Design and construction observation of retaining works along the Avon River, Wood Lane, Christchurch

 

Description: Earthquake repair work was required to stabilise the riverbank along the edge of a residential property bounding the Avon River. e2Environmental carried out the design and construction observation of the riverbank retaining works.

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Our expertise: e2Environmental designed stone riprap protection and a 1.2m reinforced earth block-faced wall to replace an existing gravity brick wall that had failed in the February 2011 earthquake. An engineering report was prepared for the resource consent application.

Much of the construction work had to be carried out underwater as it was cost-prohibitive to try and divert the river flows away from the site (for example with sheet piling). The retaining wall was designed using single graded crushed aggregate (ballast) as fill below water level, as this material is free draining and does not require compaction.

 

Outcome: Construction has been completed. The sediment control methodology designed by e2Environmental and employed during construction was an innovative use of existing materials. The geotextile screen proved very effective at retaining sediment inside the working area, with favourable comments from the Council’s monitoring staff indicating it performed better than their normal practice.