Materials
* Primary core (support) rock: well graded, hard, erosion resistant rock, minimum size as specified in the approved plan, but not less than 200mm.
* Filter medium: 15 to 25mm clean aggregate.

Installation
1. Refer to approved plans for location and dimensional details. If there are questions or problems with the location, dimensions or method of installation contact the engineer or responsible on-site officer for assistance.
2. Ensure that the installation of the sediment trap will not cause undesirable safety or flooding issues.
3. Using minimum 200mm rock, construct an embankment around the stormwater drain, minimum height 300mm with a minimum top width of 300mm. Internal batter slopes shall be no steeper than 3:1(H:V) and the toe of the batter no closer than 300mm from the edge of the stormwater inlet. The outer batter shall be no steeper than 2:1(H:V).
4. The top of the rock embankment should operate as a spillway to control the maximum pond height. Ensure the maximum pond height will not cause a safety hazard, including undesirable flooding of an adjacent property or roadway.
5. Place a minimum 300mm thick layer of filter aggregate over the outer slope of the rock embankment.
6. Where necessary, establish a flow control bund(s) to appropriately manage the settling pond depth and movement of bypass flows.
7. Take all necessary measure to minimise the safety risk caused by the structure and to prevent unsafe entry into the stormwater inlet.

Maintenance
1. Inspect the sediment trap after each runoff-producing rainfall event and make repairs as needed to the sediment trap and associated flow control bunds.
2. Remove collected sediment and dispose of in a suitable manner that will not cause an erosion or pollution hazard.
3. If flow through the sediment trap is reduced to an unacceptable level, the aggregate filter should be replaced. If a greater degree of water treatment (filtration) is required, geotextile filter fabric may be placed over the aggregate.
4. Remove sediment and restore original sediment storage volume when collected sediment exceeds one-third of the specified storage volume.
5. Sediment deposits should be removed immediately from any area where it is likely to cause a safety risk.

Removal
1. When the up-slope drainage area has been stabilised, remove all materials included deposited sediment and dispose of in a suitable manner that will not cause an erosion or pollution hazard.  
2. Bring the disturbed area to a proper grade, then smooth, compact and stabilise and/or revegetate as required.