About civil engineering

1. SERI NALLAH
DIVERSION OF SERI NALLAH AWAY FROM
ATAL TUNNEL ALIGNMENT

2. GENESIS
 During construction of Atal Tunnel, Seri Nallah fault zone was
encountered
 An Expert committee was formed by MOD which recommended
following: -
 Sealing and strengthening of concrete lining through Grouting
Works inside Atal Tunnel
 Diversion of Seri Nallah
 MoU signed between BRO and NHPC on 25th Jan 2022 for Diversion
of Seri Nallah
 Contract was awarded to M/S Venser by NHPC on 19th June 2022.
 Work started on ground on 01st Sep 2022 but subsequently it was
stopped by DFO due to Forest Clearance(FC)
 FC case was uploaded on Parivesh portal on 15 March 2022 and
uploaded again on 17 march 2023.
 Provisional sanction was granted on 17 July 2023
 Work resumed on 19 July 2023

3. GOOGLE IMAGERY OF SITE
SERI
NALLAH

4. Scope of Work Agency
 Diversion of Seri Nallah NHPC
 Construction of approach road to Drainage
Portal – 3.0 Km
BRO
 Construction of internal roads to various
sites of works – 3.80 Km
BRO
SERI NALLAH WORKS

5. SERI NALA DIVERSION SCHEME – LAYOUT PLAN
DRAINAGE
TUNNEL
GEO TREATMENT OF
SERI NALAH BED WITH
GEOMEMBRANE 450
MTR LENGTH
TRENCH
WEIR
PROPOSED
PRECAST RCC
PIPE WATER
CONDUCT
SYSTEM
ATAL
TUNNEL
SERI NALLAH
SOUTH PORTAL
DRAINAGE
TUNNEL
OUTLET
 Nallah Bed Treatment for 450 m length at Crossing of Seri Nallah area over Atal Tunnel to make the
nallah bed impervious for surface flow.
 A 3.0 m dia 623 long D-shaped unlined Drainage Tunnel to tap and divert part of the underground
seepage affecting Atal Tunnel is proposed above Atal Tunnel between Seri nala bed and Atal Tunnel.
 Trench weir 400 m downstream of outlet portal of drainage tunnel proposed to collect surface water
flow of Seri Nallah and underground seepage from drainage tunnel and divert towards south portal of
Atal tunnel through precast concrete RCC drain pipes of 1.40 m dia for 1050 m length as water
conductor system.
NORTH PORTAL

6. METHODOLGY PROPOSED FOR DIVERSION WORKS
 Nallah Bed Treament
 Seri nallah crosses above the Atal Tunnel alignment at Chainage 2500 m from South
Portal.
 Treatment of Seri nala bed from 450 m length on Upper reaches from this location
is proposed for bed treatment with Geomembrane and Geotextile with Gabion
mattress and Grouting to make the nallah bed impervious for surface flow and
thereby restricting the penetration of snow melt in the surrounding media.
 Drainage Tunnel
 To tap and divert part of the underground seepage affecting Atal Tunnel, a 3.0 m
diameter, D-shaped unlined drainage tunnel is proposed above Atal Tunnel
between Seri nala bed and Atal tunnel.
 Drainage tunnel has been aligned parallel to the alignment of Atal tunnel in order to
cover the Seri nala fault zone encountered during excavation of Atal tunnel which
might be contributing to seepage in the Atal tunnel.
 The water from drainage tunnel is outlet downstream of the Seri Nallah.
 Trench Wier
 Trench weir 400m downstream of the outlet portal of drainage tunnel has been
proposed to collect surface water flow of Seri nala and underground seepage from
drainage tunnel and divert towards south portal of Atal tunnel through precast
concrete RCC drain pipes of 1.40 m dia for 1050 m length.

7. SERI NALLAH DIVERSION WORKS
Name of Work Diversion of Seri Nallah away from Atal Tunnel,
Rohtang, Himachal Pradesh
Date of Signing of
MoU
25.01.2022
Name of Contractor M/s Vensar Constructions Company Limited,
Banjara Hills, Hyderabad
Letter of Award NH/CCW/CC-I/CO-182/PR11221/Seri Nallah/258/159
dated 19.07.2022
Contract Sum Rs.115,31,44,334/- (Rupees One Hundred Fifteen
Crore Thirty One Lakh Forty Four thousand Three
Hundred Thirty Four Only)
Revised due to change in GST rate from 12% to
18%
Rs.121,49,19,923/- (Rupees One Hundred Twenty
One Crore Forty Nine Lakh Nineteen thousand
Nine Hundred Twenty Three Only)

8. SERI NALLAH DIVERSION WORKS
Scheduled Date of Start 19.07.2022
Date of Completion
(As per Contract)
30.10.2023 (469 days)
Date of handing over of site to
contractor by NHPC
30.08.2022
(after restoration of access road by BRO).
Actual Date of Start of work 01.09.2022
Date of Completion
(As per revised schedule
submitted by contractor)
29.06.2024
Proposed Date of Completion
(after receipt of Forest Clearance)
04.10.2024

9. PHYSICAL & FINANCIAL PROGRESS OF WORK
(A) PHYSICAL PROGRESS
S.
N.
Description Date of
Start
Physical
Progress
Remarks
1. DRAINAGE TUNNEL WORK
(a) Excavation of
Drainage
Tunnel
25.07.23 4.8 % Slow progress due to
(a) Delay in handing over of site.
(b) Opening of crown at RD 4.5m to
10m & treatment thereof.
2. SERI NALLAH BED TREATMENT
(a) Excavation 01.11.22 80 % As per schedule.
(b) Concreting 13.09.23 5.9 % Slow progress due to
(a) Cement supply was badly affected
due to blockage of road at
multiple points upto site during
monsoon season.
(b) Stoppage of aggregate supply
due to impose of ban on crusher
plant by State Authority.

10. PHYSICAL & FINANCIAL PROGRESS OF WORK
S.
N.
Description Date of
Start
Physical
Progress
Remarks
3. CONSTRUCTION OF TRENCH WEIR
(a) Excavation of
Trench Weir
21.08.23 85%
(b) Concreting of
Guide Wall
25.09.23 50%
(c) Excavation for
laying of Pipe
line
21.09.23 28%
(B) FINANCIAL PROGRESS
 10% (approx.) financial progress has been achieved

11. SERI NALLAH BED TREATMENT – C/S
Geomembrane 1 mm
Geotextile 1 mm
River Bed Level
Geotextile 01 mm
Concrete Bed 300 mm
Gabion Mattress 500 mm

12. SERI NALLAH BED
GABION MATTRESS
GEOSYNTHETICS MEMBRANE
GEOTEXTILE
CONCRETE BED

13. DRAINAGE TUNNEL
FOREPOLING EXCAVATION
EXCAVATION REMOVAL OF MUCK

14. DRAINAGE TUNNEL- FOREPOLING
6m 6m
4m
(10⁰ – 12⁰ )
@150 mm C/C
X
X
X-X View
DRAINAGE TUNNEL X-Sec
3m
3m

15. TRENCH WEIR PLAN

16. TRENCH WEIR
Gabion Mattress
Geosynthetics Fibre

17. TIMELINE CHART
S.No Item Description Unit
BOQ
Qty
(LOA)
BOQ /
Anticipated
Qty
Qty
executed
Balance
Qty
Oct-23
Jun-24
Jul-24
Aug-24
Sep-24
Oct-24
Nov-24
1 2 7 8 8 9 10=8-9
I
Mobilisation & Initial Nallah
Diversion
II Exploratory Drilling Work
1
Drilling of exploratory hole in
Drainage Tunnel (200m)
m 200 200 0 200
40 20 20 60 60
III Seri Nallah Bed Treatmnent
1 Excavation of Seri Nala Bed Cum 102630 102630 66000 36630
25000 11630
2
Concreting/Treatment of Seri
Nala Bed
Cum 14600 11000 340 10660
5000 3500 2160
IV Drainage Tunnel
1 (a) Portal excavation Cum 5625 3213 3213 0
1 (b) Portal Concrete work Cum 50 45.99 45.99 0
2 Excavation of Drainage Tunnel m 610 623 23 600
100
MS-1
(25.07.23)
50 50 150 150 100
MS-4
3
Invert concreting, Drilling of
Drainage hole & Grouting
m 610 623 0 623
200 400 23
V Trench Weir Works
1 Diversion/Protection Dyke
2 Excavation of Trench Weir Cum 5080 13500 11000 2500
2250 250
3 Concreting of Trench Weir Cum 1950 1950 580 1370
800 400 170
MS-2
4 Back Filling Cum 12600 12600 970 11630
5000 2500 4130
5(a) Boulder Wire Crates Cum 382 382 0 382 120 60 60 142
5(b) CC Block Placement Cum 1350 1350 0 1350 400 300 250 400
VI Intake & Silt Flushing Conduit
2
Intake & Silt Flushing Conduit
excavation
Cum 580 1500 0 1500
1000 500
3
Intake & Silt Flushing Conduit
concreting
Cum 1810 1810 0 1810
600 1210
4 Back Filling Cum 9450 9450 0 9450 2500 5000 1950
VII
Precast Concrete Pipes, Drop
Collection Well, Outlet Spill
Channel
1
Excavation of Concrete Pipes,
Drop Collection Well, Outlet
Spill Channel.
Cum 37500 37500 2000 35500
9000 4250 4250 9000 9000
3
Laying of Precast Concrete
Pipes
m 1000 1000 0 1000
140 140 140 280 280 20
4 Other Concreting Works Cum 2700 2700 0 2700
400 350 350 700 700 200
5 Back Filling Cum 15750 15750 0 15750
2500 5000 5000 3250
VIII
HM Works (Design,
Fabrication, Erection &
Testing)
Sets 1 1 0 1
MS-3
Project : Diversion of Seri Nallah away from Atal Tunnel, Rohtang, Himachal Pradesh
Schedule of Construction
Nov-23
Dec-23 -
April-24
May-24
NON
-WORKING
SEASON
NON
-WORKING
SEASON
NON
-WORKING
SEASON

18. PLAN FOR COMPLETION OF WORK
 Non-working season: 15th Nov 2023 to 14th May 2023
 Milestones:
 MS-1 - Start of Excavation of Drainage Tunnel (25.07.2023)-
Achieved
 MS-2 - Completion of Concreting of Trench Weir (23.05.2024)
 MS-3 - Completion of HM Works (01.08.2024)
 MS-4 - Completion of Excavation of Drainage Tunnel (19-08-2024)
 Completion: 04-10-2024
 Working Season variation: Normally non Working Season has been
considered from 15th Nov to 14th May, however, in this working
season, continuous rainfall caused considerable delay and
hampered progress of work.

19. ARSN RD 3 KM
CONNECTIVITY
FMN Cl-9
GSB
WBM
BT
Km
0.00
Km
1.00
Km
3.00
Km
2.00
0.400
2.400
2.700

20. BT WORK ON APPROACH RD

21. INTERNAL RDS 3.80 KM
 Construction of road to reach the point
from where Seri Nallah will be diverted
(At site of Seri Nallah)
3.80 Km
 Date of Commencement 28 Sep 2022
 Tentative PDC Dec 2023 (W/o BT)
 Physical Progress 14 %
(Fmn cutting appx 2030 m done.
Accessibility granted to Seri
Nallah Bed Treatment work,
Trench weir and Drainage Tnl)
 Financial Progress 8 %
 Work suspended Work suspended due to snow fall
wef Nov 2022 till May 2023
Currently FMN and PMT work is in
progress

22. ARSN INTERNAL RD 3.80 KM
FMN Cl-9
GSB
WBM
Km
0.00
Km
1.00
Km
3.00
Km
2.00
Km
3.80

23. THANK YOU