DescriptionNorth Street in Keighley is one of the few streets remaining in this historic town nestled in the South Pennines in Yorkshire. Built at the confluence of two rivers, the town has long been related to the mills, powered by these water courses, and the manufacture of textiles, and textile related machinery continued right up until ten years ago.
Over the past two hundred years the population of Keighley has risen tenfold, and with the rising population, traffic increases. Much of the town was remodelled in the 1960s, but the older parts of the town suffered from too many vehicles competing for too little road space.
Following several consultations, the local council decided to make some alterations to the road network in and around the town centre, to alleviate the traffic gridlock that was becoming a feature of the town centre.
The old Keighley College building that fronted onto North Street was demolished, making space for an additional traffic lane, and provided a public open green space. Existing street trees had to be removed to allow for the road works, so new trees were specified in large soil volume tree pits, supported with GreenBlue Urban RootSpace soil cell systems.
To maximise the value of the new tree planting, it was decided to use these tree pits as storm water attenuation and treatment pits, taking water from the carriageway, passing it through a stone layer on the top of the tree pit and then filtering it down through the Arborsoil Hydro soil mix provided for the root growth. The water then transferred through a clean stone layer to an underdrain to a storm water drain. This method of conveyance gives an acceptable level of pollutant removal and slows the water down so that the existing drainage network can cope with the increasingly violent storm events.
Working alongside City of Bradford Metropolitan District Council and SIG Geotechinical Ltd, the project bought together irrigation and aeration, Root Management for guidance along utilities, Mesh, Geonet and ArborSoil Hydro, specifically blended as a result of research and testing perfect for SuDS tree pits.
The trees have shown significant growth over the past two years, which is typical for trees planted in these systems; uncompacted soil with good porous surfacing allows maximum gaseous exchange, and every storm event washes fresh nutrient into the tree pit.
This project clearly displays how imaginative tree planting can provide numerous benefits without high levels of cost – and continue to provide these benefits for decades.