In general, redevelopment projects of existing dams can significantly reduce the social, financial, and environmental impacts on a community in comparison to the construction of new dams. In addition, as redevelopment projects of existing dams can accomplish the project purpose more quickly than new construction, the expectation is that such projects will be required more frequently. Tsuruta Dam was constructed in 1966 as a multipurpose dam on the first-class Sendai River. After an unprecedented flood in July 2006, a redevelopment project of the dam began in April of the following year (2007). The project was required to minimize the effect to the flood control function of Tsuruta Dam and to minimize the effects to the power generation company, the dam user. Construction work of the upstream-side cofferdam included a reservoir construction at a significant depth of 60 m or more and a dam body drilling work, and had to be conducted under a complicated and tight schedule. This paper is intended to summarize the Tsuruta Dam redevelopment project as an introduction of the experience and technology obtained and provide some lessons to future redevelopment projects of existing dams.

1. [1] A. Kubo, K. Tohyama, and S. Simomura, “Overview of the Tsuruda Dam Redevelopment Project (No.1),” Engineering for Dam, No.311, pp. 50-62, 2012 (in Japanese).
2. [2] A. Kawano, “Toward for Tsuruda Dam is popular among locals – history in the half century since the first operation,” Engineering for Dam, No.370, pp. 79-84, 2017 (in Japanese).
3. [3] K. Kaji, J. Kawamoto, and S. Yamada, “Floating-type upstream-side cofferdam of the Tsuruda Dam Redevelopment Project,” Engineering for Dam, No.339, pp. 62-65, 2014 (in Japanese).
4. [4] Y. Takayama, R. Iwamoto, and S. Yamada, “Tsuruda Dam Redevelopment Project – expansion of water discharging facilities,” The Dam Digest, No.859, pp. 17-29, 2016 (in Japanese).
5. [5] K. Kaji et al., “The large scale dam body drilling in the Tsuruda Dam redevelopment project,” Large Dams, No.238, pp. 98-104, 2017 (in Japanese).
6. [6] Y. Takayama, “Plan of Redevelopment and construction with Tsuruda Dam is in operation,” Engineering for Dam, No.350, pp. 66-75, 2015 (in Japanese).
7. [7] N. Takiguchi and T. Kanbe, “The largest Dam redevelopment project in Japan – the Tsuruda Dam facility reconstruction,” Large Dams, No.231, pp. 82-88, 2015 (in Japanese).