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Our experience in river restoration design and construction for the Environment Agency. Céline Gallay Senior Engineer Halcrow Group Ltd [email protected]. Introduction. I will discuss the following topics: Understanding the design and information on how to restore - PowerPoint PPT Presentation
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13/07/20091 River restoration design and construction - Celine Gallay
Our experience in river restoration design and construction for the Environment Agency Céline Gallay
Senior Engineer
Halcrow Group Ltd
2 River restoration design and construction - Celine Gallay13/07/2009
Introduction
I will discuss the following topics:
• Understanding the design and information on how to restore
• Landowner engagement, constraints and buy-in into the design
• Our experience of framework contractors in river restoration
• The need for flexibility in the design and adequate supervision
• How to program the works for the low flow period
3 River restoration design and construction - Celine Gallay13/07/2009
Understanding the design and information on how to restore• Simple design with two categories: structures and in-river
restoration works
• Structures: balance design life, Eurocode standards / structures similar to historical structures
• Conflict between different protected species in different channels: the client must prioritise species at an early stage
• RRC manuals: good source of information on restoration techniques
• More information on ideal flow conditions to provide good habitats for different species would be useful
4 River restoration design and construction - Celine Gallay13/07/2009
Landowner engagement, constraints and buy-in into the design
• Consultation of landowner is required at the earliest opportunity ideally with outline design
• Good to have a showcase project. E.g. Barton Court on Kennet
• Convincing the landowner that fish will not be lost due to removal of weed rack
• Strategic River Avon Restoration : removal of weirs/hydroelectric schemes
5 River restoration design and construction - Celine Gallay13/07/2009
Our experience of framework contractors in river restoration
• Works have been delivered through the NCF or the Minor Works Framework
• Competent framework Contractors to build structures but some lack experience in river restoration techniques
• Wylye: river restoration works were carried out by a fencing sub-contractor
• Avington: stone riffle rolled to a flat finish
• Lessons learnt: during tender process, a client should request CVs of key construction staff for the works, which demonstrate past experience in river restoration
6 River restoration design and construction - Celine Gallay13/07/2009
The need for flexibility in the design and adequate supervision
• Flexible design to accommodate protected species. E.g. water voles at Avington
• Not an exact science – design needs to be adapted on site
• Importance of Environmental Clerk of Works on site and a site supervisor (part-time basis)
7 River restoration design and construction - Celine Gallay13/07/2009
How to program the works for the low flow period
• Best period from mid-July to mid-October during the low flow season
• Budget allocated for the whole project in the same financial year (April to March) resulting in a great challenge to have works on site before September.
• Programme of works was developed with the Environment Agency SW Blandford office:
• Reaches of the River Avon and its tributaries in need of River Restoration were identified and prioritised, with a costed action plan taking into account the likely landowner collaboration,
• A PAR was prepared for a 5 year programme of works allowing design during a financial year and construction during the summer of next financial year,
• This approach also allows the packaging of projects and hence cost savings.
8 River restoration design and construction - Celine Gallay13/07/2009
Example of strategic River Restoration Project (River Avon)
5-year programme
2011-12 2012-13 2013-14 2014-15 2015-16
Package yr 1 yr 2 yr 3 yr 4 yr 5
1(a) - iStructural work - simple (designs ongoing) Construct
1(a) - ii Structural work - simple Appraise & design Construct
1(b) Structural work - complex Negotiate & appraise Design Construct
2(a) - i In-channel & riparian work - simple Construct
2(b) - iIn-channel & riparian work - complex Negotiate & appraise Design Construct
3 (a) - iiCollaborative - simple 'quick win' partnerships Construct
3 (b) - iiComplex collaborative - complex partnerships
Negotiate/build partnerships & appraise Design Construct
Logical sequence of programme
9 River restoration design and construction - Celine Gallay13/07/2009
Conclusion
• Additional information on ideal flow conditions for protected species would be useful
• Early landowner engagement is essential
• Selected EA framework contractor for tenders should demonstrate past experience in river restoration
• Flexible design and adequate site supervision are required
• A more strategic catchment base approach to river restoration should be considered to provide better value for money