News & Notes
Vol. 26
Autumn 2003
Attaining Harmony between Dams and Nature

In Japan, a land of many mountains and short rivers with rapid currents, numerous dams have been constructed over the years to serve a variety of purposes, including irrigation, flood control, and power generation.

In this feature article, we examine the latest trend in environmental protection, dam redevelopment, and laborsaving construction techniques and discuss the role Kajima plays in the field of dam construction in Japan. We also report on the potential for utilizing these new concepts and technologies developed in Japan for projects overseas.
Naramata Dam
Naramata Dam, Gunma Prefecture: one of the greatest rockfill dams in Japan
Building Dams That Exist in Harmony with Nature

In recent years, a movement to promote environmentally conscious dams has taken root in Japan. Construction of a dam is preceded by meticulously conducted field surveys and studies to ensure that environmental impact in the surrounding area and drainage basin is minimal while achieving the dam's performance and required functions.

What measures are being implemented to ensure that the dam exists in harmony with nature? To start with, there is the restoration of habitats for flora and fauna by means of environmentally conscious design. For example, planting the slopes of mountains bulldozed during dam construction with plant species indigenous to the area instead of bringing in introduced plants previously selected for their quickness to root. Moreover, there is the creation of biotopes (habitats for diverse species) to restore and reproduce the habitats of flora and fauna affected by dam development and protection of precious wildlife species such as the golden eagle and hawk eagle. The effective use and recycling of materials generated in connection with construction is also important to reduce waste. Stringent water quality control at the construction site requires that drainage is released into rivers only after being collected and purified at a water treatment plant to protect a river's water quality.

These activities show that achieving a dam that exists in harmony with nature requires not only adopting an environmentally friendly designed dam itself but also continuous effort to restore and maintain nature in the surrounding areas.
Hayachine Dam
Hayachine Dam, Iwate Prefecture: a multiple concrete gravity dam
used for flood control and supplying city water
Reinforcement work for main dam ofYamaguchi Reservoir
Reinforcement work for main dam of Yamaguchi Reservoir,
Saitama Prefecture
Dam Restoration

In recent years, construction projects to restore the functions of existing dams whose goals are to reverse deterioration of performance due to sedimentation and aging of discharge facilities, enhance existing dam functions, or bring dams into compliance with new structural standards have been attracting considerable attention. Not only are these projects of great environmental significance, they are also important from the standpoint of making effective use of existing dam stock. What construction methods and new technologies are brought to bear to comply with requests to restore existing dams?

There are many methods of dam renewal: the raising of the body of an existing dam, the new construction, reconstruction, or augmentation of administrative facilities such as water intake and discharge facilities, and the prevention of dam sedimentation by means of reservoir excavation or dredging. Projects are also carried out to enhance the effective impoundment function by connecting nearby existing dams with channel tunnels and supplementing impoundment capacity. To ensure safety even in the event of an earthquake on the scale of the Kobe Earthquake, nowadays considerable attention is being paid to making dam bodies themselves earthquake resistant.
Kajima Dam Technologies Open the Way to a New Era in Dam Construction

Various new technologies that have arisen out of Kajima's wealth of past achievements in dam construction have not only enhanced dam functionality and safety but also borne considerable fruit in the areas of processes and costs. Let's look at the new technologies and solutions Kajima plans to introduce in the future.

To speed up and rationalize design and construction planning, every year Kajima has unremittingly continued to engage in technical development in every process from planning, design, construction, and maintenance. These efforts include the research, and development of laborsaving construction methods and IT construction methods that fully utilizes computers and dam CAD systems. It is no exaggeration to call Kajima the leading company in the construction industry in the area of computerized construction. Furthermore, we have contrived rationalization measures for curbing costs that involve avoiding use of specialized machinery as far as possible and making use of general-purpose equipment employed in ordinary civil engineering work.
Second construction stage for the Takizawa Dam
Second construction stage for the Takizawa Dam, Saitama Prefecture:
a multipurpose gravity dam currently under construction on the Nakatsu River
Kajima Technologies Are Widely Applicable Overseas

Capitalizing on the technologies and expertise cultivated in Japan, Kajima engages in dam projects in areas around the world, the Wonorejo Dam in Indonesia, the Dhauliganga Dam in India, and the Kukule Ganga Dam in Sri Lanka, to name just a few. What is more, Kajima meets the needs of clients through the uncompromising practice of overall QCDSE (Quality, Cost, Delivery, Safety, Environment) management. How is Kajima able to minimize costs in such diverse countries and regions as Asia, Africa, China, and India while still maintaining the required quality? The key is to introduce methods that have proven successful in Japan: the effective utilization of materials generated in construction, rationalized construction, and computer-assisted construction. The techniques of rationalized construction (for instance, the roller compacted dam concrete method, the extended layer construction method, the cemented sand and gravel method, and the concrete face rockfill dam method) and computer-assisted construction play a critical role in projects overseas, just as they do in Japan. The fact that Kajima possesses these construction technologies has already become widely recognized overseas and serves as a powerful selling point.

Needless to say, the progress made in dam technologies to date in Japan has been underpinned by the efforts of engineers who have been engaged in dam projects for many years and of Kajima as a whole. It is to be hoped that the passion and pride of these engineers will increasingly spread throughout the world in the coming years and bring about still more dams that exist in harmony with nature.
Wonorejo Dam
Wonorejo Dam, Indonesia: a multipurpose dam used for water supply,
flood control and power generation
Vol. 26
Autumn 2003
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