FEDERAL DEMOCRATIC REPUBLIC OF ETHIOPIA MINISTRY OF WATER RESOURCES ERER DAM & IRRIGATION DEVELOPMENT PROJECT Final Detail Design Report Annex H: Operation & Maintenance Manual May. 2009 CONCURT ENGINEERING AND CONSULTING ENTERPRISE P.L.C. (CECE) ENGINEERS HATER RESOURCES S AGRICULTURAL DEI El.OPMENT PLANNERS f'.OJIOS <.iiM AlMMS AII All A 141-251 II MJ9ZII FAX 2SMI-6M92-I5 I'.-mail CUOfiiK u r lln«ur( jrl <7*ATe/? In uxxticiiilinif »• ith C 'ufi.xuttifti; Eti^inefrinff Service (I. Tl))iExecutive Summary Volume I: Dam & Appurtenant Structure Annex A: Dam Design Annex B: Dam Appurtenant Structures Annex C: Geotechnical Study Annex D: Hydrology Volume II: Irrigation & Drainage Annex E: Irrigation & Drainage Design Annex F: Road Infrastructure Annex G: Project Control Centers Annex H: Operation & Maintenance Manual Volume III: Project Worth Analysise * Tabic of Content 1.0 Introduction1 2.0 Basic Features of the Works3 2.1 ReservoirJ -a 2.2 Earth fill Dam3 2.3 Bottom Outlet3 2.3.1 Intake tower3 2.3.2 Horizontal conduit3 2.3.3 Bottom outlet stilling basin (plunge type basin)4 2.4 Spillway4 3.0 Dam Instrumentation5 3.1 General5 3.2 Instrumentation Scheme6 _3.2.1 General Scheme6 3.2.2 Measurement of Pore Water Pressures6 _3.2.3 Measurement of Internal Movement7 _3.2.4 Measurement of Surface Movements7 3.3 Measurements of Rainfall8 3.4 Measurement of Reservoir Waler Level8 3.5 Measurement of Reservoir Sedimentation8 3.6 Water Demand and Regulation8 4.0 Surveillance of the Dam9 5.0 Normal Operation of the Dam or Reservoir10 5.1 General10 5.2 Condition of Initial Filling of the Reservoir10 5.3 Observation and Measurements during Initial Filling of the Reservoir11 5.4 Earthfill Dam Inspection and Maintenance13 5.5 Inspection and Maintenance of Structure and Electromechanical Equipment14 6.0 Collection Analysis and Interpretation of Data and Measurements17 6.1 General 6.2 Measurements and Records17 6.2.1 Rainfall 6.2.2 Reservoir Water Level17Erer Dam & Irrigation Project ZCECE & CES 1.0 Introduction This manual comprises the basic ideas and criteria which should be followed in operation, inspection and maintenance of Erer Earth Dam and Irrigation Project starting from the first phase of filling of the reservoir and its subsequent phase of regular operation. The personal responsible for dam operation, inspection and maintenance should have the necessary know-how and be familiar with design and construction consideration and aware of problems that may require special attention during operation and maintenance of the dam The objective of the operation of Erer Earth Dam and Irrigation Project is the timely delivery of the required quantity of water to the town and textile factory and other users This objective is achieved by the following activities • The preparation of reservoir operation planning. • Operation of water distribution according to the water supply demands. • Monitoring of the water distribution • Adjustment of the plan if required.. In any case, however, the duties and responsibilities of the operation, inspection and maintenance of the dam shall be given to a group of competent technicians, led by an engineer with experience in the field dealing with large hydraulic works and, in particular with earth fill dam This manual provides the most important information on the principle of the operation, inspection and maintenance. It is however recommended that the use of this manual refers for more detailed information should be in conjunction with the following Earth Erer Dam and Irrigation design project documents. Annex H: Erer/Operation and Maintenance /Final Detail Design Report /2009 1Ercr Dam & Irrigation Project ZCECE & CES • Finale Design report of Erer Earth Dam and Irrigation Designs project CECE, 2009 Tender Documents for the Erer Earth Dam and Irrigation construction Project. For future development work such as fishery etc in the body of the reservoir, knowledge of thermal regime is essential To monitor the water quality at different temperatures thereby facilitate condition for assessment of specific purpose, arrangements for measuring thermal regime should be thought of primarily. Annex H. Erer/Operation and Maintenance /Final Detail Design Report /2009 2Erer Dam & Irrigation Project ZCECE & CES «■ 2.0 Basic Features of the Works 2.1 Reservoir Maximum Design Flood Level Maximum Operating Level Live Storage Gross Storage Elevation of Dead Storage 1382.60 m 1379.0m 23 03Mn? 50.67Mm3 1369.85m Maximum Water Head above Stream bed 36.60m River bed level 1346.0 Minimum drain down level 1371.0 Earth fill Dam Crest Elevation Crest Width ( clear width) Crest Length Max. Dam Height above the River Bed Level Free Board Maximum Over flow depth Upstream face slope Downstream face slop 1384 0 9.0 1482.0m 36.60 2.0m 3.6 1; 3/1:3 5 1:2.5 2.3 Bottom Outlet 2.3.1 Intake tower Located at the upstream end of the bottom outlet with bed elevation 1366m(design elevation). The intake tower is provided and trash racks which will be operated from the top of the tower 1384.0m by means of mechanical devices 2.3.2 Horizontal conduit The conduit is made of rectangular shaped reinforced concrete (1.0m x 1.0m) structure having a thickness of 0 60m and 0.40 at top and bottom faces the length of the conduit is 123m. Construction joints and collars shall be provided in accordance with design recommendation and specification. Annex H: Erer/Operation and Maintenance /Final Detail Design Report /2009 3Ercr Dam & Irrigation Project /CECE & CES 2.3.3 Bottom outlet stilling basin (plunge type basin) The stilling basin has the following design parameters: Velocity (before jump) Outlet diameter (size) Length of basin Depth of basin 18.1 lm/sec 1.1m x 1.1m 8.6m 4.70m 2.4 Spillway Type of spillway Design flood Location dam Length of spillway crests Broad Crested 441 m3 /sec Left bank end of dam embankment 30 m. Level (elevation) Approach channel Weir Crest Stilling basin 1376.50 m 1379.0 m 1340.70m Depth of Broad crest Spillway weir 2.50 m The spillway will discharge out to the original course with some protection work of the dry stream channel. Spillway slab is made of slabs having laterally spaced joints at 10m interval with bitumen filled structural joints of 3 cm laterally. The provision of sub-surface drainage arrangement which is spaced at 20m interval. Annex H: Erer/Operation and Maintenance /Final Detail Design Report /2009 4Erer Dam & Irrigation Project ZCECE & CES 3.0 Dam Instrumentation 3.1 General A simple scheme has been followed for instrumentation of Erer dam so as to evaluate the performance of dam during its operation and to verify the design assumption. To observe the behavior of dam and its foundation during construction and operation of the reservoir, the instrumentation is done to measure: • Settlements and movements • Pore pressures • Seismicity a) Internal Movement The measurement of internal movement primarily consists of measurement of vertical displacement and relative horizontal movements caused by the low shearing strength and the long term creep of the foundation or embankment material. Various instruments, using different techniques, for measurement, like cross arm settlement system, base plate settlement system, inclinometer system with biaxial probe, digital inclinometer etc, are available for measuring vertical & lateral settlement of embankment and foundation b) External Movement External movement of the dam crest or the side slopes accompanies internal movement of embankment and/or foundation. External vertical and horizontal movements are measured on the surface of embankments through the use of level and position surveys of reference point. Reference points may be surface settlement points installed on the dam crest, slopes or toe of the embankment. Measurement of external movement of these surface settlement points is important for construction control as well as in monitoring the performance of the dam. Annex H: Erer/Operation and Maintenance /Final Detail Design Report /2009 5Erer Dam & Irrigation Project /CECE & CES <■ * c) Seismicity Surveillance of seismic environment of the project site needs special attention. Seismographs and accelerographs to record micro seismic activities and strong ground motion can be installed at Harar meteorological observatory No separate instrumentation is proposed at dam section to record seismic activities. Reservoir and tail water levels, wave height, evaporation and rainfall are some of the other parameters, which require to be separately monitored. 3.2 Instrumentation Scheme 3.2.1 General Scheme The general scheme of instrument in Erer Dam provides for measuring pore water pressures and internal movement at three cross-sections of dam embankment. The three cross-sections are located at distances 514m, 834m and 1266m respectively from left bank The installation of monitoring instruments shall be carried out with great care under the supervision /guidance of instrument manufactures. 3.2.2 Measurement of Pore Water Pressures Pore water pressures in dam and foundation are proposed to be measured by means of vibrating wire electrical piezometers. Vibrating wire piezometers work on measuring the change in natural frequency of a stretched wire fitted in the transducer. The water pressure existing at the point of piezometer tip is transmitted to the circular membrane. The deflection of membrane changes the tension of the wire, which in turn changes the resonant frequency of the wire. The change in resonant frequency of wire is read by means of a read out unit and is a measure of pressure change. It is proposed to install 23 Nos. vibrating wire piezometers in the dam foundation. Sixteen piezometers are installed in middle cross-sections at chainage514m and 834m Annex H: Erer/Operation and Maintenance /Final Detail Design Report /2009 6Erer Dam & Irrigation Project ZCECE & CES------------------------------------------- --------------------- << while 7 piezometers are installed at ch. 1366m on the right bank of the river at the irrigation outlet. The pore water pressures within dam embankment shall be measured by means of 27 Nos piezometers, 10 each at the middle sections and 7 at the section on the right bank at irrigation outlet The position of the three instrumented sections and the location of piezometers at these sections are shown in the relevant instrumentation drawings. (See Annex 2) 3.2.3 Measurement of Internal Movement It is proposed to use inclinometer system with biaxial probe for measurement of vertical and lateral displacement of dam embankment. A total of 4 inclinometers are proposed to be installed, along the dam axis at ch.514m and 834m. Internal horizontal movement of the embankment is proposed to be monitored by means of horizontal movement gauges, one each at the two instrumented sections in the river channel portion The position of inclinometers and horizontal movement gauges is shown on the drawings of dam instrumentation. 3.2.4 Measurement of Surface Movements Surface movement of dam embankment shall be monitored by means of a number of surface settlement points, installed at dam crest The surface settlement points shall be installed on upstream face of the dam only above MDDL. A surface settlement point shall be made of 150 mm long, 25 mm dia, steel rod having a cross mark engraved at the top. The settlement points on top of the parapet wall will be made of 25 mm dia, 150 mm long steel rod welded to a 225mm x 75 mm x 6 mm steel plate. The surface settlement points shall be installed on the slopes near the crest, at the berm levels and at the heel & toe of the dam at chainage 600m, 800m & 1000m respectively. Annex H Erer/Opcration and Maintenance /Final Detail Design Report /2009 7Erer Dam & Irrigation Project ZCECE & CES The settlement shall be monitored using a Total Station at regular intervals. The first reading acts as a reference and the subsequent readings give the settlement of the surface with respect to the time. 3.3 Measurements of Rainfall Non recording rain gauge has been installed in the vicinity of the Dam site at the Harar town for the measurements of daily rainfall. In order to obtain continuous data it is advisable to install self -recording rain gauge. 3.4 Measurement of Reservoir Water Level The Reservoir Water Levels will be measured by means of staff gauges installed on the walls of the intake tower and on the banks of the reservoir where observation and maintenance could be useful in observing the flood magnitude. 3.5 Measurement of Reservoir Sedimentation Reservoir sedimentation can be measured using sounding line capable of measuring the depth of water in the reservoir, so as to be able to obtain the elevation reached by the sediment deposition Sampling of the water turbidity in the reservoir shall be carried out by conventional hydrometric methods. 3.6 Water Demand and Regulation The quantity of water to be released into the water supply system can be measured by installing water meters. Downstream release could also be measured by the same device. For future information conventional reservoir operation planning is included in annex . 1 Annex H. Erer/Operation and Maintenance /Final Detail Design Report /2009Erer Dam & Irrigation Project ZCECE & CES 4.0 Surveillance of the Dam In the regular operation of reservoir constant surveillance of the dam must be carried our using appropriate personnel, necessary equipment and facilities. The Surveillance of the dam shall be ensured by a responsible technician who will be in charge of the supervision crew. The crew consist of crew leader (qualified technician), assistant technicians, skilled laborers, guard officer and assistants. The technician, the guard officer, and their assistants, if any shall reside in the immediate vicinity of the dam at the dam project control center (Pcc), in a well furnished living quarter and nearby office rooms The office (Pcc) should have telephone and radio communication facility or either of them to be in close contact with local and regional office which would be responsible for operation and maintenance works of the dam The regional office shall appoint an engineer or an assistant engineer in charge of the operation, inspection and maintenance of the dam. He will probably reside in the regional capital, but shall make regular inspection of the dam according to defined scheduled of inspection and when the need each period. The inspection by the engineer or assistant engineer shall be at least four times a year during the regular operation of the reservoir. Inspection should be scheduled during period of high and low water to observe conditions peculiar to each period. Special inspection should be scheduled when there is reason to believe that significant damage has occurred or may develop, such as after any unusual occurrence, like earth quakes, sustained periods of heavy rains, heavy flood events etc. During the initial filling of the reservoir inspection shall be conducted daily or in days time so that utmost information could be acquired. Roads and pathways which are in , good condition shall be ensured between the living quarter office rooms and different parts of the dam, such as intake tower, crest of the dam, downstream berms, spillway, outlet part of conduit. Annex H: Erer/Operation and Maintenance /Final Detail Design Report /2009 9Erer Dam & Irrigation Project /CECE & CES 5. 0 Normal Operation of the Dam or Reservoir 5.1 General The normal operation of the reservoir will start when the correct functioning of the dam and appurtenant works has been checked and a favorable result obtained. During the normal operation of the reservoir, surveillance of the dam shall always be ensured according to the procedures given in chapter 4. In general all components of the dam and the reservoir should be inspected with the following objectives. • To verify the safety of the components and facilities • To disclose condition which might cause disruption or failure of operation and consequently losses of human life and property. • To determine the adequacy of components and facilities to serve the purpose for which they where designed and are used. • To note the extent of deterioration as basis for planning maintenance and rehabilitation works. 5.2 Condition of Initial Filling of the Reservoir As soon as the construction of the dam has been completed and operational tests of the different electro-mechanical equipment for the bottom outlet and intake works deemed very satisfactory, the first phase of reservoir filling can be commenced. In this very delicate phase, extra precaution and procedures for operation should be adopted because un predictable situations may occur The purpose of this first phase tight inspection is that of checking the response of the dam and foundation under the action of the storage. Under particularly close surveillance frequent measurement will be taken using control instruments. Structures are very frequently and attentively supervised to note any change in their behaviors The procedures of reservoir filling shall be in the following manner. Annex H: Ercr/Operation and Maintenance /Final Detail Design Report /2009 10Ercr Dam & Irrigation Project ZCECE & CES After conducting the necessary operational tests of gates valves and related parts and confirming that their operation under the given condition is satisfactory, the filling of the reservoir can be started by closing the bottom outlet gates provided that the embankment construction of dam has been completed (or is very near to completion). The discharge, of the stream during the months of March to May constitutes the major portion of the annual flow and most of the concentrated flow to the reservoir will be expected within those months. Bearing in mind that the total reservoir capacity and the statistical values (synthetic and measured ones) of the annual stream flow, it is probable that the initial filling of the reservoir will take place in a single hydrological year. But this may arise the need to check the behavior of the dam structures in condition of gradual filling of the reservoir, alternated possible by phase of partial emptying. In case filling of the reservoir in phase is imminent the duration of each phase from beginning to end should be established. The filling of the reservoir shall be carried out only after a written order is given by the engineer who is in charge of operation, inspection and maintenance. The flow to the reservoir will be stored until the end of the first filling phase. In the process of filling of the reservoir be made in line with the conation stated in the following pages. 5.3 Observation and Measurements during Initial Filling of the Reservoir During the initial filling of the reservoir the earth fill dam embankment shall be carefully inspected every day for the purpose of finding places of development of unfourable conditions The downstream slope shall be inspected for indications of cracks, slides, sloughs, subsidence, and impairment of slope protection, springs, seepage or boggy areas caused by seepage from the reservoir. The upstream slope of the embankment shall be inspected for adequate protection of the embankment. Extensive wave action, poor quality rip-rap, poor graduation, large debris or rip-rap movement can contribute to conditions of inadequate protection of the embankment. Annex H: Erer/Operation and Maintenance /Final Detail Design Report /2009 11Ercr Dam & Irrigation Project /CECE & CES * Prior to the start of the initial filling of the reservoir the initial reference readings of all the dam control instruments shall be made. The readings of all the control instruments of the dam shall be taken with the procedures and precaution indicated in the manual Through out the initial filling of the reservoir the following measurements shall be taken using the control instruments. Rainfall------------------------------- ----- every morning Reservoir water level----------------------------------- every morning Pore water pressure with stand pipe Piezometers-------------------------------------------- — every two weeks Vertical and horizontal displacements On the crest and down stream berms----------------------- every month In addition to the measurements mentioned earlier the quantity of water released into the Irrigation water supply system and downstream for the purpose of satisfying the downstream demand shall be measured and registered every day. The result of all the measurement taken shall be accurately registered every day in appropriate register and elaborated in the form of diagrams or tables, as indicated in the following chapter (6). All the results of the observation made and the measurements taken shall be kept at the disposal of personnel in charge of the dam operation, inspection and maintenance. At the end of each month, the technician shall transmit one copy of all the observations made and measurements taken during the month to the engineer in charge of the dam operation, inspection and maintenance probably residing in the regional capital. Annex H. Erer/Operation and Maintenance /Final Detail Design Report /2009 12Ercr Dam &. Irrigation Project /CECE & CES The Technician shall notify all unusual or abnormal condition that may adversely affect the operation or safety of the dam to the engineer in charge of operation, inspection and maintenance. 5.4 Earthfill Dam Inspection and Maintenance The earthfill dam embankment shall be inspected at regular interval (every 15 days during the first year of normal operation of the reservoir and once every month thereafter) for locating places with defect development. The downstream and upstream slope shall be carefully inspected as stated in para 5.3 for adequate protection of the embankment The maintenance of the earthfill embankment consists of removing debris from the upstream face of the dam, replacing inadequate rip rap, repairing eroded material, proper grading of access roads, controlling understandable vegetation and cattle, properly maintaining monitoring devices within the embankment and adjacent area. In addition to the regular inspection and maintenance, periodically in depth inspection should be made at least every 3 years. A qualified team, headed by an engineer preferably not directly involved in the operation and maintenance of the dam should carry out theses inspection The engineer should be accompanied by operation personal familiar with all facets of the operation and maintenance of the dam. Inspection should be scheduled, if possible during alternate periods of high and low water, to observe conditions unique to situations Special inspections should also be conducted after all unusual occurrences that may adversely affect the safety of the dam, as specified in Chapter 4 Undesirable situations noted during inspection shall be identified and documented in a detailed report to be submitted, promptly to the engineer, responsible for the dam operation, inspection and maintenance, so that the necessary precautionary measures can be taken immediately. Annex H. Erer/Operation and Maintenance /Final Detail Design Report /2009 13Ercr Dam & Irrigation Project ZCECE & CES During normal operation of the reservoir, the following measurement shall be taken using the dam control in instrumentation. • Rainfall • Reservoir level Pore water pressure • With stand pipe piezometers.... • Displacements on the crest And downstream berms • Water released into water Supply system • Water released for downstream Requirements Every morning Every morning .Every month Every six month Every day during operation time At every operation The result of all the measurements taken shall be accurately registered every day in special registers and elaborated in the form of diagrams on tables as indicated in chapter 6. All the result of observation made the measurements taken shall be kept at disposal of personnel in charge of the dam operation, inspection and maintenance. Once every there months, the technician shall transmit a copy of all the observations made and measurements taken during the month to the engineer in charge of operation, inspection and maintenance. 1 he technical shall immediately notify al) unusual or abnormal conditions that may adversely affect the operation or safety of the dam to the engineer in charge of operation inspection and maintenance 5.5 Inspection and Maintenance of Structure and Electromechanical Equipment 1'he bottom outlet, intake tower and spillway are vital features for the performance of the dam Regularly scheduled inspections of these structures shall be carried out every six months to observe external and internal metal and concrete surface for abnormal condition Annex 11 Erer/Operation and Maintenance /Final Detail Design Report /2009 14Erer Dam & Irrigation Project ZCECE & CES Deterioration of protective coatings on metal works will reduce the actual life of pipes and equipment substantially Inspection of intake structures, trash racks, conduits, gate, upstream faces and stilling basin concrete surfaces below the tail water surface are normally not feasible during regularly scheduled inspections. Special inspections of these features should be performed by dewatering the structure or when operating conditions permit, at intervals of 2-3 years Regularly scheduled inspections of the electrometrical equipment will be carried out according to manufacturer’s instruction. Gates, Valves, controls and auxiliary equipment shall be operated and observed during these inspections if possible. Electromechanical equipment shall be observed. Erosion of slopes within the spillway area shall be controlled and proper drainage shall be ensured. The bottom outlet shall be used for emptying the reservoir and releasing controlled quantities of water downstream. This operation shall be made trough intake tower. The intake tower is provided with opening having a width of 2.9m x 3.82m and its sill elevation at 1366m and top of tower at elevation 1384 Om. The opening is provided with vertical grooves for installation of trash racks and stop logs. The stoplogs shall be initially dropped up to final elevation and there after shall be initially dropped upto finale elevation and level of the reservoir with respect to clearly defined bench mark The idea behind this is to abstract clear water from the top most part of water. After a series of decrease in water level and then increase will again entail the dropping of stoplogs to specified elevation so that the upper layer of stored water could easily be directed to intake tower. Every six months the actual elevation of the sediment deposit shall be checked in order to carry out the operation smoothly and with full information. The bottom outlet gates shall be operated and maintained in the best conditions, according to the manufacturer’s instruction. Annex H. Erer/Operation and Maintenance /Final Detail Design Report /2009 15Ercr Dam & Irrigation Project /CECE & CES Deterioration of protective coatings on metal works will reduce the actual life of pipes and equipment substantially. Inspection of intake structures, trash racks, conduits, gate, upstream faces and stilling basin concrete surfaces below the tail water surface are normally not feasible during regularly scheduled inspections. Special inspections of these features should be performed by dewatering the structure or when operating conditions permit, at intervals of 2-3 years Regularly scheduled inspections of the electrometrical equipment will be carried out according to manufacturer’s instruction. Gates, Valves, controls and auxiliary equipment shall be operated and observed during these inspections if possible. Electromechanical equipment shall be observed. Erosion of slopes within the spillway area shall be controlled and proper drainage shall be ensured. The bottom outlet shall be used for emptying the reservoir and releasing controlled quantities of water downstream. This operation shall be made trough intake tower. The intake tower is provided with opening having a width of 2.9m x 3.82m and its sill elevation at 1366m and top of tower at elevation 1384.0m. The opening is provided with vertical grooves for installation of trash racks and stop logs. The stoplogs shall be initially dropped up to final elevation and there after shall be initially dropped upto finale elevation and level of the reservoir with respect to clearly defined bench mark. The idea behind this is to abstract clear water from the top most part of water. After a series of decrease in water level and then increase will again entail the dropping of stoplogs to specified elevation so that the upper layer of stored water could easily be directed to intake tower Every six months the actual elevation of the sediment deposit shall be checked in order to carry out the operation smoothly and with full information. The bottom outlet gates shall be operated and maintained in the best conditions, according to the manufacturer’s instruction Annex H: Erer/Operation and Maintenance /Final Detail Design Report /2009 15Erer Dam & Irrigation Project /CECE & CES The flow regulation will be accomplished by acting on one, two or there regulating values, according to the requirements. Annex H: Erer/Operation and Maintenance /Final Detail Design Report /2009 16Erer Dam & Irrigation Project ZCECE & CES 6.0 Collection Analysis and Interpretation of Data and Measurements 6.1 General The inspection of a dam such as Erer Earth Dam and Irrigation Development Project requires the installation of a certain number of instruments. Their purpose is that of observing the behaviors of the structure through out its life. It is important to point out that the readings of the instruments must always be considered in a global context, taking into account all the surrounding condition affecting the reading itself and depending on the type of measurement Maximum care should be taken in carrying out the measurements and maintenance of instruments in such away as to guarantee their maximum efficiency and thus, reliability. This chapter gives some simple guidelines for the correct reading of the instrumentation and its correct interpretation It is absolutely necessary that all the readings be carried out by very skilled operators with the maximum care and all the figures plotted and tabulated using appropriate graphs and tables. 6.2 Measurements and Records 6.2.1 Rainfall Rainfall will be measured in millimeters by a raingage of recording or non recording type of both at daily intervals, recorded on a special register, and plotted in histogram form in relation to time. 6.2.2 Reservoir Water Level. Reservoir water level will be measured at assigned intervals by means of staff gauges and relevant values recorded on a special register and plotted in relation to time. 6.2.3 Pore water pressure The pore water pressure in the dam embankment and in the foundation will be measured at assigned intervals by means of stand -pipe piezometers. Annex H: Erer/Operation and Maintenance /Final Detail Design Report /2009 17Ercr Dam & Irrigation Project ZCECE & CES________ ______________________ It should be noted that, most probably Pizometers embedded in the dam body will take a long time to perceive the variation of pressure due to the water storage because of the low permeability of the core material, while on the other hand, the piezometer installed in the pervious foundation strata beneath the dam will give a very rapid response to the variation of the water level in the reservoir. The values of the pore water pressure obtained by the instrument will be recorded on a special register and plotted against time on graph including the water level fluctuations in the reservoir. 6.2.4 Vertical and Horizontal Displacements Measurements will be carried out at assigned intervals on the dam crest and downstream berms using monuments of type stated in annex 2 and as described in 3.1. They will give an indication of the vertical and horizontal displacement of a number of check points and will be plotted in relation to water levels in the reservoir. 6.2.5 Water Released into Water Supply System Measurement will be carried at assigned intervals using water meters instated at convenient points of the water supply and downstream release pipes. The amount of the water released and in both cases will be recorded on special registers 6.3 General Recommendation Operation and maintenance of the dam control instrumentation should be carried out according to the manufacturer’s instruction. The instrumentation should be read at regular intervals, as suggested in this manual and when deemed necessary because of the abnormal values the frequency will be increased. The technicians responsible for the readings should be highly competent, and should know all the necessary expedients to carry out the reading properly. The reading should be made at least three times, always, resetting the instrument. Annex H. Erer/Operation and Maintenance /Final Detail Design Report /2009 18Ercr Dam & Irrigation Project /CECE & CES Maximum care should be taken in handling the instrumentation so as not to damage it. Periodical and occasional maintenance should be foreseen to keep the instrumentation in good conditions Each reading should be interpreted with the physical conditions affecting it, i.e water level, rainfall; etc .All data collected should be filled. All the readings will be interpreted, in any cause, by an experienced engineer considering the whole structure and its overall behavior in respect of factors involved in each phenomenon. Control of grasses and weeds on the dam body and slope is necessary to discourage development of pests, shrubs or trees which would damage the dam body and to encourage the growth of soil binding grass (downstream face of the slope) Drains have to be cleaned after due inspection at short distance from the downstream toe of the dam should be thought of for the purpose of measuring of the quantity of water seeping out. Equipment or Machinery Required for Routine Maintenance works • Mostly maintenance is carried out by hand as per recommendation of inspection group. • Depending on the type of maintenance machinery may be acquired on rental basis or by other arrangement such as earth moving machinery • At the site shovels, hoes, etc shall be at the disposal of surveillance group. • Anti- rust and protective paints and brushes shall be available at the site. • Appropriate stock of spare parts for the purpose shall be allocated right from the very beginning. • Motor vehicle capable of accommodating operators mechanics, technician etc. with their proper maintenance equipment could be preferable to station at the site, If motor vehicle is accessible, then the necessary spare parts (tires, inner tubes, spare Annex H: Erer/Operation and Maintenance /Final Detail Design Report /2009 19Erer Dam & Irrigation Project ZCECE & CES parts and fuel reserves), so as to rely at all times, on the efficiency of their own vehicle , should be made available. Method of Maintenance works For carrying out restoration work Only materials, processes and installation complying with the technical specifications attached to the final design of the dam and adopted for its construction shall be used. The complete drawing ( as built- drawing) shall be available for operation and maintenance crew Annex H: Erer/Operation and Maintenance /Final Detail Design Report /2009 20ANNEX - 1 List of Tables and FiguresErer Dam & Irrigation Project /CECE & CES Daily Records of Rainfall, Water Level and Water Released Into Water Supply system and Downstream DATE RAINFALL (mm) RESERVOIR WATER LEVEL (m) WTER SUPPLY (L/ sec) VALVES REMARK Vi v2 v3 TABLE 1.3 I In the remarks column the names of responsible persons should be written unequivocally. Annex H: Erer/Opcration and Maintenance /Final Detail Design Report /2009 22I Erer Dam & Irrigation Project ZCECE & CES RECORD OF PORE WATER PRESSURE Annex H: Erer/Operation and Maintenance /Final Detail Design Report /2009 235 I Ercr Dam & Irrigation Project ZCECE & CES RECORDS OF VERTICAL AND HORIZONTAL DISPLACEMENTS DATE VERTICAL DISPLACEMENT} BENCH MARKS) HORIZONTAL DISPLACEMENT (BENCH MARKS) REMARK B.M B.M B.M B.M B.M B.M B.M TABLE 1 .5 Annex H; Erer/Ope«, „ o --------- 24ANNEX -2 DAM INSTRUMENTAION AND DETAIL DESIGN WORKSNOTES MWLT1383 6 FRL 1379 MDDLv1371 ▼1363-------------- U3690 1350 0 !- Acceptable foundation grade Silty gay Graval 0.6m thick plastic Concrete diaphragm wall 1- THE DRAWING SHOWS MONITORING INSTRUMENTS INSTALLED AT SECTION 1 - 1. ALL OTHER DETAILS SHOWN IN THE DRAWING INDICATIVE ONLY 2- THE LEADS COMING FROM SENSORS SHOULD BE OF SUFFICIENT LENGTH TO BE JOINED TO PROPOSED RECORDING STATION. 3- TRENCHES FOR INSTRUMENT LEADS SHALL NOT BE DUG ACROSS THE CORE. LEADS MAY BE CARRIED TO ABUTMENTS NEARLY PARALLEL TO DAM AXIS AND THEN CARRIED TO MONITORING POINT THROUGH TRENCHES MADE FOR THIS PURPOSE. 4- FOR THE INSTRUMENTS INSTALLATION DETAILS, REFER SHEET 2/2 5- ELEVATIONS ARE IN METERS AND ALL OTHER DIMENSIONS ARE MILLMETRES UNLESS SPECIFIED OTHERWISE. SECTION AT CHAINAGE 540m AND 834m LEGEND PIPES FOR DEFLECTION AND SETTLEMENT MEASURING INSTRUMENTS HORIZONTAL MOVEMENT GAUGE EMBANKEMENT VW PIEZOMETER FOUNDATION VN PIEZOMETER ABSTRACT OF INSTRUMENTS PROPOSED AT SECTION RD 500 & 800 MONITORING POINT PIEZOMETERS Q < p- 8 u. ELEVATION (m) IN CORE IN FILTER IN SHELL TOTAL DEFLECTION & SETTLEMENT DEVICES HORIZONTAL MOVEMENT GAUGE 1325 1 1 1330 2 2 1338 2 1 3 1343 1 1 2 TOT/U. IN FDN 6 2 8 1351 2 1 3 1367 3 1 1 5 1 1 1376 2 1 1 4 TOT Al IN EMB 2 3 12 1 7 BY AMENGKTE EMBANKMENTEmbankment level JKMENT PIEZOMETER SHALL BE INSTALLED IOLE OF 150 MM DIAMETER. COARSE CLEAN :R MATERIAL SHALL BE PLACED AT THE BASE ZOMETER TIP THE PIEZOMETER TIP. SOAKED FOR AT LEAST 24 HOURS, SHALL BE INSERTED ;EHOLE. FINE SAND SHALL BE FURTHER POURED TIP IS COVERED BY AT LEAST 150 MM. FHE FORM OF BENTONITE GRANULES SHALL BE Mound) PREVENT ENTRY OF GROUT IN THE SAND FILTER, during c lottom al main trencti :1 mixture of Band and co mo nt —OnN hdc min 150 0 able atorated graded sand lezomoter able VIBRATING WIRE ELECTRICAL PIEZOMETER INSTALLATION DETAILS IN FOUNDATION Scale 1:10 :ert engineering ano consulting enterprise IN ASSOCIATION WITH JLT1NG ENGINEERING SERVICE (INDIA ) PVT. LTD IRRIGATION PROJECT DETAIL DESIGN DAM INSTRUMENTATION or. DATE 2004 BY. TOMAS G. scale AS SHORAN BY: P.DATTE REVISION NR OETAJL DY: A MENGISTE DRAWNC NR No OAMO9
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