| The works were instigated following a scour assessment of the road bridge which carries Stevenson Road over the River Don watercourse in Sheffield. The bridge is a double span masonry arch structure owned by Network Rail. CML were issued a contract for design and build under Network Rail’s Works Delivery Reactive Framework. |
The works were instigated following a scour assessment of the Network Rail owned road bridge which carries Stevenson Road over the River Don in Sheffield. The bridge is a double span masonry arch structure and CML were contracted for design and build arrangements under Network Rail’s Works Delivery Reactive Framework.
The design output required, was to provide cost effective scour mitigation measures to Pier 1 of the structure. The engineering design solution chosen was to install a double layer of 400mm (d50) rock armour around the pier 1. This facilitated a flexible construction methodology as works can be undertaken in both wet and dry conditions, as well as providing a low whole life cost from minimal maintenance requirements.
Prior to the physical works starting, a full ecology survey was undertaken and a public footpath closure (Five Wiers Walk) arranged. The methodology required the construction of a temporary access ramp into the site, installation of a “Geodam” to protect the river, the installation of rock armour scour protection, and the subsequent removal of the access ramp prior to site demobilisation.
The site compound was situated in a scrap yard adjacent to the work site on an existing hard standing. The access ramp ran from the scrap yard and then cross over a section of the Five Wiers Walk and into the water course. This allowed for seamless access/egress for machinery and operatives, while also providing a quick exit route in case of an emergency.
| Pre-construction planning arrangements included the arrangement of an ecology survey by a qualified ecologist. This survey highlights environmental constrains on the proposed works and is included within the Environment Agency (EA) permit application. The River Don watercourse is governed by the EA and a permit for both temporary and permanent works is to be granted prior to working within the watercourse. CML liaised with the EA at the earliest opportunity during the pre-construction phase, this involved submitting documents relating to the planned methodology, detailed design and temporary works requirements. CML have experience in working with the EA and were able to propose solutions to the EA’s requirements, such as: installing a temporary Geodam within the watercourse to isolate the working area; installing silt mitigation downstream in the form of silt curtains and completing daily watercourse pollution monitoring throughout the physical works duration. |
| Access to the watercourse and structure was restricted by the existing environment. Retaining walls were situated on both sides of the Riverbank, and the ‘Five Weirs Walk’ pedestrian footpath ran parallel to the River Don along with the ‘Eye of the Needle and Sweeping Birches’ lookout structure located downstream of the working area. CML liaised with the local council regarding the proposed works and agreed a footpath closure and diversion was required to safely complete the physical works. CML were restricted by the council to complete the works outside the summer holiday period which would reduce the foot traffic along the footpath whilst completing the works.
The site compound was situated on 3rd party land, utilising an existing hardstanding which was owned by Network Rail and leased to a waste facility. CML communicated with Network Rails property team to agree land access arrangements, by utilising existing Network Rail owned land it reduced costs to the project related to land access. CML protected the surface of the public footpath using steel road plates and installed a temporary access ramp from the footpath into the watercourse using rock armour and gabion stone. This enabled the use of bio-oil tracked dumpers and excavators to complete the rock armour installation works. |
During excavation for the rock armour installation, a surprising and potentially hazardous discovery was made in the form of several Unexploded Ordnance devises (UXO’s), buried beneath the surface. Immediately identifying the safety risks, our Site Manager contacted a specialist UXO clearance team who, without delay, had the tools and experience to deal with this type of device.
To mitigate against this risk should further UXO’s be uncovered, and to ensure the safety of the excavator operator whilst continuing with the excavation, we replaced the standard excavator with an 8-ton armoured excavator. This excavator had the capability to carefully uncover and manage any UXO’s, minimising risks to the site and the surrounding area. The UXO team remained on site during the excavation works to scan all excavated materials and the work area for any further UXO’s.
Discovery of the UXOs presented further issues; a gas pipe attached to the side of the bridge, directly above the work area, carried the potential to cause an explosion. CML promptly contacted the owner of the gas pipe and engaged in a discussion to determine the best course of action. It was agreed that the safest option was to reduce the gas pressure to the lowest possible level and establish emergency communication arrangements between all parties, ensuring that in the event of an emergency, the gas supply could be immediately shut off. A precautionary road closure was also put into effect across the bridge to maintain the safety of the public.
Throughout the process of managing the UXO situation, CML ensured all stakeholders involved with the scheme were updated including the Environment Agency and the local authority. The EA agreed to extend the working permit until the end of October allowing CML to complete the works within this timescale following the agreed extension of time agreed with the client team. Network Rail’s management team were informed daily on the progress and expected programme and commercial impacts in the form of Early Warning Notifications (EWN) and Technical Queries (TQ).
| This project has demonstrated the exceptional dedication and teamwork of the delivery team in dealing with unforeseen risks. The engagement with the Environmental Agency and Local Authorities, as well as the effective collaboration with our subcontractors, such as Centurion Site Services Ltd, and the UXO clearance team, demonstrated our commitment to the highest safety standards and efficiency. |
This cooperative approach not only ensured the project’s timely completion but also upheld the highest degree of safety, making it a testament to our company’s core values and its ability to deliver complex projects with excellence and responsibility.
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