Emergency Works: Coordinated Environmental Delivery Across a Multi-Infrastructure Corridor

Cornice supported CN Railway’s emergency response team in the planning, regulatory coordination, and environmental oversight of emergency works on the railway near Chilliwack, BC.

The project addressed a sudden stream avulsion that redirected flows from a 200+ ha watershed into a smaller, lower capacity historical drainage system, resulting in flooding and partial rail grade failure. The event introduced immediate and ongoing risk to a shared infrastructure corridor including railway, Highway 1, and the Trans Mountain pipeline, as well as downstream First Nations lands.

Project Control Support in Practice

This project reflects Cornice’s role in complex, time-sensitive environments:

• Aligning regulatory, technical, and construction requirements

• Supporting client decision-making under uncertainty

• Integrating multiple stakeholders and disciplines

• Maintaining environmental compliance while enabling delivery

Cornice operated as a coordinating layer between field execution, regulatory frameworks, and project leadership—ensuring clarity, structure, and accountability.

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The Challenge

The project required rapid coordination under emergency conditions, with several concurrent constraints:

• Active hydrological instability due to ongoing avulsion and sediment transport

• Risk exposure across multiple infrastructure systems (rail, highway, pipeline)

• Requirement for emergency regulatory approvals (provincial and federal)

• Engagement and coordination with First Nations and multiple agencies

• Limited baseline data and evolving field conditions

• Need to align design, approvals, and construction within a compressed timeline

  The work needed to proceed prior to the next high-flow event while maintaining environmental compliance and minimizing downstream impacts.

The Approach

Regulatory Coordination

• Supported securing emergency authorization under:

  • Section 93 Order (BC Water Sustainability Act)

  • Fisheries and Oceans Canada Section 35(2)(b) Emergency Authorization review and Letter of Advice

• Coordinated with provincial regulators to align scope, timing, and mitigation measures

• Supported communication pathways with Ministry of Transportation, Trans Mountain, and First Nations representatives

Environmental Planning and Technical Input

Design intent focused on restoring flow to the original channel and reducing long-term avulsion risk.

• Prepared the Environmental Protection Plan and subsequent official correspondence to reflect evolving site conditions

• Assessed fish and fish habitat potential using desktop analysis and field verification

• Defined site mitigation measures for:

  • Sediment and erosion control

  • Flow diversion and staged channel reinstatement

  • Fish monitoring and salvage

Construction Integration and Field Support

• Supported execution strategy to prioritize construction in the dry where feasible

• Advised on staged diversion of flows back into the original channel to manage turbidity and channel stability

• Integrated environmental monitoring with active construction activities, including coordination with Assuage Environmental

Key construction elements included:

• ~870 m continuous offset retaining berm

• Downstream berm to protect adjacent lands

• Catchment basin and opposing spurs to manage sediment deposition and reduce debris flow risk

Adaptive Management

• Adjusted mitigation measures in response to observed conditions, including turbidity and channel response during flow reintroduction

• Supported decision-making during temporary work stoppage to allow for additional engineering and stakeholder review

• Maintained alignment between field conditions, regulatory expectations, and client objectives

Outcome

• Flow successfully restored to original channel alignment

• Infrastructure risk reduced across rail, highway, and pipeline systems

• Regulatory requirements met under emergency authorization pathways

• No major environmental incidents during construction

• Fish presence assessed and managed; no significant impacts identified

Construction progressed efficiently under emergency conditions, with environmental mitigation measures implemented throughout.