The Pentagon's Defense Threat Reduction Agency also announced Friday that it would hold public hearings on the test in Las Vegas, Salt Lake City and St. George early next month.

The new environmental assessment contains one significant departure from previous conclusions.

In May, federal officials determined that the Divine Strake blast "would not result in the suspension or dispersion of radioactive materials or human exposure to radioactive materials."

The new environmental study contains more detailed models and reaches a contrary conclusion.

It states that older fallout particles "resuspended from the detonation, have potential to be transported outside the [test site] boundary by wind. They may, therefore, contribute radiological doses to the public."

However, the report said, models indicate that maximum possible exposure immediately outside the test site is significantly lower than the threshold at which approval by the Environmental Protection Agency would be required, and the nearest populated area, 12 miles away, would not receive any significant exposure.

There were no estimates on exposures as far away as Utah.

The May findings also said that "radioactive contamination does not exist within the area impacted by the blast." The new report notes that "low but detectable levels of man-made radioactivity were detected primarily in undisturbed surface material."

The report is a draft that may be revised and finalized after the public is given 30 days to submit comments. Then the National Nuclear Security Administration, which manages the Nevada Test Site, will determine if further study is needed or if the test has "no significant impact" and can proceed.

"I'll be going over this very carefully," said Sen. Orrin Hatch, R-Utah. "We found a number of problems with the first analysis, and we want to make sure that those have been corrected and that there aren't any other concerns that need to be addressed."

The report was delivered to the congressional offices late Thursday. Democratic Rep. Jim Matheson was also in the process of reviewing it.

The Divine Strake test would detonate 700 tons of ammonium nitrate and fuel oil to help develop computer models to simulate blasts and damage to underground targets by bunker-buster bombs.

The new environmental study was the result of questions raised about potential fallout from the test by Nevada officials as well as Hatch and Matheson. A lawsuit seeking to stop the test was filed by Utahns suffering illnesses as a result of their exposure to fallout from Cold War nuclear weapons tests in Nevada, and a Nevada Indian tribe.

The agency decided last month to proceed with planning at the Nevada site after looking at several other locations, including the Dugway Proving Ground in Utah. The Nevada site has structures embedded in limestone, similar to potential hostile targets, and it would take longer and cost more to do the test at other sites.

The blast will be about 50 times larger than the most powerful known conventional weapon and throw dust and debris thousands of feet into the air.

Pentagon budget documents originally said the test was meant to help pick the smallest nuclear weapon to destroy a hardened target, but the department has since said the inclusion of the word "nuclear" was an oversight.

The environmental study notes similar tests conducted at White Sands Missile Range in New Mexico and the Nevada Test Site - some more than six times larger than Divine Strake - between 1977 and 1993.

The Pentagon will have three public hearings on the Divine Strake test:

* Jan. 9: Cashman Convention Center, Las Vegas

* Jan. 10: EnergySolutions Arena, Salt Lake City

* Jan. 11: Dixie Center, St. George

* The draft environmental report is available at http://www.nv.doe.gov/

A new environmental study acknowledged that the experimental blast planned next year at the Nevada Test Site may disperse some radioactive materials but insists there would be no danger.

Then and now

* From May 9 environmental study

". . . the proposed action would not result in the suspension or dispersion of radioactive materials or human exposure to radioactive materials."

* From new study

"Both natural radionuclides suspended, and historic fallout radionuclides resuspended from the detonation, have potential to be transported outside the NTS boundary by wind. They may, therefore, contribute radiological dose to the public."