Case Study - Keystone - Shutterton Brook Flood Defence

Project Description:

Local authority engineers trimmed hundreds of thousands of pounds off a new flood prevention scheme by using Forticrete's innovative Keystone dry-build retaining wall system.

Campers at three sites bordering tidal Shutterton Brook near Dawlish in Devon can sleep easier thanks to the £1 million scheme, which was completed in a tight timeframe between holiday seasons.The new defences also provide protection for a housing development further upstream.

The project, carried out for Teignbridge District Council by main contractor SW Highways, involved the construction of a two metre high reinforced Keystone retaining wall following the path of the river.

Keystone Classic splitfaced units, dry-built and using the unique Keystone high-strength glassfibre pin fixing system, were specified to provide a natural "stone built" appearance with built-in strength.

The council's engineering department selected Russet colour for the 400 metre long structure, with a string course in flint to provide contrast. Standard Keystone cappings , also in Russet, were used to completed the structure.

Positioning the locking pins in a combination of different positions allowed the contractors to curve the wall to follow the line of the brook and further strength was provided by combining the Keystone wall with proprietary geogrids, which were "locked" into the structure along the riverbank.

The council's engineers devised the scheme after alternatives had been ruled out on the grounds of cost. Wide earth mounds had been considered but these would have taken up valuable land and called for the replacement on internal roads at the campsites.The erection of a cast in situ concrete bank was also ruled out on grounds of time and cost.

Explains John Cocker, Teignbridge Engineering Services Manager: "By using Keystone we were able to keep to a tight schedule and to save hundreds of thousands of pounds on our original estimates. It also produced an aesthetically pleasing finish and helped to speed up construction."

The work has resulted in a reduction to a 1 in 100 years flooding probability for the area and has allowed the council to dispense with other artificial flood prevention measures.

Description: Keystone Compac Splitface Russet with Flint colour String Course & Cappings

Description: Keystone Compac - Shutterton Brook, Devon

Description: Keystone wall following line of river