Gomal Zam Dam: Ministry objects to Wapda’s revised PC-1

December 06, 2012

MUSHTAQ GHUMMAN

Gomal Zam Dam

The Ministry of Water and Power has reportedly raised objections over the revised PC-1 of Gomal Zam Dam multipurpose project prepared by the Water and Power Development Authority (Wapda). The 17.4 MW multipurpose project will be constructed at Kahjuri Kach on Gomal River South Waziristan and was initially approved by the Executive Committee of National Economic Council (Ecnec) in 2001 at the cost of Rs 12.829 billion which has increased by 71.5 percent to Rs 22 billion.

The ministry in its comments has said that revised PC-1 should be prepared based on latest hydro meteorological data. Old data series (1957-1980) has been used in calculation of mean monthly runoffs. For the period 1996-2011 data set may be generated by extrapolation and from 2002 onwards till-date measured date should be used.

Official sources told BR that the Ministry maintains that old water quality analysis results as contained in the original PC -1 have been attached with the revised PC-1 and Wapda has been requested to provide revised/updated analysis results in the PC-1. The Ministry has recommended F-13 at the U/S edge of the site, dental treatment with concrete and contact grouting, and permanent solution to the problem to be included in the PC-1 to prevent serious threat of concentrated leakage.

Two different escalation rates (6 per cent and 6.5 per cent) have been given for inflation on local and foreign component. Ministry has suggested its correction. A meeting held on June 21, 2011 at dam site between experts from China and Lahmeyer International for the possible solution of controlling of seepage agreed to extend curtain grouting upto impervious shale boundaries which was not implemented by M/s Sinohydro Corporation.

Initial reservoir impounding has started since March 29, 2011 and until now about 78± meters depth of water in the reservoir against 133 meters has been achieved. On either sides of the Gomal River the permeable limestone have complex striking/dipping sub-parallel to dam axis. The limestone rock at dam site medium to thin bedded, fractured, sheared, fishered and 14 Nos. faults crossed both abutments of the dam.

The seepage problem of both abutments of dam can be solved by curtain grouting. Because on either sides of the Gomal River the permeable limestone complex striking/dipping, sub-parallel to the dam axis is confined by impervious shale cropping out some 200M upstream of the dam at left abutment. At the right abutment there is continuation of the shales upstream of the dam. The exact distance between the dam axis and the impervious shale at right bank is not known.

Courtesy: BR

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