CONTRACTING Tunnels 14TH ST. -GREENLINE-METRO TUNNEL WASHINGTON, DC (1994) PARK ROAD -GREENLINE- METRO TUNNEL WASHINGTON, DC (1995) Under major cities, tunneling through soft soils requires extreme caution, monitoring and expertise. In building over one mile of twin tunnels for the Washington, D.C. subway system, the joint venture formed between KiSKA-USA and Kajima Construction utilized dewatering, chemical grouting, underpinning and slurry wall construction to stabilize soils and buildings adjacent to the excavation. Open shield hydraulic excavator and precast segment liners were used for tunnel excavation.