Click image for enlargement. Graphic by Mike Johnson.

Nevada environmental officials have halted a massive, non-nuclear explosion scheduled for June 2 at the Nevada Test Site until the federal agency hosting the blast shows it will comply with air quality standards and that hazardous particles can be tracked, letters released Tuesday reveal.

The National Nuclear Security Administration "is prohibited from allowing this test to proceed until authorization from NDEP (the Nevada Division of Environmental Protection) has been received," the state division Administrator Leo Drozdoff wrote in a letter sent Friday to test site manager Kathleen Carlson.

The letter refers to an April 28, 2005, request to Carlson from the state Bureau of Air Pollution Control.

"To date, the NNSA has not responded to this information request. NNSA is reminded that no approval was received. ... In order to conduct this test, NNSA needs to provide all information and demonstrations required," Drozdoff wrote.

Kevin Rohrer, a spokesman for the National Nuclear Security Administration's Nevada Site Office, said his agency will provide the requested information to the state "within two weeks."

"What the state wants to see is further analysis and computer modeling of any plume that might be generated from this to ensure that any emissions are still within the threshold established in our air permit," Rohrer said.

He said initial calculations based on detonating 900 tons of ammonium nitrate fuel oil solution in a 30-foot pit show the blast will be in compliance with the test site's air permit that was issued in June 2004.

The Defense Threat Reduction Agency, which wants to conduct the test above a limestone tunnel, intends to use a smaller amount of ammonium nitrate fuel oil solution, 700 tons.

"We believe we're going to be well below the threshold," Rohrer said.

The state's April 2005 request seeks documentation that identifies hazardous pollutants that will be carried by the explosion's mushroom cloud. It also calls for documentation that demonstrates that state and federal air quality standards will be met. The information is required under an existing air quality permit for operating the government's test site, 65 miles northwest of Las Vegas.

In a statement issued Tuesday, Steve Robinson, Gov. Kenny Guinn's deputy chief of staff, said: "The governor's office expects the NNSA to fully comply with all applicable state environmental rules and regulations before any testing is done."

Drozdoff's letter was written the same day that Citizen Alert, a statewide environmental group, called for the Defense Department and Energy Department to halt the Divine Strake blast, claiming it is unnecessary and could send surface contamination from previous atomic bomb tests into the air.

When told Tuesday about the state blocking the explosion until air quality compliance is demonstrated, Citizen Alert Executive Director Peggy Maze Johnson said she was delighted. But, she added, the calculations and modeling should be done by independent air-quality experts.

"Instead of NNSA hiring their contractors to do what the state wants, they need to bring in an independent study group to do that, somebody who isn't on their payroll and doesn't owe them," she said.

The Divine Strake blast is aimed at developing technology for weapons to penetrate "hardened and deeply buried targets," according to the Defense Threat Reduction Agency.