Construct - Issue 49

Project

FLOOD FOCUS

TARGETEDMAINTENANCE IS ENSURINGTHAT RESIDENTSREAP THEBENEFITSOFAPROGRAMME TOREPLACEDRAINAGE INFRASTRUCTURE

New drainage infrastructure

Specialist teams from the London Borough of Croydon and FM Conway are working in partnership to tackle long-term surface water flooding problems with a programme of regular maintenance that targets blocked and damaged drainage infrastructure. “The programme came about because we had a number of hotspots that flooded every time it rains,” explains Daisi Osibona, Croydon Council’s senior engineer for network maintenance. FM Conway senior engineer Naveed Aziz says that Croydon’s susceptibility to surface water flooding is due to the hilly nature of the area’s terrain, adding: “Geographically, the borough is split into two halves. In the north, most surface water run–off goes into Thames Water’s storm sewer network. The south half sits on good draining chalk, and surface water runoff goes into soakaways, which Croydon Council maintains. Over the years, some of these soakaways have accumulated compacted silt. Some are over

100 years old, which explains why they are starting to fail – they are reaching the end of their design life.” Replacing soakaways can be complex, especially under the carriageway. New soakaways are made from perforated precast concrete rings that can be 3m in diameter and 4m deep, requiring specialist equipment and procedures. “These are confined spaces, so we have risk plans, breathing apparatus, and people with specialist training,” explains FM Conway’s service delivery manager Rob Polley. “We’ve got a very experienced team of operatives. Because these are categorised as high-risk works, we have temporary works permits in place and the team works closely with the local community, bus companies, TfL and neighbouring local authorities to address any concerns before starting work.” Residents are already seeing the benefits of the programme and its focus on long-term flood alleviation across the borough.

is targeted at flooding hotspots

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