This document contains responses to comments on hydraulic calculations and GAD drawings for a bridge over the Yamuna River. The key points addressed are: 1) Discharge calculations were done conservatively and account for cumulative flows. 2) Interpretation of discharge criteria is correct. 3) Foundation levels and scour calculations do not need revision. 4) Span arrangement is fixed in the contract and cannot be changed. 5) Dimensions and details will be shown in structural drawings. 6) Bearing capacities and pressures are reviewed and found to be acceptable.

1. Sl.
No.
Comments Reply
1. Comments on Hydraulic Calculation
(Ref: BSEC/1509 / DN-03)
1.1 (Page .1) CWPRS Model study report for metro rail bridge at Kalindi Kunj
may please be forwarded to us.
The report is attached with the mail.
1.2 Discharge of Hindon River has been considered which is estimated at NH -
58 over existing bridge in Ghaziabad. Additional discharge on D/S of the
bridge up to the junction point with Yamuna is also to be added to
estimate total discharge of Hindon river into Yamuna River.
Discharge calculations carried out by us is on the conservative
side & duly takes into account the cumulative discharge from
Kalindi Kunj bridge (as available in CWPRS Report) + discharge
from Hindon river (as per Hindon bridge data) + additional
discharge due to the catchment area between Kalindi Kunj
bridge & project site. The reason why this discharge is
‘conservative’ is because the Hindon river is divided into
tributaries after Ghaziabad and the entire discharge of Hindon
river is not coming to Yamuna at u/s the proposed bridge.
1.3 (Page-2) As per Cl.6.2.1 if it does, Restrict it to that limit- and not to
the second highest discharge value stated by you. Please review the
interpretation.
Our interpretation of the said clause is correct. The highest
value of discharge shall be discarded if it is by more than 50% of
second highest discharge (It can be said that more than 1.5
times the second highest discharge).
1.4 (Page-5) The calculation by Area- velocity method needs to be reviewed
in ref. to Para 5.7 of SP: 13-2004 where area of stream (un-obstructed) is
to be considered i.e. prior to the construction of bridge.
Calculations carried out by BSEC is correct & do not require any
change. Clause 5.7 is not relevant in this context.
1.5 (Page-6) CWPRS report as indicated in 1.1 above is required. Refer response to point 1.1.
1.6 (Page-9) Calculation of Afflux –‘A’=un-obstructed sectional area of the
river at proposed site Here area between abutment faces is considered
and not un- obstructed. Please review.
There is no defined bank in Abutment A1 side. ‘A’ considered in
the calculation is the unobstructed area between the guide
bund on A1 side & from bank on A2 side, ignoring the
obstruction caused by pier & pier foundation.
Calculation of HFL
Since calculated HFL value is lower than adopted value it will be
appropriate to calculate MSL with respect to the calculated value of HFL
to have safety against scour for fixing Foundation LVL. Adopted value of
HFL can be considered for fixing clearance/ FRL of bridge as FRL cannot
be lesser than in tender drawing.
Only one HFL shall be considered for all calculation in a bridge.
We can not have one HFL value for scour calculations & another
HFL value for clearance calculation.
1.7 (Page-7) Calculation of scour depth to be reviewed in the light of
comments at 1.6 and other comments stated above.
Refer response to point 1.6.
2. Comments on GAD of Yamuna Bridge @ CH: 102+575

2. (Ref: Sheet 1)
2.1 Looking to the proposed size and depth of well foundation, the span of 60
m appears to be uneconomical and may be considered to have between
42m to 50m to economize on the cost of superstructure and the bridge as
a whole. Please review
The span arrangement is fixed in the Contract Agreement and
no change is possible.
2.2 HFL, MSL may require revision in view of our comments on Hydraulic
calculations.
Refer our reply for 1(1.6).
2.3 Actual HFL is estimated at RL 197.103m, but taken 199.00 m as per DPR.
Actually, HFL will touch at RL 197.103m, so scour level, foundation level
to be calculated accordingly. Difference in HFL will be considered towards
additional free board as the formation level is to be kept as per DPR.
Refer our reply for 1(1.6).
(Ref: Sheet 2)
2.4 The well cap top is kept at RL 188.30m i.e. 1.80 m above the LWL. This
may not look aesthetically better than keeping the well cap top at LWL.
The well cap can be cast inside the false steining to be made over the last
lift of well steining.
As per clause 708.11.1, the bottom of well cap shall be laid
above the LWL.
2.5 The dimensions of various components, foundation levels etc. are missing.
These may be shown in GAD.
These informations will be shown in detailed structural
drawings.
2.6 The dredge hole of wells is shown empty which may require sand filling
over bottom plug upto MSL with an IP and above IP water filling upto well
cap bottom.
It is not necessary to fill the dredge hole with sand.
2.7 Seismic restrainer shown on the pier cap plan at the center of the pier
cap. This may be to restrain longitudinal moment. Transverse seismic
restrainer may also be shown and the length of the pier cap may be
suitably adjusted.
The seismic restrainer shown in pier cap shall act as a
longitudinal as well as transverse seismic restrainer.
2.8 In the “Detail 4”, Carriageway center line is shifted by 90 mm from the
center line of well / pier / superstructure. Please inform the reason for
the same.
This is done to account for tilt of the superstructure units for
camber.
2.9 In the “Notes”, at Sr. No. 5, the grade of HYSD bars should be Fe-500
instead of Fe-5000.
HYSD bar grade is shown as 500 D & not 5000.
2.10 In the “Notes”, at Sr. No. 11, Hydraulic data may require modification in
the light of our comments on the hydraulic calculations.
Refer response to point 1(1.6).

3. 2.11 In the “Notes”, at Sr. No. 13, gross bearing capacity needs to be reviewed
being on higher side in our opinion.
Gross bearing capacity is considered as per Geotechnical
Report.
2.12 The wearing coat specifications may also be mentioned in the notes. Noted & agreed.
2.13 The steining thickness can be designed with reduced thickness by using
jack down system for well sinking from economy and speed consideration.
Normal sinking method is to be adopted.
3. Geotech Report of Major Bridge on River Yamuna:
Estimation of Load Bearing Capacity of Concrete Circular 8.00m diameter
well. Based upon criteria for settlement of well:
3.1 100 mm settlement has been considered for estimation of allowable
bearing capacity. This seems to be on higher side. Generally, upto 75 mm
settlement is considered for estimation of bearing capacity. This may
please be reviewed in view of having two span continuous type of
superstructure.
As per IRC:78-2014, clause 706.3.2, the differential settlement
shall not exceed 1/400 of the span i.e. 150mm in this bridge
hence 100mm settlement considered is conservative
assumption.
3.2 The gross bearing capacity has been estimated 110 t/sqm2
at RL
154.00mand 105 t/sqm2
at RL 155.50m (Proposed founding level for pier
wells). This seems to be on higher side. Please review.
It is reviewed & found OK.
3.3 The base pressure in normal case at the pier foundation level is 90 t/sqm2
which seems to be quite high. Please review.
It is reviewed & found OK.