Temperature - European Investment Bank

WEST AFRICAN POWER POOL (WAPP) PÖYRY ENERGY LTD.
Mount Coffee HPP ESIA and RAP 2012-09-18
ESIA Report Page 51
The samples indicate water with a very low mineralisation (low content in overall
dissolved solids, low conductivity) and of a generally good quality, in most parameters
reaching drinking water standards. The only parameter which is constantly above the
limits is coliform bacteria, both in terms of total and faecal coliform, indicating
contamination of the water with human waste.
8.4.2 Project Impacts
During the construction phase for rehabilitating Mt. Coffee HPP there is a risk of water
contamination mainly from the following sources:
� Increased load in suspended solids stemming from the construction site.
� Contamination with concrete, resulting in a higher pH which could potentially
be toxic for fish.
� Contamination with hydrocarbons (fuel, lubricants etc.) and other toxic
substances used on site.
� Contamination with human waste from the worker's camp.
During operation, there could be a small risk of an increased load in organic matter
shortly after reservoir impoundment (see Section on GHG below). Otherwise, there is
no risk of water contamination from the power plant, as long as it is well maintained
and operated according to standards (e.g. transformer oil).
8.4.3 Other Sources of Contamination
Upstream of Mt. Coffee reservoir there are no major industrial activities which could
lead to water contamination. One additional potential source of contaminants, mainly
heavy metals, were the Bong Mines; however, these are no longer in operation. If
operation should resume there, measures would have to be taken for preventing water
contamination.
Presently, in the project area there is one potential source which could lead to water
contamination: small scale artisanal gold mining (see Section 14.2.3). The miners use
mercury for extracting the gold, and this is known to be a serious water contaminant.
Available water quality analyses (see Table 8-6) so far have not detected any water
contamination with mercury which would be above the WHO limit value for drinking
water. Nevertheless, the risk does exist, and could be acute if this type of activity should
be intensified. A check for mercury will have to be included in water quality monitoring
programs.
8.4.4 Conclusions and Recommendations
During the construction phase, the required measures will have to be taken to prevent
water contamination (like sedimentation basins for water with a high load of suspended
solids and/or contaminated with concrete; appropriate storage of fuel, lubricants and
chemicals; good maintenance of vehicles and machines to prevent losses of oil;
maintenance and repair of vehicles and machines in suitable sites (equipped with oil
skimmers), no such activities in or close to the river; waste water collection and
treatment. The measures are listed in the provisional ESMP (see Chapter 20 and 21).