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Flood Defence Glazing at Shaldon and Ringmore Tidal Defence Scheme

Experience Report

PROJECT DESCRIPTION:

The Shaldon and Ringmore Tidal Defence Scheme from above

Interserve are currently constructing the £3.8m Shaldon & Ringmore Tidal Defence Scheme on the southern side of the Teign Estuary, in South Devon. This Environment Agency scheme will protect over 250 properties from tidal flooding, up to an event with a 1 in 1000 chance of occurring each year for the next 100 years.
Flood defence glazed windows were installed in the tidal defence walls, to help minimise the visual impact of the scheme on the local community. These flood defence windows are described in detail in this Experience Report.

GLAZED FLOOD DEFENCE SYSTEM:

At the Shaldon & Ringmore Tidal Defence Scheme, eight flood defence windows were incorporated into the reinforced concrete tidal defence wall. Each window was approximately 2.5m x 0.6m in size and made from heat strengthened, extra-clear, low iron glass. Two separate window systems were used:

  •  46mm thick windows – Formed from 3 x 12mm and 1 x 10mm thick laminated glass panes, with ‘bio-clean’ self cleaning glass on the seaward face 
  • 34mm thick windows – Formed from 2 x 12mm and 1 x 10mm thick laminated glass panes, with ‘bio-clean’ self cleaning glass on the seaward face

Each window was delivered to site as a completed unit within two stainless steel posts, a base and a capping bar and support / fixing angles. The stainless steel support frames were fabricated from cold formed Grade 316 (marine grade) stainless steel. Fixings holes were formed in the steel members during production in the factory, removing the requirement to cut fixing holes into stainless steel on site.

BENEFITS OF USE AT SHALDON & RINGMORE:

Visual impact of the tidal defence walls was a sensitive issue, as they partially blocked the impressive sea views. Incorporating flood defence glazing resolved objections to the scheme raised by local residents, whilst still achieving the required wall height and protection. The flood defence glazing proved a popular solution with the local community, helping to minimise the impact of the scheme. A photograph of the glass windows installed within the Shaldon and Ringmore tidal defence walls is shown below:

Flood Defence Glazing at Shaldon and Ringmore
Building work at the Shaldon and Ringmore tidal defence scheme

CONSTRUCTION METHODOLOGY:

The flood defence windows were used in two different wall types, stoneclad and rendered reinforced concrete walls. In both cases, the exposed concrete mini-columns were cast prior to placement of the glazed panels. Each window unit was mechanically lifted and lowered into position by excavator, due to the self weight. The support angles were then resin fixed into the concrete window opening and mini-columns on each side.

Protective flexible strips were placed on the glass whilst the remaining stone cladding was completed. Similarly, protective polythene was used where the remainder of the walls required rendering.

Finally, the concrete sill was grouted into place and a timber capping detail fixed on top of each window. This provided both a safe handrail and improved the visual appearance of the window units.

DESIGN LOADINGS:

Each flood defence window was designed to a Point Load of 10kN over an area of 150mm2, in addition to the maximum hydrostatic loading that may occur due to temporary rises in sea level.

LESSONS LEARNT:

Our site team found installation of the flood defence glazing was quick and straightforward. The main problem we overcame concerned the size of the lifting eye details, where insufficient space had been allowed between the concrete mini-columns. Minor alterations were made to the columns on both sides of the windows, before they were fixed into position.

POTENTIAL FURTHER USES:

Similar flood defence glazing systems have been used successfully worldwide and there is significant scope for the Environment Agency to incorporate them into future tidal defence schemes.

Interserve has also gained experience using flood defence glazing on the Ashbourne Flood Alleviation Scheme in Derbyshire, currently being constructed for the Environment Agency. Flood windows were incorporated into existing buildings that were subject to frequent flooding of the adjacent Brook.

SUPPLIER DETAILS:

The flood defence glazing used at the Shaldon & Ringmore Tidal Defence scheme was supplied by TFS-Defence Doors. The main point of contact for this project was Neil McDermid.


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