Rushey Weir Richard Harding BEng (Hons) CEng Project Executive Thames Weirs projects 1 Rushey Weir: Background to the Thames weirs The Environment Agency owns, operates and maintains 195 weir sets across 45 weir and lock complexes on the River Thames bringing multi-functional benefits including waterways, water abstraction, recreation, conservation, biodiversity and flood defence. The majority of our powers and duties are contained in the Water Resources Act 1991; Environment Act 1995 and the Thames Conservancy Acts (as successors in title to the Thames Conservancy). In particular, the Environment Agency has a duty to repair and maintain weirs and locks and the public has a right to pass and repass in vessels on the River Thames. (TCA 1932) River levels are maintained in accordance with the green book but this is us exercising a power, not a duty although over the years users could claim a legitimate expectation this has not been tested in law and weirs are predominately replaced to existing level. Most weir projects are undertaken as permitted development under the General Permitted Development Order 1995. This doesn t negate the need for wide consultation. 2 1
Rushey Weir: Background We regularly inspect our weirs and undertake repair/replacement work. Historically assets have been designed with a design life of 60 to 100 years so on average we would expect to replace 3 weir sets a year at c 7m per annum. In reality we have spent much less than this on a needs driven programme and have an aging asset base. The Thames Weirs Strategy 2003 remains unapproved as a funding split between beneficiaries could not be agreed. As such weirs are still justified on a standalone basis and funded via FCRM (levy and fdgia). Further review requested, overtaken by possible mutualisation to the Canal and River Trust and now ongoing as the Future of Navigation project. 3 Rushey Weir: Project background 1 The July 2007 flooding highlighted operational issues with the 9 remaining paddle and rymer weirs (P&R) on the River Thames. P&R weirs are a throw back to the old flash weirs and involve manually inserting and removing large paddles (up to 3 deep) between vertical posts (rymers). A review concluded we were regularly asking our staff to lift weights (both static and life) 3 times above the recommended limits within the Manual Handling Regulations 1992. A project to replace all 9 P&R weir s was initiated. 4 2
Rushey Weir: History Rushey Weir is located in rural Oxfordshire and was originally constructed in 1790 and reconstructed in 1887. It consisted of steel frames either side of a concrete bull nose. The north section was 14.7m wide (24no 3 deep paddles) and the southern section was 6.25m wide (10no 3 deep paddles). The northern section was reconstructed again in 1932 but the southern section and bull nose were unchanged making it the oldest weir on the River Thames. There are 2 Scheduled Ancient Monuments (SAM s) on the right bank. Prior to listing the preferred option was to replace with 5 dipping radial gates 5 Rushey Weir: Ergonomic assessments Key legislation includes Health and Safety at Work Act 1974 and HSE Manual Handling Regulations 1992. We undertook 3 ergonomic assessments: Williams Report Manual Handling Assessment of P&R Weirs Mar 2009. Focused on dead loads noting the maximum paddle weight at Rushey was 25kg (102 paddles and 35 rymers) taking up to a full day to pull. This is 3 time the recommended limits. Human Applications Ergonomic Assessment of lightweight paddles and rymers at Goring Weir March 2010. Human Applications Ergonomics Report of Pull Out Forces for Streatley, Northmoor and Rushey Weirs April 2010. This focused on life loads with the deeper paddles again 3 times recommended limits. EA staff at risk of serious muscular skeletal injury. Above reports challenged by local community re Northmoor Weir and English Heritage. HSE reviewed the reports in Jan 2011 concluding our approach was reasonable and the steps to manage the risk was with us as the operator. The Department of Work and Pensions involved following intervention by local MP. They concluded we were managing risk so far as reasonably practicable. National Audit Office also reviewed whether due process had been followed following request by local MP. 6 3
Rushey Weir: Heritage issues In it s wider duties we requested an independent heritage review of all 9 P&R weirs. This concluded (Truman Oct 2010 Building on initial review in 2002) that 4 weirs were of higher value (Rushey, Goring, Streatley and Iffley) and suitable for listing. Third party made listing application to English Heritage in Mar 2009. We asked them to review all 9 weirs and they gave grade II listed status to 3 weirs (Rushey, Goring and Streatley) in Oct 2009. This was based on the historical operation methodology. Certificate of Immunity requested for other 6 P&R s allowing us to proceed with works. Listing extended options appraisal and meant we needed Listed Building Consent from the local authority. English Heritage became a statutory consultee. 7 Rushey Weir: Wider options Normal options would involve reviewing weir types. EA preference (assuming weir) is fixed, radial, buck in that order. Options considered included: Gantries allowing lifting of P&R s Hinged system using winches New weir upstream or downstream retaining P&R weir Bypass channel incorporating new weir Mobile or fixed cranes Lightweight materials Gated weirs All options except gated weirs significantly increased costs, were unproven, unsightly or introduced new risk. 8 4
Rushey Weir: Shortlisted options Fully gated weir v partially gated weir (note fixed crest equivalent was 400m) English Heritage accepted main operation via gated weir provided partial retention of P&R and bullnose Reviewed no of gates on wider north section. Modelling showed 4 gates would increased flood risk downstream in low order flood events. Agreed solution was 3 dipping radial gates with single depth of P&R on raised on south side. Construction costs only estimated at 2.8m. 9 Rushey Weir: Preferred option (weir) 10 5
Rushey Weir: Preferred option (fish pass) 11 Rushey Weir: Access issues Our access to Rushey lock is on the opposite river bank and was unsuitable. How we do the work is becoming a major issue and access to Rushey Weir was no exception. Access routes on private land and compounds not adjacent to operational land are likely to need planning permission. On average we estimated 10 additional car and 2 HGV movements a day on road that carries 2000 vehicles 12 6
Rushey Weir: Consultation Consultation never stops! Communication plan is vital NEAS screen projects at the start and medium and high risk will follow process: Scoping Report EIA Land Drainage Regs advertising Environmental Report/Statement Internal consultees including waterways, fisheries, biodiversity, landscape, fisheries, PSO, FCRM Statutory consultees are Natural England and English Heritage. External consultees include local landowners and residents, local authorities, parish councils, angling clubs, British Canoe Union. 13 Rushey Weir: Key design issues Geomorphology. Major downstream gravels and new weir will change the flow regime. Fish pass type/location. We started as technical but have constructed a naturalised fish pass. Cofferdam details gated or removable v risk; levels (upstream and downstream) Flood protocols what do we do in a high flow event? Hydropower design tweaks in to construction phase to facilitate this at a later date. Archaeology full excavation required in advance of fish pass. 14 7
Rushey Weir: Key construction issues 2 key issues at Rushey: Weather. We started in drought and it s rained ever since resulting in flooding to cofferdam in year 1 and the access road on several occasions. Condition of existing weir was far worse than we expected extensive seepage and concerns over stability of bullnose.. 15 Rushey Weir: Oct 2013 (almost there). 16 8