Abstract
The core principles of collecting good quality data from site for creating CCTV inspection reports including some explanations of how to avoid common mistakes.
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The PLR Naming Convention
Most global drainage inspection standards include a system for naming pipes based on either the upstream manhole ID or a combination of both the upstream and downstream manhole IDs. The Manual of Sewer Condition Classification (MSCC) defines the naming convention for WRc pipe and sewer inspection using the Pipe Length Reference (PLR) system at all times:
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Other than that, the logic is exactly as described here.
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Good Site Drawings
Everything described above regarding avoiding problems with data in software applications can be avoided by taking care and time to create good quality site drawings. The process described here considers a domestic CCTV inspection but the recommended logical approach can be extended to any type of CCTV inspection.
The golden rule of CCTV inspections is to always start with a site sketch before getting the camera system ready to go, and take time to make it useable. If you do your job correctly on site and deliver you drawing and inspection dat aback to the office in a good shape, then nobody will ever have to call you up a few days later and start asking some questions while they are trying to write th report and make some rehab recommendations.
Step 1 on arrival on site - start with a drawing layout of the property site showing the outline of the buildings, significant points of interest and the property boundaries that are relevant, something like this:
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Site drawing part 1.
The sketch already contains some useful text information and the general site layout. The significance of writing down the surface type is that once we do the inspection and find that there are some serious problems, we may need to recommend a dig-up and if this is the case then the people in the office doing the quotation will want to know what the surface condition is so that they can quote accurately.
Step 2 - safely pop up some manhole lids and have a look at surface visible node points (gullies, SVPs, RWPs etc), and also look a little more closely at the building for the signs of small windows with frosted glass and 20mm overflow pipes poking through walls for evidence of things like downstairs toilets inside the property. From this, you should quickly be able to come up with an approximation of the drainage layout for the site based on your own expertise, like this:
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Site drawing part 2.
Notice in the drawing we have used red lines for foul drains and blue for surface water objects. There is not hard and fast recommendation for this and different water companies use different colours for this so you can be fluid, but it is advisable to at lease have some coloured pens to hand for this reason, particularly where there are separate foul and surface water systems at the site.
Step 3 - add some annotations to the drawing to clearly identify each node point on the site and do not forget to make up node IDs for ‘invisible’ connector nodes. Add some information about the physical attributes of the pipes and nodes based on observation. All of this will make life a whole lot easier when it comes to actually carrying out the CCTV inspection:
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Site drawing part 3.
Step 4 - crack on with the CCTV inspection. Life will be really easy now when it comes to entering the upstream and downstream nodes for each pipe that you camera. Just be a little careful of the connector nodes. The WRc inspection standard requires that pipe inspections are done from end to end, so in the example above, we could inspect IC2 - IC3 either upstream or downstream, and we would never inspect IC2 to CN1 or IC3 to CN2. We would simply inspect the whole pipe and add the appropriate junction or connection observation does at CN1 and CN2 as required and carry on until the end of the pipe at the next chamber or node point.
If we needed to inspect the pipe from WC1 to CN1 in a situation like this where there is no chamber at CN1, then we need to practice the ‘Indian Rope Trick' with the camera where we tie a piece of rope to the spring behind the camera head, push the camera up from IC3 to CN1 without any recording and with the rope attached and then push the camera cable while pulling the rope so that the camera flicks into the junction. Now, we pause, set the distance counter to zero on the camera and create a new clean inspection on the lateral (this is a true lateral - a pipe coming into a manhole is not a lateral) WC1 to CN1, upstream.
Step 4 - make some notes based on what you have seen and deduced during the inspection for the office:
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Site drawing part 4.
That’s it, your job as a CCTV surveyor is complete provided that the video files and data that you have recorded on your CCTV camera match up with this drawing. Based on the information reported here, the office rehab manager can either go with your recommendations or create their own, but regardless of which way they go, they have enough information in the video files, pictures and (mots importantly) the very good site sketch to make all the good and proper quotations needed for this job.
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Understanding STC25 Manhole References
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