Innovative Rainwater Management for the Halifax Ragged Lake Transit Centre

To accommodate, maintain, store and recharge the new zero-emission buses, the Ragged Lake Transit Centre needed to be expanded. This investment in infrastructure was essential to ensure that the fleet could operate efficiently and sustainably. 

The project was not only representative of a strong environmental commitment, but also a response to new in-force regional regulations encouraging initiatives to reduce the carbon footprint of municipal infrastructure. This significant shift involved major adaptation of existing infrastructure, and the Transit Centre roof became a key component of this process. 

SOPREMA was called upon to play a key role in offering solutions adapted to this ambitious project, focusing on rainwater management and energy optimization of the building, thus ensuring sustainable and efficient facilities. 

The first challenge of AECOM’s architects was to take into consideration the environmental standards and regulations put in place by the City. Indeed, the City of Halifax follows the comprehensive infrastructure management plan Halifax Regional Municipal Planning Strategy, which focuses on carbon footprint reduction and sustainable resource management. The City’s requirements, such as respecting the Halifax Green Building Policy, promote the integration of ecological solutions into municipal buildings. This policy requires that any new project or expansion meet strict energy efficiency standards, with goals including reducing energy consumption, improving rainwater management, and increasing the use of sustainable materials.  

From the outset of the project, stakeholders were aware of the stringent requirements to be met. The project had to comply with the Halifax Stormwater Management Standards for Development Activities municipal policy, which requires the retention of the first 10 millimeters of precipitation during downpours across the entire site (land parcel and building, including the roof). In a region regularly exposed to frequent and intense rainstorms, this requirement constituted a significant challenge. 

To meet municipal stormwater management requirements, the initial specifications suggested a conventional roofing system with an EPDM membrane including a modular vegetated system and controlled-flow drains. The green system was to retain 51 litres of water per square metre during rainstorms. 

However, the design of this nearly 34,000 ft² system proved to be complex, as no single manufacturer could supply all the necessary components. As a result, the waterproofing, insulation and vegetated systems each came from different suppliers. 

This configuration further complicated the project, particularly due to the lack of a unified warranty for the roofing system as a whole. For the contractor, this was a real headache, as they would have to work with many different materials, each with their own specificities, technical requirements, and delivery times. Coordinating these various elements increased the risks, in addition to the lack of warranty for the system as a whole. This question of liability in the event of a problem was a major source of concern, as it was not clear who would be responsible for repairs if issues or leaks occurred. Above all, the long-term durability of the roof could not be compromised.