Project Rehabilitation Report of Kabini Dam Project Rehabilitation Report of Kabini Dam, Karnataka Water Resources Department Doc. No.: CDSO_DSR_PRR_ KA06HH0098_KaWRD_v1.0 September 2019 Central Water Commission Ministry of Water Resources, River Development & Ganga Rejuvenation Government of India
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Project Rehabilitation Report of Kabini Dam
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Project Rehabilitation Report
of Kabini Dam, Karnataka Water Resources Department
Doc. No.: CDSO_DSR_PRR_ KA06HH0098_KaWRD_v1.0
September 2019
Central Water Commission
Ministry of Water Resources,
River Development & Ganga Rejuvenation
Government of India
Project Rehabilitation Report of Kabini Dam
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Project Rehabilitation Report of Kabini Dam
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Quality Control:
Version Date Writers/Contributors Checked by
1 29/09/2019 Dr. Hadush S Hagos (HSH) Pankaj Kumar Awasthi (PKA Anil Kumar Verma (AKV)
Rajiv Kumar Sawarn
Issued/Copied to:
I/C Date Name Organisation
Issued 30/09/2019 Shri. Pramod Narayan Central Water Commission
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Abbreviations
DRIP Dam Rehabilitation & Improvement Project
CWC Central Water Commission
CPMU Central Project Management Unit
CSV Construction Site Visit
SPMU State Project Management Unit
IA Implementation Agency
PIC Project Identification Code
DSRP Dam Safety Review Panel
PST Project Screening Template
DFR Design Flood Review
MSL Mean Sea Level
FRL Full Reservoir Level
MWL Maximum Water Level
TBL Top Bund Level (Top Level of Dam)
MDDL Maximum Draw Down Level
LSL Lowest Sill Level
DSL Dead Storage Level
U/S Upstream
D/S Downstream
El. Elevation
L/B Left Bank
R/B Right Bank
PMF Probable Maximum Flood
SPF Standard Project Flood
CD Works Cross Drainage Works
VRB Village Road Bridge
WBM Water Bound Macadam
NDT Non Destructive Testing
DHARMA Dam Health And Rehabilitation Monitoring Application
O & M Operation and Maintenance
EAP Emergency Action Plan
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ESMF Environmental and Social Management Framework
E & S specialists Environmental and Social Specialists
HM Works Hydro-Mechanical Works
EM Works Electro-Mechanical Works
SCADA Supervisory Control and Data Acquisition System
DG Set Diesel Generator Set
MW Mega Watt
MU Million units
Ha Hectare
MCM Million Cubic Metre
Deg. Degree
Min. Minute
Sec. Second
CM Construction management
QC Quality control
m meter
m3 Cubic meter
m3/sec Cubic meter per second
Km2 Square kilometre
Mcm Million cubic meter
TNWRD Tamil Nadu Water Resource Department
TANGEDCO Tamil Nadu Generation and Distribution Corporation
KWRD Kerala Water Resource Department
KSEB Kerala State Electricity Board
MPWRD Madhya Pradesh Water Resource Department
UJVNL Uttarakhand Jal Vidyut Nigam Limited
DVC Damodar Valley Corporation
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DRIP Component Wise Project Cost
KaWRD Initial/Revised Projects & Cost
BACKGROUND
In April 2012, the Central Water Commission
(CWC) with assistance from the World Bank,
embarked upon a six year Dam
Rehabilitation and Improvement Project
(DRIP) at a preliminarily estimated initial cost
of Rs.2100 Crore targeting rehabilitation and
improvement of about 250 dams initially of
six, later of nine implementing agencies -
namely: MPWRD, OWRD, TNWRD,
TANGEDCO, KWRD, KSEB, KaWRD,
UJVNL and DVC.
In June 2018, the project was extended by
two years, until June 2020. The current
revised cost for DRIP is Rs.3466 Crore out of which Rs. 2920.5 Crore is allocated for
Component 1 (Rehabilitation and Improvement of Dams and Associated Appurtenances),
Rs.232.5 Crore for Component 2 (Dam Safety Institutional Strengthening), and Rs.313 Crore
for Component 3 (Project Management). Appropriate assistance is also provided under
DRIP to develop O & M Manuals and Emergency Action Plans (EAP) for these dams. The
project also promotes new technologies and improves institutional capacities for dam safety
evaluation and implementation at the Central and State levels as well as in some identified
premier academic and research institutes in the country. The actual total number of dams
under DRIP stands at 223.
The Implementing Agencies for DRIP are the Water Resources Departments and State
Electricity Boards in the participating States and Damodar Valley Corporation (DVC) with
Central Water Commission at Central Level. State Implementing Agencies are responsible
for implementation of works of dams under their charge. Co-ordination and management of
such works within a State rests with the
concerned State Project Management
Unit (SPMU). Overall project oversight
and coordination is carried out by Central
Project Management Unit (CPMU) headed
by the Project Director with assistance of
an Engineering and Management
Consultant.
Karnataka Water Resource Department
(KaWRD) joined DRIP in August 2014
with initial number of dams totalling 31.
Later, KaWRD dropped 9 dams and
continuing in DRIP with 22 dams.
Preliminarily estimated initial DRIP project
cost for KaWRD was Rs.276.1 Crore and
the revised actual current project cost is
Rs.581.2 Crore.
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Table of Contents
Abbreviations .......................................................................................................... iv
Annex D: ESMF OK Card ....................................................................................... 51
Annex E: Third-party Test Results ........................................................................ 55
Annex E: Photographs Before and After Rehabilitation Works ......................... 59
Annex F: DBA and Inundation Maps .................................................................... 77
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1. EXECUTIVE SUMMARY
This Project Rehabilitation Report (PRR) is for Kabini Dam, which is one of the 22
dams under DRIP in the state of Karnataka. The Dam Safety Review Panel (DSRP)
inspected the dam on 22nd May 2015 and recommended both structural & non-
structural measures to be taken up by the dam authorities.
DSRP main recommendations included reaming of porous and foundation drains;
repair of spillway stilling basin; repair of right bank canal intake structures; raking and
pointing of upstream face of non-overflow masonry dam section; repair of worn-out
roller track of gate grooves and replacement of rubber seals as necessary; removal
of vegetative growth in the toe drain; provision of man holes along toe of the dam;
provision of additional V-notch weir; and provision of Casagrande type vertical stand
pipe piezometers. Non-structural measures included review of design flood, reservoir
siltation surveys; dam stability analysis; preparation of EAP and O&M manual.
As per the PST, the original peak design flood for Kabini Dam was 5,497.71 cumec
with a corresponding MWL of 696.16 m and the revised design flood (PMF) under
DRIP worked out to be 15,762.56 cumec. Flood routing study carried out by the
SPMU as part of the Dam Break Analysis (DBA) reveals that the revised MWL is at
EL 698.4 m, which is 2.24 m above the original MWL/FRL of 696.16 m. The TBL is at
EL 700.7 m and the available freeboard above the revised MWL is 2.3 m, which is
more than the minimum recommended 1.50 m as per IS 10635.
Following DSRP recommendations, rehabilitation works carried out under DRIP
included:
Civil Works:
• Improvements of drainage gallery and reaming of porous & drainage holes.
• Restoration of baffle blocks in the stilling basin.
• Providing shotcreting to concrete surface and repointing to masonry surface of right bank canal sluice.
• Providing shotcreting to concrete surface of spillway pier & improvements to masonry surface of non-overflow sections.
• Restoration of downstream earthen embankment slope.
• Providing barbed wire fencing around downstream periphery.
• Construction of security booths.
• Improvements to service road of drainage gallery.
• Providing and fixing CCTV surveillance.
• Improvements to electrical system.
• Providing fire extinguisher system.
HM Works: Replacement of damaged portion of catwalk.
The rehabilitation works were executed under 2 contracts (Civil & HM) at a total
completion cost of Rs. 1006.88 Lakhs, which included one variation order of 165.3
Lakhs for additional works in the repair of stilling basin baffle blocks.
Dam Break Analysis (DBA) and inundation maps prepared by SPMU were reviewed
and approved by CPMU. Draft Emergency Action Plan (EAP) and Operation and
Maintenance (O&M) manual prepared by the SPMU are under review process by
CPMU.
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2. PROJECT DETAILS
The Kabini dam is located across Kabini River in Kodagu district, Karnataka state at
Latitude of 75º54’20” N and Longitude of 12º29’30” E. It was completed in the year
1974. The project consists of an earthen dam 2478 m long and 7.32 m dam crest
width. It has 80.77 m long spillway with 4 nos. of radial gates having discharge
capacity of 5,497.71 cumec.
The TBL, FRL, original MWL and Spillway Crest level are at EL 700.7 m, 696.16 m,
696.16 m and 684 m, respectively. The gross storage at FRL is 552.7 MCM (or 19.52
TMC).
2.1 Project Description
Sl. No.
Item Details
a. Project Identification Code (PIC) KA06HH0098
b. Project Name Kabini Dam
c. River Basin Cauvery
d. Sub River Basin Kabini
e. River/Stream Kabini
f. Catchment area (km2) 2141.90
g. Year of commencement of project 1959
h. Year of completion of project 1974
2.2 Project Location
Sl. No.
Item Details
a. State Karnataka
b. District Mysore
c. Earthquake Zone II
d. Survey of India Map Ref No’s 57 D & 58 A
e. Nearest City Heggadadevana Kote
f. Nearest Airport Mysore
g. Nearest Railhead Mysore
h. Name of Immediate U/S Project Banasursagar Dam (Kerala)
i. Name of Immediate D/S Project Hullahalli Anicut
j. Latitude in Deg., Min, Sec. (North) 11º56’27”
k. Longitude in Deg., Min, Sec. (East) 76º20’17”
2.3 Project Benefits
Sl. No. Item Details
a. Type of Project Multipurpose
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Sl. No. Item Details
b. Gross Command Area (Ha) 45748
c. Culturable Command Area (Ha) 44534
d. Annual Irrigation Potential (Ha) 45748
e. Hydropower –
Installed Capacity (MW) 20
f. Hydropower –
Firm Power (MW) 20
g. Hydropower –
Average Annual Generation (MU) 30
h. Domestic/Municipal/Industrial Water –
Annual Quantum (MCM) 79.28
i. Domestic/Municipal/Industrial Water –
Area and Population Benefitted Mysore Tq & H.D. Kote tq
j. Flood Protection –
Flood Protected Area (Ha) Nil
k. Flood Protection –
Details of Area Benefitted Nil
l. Details of Tourism/Recreational Facilities Nil
2.4 Dam and Reservoir Features (Before rehabilitation under DRIP)
Sl. No.
Item Details
a. Full Reservoir Level (m) 696.16
b. Original Maximum Water Level (m) 696.16
c. Gross Reservoir Storage Capacity at FRL (Mm3 )
552.7
d. Live Storage Capacity (Mm3 ) 453.07 (as per O&M manual)
e. Revised Live Storage Capacity, if any
(Mm3 ) 453.07
f. Date of bathymetric survey, if any 2007 – 2008
g. Dam Type Composite (Earth Cum Masonry Dam)
h.
Length of Dam at Top (m)
i) Total length of the main dam
ii) Length of embankment dam
iii) Length of masonry/concrete dam
2732.55 (as per O&M manual)
2478.02
254.53
i. Number and length of dykes (No. & m) Nil
j. Top of dam (El. in m.) 700.7
k. Top Level of Upstream Parapet Wall of main dam (El. in m.)
-
l. Height of Dam (m)
i) Embankment dam – above river
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Sl. No.
Item Details
bed level (up to dam top without camber)
ii) Concrete/Masonry dam – above deepest foundation level (up to dam top)
28.95
57.60
m Top width of main dam (m) 7.32
n. Spillway details
i) Location Middle
ii) Type of spillway Ogee
iii) Length of spillway (m) 80.77
iv) Spillway crest level (m) 684
v) Type of Gate Radial
vi) Number and size of gates (no. and
m. x m.) 4, 12.19 X 12.19
vii) Number and thickness of piers (no.
and m. x m.) 3, 7.62 (as per O&M manual)
o.
Outlet/Sluice details
i) In Embankment dam
• Number
• Size (Width (m). x Height (m).)
• Location
• Invert level El. (m)
• Discharging capacity (m3/s)
ii) In Concrete/Masonry dam
• Number
• Size (m. x m.)
• Location
• Invert level El. (m)
• Discharging capacity (m3/s)
2 Nos. LBC & 5 Nos. RBC
1.22 X 1.3, 2.44 X 3.05
LBC, RBC
685.5, 685.5
2.55, 65.13
3 Nos.
2.4 X 4.27
Middle
676.35
333.2 (as per O&M manual)
Note: All elevations are above MSL
2.5 Any Emergency Spillway, Fuse Plug etc.
Nil
2.6 Details of previous dam incidents, if any
Nil
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2.7 PST Details
Sl.
No. Item Date/Cost Remarks
a. PST first received from SPMU 03/07/15
b. Proposed PST Cost (INR in Lakhs) 1470.0
c. First review by CPMU 25/08/15
d. Final review by CPMU 30/10/15
e. World Bank Approval 09/11/15 E- mail dated 09/11/2015
f. Approved PST Cost (INR in Lakhs) 1234.0
2.8 DSRP, CPMU and World Bank Recommendations and Compliance
2.8.1 DSRP Recommendations and Compliance
Compliance to DSRP recommendations as submitted by SPMU/dam authorities is
shown on pages 6 to 18 below.
2.8.2 CPMU/World Bank Recommendations and Compliance
Revised design flood (15190 cumecs) evaluated by CWC Hydrology Directorate being about 2.86 times the original design flood (5497.71 cumecs), WRD, Government of Karnataka should get the flood routing studies conducted on priority to check the adequacy of free board available and furnish these studies to Project Director (DRIP), CWC and CPMU, CWC to enable them to advice on the structural / non‐structural measures required to be taken. The requisite structural measures, as advised by Director (DRIP), should be taken up by the Government of Karnataka for implementation in a separate package.
Flood routing study was carried out by the SPMU as part of the Dam Break Analysis (DBA) and results reveal that the revised MWL is at EL 698.4 m, which is 2.24 m above the original MWL/FRL of 696.16 m. The TBL is at EL 700.7 m and the available freeboard above the revised MWL is 2.3 m, which is sufficient as per IS 10635.
Non-shrink and UV resistant cementitious materials utilising crystalline technology or Poly Ironite Ceramic Cement, or equivalent, and conforming to Indian and or European standards are recommended to be used for all surfaces exposed to high-velocity flows.
Following the recommendation from CPMU, PICC was used to repair the damaged baffle blocks in the stilling basin.
2.9 Scope of Rehabilitation Works as per PST
(a) Remedial Measures (Structural)
i. Improvements of drainage gallery and reaming of porous holes and drainage holes in drainage gallery.
ii. Restoration of baffle pier in the stilling basin.
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iii. Providing shotcreting to concrete surface and repointing to masonry surface of Kabini right bank canal sluice
iv. Providing shotcreting to upstream face of spillway pier & improvements to masonry surface of Non-flow section.
v. Rehabilitation of detorated surface of spillway portion.
vi. Restoration of downstream embankment of earthen embankment slope.
vii. Providing barbed wire fencing around downstream periphery of Kabini dam.
viii. Construction of Security booths at Kabini dam.
ix. Providing and constructing manhole chambers in vulnerable reaches along toe drain.
x. Replacement damaged portion of catwalk.
xi. Providing spillway stoplog gate.
(b) Non-structural Measures
xii. Stability analysis of Kabini Dam
xiii. Setting up of warning system.
xiv. Improvements to electrical system of Kabini dam.
(c) Basic Facilities Enhancement
xv. Stability analysis of Kabini Dam
xvi. Setting up of warning system.
xvii. Improvements to electrical system of Kabini dam.
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2.10 Drawings
Figure 2-1: Index Map of Kabini Dam.
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Figure 2-2: Google Map of Kabini Dam.
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Figure 2-3: Water Catchment Map of Kabini Dam.
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Figure 2-4: Layout Map of Kabini Dam.
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Figure 2-5: Longitudinal Section of Kabini Dam.
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Figure 2-6: Typical Cross Section of Kabini Earth Dam.
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Figure 2-7: Cross-section of Kabini Masonry Dam.
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3. DAM VISITS (PST STAGE)
3.1 Dam Inspections
Sl. No.
Item Date of visit Remarks
a. Dam Safety Review Panel (DSRP) 22 May 2015
b. Site Visit made by CPMU experts -
3.2 Summary of observations made by CPMU
Nil.
4. DESIGN FLOOD REVIEW (DFR)
4.1 DFR Outcome
Sl. No.
Item Original
Value
Revised
Value Remarks
a. Inflow Design Flood (m3/s) 5497.71 15762.56 PMF
b. Spillway Capacity / Routed Outflow (m3/s)
- 7455.2 Flood routing
study by SPMU
c. Maximum Water Level (m) 696.16 698.4 TBL = 700.7
4.2 Brief Summary of Review
As per the PST, the original peak design flood for Kabini Dam was 5,497.71 cumec with a corresponding MWL of 696.16 m and the revised design flood (PMF) under DRIP worked out to be 15,762.56 cumec. Flood routing study carried out by the SPMU as part of the Dam Break Analysis (DBA) reveals that the revised MWL is at EL 698.4 m, which is 2.24 m above the original MWL/FRL of 696.16 m. The TBL is at EL 700.7 m and the available freeboard above the revised MWL is 2.3 m, which is more than the minimum recommended 1.50 m as per IS 10635.
Replacement of damaged portion of cat walk of kabini
dam,PAPER BILLS, TRANSPORTATIO
N FACILITY etc
15.5 NCB 03/10/15 - -
124/2017-18
24/02/18
M/s Nandi Steel Products: Pro Sri SN Basavaraju, Class I
Contractor, No 1926/A 3rd Main,
3rd Cross, Tarala Balu Badavane,
Davanagere
2 23/04/18 15.4 12.58 30-03-18
Total 843.4 1006.88
* Final Completion Certificate for Package 2 is awaited from dam authorities.
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7.2 Details of Bidding process
As per details in the above table.
7.3 Reason for Variation, if any
One variation order of amount 165.3 Lakhs was registered in the Civil works package
for change in material for repair of stilling basin baffle blocks.
7.4 Litigation / Arbitration, If Any
No litigation.
8. THIRD PARTY CONSTRUCTION SUPERVISION VISITS BY
CPMU
8.1 Summary of Visits undertaken
Sl. No. Date of visit Transmittal details of CSV Report
a. 02-03-2017 4554/11-05-20
b. 06-06-2017 4688/12-06-2017
c. 07-09-2017 5211/10-11-2017
d. 06-02-2018 5620/07-03-2018
8.2 Summary of Third-Party Material Testing
Laboratory proctor test as well as field compaction test have been carried out by
CPMU for downstream slope embankment works. The field compaction test results
were unsatisfactory and were recommended for rectification at the time. Third-party
tests results are attached in Appendix D.
8.3 Summary of Major Recommendations
1st Construction Site Visit Report
The Overall status of the works is listed below:
▪ The EIC is recommended to improve overall management of the works being
carried out using an OK card for tracking all embankment works. Other OK
cards are being used effectively and progress is well-documented. The
Contractor is working closely with the EIC to ensure the remaining works are
implemented using best engineering practices.
▪ Emergency time constraints for supply of water to Bangalore during this
drought period impacted the work being carried out in the stilling basin baffle
repair and the review of additional work is pending dewatering to assess the
performance of the shotcrete over the M60 grade steel-fibre concrete.
Recommendations:
▪ Reaming of porous drains has been completed. The porous drains have open
grates on the crest of the dam that is allowing both air and water to penetrate
the dam body and creating an environment for formation of calcareous
materials that will eventually clog the drains; CPMU recommends that a
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provision be included in the current scope for closing the porous drains on the
crest with removable caps and installing “water traps” in the gallery as per IS
codes. Specifications are provided in the code for accomplishing this task.
▪ The stilling basin has been de-watered for repair of the energy dissipaters, or
“baffle” blocks. The baffle block cavities were filled with M60 grade steel-fibre
concrete and then overlaid with M20 grade wet-placed shotcrete. The
consensus during the visit was that this was a mistake. Dimple Chemical
offered to apply a thin layer of PICC cementitious mortar over the baffles.
CPMU recommends that the procedures be reviewed by SPMU, and if
necessary, corrected; the baffles will require additional monitoring for
understanding the effectiveness of the works; all documents for the approval
and tracking progress of this work need to be kept for the record. Any
additional new work that may be found necessary for safety and
completeness of the works is recommended to follow best engineering
practices and address WB requirements for deviations from the approved
scope of work.
▪ The embankment works include re-sectioning of the downstream slope in
certain areas that have consolidated back to design lines and grades. This
requires placement of soil up to 30-cm-thick in certain areas. CPMU
recognizes the difficulty in conducting this work and recommends small
benches be cut into the existing embankment, placing of suitable material and
compacting the material to 95% dry density using acceptable best
engineering practices.
2nd Construction Site Visit Report
Observations and Recommendations:
▪ Black ants have invaded the embankment on the downstream slope. These
ant colonies have perforated the embankment at numerous locations and
forming tunnels. CPMU recommends application of an environmental-friendly
pesticide while embankment works are being carried out.
▪ The reservoir level is expected to continue to drawdown and in the process
additional voids in the masonry are observed below the existing upstream
face guniting. CPMU recommends this be investigated and a scope
developed to rake and re-point the masonry sections below the waterline.
Work to be carried out as budget and time allow.
▪ A low berm has been constructed to support the re-sectioning work being
carried out. An excavator-powered vibratory roller is being used to protect the
bank while work is being carried out. CPMU also recommends silt fences be
installed along the hinge points of the berm to minimize soil erosion during the
upcoming monsoon, which has already started within the region and
recommends work be carried out fully after the wet season.
▪ Electrical work is being carried out: the electrical cables have been buried in
the embankment without conduit or wiring protection. CPMU recommends all
wiring be chased through GI or HDPE conduit and placed at least 500-mm
under the embankment slope to protect the cable. At the rock toe, the conduit
is recommended to be placed under the rock toe for protection. The final
placement is to be surveyed and marked on as-built drawings for future
reference, if required, for routine maintenance, repair or replacement.
3rd Construction Site Visit Report Observations:
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Observations and recommendations
▪ Ant infestations are predominant within the embankment and project staff are
recommended to treat the embankment with environmental-friendly
pesticides. Left unattended, the ants will continue to loosen the embankment
resulting in formation of erosion rills.
▪ The downstream kerb wall masonry foundation is recommended to be
reconstructed; over the years, settlement of the embankment has resulted in
loss of foundation support and many sections of the wall are in disrepair. The
upstream wall is recommended to be studied and determination for repair of
the foundations be taken up.
Sl. No
Observation / Deficiency Remarks
1
Additional voids in masonry joints below EL 2244 ft., that is, below guniting of piers. Action to be taken for pointing (CSV-2)
Could not execute as the water level in the reservoir has raised.
2 Provision is made in the contract for chipping 100 mm thick spillway glacis concrete and redo with M-60 concrete.
It may be difficult to maintain the smooth profile of M-60 concrete to be done for 100 mm thick after chipping of the glacis for 100 mm. also by resorting to chipping using pneumatic equipment will disturb the glacis surface and the bondage between old and new concrete is also at doubt for such a shallow depth of concrete. Instead CPMU recommends for resorting to application of abrasion resistant rim coat as has been done in Almatti & Narayanpur Dam, In lieu of M-60 concrete.
3
Electrical cable for dam top illumination are run in embankment & on concrete surface by the side of kerb & Parapet without any protection. (Fig-3 & 4)
CPMU recommends for running the cables through PVC pipes embedded in earth to avoid any damages to cable and subsequent arising of any eventualities.
4
Wetness at D/s face of masonry dam (NOF) at Right flank at Ch. 1985 ft. for a width of about 3.00 m is observed below EL 2265.00 ft. (Fig-12)
Pointing to U/s face of NOF sections has been done from EL.2244 ft.(Crest level) the wetness is observed in the zone where U/s & D/s pointing is done. As no grouting is done from U/s or to the body of the dam, the seepage path might not be blocked fully.
5 Considerable quantum of seepage is observed in porous blocks nos 22, 21, 20 & 19.
Mostly these porous blocks are in the NOF section encased by the Wrap Around. Because of constraint in doing pointing to masonry joints below surface of wrap around the seepage may be considerable in these porous blocks. Project authorities must confirm whether these porous blocks are coming in the wrap around area. If so then the remedial measure is to take up the body grouting from top of dam to reduce the seepage in these porous blocks.
6 Water is coming out of drainage holes 5, 6 & 13 with pressure in 1’ pipe.
Quantum of seepage and uplift pressure is to be measured for various reservoir levels for study and decision by the designers.
7
Joints of Masonry of left training wall have opened at back side. Lot of vegetation has grown in the joints (Fig-18)
The vegetation growing in the masonry joints will further weaken the structure. Hence it is recommended for uprooting of vegetation and pointing the joints with cement mortar
4th Construction Site Visit Report Observations:
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Observations and recommendations:
▪ The gallery walls remain wet in many sections even at lower reservoir water
level of 2272.45 ft during this inspection (FRL is at 2284 ft). The completed
upstream face treatment above EL 2244 ft (spillway crest level) does not
seem to have brought a noticeable effect in reducing seepages in the gallery.
As budget and time allow, CPMU recommends a geophysical scan be carried
out to assist in determining water leakage areas and develop a rehabilitation
plan to minimize and maintain the seepage within allowable limits.
▪ Other previously recommended actions include a post-rehabilitation
inspection (using ROV) of the badly eroded baffle blocks to determine the
efficacy of the works accomplished; the baffles were gunited with M15
concrete over the M60 grade cavity filling material.
▪ CPMU notes that turfing is required to protect d/s slope of the embankment
section from damages by erosion. The same to be considered for taking up
as budget and schedule allow including using Contract savings, if any. Chute
and longitudinal drains shall also be considered on the d/s embankment
slope.
▪ Between CH 1660 m and 1760 m, the d/s section of the embankment dam
crest and kerb wall have settled over 15 cm. The specific reason for this
settlement is yet to be determined and necessary rectification carried out.
No. Deficiency / Observation Remarks
1 No turfing on d/s slope of embankment dam section.
SPMU to consider using some savings from other activities to take up turfing works on d/s slope of dam. Vertical and longitudinal drains shall also be provided on d/s slope.
2 Gallery remains wet even after completion of u/s face treatment
SPMU recommended to consider geophysical scanning of the dam and determine critical leakage areas.
3 Electrical cable for dam top without protection.
CPMU recommends for running the cables through PVC pipes embedded in earth to avoid any damages to cable and subsequent arising of any eventualities.
8.4 Summary of Compliance by SPMU
Compliance letter received from SPMU against the CPMU experts’ comments during
construction site visits is shown below on page 28 to 30.
8.5 Summary Special Visits made by CWC/World Bank/Expert Committee
Nil
8.6 Summary of Technical Assistance provided by CPMU
• Review of PST. • Review of design flood.
• Provided technical guidance on maintaining quality of works as per design, contract agreement technical specification and best engineering practices.
• Third party quality control tests.
• Review of dam break analysis and inundation maps.
• Review of O&M manual (currently on-going).
• Review of EAP (currently on-going).
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9. ENVIRONMENTAL AND SOCIAL MANAGEMENT
FRAMEWORK (ESMF)
9.1 Basic Details
No. Item Yes / No Remarks
a. ESMF Issue Identified in PST Yes
b. Mitigation Measures Proposed Yes
c. Any Rehabilitation and Resettlement involved No
d. Site Visit Date of CPMU E&S Specialists -
e. Site Visit Report of CPMU E&S Specialists -
9.2 Summary of Observations
ESMF management during implementation was generally satisfactory but PPE was
partially used during construction, which was later improved. ESMF OK Card is given
in Appendix E.
9.3 Details of ESMF/EIA study (if any)
Nil.
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10. OTHER NON-STRUCTURAL INTERVENTIONS
10.1 Basic Details
Sl. No.
Item Yes / No Remarks
a
Emergency Action Plan (EAP)
(i) EAP Available at Site
(ii) EAP Prepared under DRIP
(iii) EAP Published
(iv) Stake holder consultations
No
Yes
No
No
Inundation maps prepared by SPMU was reviewed and approved by CPMU. EAP prepared by SPMU was reviewed by CPMU.
b. O&M Manual availability Yes O&M manual prepared by SPMU has been reviewed by CPMU.
c. Inflow Forecasting No
d. DHARMA Implementation Yes In progress. Most data uploaded.
e. Siren No Yes
10.2 Summary of Observations
Nil
11. PENDING REHABILITATION WORKS
11.1 Details of pending works
i. Finalization & Publication of EAP.
ii. Finalization & Publication of O&M manual.
iii. Completion of data entry in DHARMA.
iv. Address noted incompliances to DSRP recommendations.
11.2 Further course of action
All pending actions stated above should be completed before December 2019.
12. REFERENCES
i. PST
ii. DSRP report
iii. Construction site visit report.
iv. Information received from SPMU from time to time
v. Completion Certificate.
vi. World Bank approval
vii. Third-party test result
viii. Compliance letters from SPMU.
ix. Inundation report and maps.
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Annex A: PST Approval Letter
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Annex B: Drawings issued for
Rehabilitation measures
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Annex C: Completion Certificate
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Annex E: Photographs Before and
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Stilling Basin Baffle Blocks – Before & During Construction
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Stilling Basin Baffle Blocks – After
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Upstream Face – Before
Upstream Face – During
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Upstream Face – After
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Repair of RBC – During
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Repair of RBC – After
Reaming of porous holes
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1. INTRODUCTION
1.1: Preface:
Karnataka Engineering Research Station is a premiere Research Institute under
Water Resources Department, Government of Karnataka. The Research Station was
entrusted with the dam break analysis and preparation of inundation maps for Emergency
Action Plan of Kabini Dam by the Project Authorities.
The necessary training and inputs for dam break modeling have been provided by
CWC under DRIP. The required information and details of the Kabini dam have been
provided by the Project Authorities.
A draft report comprising dam break analysis of Kabini Dam and inundation
mapping for different scenarios was submitted to CWC for review, for which some
comments and suggestions were received from the review committee vide letter no.
5213/10.11.2017 (enclosed vide Annexure-2).
Further, the Deputy Director, CWC, New Delhi had directed to depute the
concerned officers of KERS to CPMU (DRIP), New Delhi for modification and finalization
of the Kabini Dam Break Analysis (letter enclosed vide Annexure-3). As per the
instructions of CPMU (DRIP), New Delhi, the Kabini Dam Break analysis Model were
modified and resubmitted for approval. The approval of the Kabini Dam Break Model by
CPMU (DRIP) was sent through mail and the same is attached vide Annexure-4. The
present report has been prepared incorporating all the recommendations/suggestions of
CPMU(DRIP), New Delhi.
1.2: General:
Based on the type of dam and conditions of the dam site, a dam may fail due to
multiple causes. In addition, the breach shape and timing of a dam failure varies with the
type of dam under consideration. Concrete gravity dams may suffer a partial breach with
the failure of one or more monolith sections. Concrete arch dams may fail suddenly and
completely within a few minutes. Embankment dams do not fail completely or suddenly
as their concrete counterparts. Breaching action in an earthen embankment dam
continues to the point where the reservoir is depleted completely or to the point where
the breached materials resist erosion, such as the dam foundation. The most common
cause of dam failure is flood or dam overtopping. The next common cause is piping or
seepage.
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1.2.1: Overtopping Failure:
Overtopping due to large inflow flood is the most common failure mode for
embankment dams. It occurs when the water surface elevation in the reservoir exceeds
the height of the dam. The flow of water over the crest of the dam, an abutment, or a low
point in the reservoir rim follows as a consequence. The foundation and abutments of a
concrete dam may also be eroded due to overtopping, leading to loss of support and
failure due to sliding or overturning. For embankment dams, the failure begins at a
downstream location, with head cutting progressing upwards gradually. As it reaches the
dam top, the width of the dam crest is eroded fast, before the reduction in height starts
taking place. This proceeds at a fast rate and may include the phase of maximum outflow
for a reservoir with capacity small compared to its height. In this phase, the earthen dam
without a core behaves mostly like a sharp crested weir.
The opening created by erosion expands gradually, almost in the shape of a
trapezoid. As the height is reduced to the foundation level, outflow may continue for a
long time if the reservoir is of sufficiently large capacity. For such cases, the peak rate of
outflow is also expected to occur during this phase. The flow mostly resembles the
overflow pattern observed over a broad crested weir with long crest.
1.2.2: Piping Failure:
Piping occurs when concentrated seepage paths develop within an embankment
dam. The seepage slowly continues to erode the dam embankment or foundation, leaving
behind large voids in the soil. Piping begins near the downstream toe of the dam and
works its way towards the reservoir upstream. Erosion proceeds at a more rapid rate as
the voids become larger and larger. As the erosion reaches the reservoir upstream, it
may enlarge and cause total failure of the dam. The process of internal erosion and piping
may be broken up into four phases: initiation of erosion, continuation of erosion,
progression to form a pipe and ultimately, the formation of a breach. Piping failures occur
in earthen dams only. Once such a pipe connection is formed, it is almost impossible to
save the dam from failure.
1.2.3: Large Controlled Releases:
Flood risks at locations downstream of the dam may also arise without any failure
of the dam and its components. After construction of a dam, the safe carrying capacity of
the river channel normally keeps on decreasing, due to the diversion of water as well as
flood moderation by the reservoir. Consequently, after many years of dam construction,
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the river channel downstream of a dam loses its capacity to carry the peak flood
magnitudes. So, extensive bank overflows become associated with flood discharges. The
situation gets further aggravated due to developmental activities taking place in the
floodplain because of reduced frequency of inundation.
In the event of a severe flood in the dam catchment having a magnitude of peak
discharge near to the design flood of the dam, the priority of dam operation will shift to
saving the dam. Otherwise, a dam breach may endanger the lives of many more persons
residing in the downstream area. With the passage of flood flows near to the spillway
capacity, severe floods causing huge inundation may occur. It may even lead to loss of
lives which has to be minimised through implementation of strict floodplain regulatory
management plans and flood warning.
1.3: Objectives:
• The main purpose of the study is to find out the areas downstream of Kabini Dam
which will be inundated due dam breach scenarios such as overtopping and non-
flood failure (piping) and to find out the inundation scenario in case of large
controlled release.
• To estimate the number of villages and people at risk due to dam failure and large
controlled release.
• To assess the submergence of infrastructure facilities such as roads and railways.
• To prepare the inundation maps for the breach scenarios such as overtopping and
piping and for controlled large release.
1.4: Scope:
• The scope of the study is restricted to failure of the dam due to overtopping and
piping only. However, inundation maps are prepared for both the cases of failure
and for large controlled releases. No other failure scenarios such as landslide,
earthquake, malfunction of gates and planned removal are considered in this study
because the HEC-RAS software cannot simulate these conditions.
• A tier-2 approach to dam breach and inundation mapping are followed which is an
intermediate level of analysis using medium resolution terrain data. A tier 3
approach to dam breach analysis could be carried out using high resolution LIDAR
data.
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2. DESCRIPTION OF KABINI DAM
The Kabini Dam is located at Beechanahalli, near H.D. Kote, Mysore District,
Karnataka State with Lat 110 56’ 27” N and Long 76020’17” E and with a catchment area
of 2142 Sq.Km. The gross capacity of reservoir is 19.52 TMC. Kabini dam is a composite
dam with central masonry overflow section and non-overflow section and left and right
earthen embankment. It caters to the needs of around 22 villages and 14 hamlets and
also serves as a prominent source of drinking water to Bengaluru. Further significant
amount of water is discharged to the Mettur reservoir in Tamilnadu to fulfill the state's
needs. The salient features of Kabini dam is as given below;
Table 2.1: Salient features of Kabini dam
Name of the Project Kabini Reservoir Project
Type of Project Multi-Purpose Project
Name of Dam Kabini Dam
Location of Dam Near Beechanahalli-Bidarahalli Village, H.D.Kote Taluk, Mysore District
Name of River Basin location Cauvery basin
River Tributary Kabani, Papanashini and Panamarum Puzha
of Kerala
Latitude 11056’27” N
Longitude 76020’17” E
Catchment Area 2141.90 Sq.Km
Gross storage capacity 19.52 TMC
Live Storage 19.19 TMC
Dead storage 0.33 TMC
Lowest Foundation Level (ft) RL 2110.00
River Bed Level (ft) RL 2204.00
Crest Level (ft) RL 2244.00
Full Reservoir Level (ft) RL 2284.00
Maximum Water Level (ft) RL 2284.00
Top of the Dam (ft) RL 2299.00
Maximum Water Spread Area at FRL 64.03 Sq.Km
Type of Dam Masonry gravity dam with overflow and non- overflow sections with earthen flanks on either side