Construction of tilting weirs at Hatfield SAC part of Humberhead Peatlands NNR

Tender description

Natural England (NE) Hatfield Moors, was exploited for peat over many centuries. During the 20th century the integrity of the bog and its unique biodiversity were severely threatened by mechanised peat extraction and associated drainage. These activities finally ended in 2004 and in 2014 a LIFE+ Project restoration (LIFE13NAT/UK/000451) project provided the opportunity to restore and extend the UK's largest area of degraded lowland raised bog providing a long-term future for the rare plants, birds and insects that have evolved to live on this unique wetland habitat. As part of the Hatfield Moor restoration project it is proposed to incrementally increase local water levels to enable re-establishment of the native peatland species and return the currently drained peat land to a natural habitat. To achieve this, various manmade water channels are to be controlled to impound water and saturate the surrounding peat land. This will be facilitated by the installation of cut-off piles and the provision of adjustable tilting weirs that will enable modification of the upstream water level. Two existing weirs located in sites 3 and 4 are to be retrofitted prior to commencement. Therefore, the scope of works is as follows; to supply and install 3 tilting weirs around Natural England's Hatfield Moors Peatland site with associated water control valves across the existing drainage ditches, this includes installation of cut-off sheet piling to support the provision of the tilting weirs and installation of hand rails. Additionally, the works will include an aspect of re-profiling earthworks. NE are the 'Client' with Mott MacDonald acting as the Principal Designer and Project Manager for NE on this project,works to be carried out by the Principal Contractor, who will be the supplier appointed. Key Objectives are to deliver the project effectively and ensure that project completion and operational use is achieved by the 30th June 2018.