Solutions for the water sector including quality monitoring, modelling, infrastructure design, engineering and asset management.
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The complexities and challenges of high-level solution development for overflow spill reductions.
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Impermeable area (IA) reduction via SuDS was calculated through the identification of areas which could realistically be removed and where SuDS systems could be viably installed. In this scenario, solutions were modelled, simulated and spill frequencies re-assessed.
Retrofitting SuDS to existing impermeable areas to reduce their contribution to the network can occur on a small scale, i.e. the roofs, drives and curtilages of private property. Whilst these features can positively influence a local environment, they introduce potential issues regarding agreements and access to carry out such work, which many be a lengthy, costly and complex process. The rate of refusal for this work to be carried out on properties should be accounted for to produce blue-green solutions that are more likely to realise the expected benefits.
Confidence in the connectivity of impermeable areas is important in producing the most reliable SuDS solutions, and surveys would have to be carried out in areas of uncertainty. This would require a significant amount of work and take valuable time, adding pressure to delivery of these solutions. Even with confidence in the connected areas, this project found that a very small proportion of solutions tested were able to achieve the overflow reduction target with a SuDS-only scheme. Hybrid solutions utilising both SuDS and traditional storage tanks offered more viable options, however grey-only solutions offered the highest proportion of viable options.
In carrying out the rapid high-level solutions development for high spilling overflows, it can be concluded that, ideally, solutions development calls for the collection, acknowledgement and understanding of details such as root causes of spills, contributing areas, hydraulically linked sites, treatment and network capacity, as well as the consideration of other complexities including the difficulties associated with retrofitting SuDS. The challenges associated with obtaining and compiling this data are considerable, however considering these aspects is likely to result in more viable and efficient solutions and an overall saving in terms of programme time and cost.