Project Scope 

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Constructex fully refurbished a timber jetty which was in a state of disrepair. We carried out a detailed assessment, designed repair works for an additional 10-year lifespan and carried out the repair works.

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The jetty comprised timber pile bents, a Bailey Bridge, Bailey linkspan and Steel Pontoon. The timber piles were suffering from loss of section from a combination of marine borer and physical erosion due to the strong currents.

 

Technical Approach

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The extent of timber section loss was obvious in some locations but less clear in others, particularly where internal section rot was present. Marine borer are known to penetrate deep within voids and shakes leading to significant section loss with severe consequences for structural capacity. It was therefore necessary to determine where and to what extent section loss had occurred prior developing the remedial scheme. The Digital microProbe developed by Sibtec Scientific was used to obtain a detailed dendrochronology. This permitted Constructex to accurately account for the section properties and target the maintenance spend efficiently; ultimately making the project economically viable.

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Environmental 

 

The jetty is located in the Medway Estuary within a Marine Conservation Zone (MCZ) and Special Area of Conservation (SAC complex feature - estuary). Constructex completed an application for a marine license which was granted by the MMO. All timber was procured through a sustainable supply chain in compliance with EUTR and FSC.

 

The Works 

 

The works included: repairs to existing timbers both above and below water; confined space inspection and painting; underwater steel pontoon repairs and fitting of anodes; intertidal concrete pours; above water structural steel repairs.

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Existing structural timber members where replaced and/or braced with new members. This involved the use of hydraulic tools for drilling and underwater timber cutting supported by in house diving teams. Galvanised steel fixings and Ekki timbers were used throughout.

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Timber bases were excavated below mudline. Reinforcing mesh was fitted around degraded bases and concrete encasement pours carried out.

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Above water corroded steel members had sections replaced. These were installed using coded welders. Below water steel patch plating repairs to structural members was carried out by underwater wet welding.

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