Technical Approach and Methodology

Transcription

1 1 Dam Rehabilitation & Improvement Project (DRIP), India Technical Approach and Methodology relative to Section of Design Flood Review of TOR Making an integral part of Egis Eau Tender Technical Proposal submitted for the DRIP Preface: The Technical Approach was authored on behalf Egis Eau Co., France, and it was intended to make a part of consolidated technical proposal for Dam Rehabilitation & Improvement Project (DRIP), India. The Technical Approach was restricted to Project Terms of Reference section defined as Design Flood Review. The following engineering realms were discussed therein: Hydrological history considerations and reestablishment of design inputs for dams rehabilitation, The reservoirs operation modeling whilst having current the increased flood flows, Scenarios of dams rehabilitation design, The means for upgrading of existing structures and hydro mechanical equipment, Emergency programs for dams break events, Software emulated dams break process. The foregoing methodology was associated in all according to the current international standards and codes of practice. April, 2013 Zika Smiljkovic

2 2 Understanding of DRIP TOR General Project Data Management and Engineering CWC Central Water Commission DRIP Dam Rehabilitation & Improvement Project SCOPE of PROJECT I Dams and Associated Structures Rehabilitation II Dam safety Institutional Strengthening III Project Management CPMU Central Project Management Unit Consulting Firm Expertise in Consultancy Management and Engineering at CPMU and the State Sub Units (SPMU) B. Project Management C. Design Flood Review Methodology B1. PLANNING É Project planning template and optimum implementation schedule. B2. PROCUREMENT É Procurement management: schedules, tender documents, cost estimates, tender procedures, contracts award. B3. Financial MANAGEMENT É Annual budget plans; É Interim unaudited reports for WB; É Compilation of audited reports to WB ending a financial year. B4. Project MONITORING É Compilation of annual and quarterly progress reports, including as build vs planned outcomes. B5. Documents MANAGEMENT É Filing System; É Proactive and on demand response system; É Compilation of final Project Rehabilitation Reports. C1. EVALUATION OF DESIGN FLOOD REVIEW STUDIES É Evaluation of design review studies prepared by Central Water Commission; É Evolving improved techniques for flood analysis. C2. OPTIONS TO COPE WITH INCREASED FLOOD DESIGN É Review of the rehabilitation design relative to hydrological re assessments, then the capacities of spillways and outlets; É Review of energy dissipation organs; É Routine trials for identification of appropriate reservoir levels with simultaneous use of water for water supply and hydropower. É Review of dam break analysis and inundation consequences in case of unforeseen floods. D1. SEISMIC DESIGN PARAMETERS É Review of design earthquake design parameters; É Review of seismic structural analysis and aseismic designs. D2. REVIEW OF STRUCTURAL SAFETY É Review of structural designs of remodeled dams aiming to receive higher floods. É Review of water tightness capacity of dams É Review of originally designed or rehabilitated dams foundation conditions, including their geotechnical conditions, and the capacity of sealing measures. D. Design Review Methodology D3. REVIEW of HYDROMECHANICAL EQUIPMENT É Review of Hydromechanical equipment rehabilitation design or where necessitated, the design of new equipment for increased reservoir levels. D4. REVIEW of DAMS INSTRUMENTATION É Review of original dams monitoring instrumentation; É Review of rehabilitated dams monitoring design, including the instrumentation, data logging, and the appropriate software for stability limit states ridings. D5. OVERALL DAMS REHABILITATION DESIGNS REVIEW É Review of survey data on seepage water through dams, geodynamic and erosive process of the upstream and downstream slopes, time related settlements of dams, propagation of cracks and thenceforth; É Review of rehabilitation designs of dams, dams abutments and reservoir slopes. D6. DESILTATION AND ENVIRONMENTAL EXPERTISE É Detail review of desiltations designs (where applied) and rendering guidance to the project authorities in environmentally sound implementations. Understanding of Project Scope The Project extends to 4 states of India: Kerala, Madhya, Pradesh and Orissa. Few more states may join DRIP at a later stage. A conclusion was derived from TOR that the Project is dealing with the flood control and/or water supply dams. There, the spillways, shoots, stilling basins, bottom outlets, the installed hydromechanical equipment inclusive, were construed to be the dam appurtenances. Hence, the water supply conveyors(if any) fed by dam ponds, then the appurtenant pumping stations, valves and water hammer limitation facilities, were presumed to be out of the DRIP scope. If the hydroelectric dams were included in DRIP package too, then it is to note that power conveyors, the regime of turbine flows, then the plants operation regimes serving base or pick on electricity demands, can be of the effect to ponds management updating, the remodeling of dams and rehabilitation of spillways and outlets. Assigning the term Appurtenances to headrace system, surge thanks, power houses, and the like, in this case should be discussed during Tender clarification phase. The same applies to rehabilitation of power generating equipment, the automation and control systems then of transmission lines (if any). E. Consultancy Supervision of Works Quality & Safety F. Dams Safety Institutional Strengthening E1. PERIODICAL SITE INSPECTION É Minimum one visit quarterly aiming to check the construction management expertise. E2. ASSESSING SUPERVISORY SYSTEM É Occasional assessment of supervisory mechanisms established by State Project Management Units for particular Dam Projects. E3. ASSESSING QUALITY CONTROL SYSTEM É Occasional assessment of quality control mechanisms established by State Project Management Units for particular Dam Projects. E4. ASSESSING of ESMF Compliances É Assessment of Environmental and social Management Framework compliances of State Implementing Agencies whilst their preparation of environmental management plans. F1. UPGRADING OF INSTITUTIONAL DEVELOPMENT EXPERTISE É Training of SPMU employees including procurement of works, financial and environmental management, modern practices in dams engineering, uptodate construction technologies, risks management, the software serving dams operation control, and the like. F2. FORMULATION OF NEW GUIDELINES FOR DAMS DESIGN AND SAFETY É Including overall scale of Dam Engineering, beginning of hydrological inputs, the reservoir routing, the flood water evacuation, until the risk analysis of dams. F3. DESIGN REVIEW MANUAL É Hydraulic safety, structural safety and rehabilitation design for the types of the existing dams. F4. DEVELOPMENT OF IMPLEMENTATION OF DHARMA É Development of balance modules of Dam Health and Rehabilitation Monitoring Application. F5. IDENTIFICATION OF UPTODATE DESIGN SOFTWARE É Advise on suitable software for hydrological, hydraulic, structural analyses of dams, as well as for dam break analysis. F6. ISO 901 Certification for CDSO and ISO Advisor É Facilitation of all activities relative to ISO 901 certification by Dam safety Organization Dam safety Commission. F7. DAM SAFETY trainings É Facilitating identification of training requirements for application of modern tools/prices relative to operation, maintenance and rehabilitation of dams. F8. IDENTIFICATION OF DAMS DESIGN SOFTWARE É Identification of appropriate software for hydrological, hydraulic and structural analysis; É Guidance to software implementation. F9. DEVELOPMENT OF IN HOUSE EXPERTISE É Identification of thrust areas of In House expertise and the related requirements for LAB facilities, hardware, software, trainings and the like.

3 3 Technical Approach and Methodology relative to Section of Design Flood Review of TOR Collection of the complete history of hydrological parameters of a watershed trending to a dam site shall be the first step of design flood review. The preconstruction collections then those being logged during dam operation span will have to be digitally filed and analyzed. The gauging stations such as those of pluvial ones, the limnigrphs or staff gauges covering the overall pre and after construction history of a particular dam should serve as a key sources for dams rehabilitation process. The recorded daily river discharges in conjunction with those of rainfall intensity are amongst others the basic inputs for an updated hydrological study supporting rehabilitation process. Establishment of mean discharge for a particular day of the hydrological history, then the particular mean weekly, monthly and yearly discharges for a year cycle, would serve as inception parameters. With reference to the watershed behaviour, these should be all the time correlated with as recorded areal hyetographs. The evaluation of the foregoing data should result to: (i) mean multiyear distribution of rainfall load during a year cycle, and (ii) mean multiyear distribution of river discharges for the same cycle. Further analyses of hydrological data will have to conclude the updated multiyear flow duration curve pertinent to a particular dam site. There, particular attention shall be paid to River discharges losses (if any) in case of faulted limestone dissolution forming karst. Here, the integral of the hydrological evaluations should result to: (i) mean MY weekly discharges (ii) mean MY monthly discharges, (iii) mean MY annual discharges, and (iv) mean MY percentage exceedence chart, alias flow duration curve, incremented at a minimum of 5%. For the purpose of the rehabilitation design, all the referenced outcomes should be digitally available too. The base flow as well as the safety flow for a specific dam site should be here reevaluated as well, the later one being under the effects of the currently applicable local regulatory acts. Whilst the probability analysis, the flood peak discharges and the appropriate flood volumes, should be evaluated for several return periods which are meritorious for setting the dam design criteria. Those being but not limited to: flood return periods of 50 Yr, 100Yr, 1000Yr, 2000Yr, 5000Yr, and Yr. The Probable Maximum Flood is the ending data which should be appraised at this point of dams rehabilitation process. The updated hydrological inputs discussed here before should be assigned the appropriate statistical error, contingent to the confidentiality of the source records and the methodology adopted for their evaluations. There, only the values inclining to conservative margin shall be adopted for dam s rehabilitation design inputs. The proper time related location of the updated hydrological inputs, is vital in view of taking into account the projection of the potential effects of climate changes governing in the areas. Hence, a consistent chart of mean annual discharges, time versus discharge, shall be graphed and the appropriate trend line extended to minimum 30 years beyond the time of rehabilitation shall be deduced there from. It will be then up to the engineering judgment, wisdom and far sighting, to locate the time section of the future operation lifespan at which the appropriate hydrological inputs shall be declared as climate changes affected. Hence, the appraised parameters are to be the basic criteria for reevaluating of dams capacity and safety. Here, a locally experienced hydrologist of CPMY or SPMY, who is fully aware of specific watershed hydrological fluctuations, should be delegated as a member of Consultant s experts team on an ad hock basis.

4 4 Comprehensive Terms of References having addressed-in the foregoing hydrological discussion should precede the preliminaries and main course of updated hydrological study preparation. At the point of dams rehabilitation process when the updated hydrological study was concluded, it is of paramount importance to collate the dams design criteria then derived, with those being prescribed at the time of original design of particular dam. The statement of their potential inconsistence shall be directive to hydraulic and structural redesigns of a particular dam. The reservoir operations modeling via flood routing analyses shall characterize the flood passage wave through a system. To this effect, the required dam outflow hydrograph shall be obtained once the River inflow hydrograph, the operation level of the reservoir and the flood storage volume of the reservoir were counted in. Whilst the inflow hydrograph will come as the outcome of hydrological inputs discussed herein, the outflow hydrograph remains the entire time contingent on the capacities of the dam outlets and spillways. Here, it was presumed the continuous monitoring of a dam outflows and reservoir levels had been either automatically or dam operators kept in the time of a dam operation. The outputs/logbooks backed there on, shall be essential for updating of reservoirs operation modeling. The reservoir modeling, concretely its storage volume shall be affected by the accumulated sediment yields too. Thus, the seismic reflection survey or bathymetric measurements of the dams reservoir should take precedence to modeling exercise. It is expected that two potential scenarios could appear after the reservoir modeling analyses has been updated: (i)the reservoir operation and flood levels are within the originally designed margins, in which case the rehabilitation process shall be confined solely to the physical treatment of the dams and associated structures aiming to lengthen their operational longevity, and (ii) the flood volume is increased and the consequent flood level was suffering upraising due to larger hydrological amplitudes, in the event of which the spillways capacity should be upgraded and the dams crest be remodeled such that to retain the required freeboard safety. Some other scenarios such as the increase the outlets capacity, construction of upstream flood control dams or construction of additional waterways inside the dam abutments might be implementable to the later case too, but to a rare extent. Hence, the latter, apart from the physical rectification it can be aligned with reconstruction activities too. Here, each dam and its components shall be considered on its own merits. Under the circumstances where the descending of spillways crests and rectification of the hydraulic conduits and thus the reduction of hydraulic losses have been proved feasible, the hydraulic outputs of the water release organs can be enhanced and the dam safety increased. As for structural aspects, both the engineered structures and those of geo-structural origin should be comprehensively considered aiming to augment the physical and mechanical sustainability of concrete structures, the geotechnical structures such as the abutments and the foundations, then the rockfill embankments.

5 5 To the foregoing effects, the following upgrading should be amongst others considered during the design stage of dams rehabilitation where/if applicable: (i) Cementitious injections of gravity dams whereby the strength of concrete matrix shall be upgraded, allowing thus potentials for remodeling of dam crest; (ii) Use of silica fume concrete for rectification of spillways, shuts and stilling basins; (iii) Fiber reinforced concrete in conjunction with bolting, for underground dam outlets; (iv) Reconstruction of rip-rap lining for rockfill dams, minimizing thus the effects of potential overtopping; (v) Hydraulically operated gates, wherever applicable; (vi) Automation of reservoir level monitoring system. The foregoing upgrading should be preceded by comprehensive hydraulic analyses of the water tract of Stream Inflow Reservoir Retention Dam Outlets, as well as by compound structural modeling of the system dam dam abutments/foundations. The Hydrologic Engineering Center (HEC) software package applicable to reservoir system analysis can be inter alia a useful tool for reservoir dam hydraulic interaction. Dams Break Events are usually aligned with catastrophic circumstances occurring during the dams lifespan, which usually are not a part of standard design criteria for dams engineering. They might be the cases of simultaneous propagation of unforeseen floods and maximum probable earthquakes, then unforeseen sliding of the reservoir slopes, and the like. A comprehensive rehabilitation program should reduce the consequences of those events to a minimum. The appropriate preparatory measures shall be an integral part of the operation and maintenance manuals of dams. In order to avoid or to foresee in due time the potential catastrophic events, the automation of reservoir monitoring then that of dams monitoring, both associated with comprehensive emergency program for downstream settlements, shall be the major section of O/M manuals. Here, the appropriate river training programs should be also used for simulation of the downstream flood wave propagation. Dam Break analysis shall be examined via analytical and numerical modeling of dam sustainability under prospective scenarios of its overtopping and the consequential erosion effects. A sensitivity analysis of overtopping depths then potential mechanisms of dam failure and progressive collapsing caused thereby shall be analyzed in depth via the foregoing models. The software packages, such as PLAXIS, ANSYS, then PHASE, can be beneficially supportable to Dam Break investigations. Z. Smiljkovic