Overburden 15m & within 260m of pipe jacking length, about 200m is the construction of the Ibo River tributary (Hayashita River) river crossing. The gravel rate was as high as 50%, & it was a construction to excavate a layer mainly composed of boulders. The water permeability was high, & troubles caused by lost circulation to occur, making it a very difficult site for the slurry type pipe jacking method.