Post on 04-Jun-2018
8/14/2019 Hydraulic Design - Scan Doc.docx
1/36
3.4.2 Hydraulic Design
Once the peak flows were estimated, the drain conveyance capacities were determined through a
hydraulic design. Manning's formula and continuity equation was used for various trial sections to
obtain the optimum slope and the section of the drain. The dimensions were practically fixed to
suit the site conditions.
The formulas are given as follows:
Continuity equation: Q* = A.V Where A = Cross sectional area of flow m
Q'= Actual Discharge (cumecs) V
= Velocity of Flow (mis)
Manning's Equation: V
=
Where R = Hydraulic Mean Depth
(m) V= Flow velocity m/s S =
Channel slope
Where A= Cross sectional area of flow m
P = Wetted perimeter (m)
Culvert channel designs were performed by selecting trial sections assuming a free board of
0.5m and calculating the actual discharge Q' and comparing it with the peak flow Q obtained
in the hydrologic design. For a satisfactory performance of the culvert Q' > Q i.e. the drain
should have a capacity to carry a flow equal or more than the peak flow also the velocity of
the flow should preferably less than 2.0 m/sec.
3.4.3 Use of "Flow Master "and "Culvert Master" Software
For the opening size computation "Flow Master "and "Culvert Master" software were also
employed.
3.4.4 Specimen calculations
Manual calculation and software calculation for Culvrt at chainage 27+308 km are given below Culvrt at
chainage 27+308 km was located at U/S of tributary of Maha oya.
Existing Slope of the stream Highway crossing chainage at 27+308 km
n
R= A
8/14/2019 Hydraulic Design - Scan Doc.docx
2/36
Total catchment
Length of the longest watercourse
Existing slope of the catchment
Corresponding velocity of catchment
(According to table 3.1)
Time of concentration
(Ponrajah's Formula)
Return period
Rainfall intensity
(By Ranathunga's formula)
= 50 Years
I = 7895 (T+49.4) --8BB1
= 127.54 mm/hr
Corresponding Run off coefficient = 0.40
(Reffering Ponrajah's table and "Applied Hydrology by Ven Te Chow")
Q=CIA/360
Q=8.13m3/s
Assuming 1m water depth according to site condition,
Using Maning's Formula Design section can be calculated.
Full suply depth (FSD) =1 m
Design discharge (Q) =8.13 m3/s
Design s!ope(S) such that velocity along
Cuvert less than 2.0m/sec =0.001
Manning's formla corresponding to concrete (n) =0.013
Q = 1R2/3S1/2A
= 1A5/3
S1/2
\ A2/3
n
v> Q = 1fBWxFSDf/3S1/2
1' (BW+2FSD)2/3n
Solving above equation, BW,= 4.31m
8/14/2019 Hydraulic Design - Scan Doc.docx
3/36
Taking BW = 4.5m
Taking Free board as 0.5m, Design section = 4,5m x 1.5m
Qmax for design section = 8.57 m3/s
Qdesign =8.13m3/s
Hence design section is ok for maximum discharge for 50 years return period.
Specimen calculation for design section of culvert is same as Design section of Bridge,
BW Calculation for 27+308 Culvert Worksheet for Rectangular Channel
Project Description
Project File c:\haestad\academic\fmw\ckah cor.fm2
Worksheet 27+308
Flow Element Rectangular Channel
Method Manning's Formula
Solve For Channel Depth
input Data
Mannings Coefficient 0.01 3
Channel Slope 0.001 000 m/m
Bottom Width 4.31 m
Discharge 8.13 m /s
Results
Depth 1.00 m
Flow Area 4.31 m2
Wetted Perimeter 6.31 m
Top Width 4.31 m
Critical Depth 0.71 m
Critical Slope 0.002716 m/m
Velocity 1.89 ' m/s
Velocity Head 0.18 m
Specific Energy 1.18 m '*
Froude Number 0.60 ^ "
8/14/2019 Hydraulic Design - Scan Doc.docx
4/36
Flow is subcritical.
4.0Drainage Opening Sizes for Culverts and Bridges and Recommended High Flood Level
4.1 Drainage Opening Sizes for Culverts and Bridges along the Expressway
Drainage opening sizes for culverts and bridges were decided using Rational Formula and Manning's Formula
assuming a critical water depth required to pass a 50 years flood. The required opening sizes are given in
Table 4.1 and the relevant hydrologic and hydraulic calculations are given in Annex (B.1) Table 4,1 -
Recommended Drainage Opening sizes for Culverts and Bridges along the Expressway
Culvert
no.
Culvert ID
(Chainage)
Design size Invert up
stream (m
MSL)
Invert down
stream (m
MSL)
Approxima
te Length
(m)
Remarks
79 25+245 10.00mx2.00m 24.00 23.97 41.3
80 25+367 1.50mx1.50m 25.02 24.95 34.9
81 25+565 6.25mx1.50m 25.11 25.07 35.8
82 25+947 6.50mx1.50m 27.62 27.57 43.9
83 26+180 2.00mx1.50m 28.10 28.05 45.2
84 26+550 3.00mx1.50m 34.60 34.55 48.085 27+308 4.50mx1.50m 35.20 35.13 68.2
86 27+481 1.50mx1.50m 35.00 34.95 50.0
87 27+948 4.00mx1.50m 32.58 32.54 39.8
88 28+400 I.75mx1.50m 33.12 33.05 60.7
89 28+500 1.75mx1.50m 33:50 33.43 61.5
90 28+885 2.25mx1.50m 36.50 36.44 36.9
91 29+520 4.25mx1.50m 37.04 36.97 69.1
92 30+036 2.50mx1.50m 38.12 38.05 41.2
93 30+330 2.50mx1.50m 44.09 44.01 47.0,
94 31+156 3.50mx1.50m 35.52 35.45 62.6
95 31+240 3.50mx1.50m 35.50 35.43 68.8
96 31+923 1.50mx1.50m 35.07 35.05 43.6
97 32+000 3. 25m x1. 50m 34.60 34.58 36.0
98 32+088 1.50mx1.50m 34.60 34.58 43.0
99 32+235 1.75mx1.50m 36.02 36.00 46.4
100 32+665 10.00mx2.00m 37.02 36.98 70.3
101 32+985 8.50mx2.00m 36.32 36.29 42.0
102 33+390 1.50mx1.50m 39.10 39.03 44.5
103 33+500 1.50mx1.50m 42.58 42.51 41.3
104 33+858 2.75mx1.50m 42.07 42.05 33.0
8/14/2019 Hydraulic Design - Scan Doc.docx
5/36
105 33+936 6.75mx1.50m 41.13 41.11 37.1
106 34+913 3.50mx2.50m 48.69 48.63 54.2 Dual Purpose
107 35+358 4.25mx1.50m 36.03 35.99 46.7
108 35+410 4.50mx1.50m35.80 35.76 45.6
109 35+460 4.25mx1.50m 35.90 35.86 44.2
Culvert
no.
Culvert ID
(Chainage)
Design size Invert up
stream (m
MSL)
Invert down
stream (m
MSL)
Approxima
te
Length(m)
Remarks
110 35+615 4.00mx1.50m 36.02 35.98 39.4
111 35+730 4.00mx1.50m 36.50 36.45 43.2
112 36+323 2.25mx1.50m 38.94 38.89 43.4
113 36+385 2.25mx1.5Qm 38.14 37.97 57.5
4 36+555 85m opening should be provided for Meerigama-Pasyala Rd and Railway Track
114 36+608 1 .50mx1 .50m 40.36 40.25 111.0
115 36+853 1 .50mx1 .50m 50.28 50.21 74.0
116 37+250 2.00mx1.50m 66.69 66.64 49.5
117 37+522 4.25mx1 .50m 58.65 58.59 57.6
118 37+893 9.00mx1.50m 48.45 48.37 88.6
119 38+001 9.00mx1.50m 48.45 48.39 62.7
120 38+400 2.00mx1.50m 58.94 58.89 46.5
121 38+676 3.25mx1.50m 59.51 59.46 57.2
122 38+943 3.00mx1.50m 64.30 64.26 39.7
123 39+195 3.75mx1.50m 53.46 53.39 72.4
124 40+065 i r-2.50mx1.50m 91.38 91.31 74.3125 40+630 3.50mx1.50m 76.70 76.66 35.6
126 40+815 3.50mx1.50m 57.98 57.92 59.2
127 40+900 1 .75mx1 .50m 54.90 54.82 70.9
128 41+070 2.00mx1.50m 57.75 57.71 44.8
129 41+445 13.50mx2.00m 51.28 51.26 51.4
130 41+565 20.00mx2.00m 48.86 48.83 68.6
131 41+930 3.75mx1.50m 66.16. 65.91 84.5
132 42+580 3.50mx1 .50m 103.84 103.78 54.2
133 42+925 3.00mx1.50m 91.76 91.71 51.9
134 43+545 9.00mx1.50m 56.52 56.47 67.8
135 43+840 3.25mx1 .50m 53.21 53.17 48.2 '
136 43+980 2.25mx1.50m 55.45 55.39 52.1
137 44+120 2.75mx1.50m 56.13 56.08 53.9
138 44+250 4.25mx1.50m 51.85 51.79 70.3
139 44+490 1 .50mx1 .50m 54.07 54.01 55.4
140 44+673 2.00mx1.50m 56.01 55.95 62.4
141 45+135 2.00mx1.50m 84.01 83.95 57.2
142 45+666 1 .50mx1 .50m 80.76 80.66 95.3
143 46+032 1.75mx1.50m 83.95 83.86 85.9
144 46+476 2.00mx1.50m 83.63 83.55 81.9
8/14/2019 Hydraulic Design - Scan Doc.docx
6/36
145 46+892 1 .50mx1 .50m 67.70 67.45 82.7
146 47+451 9.00mx1.50m 56.82 56.75 62.0
147 47+557 7.00mx1.50m 56.61 56.55 69.7
148 47+928 4.50mx1 .50m 66.68 66.61 57.9
5 48+174 32.00mx4.50m 49.84 49.64 103.0
Note: Design sizes up to Culvert No.78 has submitted to RDA in CKAH chainage from 0+000 km to 25+000 km
4.2 Recommended High Flood Level along the Expressway
The recommended High Flood Level for design purposes of the expressway are given below
Table 4.2-Recommmended High Flood Levels of the Culverts across the Expressway
Culvert ID
(Chainage)
Size of Proposed
Structure
Existing Level
(m MSL)
Full Suplly Depth
(m)
Recommended
Flood Level (m
MSL)
25+245 10.00mx2.00m 24.00 1.50 25.50
25+367 1.50mx1.50m 25.02 1.00 26.02
25+565 6.25mx1.50m 25.11 1.00 26.11
25+947 6.50mx1.50m 27.62 1.00 28.62
26+180 2.00mx1.50m 28.10 1.00 29.10
26+550 3.00mx1.50m 34.60 1.00 35.60
27+308 4.50mx1.50m 35.20 1.00 36.20
27+481 1.50mx1.50m 35.00 1.00 36.00
27+948 4.00mx1.50m 32.58 1.00 33.58
28+400 1.75mx1.50m 33.12 1.00 34.12
28+500 1.75mx1.50m 33.50 1.00 34.5028+885 2.25mx1 .50m 36.50 1.00 37.50
29+520 4.25mx1.50m 37.04 1.00 38.04
30+036 2.50mx1.50m 38.12 1.00 39.12
30+330 2.50mx1.50m 44.09 1.00 45.09
31+156 3.50mx1.50m 35.52 1.00 36.52
31+240 3.50mx1.50mv 35.50 1.00 36.50
31+923 1.50mx1.50m 35.07 1.00 36.07
32+000 3.25mx1.50m 34.60 1.00 35.60
32+088 1.50mx1.50m 34.60 1.00 35.60
32+235 1.75mx1.50m 36.02 1.00 37.02
32+665 10.00mx2.00m 37.02 1.50 38.52
32+985 8.50mx2.00m 36.32 1.50 37.82
33+390 1.50mx1.50m 39.10 1.00 40.10
33+500 1.50mx1.50m 42.58 1.00 43.58
33+858 2.75mx1 .50m 42.07 1.00 43.07
33+936 6.75mx1.50m 41.13 1.00 42.13
34+913 3.50mx2.50m 48.69 1.00 49.69
35+358 4.25mx1.50m 36.03 1.00 37.03
35+410 4.50mx1.50m 35.80 1.00 36.80
8/14/2019 Hydraulic Design - Scan Doc.docx
7/36
35+460 4.25mx1.50m 35.90 1.00 36.90
35+615 4.00mx1.50m 36.02 1.00 37.02
Culvert ID
(Chainage)
Size of Proposed
Structure
Existing Level
(m MSL)
Full Suplly
Depth (m)
Recommended
Flood Level (mMSL)
35+730 4.00mx1.50m 36.50 1.00 37.50
36+323 2.25mx1.50m 38.94 1.00 39.94
36+385 2.25mx1.50m 38.14 1.00 39.14
36+555 85m opening should be provided for Meerigama-Pasyala Rd and Railway Track
36+608 1.50mx1.50m 40.36 1.00 41.36
36+853 1.50mx1.50m 50.28 1.00 51.28
37+250 2.00mx1.50m 66.69 1.00 67.69
37+522 4.25mx1.50m 58.65 1.00 59.65
37+893 9.00mx1.50m 48.45 1.00 49.45
38+001 9.00mx1.50m 48.45 1.00 49.45
38+400 2.00mx1.50m 58.94 1.00 59.94
38+676 3.25mx1.50m 59.51 1.00 60.51
38+943 3.00mx1.50m 64.30 1.00 65.30
39+195 3.75mx1.50m 53.46 1.00 54.46
40+065 2.50mx1.50m 91.38 1.00 92.38
40+630 3.50mx1.50m 76.70 1.00 77.70
40+815 3.50mx1.50m 57.98 1.00 58.98
40+900 1.75mx1.50m 54.90 1.00 55.90
41+070 2.00mx1.50m 57.75 1.00 58.75
41 +445 13.50mx2.00m 51.28 1.50 52.7841+565 20.00mx2.00m 48.86 1.50 50.36
41+930 3.75mx1.50m "-66.16 1.00 67.16
42+580 3.50mx1.50m * 103.84 1.00 104.84
42+925 3.00mx1.50m 91.76 1.00 92.76
43+545 9.00mx1.50m 56.52 1.00 57.52
43+840 3.25mx1.50m 53.21 1.00 54.21
43+980 2.25mx1.50m 55.45 1.00 56.45
44+120 2.75mx1.50m 56.13 1.00 57.13
44+250 4.25mx1.50m 51.85 1.00 52.85
44+490 1.50mx1.50m 54.07 1.00 55.07
44+673 2.00mx1.50m 56.01 1.00 57.01
45+135 2.00mx1.50m 84.01 1.00 85.01
45+666 1.50mx1.50m 80.76 1.00 81.76
46+032 1.75mx1.50m 83.95 1.00 84.95
46+476 2.00mx1.50m 83.63 1.00 84.63
46+892 1.50mx1.50m 67.70 1.00 68.70
47+451 9.00mx1.50m 56.82 1.00 57.82
47+557 7.00mx1.50m 56.61 1.00 57.61
47+928 4.50mx1.50m 66.68 1.00 67.68
8/14/2019 Hydraulic Design - Scan Doc.docx
8/36
48+174 32.00mx4.50m 49.84 3.50 53.34
4.3 Drainage Opening Sizes for Overpasses and Underpasses along the Expressway
Drainage Opening size for overpasses and underpasses were also determined using the methods used to
determine culvert openings. The required opening sizes are given in Table 4.3 and the relevant hydrologic and
hydraulic calculations are given in Annex (B.2)
Table 4.3 - Recommended Drainage Opening sizes for Overpasses and Underpasses
Road ID Chainage Opening Size RemarksDivulapitiya-Naiwala Rd (RDA) 25+535 (LHS) 9.25mxl.50mDivulapitiya-Naiwala Rd (RDA) 25+535(RHS) l.OOmxl.SOm vMedagampitiya-Hanchapola Rd (PS) 26+394 (LHS) 2.50mxl.50mMedagampitiya-Hanchapola Rd (PS) 26+394(RHS) 4.25mxl.50m
Banduragoda-Weyangoda Rd (PS) 27+451 (LHS) 6.00mxl.50m Should be provided to suit site conditionsBanduragoda-Weyangoda Rd (PS) 27+451 (RHS) l.SOmxl.SOm Should be provided to suit site conditionsRoad (PS) 27+980 (LHS) l.OOmxl.SOmRoad (PS) 27+980(RHS) 1.75mxl.50mBanduragoda-Weyangoda Rd (PS) 28+720 (LHS) l.OOmxl.SOm
Banduragoda-Weyangoda Rd (PS) 28+720(RHS) l.OOmxl.SOm
Road (PS) 29+210 (LHS) l.OOmxl.SOm
Road (PS) 29+210(RHS) l.OOmxl.SOm
Keppetiwalana-Baduragoda Rd (PS) 29+707 (LHS) l.OOmxl.SOmKeppetiwalana-Baduragoda Rd (PS) 29+707(RHS) l.OOmxl.SOm
Gaspe Rd (RDA) 30+520 (LHS) l.OOmxl.SOmGaspe Rd (RDA) 30+520(RHS) 1.25mxl.50mRoad (PS) 31 +040 (LHS) l.OOmxl.SOmRoad (PS) 31+040(RHS1 l.OOmxl.SOmRoad (PS) 31 +395 (LHS) 1.25mxl.50m Should be provided to suit site conditionsRoad (PS) 31+395(RHS) 2.00mxl.50m Should be provided to suit site conditionsRoad (PS) 31+830 (LHS) 1.25mxl.50m
Road (PS) 31+830(RHS) 1.25mxl.SOmRoad (PS) 32+839 (LHS) 6.25mxl,50m Should be provided to suit site conditionsRoad (PS) 32+839(RHS) 13.00mxl.50m Should be provided to suit site conditionsRoad (PS) 33+490 (LHS) l.OOmxl.SOm Should be provided to suit site conditionsRoad (PS) 33+490(RHS) l.SOmxl.SOm Should be provided to suit site conditionsMeerigama-Wewaldeniya Rd (PS) 37+579 (LHS) l.OOmxl.SOm Should be provided to suit site conditions
Meerigama-Wewaldeniya Rd (PS) 37+579(RHS) l.OOmxl.SOm Should be provided to suit site conditionsMeerigama-Danovita Rd (PDA) 39+149 (LHS) l.OOmxl.SOm Should be provided to suit site conditionsMeerigama-Danovita Rd (PDA) 39+149(RHS) 1.25mxl,50m Should be provided to suit site conditionsKoshena-Soduruwatta Rd (PS) 40+510 (LHS) 2.25mxl.50mKoshena-Soduruwatta Rd (PS) 40+51 0(RHS) 1.75mxl.50m
Diversion Rd (PS) 40+885 (LHS) l.SOmxl.SOm Should be provided to suit site conditionsDiversion Rd (PS) 40+885(RHS) 7.50mxl.50m Should be provided to suit site conditionsRoad (PS) 41 +085 (LHS) l.OOmxl.SOm
Road (PS) 41+085(RHS) 1.75mxl.50m
Road (RDA) 41+620 (LHS) 2.00mxl.50m Should be provided to suit site conditionsRoad (RDA) 41+620(RHS) 2.00mxl.50m Should be provided to suit site conditions
Road (PS) 42+595 (LHS) l.OOmxl.SOm
Road (PS) 42+595(RHS) l.OOmxl.SOm
8/14/2019 Hydraulic Design - Scan Doc.docx
9/36
Diversion Rd (PS) 43+616 (LHS) 2.00mxl.50m Should be provided to suit site conditionsDiversion Rd (PS) 43+616(RHS) 7.00mxl.50m Should be provided to suit site conditionsRoad (PS) 44+228 (LHS) l.OOmxl.SOm Should be provided to suit site conditionsRoad (PS) 44+228(RHS) l.OOmxl.SOm Should be provided to suit site conditions
Road ID Chainage Opening Size Remarks
Diversion Rd (RDA) 44+444 (LHS) l.OOmxl.SOm Should be provided to suit site conditions
Diversion Rd (RDA) 44+444(RHS) l.OOmxl.SOm Should be provided to suit site conditions
Diversion Rd Meerigama (RDA) 45+1 54 (LHS) l.OOmxl.SOm Should be provided to suit site conditions
Diversion Rd Meerigama (RDA) 45+1 54 (RHS) l.OOmxl.SOm Should be provided to suit site conditions
Road (RDA) 45+464 (LHS) l.OOmxl.SOm
Road (RDA) 45+464(RHS) l.OOmxl.SOm
Diversion Rd (PS) 45+802 (LHS) l.OOmxl.SOm Should be provided to suit site conditions
Diversion Rd (PS) 45+802(RHS) l.OOmxl.SOm Should be provided to suit site conditions
Road (PS) 46+488 (LHS) 4.75mxl.50m Should be provided to suit site conditions
Road (PS) 46+488(RHS) l.OOmxl.SOm Should be provided to suit site conditionsRoad (PS) 46+91 8 (LHS) l.OOmxl.SOm Should be provided to suit site conditions
Road (PS) 46+91 8(RHS) l.OOmxl.SOm Should be provided to suit site conditions
Diversion Rd (PS) 47+51 2 (LHS) l.OOmxl.SOm Should be provided to suit site conditions
Diversion Rd (PS) 47+512(RHS) l.OOmxl.SOm Should be provided to suit site conditions
Note : LHS and RHS are with reference to the direction of chainage increase
8/14/2019 Hydraulic Design - Scan Doc.docx
10/36
5.0 Water Quality Monitoring Plan
5.1 Scope of the Study
The monitoring plan covers three phases of water quality situation in the project area. These are baseline
(existing condition), construction phase and operational phases. The scope of this study/report is limited to
surface water quality.
5.2 Background
Water pollution due to highway projects both during construction and operation are mostly a Non-Point
Sources (NPS) Pollution issue caused by contaminated runoff. Point source pollution can also occur during the
construction (Discharge of untreated effluent from Labor Camps, etc.) and in operation (Discharge from
restaurants in rest areas, etc). Tackling point source pollution is relatively easy through enforcement of
environmental protection regulations and provisions of environmenta! safeguards in the construction contracts.
Non Point Source pollution on the other hand is difficult to address through such measures but needs
qualitatively different approaches.
The water quality assessments of highway projects have two basic objectives as described below.
(a) Estimation of pollution loads or concentrations as a result of the said highway during construction and
operation and thereby develop suitable impact mitigation measures;
(b) Prepare an monitoring plan that will enable the authorities to determine whether the safeguards put in
place are effective and thereby to help to meet the water quality objectives
An important component of any water quality assessment of this nature is water quality monitoring. The
monitoring program shall establish the baseline conditions, water quality during construction and operation.
Water quality monitoring is an expensive exercise. Therefore one of the most important requirements of water
quality monitoring is to determine a sampling program that would provide the required information at an
acceptable cost. The sampling program shall cover the sampling locations, frequency (space-time framework
of sampling plan) and water quality parameters. The choice of parameters is normally based on ambient water
quality requirements. Cost is usually a factor that limits the type and number of parameters included in
monitoring plans. Testing should be based on accepted standard procedures. Also
sampling and testing should be carried out by experience technicians in accredited laboratories. This is
important if the data are to be accepted in a court of law.
5.3 Assessment of Project Area
8/14/2019 Hydraulic Design - Scan Doc.docx
11/36
5.3.1 Field Assessment
Water quality sampling plan needs identification of sampling locations. For this purpose a reconnaissance field
visit was undertaken on 7th
December and 14th
December 2010 to identify the water-bodies located in the said
stretch of the proposed expressway. This is basically a census of surface water-bodies that the proposed
expressway cut across from Baduragoda to Abepussa Interchange. Table 5.1 provides the list of water-
bodies (streams, canals, water pools/ponds and rivers) found in this stretch. The surface water-bodies
identified are mainly the irrigation canals also functioning as part of the storm water drainage systems. Table
5.1 depicts the usage of the water bodies observed during the field study [See the Notes at the bottom of
Table 5.1]. Figure 5.1 Map shows locations and The GPS coordinates of the Location IDs defined in Table
5.1 are provided in Table 5.2.
Shallow wells are a common feature along the expressway trace. At several places wells were found next to
streams/-canals with water overflowing from the mouth. These are public wells mainly used for bathing and
washing. Wells located in home gardens are mainly for household consumption including drinking.
Table 5.1-Surface Water-Bodies Located between Baduragoda - Ambepussa
Location ID* Description Usage
WQ1 Kuda Oya - major streamWashing/Bathing/ Storm water Drainage/
(Note- Not withdrawn for water supply in
the immediate downstream)
WQ2 Small irrigation ditch cutting across DudlySenanayake Road Irrigation
WQ3Small irrigation canal/ditch by the edge of the paddy filed cuttingaccress Devala Road
Irrigation
WQ4 Small stream which feeds a small pond used for bathing Bathing
WQ5 Two small irrigation ditches Irrigation
WQ6 Small irrigation canal Irrigation
WQ7Irrigation canal with substantial flow going along the edge of the paddy
field and parallel to the toe of the narrow lane
Irrigation (Note: Other uses may be
possible in the downstream)WQ8 Sizable irrigation canal flowing through paddy filed (Village
Kebellawita)
Irrigation (Note: Other uses may be
possible in the downstream)WQ9 Wide irrigation canal with substantial flow Irrigation (Note: Other uses may be
possible in the downstream)
Location ID* Description Usage
WQ10 Small irrigation ditch Irrigation
8/14/2019 Hydraulic Design - Scan Doc.docx
12/36
WQ11Wide channel through paddy lands (in the vicinity of Rilagala); there
was substantial flow
Irrigation/ bathing/washing
WQ12 Small irrigation stream through paddy fields Irrigation
WQ13 Very small irrigation channel; very low flow; Latha Mawatha Irrigation
WQ14 Large stream; substantial flow Irrigation/Bathing /Washing
WQ15Set of small irrigation ditches
Irrigation
WQ16 Very small natural stream flowing through home gardens Drainage
WQ17Sizable stream also serving as a important irrigation drainage canal;
Stream cut across B1 7 road; there are other small irrigation ditches
Irrigation/ Drainage/ Bathing/ Washing
WQ18By the side of main road B17. Drainage channel; railway line is parallel
to the road about 50 feet away
Drainage
WQ19 Small irrigation ditch by the side of the paddy filed fields Irrigation
WQ20Small stream crossing the railway line and going through uncultivated
paddy area
Drainage
WQ21 Two minor irrigation ditches Irrigation
WQ22 Set of small irrigation canals crossing and going parallel to B26 road.These canals combine and convert to a sizable canal with significant
flow
Irrigation/ (Note: Other uses may be
possible in the downstream)
WQ23Two small irrigation canals flowing along the two edges of the paddy
area; substantial flow
Irrigation
WQ24Two small irrigation canals flowing Tajong the two edges of the paddy
area; ^ ,
Irrigation
WQ25Tank situated outside the road boundary but the spill channel of the
tank is cut across by the proposed highway
Bathi ng/Wash ing/I rrigation
WQ26Wide irrigation channel going through a large paddy filed. Two other
small irrigation ditches are flowing at the two edges of the
paddy area
Irrigation/ Drainage (Note: Other uses may
be possible in the downstream)
WQ27 Small irrigation channel flowing at the edge of the paddy land Irrigation
WQ28 Two small irrigation ditches Irrigation
WQ29 Very small irrigation ditch Irrigation
WQ30 About 3 feet wide irrigation ditch running at the edge of the paddy filed
and highland
Irrigation/drainage
WQ31 Small irrigation ditch Irrigation
WQ32 Small irrigation ditch going at the edge of the paddy fields Irrigation
WQ33Sizable irrigation canal partly lined and going through paddy lands Irrigation/washing
Note 1: The descriptions under the "Usage" column are based on observations made during the
reconnaissance filed visit. It is recommended that further investigations were made on ambient uses of
major water-bodies and record the uses with more details for at least 1-2 kilometers downstream.
Note 2: Identifications (ID) numbers of water bodies are given consecutively from the point first visited to the
point last visited. First visited point is defined as WQ1.
8/14/2019 Hydraulic Design - Scan Doc.docx
13/36
Note 3: Flow conditions of the streams, canals etc reflects the situation at the day of the inspection (wet
weather with significant rainfall in the previous days).
Note 4: Irrigation canals also acts as drainage canals in many cases
8/14/2019 Hydraulic Design - Scan Doc.docx
14/36
Table 5.2- Water Quality Locations
Location Longitude Latitude
WQ1 80 12.451 7 14.669
WQ2 80 12.246 7 14.496
WQ3 8011.840 7 14.296WQ4 8011.674 7 14.247
WQ5 8011.428 7 14.466
WQ6 8011.348 7 14.720
WQ7 8011.191 7 14.779
WQ8 8011.094 7 14.879
WQ9 8010.819 7 14.860
WQ10 80 09.806 7 14.382
WQ11 80 09.885 7 14.292
WQ12 80 09.942 7 14.462
WQ13 80 09.049 7 14.099
WQ14 80 08.541 7 14.063
WQ15 80 08.305 713.995
WQ16 80 07.993 714.129
WQ17 80 07.266 7 14.009
WQ18 8007.117 7 14.007
WQ19 80 07.224 7 14.029
WQ20 80 06.842 7 14.590
WQ21 80 06.569 7 14.484
WQ22 80 05.798 7 14.294
WQ23 8005.517 7 14.226
WQ24 80 05.298 7 14.024
WQ25 80 04.873 713.775
WQ26 80 04.490 713.953
WQ27 80 02.344 7 12.369
WQ28 80 02.756 7 12.628
WQ29 80 02.838 7 12.733
WQ30 80 03.078 712.810
WQ31 80 03.351 7 12.975
WQ32 80.03.746 7 13.303
WQ33 80 3.753 713.569
8/14/2019 Hydraulic Design - Scan Doc.docx
15/36
5.3.2 Climatic Conditions
Table 5.3 gives the average annual rainfall for calendar year at Abepussa and Henarathgoda
(Gampaha).
Table 5.3 - Average Annual Rainfall in Millimeters
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Annual
Abepuss ' 50.4 78.1 165.8 271.6 248.2 200.2 126.3 120.7 209.7 399.8 314.5 122.4 2307.7
Henarathgoda 63.8 79.0 141.4 241.0 382.1 231.3 138.3 145.2 250.1 346.1 298.9 159.5 2476.7
It is assumed the rainfall quantities and pattern for Abepussa and Henarathgoda (Gampaha) gauging stationsrepresent the situation for the project area. The key observations of rainfall pattern are:
a. January and February are the driest months and the sizable rainfall is commencing at
end of March. March and April represent the first inter-monsoon period, b. May records significant
rainfall and May to September is the South-West Monsoon
period. Flooding is common in this month, c. October and November together records the heaviest
rainfall period and these two
months represent the second inter-monsoon period. Flooding is common in this period, d. December
to February represent the North-East Monsoon Period.
5.4 Ambient Water Quality Requirements
The best yardstick for evaluating freshwater quality in this case is the ambient water quality requirements for
satisfying various water uses. Table 5.4 reports the water quality criteria for freshwater systems for different
categories of water uses (Central Environmental Authority, 2003). Accordingly there are seven categories of
water uses falling into three classes as given below. Table 5.4 provides the acceptable concentration levels
for some selected parameters for different ambient uses of water. Full details of acceptable parameter levels,
including for heavy metals are available in the CEA publications.
8/14/2019 Hydraulic Design - Scan Doc.docx
16/36
Categories of Water Uses
Nature conservation
Drinking with simple treatment
Bathing and recreation
Fish and aquatic life
Drinking with conventional treatment
Irrigation and agriculture
Minimum quality (other uses)
As water uses for water-bodies are identified (Table 5.1), it is possible to determine the
important water quality parameters and minimum water quality requirements for each water-
body using the published data. Although not required in this case other additional parameters
can be added to evaluate the long-term impacts such as eutrophication.
Table 5.4 - Ambient Water Quality Requirement for Water Use Categories
Water Use
Category
PH Con. Turb DO COD P F SAR SO4 Cl
High]
1
2 6.0 8.5 5 *6 15 0.7 1.5 250 200
3 6.0 9.0 5 20 0.7
4 6,0 8.5 3 15 0.4
5 6,0 9.0 4 30 0.7 1.5 250 200
6 6.0 8.5 700 3 0.7 6-15
Note 1: Con-Conductivity (ds/m); Turb -Turbidity (NTU); pH, SAR -Numerical values; others -
ppm Note 2: Requirements for nature conservation to be determined on case by case basis
Note 3; Refer to CEA publications for concentration limits for other parameters including heavy metals
ass
ass I
ass II
ass II
ass II
ass II
ass II
ass III
8/14/2019 Hydraulic Design - Scan Doc.docx
17/36
5.5 Sampling Plan
5.5.1 Construction Phase
5.5.1.1 Nature of Construction Phase
Among the contributory factors for deterioration of water quality during road construction are:
(a) soil loss causing high sediment loads in runoff which also cause sedimentation in streams
and rivers, soil/sediment can also carry other pollutants to the water column; (b) biological
pollution due to damaged drainage
Pipes, septic tanks, uncontrolled discharge of wastewater generated in labour camps, etc;
and (c) spills of chemicals. During construction increased turbidity, color, suspended solids
are difficult to avoid water quality problems. Chemical pollution commonly includes petroleum
products.
The magnitude of impacts of these pollutants on water-bodies is dissimilar and depends on
ambient uses. In the project area there are no ecologically sensitive water-bodies requiring
application of conservation measures. As such in this case the water-bodies which are used
for water supply, bathing, and recreation are the most critical in terms of water quality. The
main water-body in this section is the Kuda Oya. Although water supply intakes are notpresent in Kuda Oya in the immediate downstrearn. from the point of intersection with the
proposed expressway, it is possible for such intakes in this water-body considering its size.
Most of the other water-bodies identified in Table 5.1 are irrigation/drainage canals. Thus
water quality standards applicable to these water-bodies are significantly less.
The other characteristic of the construction phase is that the wide spread nature of activities,
so that water quality deterioration is reflected across the area under construction. However,
problem could be more acute in certain areas where activities such as bridge construction are
taking place. Similarly high biological pollution could be possible down streams of labour
camps, if located close to waterways. [Note: Special areas such as borrow sites and mining
sites are not included in this study].
5.5.1.2 Special Issues (Bentonite Loss)
Bentonite clays are heavily used in Southern Expressway Project for pile driving work. While
8/14/2019 Hydraulic Design - Scan Doc.docx
18/36
bulk of the betonite is recovered and reused small percentage is always get to the environment
and washed away to natural water courses during rains. Therefore the impact of bentonite on
water quality is of special interest.
Bentonite is basically clay consisting mostly of montmorillonite. It has large water absorbing
capacity thus can convert to viscous liquid which is used in drilling and pilling work in
construction engineering. Bentonite is normally refered by dominant cation such as Calcium,
Sodium, Aluminum, or Potassium. Calcium bentonite has ion exchange characteristics. It can
exchange its Calcium Ion to other irons. Thus theoretically a water quality change takes
place. However, this is absolutely negligible in terms of quantities of runoff water. The other
issue is not so much of water quality but settling of bentonite slurry in small irrigation canals,
waterways and even on access roads. It is heavy and when mixed with water acts as a jelly.
Thus it can settle on the drainage paths within short distance. This is unlikely to cause an
impact unless large quantities are lost inadvertently cause drainage paths to be blocked or
roads surfaces to become slippery when wet.
5.5.1.3 Water Quality Parameters proposed for Monitoring
V '
Water-bodies listed in Table 5.1 can be divided into two broad categories based on their
ambient uses as:
A. Water-bodies used for bathing and recreation (water intakes were not observed in the
immediate project area)
B. Water-bodies serving as irrigation/drainage canals
The water quality parameters for monitoring are determined based on pollutants that are likely
to gain entry during construction and affecting the ambient uses. The proposed parameters
are given in Table 5.5.
5.5.1.4 Sampling Locations
To an extent water-bodies in Table 5.1 divided into two environmental settings.
(a) WQ 1- WQ 14 - somewhat hilly terrain
(b) WQ 15 - WQ 33 - relatively flat terrain
In similar environmental settings water quality impacts of construction are likely to be felt
8/14/2019 Hydraulic Design - Scan Doc.docx
19/36
similarly in the downstream of the road trace. Section from WQ 15- WQ 33 (See the Map given
in Figure 5.1) is more or less similar to the last segment of the first 25 kilometers, which was
covered in the previous study. Also a water-body of significant importance was not found in
this section. [Note: One irrigation tank is located at WQ 25. However, this is located upstream
of the proposed expressway and not expected to be affected by the proposed project
significantly].
On the other hand WQ 1 to WQ 14 represents somewhat hilly area and not part of flood plains. It
is assumed that water quality effects of the project are similar in this section. Therefore two
use-wise important water-bodies are proposed in this section for monitoring. The two water-
bodies are WQ 1 (Kuda Oya) and WQ 11 (Irrigation Canal in Rilagala Area). Monitoring at
upstream location is also proposed for these two water-bodies. The reason for inclusion of
upstream location in the monitoring plan is that it provides water quality data undisturbed by
the construction activities. Thus they will be useful for assessing the construction impacts.
[Note: Upstream water quality can be affected during flooding. This situation is not covered in
general water quality assessment].
Table 5.5 - Water Quality Sampling Locations for Construction Phase
Type of Water- Water-body Sampling Locations Parametersbody ID
A W1 300m upstream of centerline of the trace COD
BOD
600m downstream of centerline of theTSS
trace Turbidity
Color
pH
Colour
Oil andA W11 200m upstream of centerline of the trace Grease
Nitrate -N
trace Phosphate
5.5.1.5 Frequency of Monitoring
8/14/2019 Hydraulic Design - Scan Doc.docx
20/36
Worst water quality situations in the water-bodies identified in Table 5.1 can occur at times
when (a) significant runoff is generated when -the streams/canals/rivers are in low flow
conditions during seasonal dry period or due to irrigation controls, (b) significant runoff
generated after a long dry spell. As these conditions occur in an ad hoc manner, is not
possible to fix an exact time for monitoring where the intention is to ascertain the worst
water quality situation. Thus it is useful that timing of sampling to be determined by those
responsible based on their judgment. However by considering the climatic data reported in
Section 5.3.2 it is proposed to include minimum of five samples per year on following basis.
(i) One sample at each sampling location in January or February immediately after a
sizable storm event.
(ii) One sample at each sampling location in April after a sizable storm event
(iii) One sample at each sampling location in May
(iv) One sample at each sampling location in August after a sizable storm event
(v) One sample at each sampling location in October or November
5.5.2 Operational Phase
5.5.2.1 Nature of Operational Phase
Operational phase water quality pollution is primarily NPS pollution. In this phase long-term
impacts are also an important consideration as heavy metals and other chemicals including
petroleum based products are also a concern in this phase. Nevertheless significant long-term
effects, such as due to bio-accumulation are not expected in here. This is because substantial
rains during May and then in October-November period has high potential for flushing out
pollutants with less opportunity for long-term accumulation. As the water-bodies of concern are
flowing water-bodies chances of such accumulation is reduced further.
5.5.2.2 Water Quality Parameters proposed for Monitoring
Detailed list of pollutants entering the runoff from roads/highways under operation are provided
by the USEPA (1997). These mainly include: (a) particulate matter, (b) N and P from fertilizer
and pesticides, if maintenance of turf is part of the operation, (c) verity of heavy metals from
ware and tare of tires, combustion products, etc (d) oil and petroleum products due to spilling
(e) pathogens from animal excreta and rest areas. It is not practical and economical for the
water quality monitoring program to include all th,e individual pollutants. Thus the following set
8/14/2019 Hydraulic Design - Scan Doc.docx
21/36
of waterc.
quality parameters are proposed for water quality monitoring during operations, which can give
the picture of general water quality status.
Turbidity
pH
COD
TSS
Kjeldahl-N
Phosphate-P
Copper
Zin
8/14/2019 Hydraulic Design - Scan Doc.docx
22/36
5.5.2.3 Sampling Locations
Category B water-bodies (Section 5.5.1.2) are less important during operation phase as water is
not in direct contact with humans. Therefore only Category A water-bodies are proposed for the
monitoring program in this phase. Water-body proposed for the sampling program during operationis WQ1. Sampling location is defined in Table 5.6 below.
Table 5.6 -Water Quality Sampling Locations for Operational
300m upstream of centerline of the trace
600m downstream of centerline of the trace
5.5.2.4 Frequency of Monitoring
During the operational phase "first flush" in general results highest pollution concentrations in the runoff.
First flush means rainfall caused runoff after a dry period. Such events under low flow conditions usually
result relatively high pollution concentrations. On the other hand pollution concentration becomes less
prominent during heavy rain period due to dilution by increased flow. Accordingly following monitoring
schedule is proposed for operational phase, (i) One sample at each sampling location in January or
February immediately after a sizable storm event.
(ii) One sample at each sampling location in April after a sizable storm event (iii) One sample
at each sampling location in August after a sizable storm event (iv) One sample at each
sampling location in October or November
5.6 Baseline Conditions
Baseline water quality reflects the situation before the construction of the expressway. Baseline studyincludes two water-bodies selected for monitoring program under construction phase. The two water-bodies
are WQ1 and WQ11 {Table 5.1). Table 5.7 provides the details of the baseline water quality plan.
Table 5.7 - Water Quality Sampling Locations for Baseline Study
Type of
Water-body
Water-body ID Sampling Locations Parameters
A W1 600m downstream of centerline of the trace COD BOD
Water-body
ID
Sampling Locations
W1
8/14/2019 Hydraulic Design - Scan Doc.docx
23/36
A W11 600m downstream of centerline of the trace TSS
Turbidity
Color
pH
Colour
,,. Oil and Grease
Nitrate -N
Phosphate
;-*. Copper
. " Zinc
The water quality measurements during baseline study shall reflect the same flow or hydrologic conditions
under which the sampling was carried out during construction and operational phases. Thus sampling
frequency (time frame) for baselines study is set as follows, (i) One sample at each sampling location in
January or February immediately after a sizable storm event.
(ii) One sample at each sampling location in April after a sizable storm event (iii) One sample
at each sampling location in the month of May (iv) One sample at each sampling location in
August after a sizable storm event (v) One sample at each sampling location in October or
November
One set of data is unlikely to provide us the general water quality picture for baseline conditions. For this
purpose at least few years of data would be required. However, in reality water quality data of such length
and coverage are often not available. It is recommended to commence the baseline water quality data
collection as early as possible to collect a reasonably long data set to develop sufficiently accurate picture of
water quality before the project. In absence of such possibility it is necessary to use other historical water
quality data to generate the information required.
8/14/2019 Hydraulic Design - Scan Doc.docx
24/36
8/14/2019 Hydraulic Design - Scan Doc.docx
25/36
6.0 Recommendations
1. The drainage openings for small streams, Irrigation canals have been designed considering once in
fifty year flood situation.i.e. fifty year return period. In the design future development of area which
will increase the impervious area and the runoff volume has been considered. However with thepast experience climate changes and the percentage of land converting to developments have
been taken in to account.
2. Since the proposed highway trace passes through the low-lying areas and hilly areas it is
recommended to construct the cross drainage structures to minimize the effect of backwater
created by rising flood levels. The minimum sizes of Culverts across the proposed alignment are
included in table 4.1. Also it should be ensured that there will not be any settlements of culverts to
avoid adverse environmental impacts due to stagnation of water.
3. It is observed that the present uncertainty related to climate change which links to flood damage.
Therefore It is suggested to minimize the filling which causes adverse environment effect by
introducing Viaduct sections wherever necessary. Also natural water paths should not be disturbed
and should be improved.
4. If any changes are suggested using viaduct sections in your design sofit levels of those and location
of piers should be brought to the notice of SLLRDC for rechecking.
5. The outlet of all the proposed culvert/bridge crossings should be dredged and connected to the
nearby streams. The inlets of the same should be cleared about 500m upstream. These drainage
connections should be established before filling of embankment.
6. All drainage structures have been provided for cross drainage only. If additional structures are
needed for irrigation purposes they should be additionally provided.
7. It is desirable to discuss the locations of the proposed drainage crossings with Irrigation
Department, and Department of Agrarian Development Services and farmers' organizations. If anychanges are suggested those should be brought to the notice of SILRDC for rechecking.
8/14/2019 Hydraulic Design - Scan Doc.docx
26/36
8. The toe drains and other drainage canals in the vicinity of the road along the expressway should be
established as proposed in the Table 4.3.
9. Prior approval for the proposed bridges across the Kuda oya should be obtained from Department of
Irrigation.
10. Canal banks which already collapsed should be protected using gabions at least 200m both sides
(U/S and D/S) of the Canals where proposed culverts are located.
11. Canals should be dredged and kept to a desirable bed width. Necessary other maintenance should
be carried out through the responsible institution simultaneously at least 500m both sides (U/S and
D/S) of the Canais where proposed culverts are located.
12. The distance proposed for downstream measurement of water quality is for the purpose of providing
adequate mixing of pollutants with the stream flow. Also Upstream measurement is aimed at
obtaining the undisturbed picture during measurements.
13. The water quality monitoring plan to be implemented in three phases such as baseline (before the
project and existing .status), construction phase and operational phase.
14. Proper sample preservation methods are required. Therefore Sampling and testing should be carried
out by recognized institution.
15. Analytical methods use for water quality monitoring should be the standard methods accepted in Sri
Lanka.
8/14/2019 Hydraulic Design - Scan Doc.docx
27/36
Bibliography
(i) Design of Irrigation head works for Small Catchments,2ndEdition (Revised) ,AJ.P.Ponrajah,lrrigation Department Colombo, May 1984
(ii) Technical paper of towards more efficient hydraulic and hydrological Design of Cross drainagesstructures using new developed Intensity Duration Frequency Equations by D.G.L. RanatungaFormer Head Hydrology Division Irrigation Department.
(iii) Applied hydrology, International Edition, 1988 by Ven Te Chow.
(iv) Hydrological Study for Colombo-Kandy Alternate Highway Chainage from 0+000 km to25+000 km
(v) Ambient Water Quality Guidelines, Central Environmental Authority, 2003
(vi) Controlling Nonpoint Source Runoff Pollution from Roads, Highways and Bridges.
Washington, D.C.: Office of Water, U.S. Environmental Protection Agency, 1995.
(vii) Environmental Impact Assessment Report; Colombo-Kandy Alternate Highway Project;2003.
(viii) Sources and Mitigation of Highway Runoff Pollutants; Federal Highway Administration;Washington, D.C., 1984.
(ix) Statistical Methods for Environmental Pollution Monitoring; R.O, Gilbert; 1987.
8/14/2019 Hydraulic Design - Scan Doc.docx
28/36
Annex (B.1): Hydrological and Hydraulic Calculation for Drainage Opening Sizes
Culvert ID
(Chainage)
Total
Catch m
ent Area
(ha)
Length of
Longest
water
path (m)
Runoff
Coeffici
ent
Time of
Concent
ration
Tc(min)
Rainfall
Intensity
(mm/hr)
SOyr
Discharge
(m3/sec)
SOyr
slope Water
Depth
(m)
Proposed Size of
Structure
25+245 284.37 2080 0.40 90.82 97.89 30.93 0.0006 1.50 10.00mx2.00m
25+367 20.22 1101 0.40 55.14 127.07 2.85 0.0020 1.00 1.50mx1.50m
25+565 90.05 1255 0.40 60.75 121.30 12.14 0.0010 1.00 6.25mx1.50m
25+947 100.86 1348 0.40 64.14 118.08 13.23 0.0010 1.00 6.50mx1.50m
26+180 20.08 873 0.40 46.82 136.77 3.05 0.0010 1.00 2.00mx1.50m
26+550 25.18 738 0.40 41.90 143.30 4.01 0.0010 1.00 3.00mx1.50m
27+308 57.39 1089 0.40 54.70 127.54 8.13 0.0010 1.00 4.50mxl50m
27+481 8.39 449 0.40 31.37 159.78 1.49 0.0010 1.00 1.50mx1.50m
27+948 46.67 966 0.40 50.21 132.63 6.88 0.0010 1.00 4.00mx1.50m
28+400 ! 35.09 654 0.40 38.84 147.71 5.76 0.0010 1.00 1.75mx1.50m
28+500 J 1.75mx1.50m
28+885 26.36 718 0.40 41.17 144.32 4.23 0.0015 1.00 2.25mx1.50m29+520 53.06 925 0.40 48.72 134.42 7.92 0.0010 1.00 4.25mx1.50m
30+036 26.64 780 0.40 43.43 141.20 4.18 0.0015 1.00 2.50mx1.50m
30+330 34.72 1069 0.40 53.97 128.34 4.95 0.0015 1.00 2.50mxl50m
31+156 -i 82.94 936 0.40 49.12 133.94 12.34 0.0010 1.00 3.50mx1.50m
31+240 J 3.50mx1.50m
31+923 -, 60.75 625 0.40 37.78 149.30 10.08 0.0004 1.00 1.50mxl50m
32+000 I 3.25mx1.50m
32+088 | 1.50mx1.50m
32+235 J 1.75mx1.50m
32+665 297.15 2751 0.40 115.28 84.87 28.02 0.0005 1.50 10.00mx2.00m
32+985 223.45 2423 0.40 103.33 90.74 22.53 0.0005 1.50 8.50mx2.00m33+390 i 36.02 802 0.40 44.24 140.12 5.61 0.0015 1.00 1.50mx 1.50m
33+500 J 1.50mx1.50m
33+858 1 , 84.15 979 0.40 50.69 132.07 12.35 0.0005 1.00 2.75mx1.50m
33+936 6.75mx1.50m
34+913 14.09 435 0.40 30.86 160.69 2.52 0.0010 1.00 3.50mx2.50m
35+358 -i 202.54 1884 0.40 83.68 102.55 23.08 0.0007 1.00 4.25mx1.50m
35+410 4.50mx1.50m
35+460 J 4.25mx1.50m
35+615 ~\ 134.31 2044 0.40 89.51 98.72 14.73 0.0010 1.00 4.00mx1.50m
35+730 J 4.00mx1.50m
36+323 -\ 53.10 1010 0.40 51.82 130.76 7.71 0.0010 1.00 2.25mx1.50m36+385 J 2.25mx1.50m
36+555 85m opening should be provided for Merigama-Pasyala Rd and Railway Track 85m Opening
36+608 4.54 849 0.40 45.95 137.89 0.70 0.0010 1.00 1.50mx1.50m
36+853 9.43 441 0.40 31.08 160.30 1.68 0.0010 1.00 1.50mx1.50m
37+250 15.12 565 0.40 35.60 152.70 2.57 0.0010 1.00 2.00mx1.50m
8/14/2019 Hydraulic Design - Scan Doc.docx
29/36
Culvert ID
(Chainage)
Total
Catchm
ent Area
(ha)
Length of
Longest
water
path (m)
Runoff
Coeffici
ent
Time of
Concentr
ation
Tc(min)
Rainfall
Intensity
(mm/hr)
50yr
Discharge
(m3/sec)
SOyr
slope Water
Depth
(m)
Proposed Size of
Structure
37+522 56.11 1122 0.40 55.90 126.25 7.87 0.0010 1.00 4.25mx1 .50m
37+893 -i 456.45 3977 0.40 159.98 68.57 34.78 0.0008 1.00 9.00mx1.50m
38+001 J 9.00mx1.50m
38+400 16.58 469 0.40 32.10 158.51 2.92 0.0010 1.00 2.00mx1.50m
38+676 45.02 1662 0.40 75.59 108.42 5.42 0.0010 1.00 3.25mx1.50m
38+943 38.00 1347 0.40 64.10 118.11 4.99 0.0010 1.00 3.00mx1.50m
39+195 48.55 1128 0.40 56.12 126.02 6.80 0.0010 1.00 3.75mx1.50m
40+065 24.41 802 0.40 44.24 140.12 3.80 0.0010 1.00 2.50mx1.50m
40+630 52.94 1707 0.40 77.23 107.18 6.30 0.0010 1.00 3.50mx1.50m
40+815 45.74 1410 0.40 66.40 116.03 5.90 0.0010 1.00 3.50mx1 .50m
40+900 13.83 712 0.40 40.96 144.63 2.22 0.0010 1.00 1.75mx1.50m
41+070 15.07 575 0.40 35.96 152.13 2.55 0.0010 1.00 2.00mx1.50m
41+445 \ 1456.46 5049 0.40 199.06 58.90 95.32 0.0004 1.50 13.50mx2.00m
41+565 20.00mx2.00m
41+930 44.91 964 0.40 50.14 132.72 6.62 0.0010 1.00 3.75mx1.50m
42+580 40.83 976 0.40 50.58 132.20 6.00 0.0010 1.00 3.50mx1.50m
42+925 34.31 1064 0.40 53.79 128.54 4.90 0.0010 1.00 3.00mx1.50m
43+545 1 193.10 1539 0.40 71.10 112.00 24.03 0.0008 1.00 9.00mx1.50m
43+840 ^ 3.25mx1.50m
43+980 26.35 1472 0.40 68.66 ,114.06 3.34 0.0010 1.00 2.25mx1 .50m
44+120 31.66 1332 0.40 63.56 118.62 4.17 0.0010 1.00 2.75mx1 .50m
44+250 57.71 1366 0.40 64.80 117.48 7.53 0.0009 1.00 4.25mx1.50m
44+490 10.44 475 0.40 32.32 158.14 1.83 0.0010 1.00 1.50mx1.50m
44+673 14.18 416 0.40 30.16 161.93 2.55 0.0010 1.00 2.00mx1.50m
45+135 17.40 501 0.40 33.26 156.53 3.03 0.0010 -1.00 2.00mx1 .50m
45+666 9.19 473 0.40 32.24 158.26 1.62 0.0010 1.00 1.50mx1.50m
46+032 12.31 528 0.40 34.25 154.89 2.12 0.0010 1.00 1.75mx1.50m
46+476 16.63 469 0.40 32.10 158.51 2.93 0.0010 1.00 2.00mx1.50m
46+892 10.30 450 0.40 31.40 159.72 1.83 0.0010 1.00 1.50mx1.50m
47+451 1 267.06 1630 0.40 74.42 109.33 32.44 0.0009 1.00 9. 00m x 1.50m
47+557 -* 7.00mx1.50m
47+928 62.61 1255 0.40 60.75 121.30 8.44 0.0010 1.00 4.50mx1.50m
48+174 5057.04 13399 0.40 503.44 32.92 184.95 0.0040 3.50 32.00mx4.50m
8/14/2019 Hydraulic Design - Scan Doc.docx
30/36
Annex (B.2): Hydrological and Hydraulic Calculation for Drainage Opening Sizes for
Overpass and Underpass
Culvert ID
(Chainage)
lotai
Catchme
nt Areaha
i_engin
of
Longest
water
Runoff
Coeffici
ent
i ime or
Concentr
ationTc min
Kainran
Intensity
(mm/hr)50 r
uiscnarg
e
(m3/sec)50 r
slope
SWater
Depth
(m)
Proposed Size
of Structure
25+535 (LHS) 161.92 1838 0.40 82.00 103.71 18.66 0.001 1.00 9.25mxl.50m
25+535(RHS) 2.16 202 0.40 22.36 177.47 0.43 0.001 1.00 l.OOmxl.SOm
26+394 (LHS) 25.18 830 0.40 45.26 138.78 3.88 0.001 1.00 2.50mxl.50m
26+394(RHS) 54.20 1063 0.40 53.75 128.58 7.74 0.001 1.00 4.25mxl.50m
27+451 (LHS) 87.68 1215 0.40 59.29 122.75 11.96 0.001 1.00 6.00mxl.50m
27+451 (RHS) 11.87 893 0.40 47.55 135.86 1.79 0.001 1.00 l.SOmxl.SOm
27+980 (LHS) 5.40 347 0.40 27.65 166.61 1.00 0.001 1.00 l.OOmxl.SOm
27+980(RHS) 15.67 821 0.40 44.93 139.21 2.42 0.001 1.00 1.75mxl.50m
28+720 (LHS) 1m minimum openings should be provided . l.OOmxl.SOm
28+720(RHS)l.OOmxl.SOm
29+210 (LHS) l.OOmxl.SOm
29+21 0(RHS) l.OOmxl.SOm
29+707 (LHS) 0.58 94 0.40 18.43 186.59 0.12 0.001 1.00 l.OOmxl.SOm
29+707(RHS) 5.11 515 0.40 33.77 155.67 0.88 0.001 1.00 l.OOmxl.SOm
30+520 (LHS) 4.15 355 0.40 27.94 166.06 0.77 0.001 1.00 l.OOmxl.SOm
30+520(RHS) 8.89 728 0.40 41.54 143.81 1.42 0.001 1.00 1.25mxl.50m
31 +040 (LHS) 1.83 180 0.40 21.56 179.25 0.36 0.001 1.00 l.OOmxl.SOm
31+040(RHS) 6.48 762 0.40 42.78 142.09 1.02 0.0010 1.00 l.OOmxl.SOm
31 +395 (LHS) 9.06 539 0.40 34.65 154.23 1.55 0.001 1.00 1.25mxl.50m
31+395(RHS) 18.83 776 0.40 43.29 141.40 2.96 0.001 1.00 2.00mxl.50m
31+830 (LHS) 9.08 663 0.40 39.17 147.22 1.49 0.001 1.00 1.25mxl.50m
31+830(RHS) 10.10 1712 0.40 77.41 107.04 1.20 0.001 1.00 1.25mxl.50m
32+839 (LHS) 127.08 2627 0.40 110.76 86.99 12.28 0.001 1.00 6.25mxl.50m
32+839(RHS) 255.40 2571 0.40 108.72 87.99 24.97 0.001 1.00 13.00mxl.50m
33+490 (LHS) 1.93 204 0.40 22.44 177.31 0.38 0.001 1.00 l.OOmxl.SOm
33+490(RHS) 10.63 697 0.40 40.41 145.42 1.72 0.001 1.00 l.SOmxl.SOm
37+579 (LHS) 4.62 359 0.40 28.09 165.78 0.85 0.001 1.00 l.OOmxl.SOm
37+579(RHS) 1.11 155 0.40 20.65 181.32 0.22 0.001 1.00 l.OOmxl.SOm
39+1 49 (LHS) 6.89 627 0.40 37.86 149.19 1.14 0.001 1.00 l.OOmxl.SOm
39+149(RHS) 7.99 412 0.40 30.02 162.19 1.44 0.001 1.00 1.25mxl.50m
40+510 (LHS) 20.74 732 0.40 41.68 143.61 3.31 0.001 1.00 2.25mxl.50m
40+51 0(RHS) 11.71 443 0.40 31.15 160,17 2.08 0.001 1.00 1.75mxl.50m
40+885 (LHS) 9.25 425 0.40 30.49 161.34 1.66 0.001 1.00 l.SOmxl.SOm
40+885(RHS) 119.09 1586 0.40 72.82 110.60 14.64 0.001 1.00 7.50mxl.50m
41+085 (LHS) 0.56 95 0.40 18.46 186.50 0.12 0.001 1.00 l.OOmxl.SOm
41+085(RHS) 14.56 778.00 0.40 43.36 141.30 2.29 0.001 1.00 1.75mx1.50m
41+620 (LHS) 19.31 761 0.40 42.74 142.14 3.05 0.001 1.00 2.00mxl.50m
41+620(RHS) 18.02 946 0.40 49.49 133.50 2.67 0.001 1.00 2.00mxl.50m
8/14/2019 Hydraulic Design - Scan Doc.docx
31/36
Culvert ID
(Chainage)lotalCatchme
nt Area
ha
Length
of
Longest
water
Runoff
Coeffici
ent
i ime or
Concentr
ation
Tc min
Kamtall
Intensity(mm/hr)
50 r
Uischarg
e
(m3/sec)
50 r
slope
SWaterDepth(m)
Proposed Size
of Structure
42+595 (LHS) 5.59 458 0.40 31.70 159.21 0.99 0.001 1.00 l.OOmxl.SOm
42+595(RHS) 2.37 211 0-40 22.69 176.75 0.47 0.001 1.00 l.OOmxl.SOm
43+616 (LHS) 17.06 686 0.40 40.01 145.99 2.77 0.001 1.00 2.00mxl.50m
43+61 6(RHS) 85.09 928 0.40 48.83 134.29 12.70 0.0009 1.00 7.00mxl.50m
44+228 (LHS) 4.99 374 0.40 28.63 164.75 0.91 0.001 1.00 l.OOmxl.SOm
44+228(RHS) 6.31 392 0.40 29.29 163.53 1.15 0.001 1.00 l.OOmxl.SOm
44+444 (LHS) 4.36 457 0.40 31.66 159.27 0.77 0.001 1.00 l.OOmxl.SOm
44+444(RHS) 1.29 171 0.40 21.23 179.99 0.26 0.001 1.00 l.OOmxl.SOm
45+1 54 (LHS) 0.38 113 0.40 19.12 184.91 0.08 0.001 1.00 l.OOmxl.SOm
45+154 (RHS) 6.10 1295 0.40 62.21 119.89 0.81 0.001 1.00 l.OOmxl.SOm
45+464 (LHS) 1 m minimum openings should be provided . l.OOmxl.SOm45+464(RHS) l.OOmxl.SOm
45+802 (LHS) l.OOmxl.SOm45+802(RHS) l.OOmxl.SOm
46+488 (LHS) 56.71 751 0.40 42.38 142.64 8.99 0.001 1.00 4.75mxl.50m
46+488(RHS) 2.14 370 0.40 28.49 165.02 0.39 0.001 1.00 l.OOmxl.SOm
46+91 8 (LHS) 1.09 185 0.40 21.74 178.84 0.22 0.001 1.00 l.OOmxl.SOm
46+91 8(RHS) 5.87 442 0.40 31.11 160.23 1.05 0.001 1.00 l.OOmxl.SOm
47+51 2 (LHS) 5.79 380 0.40 28.85 164.34 1.06 0.001 1.00 l.OOmxl.SOm
47+51 2(RHS) 2.71 273 0.40 24.95 171.97 0.52 0.001 1.00 l.OOmxl.SOm
Following details are enclosed into Annex (C);
1). Details of culverts "'
2). Maps showing catchment areas
3). Colombo Kandy alternate Expressway plan and longitudinal maps
4). Longitudinal sections and Cross sections at Chainage 33+368 km, 37+8.79 km 38+001 km and
48+174 km
8/14/2019 Hydraulic Design - Scan Doc.docx
32/36
8/14/2019 Hydraulic Design - Scan Doc.docx
33/36
8/14/2019 Hydraulic Design - Scan Doc.docx
34/36
8/14/2019 Hydraulic Design - Scan Doc.docx
35/36
8/14/2019 Hydraulic Design - Scan Doc.docx
36/36