Legend
4.7.3 Surface Water Quality
67 Noise levels increased in the dry season due to increased human activities. The proposed project has the potential to increase noise levels due to increased vehicular, machinery and human activities during and after the construction of the project. All parameters of air quality and noise within the study area are within acceptable limits both at the study locations and control.
68 natural waters is 1 to 2000 NTU (Mills, 2013). High turbidity levels are common in Niger Delta rivers (Akpan et al., 2003). High wet season values are due to surface run-off of silt from river catchment into the surface waters. The proposed project has the potential to increase the turbidity of associated surface waters.
Mean levels of TSS ranged from 34 mg/l at MSAGIO to 78 mg/l at USAGIO compared to 26.5 mg/l at control and from 23 mg/l at MSPW to 52 mg/l at MSAGIO compared to 46 mg/l at the control during the dry season. Levels during the wet season were also significantly higher and more varied than those of the dry season which may be attributed to rain-related input of silt and other materials via surface run-off. Values of TSS ranging from 1.2 to 397 mg/l have been previously reported for the Niger Delta Rivers (RPI/NNPC, 1985). Present levels are normal for rivers of the Niger Delta. The proposed project has the potential to increase suspended solids in associated surface waters.
Mean water colour varied from 15.43 units at DSPW to 29 units at USAGIO compared to control of 22.5 units during the wet season and from 7.8 units at DSPW to 26 units at USAGIO compared to control of 18 units. Dry season values were generally lower than wet season concentrations.
The seasonal variation is related to rain-related inputs of materials including humic substances from the catchment via surface run-off. The values are normal for forested aquatic systems of southern Nigeria (Akpan, et al., 2003).
Electrical conductivity (EC), Total Dissolved Solids (TDS) and Salinity:
Conductivity, total dissolved solids and salinity are related parameters used as measured of salt concentration. Mean value of electrical conductivity ranged from 15.81 µS/cm at PW to 39.3 µS/cm at USAGIO compared to control of 38.8 µS/cm during the wet season and from 15.6 µS/cm at DSPW to 32.31 µS/cm along PRoW compared to control 38.4 µS/cm at the control during the dry season. There were no significant differences between levels in the wet and dry season but all levels were those characteristic of freshwaters and within limits of previous report for Niger Delta Rivers (10 – 42,100 µS/cm; RPI/NNPC, 1985). Natural fresh waters are reported to vary between 50 and 1500 μS/cm (ILMB, BC, 1998, Chapman, 1992).
Total Dissolved Solids ranged from a mean of 8.04 mg/l at PW to 19.7 mg/l at USAGIO compared to control of 19.4 mg/l during the wet season and from 7.3 mg/l at MSPW to 9.35 mg/l at DSAGIO compared to 19.4 mg/l at the control. Spatial variations were observed but with no clear trend. The values were generally characteristic of freshwaters.
Salinity (as Chloride) ranged from 1.56 mg/l at MSPW to 8.69 mg/l at USAGIO compared to 51.44 mg/l at the control during the wet season and from 3.07 mg/l at MSAGIO to 8.12 mg/l at PRoW compared to control of 8.63 mg/l at control. Values at study locations were generally higher during dry than wet season but the control showed the opposite trend. All values were
69 characteristic of freshwaters. RPI/NNPC (1985) reported a range of 3.0 – 18,648 mg/l for the Niger Delta..
70 Table 4.5a: Summary results of Physicochemical measurements in Surface water around Enwhe Field during the wet season
Parameters PW PRoW USPW MSPW DSPW USAGIO MSAGIO DSAGIO CTR RPI/NNPC,
1985
pH 6.7±0.84 7.15±0.4 6.75±0.35 7.5±0 6.68±0.82 6.9±0 7.5±0 6.75±0.35 6.95±0.35 3.1-8.6
Redox Potential, mV 21.17±54.77 -12.53±32.3 4.63±11.4 45.9±0 8.54±58.2 11.1±0 -46.3±0 4.63±11.4 0.65±20.01 Electrical
Conductivity, µS/cm
15.81±3.92 27.96±12.8 18.43±6.31 19.3±0 32.02±44.58 39.3±0 21±0 18.43±6.31 38.7±0 0.01-42.1 Turbidity, NTU 54.49±35.68 89.05±70.34 86.87±72.2 112.4±0 61.34±50.29 81.6±0 49.6±0 86.87±72.2 15045±8421
TSS, mg/L 41±28.68 67.3±48.44 61±48.14 89±0 41.14±28.96 78±0 34±0 61±48.14 26.5±3.54 1.2-397.0
TDS, mg/L 8.04±2.05 14.05±6.39 9.27±3.11 9.7±0 16.14±22.24 19.7±0 10.8±0 9.27±3.11 19.4±0 0.002-35.35
THC, mg/L 0.64±0.36 <0.1 <0.1 0.72±0 0.6±0.5 <0.1 <0.1 <0.1 <0.1
COD, mg/L 8.06±1.19 10.03±2.89 11.07±2.54 7.36±0 8.19±1.15 16.36±0 8.56±0 11.07±2.54 7.43±1.59 1.95-2,460.0
DO, mg/L 7.2±1.37 6.33±1.61 6.8±0.36 8.1±0 7.01±1.31 6.9±0 7.1±0 6.8±0.36 4.85±1.91 2.0-9.0
BOD5 mg/L 2.83±0.71 2.77±0.8 3.43±0.59 2.3±0 2.89±0.67 3.1±0 2.5±0 3.43±0.59 1.95±1.06
Salinity as Cl, mg/L 1.86±1.15 3.42±2.64 1.97±1.11 1.56±0 7.56±15 8.69±0 2.9±0 1.97±1.11 51.44±65.5 3.0-18,648.0
Odour ND ND ND ND ND ND ND ND ND
Nitrite, mg/L 0.04±0.03 0.04±0.02 0.03±0.01 0.05±0 0.04±0.03 0.02±0 0.02±0 0.03±0.01 0.02±0 Colour(Pt-Co) 16.86±8.73 20±6.04 16.33±4.04 28±0 15.43±7.3 29±0 21±0 16.33±4.04 22.5±3.54 Alkalinity mg/L 29.71±3.74 32±2.3 31.5±2.5 31.5±0 29.71±3.74 31.5±0 31.5±0 31.5±2.5 35.25±5.3 Oil & Grease mg/L 1.08±0.65 <0.01±0 <0.01±0 1.3±0 0.98±0.88 <0.01±0 <0.01±0 <0.01±0 <0.01±0
Nitrate mg/L 0.16±0.05 0.35±0.69 0.85±1.26 0.11±0 0.19±0.09 0.19±0 0.16±0 0.85±1.26 0.13±0.01 BDL-5.44 Phenols mg/L <0.05±0 <0.05±0 <0.05±0 <0.05±0 <0.05±0 <0.05±0 <0.05±0 <0.05±0 <0.05±0
Sulphate mg/L 2.15±0.85 2.82±1.89 1.98±0.41 3.18±0 2.53±1.64 2.35±0 2.19±0 1.98±0.41 4.69±2.36 Ammonia mg/L 1.05±0.18 1.5±0.74 1.43±0.59 1.33±0 1.08±0.24 1.07±0 1.07±0 1.43±0.59 0.79±0.11
Phosphate mg/L 0.16±0.11 0.32±0.23 0.12±0.01 0.36±0 0.16±0.12 0.24±0 0.16±0 0.12±0.01 0.11±0.01 0.049-0.584 reactive silica mg/L 1.15±0.34 1.16±0.31 0.78±0 1.47±0 1.03±0.35 1.08±0 1.42±0 0.78±0 1.24±0.3
PW=Proposed Wells; PRoW=Pipeline RoW; USPW = Upstream of Proposed Wells; MSPW =Midstream of Proposed Wells; DSPW = Downstream of Proposed Wells; USAGIO = Upstream of Agiogbologbo; MSAGIO = Midstream of Agiogbologbo; DSAGIO = Downstream of Agiogbologbo;
CTR = Control, BDL=Below Detection Limit; Source: Enwhe Field Development EIA Field Data September, 2016 (Wet season)
71 Table 4.5b: Summary results of Physicochemical measurements in Surface water around Enwhe Field during the dry season
Parameters PW PRoW USPW MSPW DSPW USAGIO MSAGIO DSAGIO CTR RPI/NNPC,
1985) pH 7.13±0.1 6.93±0.25 6.95±0.35 7.02±0 7.15±0.09 6.71±0 6.9±0 6.95±0.35 7.04±0.51 3.1-8.6 Redox Potential
mV
-30.64±1.52 -24.31±8.07 -24.3±11.03 -29.5±0 -30.86±1.39 -15.2±0 -28.1±0 -24.3±11.03 -25.95±10.68 Electrical
Conductivity µS/cm
15.7±0.71 32.31±26.72 18.65±0.35 14.6±0 18.8±6.33 15.6±0 16±0 18.65±0.35 38.4±19.66 0.01-42.1
Turbidity NTU 18.48±1.82 22.83±11.48 27±9.9 19±0 15.86±5.85 19.3±0 43±0 27±9.9 46.2±12.45
TSS mg/L 23.6±3.97 28.43±13.56 29±18.38 23±0 20.4±8.47 28±0 52±0 29±18.38 46±2.83 1.2-397.0 TDS mg/L 7.86±0.35 16.36±13.69 9.35±0.21 7.3±0 9.44±3.22 7.8±0 8±0 9.35±0.21 19.4±10.04 0.002-35.35 THC mg/L <0.1±0 <0.1±0 <0.1±0 <0.1±0 <0.1±0 <0.1±0 <0.1±0 <0.1±0 <0.1±0
COD mg/L 7.05±1.01 7.85±1.66 8.75±0.65 5.36±0 7.45±0.35 6.13±0 10.08±0 8.75±0.65 7.63±0.83 1.95-2,460.0 DO mg/L 6±0.58 5.96±0.67 5.95±0.07 5.8±0 6.2±0.66 5.5±0 6.4±0 5.95±0.07 5.9±0.57 2.0-9.0 BOD5 mg/L 2.24±0.5 2.24±0.53 2.2±0.42 2.9±0 2.18±0.41 2.9±0 2±0 2.2±0.42 2.6±0.28
Salinity as Cl mg/L 4.8±0.75 8.12±5.04 6.01±1.32 5.08±0 5.02±0.98 5.08±0 3.97±0 6.01±1.32 8.63±5.87 3.0-8,648 Nitrite mg/L 0.01±0.01 0.01±0 <0.001±0 <0.001±0 0.01±0 <0.001±0 <0.001±0 <0.001±0 <0.001±0
Colour(Pt-Co) 8.2±2.77 13.43±6.11 11.5±3.54 12±0 7.8±2.17 26±0 15±0 11.5±3.54 18±1.41 Alkalinity mg/L 42±6.16 41.43±2.99 40±2.83 46±0 40.8±5.76 40±0 42±0 40±2.83 44±0 Oil & Grease mg/L <0.01±0 <0.01±0 <0.01±0 <0.01±0 <0.01±0 <0.01±0 <0.01±0 <0.01±0 <0.01±0
Nitrate mg/L 0.02±0.01 0.01±0.01 0.004±0 0.02±0 0.02±0.01 0.004±0 0.01±0 0.004±0 0.01±0 BDL-5.44 Phenols mg/L <0.05±0 <0.05±0 <0.05±0 <0.05±0 <0.05±0 <0.05±0 <0.05±0 <0.05±0 <0.05±0
Sulphate mg/L 0.96±0.66 0.87±0.34 0.97±0.17 0.49±0 1.22±0.69 0.49±0 0.87±0 0.97±0.17 1.66±1.18 Ammonia mg/L 0.23±0.07 0.19±0.03 0.19±0.01 0.12±0 0.22±0.09 0.2±0 0.18±0 0.19±0.01 0.16±0.02
Phosphate mg/L 0.04±0.01 0.03±0.01 0.02±0 0.04±0 0.03±0.01 0.03±0 0.02±0 0.02±0 0.03±0.02 0.049-0.584 reactive silica mg/L 0.68±0.29 0.52±0.2 0.45±0.16 0.59±0 0.7±0.28 0.85±0 0.62±0 0.45±0.16 0.73±0.3
PW=Proposed Wells; PRoW=Pipeline RoW; USPW = Upstream of Proposed Wells; MSPW =Midstream of Proposed Wells; DSPW = Downstream of Proposed Wells; USAGIO = Upstream of Agiogbologbo; MSAGIO = Midstream of Agiogbologbo; DSAGIO = Downstream of Agiogbologbo; CTR = Control, BDL=Below Detection Limit; Source: Enwhe Field Development EIA Field Data November, 2016 (Dry Season)
72 Dissolved Oxygen (DO), Biochemical Oxygen Demand (BOD5) and Chemical Oxygen Demand (COD)
Dissolved oxygen ranged from a mean value of 6.33 mg/l at PRoW to 7.2 mg/l at PW compared to control of 7.43 mg/l during the wet season and from 5.5 mg/l at USAGIO to 6.4 mg/l at MSAGIO compared to 5.9 mg/l at control during the dry season. Most water quality criteria for protection of aquatic life recommends DO values of 5 mg/l (Alken Murray Corp., 2006) and above but below 110% saturation (RAMP, 2000). The amount of dissolved oxygen is considered poor if the concentration is less than 2 mg/l, a condition referred to as hypoxia (Chapman, 1992, Rabalais et al. 2002). RPI/NNPC (1985) reported DO levels between 2 and 9 mg/l for waters of southern Nigeria. The measured levels are considered normal for unpolluted environments.
Biochemical Oxygen Demand ranged from mean of 2.3 mg/l at MSPW to 3.43 mg/l at USPW and DSAGIO compared to control of 1.95 mg/l at control and from 2 mg/l at MSAGIO to 2,24 mg/l at PW and PRoW compared to control of 2.6 mg/l during the dry season. There were wide spatial and seasonal variations in BOD levels with no clear trend. Unpolluted waters typically have BOD of 2 mg/l or less, whereas water in contact with wastewater may have values up to 10 to 15 mg/l (Chapman and Kimstach, 1992). The observed BOD values are normal for unpolluted surface waters.
Chemical Oxygen Demand varied from mean value of 7.36 mg/l at MSPW to 16.36 mg/l at USAGIO compared to control of 7.43 mg/l during the wet season and from 5.36 mg/l at MSPW to 10.08 mg/l at MSAGIO compared to control of 7.63 mg/l at the control during the wet season. Wet season values were relatively higher than dry season values but all levels were low and characteristic of unpolluted waters. A range of 1.95 to 2,460 mg/l was reported by RPI/NNPC (1985) for the Niger Delta.
Nutrients-Ammonium, Nitrate and Phosphate:
Ammonium ranged from 1.05 mg/l at PW to 1.5 mg/l at PRoW compared to 0.79 mg/l at the control during the wet season and from 0.12 mg/l at MSPW to 0.23 mg/l at PW compared to control of 0.16 mg/l during the dry season. The un-ionized form of ammonia (NH3) should not exceed 0.05 mg/l in order to protect aquatic organisms (Francis-Floyd et al., 2015). Considering the ambient pH (~7) and temperatures during the study, the concentration of un-ionized ammonia would not exceed 20% of total ammonia and therefore not of any toxicological concern..
Nitrate ranged from 0.11 mg/l at MSPW to 0.85 mg/l at USPW and DSAGIO compared to control of 0,13 mg/l during the wet season and from 0.004 mg/l at USAGIO, DSAGIO and USPW to 0.02 mg/l at PW compared to control of 0.01 mg/l during the dry season. Wet season values were significantly higher than dry season levels indicating the effect of rainfall and surface run-off on concentrations which is also responsible for the higher spatial variability in the wet season. Nitrate levels were generally low and within the range of BDL to 5.44 mg/l reported previously for the
73 Niger Delta (RPI/NNPC,1985). In non-polluted waters, the world average of nitrates is 0.30 mg/l (Mills, 2013). Concentrations in excess of 20 mg/l nitrate usually indicate pollution by human or animal waste, or fertilizer runoff (Chapman and Kimstach, 1992).
Mean Phosphate levels ranged from 0.12 mg/l at DSAGIO to 0.36 mg/l at MSPW compared to control of 0.13 mg/l during the wet season and from 0.02 mg/l at DSAGIO, MSAGIO and USPW to 0.04 mg/l at PW, and MSPW compared to control of 0.03 mg/l in the dry season. Wet season values were significantly higher than dry season values indicating the impact of rainfall input and run-off from catchment. Spatial variations were higher in the wet season compared to dry season indicating the importance of local inputs from surface run-off. Most natural waters have phosphate levels ranging from 0.01 to 0.05 mg/l (Mills, 2013). RPI/NNPC (1985) gave a range of 0.049 to 0.584 mg/l for phosphate in rivers of southern Nigeria. Present values are therefore normal for the study area.
Mean Reactive silica concentration ranged from 0.78 mg/l at DSAGIO and USPW to 1.47 mg/l at MSPW compared to control of 1.24 mg/l and from 0.45 mg/l at USPW and DSAGIO to 0.85 mg/l at USAGIO compared to 0,73 mg/l at the control. Wet season values were higher than dry season values and spatial variability was also higher in the wet season showing the effect of surface run-off inputs. Silicate is mainly of importance as nutrient in the growth of diatoms which utilize it for the formation of their shell matter. Natural concentrations can range from a few parts per million (ppm) in surface water to more than 100 ppm in groundwater. For instance, the soluble silica concentration of Mississippi River-water averages 4.0-7.5 ppm (Bien, et al., 1958). The observed concentrations in the study area are low and within normal levels in unpolluted waters.
Alkalinity
Alkalinity represents the sum of components (mainly bicarbonate, carbonate, and hydroxide) in the water which buffers it against changes in pH. Alkalinity ranged from a mean of 29.71 mg/l at PW and DSPW to 32 mg/l at PRoW compared to 35.25 mg/l at control during the wet season and from 40 mg/l at USAGIO to 46 mg/l at MSPW compared to 44 mg/l at the control during the dry season. Spatial variation was not significant but dry season values were significantly higher than wet season values indicating the impact of rain dilution of carbonates and bicarbonates. The alkalinity values are normal for freshwaters. To offset acids produced by nitrifying bacteria, alkalinity above 75 mg/L is recommended. The acceptable range for most finfish is 20-200 mg/1 (ppm).
Sulphate
Sulphate ranged from a mean of 1.98 mg/l at USPW and DSAGIO to 3.18 mg/l at MSPW compared to 4.69 mg/l at the control during the wet season and from 0.49 mg/l at MSPW and USAGIO to 1.22 mg/l at DSPW compared to 1.66 mg/l at control during the dry season.
Concentrations were significantly higher during the wet season indicating the input of sulphates
74 from biogenic sources via surface run-off into the waters. Observed sulphate levels are low and characteristic of freshwater environments.
Total Hydrocarbons (THC) and Oil & Grease (O&G)
Levels of THC and O&G were generally below the limits of detection particularly during the dry season. Locations with measureable concentrations during the wet season were PW, MSPW and DSPW. Average THC ranged from 0.6 mg/l at DSPW to 0.72 mg/l at MSPW compared to undetectable levels in the control. Similarly, O&G ranged from a mean of 0.98 mg/l at DSPW to 1.3 mg/l at MSPW compared to undetectable levels at the control. The surface waters were therefore not contaminated with petroleum; the minor levels being associated with inputs from run-off during the wet season.
Cations and Heavy metals
The summary of results of metals measurements in surface water are presented in Tables 4.5c and 4.5d for the wet and dry seasons respectively. Detailed results are presented in Appendix 4.6.3c &
d.
Sodium, Potassium, Calcium and Magnesium:
Mean concentration of sodium ranged from 1.12 mg/l at USPW and DSAGIO to 4.68 mg/l at USAGIO compared to control of 5.47 mg/l at control during the wet season and from 1.22 mg/l at MSAGIO to 1.6 mg/l at USPW and DSAGIO compared to control of 1.72 mg/l at the control during dry season. Levels were significantly higher during the wet than dry season. Similarly, spatial variations were higher during the wet season. Sodium levels were generally low and characteristic of freshwater environments. The proposed project has the potential to increase the sodium levels of associated surface waters through waste and effluent discharges and interference with drainage patterns.
Potassium ranged from a mean of 0.6 mg/l at MSAGIO to 2.9 mg/l at USAGIO compared to control of 2.32 mg/l at control during the wet season and from 0.2 mg/l at USAGIO to 1.0 mg/l at MSPW compared to control of 0.54 mg/l at control during the dry season. Potassium levels were relatively higher during the wet season than dry season but no significant spatial differences in relation to the control. The proposed project has the potential to increase the potassium levels of associated surface waters through waste and effluent discharges and interference with drainage patterns.
Calcium ranged from a mean of 0.32 mg/l at MSAGIO to 0.70 mg/l at MSPW compared to control of 0.33 mg/l at the control during the wet season and from 0.23 mg/l at USAGIO to 0.34 mg/l at USPW and DSAGIO compared to control of 0.23 mg/l during the dry season. Rainy season values were higher than those of the dry season but variation between stations and control was not significant.
75 Magnesium ranged from a mean of 0.24 mg/l at MSAGIO to 0.52 mg/l at MSPW compared to control of 0.26 mg/l at the control during wet season and from 0.12 mg/l at USPW and DSAGIO compared to control of 0.2 mg/l at the control during dry season. Values were significantly higher during the wet season than dry season but variation with control was not significant.
Higher levels of cations during the wet season compared to dry season is due to run-off of terrestrial materials into the surface waters during rains. All cation levels were low and characteristic of freshwater environments.
Heavy metals
Apart from Zinc, Iron and Manganese, all other heavy metals were below analytical detection limits in the study area. Iron ranged from a mean value of 0.52 mg/l at MSPW to 2.31 mg/l at USAGIO compared to control of 0.53 mg/l during the wet season and from 0.67 mg/l at USAGIO to 0.93 mg/l at MSPW compared to 0.86 mg/l at the control during the dry season. Wet season values were significantly higher than dry season values. During the wet season, levels at control were lower than those of the study location but there was no spatial difference during the dry season. The observed levels are within the BDL to 4.75 mg/l reported by RPI/NNPC (1985).
Manganese ranged from a mean of 0.08 mg/l at PW and MSAGIO to 0.11 mg/l at USPW and DSAGIO compared to 0.06 mg/l at the control and from 0.04 mg/l to 0.06 mg/l at MSPW compared to control of 0.04 mg/l. Wet season values were higher than the dry season concentrations but spatial variation were not significant.
Zinc varied from a mean concentration of 0.11 mg/l at USAGIO to 0.63 mg/l at DSPW compared to control of 0.27 mg/l and from 0.29 mg/l to 0.32 mg/l compared to control of 0.29 mg/l during the dry season. Wet season values were higher than the dry season values but spatial variations were not significant. Zinc levels were within the range reported by RPI/NNPC (1985) of BDL -0.770 mg/l for the Niger Delta. In general, while the levels of cations and heavy metals are low and within background values, there is a strong tendency for inputs from catchment during rains.
76 Table 4.5c: Summary results of metals measurements in Surface water around Enwhe Field during the wet season
Parameters PW PRoW USPW MSPW DSPW USAGIO MSAGIO DSAGIO CTR RPI/NNPC, 1985 Na mg/L 1.69±0.68 3.56±2.54 1.12±0.03 2.01±0 4.6±7.87 4.68±0 3.07±0 1.12±0.03 5.47±0.3
K mg/L 0.84±0.16 1.03±0.7 0.91±0.04 0.93±0 1.55±1.93 2.9±0 0.6±0 0.91±0.04 2.32±0.73 Ca mg/L 0.39±0.2 0.47±0.19 0.44±0.18 0.7±0 0.37±0.17 0.42±0 0.32±0 0.44±0.18 0.33±0.03 Mg mg/L 0.31±0.12 0.32±0.1 0.33±0.08 0.52±0 0.28±0.07 0.28±0 0.24±0 0.33±0.08 0.26±0.04 Mn mg/L 0.08±0.04 0.09±0.03 0.11±0.03 0.05±0 0.1±0.05 0.11±0 0.08±0 0.11±0.03 0.06±0.01
Fe mg/L 1.1±1.02 1.52±0.83 1.48±0.9 0.52±0 2.06±2.49 2.31±0 1.28±0 1.48±0.9 0.53±0.14 BDL - 4.75 Cd mg/L <0.001±0 0.01±0 <0.001±0 <0.001±0 <0.001±0 <0.001±0 <0.001±0 <0.001±0 <0.001±0 BDL - 0.092 Cr mg/L <0.005±0 0±0 <0.005±0 <0.005±0 <0.005±0 <0.005±0 <0.005±0 <0.005±0 <0.005±0 BDL - 0.971 Ni mg/L <0.005±0 0±0 <0.005±0 <0.005±0 <0.005±0 <0.005±0 <0.005±0 <0.005±0 <0.005±0 BDL-1.379 V mg/L <0.005±0 0±0 <0.005±0 <0.005±0 <0.005±0 <0.005±0 <0.005±0 <0.005±0 <0.005±0 BDL -1.563 Pb mg/L 0.04±0.02 0.02±0.01 0.01±0.01 0.01±0 0.04±0.02 0.02±0 0.01±0 0.01±0.01 0.03±0.01 BDL –
1.354 Zn mg/L 0.35±0.15 0.42±0.24 0.36±0.17 0.29±0 0.63±0.72 0.11±0 0.51±0 0.36±0.17 0.27±0.05 BDL -0.770 Hg mg/L <0.02±0 <0.02±0 <0.02±0 <0.02±0 <0.02±0 <0.02±0 <0.02±0 <0.02±0 <0.02±0
PW=Proposed Wells; PRoW=Pipeline RoW; USPW = Upstream of Proposed Wells; MSPW =Midstream of Proposed Wells; DSPW = Downstream of Proposed Wells; USAGIO = Upstream of Agiogbologbo; MSAGIO = Midstream of Agiogbologbo; DSAGIO = Downstream of Agiogbologbo; CTR = Control
Source: Enwhe Field Development EIA Field Data September, 2016 (Wet season)
77 Table 4.5d: Summary results of metals measurements in Surface water around Enwhe Field during the dry season
Parameters PW PRoW USPW MSPW DSPW USAGIO MSAGIO DSAGIO CTR RPI/NNPC, 1985 Na mg/L 1.46±0.17 1.31±0.23 1.6±0.21 1.34±0 1.52±0.17 1.27±0 1.22±0 1.6±0.21 1.72±0.01
K mg/L 0.62±0.42 0.61±0.33 0.64±0.33 1±0 0.47±0.39 0.2±0 0.95±0 0.64±0.33 0.54±0.48 Ca mg/L 0.33±0.04 0.31±0.05 0.34±0.04 0.32±0 0.33±0.04 0.23±0 0.27±0 0.34±0.04 0.23±0.01 Mg mg/L 0.15±0.05 0.15±0.04 0.12±0 0.13±0 0.14±0.05 0.14±0 0.13±0 0.12±0 0.2±0.13 Mn mg/L 0.05±0.03 0.04±0.02 0.04±0.01 0.06±0 0.05±0.03 0.04±0 0.08±0 0.04±0.01 0.04±0.01
Fe mg/L 0.77±0.21 0.78±0.16 0.8±0.18 0.93±0 0.69±0.21 0.67±0 0.8±0 0.8±0.18 0.86±0.09 BDL - 4.75 Cd mg/L 0.01±0 <0.001±0 <0.001±0 <0.001±0 <0.001±0 <0.001±0 <0.001±0 <0.001±0 <0.001±0 BDL - 0.092 Cr mg/L <0.005±0 <0.005±0 <0.005±0 <0.005±0 <0.005±0 <0.005±0 <0.005±0 <0.005±0 <0.005±0 BDL - 0.971 Ni mg/L <0.005±0 <0.005±0 <0.005±0 <0.005±0 <0.005±0 <0.005±0 <0.005±0 <0.005±0 <0.005±0 BDL-1.379 V mg/L <0.005±0 <0.005±0 <0.005±0 <0.005±0 <0.005±0 <0.005±0 <0.005±0 <0.005±0 <0.005±0 BDL -1.563 Pb mg/L 0.03±0.01 0.02±0.01 0.01±0 0.04±0 0.03±0.02 0.03±0 0.03±0 0.01±0 0.04±0 BDL – 1.354 Zn mg/L 0.32±0.03 0.29±0.01 0.29±0 0.31±0 0.32±0.03 0.3±0 0.31±0 0.29±0 0.29±0 BDL -0.770 Hg mg/L <0.02±0 <0.02±0 <0.02±0 <0.02±0 <0.02±0 <0.02±0 <0.02±0 <0.02±0 <0.02±0
PW=Proposed Wells; PRoW=Pipeline RoW; USPW = Upstream of Proposed Wells; MSPW =Midstream of Proposed Wells; DSPW = Downstream of Proposed Wells; USAGIO = Upstream of Agiogbologbo; MSAGIO = Midstream of Agiogbologbo; DSAGIO = Downstream of Agiogbologbo; CTR = Control
Source: Enwhe Field Development EIA Field Data November, 2016 (Dry season)
78 Microbiology
The summary of results of Microbiological measurements in surface water are presented in Tables 4.5e and 4.5f for the wet and dry seasons respectively. Detailed results are presented in Appendix 4.6.3e and f.
Coliform Bacteria:
Total coliforms ranged from a mean of 4 MPN/100ml at MSAGIO to 10 MPN/100 ml at MSAGIO compared to control of 10 MPN/100 ml at the control during the wet season and from 2 MPN/100 ml at MSAGIO and MSPW to 6.6 MPN/100 ml at DSPW compared to control of 4 MPN/100 ml during the dry season. Values were significantly higher during the wet season showing the impact of surface run-off inputs. Most drinking water quality standards recommend that drinking water should be devoid of all Coliform bacteria. Although coliform bacteria are not harmful in most cases, their presence in water supply it is an indicator of the potential occurrence of other harmful and disease causing bacteria and such waters are considered as being presenting a potential health hazard and classified as unsafe for human consumption.
Total Heterotrophic Bacteria (THB):
THB ranged from mean value of 0.5 x 103 cfu/ml at MSAGIO to 0.91 x 103 cfu/ml at MSPW compared to 0.54 x 103 cfu/ml at the control during the wet season and from 0.29 x 103 cfu/ml at MSAGIO to 0.39 x 103 cfu/ml at DSPW compared to control of 0.23 x 103 cfu/ml at the control during the dry season. Values were significantly higher during the wet season compared to the dry season but there was no significant difference compared to control.
Hydrocarbon Utilizing Bacteria (HUB):
HUB ranged from a mean of 0.2 x 102 cfu/ml at MSAGIO to 0.44 x 102 cfu/ml at PRoW compared to control of 0.22 x 102 cfu/ml during the wet season and from 0.1 x 102 cfu/ml at MSPW to 0.31 x 102 cfu/ml at MSAGIO compared with control of 0.13 x 102 cfu/ml during the dry season. Values were significantly higher during the wet season than dry season but spatial variation compared to control was not significant. The percentage of HUB to THB is usually used as indication of petroleum hydrocarbon pollution. Levels below 10% is regarded as indicator of unpolluted environment (Atlas, 1982). The levels of HUB are generally very low (10 orders of magnitude lower) relative to THB signifying no oil pollution in the environment.
Total Heterotrophic Fungi (THF) and Hydrocarbon Utilizing Fungi (HUF)
Mean levels of THF and HUF were generally low and non-detectable in several samples particularly around the pipeline crossings near Agiogbologbo.
79 Table 4.5e: Summary results of microbiological measurements in Surface water around Enwhe Field during the wet season
Paramete
rs Units PW PRoW USPW MSPW DSPW USAGI
O
MSAGI O
DSAGI
O CTR
Coliform Count
MPN/100
ml 6.86±3.39 9±3.71 8.67±3.7
9 7±0 7.43±3.74 10±0 4±0 8.67±3.7
9 10±1.41
HUB cfu/ml X
102 0.35±0.16 0.44±0.2 0.31±0.0
6 0.34±0 0.33±0.17 0.36±0 0.2±0 0.31±0.0
6 0.22±0.16
HUF cfu/ml X
102 0.05±0.02 0.04±0.01 0±0 0±0 0.07±0.05 0±0 0±0 0±0 0±0
THB cfu/ml X
103 0.59±0.24 0.69±0.21 0.85±0.1
1 0.91±0 0.5±0.22 0.51±0 0.5±0 0.85±0.1
1 0.54±0.08
THF cfu/ml X
102 0.07±0.02 0.12±0.1 0.04±0 0.05±0 0.06±0.03 0±0 0.03±0 0.04±0 0.05±0 PW=Proposed Wells; PRoW=Pipeline RoW; USPW = Upstream of Proposed Wells; MSPW =Midstream of Proposed Wells; DSPW
= Downstream of Proposed Wells; USAGIO = Upstream of Agiogbologbo; MSAGIO = Midstream of Agiogbologbo; DSAGIO = Downstream of Agiogbologbo; CTR = Control
Source: Enwhe Field Development EIA Field Data September, 2016 (Wet season)