Azura-Edo Independent Power Plant Environmental Impact ... - IFC

Osemwende was measured at 27.2 mg/l (wet season), and was comparably
higher than the TDS at both Ihovbor-Evboeka borehole. However, all values
falls within the FMEnv limit of 500 mg/l, and the WHO drinking water
guideline of 600 – 1,000mg/l (WHO, 2011). The TSS from the groundwater
sample also fell within the 10.0 mg/l limit set by FMEnv (refer to Annex B), with
values recorded at 9.0 mg/l at the Ihovbor-Evboeka borehole (Borehole 1, dry
season) and 1.0 mg/l (Borehole 2, wet season). TSS was measured as 3.0 mg/l
at Orior-Osemwende borehole during the wet season.
• Nutrients. The nutrient load of the groundwater is identified in Table 4.2. The
nitrate levels for the Ihovbor-Evboeka borehole was 19.0 mg/l (Borehole 1, dry
season), which is above the FMEnv limit of 10.0 mg/l but which fell within the
WHO guideline of 50.0 mg/l (WHO, 2011). According to WHO, in most
countries, “nitrate levels in drinking water originating from surface water do not
exceed 10.0 mg/l, however water derived from wells often is above 50 mg/l” (WHO,
2011: p 398). The high presence of nitrate in the groundwater sample maybe a
result of leaching from natural vegetation and agricultural activity including
excess application of inorganic nitrogenous fertiliser. The nitrate concentration
at Ihovbor-Evboeka however also decreased significantly during the wet season
(Borehole 2) and was measured as 1.30 mg/l, well within both FMEnv and
WHO limits. The nitrate level at the Orior-Osemwende community
demonstrated similarly low levels (4.00 mg/l). The phosphate and sulphate
concentrations are within the indicated FMEnv levels (Table 4.2) and sulphate
levels were recorded within the WHO and EU standards of 500 and 250 mg/l
respectively (Lenntech, 2011).
• Cations. The concentration levels of sodium, calcium and magnesium were
within the FMEnv standards and WHO standard for sodium (less than 200
mg/l) (WHO, 2011).
• Heavy Metals. The heavy metals (copper, zinc, iron and nickel) that were
detected are provided in Table 4.2, and apart from nickel (sampled during the
dry season - Borehole 1 - at the Ihovbor-Evboeka borehole) all were recorded
below FMEnv levels (Annex B). Nickel concentrations were recorded at 0.060
mg/l or 0.010 mg/l above the FMEnv limit (0.050 mg/l) but within the WHO
drinking water standards of 0.070 mg/l (WHO, 2011).
• Total Hydrocarbon Content. The hydrocarbon parameters of oil and grease
and THC for both boreholes during both wet and dry seasons, fell below the
detection limit of 0.05 mg/l.
• Microbiology. Of the heterotrophic organisms analysed, only heterotrophic
bacteria were detected at the boreholes. Heterotrophic bacteria levels at
Ihovbor-Evboeka were noticeably lower during the dry season (Borehole 1) (1.0
x10 3 cfu/100ml) compared wet season (Borehole 2) results of 10 x 10 3
cfu/100ml. The heterotrophic bacteria levels were recorded as 5.0 x10 3
AZURA EDO IPP
4-19
DRAFT EIA REPORT