Archaeologists hired by Luke Air Force Base will excavate seven sites where hundreds of Native American artifacts have been found to clear the way for construction of the military's largest solar array.

Base officials were aware of the artifacts sites before recently launching a project to install more than 50,000 solar panels manufactured by SunPower Corp. The panels, paid for by Arizona Public Service Co., would generate power that the utility company would sell to its Valley customers. Luke would receive a fixed electricity rate for providing land for the panels.

Federal and state laws require agencies like the military to preserve historic artifacts before building on federal or state land and to consult with various groups. For the Luke project, officials have invited 16 Arizona tribes, the State Historic Preservation Office, the Washington, D.C.-based Advisory Council on Historic Preservation, and Glendale to weigh in. Tribal leaders will tour the sites next week.

"The tribes do need to be a part of the process," said John R. Lewis, executive director of the Inter Tribal Council of Arizona. "They take that very seriously."

Such sites may include ceremonially significant artifacts that tribes want to reclaim, he said. Human remains and funerary materials must be reburied. And other artifacts may serve to document the history of the tribes.

The process could delay the solar project.

Base officials hope to begin excavating the sites in October and begin installing solar panels in January, said Jeff Rothrock, Luke's environmental chief.

But other projects have taken months to work out formal agreements with tribes and historic-preservation agencies on how artifacts should be collected, said Ann Howard, senior archaeologist at the State Historic Preservation Office.

Another factor is how extensive the archaeological discoveries are.

On an initial survey of the land, private Tucson archaeological firm Statistical Research Inc. found well-preserved pottery shards, stone hammers, grinding tools, arrowheads, a shell and burned rocks, indicating areas that were used for making tools and cooking, according to a draft report.

Collecting those items would take less time. But the sites could hold ruins of homes or hearths underground. Nearby digging in previous years failed to turn up features below the surface, but the likelihood of their presence is high, the report says.

Finding an underground room could require archaeologists to spend more time excavating, Rothrock said.

"It's a wild card," he said. "Depending on how substantial they are, we may be able to deal with the current construction schedule." If not, construction crews may build around the sites until archaeologists finish.

The artifacts are believed to come from the Formative Hohokam period or earlier Archaic period, from 300 B.C. to A.D. 1400.

After excavating, Statistical Research plans to study the items and publish research. Luke officials will arrange public outreach such as an event or brochure if significant historical discoveries are made.

The items then will be archived in a private, climate-controlled Air Force facility in Gila Bend.