TOKUSHIMA -- Residents of the city of Tokushima were officially notified Thursday of a Jan. 23 plebiscite on the controversial Yoshino River dam project -- the first such vote to be held on a central government-initiated major public works plan. The plebiscite will ask local voters whether they support construction of the dam. Although the outcome is not legally binding, a majority of "No" votes against the 103 billion yen project will have a major political impact not only on the dam itself but on other public works projects facing similar opposition. As agreed upon by members of the city assembly, the votes will not be counted if less than 50 percent of the electorate turns out. There were 209,320 eligible voters in the city as of Thursday. Citizens' groups and environmentalists opposing the dam are stepping up their campaign to urge local residents to go to the polls. The Construction Ministry's local office, on the other hand, opened a temporary office Thursday in a hotel to explain the benefits of the project to the public. The room will be open through Jan. 22. The project calls for demolishing a 250-year rock barrier at the river and constructing a dam with floodgates. The ministry says the current rock barrier cannot withstand major floods and is thus a threat to people living near the river. However, opponents say construction of a new dam will only degrade water quality and waste taxpayer money. They say that repairing the barrier and creating embankments will solve the problem posed by major floods. The plebiscite is a result of strenuous efforts by civic groups to have the voices of local residents heard. The dam was originally planned in 1982. The ministry set up a panel of experts to examine the validity of the project in 1995, and the panel gave the green light in July 1998. However, civic activists complained that the panel members were unfairly selected so as to exclude those who questioned the project. They also pointed out that the project has various flaws. Frustrated that the opinions of local residents had not been reflected in the decision-making process, a citizens' group was set up in September 1998 to enact a city ordinance to hold a plebiscite on the project. The group collected 101,535 signatures, or nearly half of the local electorate, and submitted the petition to the assembly in January 1999. After the assembly rejected the petition last February, the group fielded five candidates in the municipal assembly election in April. The election resulted in a change in the power balance at the 40-seat assembly. Three of the five candidates backed by the civic group won seats, raising the number of those who back the plebiscite to a 22-member majority. The Construction Ministry meanwhile maintains that it will promote the project regardless of the plebiscite outcome. Last April, then Construction Minister Katsutsugu Sekiya said -- at one point after the Tokushima Municipal Assembly election -- that the ministry would scrap the project if a majority of the Tokushima electorate oppose it in a plebiscite, only to retract the remark later. His successor, Masaaki Nakayama, told reporters Tuesday in Tokyo that a dam such as the one planned for Tokushima is not suitable for a plebiscite, saying decisions on such projects require technical and scientific knowledge.