During a routine inspection Northumbrian Water Operations found that a landslip had seriously damaged part of the surface water network on the southern edge of Peterlee, County Durham. As a result the surface water sewer outfall that discharges to Blunts Beck, a tributary of the Castle Eden Dene, was found to be at imminent risk of failure.
As the area remains unstable it will not be possible to repair the existing pipe, and a new surface water sewer will need to be constructed. This work will have to take place within the Castle Eden Dene Special Area of Conservation (SAC), which is where the original surface water sewer is located. As a result BSG Ecology was contracted by Northumbrian Water to complete a Habitats Regulations Assessment (HRA) to determine whether the proposed work will have an adverse effect on the integrity of the SAC.
BSG Ecology’s Role in the Project
We provided advice on potential ecological impacts during a comprehensive options appraisal undertaken by Northumbrian Water. The appraisal was to select a viable option whilst ensuring that the integrity of the SAC will not be affected by the proposed work. The preferred option will involve the construction of a new pipeline and an outfall into the Blunts Beck, around 360m away.
We worked with the design team to develop all necessary measures to mitigate impacts on the SAC. This presented a significant challenge as the scale of the proposed works requires the creation of access tracks, compounds and working areas that are surfaced to carry the heavy plant that is required. There is also a need for soil storage within the site, both from the site preparation and from the tunnelling. This will require the clearance of a significant area of regenerating ash woodland, the removal of top soil and the importation of locally sourced stone to surface the working area.
Consultation by BSG Ecology with Natural England resulted in agreement that the works will not affect any of the yew woodland for which the SAC is designated (despite their extent). The options appraisal process has ensured that the works will take place in areas that are considered to be part of the wider site fabric – in other words, the affected habitat is not an SAC interest feature but has a supporting role for the maintenance of the site’s integrity.
By using Natural England’s Discretionary Advice Service, it was possible to engage positively with them ahead of a formal consultation being made by Northumbrian Water. This enabled the HRA to be signed off promptly by Natural England, which will allow the work to commence without unnecessary delay. Working with Natural England revealed that the proposed tree clearance will contribute to Natural England’s longer-term management objective to create an open mosaic of meadow and scattered trees. Consequently the site clearance and its subsequent restoration is designed to ensure that a mixture of trees and shrubs is retained.
Targeted survey complemented by consultation with Northumbrian Water and Natural England meant that a preferred option was identified that was acceptable to all concerned. The prompt resolution of all the key ecological issues meant that Northumbrian Water could obtain board approval for the funding of the project, in time for a proposed start date in September 2016. The scale and nature of the proposed work means that completion is expected in spring 2017.