater pumping. As water was removed, the land sank, and then when it rained, the clay soil dissolved into cracks. With the cracks, a development of a large gully may occur.
"In 2005, storms occurred which helped to notify the public of the conditions," Shipman said. "If there is shallow bedrock, fissures can occur."
"Adverse effects of desiccation cracks are that some create gulleys, and a bus-sized pothole opened up in Willcox. A lot of erosion can cause huge gaping holes and ultimately hazards for cattle and other things."
Shipman advised consulting a geologist before deciding to build in a certain area.
"The middle of St. David has smectitic clay and collapsing soil that expands when it gets wet," Shipman pointed out. "When it dries, it may contract or do nothing. If it's beneath a house, the change from getting wet to dry and back again can cause shifting."
Jesse Dickinson is leading the collection of hydrologic data in the Middle San Pedro area.
"We study the discharge, storage and changes in storage and directions of groundwater flow over time," Dickinson said. "This will let us construct a model.
Dickinson and his team are coordinating data from the air and the ground. They are also using a process known as interferometry.
"It takes images to compare differences between wavelengths. From an image, we can identify areas of fissures. We're trying to promote using this imagery in the San Pedro Valley," Shipman said.
Another speaker, Sandy Kunzer, is looking for volunteers to help the CWA (Community Watershed Alliance) collect ground water data.
Kunzer and his wife have been compiling data in San Pedro Valley since 2001.
Kunzer said, "We want to have years worth of data. This will be a trial year. We need to get 200 individual landowners to give us permission to find where water is."
Kunzer points out that you don't have to be a geology expert to participate.
"It only takes two hours of training," he said. "Volunteers will be organized into teams that will cover a 37-mile stretch from Escalante Road in St. David to north of Pomerene. The teams will measure and record where there is flowing or standing water in the river using the GPS units and paper record sheets."
To be a member of Kunzer's team, call or e-mail CWA at 520-609-2738, or call Kunzer at 520-803-8490 or email at sbkunzer@theriver.com.
San Pedro Valley News-Sun
Desiccation cracks, which can wreak havoc for property owners, may exist in St. David according to Todd Shipman, research geologist with the Arizona Geological Survey.
"Earth fissures are now going through some people's properties," said Shipman. "I'm not giving you all doom and gloom. The best thing is to know that fissures are there. You can prevent water from getting to them by adding dirt."
The San Pedro Basin is attracting a lot of attention these days among geologists. The Community Watershed Alliance gathered last Wednesday to discuss concerns that affect property owners. Shipman was one of a host of guest speakers, most of whom are involved in projects monitoring the San Pedro Basin.
Shipman explained that earth fissures are the result of decades of groundwater pumping. As water was removed, the land sank, and then when it rained, the clay soil dissolved into cracks. With the cracks, a development of a large gully may occur.
"In 2005, storms occurred which helped to notify the public of the conditions," Shipman said. "If there is shallow bedrock, fissures can occur."
"Adverse effects of desiccation cracks are that some create gulleys, and a bus-sized pothole opened up in Willcox. A lot of erosion can cause huge gaping holes and ultimately hazards for cattle and other things."
Shipman advised consulting a geologist before deciding to build in a certain area.
"The middle of St. David has smectitic clay and collapsing soil that expands when it gets wet," Shipman pointed out. "When it dries, it may contract or do nothing. If it's beneath a house, the change from getting wet to dry and back again can cause shifting."
Jesse Dickinson is leading the collection of hydrologic data in the Middle San Pedro area.
"We study the discharge, storage and changes in storage and directions of groundwater flow over time," Dickinson said. "This will let us construct a model.
Dickinson and his team are coordinating data from the air and the ground. They are also using a process known as interferometry.
"It takes images to compare differences between wavelengths. From an image, we can identify areas of fissures. We're trying to promote using this imagery in the San Pedro Valley," Shipman said.
Another speaker, Sandy Kunzer, is looking for volunteers to help the CWA (Community Watershed Alliance) collect ground water data.
Kunzer and his wife have been compiling data in San Pedro Valley since 2001.
Kunzer said, "We want to have years worth of data. This will be a trial year. We need to get 200 individual landowners to give us permission to find where water is."
Kunzer points out that you don't have to be a geology expert to participate.
"It only takes two hours of training," he said. "Volunteers will be organized into teams that will cover a 37-mile stretch from Escalante Road in St. David to north of Pomerene. The teams will measure and record where there is flowing or standing water in the river using the GPS units and paper record sheets."
To be a member of Kunzer's team, call or e-mail CWA at 520-609-2738, or call Kunzer at 520-803-8490 or email at sbkunzer@theriver.com.
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