Ghana - Thermal Power Project : environmental assessment (Vol. 3 of 7) : EIA : Takoradi Thermal Plant : addendum 1 revisions to EIA (final draft)

Environmental Assessment/Analysis Reports •_ _ l Report E0051 Ghana * Thermal Power '1 EA Category A Environmental Assessment 3of4 August 1993 This report has been prepared by the Borrower or its Consultant Republic of Ghana Volta River Authority Takoradi Thermal Plant Addendum I Revisions to Environmental Impact Assessment Final Draft September 1993 Acres International Limited Addendum 1 Revisions to Environmental Impact Assessement Final Draft In response to preliminary review comments received from the World Bank and the African Development Bank, this addendum is provided to clarify the following points. 1 Cooling water discharge temperature with one steam turbine generator (300 MW) and two steam turbine generators (600 MW), and predicted extent of hydrodynamic mixing zone and thermal plume under each of those operational conditions. 2 Maximum ground level NOx concentrations under open cycle (bypass mode) operation prior to availability of water for either combined cycle operation. NOx control or desalination plant operation. Pages incorporating the revised text are attached. Please attach this addendum to your copies of the above noted report. These changes have been included in the 'EA Summary' published September 1993. Revised Pages Executive Summary This report has been prepared to review and evaluate the environmental impact of a proposed 300-MW, with the potential to upgrade to 600 MW, combined-cycle thermal generating plant to be located 15 km northeast of Sekondi-Takoradi. near the village of Aboadze. This environmental assessment addresses the requirements of the African Development Bank and also those of the World Bank as a Category 'A' project. The analysis involved a 1-wk visit to the area by an environmental specialist and the provisions of socioeconomic and other data by VRA staff, both of which supplemented site visits by engineering staff. Some monitoring data is presented, while further information is being collected, and will be included, as an addendum to this report at a later date. The plant will initially use light crude oil, or distillate oil with the possibility of later conversion to natural gas should a supply become available. The plant requires a 3.0 m conduit for once through cooling water, drawing 5.7 m3/S from the sea. Current estimates indicate a construction work force of approximately 400 including 75 expatriates and an operating work force of up to 125. Plans include a townsite for construction and operations staff, likely including a first- aid clinic. A permanent townsite will be developed for operating staff, and a school will be provided if existing community services are insufficient. There will be a self- contained sanitary sewage treatment system and a desalination plant to provide an adequate long-term, water supply for operational and domestic requirements. In addition, the plant will be connected to the municipal water supply. In general the analysis indicates that the plant will have modest, but mitigatable, environmental impacts. The key potential issues include: - the effect of the cooling water on marine life and the consequent effects on the thriving fishing industry of Aboadze and neighboring villages - the effects that the loss of site land (some 35 - 40 ha) will have on nearby families who currently practice predominantly subsistence level agriculture on that site - air quality impacts - potential spillage and/or leakage of oil. Cooling Water and Marine Ufe Normal ambient sea water temperatures are 26 to 270C, however, water temperatures occasionally rise to 30 to 310C. Draft guidelines proposed by the Environmental Protection Council of the Ghanaian Ministry of Environment suggest that the maximum ambient water temperature at the beaches should not exceed 33*C and not raise temperatures by more than 5"C. The State of Florida uses 360C maximum for open waters and at the edge of a mixing zone. The proposed 300 MW plant would operate with a 90C AT, while the potential 600 MW plant would operate with a 120C AT. Thus the 300 MW plant's discharge would periodically exceed 360C, while the 600 MW plant would routinely exceed 360C. The use of a discharge nozzle which creates an exit velocity greater than 2 m/s, would ensure that discharge temperatures above the 360C level are confined to a small, localized mixing zone (less than 20 m from discharge point for the 300 MW plant and less than 200 m for the 600 MW plant). Modeling results have indicated that the temperature rise will be no more than 0.5C beyond 200 m from the discharge, even under two unit (600 MW) operation. In addition, the discharge will be directed offshore and located beyond the 6 m depth contour. This will ensure that the above noted criteria are met. No measurable damage is expected to the fishery. Revsed September 10. 1993. ii It is recommended that baseline monitoring be undertaken to assist in selecting the optimum intake and outfall locations and to ensure that predictions of impacts are verified and applicable standards are met. Farm Land Loss It is estimated that some 35 - 40 ha of the site are farmed - generally by women, as income and food supplements for their families. In some cases, quite valuable crops (e.g., coconut palm, tigemuts) are grown. The lands are farmed by tenants. Commercial farmers pay for the use of the land with a share of their crops grown, while subsistence farmers make a nominal contribution to the land owner. The concern is that any compensation will be paid to the land owners and not to the tenant who may find it difficult to find an alternate farm site. It is important that this issue be addressed in the compensation structure and it may be appropriate to provide assistance to tenants in locating other lands. The development plan for the project includes preservation 2 of the beach ridge coconut palm plantings. Air Quality The major air quality concern of the project is related to NOx emissions. Source emission standards are measured in nanograms per joule and the World Bank guideline for NOx is 130. The plant could generate approximately three times that level without control mechanisms. Water injection technology used to lower NOx emissions will be installed on the combustion turbine burners, however, due to limited fresh water availability on site, may be delayed by up to 12 months from the start-up of the first CTG. To provide, a sufficient and reliable source of water for this control, a desalination plant is provided in the plant design. Assuming no delays in contract award or schedule, the water supply from the desalination plant will be available shortly after the start-up of the second' CTG. thereby ensuring that emission levels are below applicable standards for operations beyond this point. III It is suggested that an environment/social development officer be appointed to the project. The task of this officer will be to oversee the various monitoring programs that will be taking place and to ensure that impacts, both natural and socioeconomic are dealt with and minimized. A comprehensive environmental training programme should be provided to supervisory staff. A detailed monitoring and baseline/data gathering programme is outlined. This will supplement the existing information, provide the data required for siting the marine structures and determine if emissions are in compliance with the guidelines. As this will be the first large scale thermal power plant in Ghana, detailed effects monitoring will aid in developing future mitigation requirements and help determine if the predictions and mitigations given here are correct. As the local community of Aboadze will be changed by the presence of the plant, it is recommended that the population should obtain some benefits from the project to offset these changes. VRA should consider assisting the community in some of their development projects. iv 5-31 concentration (100 ug/m3). however, ground level concentrations during shorter periods of time (0.5 and 1 h averages) generally exceed this value, especially at stack heights of less than 60 - 75 m. The preferred stack height (due to cost, aesthetic and other considerations) was 40 t5 m. At that height. predicted ground level concentrations from an uncontrolled plant, at C stability condilions (the worst case) are as follows - annual mean 58 pg/m3 - 0.5 h peak 98 pg/m3 - 1 h average 163 pg/M3 - 24 h average 67 pg/M3 Considerable concern was expressed by ADB project appraisal staff with respect to these emissions and projected ground level concentrations. Considering the potential for a future development of a similar size, and the need to maintain provision for contributions from other sources, it was recommended that the station contribution not exceed 1/3 of the total, and preferably be less than 10 pg/rm. Under the worst case scenario, a 1/3 contribution (=30 pg/m) would require a stack height of 80 m. It was therefore decided to investigate other options as well. High NO, levels are produced from combustion at extremely high temperatures. To control NO, emissions both dry and we[ techniques have been used. Both these technologies were investigated to ascertain their feasibility for use in this plant. While reviewing available technology, it became apparent that dry 'LO NOx' burners have been developed, and are in widespread use for gas fired installations, achieving emission rates of as low as 5% of those now predicted for the oil fired equipment. Although dry LO NO, burners for oil firing-are in some stage of development and most manufacturers indicate that prototype units are being investigated, there is no manufacturer at this time prepared to indicate a definite schedule for the availability of these new burners, nor identify the obtainable emission values. Published data from research papers do however indicate potential reductions to approximately 2/3 of the present emission levels. Further reduction can be achieved by injecting steam or water into the combustion zone, which satisfactorily modifies the NOx generation and in conjunction with sophisticated computerized control, achieves a level of emission well below the allowable emission criteria. However, the present level of control 5-32 achieved by dry LO NOx' burners is marginal, as reflected in the values presented in Table 5.4. Considering that dry 'LO NOx' burners will become available at a later date It was Investigated whether a temporary load reduction would achieve an emission rate within the established criteria. While theoretically a load reduction does produce a lower heat release, today's high efficiency units use multi burner arrangements which maintains the flame temperature and hence little or no variation of NOK can be achieved. Increasing the stack height results in a reduction of the ground level concentration but does not produce a reduction of the emission. To increase the stack height incurs an extra cost especially as the plant is fitted with a total of four (4) stacks. The other technology for NOx control and the one being currently used at a few oil fired plants throughout the world, involves injection of fresh water into the burners. Considerable quantities of water are required (i.e., water is added in the ratio of .5 to 1.8 kg per kg of fuel burned). Based on a fuel consumption of 25 000 to 30 000 kgth per turbine this would require a water supply of 25 000 to 108 000 kg/hour. Additional model runs were undertaken utilizing emission characteristics (Table 5.4) of those CTGs employing NOx control with either dry low NOx burners or with water injection. The predicted emission rates and ground'level NOx concentrations for similar operating conditions and stack heights are presented in Table 5.5. Model runs for intervening stack heights and bypass mode of operation are presented in Appendix E (tables and figures E2.1). Emission rates for the dry NOx control system are estimated at 297 ng/J. These still exceed the World Bank guidelines by a factor of over two. To achieve the recommended ambient GLCs the stack height would still have to considerably exceed 40 m (Appendix E). For water injection, the emission rate of 77.9 ng/J falls considerably under the guidelines. Ambient GLCs with a 40 m stack are considerably less than with either the uncontrolled or dry Nox control condition, and are as follows - annual mean 10.0 pg/m3 - 0.5 peak 34.4 pg/m3 - 1 h average 21'.3 pg/mi - 24 h average 11.6 pg/m3 5-33 However the selection of this option would require that a constant, reliable source of water for injection be located. The availability of a fresh water supply at the proposed site was investigated. The site was selected for its proximity to the ocean to provide access to cooling water for the condensers of the steam turbine. However, the fresh water supply is at present limited to a single source, that is a supply from the Ghana Water and Sewerage Corporation (GWSC) at Inchaban in the amount of 100 000 g/d (378.5 m3/d). GWSC.provides about 300 000 g/d of municipal water to the villages of Aboadze and Aboesi, of which. 100 000 g/d could potentially be assigned to the new plant. No additional water is at this time available from this source, which is known to be erratic during dry periods. Hydrologic data is not adequate to allow confirmation of the overall reliability of this supply. Aternate water sources are the River Pra. about 20 km each of the site, or saline water from the ocean. Water from the Pra is now piped to Takoradi for their muni';ipal water supply. This supply is also very dependent on the river flow which varies considerably with the season. To create a second water supply from the Pra would likely affect the reliability of the Takoradi supply and would necessitate a new dam or weir to be built on the River Pra. Minimally, this would require an intake for a pumping station, and a 20 km pipeline to the plant. Its dependability could not be assured without creation of an adequate storage reservoir. A desalination plant using sea water would meet the requirements (a high grade of purity) of water for injection. A nominal plant of 300 000 g/d. would be required, equivalent to approximately 47 500 kg/h. which would represent a water injection rate of 1 kg/kg at a fuel flow of approximately 28 000 kg/h per unit. It would also require other system components consisting of seawater pumps, additional pumphouse space, reverse osmosis units (complete with their feed systems comprising pumps, filters, piping systems, etc.) and an increase to the proposed demineralizers to handle the arger water flow. From the above discussion it is then recommended that NO, control be installed at the proposed Takoradi Thermal Plant. The technology to be used is the water injection system. To ensure a constant and adequate water supply a desalination plant will be buiL 5-34 In order to satisfy the requirements of the lenders (financiers) for the project, four separate packages have been developed, related to combustion turbines, steam turbine, transmission and housing. This has resulted in assl3nment of the desalination plant to the STG package, as both require a sea water supply. The end result of this is a scheduling problem in that the first combustion turbine will operate for 3 - 6 months without NOx emission control (potentially 6 - 12 months or more If delays occur in the awarding of the STG contract). Given that only one unit will be operational and will be in bypass (simple cycle) mode, ground level concentrations will be reduced from that with two units, and would be 50% of that shown in Appendix E2.1(b)-1 (i.e., 4.6 pg/M3 vs 92 Pg/m3 for uncontrolled two CTG operation, bypass mode). it is felt that approval for temporary operation should be granted, to allow the plant to operate before the long-term water supply is available. Operation of both CTGs in combined cycle mode, without water injection, will exceed emission criteria, and may result in ground level concentrations up to the maximum allowed (annual average <100 pg/M3, 24-h average <200 pg/m). As ambient wind speeds in the project area (Appendix A) are quite low. two model runs were undertaken. representing one and two unit uncontrolled combined cycle CTG operation, to provide preliminary information concerning the potential point of impingement of the plume under light wind conditions. The results of those runs are presented graphically in Appendix E, Figures E2.1(a2) and E2.1(a3). As shown. plume impingement is expected to be a considerable distance downwind (beyond 10 kIn) under those conditions. Maximum ambient GLC under two unit operation is predicted to be approximately 70 pg/M3, which is below the 100 pg/M3 annual average criteria. One unit operation would more closely approximate the GLC goals previously described (30 - 35 pg/m3). However predicted maximum ground level concentrations in bypass mode are well below recommended limits, and ambient conditions will be monitored. Should testing reveal GLCs in excess of the maximum allowed, then it would be recommended that the second CTG not be allowed to operate until the water supply from the desalination plant is available to provide NOX control for both units. In no case should both units operate in combined cycle mode without water injection operational and in use. Thus the desalination plant should be placed on the critical path within the STG contract, such that it is available and capable of providing water for combined cycle operations. Groundwater from a series of boreholes may be able Revised September 10. 1993. 5-53 the season, and total temperature of the effluent Is not to exceed 33.30C or 322C, depending on season. In open waters (beyond the 5.7-m contour), the temperature at the point of discharge must not exceed 9.40C above ambient, and surface waters of the receiving environment shall not exceed 36.10C. Also, the discharge should be placed far enough off shore to ensure that water criteria in the coastal zone are not exceeded. Florida regulations also provide for thermal mixing zones inside which temperatures may exceed the above criteria, provided two conditions are met. First, the mixing zone must provide for the protection and propagation of a balanced, indigenous population of shellfish, fish, and wildlife in, and on the body of water into which the discharge is to be made. Second, that the temperature criteria must be mel at the edge of the mixing zone (State of Florida. 1993). Hydrodynamic modelling was conducted to provide a preliminary assessment of the impact of the thermal discharge on the receiving waters. The modelling included both single port and multiple port outfalls. For the single port outfalls, four scenarios were modelled in which the thermal discharge rate and temperature, and ambient current velocities were varied. The results of this modelling are presented in Appendix F. Figures 5.3 and 5.4 portray the thermal plumes resulting from a single port outfall under two of the scenarios modelled, referred to as Case 1 and Case 4. In Case 1, the thermal discharge was 6.4 m3/s with a 9C rise above ambient temperature and an ambient current velocity of 0.25 m/s. This case was selected to model normal one STG unit operation, however, the plant would be designed to operate with a 120C temperature rise if expanded to 600 MW. Under Case 4, the thermal discharge was 11.3 m3/s with a 120C rise above ambient temperature and an ambient current velocity of 0.10 m/s. This approximates 2 STG unit operation, with low ambient current flow (worst case scenario). The results of the modelling (discussed in Appendix F) indicate that the impacts of the thermal plume will be limited. Under Case 1, the temperature of the plume was predicted to be 4.5DC above ambient water temperatures at a 10 m distance from the outfall, and less than VC at 15 m from the outfall. Under Case 4. the temperature was 60C over Revised September 10. 1993. 5-54 ambient at a distance of 16 m, while the mixing zone boundaries were predicted to extend approximately 200 m from the outfall. As suggested by Figures 5.3 and 5.4, in both cases the thermal plume was predicted to be less than 1C above ambient water temperatures at the edge of the mixing zone, while at a distance of 2000 m the temperature of the plume was projected to be 0.SC (or less) above the ambient temperatures. The other scenarios modelled provided similar results (see Appendix F), suggesting that the thermal impacts will be limited. The temperature of the final effluent of the proposed Takoradi plant will potentially exceed the ambient sea temperature by 90C for 300 MW operation and by 120C at full (600 MW) plant operation. For the presently proposed development (300 MW), this increase will result in discharge temperatures ranging from 33"C during upwelling events to 39C to 40C during much of the remainder of the year. On rare occasions, discharge temperatures could potentially exceed 400C. To moderate these high temperatures the final design of the discharge portal will include either an off-shore diffuser or a nozzle. If a single orifice is employed, it should provide an exit velocity of not less than 2 rmsec. Both types will provide rapid mixing of the effluent. in a small area where the discharge-induced currents exceed the ambient alongshore currents. As the discharge currents approach the velocity of the ambient currents, the thermal effluent will rise to the surface (due to temperature-related density differences). At the surface, further temperature reductions will take place at a slower rate, and will occur both due to atmospheric cooling and further mixing. Additional modelling will be required by the successful contractor to undertake the final design of the exit portal, to assure adequate mixing and cooling and meet design criteria. The increase in temperature of the discharge (above ambient) at full 600 MW operation will not meet the Florida criteria for open water discharges, however, the diffuser will act to rapidly mix the discharge with ambient water, resulting in attainment of the Florida and Texas criteria at the edge of the mixing zone. Revised September 10, 1993. 5-59 The exact location of the diffuser cannot be identified at this point. The diffuser should, however, be located off shore beyond the most distant 6 m contour in an area away from any Important shellfish beds and fish concentration areas. It should also be pointed offshore, and maintain an exit velocity of not less than 2 m/sec. Preconstruction Investigations will be required to select the appropriate location. This design will ensure that temperatures at the edge of the mixing zone are less than 90C above ambient and below 360C total temperature. When the plant becomes operational, modelling and/or drogue studies of the behaviour of the thermal plume should be conducted to identify where and at what temperature the plume will enter the coastal zone (i.e., inside the 6-m contour). The final design and siting of the discharge should ensure that the temperature (of the plume) at the edge of the mixing zone does not exceed 2*C above ambient, or 33*C maximum temperature at the point where the plume enters the coastal zone. Adherence to these criteria will also meet the EPC's requirements. Chronic or Acute Discharges of Toxic Substances In Cooling Water The main substance that could be present in the cooling water discharge at toxic levels is chlorine. A chlorination system is to be included in the circulating water system to chlorinate the water, as well as to prevent biofouling of the heat exchangers and piping. The chlorine will be produced using an electrolytic chlorinator (sea water will be electrolyzed to produce a hypochlorite solution). Chlorination will be an intermittent activity, but levels will be high during activation. Excessive chlorine can kill or damage aquatic life. The residual chlorine at the discharge point will be considerably diluted. It should at no time exceed 0.2 mg/L The cooling water circuit will be the final receptor for all others effluent streams on Site. Prior to its installation, these streams will have been discharged to a feeder stream of the Anankwari River. All liquid effluent streams will be joined together on Site, and discharged as one common waste stream. This combined stream will be monitored and will meet the criteria specified in the following section and in the tender documents for liquid effluent. Revised September 10. 1993. 5-60 The other discharge to the cooling water circuit will be from the desalination plant. This could amount to up to 750 m3/d (<0.01 m3/s), which is a small amount, compared to predicted cooling water discharge. This discharge will be of elevated salinity, but is not expected to have significant impacts, due to its limited volume. (c) Discharge of Wastewater Discharge of effluents can have detrimental effects on the water quality of the receiving water body. For example, excessive amounts of organic matter can deplete the oxygen available for the existing organisms. High phosphate levels can produce rapid growth of algae, etc. in the receiving water. Wastewater will come mainly from sewage and preoperational cleaning requirements. Sewage from the proposed plant and the housing complex will all be treated at one central facility, consisting of an activated sludge extended aeration treatment system. The system will be designed to meet a BOD5 of 25 mg/L and suspended solids of 200 mg/L Wastewater will also be derived from preoperational cleaning of the HRSGs and other operational chemical cleaning. It is proposed that these wastes will be stored in a suitably lined lagoon or tank (i.e.. one which will not react with the chemical cleaning solutions). The wastes will be neutralized by the addition of lime and dissolved metals, such as iron, will be precipitated out of solution. A polymer may be added to help coagulate and settle the solids. Once the solids have settled, the clear water will be pumped out to the discharge outfall. As the lagoon fills, the solids will be cleaned out and taken to the sold waste landfill area. To ensure that the wastewater is strictly controlled, the effluent from all systems will be discharged through one common pipe. This effluent will be monitored to ensure that the criteria below are met. These criteria should ensure that the water quality of the receiving body is not negatively impacted. The effluent will initially be discharged into a feeder stream of the Anankwari River but will be diverted to the once-through cooling water discharge system when it becomes operational. Provision will continue to be retained to monitor this effluent before mixing with the cooling water discharge. 7-9 supplies in the area. The desalination plant is expected to be operation within 6 mo after start-up of the first unit. Thus water for NO, control could be provided, If an alternate source of water (other than CW circuit) could be made available on a temporary basis (potentially, groundwater from a series of on-site boreholes). However, as planned, the first CTG will operate in an uncontrolled manner for a period of time predicted not to exceed 6 mo, assuming the present schedule is maintained. During this period, its NOx emissions will exceed applicable standards, but ground level concentrations are predicted to be below maximum acceptable levels. The second CTG unit must not come on line until the cooling water supply is available and desalination plant operation, such that NOx control can be implemented, if the air quality monitoring program associated with the project. Indicates that maximum ground level concentrations are- being exceeded. Preferably, the schedule for the intake and outfall construction should be advanced, such that the water, and the desalination plant, are both available and operational when the first unit is commissioned, and definitely before the second unit is operated. A desalination plant will be built on-site to provide the long-term fresh water requirements. The cost of this mitigation measure has been estimated at approximately US$ 5 million. If the present project schedule is followed. 7.2 Aquatic Conditions Further marine investigations are required as outlined in Section 9 to select appropriate locations for the intake and discharge portals, and the SPM. It is required that the studies to select an appropriate location for the SPM be undertaken and completed prior to contract award in order to provide input to the final site selection. Studies to select appropriate intake and discharge locations will require a 12-mo period (in order to evaluate seasonal differences) and will be completed prior to November, 1994. (See construction schedule, Figure 3.1.) The major mitigation costs will be in the form of the monitoring. Location of Intake The intake must be located upstream of the Raoni and Sherbro banks and inside the 10-m contour. The intake will be fitted with a velocity cap, and raised off the sea bed. Buoys shall be placed to indicate the location of the intake. Detailed preconstruction marine investigations will be required to select an intake location that does not inflict undue impacts. These studies will include physical and biological components. 7-10 At this time, It is not considered that the environmental requirements will aflect the cost of the intake construction, which is estimated at $14.5 M. Location of the Discharge Outlet Field studies will be required to determine the most suitable location for the discharge outlet. Generally, the outfall must be located off shore of the most distant 6-m contour and away from Important shellfish beds and fish concentration areas. It is expected that only a nozzle will be required but the exit velocity of the water must not be less than 2 m/s to ensure rapid mixing of the heated water, and be directed offshore. The nozzle will meet a T. of 33*C at the edge of the mixing zone, and <2C above ambient temperature rise in the near-shore zone (beach). The outfall shall extend a minimum of 1500 m from shore. Cost of the outfall construction is approximately US $14.5 M, which includes provision of the nozzle. The field investigations required to select an appropriate discharge location will be undertaken at the same time as the intake site selection studies. Location of the Single-Point Mooring (SPM) The SPM must be located downstream of Sherbro and Raoni banks in an area such that any oil spilled at the buoy would not be swept directly into Shama Bay by long- shore currents or local gyres. Hence, an oceanographic study will be required to select an appropriate location. This study should be undertaken during the period of the low flow in the Pra River; thus, would be undertaken prior to contract award (January/February 1994). Warning lights shall be required on the SPM. Oil Spill Response/Recovery Mitigation Plan Currently, there are no dedicated oil spill response teams or oil recovery equipment in Ghana and there is a probability that spillage or leakage may occur at the SPM. Therefore. VRA should obtain and dedicate such equipment and develop an action plan to provide an 'initial response' capability. The goal of the initial response would be to stabilize the situations, and contain a spill or release to as small an area as possible, preventing further dispersal along the shoreline or out to sea. The oil spill response plan of the VRA should be integrated with the National Oil Spill Contingency Plan (NOSCP). Such an integration would allow recovery/cleanup operations to be then conducted under the auspices of the NOSCP following initial containment by VRA. This approach would limit and minimize VRA's liability for environmental and other damages incurred by the oil spill. At the same time, this Revised Sepoeber 10. 1993.