The strength of these rocks range from extremely weak to extremely strong and their conditions range from highly weathered and fractured, to fresh, massive and intact. The weathered rock beds are further overlain by transported soil, calcareous sandstone and thin bed of coarse grained conglomerate. The top of these strata are overlain by marine soil layer up to 9m thick consisting of dark brown clayey silt with some fine sand overlying weathered, dark brown basaltic boulders embedded in the silt. The major engineering problems that needed suitable solutions before proceeding with the work were as follows: