A tiny bat that's up to 2 inches long and weighs a quarter of an ounce is delaying progress on construction of the next section of the Southern Beltway along the Washington-Allegheny county line.

Pennsylvania Turnpike Commission officials have disclosed they're now required to determine if the endangered Indiana bat lives in the 13.3-mile alignment where the limited-access highway is to be built from a new Interstate 79 interchange north of Canonsburg to Route 22 in Robinson. There, it would hook up with the beltway's Findlay Connector, which is currently open to Pittsburgh International Airport.

If the corridor is part of the bat's habitat, the Federal Highway Administration may not sign off on a final Environmental Impact Study or issue a Record of Decision necessary for the turnpike commission to start acquiring property by the end of the year as planned.

Consequently, dozens of property owners living with uncertain futures since the Southern Beltway proposal was conceived more than 15 years ago may have to wait even longer.

Dave Zazworsky, a former Pennsylvania Department of Transportation administrator serving as special adviser to the turnpike commission for toll road expansion projects, said the U.S. Fish and Wildlife Service recently raised the issue of the Indiana bat, which spends summer months living throughout the eastern United States but clusters together and hibernates in a few caves over winter.

The Indiana bat, a tiny brown mammal closely resembling some other species of bats, has been found in Greene County, northern West Virginia and the Allegheny National Forest.

Bats are the only major predator of night-flying insect pests such as mosquitoes and are considered a significant part of the ecosystem. The Indiana bat has been on the endangered species list since 1967.

Mr. Zazworsky said the possibility that beltway plans could be halted because of the bat and officials would need to develop another alignment is a "worst-case scenario."

"But we have to do this extra survey and testing," he said, admitting he's frustrated because state officials had promised the turnpike commission would begin property acquisitions later this year.

"We're not here to throw rocks at anyone but to try to expedite the testing," Mr. Zazworsky told a meeting of the Mon-Fayette Expressway-Southern Beltway Executive Committee last week at the Holiday Inn-Meadow Lands. "If we find the bats, they must be dealt with. This isn't holding us up right now, but it could."

The commission is seeking offers from real estate firms that would handle property acquisitions. It has $67 million set aside for continuing work on the stretch of future toll road.

In addition, the region's transportation plan has been amended to show the turnpike commission plans to sell bonds to raise $578 million toward construction and related activities.

Environmental documents submitted to the FHWA two years ago showed these right of way impacts:

• Acquisition of 72 homes in Cecil, 21 in South Fayette and 12 in Robinson; eight small businesses; and a total of 1,482 acres.

• Compromising seven small farms totaling 92 acres, although two have been purchased by the U.S. Department of Veterans Affairs for its National Cemetery of the Alleghenies along I-79 at the Cecil-South Fayette line.

• Closing or abandoning 34 private water wells and 41 oil and natural gas wells.

• Replacing 7.45 acres of wetlands and relocating or otherwise providing for eight streams.

"One of the priorities of the designers will be to minimize these impacts," turnpike commission spokesman Joe Agnello said. "For example, we believe the actual number of residential displacements will be closer to 75 than 105."

In addition to interchanges at I-79 and at Route 22, the next section of the Southern Beltway includes intermediate interchanges at Beech Hollow Road and at Fort Cherry Road, both in Robinson, and at Cecil-Sturgeon Road-Route 50 in Cecil. A mainline toll plaza would be established south of McDonald.

The project has been broken into three parts for the preliminary design, scheduled for completion in 2009.

Based on a timetable released at last week's meeting, the turnpike commission and its consultants have estimated completing the middle section of the Southern Beltway in 2015 or 2016.

The third and final section involves up to 16 miles of toll road from I-79 southeast to the Mon-Fayette Expressway north of Finleyville. It's in the draft environmental study stage and, therefore, not as far advanced as the I-79-to-Route 22 section.