上総掘り(かずさぼり)とは？

Kazusa-bori is a method of digging a deep well which was devised in the city of Kimitsu, Chiba prefecture. This area was called ‘Kazusa’ hundreds of years ago. ‘Bori’ is a variation of ‘hori’, which means digging in Japanese.

Since river terraces have been structured well along Obitsu river and Koito-river in Kimitsu city, it was difficult to have water for drinking and agricultural use in those areas. Until the early 19th century, they had been using ‘Hori-Ido’ method, where they dig pits with bare hands, and ‘Tetsubo-shiki’ method, where they dig the ground with an iron stick. However, we cannot reach more than 35m deep with those methods and thus cannot gain enough water. Then directed by Yasunosuke Omura in Obitsu area, Kyukichi Ikeda and Tokuzo Ikeda in Koito area, people tried to improve the technique.

In 1883, Omura and Kyukichi Ikeda devised ‘Kashibo-shiki’ method where they use oak wood in place of iron sticks. With lighter devices and less human power, they started to dig wells 90~110m deep. Later Omura and Tokuzo Ikeda devised a technique in which they use materials called Take-higo*¹, Suiko*² and an iron pipe at the same time. Then they reached 360~540m deep.

In 1887, Minejiro Ishii devised the Hanegi*³while Kinjiro Sawada devised the Shumoku*⁴ and Higoguruma*⁵ in Koito area, Kimitsu. It is said that around 1896, the current type of Kazusa-bori technique came out.

After that, Kazusa-bori spread across the nation as it was used for drilling oil, natural gas and hot springs. But around 1970, Kazusa-bori had become unpopular because of its big labor costs, widespread of sewage and mechanical drilling skills, and lower demand of irrigation wells.

Nevertheless, these days it attracts considerable attention as a promising technique which enable us to drill deep into the ground without any machineries. This is useful especially in developing countries that suffer from water shortage. After the Great East Japan Earthquake, there are many cases where we installed wells in homes or in public spaces for emergency use.

*¹Take-higo

a string made of bamboo which is used to hang an iron pipe inside an underground hole.

*²Suiko

a pipe made of tin. It is used for removing mud at the bottom of the hole after digging.

*³Hanegi

a pair of poles sustaining Hori-Tekkan or Suiko from above with their resilience.

*⁴Shumoku

a handle vertically driven into Take-higo. It conveys our power to the Hori-Tekkan underground.

*⁵Higoguruma

a large wheel which rolls part of Take-higo which is not in use. It stands out with the structure like a waterwheel.