annexc - Newmont Mining Corporation

Annex C4 – Water Resources Supplemental Information C4 - 8
SW-28: Mamang River at Mamanso (drainage area = 98 km 2 )
� April-June 2004 flow measurements = 0.009 – 0.56 m 3 /sec
� Minimum flow in May 2007 was zero m 3 /sec
� Peak flow in September 2007 = 12.2 m 3 /sec, with flow receding to 0.05 m 3 /sec by
early December
� Calculated bankfull discharge = 12 m 3 /sec
SW-24: Mamang River at Nkwanten (drainage area = 384 km 2 )
� April-June 2004 flow measurements = 0.021 – 9.86 m 3 /sec
� Minimum flow in May-early June was zero m 3 /sec
� Peak flow in September 2007 = 68 m 3 /sec, with flow receding to 0.5 m 3 /sec by early
December
� Calculated bankfull discharge = 32 m 3 /sec
Tributary Streams
Principal tributary streams in the Study Area include the Afosu, Adentosu, Akwasi, and
Adenkyerensu, all of which are ephemeral. Instantaneous flow measurements for tributary
streams by Clear Creek Consultants (2008b) in July and October 2007 ranged from 0 to 0.5
m 3 /sec. Calculated mean monthly flows for the Adenkyerensu and Afosu streams are
presented in Table C4-3.
SURFACE WATER QUALITY
Laboratory analysis for metals in surface water samples was conducted at the SGS
Laboratory in Amsterdam, Netherlands, while all other physio-chemical constituents were
analyzed at the SGS Laboratory in Accra, Ghana. All laboratory analyses were performed in
accordance with “Standard Methods for the Examination of Water and Wastewater” of the
American Public Health Association (1995).
Water quality standards or guidelines for the parameters analyzed are presented in Table
C4-4. These standards are associated with drinking water from the Ghana Standards
Board/Ghana Water Company (GSB/GWC), United States Environmental Protection
Agency (USEPA), and World Health Organisation (WHO). The drinking water standard
with the lowest concentration for each parameter, if available, was used for comparison of
analytical results in the attached statistical summaries.
Statistical summaries of chemical analyses of surface water samples collected from the 28
monitoring stations between 2001 and 2007 (SGS 2004g; Clear Creek Consultants 2008b)
are presented in Table C4-5. These data are compared to the water quality standards and
guidelines shown in Table C4-4. The statistical summaries of all surface water quality data
are grouped into the following categories: Pra River, Pra River tributaries, Mamang River,
Mamang River tributaries, and Afosu stream.
Akyem Gold Mining Project November 2008 FINAL EIS