Strutts Centre Derby Road Belper Derbyshire DE56 1UU
Description 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 caretakers house and a childrens 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 projects 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.
Specific details Site area : 0.86 ha Return period : 1 in 2 year at Caretakers House and 1 in 10 year for the main basin. To our knowledge the raingardens have accepted all of the flows so far. Discharge destination : Combined sewer. By allowing rainwater to infiltrate and evaporate on site the oils and heavy metals from parked cars are diverted from the sewage system. The risk of overwhelming the sewage system during high rainfall events, leading to untreated sewage overflowing to the river was somewhat reduced. Although there would be greater water quality benefits were the water to discharge into surface water sewers. This location was chosen to show the public how raingardens and SuDS can have multiple benefits and are practical and achievable at domestic level too. Status Project start : August 2014 Consultation and design : September to December 2014 Construction : February and March 2015 Planting : March 2015 Interpretation installed and public launch : September 2015 SuDS model : completed early summer and toured some 12 public events summer 2015. SuDS video : September 2015. Awarded Britain in Bloom New Landscape of the Year : October 2015 SuDS used The design uses a linear raingarden in front of the old caretakers 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 caretakers 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: