Construction of temporary road in steep valley using EDO-EPS

The upper reaches of the Arakawa River, a primary river flowing into Tokyo Bay. Futase Dam is located in Otaki, Chichibu City, Saitama Prefecture, at the confluence of the Arakawa River and the Ooobora Horogawa River. It is a 95m high concrete arch gravity dam completed in 1963, with a total water storage capacity of 26.9 million m3. The reservoir has a capacity of 21.8 million m3, and is responsible for preventing downstream flooding, providing stable irrigation water, and generating hydroelectric power for 60 years. However, the siltation of the dam is progressing every year, and in 1989, a sand dam was built on the Arakawa River upstream of the "Lake Chichibu" dam reservoir to control the inflow of sediment. Similarly, the construction of a sand dam was planned for the upper reaches of the Oodo River, and the construction of an access road to the riverbed of the dam reservoir with a height difference of about 60 m in the deep V-shaped valley was necessary. to Okuchichibu.

The EDO-EPS construction method, an ultra-lightweight embankment method, was used to construct this access road. In a deep and steep valley like our site, if we were to construct a road using conventional embankments, there would be a risk of the road collapsing under its own weight. The construction method was chosen because it can be easily carried out by hand due to the light weight of its components, making it more effective at sites where large construction machines cannot enter due to local conditions.

The access road constructed is being used for disaster relief work to remove a large amount of soil and sand accumulated in the Ohoro River. in the 2019 Storm No. 19 disaster.