Photo/IllutrationThe Umenokidai No. 1 tunnel in Kimitsu, Chiba Prefecture (Kyota Tsutsumi)

  • Photo/Illustraion
  • Photo/Illustraion
  • Photo/Illustraion

KIMITSU, Chiba Prefecture--Tunnels dug by hand out of limestone hillsides decades ago by local residents seeking quicker access around the Boso Peninsula are showing their age, and authorities here decided it was time something was done before an accident occurred.

Fashioned mostly with picks, years of wear and tear are showing, and nearly all of the passages require a degree of shoring up and other reinforcement work to ensure they remain safe.

The city government is planning to conserve 22 of the hand-dug tunnels, and has earmarked 612.34 million yen ($5.4 million) for repairs to them and 10 other ordinary tunnels.

Although the primitive interiors are enough to make the uninitiated ponder the wisdom of entering, the humble charms of the routes have attracted droves of outside visitors in recent years.

Many tunnels are still in daily use, and the local government is responsible for ensuring that appropriate safety precautions have been taken and proper maintenance is carried out.

City officials started reinforcing and repairing the tunnels in March.

One tunnel, the 85-meter long Umenokidai No. 1, comes out near a lake formed by the city's Mishima dam.

The tunnel is narrow, with barely enough space for a compact car to pass without scraping its sides. The entrance is reinforced, but the interior remains bare and retains the marks left by chiseling through the soft rock. It looks more like a natural cave than man-made.

The other end is not visible from the entrance because of a sharp curve, a feature that prompts locals to refer to the passageway as the “L-shaped” tunnel of Mishima dam.

City government workers are due to coat the tunnel walls with liquid concrete before current fiscal year finishes at the end of March.

The No. 1 tunnel leads to the Umenokidai No. 2 tunnel, which is about the same length but has no reinforcements. Nor does it have a sharp curve, although a smaller passageway branches off through which people must walk single-file. It leads to an opening at the foot of a steep cliff from which the reservoir created by the Mishima dam is visible, as well as a small shrine, about 1 meter tall, that is wedged into the cliff.

The city of Kimitsu occupies the second-biggest land area in Chiba Prefecture, much of it hilly and dotted with small settlements. Residents in the area dug out small passageways for their own convenience decades ago.

Aside from national expressways and prefectural roads, and passageways under expressways, the Kimitsu city government is responsible for 32 tunnels, about two-thirds of which were hand-dug without timber supports or other shoring devices to prevent a cave-in.

They are said to have been dug in the 1940s or earlier, and all show signs of deterioration. Spending vast amounts of money for the repair project is not regarded as a viable option, as some of the hand-dug tunnels lead only to few homes.

“It would be difficult to do major work on all of them, but we cannot simply close them,” said a city official in charge of the issue. “We will try to undertake repairs early to extend the life of the tunnels.”

The city government has decided to carry out repair work on 32 tunnels, including the 22 hand-dug ones, over five years to extend their lifespan.

Initial plans call for removing overhead rock from two tunnels so that they become passageways open to the elements, and for five to be sprayed with concrete to lessen the risk of the walls collapsing.

Three high-risk tunnels have been closed.

In fiscal 2019, a major safety check inspection is in the cards to decide on future actions.