Measuring and reducing carbon for HS2 Enabling Works

Our team provided design services for a series of enabling works for High Speed 2 in Northamptonshire, including new highways construction, diversions, drainage and landscaping.

A key requirement in the contract was to accurately measure the carbon footprint at each design gateway and to develop solutions to meet HS2’s target for a 30% carbon reduction compared to a standard reference baseline.

Challenge

The challenges in this project lay both in developing the low carbon design solutions and in creating a carbon measurement approach that:

• could be applied consistently and repeatably at each design gateway stage to quantify savings
• adapted to a changing level of information as the design evolved from concept to detailed
• integrated effectively with data from the BIM system
• met HS2’s highly demanding and industry-leading technical standards documents (which evolved during the course of the work) for carbon assessment, life-cycle analysis and materials efficiency.

Solution

Our design solution provided a 33% carbon reduction, exceeding HS2’s target. This was achieved through a mixture of design optimisations for materials efficiency, substitution with better-performing products, and making best use of the landscaping design for carbon sequestration.

Interesting trade-offs explored in the design and carbon measurement work were the balance between construction-stage carbon and lifetime carbon impacts—particularly with regard to the longevity and expected maintenance requirements of materials, as the life-cycle assessment (LCA) was required to cover a 120 year asset lifetime in HS2’s technical standards.

To measure carbon at each design gateway and compare it to the reference baseline, our approach was to use a mixture of product-specific LCA data where available, project-specific calculations for other materials, and a verified woodland carbon tool for sequestration calculations. This approach was selected because it could be easily tailored to the information available at each design gateway, providing more insight and flexibility than a generic lifecycle assessment package, while meeting HS2’s demanding technical standards documentation.