Besides the geology-related problems usual in underground excavation, numerous other problems like rockslides & unprecedented floods were encountered during project construction, some of which are described below. A massive rock slide of about 1.0 million cum., occurred on 8th July, 1993 on the right bank about 120 m upstream of dam axis which completely covered the proposed location of the inlet portal of the diversion tunnel and necessitated modification in the diversion arrangement. It was seen that removal of debris to approach and construct the inlet portal at its original location and level without effecting construction schedule was not possible. Therefore, studies were carried out to shift the inlet portal upstream of the original location.The length of diversion tunnel had to be increased from 410 m to 738 m.
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