Strutts Centre, Rain Garden Project
The contents of this page between the line are copied from the Sudsdrain Web Site and simply reformatted to fit in with our web site.
The Strutts Centre is a former school, now run by a trust as a Community Centre. It is well used by many groups, including the Environment Agency (EA) and Trent Rivers Trust (TRT) who hold meetings there. It is a Grade II listed building in the Derwent Valley Mills World Heritage Site. A former caretaker’s house and a children’s nursery are located to the north east of the playground with an extensive area of green space rising up to the site boundary.
Figure 1: The main entrance to the Strutts Centre
The EA was keen to have a sustainable drainage system (SuDS) demonstration site in the area to encourage people to have domestic raingardens to cumulatively improve water quality in rivers and reduce flood risk. The water from this site discharges into the River Derwent after being treated at the nearby sewage treatment works. The Derwent is a large river and although this project would not make a demonstrable difference to water quality in the river, its value lies in demonstrating the link between rain water reaching and leaving homes and gardens and in giving a practical example of how we can all make a difference whilst still having beautiful gardens. The site was chosen because of its high visibility as a demonstration project and because the owners were happy to be involved. The site is visible to passers-by and is used by hundreds of people each week.
The project’s aims were:
The trustees of the centre were keen to engage with the project. Their focus hitherto had been mainly on interiors and this project brought extra attention and resources to their considerable outside space.
The site is 0.86 hectares in size. It has an approximate impermeable area of 0.6 hectares and small permeable areas that provide of 0.26 hectares of green space. Behind the school building is an extensive tarmac surfaced former playground, now used as a car park. An access road links this to the east of the school with another car park and the A6 Derby Road as it runs through the town. An area of formerly mown grass where there used to be two cottages now houses the main raingarden.
The design uses a linear raingarden in front of the old caretaker’s house, a collector grating (dubbed a ‘raincatcher’) into a short swale. This delivers runoff into the main raingarden which also takes water from the main Strutts building.
Figure 2: Brick rain channel and linear raingarden in front of the old caretaker's house
Figure 3: Meandering channel (foreground) flowing into the main raingarden (background) immediately after planting spring 2015 and in summer 2015.
Figure 4 Inlet from what the community described as ‘raincatcher’ grating across the access road. The headwall is mitred, with stainless steel inlet pipe and granite sett surround into the short swale.
How it works
SuDS retrofit can be described as ‘the art of the possible’. In order to determine what was possible at the Strutts Community Centre a SuDS Audit was undertaken to identify opportunities with recommendations on prioritised actions. This was based on a topographic survey and site visit by the designer and provided a prioritised evaluation of a range of options. This approach was useful in appraising options and choosing the preferred ones with funder and owners and would be a useful approach for other projects.
The creation of a raingarden designed to release a controlled flow of clean water to the combined sewer, bringing a range of benefits to the community, was identified as the most cost effective action. Once this idea was proposed the suggestion of a second, domestic scale raingarden that could be created on a typical house came from discussion with members of the local community. This was built outside the old caretakers’ house and linked to the first raingarden.
The volume of water to be managed by the SuDS components was calculated using the area of roof and road that contribute to the basins, and an appropriate storm return period, that reflects the likelihood of increasing amounts of rain, discharging to the sewer at 5L/sec/hectare.
The volume selected for the small domestic raingarden outside the old caretaker’s house was calculated for the 1 in 2 year return period to reflect day to day runoff from an average house in the Belper area. The 1 in 10 storm return period was used for the main raingarden to retain water from a larger storm event likely to cause local flooding during more intense rainfall events over a prolonged wet period.
Specific Project Detail
The site lies within the Derwent Valley Mills World Heritage Site. The Strutts Centre and wider community were enthusiastic landowners and project partners. They easily understood the concept of SuDS and were keen to have another beneficial and interesting aspect to the community centre.
Project management was by TRT who:
The EA funded the project and provided technical and project management support as required. They also filmed the video and helped with publicity. The EA were keen to deliver projects which meet their objectives in partnership in this region. This flexible approach paid dividends by supporting the TRT to take on and successfully deliver their first SuDS project and more broadly it supported the TRT to develop skills and confidence in urban river work.
Designers Robert Bray Associates (RBA) used initial meetings and site visits to consult with the clients and draw up a SuDS audit. This guided the selection of the most appropriate solutions. The RBA team then drew up detailed designs and advised the clients through the process of tendering for contractors. They worked closely with contractors Pugh-Lewis and Trent Rivers Trust, drew up detailed planting plans and maintenance guidance and even took a leading role at the community planting day! They were always on hand with advice and answers to questions and provided graphics for the interpretation panels. Pugh-Lewis Ltd. delivered the project conscientiously, on time and on budget.
Figure 5 Illustration of SuDS Audit
Early discussions with the local planning authority established key parameters such as not adding anything more than 1m above ground level or excavating more than 1m below ground level which were adhered to and avoided the need for planning permission.
Richard Bett, a local artist, provided the stainless steel interpretation. The idea was to visually enhance the SuDS, picking up on the stainless steel used in the spouts and to interpret the scheme to all ages, including the children and parents on the nursery which uses the site. By creating something resembling a ‘treasure trail’ they draw people into the SuDS train as the water flows through it. A physical working model of domestic SuDS was built by TRT staff with hidden talents! It has proved very popular and has ‘toured’ more than 10 public events over the summer of 2015 showing the pubic how SuDS work. A two minute video of the model can be seen here thanks to You Tube
Figure 6 SuDS model
An interpretation panel and bespoke stainless steel signs which aims to engage people on following and understanding the SuDS management train were installed, ensuring they keep with the building’s historic status.
Figure 7a: Interpretation panel showing a cross section of the main ‘raingarden’ looking towards the Strutts Centre.
Figure 7b: Interpretation board cross section
Figure 7c: Interpretation board cross section
Maintenance & operation
The substrate was clay and a humus-rich soil was added to both raingardens along with the topsoil that was lifted and stored during construction. Both raingardens were planted with perennials. Plants were selected on the basis of being suited to both wet and dry conditions with some species as erosion control in areas of highest gradient. On the bank side plants which thrive in drier conditions were chosen while at the top of the banks plants which provide ground cover to reduce erosion were selected. The basin was also sown with Pictorial Meadows seed mixes for immediate visual impact. In hindsight this mix, on the fertile soil, ‘drowned out’ some of the perennials so a less dense sowing would be recommended in future.
The aim was that the raingardens would, once built, belong to the Strutts Centre. However, as the design and build process had been managed by TRT, albeit with careful consultation and involvement of all, the transition from ‘their project with us’ to ‘our raingarden’ was not automatic and needed considerable support.
Most of the existing Strutts Centre volunteers had little spare time so a specific team was recruited by TRT from people who contacted the centre. The Project Manager invested time irrigating the planting through a very dry April 2015 to keep the plants alive and into recruiting, gardening with and supporting the volunteers. She ensured that they were well linked with the Centre’s other volunteers and trustees to ensure that the raingarden would be looked after through the first and future years.
The designers helpfully provided a brief, two page maintenance plan to advise on future gardening requirements and they also gave advice by phone when required.
Figure 9 Extract from maintenance plan
Monitoring and evaluation
Challenges or lessons learnt
Budget and Funding
Funding was initially from DEFRA’s Catchment Restoration Fund, with significant further funding from the EA which included the model and launch. Severn Trent Water paid for much of the interpretation.
Total budget: £49,200.
A Strutts Perspective
We could not and would not have spent this much on this type of project, we would have been unable to justify such expenditure. Therefore we are grateful for the input from the agencies involved. However, it is sad to say that little acknowledgement of the input from Strutts as been given. Further, despite assurances that the project would be cost neutral to Strutts this has not been the case. For the first two months our water rates were inflated by a considerable margin as the planting was kept alive through a very dry period. Maintenance of Suds is a bit more complicated than the experts would have you believe. This is particularly true during the first few years until the planting is well established, further so far our Suds is looking a bit grim in the winter.
However, overall I would say it is a positive addition to the site and the project. I guess you might also accuse me of a bit of bah humbug against the rosy picture painted of Suds.