Full Title - The Birmingham Gateway Project
Managing Construction Fire Safety within Highly Complex and Densely Occupied Infrastructure Projects
By Reece Walker, Senior Fire Engineer
Abstract
In September 2015, Arup was part of a project delivery team that completed a major rail infrastructure refurbishment in the UK. Arup fire engineers were permanently onsite throughout the five-year construction programme to provide project fire safety advice and deliver more than 400 risk assessments. Fire engineering was a fundamental part of the construction project since it allowed work to continue in a fully operational station and shopping centre environment.
Introduction
The Health and Safety at Work Act is the principal legislation regarding health and safety in the UK. It imposes general duties on employers and stakeholders for reducing risk to people due to workplace activities. Beneath this ‘umbrella’ act there are further regulations, such as the CDM 2015 Regulations and RRO 2005, that relate to fire safety.
The main fire safety guidance document for construction work in the UK is HSG 168. This outlines best-practice methods for both fire prevention and risk assessment undertaken by responsible parties during “straightforward or less complex” construction work. The document recognises that “more complex and high-risk projects are beyond the scope of this guidance and you may need additional help with these from a competent specialist.”1
We, as fire safety engineers, therefore need sufficient knowledge of construction fire safety to be provide assistance to the construction industry during high-risk projects.
The Birmingham Gateway Project
The Birmingham Gateway Project was a comprehensive, multi-phased programme aimed to increase the passenger capacity of one of Britain’s busiest transport interchanges.
Figure 1. Gateway project atrium during the construction phase.
The construction work undertaken had a continuous and significant impact on the existing fire safety measures in the building. Work included the formation of a new Station Concourse, 3.5 times larger than its predecessor; demolition and re-construction of more than 80 retail units; and complete replacement of the smoke exhaust, fire alarm and sprinkler systems.
Understanding the Fire Safety Risks
Railway stations, like most densely occupied buildings, are generally designed with low-risk/low-combustibility circulation spaces and separation of risk spaces by fire compartmentation or sprinkler suppression. These measures, coupled with active systems for early warning (to occupants) and rigorous fire safety management for effective emergency response, provide a high level of protection from fire.
The Birmingham Gateway project created several challenges in maintaining these fire safety features during the interim phase. Areas under construction could not be provided with automated smoke detection due to the risk of false activations and subsequent evacuation of the station. Furthermore, the construction site spaces could not always be fully fire-separated from the occupied station due to constraints of the site.
The Role of the Fire Engineer
HSG 168 notes that “it is essential that fire safety measures are considered throughout all stages of the procurement and design process and implemented effectively during the construction phase”. Generally, the fire engineer’s focus during the design stage is identifying opportunities for performance solutions to enable instances of non-compliance in the building code. Their role is often complete upon approval of the design.
When construction begins, the principal contractor becomes responsible for managing fire safety on their site. The complexities involved with occupied buildings under construction can be underestimated, both at the design and construction phase, so seeking advice from a fire engineer in the initial stages is considered essential.
Stakeholder Engagement Process
A major project challenge was improving effective communication and co-ordination of the construction work and associated fire safety impacts among the multiple project stakeholders.
How do you deliver a complex project, whilst ensuring complete transparency, where all responsible stakeholders accept and fully understand the forever varying risk? In this instance, Arup created a stakeholder engagement and fire risk management process for the project to facilitate the principal contractor in fulfilling duties regarding fire safety.
The fire safety representatives for each stakeholder received ongoing risk assessments by Arup outlining the proposed work, associated fire risks and required mitigation measures. This process allowed continuous construction work to occur simultaneously in multiple areas and support the construction project milestones.
It was evident that the sheer scale of the refurbishment would require all work to be planned and co-ordinated with a fire engineer at the core of the temporary design process. By working closely with the principal contractor, Arup developed an understanding of construction methods and could assist the project team in proposing strategic changes to the station while continuing to maintain an acceptable level of risk.
Documentation, Implementation, Education and Enforcement
A crucial factor with phased construction work is that there are numerous temporary stages in each phase. Reliance on fire safety management and human intervention inevitably becomes part of the overall solution when final design active systems cannot be provided in full. To rely on this human element, the need for staff to understand their role is paramount in an emergency. As the key co-ordinator, Arup provided briefings, training and onsite enforcement of the temporary solutions to satisfy stakeholders that the risks were managed in accordance with the FRA.
The correct installation, operation and commissioning of both active and passive fire safety features are paramount during interim occupation, since such features are integral to the temporary phase. More often than not, fire safety systems such as fire alarm and detection, smoke control, fire dampers, and sprinklers are not fully installed per the project. That makes it important for all variations to be understood and documented when commissioning occurs for the temporary systems to be fully certified as fit for their intended purpose.
Emergency Response and Coordination
As the station transformed over the course of the project, so too did the emergency response procedures for both the station personnel and local fire service. Consultation with the fire service was vital throughout the project lifecycle to keep firefighters informed and provide comment on the ever-changing firefighter provisions.
The local fire stations were provided with regular familiarisation tours of the site to allow them to keep pace with the building changes, in recognition that the potential for firefighter confusion during an incident due to unfamiliarity of the evolving station layout was a risk that required mitigation.
Combination of Theoretical Modelling and Practical Management
A key part of the project was refurbishing all 12 sub-surface platforms below the station concourse. As portions of platforms were closed off from public use, train services were re-routed to the adjacent platforms. It became evident that simple egress calculations for the high populations and ever-changing conditions were not sufficient for identifying risks such as pinch points and converging exit routes with respect to crowding and queuing.
In response, Arup developed MassMotion, a 3D pedestrian model, that was used to track the changes to platforms and the concourse and demonstrate suitable egress conditions were being maintained. Where areas of crowding were identified, the layout of proposed hoarding was amended to suit and station staff were briefed to direct occupants to more under-used exits based on the modelling results to further ease queuing conditions.
The MassMotion outputs were used as part of a Required Safe Egress Time (RSET) and compared against fire dynamics modelling of station fire scenarios to understand the Available Safe Egress Time (ASET).
Figure 2. Image from the MassMotion 3D model of station platforms and concourse.
Fully Integrated Fire-Engineered Design
The final phase of the project culminated in the removal of all temporary fire separation between the most significant construction areas and the public occupied station. Removal of this temporary compartmentation was necessary to complete the physical work and final integration of the fire safety systems.
Subsequently, two levels of the construction site at the shopping centre retail level and station concourse (connected via a large atrium) were directly open to the operational station and platforms.
Since not all fire safety systems were operational, and site constraints restricted the use of smoke detection and sprinklers within the construction areas, the risk to the station was at its highest level during this time.
In conjunction with input from stakeholders, a series of strategic documents were formulated to create a building-wide fire safety plan over the six months running up to handover. This plan addressed the increased risk with a holistic solution incorporating both active and managed fire safety provisions and strict control over construction materials.
The station and construction site were being managed as a single, fully integrated space at this point, which required the station operator and principal contractor to align their emergency response procedures. Arup developed an emergency response plan for the construction site that was co-ordinated around the specific and unusual risk the work posed to the station and shopping centre occupants.
Conclusions
When working on the refurbishment of occupied buildings, the fire engineer, as part of the design team, should identify and explain the associated construction fire safety risks to their clients. The project hazard risk register is the first step in this process.
Without clear planning and advice from the fire engineer, the financial expenditure and delays associated with temporary fire safety measures can be a significant unforseen cost. Principal contractors should consider the need for in-depth fire engineering advice throughout the project lifecycle.
Today’s fire engineers, as the most-competent fire safety professionals, must understand the fire safety risks associated with refurbishment projects and be able to provide effective and innovative solutions for contractors during the construction phase.
Being able to integrate technical justification with practical solutions and robust emergency response procedures are fire engineering skills that are central to the success of these complex infrastructure projects.
Reece Walker, Senior Fire Engineer is with Arup
References
1HSG 168 - Fire Safety in Construction Guidance, 2nd Ed. 2010.