A biotope is a concept initiated in Germany, can be defined as a area where several living organisms, that can support themselves without external intervention. This concept can be similar to "habitat", but the main difference is that "biotope" refers to an entire biological community, while habitat refers to a species or specific population. Japan has embraced this concept and has begun to include it in many areas of social planning.

Without any action to prevent it, after the construction of the multipurpose Miyagase Dam and subsequent reservoir could have had an adverse impact on the surrounding environment. The "Miyagase Dam Environmental Protection Scheme" was formulated. This scheme included provicions to ensure that "the areas used for dam construction had to be designated for environmental recovery and compensation".

CTI took charge of the research, design, implementation plan and follow-up monitoring of the biotopes that were created in the areas where sludge resulting from excavation work was disposed . Four sites were created: the Higashizawa biotope, the Oizawa biotopes (Ravine Forest and micro-fauna forest ), and the Washigasawa Biotope.