Carlington Heights Pump Station Upgrade

Project overview

The City of Ottawa has initiated the planning process for the Environmental Assessment (EA) Study for the proposed Carlington Heights Pumping Station (CHPS) Upgrades. The main objective of this study is to prepare the functional design and phasing plan for the proposed CHPS site upgrades in accordance with the Municipal Class Environmental Assessment (MCEA) requirements. This will include identification and evaluation of a range of alternatives that focus on potential pumping station and suction/discharge piping upgrades.

The following information has been prepared to provide an overview of the project and an outline of the study process to date.

Project background

The CHPS was originally constructed in 1963. It draws water directly from the adjacent Carlington Heights Reservoir and supplies a population of over 250,000. The City of Ottawa is divided into various water system pressure zones based on providing customers with an appropriate minimum and maximum water pressure. Figure 2 shows the City's various water pressure zones. The CHPS is currently a two zone station serving the Meadowlands East (ME) and 2W Pressure Zones. The 2W Pressure Zone also supplies all of the water t the 3W and Barrhaven (BARR) Pressure Zones. The station is a back-up source of water for Zones 2W, 3W, and BARR and is the only source of water for the ME Pressure Zone under normal operating conditions. These zones are noted on the following map.

The 2008 Infrastructure Master Plan identified the need for additional capacity at the CHPS. The output of this pumping station is limited by pump capacity and the size of the suction and discharge piping near the station. Improvements are needed so that this pumping station can provide adequate emergency supply to Zones 2W, 3W, and BARR. These improvements will also add capacity to accommodate projected urban growth in these zones.

Environmental Assessment requirements

This project has been planned as a Schedule 'B' project under the MCEA document (2011). The purpose of the Class EA study is to confirm project need and justification, document existing environmental conditions, examine alternatives and potential impacts, and recommend a preferred alternative for the upgrade.

Consultation

Communication and consultation are an important part of the study process. The City will engage the public through a variety of methods including information posted on the City Web site and meetings, as required, with community associations and approval agencies. The project also benefits from a Technical Advisory Committee that provides guidance and support through the planning and design processes.

Existing conditions

Existing environmental conditions are characterized to determine sensitivities and provide a baseline against which the effects of each of the alternatives can be assessed. Overall, the baseline data was collected and analyzed for key environmental parameters in order to:

• Provide an understanding of existing conditions;
• Allow for predictions of how the proposed project may cause these environmental conditions to change; and
• Allow for predictions of how adverse effects can be mitigated and beneficial effects enhanced.

Key social, natural, and geotechnical conditions are represented on the following maps.

• Areas of archaeological potential surround the water reservoir beyond the existing access roads
• on-road cycling routes are identified outside of the study area
• Off-road cycling routes and multi-use pathways are located through Carlington Woods extending to the east and west of the study area
• Sanitary and storm sewers are located beneath the majority of the roadways
• Carlington Woods (Urban Natural Area 121) surrounds the reservoir and pump station to the south, east and west
• A water body resulting from the snow storage is identified west of Clyde Avenue
• A former landfill area at McBride Street and Raven Avenue was closed in 1953
• The depth to bedrock varies from 0 to 15 metres across the site

Evaluation criteria

Each Alternative was assessed against a series of criteria for the purpose of selecting a preliminary preferred alternative. Included in the table below is the rationale for the selection of the criteria and the indicators that will be used to assess the impacts/rate the effect.

Table 1 Evaluation Criteria

Alternative solutions

Alternative solutions were developed based on an understanding of the existing economic, technical, social/cultural, and natural and physical environmental conditions. Technically, these alternatives address existing condition-related issues, hydraulic limitations (pumping, suction and discharge), electrical limitations, and physical space limitations, within the existing pump station.

Eight alternatives were developed as follows.

• Continued use of all existing pumps
• Addition to existing building to house additional 2W pumps & standby power
• New suction connection through the west reservoir wall and continued use of existing suction
• New discharge line for new pumps

• Ultimate demolition of existing station
• New station & all new pumps tight to reservoir berm
• New suction connection through the west reservoir wall

• Ultimate demolition of existing station
• New station set into the reservoir berm tight to the reservoir wall to reduce suction line lengths to a minimum
• Gravity connection for 2W off the existing suction line but interconnected inside the station – and abandon the existing and long length of dead watermain

• Ultimate demolition of existing station
• Reinforcement of the reservoir roof & construction of walled-off pump wells
• New vertical turbine pumps to the reservoir floor
• Existing suction line retained as a 2W gravity connection
• New discharge lines for 2W and ME – and abandon existing

• Continued use of all existing pumps
• Addition to existing building to house additional 2W pumps & standby power
• New suction line off the 1W connection to improve net positive suction head available

• Ultimate demolition of existing station
• New station & all new pumps tight to reservoir berm
• New suction connected directly to the Zone 1W reservoir inlet pipe
• New piping connections to Zones 2W and ME along the south side of the reservoir

• Ultimate demolition of existing station
• New station and all new pumps tight to berm on east side of reservoir
• New suction connection directly off the 1W connection removing all constraints on reservoir level control
• Existing suction line retained as a 2W gravity connection (but an internal connection could be provided to allow it to be abandoned)
• Existing station is retained and dedicated to Zone ME

• Ultimate demolition of existing station
• New station & all new pumps tight to berm on east side of reservoir
• New suction connection directly off the 1W connection removing all constraints on reservoir level control
• Existing suction line retained as a 2W gravity connection (but an internal connection could be provided to allow it to be abandoned)
• New discharge lines for 2W and ME – and abandon existing
• Option 6 but located on the south side of the reservoir and set partially into the berm

Capital costs for the various options ranged from $4.4 M to $7.0 M. The estimates costs include construction costs, hydro allocations and engineering as well as a contingency.

Each alternative was evaluated and assessed a comparative score out of 10 for each criteria indicator with 10 representing the least impact/best result.

Sensitivity analysis

The weighting of each of the criteria groups were considered in evaluating the sensitivity of the evaluation results to variability in criteria weighting. Initially, weighting values for all criteria were scored equally. The weightings were then adjusted to varying degrees to test their influence on the outcome. Examples are illustrated below.

Options 2 and 6 are ranked in the top three when Economics, Natural and Technical are weighted high. Option 6 loses its top-three ranking when Social/Cultural is weighted high, reflecting the increasing influence of visual impacts and construction disruption. Options 2 and 6 consistently ranked amongst the highest in the various weighting scenarios. 

The key benefits of Options 6 and 2 are as follows:

Option 6

Key Benefits

• Uninterrupted operation of existing pumping station during construction of the new station
• Shorter construction period compared to options involving additions to the existing station
• Maximizes operational flexibility of the reservoir
• Good access for operations and maintenance
• Frees up land to west of reservoir for potential future uses.

Option 2

Key Benefits

• Uninterrupted operation of existing pumping station during construction of the new station
• Shorter construction period compared to options involving additions to the existing station
• Facility essentially hidden from view of nearby residents and users of the green space
• Reduced hydro supply extension compared to Option 6

Preliminary preferred alternative

A major advantage of a suction connection on the reservoir inlet/outlet line (Option 6) is that it effectively increases the volume of available storage in the Carlington Heights Reservoir by approximately 20 ML. This has both operational benefits and economic benefits. Despite the functional and operational advantages of Option 6, the environmental impacts of a major facility on the east side of the reservoir could be substantial, especially considering the fact that technically acceptable locations were available on the west side and would essentially be hidden from view for recreational users of the area (Option 2). Taking into account Option 6 represented the preferred technical solution but Option2, which places the station near the existing site, would be less intrusive, an option combining the advantages of both was developed as the Preliminary Preferred Alternative [ PDF - 371 KB ].

Impacts and mitigation

The CHPS will be designed and implemented with the benefit of contemporary planning, engineering, and environmental management practices. Best Management Practices (BMPs) will be implemented including:

• Erosion and Sediment Control Plan
• Construction and Traffic Management Plan
• Emergency Response Plan
• Environmental Protection

Following the incorporation of the BMPs, site specific, mitigation measures were identified to reduce potential negative effects. These include:

• Geotechnical Considerations
• Butternut Assessments (if required)
• Landscape Plan for new station
• Public Communications Plan
• Pedestrian Detour / Management Plan
• Hoarding and Exclusionary Fencing

Schedule and next steps

The study team will review comments and address concerns or questions that are raised by the public. Thereafter, the next steps in the study process are to:

• Confirm the preferred alternative solution (early summer)
• Prepare the EA report (early summer)
• Committee and Council meetings (summer)
• 30 Day Public review of EA Report (summer/early fall)
• Functional Design (fall)
• Design (winter and spring 2014)
• Construction (starting 2015)

Comments

Tell us what you think. Provide your comments by mail or e-mail by June 28, 2013.

Chris Rogers, M. A. Sc., P. Eng.
Senior Project Engineer
Infrastructure and Water Services Department
City of Ottawa 110 Laurier Avenue West, 4th Floor
Ottawa, ON K1P 1J1
613-580-2424, ext. 27785
E-mail: Christopher.Rogers@ottawa.ca