The formal study regarding replacing the deadly Calgary Weir with natural looking rapids, by Golder and Associates, has been released. The Executive Summary is available, for your information. The formal study regarding replacing the deadly Calgary Weir with natural looking rapids, by Golder and Associates, has been released. The Executive Summary is attached here, for your information.



Background
The Western Headworks Diversion Weir is located on the Bow River within the City of Calgary and is operated for the purpose of supplying water to the Western Irrigation District (WID). Although it functions well to satisfy the intended purpose, the design of the diversion weir creates an extremely dangerous hydraulic condition that has claimed several lives and is often referred to as “the drowning machine”. It also represents an impassable barrier to boaters and potentially to fish.

Previous Investigations
In 2001, the Bow Waters Canoe Club with funding from the Calgary Communities Lottery Board engaged John Anderson Architect and McLaughlin Water Engineers (Anderson & McLaughlin) to conduct a Feasibility Study for Modifications to the Western Headworks Weir. This was a qualitative study that looked at various ways to provide recreational and safety enhancements at the existing weir, including in-river by-pass channels on river left and river right, off-river by-pass channels through Pearce Estate Park and the so called “full width whitewater rapid option”. Anderson & McLaughlin evaluated each alternative and ranked them with respect to how well the following objectives and/or constraints were likely to be satisfied:

• Preserves the irrigation diversion.
• Complements the adjacent parks.
• Improves safety.
• Does not adversely affect floods and ice levels.
• Enhances fish passage and habitat.
• Provides boating opportunities for all skill levels.

The “full width rapid” and the “in-river right bypass” were the highest and second highest scoring alternatives, respectively.


Current Study Goals and Objectives
The current study carries on from the previous study by Anderson & McLaughlin to produce a feasibility level design and cost estimate. In addition, the study includes an overview assessment of the potential impacts and benefits associated with the preferred alternative. The stated goal of the project proponents is simply:

“To identify and evaluate alternative methods to modify the Bow River weir in Calgary to allow small (non-motorized) boat passage and eliminate the dangerous hydraulic roller created by the existing structure.”

However, the study scope is defined by a very detailed Terms of Reference that include a set of 19 “criteria” that were developed based on input received from the Technical Advisory Group and the Public Advisory Committee.

Preferred Alternative
Based on a review of alternative design concepts, the consultant team for the current study concluded that the “full width rapid” alternative best satisfies the study Terms of Reference. The full width rapid concept offers the following advantages over other options:

• It eliminates the dangerous hydraulic roller created by the existing weir and provides the highest degree of boater and public safety.
• It has the potential to be the most aesthetically pleasing (naturally appearing) alternative.
• It has the potential to provide river features attractive to kayakers and canoeists with the least impact on the right river bank and Pearce Estate Park.

The key features of the design are:

• No change to the orientation of the existing weir crest and no change to the existing Western Headworks sluiceway structure.
• A bypass channel on river right (Low Flow Channel) intended to provide a less difficult bypass for a variety of watercraft at low and normal water levels.
• A full width rapid (High Flow Channel) extending from the bypass channel to the existing sluiceway structure, thereby eliminating the existing hazard created by the diversion weir.
• A shallow notch constructed on the right side of the weir to direct flow towards the by-pass channel on river right.

Conclusions
The proposed design is considered to be a technically viable alternative that could be built at a capital cost (including engineering and contingencies) of approximately $6.5 million. The project would offer many benefits, including:

• Increased safety and navigability.
• New recreational opportunities for whitewater boating.
• Economic opportunities created by increased visitors to Calgary and area.
• Reduced costs for Fire Department Aquatic Rescue Unit.
• Reduced costs for Alberta Environment safety measures.
• Improved fish passage and habitat.
• Aesthetic improvement.
• Educational opportunities.

Primary areas of concern requiring further investigation and resolution of issues prior to project implementation include:

• Effect of incremental flood level increases on adjoining and upstream properties.
• Effects of increased river levels on Sam Livingston Fish Hatchery water supply wells and the Pearce Estate Park Interpretive Wetlands Cold Water Stream.
• Impact of increased activity on adjacent land uses, especially Pearce Estate Park.
• Lack of a firm plan to provide access and parking for paddlers and other users.
• Environmental impact and mitigation requirements.
• Better understanding of annual maintenance requirements and associated costs.

Recommendations
The following actions should be adopted as the “next steps” towards advancing this project to the detailed design phase:

Step 1 – Detailed Assessment of Incremental Flood Levels
The City of Calgary has expressed concerns regarding the potential impacts of incremental increases in 1:100 year flood levels upstream of the modified weir. Although the magnitude of the potential flood level increases is relatively small, additional analysis is warranted to verify the levels computed in the pre-design study and to identify any mitigative measures that may be required. These investigations will need to be carried out in consultation with the City of Calgary.

Step 2 – Preliminary Groundwater Study
Alberta Sustainable Resource Development (ASRD) has expressed concerns regarding the potential impacts of the proposed design on the Fish Hatchery water supply wells and on the Pearce Estate Park Interpretive Wetlands Cold Water Stream. This pre-design study has recognized the importance of these water supply wells and has concluded that any impacts of the proposed weir modifications will be of small consequence on the quality and quantity of groundwater produced from these wells. ASRD, with the support of Alberta Environment has indicated that a preliminary groundwater impact assessment will be required as a condition of any authorization to proceed with weir modifications. Due to ongoing operational problems with the wells, it is recommended that a groundwater monitoring program be implemented irrespective of the proposal to modify the weir.

Step 3 – Environmental Impact Assessment
An Environmental Impact Assessment (EIA) will be necessary to satisfy the conditions of various regulatory approvals that would be required should the project proceed. A component of the EIA would be the Biophysical Impact Assessment (BIA) that the City of Calgary, Park Planning & Development has indicated must be conducted “before a single alternate design can be selected”. The City requires that the terms of reference for such a study be resolved with Parks Resource Management and that the scope include both shorelines, Pearce Estate Park, proposed parking areas as well as construction staging areas.

The EIA would also include a detailed evaluation of the potential impacts of the proposed project on fish habitats. The project proponent must demonstrate that the “no net loss” policy established by Fisheries and Oceans Canada pursuant to the Federal Fisheries Act can be satisfied. This policy is also supported by Alberta Sustainable Resource Development.

The EIA could be conducted simultaneously with the Groundwater Study (Step 2).

Step 4 – Preliminary Engineering Design
It may be prudent to delay the preliminary engineering design until the Groundwater Study and the EIA are complete, as the results of the these two studies could have considerable influence on how the engineering design proceeds from the current level of detail.

It is extremely important that the recreational consultant work closely with the engineering team throughout the Preliminary Engineering Design phase, which will expand and refine the concepts presented in this pre-design study. The Preliminary Engineering Design phase should include a physical hydraulic model study, which is considered essential for a project of this magnitude and complexity.

Step 5 – Permit Applications
The filing of applications for various regulatory approvals could take place concurrent with Step 4. It is anticipated that approvals will be required pursuant to the following federal and provincial and legislation. Various other authorizations will be required from the City of Calgary and Alberta Sustainable Resource Development, as discussed in this report.

• Fisheries Act (Federal)
• Navigable Waters Protection Act (Federal)
• Water Act (Provincial)
• Public Lands Act (Provincial)

Step 6 – Detailed Design and Tender Document Preparation
This is the final stage in the design process. It involves the preparation of detailed construction drawings, specifications and tender document package.