|
|
|
|
|
|
|
dealing with blockage reports and mobilizing resources to deal with them within target response times. |
|
|
|
|
|
|
|
|
4. In order to develop and maintain cost-effective planned maintenance programmes, appropriate methods should be maintained of all sewer cleaning work. Records of sediment depths from sewer, manhole and storm sewage overflow inspections should also be kept and used for this purpose. |
|
|
|
|
|
|
|
|
5. In cases where there are persistent problems, the sewerage manager will also need to assess whether it is cost-effective for him/her to continue to clean a defective sewer, or whether to invest in improvements. In arriving at this decision, the sewerage manager will have to balance economics against the levels of service failure. |
|
|
|
|
|
|
|
|
It is recommended that surveys are carried out to determine the effectiveness of sewer cleaning work. However, such surveys need not include full recording of defects. |
|
|
|
|
|
|
|
|
The term 'sediment' covers a wide variety of materials from fine solids, carried initially in suspension at some stage may settle in the sewer invert, to the large 'obstacles', which are either stationary or roll along the sewer invert. Debris is an additional associated problem. This may include bricks, rubble, rags and other sanitary refuse. Sediment can find its way into the sewer system in a number of different ways: through toilets, kitchen connections, inadequate pipe joints, manholes and inspection chambers. Construction sites can prove particularly troublesome sources of debris. Sediments will generally be cleared by jetting, but occasionally rodding, winching or hand excavation may be necessary. |
|
|
|
|
|
|
|
|
Any sewer, particularly where there are defects such as open joints or fractures, may be affected by tree roots attracted by the source of moisture. Roots may be classified as fine, mass or tap |
|
|
|
|
|