Materials * Rock: 150 to 300mm equivalent diameter, hard, erosion resistant rock. * Sandbags: geotextile bags (woven synthetic, or non-woven biodegradable) filled with clean coarse sand, clean aggregate, or compost. Installation (Rock Check Dam) 1. Refer to approved plans for location and installation details. If there are questions or problems with the location or method of installation contact the engineer or responsible on-site officer for assistance. 2. Prior to placement of the sediment trap, ensure the drainage channel is deep enough to prevent water being unsafely diverted out of the drain once the check dams are installed. 3. Locate each check dam sediment trap as directed within the approved plans, or otherwise at such a spacing to achieve the required sediment trapping outcomes. 4. If the check dams are also being used to control erosion within the drainage channel, then locate each successive check dam such that the crest of the immediate downstream dam is level with the channel invert at the immediate upstream check dam. 5. Construct each check dam to the dimensions and profile shown within the approved plan. 6. Where specified, the check dams must be constructed on a sheet of geotextile fabric used as a downstream splash pad. 7. Each check dam must be extended up the channel bank (where practicable) to an elevation at least 150mm above the crest level of the dam. Installation (Compost-filled socks) 1. Refer to approved plans for location and installation details. If there are questions or problems with the location or method of installation contact the engineer or responsible on-site officer for assistance. 2. Prior to placement of the sediment trap, ensure the drainage channel is deep enough to prevent water being unsafely diverted out of the drain once the check dams are installed. 3. Locate each sock as directed within the approved plans, or otherwise at such a spacing to achieve the required sediment trapping outcomes. 4. Place each sock to the lines and profile shown in the approved plan or as directed by the site supervisor. 5. Ensure each sock extends up the channel banks (where practical) to a level at least 100mm above the crest level of the check dam. Maintenance 1. Inspect each check dam and the drainage channel at least weekly and after runoff-producing rainfall. 2. Correct all damage immediately. If significant erosion occurs between any of the check dams, then check the spacing of the dams and where necessary install intermediate check dams or a suitable channel liner. 3. Check for displacement of the check dams. 4. Check for soil scour around the ends of each check dam. If such erosion is occurring, consider extending the width of the check dam to avoid such problems. 5. If severe soil erosion occurs either under or around the check dams, then seek expert advice on an alternative treatment measure. 6. De-silt sediment trap if the sediment level exceeds 1/3 the crest height. 7. Dispose of collected sediment in a suitable manner that will not cause an erosion or pollution hazard. Removal 1. When construction work within the drainage area above the check dams has been completed and disturbed areas sufficiently stabilised to restrain erosion, the dams must be removed, unless the sediment traps are to remain as a permanent feature. 2. Remove collected sediment and dispose of in a suitable manner that will not cause an erosion or pollution hazard. 3. Remove and appropriately dispose of all materials including any geotextile fabric. 4. Stabilise the disturbed channel with a lining of fabric and rock, or establish vegetation as appropriate.