| A.1 |
The working party shall refer to Section 3.2.1 of the Code of Practice on Working near Electricity Supply Lines . They shall decide whether the works site is within the vicinity of underground cables in accordance with the distance specified in Table 1 (i.e. Section 1.3.2.5). If the cable plans supplied by the electricity supplier indicate that there are underground cables within the works site and/or the area of the specified distance from the works site, the working party shall appoint a competent person to carry out the cable detection work. |
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| A.2 |
According to Section 3.3.1(a) of the Code of Practice on Working near Electricity Supply Lines , great cautions have to be exercised when exposing the target underground cable. The excavation of trial holes shall be supervised by the competent person who should repeatedly use a cable detection device and frequently update the working personnel with the most accurate cable location until the target cable is exposed. Section 3.3.1(b) indicates that the target cable inside the trial hole is adequately exposed so as to permit the competent person to place a signal clamp around it. A known high frequency signal is injected into the cable by electromagnetic induction through the signal clamp. As only the target cable carries this high frequency signal, the competent person can use a receiver set to this signal frequency to detect at appropriate interval (say, 1 to 3m) the alignment and depth of the unexposed part of the target underground cable, starting from the trial hole. |
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| A.3 |
According to Section 3.3.2 (b) of the Code of Practice on Working near Electricity Supply Lines , if the alignment of the peak signals is located between the area 500mm and 3m away from the works site and it is not practicable to dig trial holes within that area (e.g. the works site is on a footpath whereas the alignment is located on a carriageway), the competent person should propose the following:
- Dig a number of trial holes along the boundary of the works site opposite to the alignment of the peak signals. The competent person shall determine the number of trial holes based on the alignment and the number of cables within the group. In principle, the closer the alignment and/or the greater the number of cables within the group, the more trial holes will be required.
- The trial holes should be proposed at the locations where the peak signals are closest to the works site.
- The trial hole should be excavated at a right angle to the alignment and extended 500mm away from the works site.
- The alignment and depth of any cables found in the trial holes shall be ascertained by means of toroidal active detection.
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| A.4 |
Photocopies of the following documents are required to be submitted in an application for approval as a competent person:
- current Certificate of Approval as a competent person (for renewal applicant only);
- testimonials, certificates of relevant education and qualifications;
- testimonials, certificates of relevant apprenticeship or training;
- testimonials, certificates of relevant training course in the locating of underground electricity cables issued by recognized organizations;
- testimonials, certificates of services or employment to certify that the applicant has had no less than 6 months' (for new applicant) or 3 months' (for renewal applicant) practical experience in locating underground electricity cables during the 3 years immediately preceding his application; and
- supplementary documents of practical experience during the work or employment period mentioned in (e) above:
- three underground electricity cable detection reports showing the applicant has carried out or assisted a competent person to carry out such work; and
- letter from the competent person verifying the applicant has assisted in the work mentioned in (f)(i) above (for new applicant only).
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| A.5 |
Upon completion of active cable detection, according to Section 3.4.1 of the Code of Practice on Working near Electricity Supply Lines , the competent person is required to prepare a proper record form for submission to the working party appointing him. The form shall bear the "Competent Person Written Report" and include the following details:
- name and approval number of competent person;
- name of the working party or site contractor;
- location, date and time for which the active detection was carried out;
- the cable layout plan detailing the alignment of each underground cable based on common reference points (e.g. lamp pole, traffic light post, or hydrant, etc.) and any cable sections in shallow depth (Note: a cable alignment band can be used to represent a group of underground cables of which the ascertained alignments are very close to each other. The alignment and size of the band shall be dimensioned and the number of underground cables that the band represents shall be specified.);
- depth profile of each underground cable (i.e. cable depth corresponding to each measurement point along the cable alignment);
- voltage level of each underground cable;
- electricity supplier's advice, if any;
- photos showing the toroidal active detection and site markings for cable alignment and depth; and
- brand name, model number, serial number, calibration record and the adopted frequency of the underground cable detection device used for the detection.
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