Tanzania - Emergency Power Supply Project : environmental assessment (Vol. 2 of 2) : Preliminary hydrogeological investigations

Emergency Power Projects Environmental Audits of the Thermal Power Plants and Power Co-generating Units: PRELIMINARY HYDROGEOLOGICAL INVESTIGATIONS E950 Volume 2 p~. ~ s_s:i T-- ,.~~~~~~~~** -- .- MWANZA NYAKATO POWERSTATION Report by: Leonard B. Kassana, Directorate of Corporate Planning & Research, Tanzania Electric Supply Company Limited, P.O. Box 9024, Dar es Salaam. Tanzania. April 2004. Leonard Kassana/Nyakatosubstation ReportCover I Page I of 1 4/14/2004 ._ FIE C Y' -" h ' ' ;wsw_~~B _ . . ~ ~ L  Emergency Power Projects Environmental Audits of the Thermal Power Plants and Power Co-generating Units: Preliminary Hydrogeological Investigations at Mwanza Nyakato PowerStation TABLE OF CONTENTS 1. INTRODUCTION 2. SCOPE OF WORK 3. INVESTIGATIONS 4. RESULTS 5. CONCLUSION AND RECOMMENDATION 6. REFERENCES 7. APPENDICES: a. Appendix 00: Field LSD Results b. Appendix 01: Draft Terms of Reference of Environmental Audits of the c. Appendix 02: Machines technical Specifications (Equipment Data Sheet) and Additional notes by the author of this report d. Appendix 03: Maps e. Appendix 04: Photo documentation during the Investigations Leonard Kassana/Preliminary Hydrogeological Investigations Page 1 of 5 4/15/2004  Emergency Power Projects Environmental Audits of the Thermal Power Plants and Power Co-generating Units: Preliminary Hydrogeological Investigations at Mwanza Nyakato PowerStation 1. INTRODUCTION This work is a part component of the Environmental Audits of the Thermal Power Plant and Power Co-generating Units Projects that are currently on the discussion table between the World Bank and TANESCO. There are three options that are being considered for implementation for assisting TANESCO to meet its emergency power generation needs due to poor hydrological conditions in its critical catchments areas. Details on the 3 options in subject are found in the Draft Terms of Reference for Environmental Audits of Thermal Power Plant and Power Co-generating Units hereby appended (Appendix 01) for the reader to refer to. The option that is being worked on is the one that includes 18x 1 Mw plant to be leased from the Geita Gold mines to be installed at TANESCO'exisitng generations site at Nyakato, Mwanza. See Appendix 02 for the specifications of the machines and Additional notes on the rudimentary financial analysis by the author of this report. 2. SCOPE OF WORK This part of the work is to assist and guide the environmental audit for the Mwanza Nyakato PowerStation. The geological work was commissioned to TANESCO Engineering Geologist, Eng. Leonard Kassana for making preliminary assessment of the hydro-geological conditions of the area within the following scope: 2.2. Preliminary assessment of water table in the area 2.3. Preliminary assessment of the geological formational lithology within the site 2.4. Tentative location of boreholes that are meant for monitoring pollution of ground water by water and oil effluents from both existing and planned thermal generating units 2.5. Possible direction of the groundwater in the area 2.6. Establish tentative costs for boreholes to be drilled at the site. 3. INVESTIGATIONS The following methods of investigations were applied during the course of this short study: 3.2. Interpretation of topographical maps at 1:50,000 and 1:2,500 3.3. Geological map at 1: 100,000 3.4. Light Static and Dynamic Sounding (LSD) as pilot hole for hand augering 3.5. Hand auger to assess lithology and ground water table 3.6. Survey and interview local professionals around the site regarding hydrogeological conditions. 4. RESULTS 4.1. Site Geology: The site lies within Greenstone belt of Tanzania whose age is within Precambrian age. The site lies about 7 km along Mwanza - Musoma road. The area is underlain by Granite and due to the preliminary nature of this study, the author of this report is not able to differentiate the granitic rock. The average bedrock level at the site varies between 1.6 m and 2.0 m as preliminarily determined by Light Static and Dynamic Sounding method (see Appendix 00). Leonard Kassana/Preliminary Hydrogeological Investigations Page 2 of 5 4/15/2004  * *1 Emergency Power Projects Environmental Audits of the Thermal Power Plants and Power Co-generating Units: Preliminary Hydrogeological Investigations at Mwanza Nyakato PowerStation In the yard, there are few granitic outcrops scattered, protruding above the surface. Spherical weathering is much dominant in the area making vertical and lateral jointing system to be very important. For more information on regional geology, the reader is referred to the provisional publication of the quarter degree sheet (QDS) #33 of Mwanza by Geological Survey of Tanzania, 2002. The site is covered by the soil derived from granitic rock whose thickness varies between 1.6 m and 2.0 m. The hand augured samples have the following characteristics: Table 1: Preliminary Lithology at Nyakato PowerStation area Depth in m Description Remarks 0.0 - 0.2 Brown, loose, Silty SAND 0.2 - 0.6 Grayish Brown Sandy SILT 0.6 - 0.8 Grey fine Sandy SILT 0.8- 1.6 Reddish Brown Clayey Sandy This is equivalent of SILT with occasional gravels weathering grade IV NB: Groundwater in the hand auger hole is Dry. For visual view, the reader is kindly referred to the photos in Appendix 04. 4.2. Hydrogeology of the site: Preliminary investigations during this period show that hydrogeology of the site is much controlled by underlying the granitic environment. The underlying rock is shallow seated ranging from 1.6 to 2.0 m depth. The underground drainage is controlled by rock mass jointing system. The rock mass is dominated by vertical and lateral jointings due to special type of weathering known as spherical weathering. Soil mass is derived from granite and the nature of the soil is much sandy hinting that soil permeability may be moderate to high. Findings from the light and shallow sounding and borings done during this short study show that water table are deeper than 2 m. The groundwater measurements in 3 LSD holes using water dipper showed that all of them are dry down to 2 m. This exercise took place in the month of March 2004 toward the end of dry season. According to the Civil Engineer, Tanesco Mwanza, Mr. Nnunduma, the water table was struck at 3 m in the soak pit dug at about 100 m south east of the LSD2/HA1 for the substation staff houses. The bedrock is very shallowly inclined, dipping between south east to east hence somehow governing the general flow direction. More hydrogeological parameters must be investigated in the future to determine absolute permeability of the soil mass and rock mass. Insitu permeability tests have to be done in the boreholes that will be drilled at site. Water table will also be confirmed during this future exercise. Leonard Kassana/Preliminary Hydrogeological Investigations Page 3 of 5 4/15/2004  Emergency Power Projects Environmental Audits of the Thermal Power Plants and Power Co-generating Units: Preliminary Hydrogeological Investigations at Mwanza Nyakato PowerStation 4.3. Observation BHs: Based on site conditions, two boreholes (BHs) are proposed to be drilled at two tentative locations in the order of 200 m apart, see the site map on Appendix 03. One BH will be located at location behind the old power house but downstream of the Oil interceptor pit. The reason for this proposed BH: * To monitor ground water pollution 'which I think has been caused by discharge of oil due to the collapse of the pit. This happened at the time of our stay. * Oil spillage around the oil interceptor has been significant and it is therefore recommended to monitor the pollution in the ground water. The second BH will be at a location considered suitable enough to intercept the flow of the ground water of any effluents from the would be new installations. The preliminary costs for borehole drillings are based on the discussions conducted with Mr. Theobald Theonest, Head of Drilling Section, Drilling and Dam Construction Agency at Mwanza Office. Table 2: Indicative Costs for BH Drilling and Testing at Mwanza Nyakato P/S Item Description Unit Rate in TAS Sum in TAS 1 Core drilling - rock 36 m 150,000.00 5,400,000.00 2 Soil drilling 4 m 50,000.00 200,000.00 3 Lugeon Test 8 nos 50,000.00 400,000.00 4 Insitu Soil Permeability, 4 30,000.00 120,000.00 _____ 4 tests 5 Mobilization and Ls 2,000,000.00 Demobilization 6 SUBTOTAL 8,120,000.00 7 Contingency (23%) 1,880,000.00 8 SUBTOTAL _ 10,000,000.00 Notes: These costs are not meant to cater for casings material as part of the permanent stabilization of the observation holes which could not be immediately established due to time constraints of this work. Leonard Kassana/Preliminary Hydrogeological Investigations Page 4 of 5 4/15/2004  Emergency Power Projects Environmental Audits of the Thermal Power Plants and Power Co-generating Units: Preliminary Hydrogeological Investigations at Mwanza Nyakato PowerStation 5. CONCLUSION AND RECOMMENDATION *: Field observations at site show clearly that oil spillage around the area is notable. Areas around 'oil interceptor, storage tanks and drainage system for extracted water from oils' show the extent of pollution on the ground. See appendix 4. *: The soils in the area are sandy in nature and rock mass is granitic whose dominant jointing type is due to spherical weathering. Jointing system may be moderate but infillings between the joints/faults may range from clayey to gravel materials which govern the degree of conductivity/permeability of the discontinuities. *: It is therefore recommended to have two observation boreholes within the site of Mwanza Nyakato PowerStation to cater for pollution monitoring adequately. The indicative budget for drilling and testing is given in table 2. Recommended depth for each borehole is 20 m to cater for maximum possible interception of discontinuities. *: Equipment for water sampling and ground water measurements in the observation holes must be purchased and kept at site. * Recruiting a staff at Mwanza for sampling and measurements is essential. This may be done by experts from Tanesco HQ during the drilling supervision and testing period. A cost for the equipment will be established at that in the later stage of the implementation. *: A schedule of observations, sampling and testing should be devised by the Environmental Engineer. *: Analysis of the results should be done by TANESCO HQ Environmental Engineer who will be responsible for advising on the strategies how to control pollution. 6. REFERENCES: * Nilsen, B & Palmstr0m, A, 2000: Handbook #2, Engineering Geology and Rock Engineering, Norwegian Group for Rock Mechanics (NBG). *: Survey and Mapping Division, Government of the United Republic of Tanzania, 1994: Topographic Map 1:50,000, Mwanza, Sheet # 2, Edition 2-TSD. * Geological Survey of Tanzania, 2002: Provisional Mwanza Quarter Degree Sheet #33 and Part of 21, 1:100,000, Initially Geologically Surveyed by G.M. Stockley Geologist 1940. Leonard Kassana/Preliminary Hydrogeological Investigations Page 5 of 5 4/15/2004  Measurement of Baseline Environmental Information At Mwanza Power Station By Dr. Eno& Masara Chemical and Process Engineering Department, University of Dar es Salaam 1. Introduction The Mwanza power station is located in a rural area. There are no high rising structures (i.e. tall buildings, hill tops, or thick forests) in the vicinity. The dispersion of exhausts from stacks is thus free without significant downwashing due to high rsing structures. The setting of the investigation is shown in Figure 1. Major sampling points are numbered (1-17) and labelled (A - D). Note that Figure 1 is not true to scale. The following investigations were carried out as required bythe client: i) Noise measurement (results in Table 1); ii) Ambient air measurements for C02, 02, NO. and SO. (results in Table 2); iii) Soil sampling and testing for heavy metals, and S042-, Cl- and NO3- (results in Table 3); iv) Water sampling: ground or surface and testing for S042-, 1- and NO3- and phenols (results in Table 4); and v) Sampling and testing for PCBs  Sub Station/ Switch Yard -.Li Iiouses. ,. 1 2 . . F -- - . | Cooling.towers L- , F 1'4 ..8 7 . .6 , . 12~ ~ ~ ~ ~ ~ ~ ~~~~~~~~~~~~~~~~~~~~1 .... ... .... ....1 gGeneratorHouse 15~~~~~~~~~~~~~~~~~~~ I ... . 1 2 3 4 F-- i 11~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ o~ ~ ~ ~ ~~~~~~~~~~~~~~o Figuie 1: SiteeneLocations 9~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~~~.. ....... I 2 3 ' . .~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~.. ...... ...... . . .~~~~~~~~~~~~~~~1 . .. . ... ..... o f | ~~~~~~~~~~~~~Officel ....... _.'.'. .. ........ . .. .. . ... , . . . .. . . . . . .... .. ... . ..... .. .............. ... ...... ..... ........ ....... ... ....... .... .......... .. ......... .............. .. . . ...... .. .. .. ..... . . . Figure 1: Site Location  2. Results 2.1 Noise The generator house has four generators but only one is operational. The generator is rated at 3.5 MW (rated down from 4.5 MW when new) and was working at full load. The Noise level measurements were done at point 1 -15. The results are shown in Table 1. Table 1: Noise Measurement Results Measurement Points \ 1 21 31 41 51 61 71 81 91 10 111 121 131 141 1 Noise in ecibels96 9492 92 94 94 96 96 86 82 72 84 82 7272 2.2 Air quality The air quality was measured at points 15 and 16 (Figure 1) and A - D (Figure 2). Results are shown in Table 2. Y Wind direction B 0.7m c 0.5 m Generator house 0.5 m A 0.5 m CGate Figure 2: Some Air Quality Measurement Points (not true to scale) 3  Table 2: Air Quality Measurement Results Temp 02 GO Go, NO