The potential environmental impacts from construction activities for the project include: fugitive dust; noise; water consumption; hazardous materials and waste handling, storage and transport; sewage and domestic garbage treatment & disposal; surface runoff and sediment load management; and vehicle traffic. The EPC contractor and subcontractors are expected to control these to acceptable levels through application of standard construction environmental management practices. The relevant recommendations and mitigation measures called for in the ESMP will be incorporated into the construction contract documents as previously noted.
Water
Water will be supplied from three new boreholes to be drilled on the site in the productive aquifer. The total water consumption of the plant is expected to be approximately 22 m³/hour during the operation phase, excluding cooling water that will be pumped from the Ebrie Lagoon. Based on desktop information on the hydrogeology of the site, the risks of impacts of the groundwater pumping on water resources for the surrounding water users and risk of saline intrusion has been evaluated to be minor in the ESIA. To confirm this assessment, the project will reinforce the impact assessment based on the results of the hydrogeological tests undertaken on site and on additional groundwater user baseline/census in the project surroundings. This will include the results of pumping test to estimate the hydraulic properties of the aquifer and to model drawdown and salt water intrusion according to internationally accepted methods as well as a detailed survey or other water uses and users within the hydrogeological area of influence (ESAP #12).
A unit for the treatment of incoming waters will be installed on the power plant site to provide the various systems with the different qualities of water required. The key effluents from the project will come from the surface water runoff, sanitary water, water from the demineralized water production unit and the water from the water treatment unit that will collect the industrial effluent and drainage water from the plant. Dedicated wastewater treatment, equipment and drainage will be constructed as part of the project to manage any contaminated wastewater during the operational phase. The water treatment unit will include an oily water storage tank, a sand trap and an oily water separator. Sanitary water will be treated on site in a septic tank and soak away pit. Except for the sanitary wastewater, other effluents will be discharge into the Ebrié Lagoon along the cooling water (see below).
Cooling water – The project will use a closed-circuit water-cooling system (forced-draft) with cooling towers, which extracts waste heat to the atmosphere through the cooling of a water stream to a lower temperature. A water intake and discharge pipeline will be installed on a distance of approximately 1.2 km, between the project site and the lagoon, passing through agricultural lands, to the East of the village of Taboth and to the West of the forest area. Some of the water of the circuit must be added to replace the portion of the flow that evaporates. This make-up amount must equal the total of the evaporation, blow-down, drift, and other water losses such as wind blowout and leakage, to maintain a steady water level in the system. The cooling water will be pumped from the Ebrié lagoon (estimated volumes of 2.168 m³/h at worst case, during summer). Some of the water of the circuit will be discharged back into the lagoon to limit the concentration of dissolved minerals (like salt) and other solids in the recirculating water due to evaporation. The estimated volumes of water discharged into the lagoon are 1.676 m³/h (worst case) including contributions from the industrial effluent and drainage water from the plant described above. The project will be designed so that combined discharge of the thermal and brine effluent from blow-down water and industrial effluents meet water effluent guidelines from the World Bank Group (WBG) EHS Guidelines for Thermal Power Plants (2007), Table 5 and WBG General EHS Guidelines (2007) for thermal effluent discharge to surface waters. (ESAP #13).
To assess the potential risk of the water discharge in the lagoon, the project undertook a water quality mixing modelling study (using TELEMAC-3D V7.2 software) that was performed by an internationally recognized consulting firm (Tractebel Engineering). The model considered various assumptions on the receiving water body (climate, currents, temperature, water quality, salinity), including various recent scientific studies available for the Ebrié Lagoon and the water quality baseline samples that were collected at the location of the future discharge point as part of the ESIA in June 2018. US-EPA standards were used to determine the radius of the mixing zones (100 m) considering water use, potential receptors and assimilative capacity of the water body. Since there are no clear guidelines on the tolerance limits for salinity (highly dependent on the type of local environment), salinity limits based on the State Water Resources Control Board in California were applied. The lagoon currents speed and waves characteristics were evaluated using Jonswap formulas and Ekman assumptions. The results showed that for modelled scenarios the maximal increase in background temperature was below the applicable WBG General EHS Guidelines of 3 degrees (maximum 1.7 degree difference at a distance of 100 m). The maximal increase in salinity was 1.8 ppt at a distance of 100 m in the worst-case scenario, which is very limited considering seasonal salinity fluctuations of about 20 ppt. Therefore, significant impacts on the environment are not expected under these circumstances. Other elements that will be present in the discharged cooling water are chlorine and PO4. The concentrations of these element will however be limited in the water and controlled prior to discharge into the lagoon to guarantee compliance of the measured concentrations with the national legislation and WBG EHS guidelines, such as presented in the ESIA. The technical study states that, although the elevation of the salinity and temperature is limited and restricted to the immediate surrounding of the outfall pipe, mitigation measures should be installed were possible, such as using outfall solutions favoring rapid dilution and a location that rules out recirculation and concentrated discharge along the shoreline due to wind effects. Potential impacts of the water discharge into the lagoon to ecosystem services, including those associated with fishing communities, are discussed in the section related to Performance Standard 5 below.
As presented in the ESMP, a specific water management plan will be developed by Atinkou to summarize the various elements and monitoring requirements that will be associated with the management of the different water streams presented in this section.
GHG Emissions
The selected technology for the plant, using a combined cycle system that recuperates the heat produced by the gas combustion to produce additional energy, will reduce gas consumption by 31% compared to an open cycle technology. The overall approximate efficiency rating is expected to be about 58% net of the fuel’s Lower Heating Value (LHV). The project’s greenhouse gas emissions will primarily be carbon dioxide emitted by the plant due to combustion of natural gas. Total GHG emissions are estimated around 1,031,203 tonnes of carbon dioxide equivalent (CO2e) annually on open-cycle mode (gas-fired OCGT) and 1,096,208 tonnes of CO2e annually during combined-cycle operations. Note that the combined cycle process represent a save of around 500 000 tonnes CO2 per year with regard to the equivalent power in combined cycle.
Air Emissions and Ambient Air Quality
During the construction phase the pollutants of interest will be dust and particulate matter, evaluated as PM10, PM2.5 and Total Suspended Particulates (TSP), nitrogen dioxide (NO2), oxides of nitrogen (NOx), and sulphur dioxide (SO2) arising from construction traffic. Sources of dust and particulate matter include earthworks, access road construction and traffic along the existing road that connects the site to the main access road.
During the operational phase, the main pollutant of interest will be NO2 as the project will run on natural gas. According to project design specifications, NOx emissions from the gas turbine will not exceed 25 ppm dry volume during natural gas combustion. These limits are consistent with the 2008 World Bank Group Environmental, Health and Safety (EHS) Guidelines for Thermal Power Plants.
Considering that the project is located in a rural area with no major sources of atmospheric emissions (e.g. industries are absent, and the closest urban area is Jacqueville, located about 10 km to the east), the local airshed was assumed to be undegraded for the purpose of the present impact assessment. To confirm this assumption, baseline air quality measurements are being conducted as part of the supplemental ESIA, using diffusion tubes, for nitrogen dioxide (NO2) and nitrogen oxides (NOx) at different selected baseline air sampling locations - determined through consideration of the prevailing wind direction (almost exclusively from the southwest) and the location of sensitive receptors, in order to gain a representative sampling of the ambient air quality in the airshed.
As part of the ESIA, potential incremental impacts from operating activities were evaluated through the use of a predictive atmospheric dispersion model under open and combine cycle operating modes. The modelling took into account the plant design and local meteorology. Based on predictive modelling results, the maximum project contribution to NOx levels will be below the applicable ambient air quality standards, contributing only about 3.89 % (open cycle mode, limited to the first months of operation) and 15.41 % (combined cycle mode, used thereafter) of the NO2 1-hour maximum WHO Ambient Air Quality Standard (200 µg/m3) and 1.77% (combined cycle) of the NO2 annual average WHO Ambient Air Quality Standard. These results are compliant with the WBG General EHS Guidelines recommendation that no single project contribute more than 25% of the air quality headroom to allow for future project development. The CIPREL 5 plant design includes a continuous emissions monitoring system (CEMS) to automatically monitor NO2 emissions at the stacks on an on-going basis.
Noise
The ESIA addresses the potential for noise impacts affecting off-site receptors during the construction and operational stages of the project. Baseline ambient noise level were measured at the closest sensitive receptors that include the closest houses at the South-Eastern part of the village of Thabot (1 km away from the site) and three isolated houses/farm located closer to the future project site (including a ‘temporary’ house, approximately 300 m from the site). Noise emissions from the project will add to sources of noise from other existing noise sources in this rural environment. Background noise levels at the closest receptors around the project were evaluated to be below 45dB(A) at night for the closest receptors (except for the centre of the village of Thabot where the noise level reached 47 dBA due to human activities) and below 50dB(A) during the daytime for all receptors (isolated houses to the west of the site and houses locates at the limit of the village of Taboth, to the North-West from the site.
Potential impacts from incremental noise during operation included an evaluation with a noise propagation model (SoundPLAN v.7.3) which generates noise contours based on assumed noise emissions levels of activities and operating equipment to provide an overall view of the predicted noise levels around the project site. Considering the fact that the nearest receptors affected by noise are residential and educational institutions, and because plant operation during the day and at night are expected to be the same, the project will be designed to target an overall project plant contribution of 45 dB(A) at the nearest receptors, noting that at worst only a marginal addition to pre-project noise level would occur (<3 dB(A)).
The results of the model showed that operational phase noise levels are estimated to comply with the WBG EHS Guidelines limits of 45 dB(A) and not to result in increased background noise by more than 3dB(A), except for the isolated house located approximately 350 m from the site and the ‘temporary’ house (300 m North-West) for which the predicted noise levels would reach 50 dBA. As stated in the ESMP, Atinkou will conduct a formal assessment of alternatives to prevent and mitigate impacts due to noise and vibrations at the nearest receptors. Based on results of this assessment, the company will engage with the owner/users of these isolated houses (to the West of the site) to consider the potential options to limit the impact of elevated noise and vibrations on the occupant above the WBG General EHS Guidelines (2007) noise levels. This could include source control at the power plant if technically and financially feasible and cost effective, acoustic isolation of the house if technically feasible and accepted by the occupants, or the resettlement of the house to a quieter location, located further away from the power plant, also if accepted by the occupants. If resettlement is the selected option, affected persons will be incorporated into the RAP prepared by the company and compensated according to IFC PS5 requirements (ESAP #14).
A number of additional mitigation measures for operational noise are proposed in the ESIA, to minimise the potential noise impact and that includes regular noise monitoring following the commissioning of the plants, information of the public of plans and effort to minimise noise and establish a complaints response procedure and consideration of additional mitigation measures in the event of noise complaints following the commencement of operation.
Solid Waste Management
The project construction will generate general solid waste (household waste, plastics, paper, food, packaging, glass, office equipment, scrap metal and wood) and hazardous waste (waste oil, oily rags, filter cartridges, absorbent materials, medical waste, paint waste and paint cans and lead-acid batteries). Most of the hazardous waste will comprise oil-contaminated materials. The primary hazardous waste during operations will include: the oil collected from oil water separators; sludge and residual solids from oil and grit separator tank; waste water treatment plant sludge; compressor cleaning waste; oil filters; batteries; oil and grease contaminated maintenance waste; used oil/paint/chemical drums; oil contaminated water or spills from oil storage areas; used oil generated in maintenance; oily rags/oil contaminated scrap from maintenance activity; and transformer oil.
Atinkou will identify appropriate authorized entities that can handle the different types of hazardous wastes that will be generated during construction and operation. As stated in the ESMP, capability to treat and dispose of the different types of waste in accordance with WBG General EHS Guidelines and national laws will be considered in selection of waste management entities. Further, the Company will implement procedures to assure itself that the hazardous waste treatment and disposal facilities remain compliant with the national laws and good international industry practices. As presented in the ESIA, a waste Management Plan will be finalized prior to the start of construction for proper storage and disposal of all wastes generated during construction. A post-construction survey of the construction area will be conducted to confirm that all debris and wastes have been removed and appropriately disposed at the end of the construction phase.
Hazardous Materials
During the construction phase, fuel oil, lube oil, paints, and maintenance products are likely to be required. No bulk storage of chemicals is anticipated. Through contractual requirements and as stated in the ESMP, Atinkou will ensure that good site management practices are observed by the EPC during construction, and that hazardous materials are properly stored and handled at site (e.g. as appropriate within secondary containment, double walled tanks, over filling alarm system, etc.).
During the operational phase, type and volumes of hazardous materials stored and used at the power plant will also be limited and include acid, caustic soda, fuel, solvents, lubricating oils, transformer oil, natural gas (not stored on site but used).
As specified in the ESMP, Atinkou will develop and implement a procedure for appropriate storage of these materials during construction and operation phases, including appropriate segregation, labeling, storage based on compatibility assessment, where required provision of secondary containment, corrosion resistant lining as required and access control.