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

Hydrocarbon Content. The hydrocarbon parameters (THC and oil and grease)
in the soil samples indicated low concentrations, with oil and grease levels
falling below the detection point across both depth intervals (0.5000mg/kg).
The THC was recorded between 0.8830 – 2.920 and 0.4080 – 2.810 mg/kg in
the top and subsoil respectively.
Physico-chemical Properties. The results of the soil sampling identified the
soil to be of an acidic nature (pH 5.2000 - 5.8000) with no substantive variation
between the topsoil and subsoil. The pH was also found to fall within the
optimal pH range that supports plant growth (Ojo-Afere et al, 1990). The
analysis also identified that sandy loam is the predominant soil type with an
average composition of 60.660 and 96.260 percent during the dry and wet
seasons respectively. The sand content of the soil was observably higher
during the wet season (94.860 - 97.440 percent in the topsoil and 94.620 –
98.000 percent in the subsoil). The percentage sand composition during the
dry season was recorded at 56.840 – 65.870 mg/kg in the topsoil and at 52.410
– 68.220 mg/kg in the subsoil.
Microbial Analysis. The total heterotrophic bacteria count from the soil
samples collected at western portion ranged between 110.0 x 10 3 and 450.0 x
10 3 cfu/g, with a mean count of 251.7 x 10 3 and 231.3 x 10 3 cfu/g over the dry
and wet season respectively. The count did not illustrate significant changes
over the two depth intervals (175.0 – 362.0 and 110.0 – 450.0 mg/kg in the top
and subsoil respectively). Heterotrophic fungi were also identified in the soil
ranging between 8.000 x 10 3 and 102.0 x 10 3 cfu/g in the wet and dry season.
The heterotrophic fungi were found to be at a higher level in the topsoil (62.00
– 102.00 x 10 3 cfu/g) compared to the subsoil (8.000 – 60.00 x 10 3 cfu/g). Similar
to the Proposed Site, hydrocarbon utilizing bacteria and fungi were not
detected in the soil during both sampling periods.
Southern Portion of the Site
Sampling was also conducted on the southern portion of the site and results
are outlined below.
Heavy Metal Composition. Other heavy metals examined were recorded at
low concentrations similar to those recorded at the other locations sampled
across the site, during both seasons. Concentration levels fall within the
limits tolerated by plants and soil organisms and correspond to levels
naturally occurring in soils (Allen et al, 1974). Iron was identified as having
the highest concentration ranging between 2,320 and 36, 000 mg/kg over both
the dry and wet seasons. The iron concentrations were notably higher in the
subsoil during both wet seasons (11,500 – 36,000) compared to the topsoil
(2,320.0 – 15,280 mg/kg).
Anion and Cation Analysis. Nitrate ions were found, as with the other
locations sampled across the Project site, to have the highest concentration
among the anions analysed (3,450.0 - 61,152 mg/kg). The nitrate concentration
AZURA EDO IPP
4-11
DRAFT EIA REPORT