Tensar structural solution for flood protection

Tensar Technology solution, comprising a reinforced soil retaining wall and reinforced embankment, adopted to meet the Environment Agency 1 in 100 year flood prevention standard.

Dawlish Sands Holiday Park is a highly popular static caravan park by the estuary at the mouth of Devon's River Exe, bordered along one perimeter by the Shutterton Brook.

The brook becomes tide-locked in certain tidal conditions, causing water levels to rise and threatening to flood the holiday park.

A cost-effective solution based on Tensar Technology comprising a reinforced soil retaining wall and reinforced embankment was adopted to provide upgraded defences to meet the Environment Agency 1 in 100 year flood prevention standard.

The brook runs along 700 metres of the perimeter of the holiday park and the existing embankment was not high enough to meet the 1 in 100 year standard.

The problem was to upgrade the flood protection urgently without compromising the existing level of protection or using very expensive and time consuming temporary construction measures.

Other factors considered were the aesthetic appearance, and the need to minimise land take to avoid reducing the number of caravan plots.

The solution adopted was the construction of two reinforced soil embankments to act as earth bunds on either bank of the brook, using Tensar RE geogrids layered with local fill.

These embankments were constructed with face angles of between 45 and 65 degrees, and the Tensar reinforced soil wraparound embankment system incorporated turf liners to ensure rapid vegetation growth.

This simple and versatile construction method enabled only small, 20m sections of the existing defences to be opened up at any one time, and completed by nightfall or easily sandbagged to maintain protection.

The work was completed in 18 weeks during the park's close season, avoiding risk to the public.

On the caravan park side of the embankment, a BBA Roads and Bridges certificated Tensar Wall System (TWS) was adopted.

The reinforced soil wall was faced by pre-cast masonry blocks, in an attractive russet red colour with a flint colour band and a coping layer.

The Tensar TW3 masonry blocks were hand placed and dry laid.

The system was flexible enough to be installed in an S shape to mirror the shape of the brook, thus maximising the space available, and maintaining the natural bed of the brook.

Tensar's retaining Wall System has British Board of Agrement (BBA) certification and consists of modular pre-cast concrete facing blocks and geogrid, which reinforce the granular fill behind.

The geogrids are connected to the block wall by a unique high-strength polymer 'key'.

The TW3 blocks require a two man lift with appropriate lifting handles.

Client: Teignbridge District Council Specifier: Teignbridge Engineering Services Contractor: Southwest Highways.

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