Potential Flood Storage Schemes in the Bow River Basin

POTENTIAL FLOOD STORAGE SCHEMES IN THE BOW RIVER BASIN

Submitted to: Alberta Environment and Parks Resilience and Mitigation Branch Edmonton, Alberta

Submitted by: Amec Foster Wheeler Environment & Infrastructure Calgary, Alberta

September 2015

CW2174

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Alberta Environment and Parks Amec Foster Wheeler Flood Storage Schemes in the Bow River Basin Environment & Infrastructure Calgary, Alberta September 2015

EXECUTIVE SUMMARY

Amec Foster Wheeler Environment & Infrastructure, a division of Amec Foster Wheeler Americas Ltd. (Amec Foster Wheeler), has been asked by Alberta Environment and Parks (AEP) Resilience & Mitigation Branch (RAM) to investigate opportunities for flood storage in the Bow River Basin upstream of Calgary.

The study was to investigate flood storage opportunities within the Bow River basin upstream of Calgary that would provide protection to The City of Calgary (the City) and other stakeholders from floods with a magnitude similar to the June 2013 flood event. This report provides the results of a high level, conceptual, desktop investigation and therefore:

► The June 2013 flood event is referenced to provide perspective with respect to the size of potential flood mitigation works required. Additional work is required to finitely establish the size/frequency of the design flood event for mitigation purposes; ► Costs are an indication of likely capital investment; ► No geotechnical investigations were carried out; ► No detailed or preliminary design has taken place; ► Operational specifics have not been studied in detail; ► Land ownership and use has not been studied in detail; and ► No environmental review has been undertaken.

The summary table on the following page identifies 11 possible flood mitigation storage locations along with their characteristics and some relevant technical information. It is recommended that the following work be undertaken prior to wider engagement on selected schemes:

► Confirmation of basin hydrology and study of historical events within each basin; ► A desktop review of geotechnical/geo-hazard risks at each site; ► A desktop review of environmental, social, land use & ownership constraints; ► Confirmation of dam characteristics and affected areas; ► Identification of external and internal (government) stakeholders for each scheme; ► Identification of infrastructure, pipelines & utilities that may be affected associated with each scheme; ► The establishment of design criteria; and ► Identification of other potential risks and issues to be resolved.

It is important to emphasize that the viability of all 11 of these schemes is yet to be proven and each will have environmental, social, geotechnical and design challenges which should be identified before going to stakeholder engagement.

Potential flood flow reductions resulting from each individual scheme are related to complex basin hydrology. Due to differences in basin response times (the amount of time it takes for rain falling within a basin to reach the point of interest), it cannot be assumed that the actual flow

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Alberta Environment and Parks Amec Foster Wheeler Flood Storage Schemes in the Bow River Basin Environment & Infrastructure Calgary, Alberta September 2015 reductions achieved in Calgary for multiple schemes would be the arithmetic sum of flow reductions from individual schemes; nor can it be assumed that the flow reductions would be achieved for all flood events. Detailed hydrological analysis should be undertaken at the preliminary design stage to achieve the optimal balance in geographic location and project size.

A summary description of 11 potential schemes is provided in Table 1.

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Alberta Environment and Parks Amec Foster Wheeler Flood Storage Schemes in the Bow River Basin Environment & Infrastructure Calgary, Alberta September 2015

Table 1: Summary of Potential Bow River Flood Storage Schemes

Ref Scheme Description River Upstream Proportion of Bow Indicative Estimated Type of Basin Area Basin Regulated Project Cost Storage Mitigation or (km2) by Scheme ($million) Available Opportunity (dam3)

1 Spray River basin upstream of Spray Spray River 510 6.6% <$100 N/A Operational Operational Lakes Reservoir Opportunities in 2 Cascade River Basin upstream of Cascade River 640 8.5% <$100 N/A Operational Tributary Lake Minnewanka Watersheds 3 Kananaskis River Basin upstream of Kananaskis River 360 4.6% <$100 N/A Operational Lower Kananaskis Lake

Upper Ghost River Diversion into 4 North Ghost River 230 2.9% <$100 Est 20,000 New Project Lake Minnewanka

Dam on Ghost River Upstream of 5 Ghost River 615 7.8% $200-$400 50,000 to 70,000 New Project Waiparous Creek New Projects on Tributaries to the Dam on Waiparous Creek Upstream 6 Waiparous Creek 330 4.2% $200-$400 30,000 to 40,000 New Project Bow River of Ghost River

Dam on Kananaskis River near 7 Kananaskis River 900 11.4% $200-$400 80,000 to 90,000 New Project Upstream end of Barrier Lake

Dam on Jumpingpound Creek 8 Jumpingpound Creek 600 7.7% $200-$400 50,000 to 70,000 New Project Upstream of Bow River Confluence

Operational Opportunity on 9 Ghost Reservoir Dam Drawdown Bow River 6500 85% <$100 50,000 to 70,000 Operational Bow River Mainstem Dam on Bow River Upstream of 10 Bow River 7770 >95% <$1,000 60,000 to 80,000 New Project New Projects on Bearspaw Reservoir Bow River Dam on Bow River upstream of Ghost Mainstem 11 Bow River 5300 65% <$1,000 >150,000 New Project Lake (Morley)

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Alberta Environment and Parks Amec Foster Wheeler Flood Storage Schemes in the Bow River Basin Environment & Infrastructure Calgary, Alberta September 2015

TABLE OF CONTENTS

1.0 INTRODUCTION ...... 1 1.1 Scope ...... 1 1.2 Project Scale Requirements ...... 1

2.0 BACKGROUND ...... 3 2.1 Overview ...... 3 2.2 Existing Tributary Basins with Flow Regulation ...... 3 2.2.1 Scheme 1 - Spray River Upstream of Spray Lakes Reservoir ...... 3 2.2.2 Scheme 2 - Cascade River Upstream of Lake Minnewanka ...... 4 2.2.3 Scheme 3 - Kananaskis River Upstream of Kananaskis Lake (Upper and Lower) ...... 5 2.2.4 Summary of the Effect of Existing Tributary Basin Flow Regulation ...... 6 2.3 New Opportunities on Tributaries of the Bow River ...... 7 2.3.1 Scheme 4 - North Ghost Diversion to Lake Minnewanka ...... 7 2.3.2 Scheme 5 - Ghost River Dam Upstream of Waiparous Creek ...... 8 2.3.3 Scheme 6 - Waiparous Creek Dam Upstream of the Ghost River ...... 9 2.3.4 Scheme 7 - Kananaskis River Dam Upstream of the Barrier Reservoir ...... 10 2.3.5 Scheme 8 - Jumpingpound Creek Dam ...... 10 2.4 New Opportunities on the Main Stem of the Bow River ...... 12 2.4.1 Scheme 9 - Ghost Reservoir Drawdown ...... 12 2.4.2 Scheme 10 - Dam on the Bow River Upstream of Bearspaw Reservoir ...... 12 2.4.3 Scheme 11 - Dam on the Bow River Upstream of Ghost Lake (near Morley) ...... 13

3.0 CONCLUSIONS AND RECOMMENDATIONS ...... 14

4.0 CLOSURE ...... 16

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Alberta Environment and Parks Amec Foster Wheeler Flood Storage Schemes in the Bow River Basin Environment & Infrastructure Calgary, Alberta September 2015

LIST OF TABLES

Table 1: Summary of Potential Bow River Flood Storage Schemes ...... iii

LIST OF FIGURES

Figure 1 June 2013 Bow River Hydrograph and Mitigation Requirements ...... 2 Figure 2 Spray Lake and Spray River...... 4 Figure 3 Cascade River and Lake Minnewanka ...... 5 Figure 4 Upper and Lower Kananaskis Lakes ...... 5 Figure 5 Naturalized Flow Hydrograph downstream of Bearspaw Reservoir (June 2013) .. 6 Figure 6 Schemes on the Ghost River ...... 8 Figure 7 Waiparous Creek Dam Upstream of the Ghost River ...... 9 Figure 8 Kananaskis River Dam ...... 10 Figure 9 Jumpingpound Creek Dam ...... 11 Figure 10 Mainstem Bow River Schemes...... 12

LIST OF APPENDICES

Appendix A Figure A1 – Location of Potential Mitigation Projects

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Alberta Environment and Parks Amec Foster Wheeler Flood Storage Schemes in the Bow River Basin Environment & Infrastructure Calgary, Alberta September 2015

1.0 INTRODUCTION

1.1 Scope Amec Foster Wheeler Environment & Infrastructure, a division of Amec Foster Wheeler Americas Ltd. (Amec Foster Wheeler) has been asked by Alberta Environment and Parks Resilience & Mitigation Branch (RAM) to investigate opportunities for flood storage in the Bow River Basin upstream of Calgary.

The study was to investigate flood mitigation measures that would provide protection to the City of Calgary from floods with a magnitude similar to the June 2013 flood event. The report identifies several possible flood mitigation storage locations along with their characteristics and some relevant technical information. This report is a high level review and therefore:

Aside from habitations (for example at Waiparous, Cochrane, Morley, Exshaw, Canmore), there are a number of constraints within the Bow River basin which are primarily related to administrative boundaries, land ownership and existing infrastructure. These are:

► Banff National Park; ► Stoney Nakoda First Nation; ► Various administrative and recreation area boundaries in Kananaskis region; and ► Various hydroelectric schemes operated by TransAlta.

1.2 Project Scale Requirements As previously mentioned, there were no specific design criteria for this initial investigation into flood storage opportunities. However, to determine the magnitude or scale of project needed to mitigate flooding from the Bow River, it was agreed that the June 2013 event would provide a good indication of flood storage requirements because it is quite likely the largest flood event on record in the Bow River basin once regulation in the basin is taken into consideration (see Section 2.2.5).

The June 2013 flood event flow rate peaked at approximately 1840 m3/s in Calgary (see Figure 1). The estimated current threshold for flooding from the Bow River within the City is approximately 800 m3/s. For flow rates above this value, overland flooding and evacuations commence and the City begins to have issues with sanitary lift stations. To mitigate flooding for

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Local mitigation efforts within the City may increase the flood threshold and reduce the required storage volumes. Some of these projects may be funded by the Government of Alberta through grant programs (FREC or ACRP) and others may result from a combination of Municipal Recovery funding and funding from the City of Calgary or fully by the City of Calgary. Engagement with the City of Calgary, its consultants and RAM is a future requirement.

Figure 1 June 2013 Bow River Hydrograph and Mitigation Requirements

2.0 BACKGROUND

2.1 Overview Approximately 20% of the Bow River basin upstream of Calgary is regulated by TransAlta facilities which provide de facto flood defence within the upstream environment. TransAlta owns and operates these facilities to produce electricity and will operate them during flood conditions in such a manner as to protect the safety of the dams. The reduction of flooding in Calgary is essentially a by-product of these operations which cannot always be relied upon unless specific pre-flood agreements are established. The following paragraphs describe opportunities within these regulated basins (for convenience, referred to here as “basins with flow regulation”) and those with new opportunities for reducing flood discharge. Opportunities are illustrated at a conceptual level. Field investigations and study are required to better define specific project locations (which could vary by several kilometres from the locations shown herein), flood mitigation potential and technical viability. The approximate locations of the potential mitigation schemes are illustrated in Figure A1 (Appendix A).

2.2 Existing Tributary Basins with Flow Regulation There are three relatively large basins in the Bow River watershed above Calgary which are significantly regulated by structures owned by TransAlta for electricity generation. These are:

► Spray River upstream of Spray Lakes Reservoir; ► The Cascade River upstream of Lake Minnewanka; and ► Kananaskis River upstream of Kananaskis Lakes (Upper and Lower). The effect on the flood hydrology for the June 2013 event and mitigation potential at these sites is described below.

2.2.1 Scheme 1 - Spray River Upstream of Spray Lakes Reservoir Approximately 510 km2 or 6.6% of the Bow Basin upstream of Calgary City Limits is regulated by the Spray Lakes reservoir. The Spray River basin was near the ‘epicentre’ of the rainfall event in June 2013. During the flood, the discharge from the Spray River was reduced from an estimated inflow to the lake of 255 m3/s to an outflow of 18 m3/s.

Depending on the natural downstream flood attenuation, and other basin hydrologic and hydraulic characteristics, the presence of the Spray Lakes TransAlta infrastructure may have reduced the June 2013 flood in Calgary in the region of 200 m3/s.

An opportunity therefore exists to work with TransAlta to form an agreement to provide seasonal storage capacity within the Spray Lake system to help mitigate downstream flooding.

Figure 2 Spray Lake and Spray River

2.2.2 Scheme 2 - Cascade River Upstream of Lake Minnewanka The Cascade River is the main source of runoff for Lake Minnewanka. It has a basin area of 644 km2 representing approximately 8.5% of the Bow basin upstream of the City of Calgary.

Until June 2013, Lake Minnewanka was also fed from a diversion from the North Ghost River through Devil’s Gap. The maximum capacity of this diversion1 was 11 m3/s; however it was completely destroyed in June 2013 and is yet to be reconstructed.

An application has been made by TransAlta under the Water Act for approval to reinstate the North Ghost River diversion. The plan is to construct a buried pipeline with a capacity of between 6 m3/s and 8 m3/s.

During the June 2013 flood event, discharge at Lake Minnewanka was reduced from an inflow of 314 m3/s to an outflow of 27 m3/s through the spillway.

An opportunity therefore exists to work with TransAlta to form an agreement to provide seasonal storage capacity within the Lake Minnewanka system to help mitigate downstream flooding.

1 South Saskatchewan River Basin Structures Inventory, Appendix 2 to Volume 1. Alberta Environment. July 1981.

Figure 3 Cascade River and Lake Minnewanka

2.2.3 Scheme 3 - Kananaskis River Upstream of Kananaskis Lake (Upper and Lower) The Kananaskis River upstream of the Upper and Lower Kananaskis Lakes represents approximately 4.6% of the Bow River basin upstream of Calgary City limits. In June 2013, the antecedent conditions in the reservoir were such that there was no outflow from the storm. The reservoirs were more than 10 m below the full supply level even after the flood event. As a result of the low levels prior to the event, combined discharge from both lakes may have been reduced by as much as 216 m3/s.

An opportunity therefore exists to work with TransAlta to form an agreement to provide seasonal storage capacity within the Kananaskis Lakes system to help mitigate downstream flooding.

Figure 4 Upper and Lower Kananaskis Lakes

2.2.4 Summary of the Effect of Existing Tributary Basin Flow Regulation During the June 2013 flood event, the peak flow was reduced by existing infrastructure. In particular, the presence of Lake Minnewanka, Spray Lakes and Upper and Lower Kananaskis Lakes had a very profound impact on the severity of downstream flooding. Other reservoirs, for example Barrier Lake (Kananaskis River) and Bearspaw Reservoir (Bow River) had little effect.

It can be concluded that the flood on the Bow River in Calgary would have been much worse had the above mentioned, TransAlta owned, reservoirs not had such an attenuating effect on a significant proportion of the basin.

AEP provided Amec Foster Wheeler with a “naturalized” hydrograph which was based on hydrologic modelling of the Bow River basin. Naturalized means that an attempt was made to simulate, or back calculate, the hydrograph as though there were no flow regulation in the basin. The hydrograph shown in Figure 5 shows the naturalized flow hydrograph for June 2013 downstream of Bearspaw Reservoir. It shows that the Bow River flood at Calgary could have been as high as 2250 m3/s had the TransAlta facilities not absorbed a significant portion of the flood water. It shows that the June 2013 flood was the highest on the Bow River since systematic flow monitoring commenced about 1908.

Figure 5 Naturalized Flow Hydrograph downstream of Bearspaw Reservoir (June 2013)

By calculating the volume between the recorded and naturalized hydrographs, it is estimated that, including storage within the Ghost Reservoir described in Section 2.4.1, the TransAlta facilities took approximately 95,000 dam3 in flood volume out of the system and may have reduced the peak flow rate in Calgary by over 400 m3/s.

2.3 New Opportunities on Tributaries of the Bow River

2.3.1 Scheme 4 - North Ghost Diversion to Lake Minnewanka As previously discussed, TransAlta is in the process of getting approval to replace the North Ghost River diversion which was destroyed in the June 2013 flood. This diversion will be via pipeline and have a maximum capacity of approximately 8 m3/s. This diversion provides additional water to Lake Minnewanka and the Cascade River hydroelectric plant.

An opportunity exists to divert a larger proportion of the upper North Ghost River flow into Lake Minnewanka through Devil’s Gap during extreme flood events.

Up to 60 m3/s could be diverted by this scheme; rather than the proposed 8 m3/s. An estimate of the discharge from the North Ghost River in June 2013 equates to an approximate 1 m rise in lake level in Lake Minnewanka (approximately 22,000 dam3).

Since Lake Minnewanka is a large waterbody, for every meter of lake level rise, 22,000 dam3 could be stored. As such, there may be potential to negotiate the seasonal drawdown of the lake to accommodate such an event.

The existing Lake Minnewanka spillway capacity may not be sufficient and therefore the increased diversion rate would require either a second dam to be built in the region upstream of Lake Minnewanka (this may lie within Banff National Park) or to increase the capacity of the spillway at the existing dam.

The scheme would control a basin area of approximately 230 km2 or 2.9% of the overall Bow River basin to Calgary (at Bearspaw). The small proportion of the overall Bow Basin controlled together with complications in obtaining approvals from the National Park would be expected and may render this scheme unviable.

Figure 6 Schemes on the Ghost River

2.3.2 Scheme 5 - Ghost River Dam Upstream of Waiparous Creek Scheme 5 is a dam on the Ghost River upstream of the hamlet of Waiparous and the confluence with Waiparous Creek. The scheme would control a basin area of approximately area of 615 km2, or 7.8% of the overall Bow River basin to Calgary.

Following the June 2013 flood, the Flood Advisory Panel recommended a dam on the Ghost River upstream of Waiparous Creek. This site was known as BG1. Scheme 5, shown in Figure 6, is slightly upstream from BG1 but is on the same reach of river. Moving the dam upstream slightly to a slightly flatter reach of river has the advantage of a lower dam height but yields a similar storage volume.

Stantec estimated that BG1 could store up to 62,800 dam3 and could reduce flows in the Bow River by up to 380 m3/s (or 36% of the required mitigation) in a June 2013 size flood. Modelling undertaken by Alberta WaterSmart indicated a reduction of 375 m3/s; confirming Stantec’s estimates.

However, a dam at this location would only be effective for an event that is generated over the North or South Ghost Rivers. As a standalone mitigation scheme, a dam on the Ghost River does not provide adequate protection to the City of Calgary.

2.3.3 Scheme 6 - Waiparous Creek Dam Upstream of the Ghost River Scheme 6 is a dam on the Waiparous Creek upstream of the hamlet of Waiparous and the confluence with Ghost River. The scheme would control a basin approximately 330 km2, or 4.2% of the overall Bow River basin to Calgary.

The Flood Advisory Panel also recommended a dam on the Waiparous Creek upstream of the Ghost River and the hamlet of Waiparous. This site was known as BW1. Scheme 6, shown in Figure 7, is slightly upstream from BW1 but is on the same reach of river.

The Flood Advisory Panel estimated that BW1 could store up to 38,400 dam3 and could reduce flows in the Bow River by up to 280 m3/s (or 31% of the required mitigation) in a June 2013 size flood. Alberta WaterSmart estimated that the reduction in flows by a dam at this location for the 2013 event would only be 78 m3/s. Based on the small basin size, the true reduction is probably closer to the latter figure.

A dam at this location would only be effective for an event that is generated over Waiparous Creek.

Figure 7 Waiparous Creek Dam Upstream of the Ghost River

2.3.4 Scheme 7 - Kananaskis River Dam Upstream of the Barrier Reservoir Approximately 360 km2 (40%) of the upstream tributary basin is already regulated by Upper and Lower Kananaskis Lakes. June 2013 flood outflow from Upper and Lower Kananaskis Lakes (see Section 2.2.3) was minimal due to very low antecedent lake levels. Data obtained from TransAlta shows that during the June 2013 flood, the inflow into Barrier Lake was equivalent to the outflow, and therefore the lake had no tangible effect on discharges at Calgary.

2.3.4.1 New Dam Upstream of the Existing Barrier Dam An opportunity exists to construct a new dam across Barrier Lake at a location near the pinch point on the left side of the photograph in Figure 8. A 35 m high dam may be possible that could hold 85,000 dam3 and reduce flows in the Kananaskis River by over 300 m3/s based on June 2013 hydrology. With the reduction from the Upper and Lower Kananaskis Lakes, this new dam would reduce discharge from the Kananaskis River to non-flood conditions for a June 2013 magnitude event. Alternative consideration could be given to siting the dam upstream of the existing reservoir; but which may have increased social and environmental impacts.

A new dam at this location would control a basin approximately 900 km2 or 11.4% of the overall Bow River basin to Calgary.

Figure 8 Kananaskis River Dam

2.3.5 Scheme 8 - Jumpingpound Creek Dam The Jumpingpound Creek basin area is approximately 640 km2 at the mouth representing approximately 8% of the overall Bow River basin area upstream of Calgary. Its headwaters rise in the hills between the Elbow River and the Kananaskis River but do not reach into the Rocky Mountains.

The basin is predominantly rural with few dwellings; but is intersected by the Trans-Canada Highway. It may be possible to construct a dam across Jumpingpound Creek at the location shown in Figure 9. With a 30 m high dam, this site could store approximately 60,000 dam3 for an indicative flow reduction of 220 m3/s for a June 2013 magnitude event.

Figure 9 Jumpingpound Creek Dam

2.4 New Opportunities on the Main Stem of the Bow River

Figure 10 Mainstem Bow River Schemes

2.4.1 Scheme 9 - Ghost Reservoir Drawdown In the June 2013 flood event, the level in Ghost Lake rose by 0.91 m from 1191.08 m to 1191.99 m. A total of 10,300 dam3 of floodwater was stored. Given the large volume required, this had little effect on the levels experienced in Calgary. However, there is a significant amount of potential storage in Ghost Lake if an agreement can be made with TransAlta for seasonal drawdown. An agreement was in place to draw the level down for the 2015 flood season.

An opportunity exists to form a permanent agreement on the seasonal operation of the Ghost Reservoir to ensure that there is a considerable amount of flood storage available each freshet. It may also be possible to undertake structural improvements to the dam and riparian environment that would facilitate a more rapid draw down of the reservoir in anticipation of a flood. A detailed investigation of opportunities at the Ghost Reservoir would require detailed consultation with not only TransAlta but other stakeholders due to the recreational and in-stream flow needs along the Bow River.

2.4.2 Scheme 10 - Dam on the Bow River Upstream of Bearspaw Reservoir A previous assessment of flood mitigation potential of this reservoir was undertaken by Amec Foster Wheeler in April 20152. An assessment of the storage available with a 30 m high dam at Bearspaw was undertaken using LiDAR data. The maximum water level behind the dam would be in the region of 1,121 m (approximately 30 m high dam). This is the estimated maximum dam height considering it is constrained by the CPR railway line as well as infrastructure in Cochrane that would begin to flood above the 1,121 m contour. This ignores the

2 Memo to Alberta Environment and Parks: Review of Potential for a Dam on the Bow River near Range Road 33

The maximum storage available in this reservoir is estimated to be just over 70,000 dam3. This storage volume represents 35% of the storage required to attenuate the June 2013 flood to 800 m3/s. It would therefore not be adequate as a standalone scheme, but could be considered in combination with other initiatives in the basin.

2.4.3 Scheme 11 - Dam on the Bow River Upstream of Ghost Lake (near Morley) Upstream of Ghost Lake lies a vast expanse of wide floodplain. This area is entirely within the Stoney Nakoda First Nation Reserve lands.

A new dam at this location would control approximately 5300 km2 or 65% of the overall basin to Calgary. A big advantage of this scheme, as with others on the mainstem Bow River close to Calgary, is that the proportion of the basin controlled is so large. It would not matter where the source of flooding in the upstream mountain environment was, the scheme would still be effective.

A 30 m high dam at this location would provide 65% of the required storage volume to mitigate the Bow River flooding from June 2013. A dam higher than 30 m may be possible but it would begin to impact the railway line and the TransCanada highway.

Further investigation would be required to determine the viability of such a large flood mitigation scheme.

3.0 CONCLUSIONS AND RECOMMENDATIONS

The locations of the 11 potential flood storage schemes are illustrated in Figure A1 (Appendix A). A summary comparison of potential storage, flow reduction and indicative cost for each scheme is provided in Table 1 (included in Executive Summary).

This report presents the results of a high level study of flood storage opportunities in the Bow River basin upstream of Calgary and therefore:

► Costs are an indication of likely capital investment; ► No geotechnical investigations were carried out; ► No detailed or preliminary design has taken place; ► Operational specifics have not been studied in detail; ► Land ownership and use has not been studied in detail; and ► No environmental review has been undertaken.

The viability of these schemes is yet to be proven. Project locations as illustrated herein are approximate and could be moved significant distances upstream of downstream dependent on the results of future field investigations and design studies. Further study is required to determine project viability and to better establish flood mitigation potential and associated project costs.

The following would should be undertaken prior to wider engagement on selected schemes:

► Confirmation of basin hydrology and study of historical events within each basin; ► A desktop review of geotechnical/geo-hazard risks at each site; ► A desktop review of environmental, social, land use & ownership constraints; ► Confirmation of dam characteristics and affected areas; ► Identification of external and internal (government) stakeholders for each scheme; ► Identification of infrastructure, pipelines & utilities that may be affected by each scheme; and ► Identification of other potential risks.

All new opportunities would have environmental and social impacts. Combined schemes would need to be considered to provide June 2013 flood level flood protection; with due consideration given to flood mitigation works which may be implemented by The City of Calgary. Otherwise, double counting of the economic benefits to society would occur. Consideration should also be given to developing projects for multi-purpose use (i.e., including live storage) as this will significantly increase the benefit cost ratio and ‘triple bottom line’ value of these projects to the Province of Alberta and downstream developments. In this respect, these structures should be considered and designed to be ‘water management’ structures capable of reducing the impacts of droughts and floods.

The source of indicated potential flow reductions varies3 and are only an indication of the potential flow reduction at a given site for a standalone project. Due to differences in basin

3 Source is an estimation by Amec Foster Wheeler unless otherwise indicated.

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Due to the size of the Bow River basin and the presence of infrastructure and administrative boundaries, it is likely that a single scheme will not be sufficient to protect downstream properties to a desired standard of protection. Consideration should be given to implementing more than one scheme to provide a desirable standard of protection.

Further study will be required to determine the optimal balance between flood protection, cost, societal impact, environment and administrative boundaries.

4.0 CLOSURE This report has been prepared for the exclusive use of Alberta Environment and Parks. This report is based on, and limited by, the interpretation of data, circumstances, and conditions available at the time of completion of the work as referenced throughout the report. It has been prepared in accordance with generally accepted engineering practices. No other warranty, express or implied, is made.

Yours truly, Amec Foster Wheeler Environment & Infrastructure a Division of Amec Foster Wheeler Americas Limited

Reviewed by:

Geoff Graham, B.Sc., C.WEM Ken Kress, P.Eng. Associate Water Resources Specialist Principal Engineer Tel: (403) 387-1883 Fax: (403) 248-1590 Email: [email protected]

GG/KK/cf

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Appendix A

Figure A1 – Location of Potential Mitigation Projects