Thursday, December 24, 2009

New earth fissure maps in Cochise and Pinal counties released

AZGS has released new Earth fissure maps for the Dragoon Road Study Area in Cochise County [right] and the Greene Wash Study Area in Pinal County.

In the Dragoon Road area, AZGS geologists identified more than 3.5 miles of continuous and discontinuous earth fissures. The fissures constitute a narrow network of north‐south trending features, from just south of the intersection of Dragoon Road and S Cochise Stronghold Road, north towards the intersection of W. Haywire Road and U.S. Route 191.

An additional two miles of reported but unconfirmed fissures are shown on the map. This includes nearly 3000 feet of fissure previously known to underlie the ash and sludge storage ponds at the Apache Station Combustion Waste Disposal Facility operated by Arizona Electric Power Cooperative. (The storage ponds are situated at the southwest end of Willcox Playa, just east of South Cochise Stronghold Road.) Fissures were first reported there in March 1993 and 1200 feet of fissure were mapped during the permitting stage of the storage ponds. At the same time, a geophysical study identified a buried, incipient fissure that continues north to the north section line of Section 04, T16S, R24E.

Because of the earth fissure, the storage pond system constructed in 1994 was modified to include a second geomembrane liner. In June 2009, the Environmental Protection Agency posted a “High Hazard Potential rating” for the seven Apache Station Combustion Waste Disposal Facility ponds. This rating does not infer problems with structural quality, but simply indicates the potential for loss of life should the containment fail.

The Greene Wash area, located about six miles south of Arizona City, hosts 3.5 miles of identifiable continuous and discontinuous earth fissures. Reported but unconfirmed earth fissures total an additional 5.5 miles. Some of the unconfirmed fissures occur in active farmlands, where seasonal plowing can obliterate the surface expression of fissures.

[this post taken in large part from our publication announcement]

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