Spring 2013 – Aylestone Overflow Weir Plans

Delivery of the Aylestone Park Project on this site now moved to one that is contract led to ensure that what was now required at this key weir location could be delivered.

Firstly, the background to the scheme … this is one of two versions of the H&G model overflow weir design. The weir is based on a similar principle to one recently constructed at Over, the Aylestone version being the alternative design with full depth draw-off under the towpath to considerably increase hydraulic efficiency and permit boats to moor across the structure thus maximising use of the site at what will be a popular visitor mooring. This design ensures there is no potential for the structure to fail to perform the crucial function for surface water discharge purposes at all times.

The face fronting the Canal goes to below water level to minimise floating debris passing under the towpath and getting caught on the weir. This will ease and add to the safety of future maintenance, as well as ensuring blockages and debris are prevented so as to maintain consistent hydraulic performance. The adjustable weir plate gives the ability to adjust the height of the weir and to have different sections at different heights to control the water level more efficiently. A section of angle on top of the concrete weir acts as the weir crest. This not only enhances the hydraulic efficiency but also ensures that there is no wide crest to the weir, which can be tempting for children to ‘dare’ to run along! One section is provided with deeper ‘stop planks’ to permit partial draining of the Canal so as to facilitate easy adjustment of the adjoining weir plates. The final towpath over the structure will be surfaced to match the other paths at Aylestone.

A key action to progress the project at the end of last year was a re-appraisal of the original design concept. This essentially remained unaltered but with a change in construction method and, most crucially, the working up of detailed designs. It was no small task to deliver this on a reasonably tight deadline, including the necessary structural calculations and detailed construction drawings, so that the work could proceed as soon as the appalling weather conditions permitted. We are very pleased to welcome to our team volunteer Thomas Ashworth of Tony Gee & Partners, a world respected firm of Structural Engineers in Gloucestershire, and this presented the ideal first project. We greatly appreciate the support of Tony Gee & Partners in both this and a number of other projects – thank you.

Having produced full construction drawings we now needed to be able to ensure, once we actually started construction, that it would be completed relatively quickly. Chambers Builders of Gloucester had already been involved undertaking work at The Wharf House after the internal burst pipe last September (having first been recommended by our contacts at Gloucester Quays and Keyway) and undertake works of all scales in a diverse range of industries. It actually turned out that the owner of the Company was a customer of The Wharf House and an ongoing partnership has rapidly evolved – they were obvious candidates to approach in respect of the work at Aylestone Park.  Add in the offer to undertake the work at highly preferential rates and all the H&G CT boxes were ticked!

Chambers was therefore the Principal Contractor appointed to deliver the reinforced concrete element of the project.  The weir will act as a crucial structure in the long term surface water management of both Hereford City and the Hereford pound of the H&G Canal.

By early spring, 2013, we will have submitted the joint planning application with Hereford United Community Trust for the levelling of the lower part of the Park and the construction of the new sports and recreation facilities.  The considerable reed bed and overflow channel that the weir will discharge into will form another phase later this year.  This will include the selective widening of the Canal at Aylestone Park to meet modern requirements – more in Edition 116 of The Wharfinger.