Gully Filter Bags - Catchments and Creeks

1 Catchments & Creeks Pty LtdVersion 2 - April 2010 Page 1 Gully Filter bags SEDIMENT CONTROL TECHNIQUEType 1 SystemSheet FlowSandy Soils Type 2 SystemConcentrated Flow Clayey Soils Type 3 SystemSupplementary Trap Dispersive SoilsSymbolPhoto 1 Temporary Gully bagPhoto 2 Permanent Gully bagKey Principles1. Sediment trapping primarily occurs through the filtration of the water passing through thegully The critical design parameters are the flow capacity and pore size of the Filter The Gully bag must not be allowed to block the passage of flow into the drainage Gully evenwhen the bag is full of Can be used on field (drop) inlets as well as sag and on-grade roadside kerb InformationRefer to manufacturer s specifications and design Gully bag must be installed such that no sediment-laden inflow is allowed to bypass the baguntil the bag is either full of sediment, or the inflow exceeds the hydraulic capacity of the practicable, the Gully bag should be capable of allowing 100% bypass of the designinflow once the bag is fully blocked with sediment.

2 In such cases the side entry inlet slot (if any)may be fully blocked with a suitable sediment filtration barrier (Photo 1).If the Gully bag does not have the capacity to allow 100% bypass of the design inflow once thebag is fully blocked with sediment, then the side entry inlet slot (if any) must be protected inaccordance with the guidelines provided for sag inlets (refer to separate fact sheet). Catchments & Creeks Pty LtdVersion 2 - April 2010 Page 2 Figure 1 Typical installation of temporary Gully Filter bagDescriptionA Gully Filter bag (Photo 1) is a removable,high strength, Filter bag installed beneaththe grate of a roadside kerb inlet or field(drop) alternative to the temporary Gully bag isthe use of a permanent Filter bag/cage(Photo 2) that can be used for sedimentcontrol during both the civil construction,building and operational to trap sediment at roadside kerbinlets and field (drop)

3 Technique is a Type-3 sediment trapprimarily focused on the collecting of most circumstances these traps shouldbe supplementary to a more substantialdownstream sediment limited control of fine sediment to assist in limiting sediment build-up instormwater drains, thus reducing the cost offinal off-maintenance systems can be retained as part ofthe permanent stormwater likely to be damaged by road trafficcompared to aboveground kerb inletsediment require cleaning on a regular machinery is required to remove thegully bag once full of ProblemsThe Gully filer bags are often removedbefore the site goes off-maintenance.

4 Flooding problems may occur during heavyrainfall events if the side entry slot isblocked, thus reducing the overall inletcapacity of the be used on field (drop) inlets as well as sag and on-grade roadside kerb RequirementsConsideration must always be given topotential bypass flows in the event ofsevere sediment trap must be capable ofallowing 100% bypass of the design inflowonce the bag is fully blocked with sediment. Catchments & Creeks Pty LtdVersion 2 - April 2010 Page 3 Site InspectionCheck the installation for safety for excessive that all stormwater is allowed to passthrough the Gully to see if additional sediment trapsare required up-slope and/or down-slope ofthe stormwater Refer to approved plans for locationand installation details.

5 If there arequestions or problems with the location,dimensions, or method of installation ,contact the engineer or responsible on-site officer for Ensure that the installation of thesediment trap will not causeundesirable safety or flooding Install sediment trap in accordance withmanufacturer s Ensure that no sediment-laden inflow isallowed to bypass the Gully bag until thebag is either full of sediment, or theinflow exceeds the hydraulic capacity ofthe Install appropriate sediment and/or flowcontrols on the side-entry slot (if any).6. Take all necessary measure tominimise the safety risk caused by Inspect all sediment traps daily andimmediately after runoff-producingrainfall.

6 Make repairs as Remove and replace the Gully bagwhen it is either full of sediment, or islikely to be full of sediment before thenext inspection, or the hydrauliccapacity of the Filter bag is Dispose of the sediment and Filter bagin a suitable manner that will not causean erosion or pollution Ensure sediment does not enter thestormwater drain during de-siltingoperations and maintenance of the Sediment on the road must be removedimmediately if it represents a When the up-slope drainage area hasbeen stabilised, remove all materialsincluded deposited sediment anddispose of in a suitable manner that willnot cause an erosion or pollutionhazard.