Work has now started above ground level after months of preparatory work below the surface of Old Town Street and New George Street.
Three rain gardens have now been installed outside the House of Fraser store as part of a Sustainable Urban Drainage Scheme and work on the landscaping and planting above will begin shortly.
The rain gardens are essentially big holes that have been dug in the ground, then reinforced and layered with material so that at times of very heavy rainfall, the tanks can hold water, helping to reduce the risk of flooding. They act like a giant plant pot, storing water to irrigate new plants and trees that will be part of the new landscape.
The rain gardens range in size from 16 cubic metres to 30 cubic metres and can handle up to 54 cubic metres of rainwater. And if there’s more rain, there is now a new storm sewer deep beneath New George Street to take the excess and keep flood water from combined sewer system.
The new storm sewer system is a series of large plastic pipes – the largest 1.5 metres across and acts as a storage system during heavy rain, holding around 215 cubic metres of rainwater and releasing this gradually via a constrained outfall, known as a hydrobrake.
As well as the rain gardens there will be five more traditional gardens and other seating areas.
The scheme has moved on since contractors Morgan Sindall construction took over the site. There’s been some further revisions to the scheme, including more seating and more trees to be planted. There will be a total of 28 semi mature trees which are more resilient to an urban setting as well as the four existing large mature trees.
Proposals for a play area have changed, given the exciting proposals for a destination play village unveiled for Armada Way, there will be more planted landscaping instead.
In order to finish the entire scheme however more funding is needed and a decision is being signed this week to award a further a £6,077,134 contract to Morgan Sindall.
Councillor Lowry said: “I appreciate increased costs is not good news, but this project was conceived seven years ago and the economic landscape is now completely different. We have had a pandemic, the war in Ukraine and like other infrastructure and construction projects up and down the country, this has been massively affected by inflation pressures, the cost of material and supply chain issues.
“The projects had its own challenges as well. There’s been some incredibly tricky issues along the way that all had to be tackled and solved, numerous voids in the ground, Blitz rubble, filled-in cellars – a Victorian culvert – which was another recent discovery – as well as the maze of utilities. The design team have been back to the drawing board a number of times to adapt plans to the conditions.
“We have to finish this scheme to transform the look and feel of the city centre.
“The work that’s been taking place beneath the ground is going to be crucial if we are to encourage future investment. We have an elderly sewer system and taking rainwater away from the combined system will ease pressure on it and help prevent future flooding.
“The scheme will look amazing and it will help revitalise the city centre."
The scheme plays an important role in the city’s flood management strategy and its Climate Emergency Action Plan.
The sustainable urban drainage system means that every drop of water which falls in the area can be offered for the planting to feed, with the surplus stored in underground tanks. The three rain garden tanks are also capable of holding back 75.5 cubic metres of storm water in the event of heavy rainfall.
Although the other gardens in the project don’t provide additional storage as they are not part of the SUDs drainage system, they help to reduce the surface water run-off to the combined sewer and water channels into them to water the trees and other plants.
Above the surface new granite paving is going to be laid to make the area much more attractive, less dated and tired and reduce the likelihood of trips and falls. There will also be new street lighting, decorative lighting to create a wow factor after dark and improved CCTV coverage,
The scheme includes an events space at the junction of Old Town Street and New George Street equipped with power and water and capable of supporting small events and performances.
The works are funded from the existing project budget for Old Town Street and New George Street which includes external grant funding from Transforming Cities Fund, Local Economic Partnership, and Historic England’s Heritage Action Zone.
In order to award this contract, an additional allocation of £2,764,767 funded through corporate borrowing needs to be added to the capital budget of the Old Town Street and New George Street public, increasing the total cost to £16,752,850.