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Example of Standard Operating ProcedureThe main risks when cleaning out a silt lagoon are created either by undercutting and making unstable the embankment, particularly below water or by a machine driving onto soft ground that cannot support the machines weight.

Silt lagoons can be deceptive, they form a crust which appears stable, but the silt remains soft beneath.
To manage this risk the guidance below will be followed:-

Pre Commencement Planning

A risk assessment will be carried out to identify the appropriate machinery
Inspection and monitoring
Regular inspections of the operational area will be carried out by the Quarry Manager or appointed competent person.
The inspections will be at a frequency that is appropriate for the operation, but no less than daily
The operator working the machine will constantly monitor the crest of the lagoon for sign of slumping, cracking or instability.
Upon observing any signs of instability, all work will be suspended; personnel and machinery removed and access prohibited. The operator will inform management and geotechnical advice will be sought if required.

Method

Work in accordance with the diagram above
Access onto the silt is not permitted unless capped and stabilised and authorised by the Unit Manager.
Care will be taken to only remove silt as planned and not excavate the lagoon retaining structure.
The edge of the silt pond will be clearly demarcated at all times, ideally by barriers such as a bund.
The excavator will be as far from the lagoon edge as operationally possible and will be capable of obtaining the necessary depth of dig whilst maintaining the required stand-off
The excavator’s tracks will be perpendicular to the lagoon edge such that a safe, rapid exit from the area can be made if slope instability develops.
The excavated silt will be cast as far away from the crest of the lagoon as possible so as to prevent loading of the crest which could cause failure. The placement of silt must not block the safe exit route of the machine.
When not in use all machinery will be parked in a safe location away from the waters edge.

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