Temperature - European Investment Bank

WEST AFRICAN POWER POOL (WAPP) PÖYRY ENERGY LTD.
Mount Coffee HPP ESIA and RAP 2012-09-18
ESIA Report Page 24
o The most impacted part of the downstream area will be the stretch of the
old riverbed between the spillway and the outlet of the tailrace channel,
which has a length of about 4 km. The impact in this part of the river will
strongly depend on the discharge pattern of the Mt. Coffee HPP. The
HPP will be operated during rainy season as a Run-of-River scheme;
during this period there will be no impacts, but during the dry season the
natural river flow will be significantly reduced, and could even be zero at
times, which would have a strong negative impact on the environment.
Therefore a residual flow taking into account the environmental,
economic and social needs has been defined.
o Another part of the downstream area is the tailrace channel itself. During
the past 20 years it was functioning as a more or less natural branch of
the river. As already mentioned above, during the rainy season discharge
will remain constant (full capacity of plant operated on a ROR basis),
while during the dry season it will be influenced by the discharge pattern.
Here, the impact compared to the original riverbed very small since all
the water used for energy production during dry season will be in the
tailrace channel. Nevertheless, the changes between full load and
reduced operation will be noticeable.
o The third part will be downstream of the confluence between tailrace
channel and original riverbed and will reach until the Atlantic Ocean
since no larger tributaries are entering into the St. Paul River within this
river stretch (salt intrusion was assessed).
� Catchment area: the catchment or watershed area of Mount Coffee HPP will not
be affected by the Project as such, but the situation in this area can greatly
influence the reservoir. The most important of these effects are eutrophication
and pollution of the reservoir water by input of nutrients (stemming mainly from
agriculture, mining activities and human settlements) and siltation of the
reservoir (due to erosion in the catchment, which again is often caused or at least
considerably exacerbated by human activities). In addition, plans for other HPPS
within the catchment were taken into account.
� River basin: for some effects, other developments in the same river basin have to
be taken into account, since they can increase or reduce environmental (or
social) effects of the project in question. However, it has to be pointed out that
this is an ESIA for a specific project and not a CIA of all the projects in the St.
Paul river basin, nor a SEA for the entire development plan of this river basin.
� Access roads: access roads can have major direct or indirect environmental
impacts. However, the project does not require the construction of any new
access roads. Work for upgrading the existing roads from Monrovia to Mount
Coffee on both sides of the St. Paul river is part of the project.
� Other areas, as might be relevant. This can comprise, e.g., transmission line
corridors, resettlement areas.