Collaton Cross, South Devon

PROJECTS

Collaton Cross, South Devon

Project: Collaton Cross
Location: South Devon
Client: Pillar Land Securities Ltd
Services: Flood Risk and Infrastructure

A group of school children are on a school science trip to a pond outdoors. Here they use nets to catch bugs

The Project

We applied our flood risk and infrastructure services to a proposed mixed-use development, consisting of 125 high-quality residential dwellings and 12 commercial units, on a site located on the boundary of an Area of Outstanding Natural Beauty (AONB).

The Problem

Our client, Pillar Land Securities Ltd, was looking to make a detailed planning application to redevelop a long-abandoned RAF station on the outskirts of Newton Ferrers in South Devon. In addition to the usual challenges of developing on a brownfield site, there were existing drains entering the site that served surrounding properties, that needed to be accommodated within the site proposals.

Due to the scale of the development, a Flood Risk Assessment with Drainage Statement was required to support the outline planning application; and ensure that the scheme would manage surface water effectively (by not increasing the risk of flooding on site, to third parties or downstream of the site’s outfall).

As this site was located on the edge of an AONB, the client was conscious of providing a visually attractive development that would integrate seamlessly into the view planes from the wider escarpment. It was also important to have a hardworking scheme that that could provide multifunctional benefits wherever possible.

Due to the nature of the site’s former brownfield use, a carefully considered Materials Management Plan (MMP) needed to be devised to handle any potential contaminates or reworked ground within the existing strata. Vehicle movements off site to expensive waste handling facilities would also need to be minimised.

Additionally, the site had challenging levels which needed careful consideration to ensure that future residents were provided with desirable gardens. The Highway Authority’s specific requirements of minimum and maximum site grades for the proposed public highways also needed to be addressed.

The Conclusion

The client wanted an exceptionally high-quality development that would not only provide much needed housing and employment opportunities, but also deliver on amenity and biodiversity aspects.

With Calibro’s sound due diligence work conducted throughout the process, along with our collaborative working style with all design team members, a scheme was devised with the potential to provide a real sense of community for the eventual owners, occupiers and day trippers to this exciting South Devon development.

The Solution

An initial site appraisal of all third party information and a subsequent client meeting was considered essential to understanding the true complexities of the site. From the outset we needed to ensure that we correctly identified exactly what the client wanted to achieve, and whether they had any specific preferences for how to approach some of the challenges.

After our initial due diligence appraisal, we highlighted some additional constraints relating to existing drains from offsite that the client wasn’t originally aware of. This enabled us to design in solutions early in the process (meaning the client wasn’t confronted with a significantly costly problem during the site build).

Alongside this, we assessed surface water strategies for the site, in line with the existing ground conditions (and any potential contamination from the site’s previous land uses that may have been present) to ensure the two were compatible. A number of detailed meetings with the client and their geotechnical consultants followed, to devise a strategy for the MMP. From here we also targeted additional ground investigations in the areas of concern or that would require additional investigation; giving the approving authorities confidence in the body of evidence that supported the strategies put forward.

Ultimately, for the MMP strategy, we were able to identify a significant area of a natural valley in a steep section of what would have been largely unusable Public Open Space. This area could be utilised to store and safely encapsulate all site waste/arisings: remaining on the site and avoiding significant cart-away costs. This had the benefit of creating a much more useable area of POS, that could be enjoyed by future residents. This was further enhanced by our proposals for surface water features, enabling a creative landscaping scheme and Biodiversity Net Gain compliant scheme; while adding significant amenity benefit to residents and the wider local community.

Once we had the strategy for dealing with the MMP, we could zero in on the development proposals themselves. We identified certain areas where we could drain to ground using soakaways; opportunities for conveyance swales for highway runoff; bio retention areas for amenity and water quality purposes; and even a significantly sized detention basin with permanent wet pool, which could be enjoyed by local residents as well as wildlife.

But we didn’t stop there. We even added swales and ponds downstream of the main site ‘lake’, to further mitigate and cleanse offsite flows entering the site, by re-wilding/naturalising the existing piped drainage connection.

All proposed site levels were devised in line with the MMP and drainage strategy, while also adhering to the local authority’s design guidance. This gave the client the best possible outcome in terms of construction costs, a desirable layout, and the potential for road and sewer adoptions on receipt of a positive planning decision.