Posted By Struan
Is there a truely tried and tested way of avoiding known sevices and utilities?
We are given plans, sketches, scaled drawings,locators / avoiders etc. All fine, but some utility providers are using PE pipes which, as far as I'm aware, can only be located by Ground Penetration Radar, or by relying on the (limited!) information from the utility company.
The HSG 47 provides good, sound guidance but I believe that the utility companies dont go far enough in providing ease of location, both for themselves and others who need to expose or locate the utility.

Posted By Stuart Nagle
Struan.

I agree, locating utilities service is not an exact science, unless you become very skilled in the use of cable locating tools and the service you are trying to locate is capable of being detected.

In my own experience of undertaking excavations - back in the days when the spade was the tool used, even when adept at using the new fangled cat and genney or radio-detection scanner, exact location (from the surface) was not ever going to correctly locate the service - only provide a guide. Once roughly located, services were excavated (sfter the hard surface was broken open by a breaker) by 'careful' hand excavtion.

Even then it was possible to cut, break or bust services on occassions, but use of the cable locator in the excavation itself also helped to avoid this by gradually turning down detection sensitivity and testing the range of sensing on another piece of equipment to show how far away you might be from the service helped form a more accurate location...

I understand that nowadays, some 'plastic' pipes do include a strip of material capable of being detected through an induced signal from a cat, although I have not seen this myself. What I do note however is that the utility companies themselves seem very rarely actually hit their own or other equipment when excavating, for example to replace valves or connect new services etc. Could it be they are more expert and better at locating equipment and services than civils contractors (bish bash bosh - seen the video of the guys mine detecting with shovels?)

Given that the buried equipment is usually shown on 1:2500 scale drawing, the line of the quipement shown can be anything up to 2 metres wide, so this certainly allows some scope for missing as well as hitting the equipment, and as I am sure you will be aware, all drawings from 'statutory undertakers' carry a big red stamp stating that the location is only approximate and the person excavating must take such measures as necessary to correctly locate the equipment.

I think at present we have reached state of the art in detection, until someone decides to develop better equipment, but gound radar may still be a bit expensive for general civils contractors operations...

Stuart