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Tomo Remediation, Lynn Reserve, Glenfield

A large tomo began appearing in the recreational park at Lynn Reserve. After initial investigations, the source of the tomo occurred due to catastrophic collapse of the existing 1050dia steel culvert. The remedial strategy was deemed as Emergency Works, and involved relining the existing 1050dia culvert using a HDD method to pull through 800dia SRD11 PE pipe across the 200m of culvert. This method was used in replacement of standard PVC liners, as these methods typically use man-entry. Man-Entry into the failed 1050dia culvert was not accepted by the Client, therefore Kerry Drainage & Civil developed a non-man-entry method by pulling in PE pipe for the relining system.

Works also included installing a new future-proofed 1280dia GRP pipe, using micro tunnelling and pipe jacking methods. A challenge encountered during the relining and miscounselling activies, was drilling through tomo and slip material; a high level of detailed planning and work methods were development to ensure the success of these activities.

A 12m deep temporary shaft was constructed as a key work location to undertake the relining and pipe jacking works. The shaft was constructed to a high quality standard and was utilised throughout the 12months of project work.

The existing headwalls were upgraded in-situ, along with the addition of a large bespoke fish ladder. The unique fish ladder captured the attention of many ecologists and encourages native fauna to access fresh water upstream habitats for spawning. 


Completed: September 2020


Client: Auckland Council


Type: Stormwater Upgrade, Emergency Works, Microtunnelling

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