Cities and provincial governments are aware of the general overall condition of the various infrastructure systems.
They are working to develop plans to bring the infrastructure deficit under control. What is missing is a comprehensive system wide approach to the condition assessment of these extremely large linear assets such as wastewater collection systems. Using zoom camera inspection technology as the first step in the development of asset management plans will assist operating authorities in getting started on a system wide solution.
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Traditionally, operating authorities responsible for the ongoing asset management of wastewater collection systems would complete a CCTV inspection of a portion of the system each year or in conjunction with the capital works program in any given year. This approach results in an incomplete set of data and doesn’t effectively look at the entire system in a cohesive manner. Asset managers need to manage from a system wide perspective to capture the best bang for their buck when spending rehabilitation and/or replacement capital dollars.
When a team simply follows the roads replacement list and checks the sewers before paving the street, it may well be spending dollars on a marginal sewer rehabilitation on one street, while under the next street, there exists a major sewer in a significant state of deterioration.
An Alternative to CCTV
By adopting a system wide approach through the application of zoom camera technology, asset managers obtain the overall assessment of the system and can apply their funds in a more effective manner.
Zoom camera technology, and specifically, truck-mounted zoom camera inspection systems have been used in Ontario and Quebec since the mid-1990s and have demonstrated their capabilities over the past 20 years to provide the system-wide data that asset management teams require. Zoom camera inspection systems utilize a zoom camera attached to a telescopic mast mounted on a vehicle and connected to a computer with standard sewer condition assessment software.
A truck-mounted system is required to facilitate the data collection process where a field inspection team will complete approximately 25 manholes daily, and will be operating in active traffic conditions. Typical hand held zoom camera systems generally do not have the same zoom or lighting capabilities of truck mounted systems and are unable to be deployed effectively on a system wide inspection program.
The basic zoom camera inspection process involves having the vehicle position the camera and mast over a manhole, lowering the camera on the telescopic mast into the manhole while video recording the condition of the manhole from top to bottom. When the camera is lowered to the bottom of the manhole, the field crew positions the camera in front of the opening of each attached sewer pipe and the camera operator, utilizing the zoom camera functionality of the camera, inspects each sewer line from the manhole.
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The field technicians complete the inspections and code the asset condition defects onsite, following prescribed NASSCO PACP and MACP defect coding principles. The benefit to coding while completing the defect coding onsite at the time of the inspection, is that the field crew can adjust the camera position during the inspection process to better capture video that clearly depicts the actual conditions within the sewer lines and manholes.
The zoom camera inspection technique is completed without flushing the sewer lines and field crews are able to complete the inspection of approximately 25 manholes and associated sewer pipes in a standard eight-hour workday. Over the past decades, the sewer industry has compiled a vast amount of data on sewer condition assessment and in general terms, it is usually stated that 80 percent of the damage in a sewer line occurs within 20 m of the manhole.
The zoom camera inspection process, whereby the field inspection team inspects a sewer line from each manhole, captures the majority of these defects within the sewer lines, as most zoom camera systems are capable of zooming well over 60 m down a typical sewer line. The application of zoom camera inspection costs approximately one-third the cost of regular flushing and CCTV and can be completed in one-fifth of the time.
Based on 20 years of data, on average, zoom camera inspection results will clearly define the sewer operational and structural condition ratings as compared to standard CCTV inspection results. Zoom camera inspection data will typically indicate that approximately one-third of any system will require any further follow up inspection with regular CCTV. This results in substantial savings for the operating authorities.
Zoom camera inspections result in a complete inventory of the system, manholes, catch basins, chambers and sewer pipe conditions.
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The standard CCTV inspection process requires the sewer lines to be flushed prior to the completion of the camera inspection to facilitate the camera travelling through the system and to ensure the entire pipe circumference is visible to aid in the structural assessment of the pipe condition. This approach, flushing before inspecting, removes the majority of the evidence of the operational conditions within the sewer line, such as debris, roots, grease, etc. A quick review of the NASSCO PACP sewer condition assessment codes shows that the operational codes describing the flow conditions in the sewers comprise a significant portion of the assessment process. The current prescribed method of sewer condition assessment starts by flushing out this data, leaving only watermarks and stains on the pipe wall for asset managers to interpret.
The System-Wide Approach
From the perspective of asset management and the application of zoom camera inspection technology, the following outcomes make truck-mounted zoom camera inspections a valuable tool in the development of long-term asset management initiatives.
1) Truck mounted zoom camera inspection programs, yields a viable system-wide assessment of both the sewer pipe network and the associated manholes. PACP and MACP condition assessment provides the structural condition of the sewers as well as infiltration and flow conditions.
2) Zoom camera inspection data clearly depicts in-situ debris and flow conditions within the entire wastewater collection system. Cities such as the City of Hamilton, Ontario, rely on an ongoing zoom camera inspection program to drive their sewer flushing program. This means they are only flushing lines that actually have a need, resulting in cost savings versus flushing entire areas and reduced damage to the existing sewer lines from the flushing activity.
3) Identification of infiltration in sanitary sewers is noted in manholes and pipes. Identification of cross connections to storm sewer systems is possible because the data that normally indicates a cross connection, specifically toilet paper and waste are removed by the pre-flush operation of standard CCTV.
4) Inspection of the entire waste water collection system instead of continuing to inspect isolated areas of interest. The data from the sewer condition assessment can be matched up to the road network condition assessments allowing for the development of a more refined asset management plan.
5) Debris levels noted in an initial zoom camera inspection program will form the baseline for the ongoing monitoring of the operational flow condition of the system. During the initial inspection process, the debris levels are noted but it is unclear how long the debris took to accumulate. If an operating authority applies the system-wide zoom camera inspection method, in subsequent years, the debris levels will provide a clear indication of the flow conditions in the sewer lines.
6) Similarly, the structural condition of the sewer lines will be able to be monitored over a reasonable time frame. Based on historical comparisons, the results from a zoom camera inspection program yield comparable condition rating results of sewer conditions and as such can be utilized to refine CCTV inspection programs. Again, similar to the flushing issue noted above, only conduct detailed CCTV inspection of lines that have noted deterioration.
7) In areas with sewer deterioration due to hydrogen sulfide attack, the operating authority would be able to monitor sewer degradation without further damaging the lines with high pressure flushing and in cost effective manner on a cyclical inspection program.
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The application of a truck-mounted zoom camera inspection program by a wastewater collection operating authority yields a comprehensive system-wide assessment of both the operating and structural condition of the assets.
Donald Gunn, C.E.T., is president of Infratech Services/CTZoom Technologies.