saskatchewan avenue crossing replacement at sturgeon creek environmental assessment report ·...

Saskatchewan Avenue Crossing Replacement at Sturgeon Creek Environmental Assessment Report

APPENDIX F HYDROLOGIC AND HYDRAULIC ASSESSMENT

734-1600070700-REP-V0001-00

Bruce Harding Consulting Ltd

Sturgeon Creek at Saskatchewan Avenue Crossing Replacement Hydrologic and Hydraulic Assessment

May 2, 2017

Rev 2

City of Winnipeg Public Works


Sturgeon Creek at Saskatchewan Avenue Crossing Replacement Hydrologic and Hydraulic Assessment

Prepared by: Bruce Harding, P.Eng.

May 2017

Rev 2

City of Winnipeg Public Works


Table of Contents

1 Introduction ....................................................................................................... 1

2 Hydrology .......................................................................................................... 2

2.1 Flood Hydrology................................................................................................ 2

2.2 Stage-Discharge Relationship ......................................................................... 3

2.3 Fish Passage Discharge .................................................................................. 3

2.4 Navigation Discharge ....................................................................................... 4

3 Hydraulic Assessment – Existing Conditions ............................................... 5

4 Hydraulic Assessment – Proposed Crossing Replacement ......................... 7

4.1 General ............................................................................................................... 7

4.2 Hydraulic and Regulatory Design Criteria ..................................................... 7

4.3 Replacement Structure .................................................................................... 8

4.4 Erosion Control Measures ............................................................................. 13

5 Ice Loadings ..................................................................................................... 15

5.1 Dynamic Ice Forces ........................................................................................ 15

5.2 Static Ice Forces ............................................................................................. 16

5.3 Ice Jam Forces ................................................................................................ 16

5.4 Ice Adhesion Forces ....................................................................................... 17

6 Other Considerations ...................................................................................... 18

Figures

Appendix A – Fish Habitat Classification Map

Appendix B – Photographs


1 Introduction

This report summarizes the results of our hydrologic analysis and hydraulic sizing for a

replacement crossing of Sturgeon Creek by Saskatchewan Avenue in the City of Winnipeg.

The location of the site is indicated on Figure 1. The existing double cell concrete box culvert

has reached the end of its service life and requires replacement.

Pertinent features of the project area are as follows:

Municipality - City of Winnipeg

Watercourse - Sturgeon Creek

Stream Order - 4th order

Flow Direction - Southeast

Designation of Drain Map - No. 26

UTM Coordinates - 622285E, 5528935N (Zone 14)

Fisheries and Oceans Canada has indicated that this reach of Sturgeon Creek near the site

has Type A – complex habitat with indicator species1 (refer to appended map) , therefore the

design of the proposed crossings will adhere to the Manitoba Stream Crossing Guidelines2

with respect to providing fish passage.

Transport Canada has indicated that Sturgeon Creek is navigable3; therefore the proposed

crossing will be subject to the specific requirements for vertical and horizontal clearances

under the Navigable Water Protection Act.

The existing box culvert crossing has been proposed to be replaced with a bridge structure on

the same alignment. Additional details with respect to the hydrologic assessment and the

hydraulic sizing of the replacement structure options are summarized in the following sections.

1 “Fish Habitat Classification for Manitoba Agricultural Watersheds”, Map 062H14, March 2008, Fisheries and Oceans Canada.

2 “Manitoba Stream Crossing Guidelines for the Protection of Fish and Fish Habitat”, Manitoba Natural Resources –Fisheries

Department and the Canadian Department of Fisheries and Oceans, May 1996.

3 “Application for approval of Sturgeon Creek Culverts and Omand’s Creek Overpass Crossing, Province of Manitoba”, Letter

from Matt Klaverkamp, Transport Canada to Don McRitchie, MIT dated September 2, 2009. Transport Canada File No.

8200-09-10644/10645/10646 and 8200-09-10687


2 Hydrology

2.1 Flood Hydrology

The contributing drainage area of Sturgeon Creek to the project site has been delineated as

approximately 556 km2 from the watershed map. A streamflow gauge had been operated by

Water Survey of Canada on Sturgeon Creek (Sturgeon Creek near Perimeter Highway – WSC

05MJ011) in upstream of thee project site for the period from 1978 to 1994. The flood

hydrology derived for this streamflow gauge was selected to reflect the hydrological conditions

of Sturgeon Creek within the project site.

The flood hydrology and regional discharge coefficients for the Sturgeon Creek gauge

05MJ011 were developed by Manitoba Water Stewardship (MWS) utilizing recorded and

correlated data for Sturgeon Creek. MWS utilized a downstream streamflow gauge on

Sturgeon Creek (Sturgeon Creek at St James – 05MJ004) with a longer streamflow record to

extend the data set for the upstream gauge through correlation. The historical data from the

downstream gauge was correlated with the overlapping data from the upstream gauge site

record enabling the extension of the streamflow records at the upstream site for years when

data was not recorded. Table 1 summarizes the regional discharge coefficients for Sturgeon

Creek. The flood hydrology for Sturgeon Creek at Saskatchewan Avenue is summarized in

Table 1.

Table 1

Sturgeon Creek at Saskatchewan Avenue Crossing

Flood Hydrology – Regional Coefficients and Flood Estimates

Probability Regional Discharge Coefficient

Sturgeon Creek near Perimeter

Highway

Gauge 05MJ011

Drainage Area = 538 km2

Flood Estimate

Sturgeon Creek at Saskatchewan

Avenue

Drainage Area = 556 km2

(m3/s)

50% 0.175 22

20% 0.333 42

10% 0.423 53

5% 0.494 62

2% 0.566 71

1% 0.606 76

* - from Regional Flood Formulae Tables, Zone 3, Manitoba Water Stewardship, April 2010, n=0.765

The 1% flood discharge of 76 m3/s will be selected as the design discharge for the crossing

replacement.


A streamflow gauge has been operated by Water Survey of Canada just downstream of the

Saskatchewan crossing at the Sturgeon Road bridge (Sturgeon Creek at St James –

05MJ004). This downstream streamflow gauge on Sturgeon Creek was not used to develop

site hydrology for the project as Water Survey of Canada has recently revised the stage-

discharge relationship applied at that location which may have resulted in the overestimation

of discharge, particularly under high flows. The revision was in response to changes in the

technique employed at this location to measure discharge. As indicated, the historical

discharges noted at this location are slightly overestimated which is confirmed by a correlation

assessment between the two Sturgeon Creek gauges. The historical discharge data at this

downstream gauge may be reduced by a factor of approximately 0.8 depending on the

correction factor adopted. It is interesting to note that there is only a 30 km2 increase in

drainage area between the upstream (538 km2) and downstream (568 km2) gauges however

the peak flows are much higher at the downstream gauge. With the adjustment factor applied,

the observed peaks and the derived flood hydrology are comparable. Note that this identified

difference will not affect the extension of the upstream gauge data set as the correlation

technique would have taken the adjustment factor into account.

2.2 Stage-Discharge Relationship

As indicated, Water Survey of Canada has operated a streamflow gauge downstream of

Saskatchewan Avenue at Sturgeon Road (Gauge 05MJ004). The stage-discharge relationship

for this gauge has been revised and would be indicative of current conditions on Sturgeon

Creek. The data used in the derivation of the stage-discharge relationship would reflect

discharges following the change in discharge metering technique at this location. The stage-

discharge relationship at the downstream gauge (05MJ004), as presented on Figure 2, will be

used to aid in model calibration.

2.3 Fish Passage Discharge

If a watercourse is considered fish habitat, then a crossing of the watercourse should not

restrict upstream fish passage during a spawning migration period for flows up to a specified

fish passage discharge. As indicated, Sturgeon Creek within this reach is considered fish

habitat, therefore the proposed crossings will be designed to enable upstream fish passage.

The spring migration period is considered the critical period for this site on the basis of the

large bodied freshwater species (northern pike, sucker, etc.) that may exist within the creek.

The spawning migration period was assumed to extend from April 1 to May 31 (Table 4 of the

fisheries guidelines).


The fish passage discharge is estimated from the results of frequency analyses that consider

the streamflow for each year that corresponds to the largest streamflow that is equalled or

exceeded for 3 consecutive days during the spawning migration period. The 3 day delay

discharge with a 10% probability (3DQ10) of exceedence is typically selected as the fish

passage discharge. This analysis requires daily streamflow records from which to derive this

discharge.

The 3QD10 discharge coefficient, estimated as 0.389 by MWS, was derived from an analysis

of streamflow records for the Sturgeon Creek near Perimeter Highway gauge (05MJ011)

during the spring migration period. The 3DQ10 discharge for Sturgeon Creek at the

Saskatchewan Avenue crossing has been estimated as 49 m3/s.

2.4 Navigation Discharge

As indicated, Sturgeon Creek is considered navigable, therefore sufficient vertical and

horizontal clearance must be provided through the structure openings to ensure the safe

passage of watercraft. The required vertical clearance beneath a structure is referenced from

a water level based on a specific probability of exceedence. The water level at the 50%

discharge will be selected for this assessment. The clearances will be assessed to ensure that

the specific requirements have been met.


3 Hydraulic Assessment – Existing Conditions

The existing Saskatchewan Avenue crossing of Sturgeon Creek is a double 2.4 high by 2.4

wide by approximately 21 m long cast-in-place concrete box culvert. The culvert is skewed

approximately 25o and includes extensive upstream wingwalls and concrete retaining walls

between the culvert inlet and the CPR Bridge. The existing crossing has reached the end of its

service life and requires replacement. Additionally it must be noted that the existing culvert

crossing is undersized resulting in the frequent surcharge of river levels and the risk of

overtopping of Saskatchewan Avenue for flood events in excess of a 5% discharge event.

Sturgeon Creek within the study reach is for the most part a natural channel; however the

creek has been heavily impacted by urban development and transportation infrastructure. The

channel grade through the study reach is approximately 0.08%. The channel bottom is

predominately gravel, likely with the channel bottom close to the top of the till layer. The study

reach includes four low height rock riffles which were placed in the river to provide and create

habitat diversity and to maintain water depth during periods of low flow. The rock riffles

however are quickly drown out by higher flows and do not backwater the creek during flood

passage. Photographs of Sturgeon Creek and the Saskatchewan Avenue crossing are

appended for reference.

A hydraulic assessment of Sturgeon Creek within the project area was undertaken to

determine the hydraulic characteristics of the waterway and downstream structures which

influence the hydraulics of the channel. An existing HEC- RAS model of Sturgeon Creek

previously developed for other hydraulic studies was used for the assessment. The steady-

state backwater model of Sturgeon Creek within the study reach was developed using the

US Army Corps of Engineers River Analysis System HEC-RAS model. The HEC-RAS model

is a one-dimensional backwater model, which is considered to be the universal standard for

computing steady-state water surface profiles. The backwater model extends upstream

approximately 8000 m from the Portage Avenue crossing and includes the Grants Mill Dam,

Sturgeon Creek Bridge, Ness Avenue Bridge (new) Crossing, Hamilton Avenue Bridge,

Saskatchewan Avenue Culvert Crossing, CPR Culvert Crossing, Summit Road Bridge and the

two new Centreport Crossings. The existing backwater model was assembled from cross-

sections, channel profiles and details of the crossing structures surveyed by Denis Andrews

Consulting (2002), City of Winnipeg (2005) and MMM Group (2009). The model was further

updated with additional detailed surveys in the Ness Avenue reach by GDS Surveys

(August 2014) and the Saskatchewan Avenue reach by GDS Surveys (April 2016).


The backwater model has been developed to the level of detail required to estimate the

relative effect of the proposed replacement crossing at Saskatchewan Avenue. In general the

model has not been calibrated over the entire modelled length, however the stage-discharge

relationship at Sturgeon Road (WSC 05MJ004) was used for calibration in the lower reach

closer to Ness Avenue. The hydraulic parameters required for calibration within this lower

reach, such as channel roughness, are within the standard range expected for Sturgeon

Creek. The results of the calibration with the stage-discharge relationship are presented on

Figure 2.

The estimated water surface profiles for Sturgeon Creek within the study area under existing

conditions (circa April 2016), with the existing Saskatchewan Avenue box culvert crossing are

shown on Figure 3. The existing conditions backwater model assumes that the Ness Avenue

Bridge, which is under construction, has been completed. Table 2 summarizes the hydraulic

assessment for the existing Saskatchewan Avenue crossing.

Table 2


Hydraulic Summary for Existing Box Culvert Probability Discharge

(m3/s)

Water Level

Downstream

of Crossing

(m)

Water Level

Upstream

of Crossing

(m)

Headloss

(m)

Clearance to

Underside of

Soffit *

(m)

Culvert

Velocities

(m/s)

50% 22 233.37 233.56 0.21 0.64 submerged 1.85

20% 42 233.89 234.67 0.81 1.75 submerged 3.53

10% 53 234.12 235.41 1.3 2.49 submerged 4.45

5% 62 234.30 235.98 1.68 ** 3.06 submerged 5.10 **

2% 71 234.46 236.20 1.73 ** 3.28 submerged 5.29 **

1% 76 234.54 236.28 1.73 ** 3.36 submerged 5.38 **

3DQ10 49 234.04 235.13 1.11 2.21 submerged 4.12

* - underside of soffit (existing box culvert) at approximately el 232.92 m

** - Saskatchewan Avenue overtopped


4 Hydraulic Assessment – Proposed Crossing Replacement

4.1 General

The proposed replacement crossing will be a bridge structure due to the site geometry and the

flow conditions observed at this location. As proposed, the replacement structures will be

either clear span bridges or a 3 span bridges with the centre span clearing the main channel

of Sturgeon Creek.

4.2 Hydraulic and Regulatory Design Criteria

The hydraulic design criterion selected for the replacement crossing is as follows:

Design discharge – 1%.

Maximum headloss of 0.3 m during the passage of the design discharge.

Bridge opening velocities less than 1.5 m/s for discharges up to the design discharge

Underside of girder elevation to remain minimum of 0.3 m above water surface during

passage of design discharge.

Sturgeon Creek has been judged to be navigable by Transport Canada; therefore any

proposed crossing will be subject to the specific requirements for vertical and horizontal

clearances under the Navigable Water Protection Act. The following vertical and horizontal

clearances for small watercraft (canoes, kayaks, etc.) were assumed to be provided:

Provide a minimum vertical clearance of 1.5 m from the underside of girder to the water

surface corresponding to the 50% (Q2) discharge.

Provide a minimum clear horizontal width of 3 m within the bridge opening at the water

surface corresponding to the 50% (Q2) discharge.

Bridge structures do not typically require the same strict limiting velocity requirements for fish

passage as those of culvert type structures. The shape of the bridge opening with sloping

banks at the abutments, provides lower velocity fringe zones to permit upstream fish passage.

As such, the requirement for limiting velocity is typically not applied except under extenuating

circumstances. On that basis, there are no concerns or design requirements with respect to

fish passage with a bridge structure at this location.


4.3 Replacement Structure

Four replacement structure options have been prepared including two three span bridge

options and two clear span bridge options. The options proposed are as follows:

Option 1 – Three Span Bridge

The proposed Option 1 replacement structure for this site is as follows:

Three span 36 m long bridge. The 36 m long bridge, as proposed by Tetra Tech

consists of 11 m long approach spans with a 14 m long centre span.

The proposed structure would be offset slightly west relative to the existing box culvert,

with the structure shifted south to accommodate the wider structure. A 20 degree

skew is proposed.

The proposed underside of girder elevation of 234.85 (minimum) has been selected to

provide approximately 0.3 m of clearance from the water surface profile during the

passage of the 1% design discharge.

The proposed replacement structure will require the removal of the original box culvert

and the excavation and armouring of the channel slopes. Channel skewed with bridge

at 20 degrees. The channel slopes (headslopes) beneath the bridge will be excavated

with a slope of 4:1 extending down from the abutments to the channel base. The

channel base and slopes would be armoured with a 0.675 m thickness of Class 450

rock placed over non-woven geotextile. The channel base would be reshaped with a

width of 6.0 m and a finished elevation of 231.2.

Channel reshaping and rock armour to extend 5 m upstream and downstream of the

outside faces of the replacement bridge structure.

All Class 450 rock to be well-graded, rounded, sound field stone or quarried rock with

the following gradation: 100% < 450 mm, 50% > 250 mm, and 80% > 150 mm. 30%

granular material by volume will be blended with the Class 350 rock prior to placement

in order to fill the interstitial space/voids within the rock. The granular will be clean

gravel or crushed rock with the following gradation: 100% <100 mm, 50% > 20mm and

80% > 3mm.

Refer to the detail sketches of the proposed bridge structure on Figures 4 and 5.

The backwater model of Sturgeon Creek was modified to incorporate the proposed bridge

replacement structure. The estimated water surface profiles for Sturgeon Creek with the

proposed replacement bridge structure are shown on Figure 6 while Table 3 summarizes the

hydraulic assessment.


Table 3


Hydraulic Summary for Option 1 - 36m long 3 span bridge Probability Discharge

(m3/s)

Water Level

Downstream

of Crossing

(m)

Water Level

Upstream

of Crossing

(m)

Headloss

(m)

Clearance to

Underside of

Girder *

(m)

Bridge

Opening

Velocities

(m/s)

50% 22 233.36 233.37 <0.05 1.48 0.75

20% 42 233.86 233.88 <0.05 0.97 1.05

10% 53 234.09 234.11 <0.05 0.74 1.15

5% 62 234.26 234.28 <0.05 0.57 1.25

2% 71 234.42 234.43 <0.05 0.42 1.35

1% 76 234.51 234.52 <0.05 0.33 1.4

3DQ10 49 234.01 234.02 <0.05 0.83 1.1

* - underside of girder at 234.85

Option 2 – Clear Span Bridge - Skewed


Clear span 32 m long bridge as proposed by Tetra Tech.



skew is proposed.



















80% > 3mm.






Table 4


Hydraulic Summary for Option 2 - 32m long clear span bridge - skewed Probability Discharge

(m3/s)

Water Level

Downstream

of Crossing

(m)

Water Level

Upstream

of Crossing

(m)

Headloss

(m)

Clearance to

Underside of

Girder *

(m)

Bridge

Opening

Velocities

(m/s)

50% 22 233.36 233.37 <0.05 1.48 0.7

20% 42 233.86 233.88 <0.05 0.97 1.0

10% 53 234.09 234.11 <0.05 0.74 1.15

5% 62 234.26 234.28 <0.05 0.57 1.2

2% 71 234.42 234.43 <0.05 0.42 1.3

1% 76 234.51 234.52 <0.05 0.33 1.35

3DQ10 49 234.01 234.02 <0.05 0.83 1.1


Option 3 – Clear Span Bridge - not skewed


Clear span 32 m long bridge as proposed by Tetra Tech.


with the structure shifted south to accommodate the wider structure. The channel

would be skewed relative to the road, but bridge would be built without skew.



















80% > 3mm.






Table 5


Hydraulic Summary for Option 3 - 32m long clear span bridge - unskewed Probability Discharge

(m3/s)

Water Level

Downstream

of Crossing

(m)

Water Level

Upstream

of Crossing

(m)

Headloss

(m)

Clearance to

Underside of

Girder *

(m)

Bridge

Opening

Velocities

(m/s)

50% 22 233.36 233.37 <0.05 1.48 0.7

20% 42 233.86 233.88 <0.05 0.97 1.0

10% 53 234.09 234.11 <0.05 0.74 1.15

5% 62 234.26 234.28 <0.05 0.57 1.2

2% 71 234.42 234.43 <0.05 0.42 1.3

1% 76 234.51 234.52 <0.05 0.33 1.35

3DQ10 49 234.01 234.02 <0.05 0.83 1.1



Option 4 – Three Span Bridge with Pathway


Three span 42 m long bridge. The 42 m long bridge, as proposed by Tetra Tech

consists of three 14 m long spans.



skew is proposed.


provide 2.5 m of clearance from the proposed pathway set at elevation 233.4. The

proposed pathway elevation was selected to be at the 50% water level within the

bridge opening. The criteria for the selection of the vertical clearance and path

elevation matches that used at the Ness Avenue crossing replacement.




with a 4:1 headslope on the west side and 3.5:1 on the east side (complete with 3.5 m

wide pathway), extending down from the abutments to the channel base. The channel

base and slopes would be armoured with a 0.675 m thickness of Class 450 rock

placed over non-woven geotextile. The channel base would be reshaped with a width

of 6.0 m and a finished elevation of 231.2.








80% > 3mm.







Table 6


Hydraulic Summary for Option 4 - 42m long 3 span bridge Probability Discharge

(m3/s)

Water Level

Downstream

of Crossing

(m)

Water Level

Upstream

of Crossing

(m)

Headloss

(m)

Clearance to

Underside of

Girder *

(m)

Bridge

Opening

Velocities

(m/s)

50% 22 233.36 233.37 <0.05 2.53 0.75

20% 42 233.86 233.88 <0.05 2.02 1.05

10% 53 234.09 234.11 <0.05 1.79 1.2

5% 62 234.26 234.28 <0.05 1.62 1.25

2% 71 234.42 234.43 <0.05 1.47 1.35

1% 76 234.51 234.52 <0.05 1.38 1.4

3DQ10 49 234.01 234.02 <0.05 1.88 1.15


4.4 Erosion Control Measures

CPR Railway Bridge

The replacement of the undersized Ness Avenue and Saskatchewan Avenue crossing will

have the benefit of reducing water levels within Sturgeon Creek upstream of Saskatchewan

Avenue. However, the lower water surface profile results in increased velocities within the

creek and the upstream CPR Bridge crossing. It was noted that the replacement of the

Saskatchewan Avenue crossing with a bridge (or other suitably sized crossing structure)

lowers water levels immediately downstream of the CPR Bridge by 1.75m at the 1% design

discharge. The reduction in water level results in the CPR Bridge opening velocities increasing

from the already high 3.0+ m/s to 4.0+ m/s at the 1% design discharge. This increase in

velocity will certainly raise the risk of scour and the possibility of structure undermining. This is

particularly important if the structure is founded only on shallow footings as opposed to piles.

It is understood however that as-built drawings of this structure do not exist to confirm

foundation type or what erosion protection measures presently exist, therefore options for

reinforcing the existing erosion protection must be investigated. Options for erosion protection

improvements and remediating the increase in bridge opening velocity are limited however,

and as such a certain level of scour risk and undermining at the CPR structure will remain.


It was noted during the survey that the entire CPR Bridge opening appears to be either rock

armoured or has a solid continuous slab bottom. Confirmation of the bridge opening base

material should be determined to allow the development of remedial erosion control measures.

It is understood that dewatering of the site to allow visual inspection or construction is not

possible or practical therefore only in-water probing using steel rods will have be utilized. If

the base is rock riprap, then an estimate of existing rock size/gradation will be required to

determine if the base material is adequate in size and thickness to withstand the increase in

velocity. If the base rock armouring is found to be deficient, then replacement of the rock base

with larger rock and possibly a lowered invert could be considered. However, if the base is

found to be a solid continuous slab (concrete or grouted limestone block) then the opening

itself should be adequate to resist the increase in velocity. Outside of the bridge opening, to at

least the limits of the wingwalls and where permitted by CPR, it is recommended that the

channel and slopes be excavated and replaced with a 1.5 m thickness of Class 600 angular

rock with finished channel bottom grade no higher than elevation 231.75.

Replacement Saskatchewan Avenue Bridge

The rock proposed for the replacement bridge structure at Saskatchewan Avenue is larger

than typically specified, with the rock size increased from Class 350 to Class 450. The

increase in channel velocities at the outlet of the CPR Bridge and the resultant turbulence

would necessitate the use of the larger rock to minimize scour potential. The alignment and

layout of the proposed Saskatchewan Avenue bridge has been selected to streamline the

channel and piers to reduce the effects of the higher velocity and turbulence. The close

proximity of the CPR Bridge poses challenges and limits layout options, however appropriate

measures to mitigate erosion and scour can be undertaken. Additionally, the replacement

crossing layout took the possible future replacement of the CPR Bridge into consideration to

ensure that the alignment doesn't limit replacement options for that crossing at that time.

The creek downstream of the Saskatchewan Avenue crossing has been scoured

approximately 2 m below the culvert invert and as a result, a large pool has been formed. The

riverbanks don't appear to be showing evidence of additional scour and undermining and it

was judged that shoreline erosion protection outside of the bridge opening does not appear to

be necessary to satisfy hydraulic requirements.


5 Ice Loadings

There are several modes of interaction between ice and bridge piers which may develop

forces which have to be taken into consideration in the design of a pier. The potential modes

of ice interaction on the piers may include:

Dynamic forces due to moving sheets or floes of ice being carried by river currents.

Static pressure due to thermal expansion movements of the ice cover.

Pressures resulting from the formation of a hanging ice dam or by an ice jam

Vertical loading resulting from the adhesion of ice to the pier in waters with fluctuating

water level.

Section 3.12 – Ice Loads of the Canadian Highway Bridge Design Code4 will be referenced to

develop ice loading forces for the design of the piers.

5.1 Dynamic Ice Forces

Dynamic forces occur when a moving ice floe strikes a bridge pier. Forces imposed by the ice

floe on a pier are dependent on the size of the individual ice floes (thickness, width and

length), the internal strength of the ice and the geometry of the pier nose. For smaller

waterways, like Sturgeon Creek, the governing ice loads are typically due to crushing and

bending/flexure. Note however, the ice and resultant loadings that have been observed on

Sturgeon Creek would not be excessive.

The effective ice strength varies depending on the air temperatures and the integrity of the ice

cover. The Code provides guidelines for estimating the effective crushing strength of the ice

cover (Section 3.12.2.1). The value which best reflects the effective crushing ice strength is

(b) “the ice breaks up at melting temperature and is somewhat disintegrated: 700 kPa”. The

thickness of the ice cover has been assumed to be limited to 750 mm, although locally thinner

and thicker sections could exist depending on the severity of the winter, the snow cover and

flows throughout the winter period. A 750 mm thickness would be considered the upper limit

on average for ice thickness within the river. The code provides equations for the estimation of

the horizontal forces computed by both crushing and bending modes. The governing ice

loading force, F, will be the smaller of either of these two estimates as the ice will fail in either

crushing or flexure modes once it reaches the smaller of these two loadings.

4 “Canadian Highway Bridge Design Code”, Canadian Standards Association, November 2006, Section 3.12


The code recommends that the acting ice load or impact force for piers parallel to the flow, as

would exist at the Saskatchewan Avenue Bridge with skewed piers, be assessed for two load

cases as indicated. During breakup, the ice would be confined to the main river channel which

would be in alignment with the proposed bridge and the piers.

The resultant dynamic ice force should be applied at a given elevation which corresponds to

the water level at the time of estimated breakup. The required water level elevation and top of

ice elevation at the Saskatchewan Avenue Bridge has been estimated to be 233.5 m. The

elevation to apply the force can be taken as the centre of the ice cover which is approximately

233.1 m. Corresponding bridge opening velocities are estimated at 0.8 m/s.

Any remedial measures required for the piers should incorporate a rounded or bullet-shaped

nose as that form reduces the ice loadings relative to pointed angular noses. The sloping of

the upstream face of the pier can also decrease ice loadings by reducing the force necessary

to fail the ice by flexure; however this may only be an advantage when the crushing strength is

relatively high, however a sensitivity on the slope angle should be assessed to determine if a

design advantage exists.

5.2 Static Ice Forces

Thermal expansion of an ice cover can induce significant loading on piers if the loading is

unbalanced, acting only on one side. Generally thermal expansion is of greater concern within

a lake environment where the ice is constrained on one shoreline and expands laterally out

from the shore. The limited ice cover within the proposed bridge opening would not be large

enough to generate sufficient static ice forces which would result in an imbalance in forces,

therefore no allowance for static forces will be assumed.

5.3 Ice Jam Forces

Dynamic forces occur when moving ice jams and hanging ice dams shed their internal forces

to the river banks, to islands or to obstructions like bridge piers within a waterway. The code

provides guidance with respect to estimating the loading of an ice jam on the bridge piers. For

clear openings between piers less than 30 m, a pressure of 10 kPa can be assumed which

acts on either one of the lateral faces or the upstream face of the pier over the thickness of the

ice jam. Ice jams at this location would be unlikely, however the sensitivity of the pier loadings

should be assessed for a nominal ice jam thickness. The estimated ice jam thickness is

1000 mm which would be assumed at a water level and corresponding ice surface elevation of

233.5 m.


5.4 Ice Adhesion Forces

Ice adhesion is generally of concern in areas where rapidly varying water levels can occur

such as below a hydroelectric development during ice formation periods. Flows and

corresponding water levels within Sturgeon Creek throughout the winter period remain

relatively stable and would not typically result in significant vertical loadings.


6 Other Considerations

Best Management Practices for working near waterways including the appropriate

implementation of sediment and erosion control measures should be followed. Exposed

slopes not covered with rock should be revegetated and covered with erosion control blanket.

Construction activities within the creek shall not take place between April 1 and June 15 of any

given year. An Environmental Management Plan should be prepared which details the specific

environmental management requirements and sediment and erosion control.

Water management during construction can be an important aspect of any project and may

influence the cost and scheduling for crossing replacement. The largest flows within the creek

are expected to occur during the spring runoff period and following a heavy summer rainfall

event. Construction should take place in the late fall and winter period when the potential for

runoff is reduced thereby minimizing water management requirements. All instream work

should be completed no later than March 15th, with the schedule showing the majority of

instream work completed by early March. Although minimal, flows continue throughout the

winter and should be considered as part of the water management plan with appropriate

measures taken to deal with the flow. Additionally there is a considerable volume of water

within the downstream scour hole and creek upstream which has to be taken into

consideration for water management during construction.

Figures

231.0

231.5

232.0

232.5

233.0

233.5

0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0

WA

TER

LEV

EL (

m)

DISCHARGE (m3/s)

WSC 05MJ001 STAGE-DISCHARGE

HEC-RAS MODEL - STA 14+05

STURGEON CREEK WSC 05MJ004 STAGE-DISCHARGE RELATIONSHIP

FIGURE 2

NOTE: 1) STAGE-DISCHARGE RELATIONSHIP DERIVED FROM OBSERVED WATER LEVEL AND DISCHARGE DATA AT THE WATER SURVEY OF CANADA GAUGE (05MJ004 - STURGEON CREEK NEAR ST JAMES ) FOR THE PERIOD FROM 2011 TO 2014 2) HEC-RAS DATA FROM MAY 2016 STURGEON CREEK MODEL FOR LOCATION JUST UPSTREAM OF STURGEON ROAD.

Appendix A

Fish Habitat Classification Map

Appendix B

Photographs

Sturgeon Creek at Saskatchewan Avenue – Crossing Replacement

Photo No. 1 Creek upstream of CPR Bridge Crossing

Photo No. 2 Upstream side of CPR Bridge Crossing All photographs taken April 29, 2016


Photo No. 3 Upstream side of Saskatchewan Avenue Crossing

Photo No. 4 Downstream side of CPR Bridge Crossing just upstream of Saskatchewan Avenue


Photo No. 5 Downstream side of Saskatchewan Avenue Crossing

Photo No. 6 Creek downstream of Saskatchewan Avenue Crossing

saskatchewan avenue crossing replacement at sturgeon creek environmental assessment report ·...

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