Project Details


Upper Pitt Street


Liverpool, England


June 2022

About The Project

As England’s third largest city and major port, Liverpool has a rich industrial heritage. However, since the demise of the shipping industry, Liverpool, as with many cities, suffered its fair share of urban decline, with previously bustling centres of business and busy neighbourhoods becoming derelict and unloved as the population shifts to newer, more in vogue areas. Fortunately, over the past few decades there has been a flurry of redevelopment initiatives to address this decline, all placing Liverpool firmly as one of the UK’s up and coming business destinations.

The urban rain garden at Upper Pitt Street, is an exemplar project (100% externally funded through the EU URBAN GreenUP project –, showcasing how landscape design combined with SuDS principles can be successfully retrofitted across our cityscapes.

What we did

Green-tech Specifier has been involved with manufacturing soils since 2004 under the brand name Green-tree. These soils are widely regarded to be amongst the best in the country, suitable for a wide range of standard and specialist landscaping purposes.

With the increasing popularity and demand, in many cases as part of the planning conditions, for green roofs and rain gardens, Green-tree offers a wide range of lightweight green roof and podium substrates, as well as rain garden and bioretention soils, all using our ever-popular British Standard manufactured soil as a base.

In this instance, as Liverpool had no previous experience using rain gardens as a “green solution”, it was proposed to create a test area to demonstrate what could be achieved.

Working in partnership with the Sports Turf Research Institute (STRI Ltd), Green-tech supplied three different bioretention blends for testing:

Blend 1 is the standard Green-tree bioretention mix, featuring screened silica sand, green compost and blown clay particles. This provides sufficient permeability to avoid waterlogging, while at the same time providing enough nutrients and organic matter for the shrubs and other vegetation.

Blend 2 is Green-tree’s High Performance bioretention soil, which has been improved to allow a greater percolation rate, whilst maximising the ability to sequester pollutants from the surface runoff.

Blend 3 is an experimental custom soil containing brick fragments, that in theory should aid permeability, whilst improving filtration. It will be interesting to see how this performs against the more traditional mixes.

The performance of each bed will be monitored by Liverpool City Council, in collaboration with the University of Liverpool and The Merseyside Forest organisation.

The various testing parameters will include:

Water flow during storm events and the velocity of discharge.

Using moisture probes to monitor both moisture and temperature levels between the beds.

How the different soils affect: vegetation, pollinators, water quality (and pH levels) and air quality

Pictures courtesy of Martha Redman STRI, Juliet Staples LCC, Dan Dean Photography

It is great to be involved with what will hopefully be the start of many similar projects for Liverpool City Council. Working with both STRI and Polypipe over the years, we were delighted to be able to supply the custom bioretention substrates and look forward with interest to seeing the test results for the various blends.

Mark Wood – Business Development Director – Green-tech Specifier

STRI have worked with Green-tech for several years now. Throughout this time, Green-tech have provided invaluable support in developing and delivering customised substates to meet our ever changing, often challenging, design requirements across a variety of sectors.

Martha Redman – Chartered Landscape Architect – Sports Turf Research Institute