Waterfront businesses could lose $65 million of value during construction of the replacement to the viaduct, but may gain up to $250 million in increased property values, according to a study presented to the Alaskan Way Viaduct Stakeholders Advisory Committee Thursday,

The study, by ECONorthwest, showed "no change in the economic activity in the region," said Ron Paananen, deputy director of the Urban Corridors Office at Washington State Department of Transportation, during a press conference Thursday afternoon.

The areas affected worst - such as the Seattle waterfront - are a small percentage of the Puget Sound regional economy. The study compared local impacts against the total economic activity in Puget Sound.

"The biggest concern is the perception of impacts," Pannanen said, "impacts that may not be realized."

Economist Terry Moore presented his analysis of the economic impacts to the Alaskan Way Viaduct Stakeholders Advisory Committee Thursday evening. Moore is the vice president and senior planner for ECONorthwest, a consulting firm which applies economic analysis to public policy, transportation and land use.

Moore said the economic impacts are worst for the waterfront businesses during the demolition of the viaduct and the construction of its replacement.

"That's Zone Zero where the biggest impacts will occur," Moore said.

Comparisons were made between the replacement scenarios and a baseline, "no build" situation, where the viaduct is demolished in 2012 and nothing else is put in its place. The economic models assumed unmitigated, construction-efficient building of a replacement, and studied the economic impacts during construction, and after completion.

The four-county region studied - including the economic activity of King, Snohomish, Pierce and Kitsap counties - employs 2.3 million people and generates $350 billion a year. The impact to the Seattle waterfront, overall, is small.

"I'm not saying it will be pleasant," Moore said, "but it's not going to be precipitous."

Building a cut-and-cover tunnel or a lidded trench will affect the waterfront the worst with extensive excavation on Alaskan Way. The bored tunnel affects the waterfront least, at least until the viaduct is demolished after the tunnel is opened, though that project has the longest construction time.

The impacts to waterfront businesses may be minimized by scheduling construction around the summer tourist season and clever staging of materials. This is difficult to do while excavating a waterfront tunnel because, Paananen said, "we have to get in, stay in and finish the work."

And the type of businesses on the waterfront - small retail shops, with low profit margins, close to construction, relying on walk-in customers such as tourists - are especially vulnerable. Up to 300 parking spaces now under the viaduct will be lost to most scenarios.

The businesses that survive, or return after five-to-seven years of construction, have the most to gain, Moore said. With a quieter waterfront, new open space and new views, existing properties could see values increase $50 to $250 million.

The Alaskan Way couplet with Western Avenue, and all three tunnels, offered the most gains for waterfront properties, while two surface highways scenario offered modest increases.

The two elevated highways offered the least increases to property values. But the integrated elevated, with the highway running underneath a park lid, would offer more business opportunities for retail and office spaces underneath the structure.

Still, Moore's economic simulations showed 10 to 25 percent of businesses may leave the waterfront during construction, at a loss of $50 to $100 million.

"I'm not confident that we are going to lose $65 million a year, but it's on that order of magnitude," Moore said. "I am confident it's not $6 million and it's not $600 million."

The numbers are much less than reported two years ago. Then, Hebert Research studied the impact of a 42-month, total closure of the viaduct to build a cut-and-cover tunnel, and found $3.4 billion lost annually from waterfront businesses. Even with business moving nearby, the report still predicted losses in King County at more than $2 billion.

The Hebert study presumed the 110,000 vehicles that use the viaduct daily "disappear from the system," explained Ron Posthuma, assistant director for King County Department of Transportation, during the press conference Thursday. In contrast, he said the most recent travel models show all the trips will be made, if not in cars on the viaduct, then on streets, on I-5, in buses, or to elsewhere in the county.

"This time we include access to businesses on the waterfront and maintain throughput with detours, reroutes, and mitigation," Posthuma said. "It's a different kind of analysis."

In his study, Moore used case studies of other cities, local focus groups and interviews, and questionnaires of local businesses. The economic impacts were calculated from the traffic models, which already show increased times for commuters and moving freight after the viaduct is replaced, little reduction in trips taken.

The Port of Seattle will be less affected by construction on the central waterfront starting in 2012, using the new southern half of the viaduct, its interchange at King Street, and new SR-519 ramps, to get freight to the interstate and the rail yards.

Local deliveries and vehicles using the viaduct for trips through the city will be more affected, with longer travel times through construction, and on any surface roadway completed on the waterfront.

The economic impact study was one of the last of 27 measures evaluating the eight scenarios.

The advisory committee will get more details and have questions answered at an additional workshop 5:30 p.m. Monday in the Bertha Landes Room at city hall.

The building blocks for these scenarios will be reassembled into two or three "hybrid" scenarios and presented to the stakeholder advisory committee Thursday, Dec. 11.

A final solution will be presented to the mayor, the county executive and the governor by the end of the year.

Matthew G. Miller is a freelance writer living in the Admiral District. He may be reached through wseditor@robinsonnews.com.