Field Investigations
Field investigations conducted by Johnstown Regional Sewage on the interceptor system and by each of the municipalities/authorities operating the collection systems will be necessary to identify defects in their systems that are contributing to the sanitary sewer overflows and backups in the area. In general, a Sanitary Sewer Evaluation Study (SSES) may consist of all or some of the following parts: Flow Monitoring, Smoke Testing, Manhole and Pipe Inspections, Closed Circuit TV Inspections, and Dyed Water Testing.
Flow Monitoring
Flow monitors are installed in specific locations throughout the sewer collection system to determine flow rate and volume. This information will be used to develop a wet weather plan, narrow down the locations of excess flow sources, and may be used to assess increased fees necessary to cover the costs of treating any of this flow that cannot be effectively removed from the system.
Dyed Water Testing
Dyed water testing is a method used to locate rain or ground water entry points into the sanitary sewer system. During this process, non-toxic dyed water is introduced into roof drain leaders, driveway drains, or area drains. In some instances, dyed water is injected into the ground around foundations to check for the illegal connection of foundation drains. After introducing the dyed water, the downstream sanitary sewer manhole is checked, or if an inspection port is present, it is checked for dyed water.
Smoke Testing
Smoke testing is another effective method of locating sources of inflow and infiltration problems with sewers. The non-toxic "smoke" will help locate places where storm and other surface waters enter the sanitary sewers. It is conducted by placing a blower over a centrally located manhole and forcing non-toxic smoke-filled air through a sewer line. The smoke under pressure will fill the main line plus any connections, then follow the path of any leaks to the ground's surface, quickly revealing the source of inflow and infiltration.
Manhole and Pipe Inspections
Manhole and pipe inspections are conducted to assess the integrity of the collection system. The inspector documents information such as the construction materials, ring size, depth to invert, flow conditions and evidence of surcharge for each manhole. These will allow the system managers to plan the most efficient means to eliminate the excess flow sources.
Closed Circuit TV (CCTV) Inspections
A CCTV inspection uses a television camera mounted on a robotic device that is connected to a video monitor. The robotic system is placed directly into the sewer through a manhole. Once inside the sewer line, the robotic device can be operated by remote control located inside a truck. The operator can examine the entire length of sewer line between two manholes.