Context

Classed as a conservation area, trees at St Peter’s Square in Manchester are of crucial importance to the environment. With proximity to the city centre, near the central library and the main metro stops, it was critical to provide a focal point that was characterised by good quality, extensive canopy cover; a space that was adaptive and attractive, fit for the future.

One of the most exciting aspects of the project was the way in which trees were integrated as part of the transport infrastructure, ie the tram stops. People spend so many days waiting for public transport and communing, it is only fitting that urban trees provide some respite from this somewhat monotonous daily experience.

Requirement

Both the clients and the designers understood the necessity of using a long-term solution for planting trees in such a densely populated urban environment with numerous above and below ground constraints. Tree pits are more than a basic hole in the ground. With adequate space, soil, irrigation and aeration, the pits are also designed to provide lighting and an integrated power supply.

Products supplied

GreenBlue Urban supplied 60 series StrataCells, Arborvents, bespoke tree grilles and Geonet for the 22 trees including the Japanese pagoda tree, the foxglove tree, the London plane and the pin oak, each having been grown in specialist nurseries for up to 7 years.

Outcome

When asked to comment on the scheme post installation, partners at City of Trees, as well as contacts at Manchester City Council, referred to the transformation of the space as transcending the merely physical.

It has encouraged a different use of the space, from a mere thoroughfare to a destination of choice in its own right for the moments between work meetings, before an evening out or a weekend taking in the culture of this thriving metropolis.

Described by the Manchester Evening News as a historic site steeped in democratic history, GreenBlue Urban is proud to have been part of a process that gives this space back to the people, and an accessible green space, that will deliver the ecosystems services for future generations.

Testimonial

"At St Peter’s Square, there was the ambition for a continuous hard surface to HGV loading requirements in the area where a lot of trees were supposed to be planted. The tree pits had to be designed for the entire life span of the trees which were planted at an already semi-mature size, so there was requirement for sufficient rooting space and soil, need of aeration, irrigation and drainage for this period. Our aim was to have maximum contact between the rooted area and natural surface air whilst the aperture around the trunk was limited by the structural concrete slab supporting the paving and the potential traffic on top. As the tree pits are between 16 and 25m², the area underneath the slab was quite large, as were the calculated forces. The cell system provided the ideal response to that challenge, as they could take the loading in the long term much better than mere structural soil, and minimise the risk of settlements. As the pits were constructed in an urban environment with a multitude of existing utilities, it was particularly advantageous that the cell system is highly flexible in layout, and easy to combine with root directing systems. The aperture was eventually covered with a steel grill whose frame was fixed onto the concrete slab, resulting in an entirely walkable surface."

– Latz und Partners

Tree pit system for St Peters Square, Manchester

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