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Balancing The Challenges Of Legacy Suds In Scotland

Congress: 2015
Author(s): Roy Middleton, Doug Buchan, Stuart Cullen, Maria Lucey
Scottish Water1, Clackmannanshire Counci2

Keyword(s): Sub-theme 11: Key vulnerabilities and security risks,
Abstract

Introduction

Managing surface water is pivotal to minimising the impacts from storm runoff with Sustainable Urban Drainage Systems or 'SUDS' playing a significant role in mitigating these impacts in urbanised environments. In Scotland, nearly 2,000 'legacy' SUDS are known to have been completed prior to publication of 'Sewers for Scotland 2nd Edition' in 2007, in which improved technical standards and requirements are set out for SUDS to publically vest i.e. be adopted for maintenance with Scottish Water (SW). Following technical approval and planning permission, ownership and maintenance of SUDs starts privately with developers and/ or residents who may request vesting with either SW for curtilage drainage and/ or the appropriate local authority for roads drainage. Public ownership ensures appropriate SUDS maintenance regimes are in place to help protect people, property and the environment from storm water runoff problems. To this goal, SW is keen to work with SUDS owners, local authorities and other stakeholders to promote SUDS vesting to provide cost-effective and risk-based protection for Scotland, its people and its environment.

With the majority of Legacy SUDS privately owned and maintained, increased complaints over time have resulted from non- or under-performing and aesthetically poor looking systems. The effects of climate change including the increased frequency, duration and intensity of storm rainfall events have the potential to worsen these problems.

Methods/Materials

To address these growing problems and protect the public, the need to identify a new process to cost-effectively vest legacy SUDS into public ownership across Scotland was identified. From this, a 'pilot' or trial project was devised between SW and Clackmannanshire Council (CC) across the Clackmannanshire area in central Scotland aimed at assessing the challenges, risks and costs in vesting privately-owned legacy SUDS into public ownership. The results, experiences and lessons learnt from this pilot project were planned to help steer the development and application of a new robust set of processes for risk-based public vesting of other legacy SUDS across the wider Scotland.

Initially 15 legacy SUDs sites were identified covering a broad range of developments and private ownership likely to be representative of Scotland-wide legacy SUDS. These 15 sites included a mixture of ponds, basins, filter trenches, swales, a wetland and geocellular storage features. External stakeholders from the onset also included developers, Homes for Scotland, land factors, and Scottish Environment Protection Agency (SEPA).

Of these 15 sites, 5 were agreed for removal from further assessment due to being inappropriate for SW to vest, as 1 site had no defined SUDs and the remaining 4 sites accepted roads drainage only. The remaining 10 sites were progressed to full technical assessment involving site and desk-based activities comparing original approved drawings, hydraulic calculations and constructed SUDS installations to the relevant standards at the time of approval. This involved the development and use of new, risk-based assessment procedures. Where these assessments revealed problematic SUDS due to either poor construction and/ or poor maintenance regimes, appropriate mitigation actions with estimated costs were identified to the aim of remediating the SUDs to the minimum relevant vestable standards at the time of construction. These actions would be completed and funded by the current owners to enable public vesting. As part of this, SW also estimated 'whole life' maintenance costs for each remaining SUDS site under public stewardship.

Results and Discussion

To date, the focus has been on 3 sites prioritized due to their varying ownership models and relatively straightforward issues. Of these, one developer has agreed to complete the required remedials at their site with public vesting expected for early 2015. At the time of writing, negotiations are ongoing with the owner of the second site with the expected outcome that public vesting will complete in 2015. For the third site, protracted legal negotiations with the current owner have effectively stalled the vesting process. This is a key point to note as the ability to complete the vesting process falls outwith the control of either public body. This interim result will help guide future decisions whether to progress SUDS vesting for similar sites involving land management companies. Progression of the outstanding SUDS sites is likely to follow subject to the experiences gained and lessons learnt from focussing on vesting SUDS at the above 3 sites.

This ongoing 'pilot' project has highlighted many successful outcomes and challenges. These include the likely public vesting of at least 2 SUDS sites in 2015 and several key lessons learnt. These lessons include the need for close liaison and early dialogue with relevant and willing stakeholders, the identification of legal complexities, delays due to uncooperative SUDS owners, the availability and application of sufficiently experienced staff resource to the vesting process, dealing with court appointed administrators of insolvent developers delaying identification of land ownership for transfer, as well as the sub-standard construction and historic poor maintenance at the majority of legacy SUDS sites. More generally, this pilot project has increased experience in and heightened awareness of legacy SUDS issues including the need for better management of urban waste water runoff.

Conclusions

The experiences of this pilot study are helping SW to inform and shape new and clearer strategies, policies and processes on this complex topic of risk-based and cost-effective vesting of legacy SUDS across Scotland. This will ensure that vested SUDS features will perform as intended, helping to minimise flooding from surface waste water runoff and associated environmental impacts, as well as promoting the amenity and environmental value to help make Scotland a better place to live.

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