6 Personnel for ground investigations

6.1 General

Personnel involved in carrying out a ground investigation should have suitable qualifications, skills and specialist experience in ground investigations generally. They should also be familiar with the purposes of the particular investigation and be suitably skilled and experienced in the specific methods of investigation required.

NOTE A guide to the qualifications required for the various levels of seniority is given in Effective site investigation [6].

6.2 Direction, planning and execution of an investigation

COMMENTARY ON 6.2

Attention is drawn to the Construction (Design and Management) Regulations 2015 [7].

For all projects where more than one contractor is involved (the majority of contracts involve more than one contractor at some stage), the client should appoint a principal designer who is responsible for coordinating the pre-construction phase of the works and ongoing design. The client is responsible for ensuring the principal designer is competent to carry out the works and is adequately resourced. There is likely to be a wide range of designers for the design, planning and execution of the project — all of whom should coordinate with the principal designer.

NOTE 1 The principal designer might be a chartered engineer, structural engineer, architect or, on simple projects, the principal contractor and they might not have specialist expertise in geotechnics and/or geology.

A geotechnical adviser should be appointed who is directly responsible to the principal designer for the planning, direction, execution and supervision of the ground investigation. More than one adviser may be appointed to take responsibility for different parts of the investigation because, for example:

a) the scoping, planning and design of the investigation might be separated from the execution and supervision by contractual arrangements; and/or
b) expertise might be required for a range of disciplines such as geology, engineering geology, geotechnical engineering, geophysics, hydrogeology and contaminated land.

The geotechnical adviser(s) should be suitably qualified and experienced.

NOTE 2 It might be advisable for the geotechnical adviser to be registered with the UK Register of Ground Engineering Professionals (RoGEP) or similar as a means of demonstrating their ground engineering competences (see Effective site investigation [6]).There are three grades of registrant in RoGEP and it could be implied that a Registered Ground Engineering Professional would suffice for a relatively simple investigation whereas Specialist and Adviser grades are more appropriate as the complexity increases.

The geotechnical adviser should determine the extent and adequacy of the investigation, direct the investigation both in the field and in the laboratory, and should finally assess the results in relation to the design of the proposed works. The geotechnical adviser may delegate part of these duties to other specialists who are on their staff or who act as consultants or contractors.

The person responsible to the geotechnical adviser for the execution of the ground investigation might be on the staff of the geotechnical adviser, or might be a geotechnical consultant or contractor; they should be a suitably qualified geotechnical specialist, as required by the character and scope of the ground investigation.

6.3 Supervision in the field

The supervision of the work in the field should be either the full-time or the part-time responsibility (depending on the size of the investigation) of a suitably qualified and experienced practitioner.

NOTE This person (referred to as the "investigation supervisor" in UK Specification for Ground Investigation [8] or the "responsible expert" in BS 22475-2) might be assisted by, or delegate this responsibility to:

a) assistant geotechnical engineers or engineering geologists;
b) field engineers and senior field technicians who are skilled in the work described in 6.7 and who are competent to supervise such work by others, and in addition might be required to supervise work described in 6.8.1 and 6.8.2;
c) geophysical experts who are skilled in the work described in Section 5, and who are competent to supervise such work by others;
d) drilling supervisors who are skilled in the work described in 6.8.1 and who are competent to supervise such work by others, and to supervise the work described in 6.8.2.

6.4 Logging excavations and boreholes and describing soils and rocks

Detailed descriptions for engineering purposes of all the soil and rock samples obtained (see Section 6) should be made by a suitably qualified and experienced geotechnical engineer or engineering geologist; these engineering descriptions are incorporated in the field logs to form part of the report preparation.

For more extensive investigations, it is preferable for this work to be carried out on site, and proper facilities should be provided. However, for smaller investigations, the description may be made at the premises of the ground investigation contractor or at another suitable location.

NOTE For rotary cored boreholes, it might sometimes be necessary to have the full-time attendance on site of an engineering geologist so that the rock cores can be logged and described in their fresh condition as the work proceeds.

The qualified operator, who is commonly the lead driller, should be responsible for recording the information obtained from the borehole as it arises (see 6.8.1 and BS 22475-2); this should include a measured record of strata, with simple soil and rock descriptions.

Where trial pits and other exploratory excavations are required and where existing natural or man-made exposures of the ground are involved, the detailed recording of the soils and rocks, their stratification, structure and fabric should be made by a suitably qualified and experienced geotechnical engineer or engineering geologist.

6.5 Laboratory work

The testing of soil and rock samples should be carried out in a laboratory approved by the client's geotechnical advisor, under the control of a suitably qualified and experienced supervisor. Laboratory technicians should have received training and/or have experience of the type of test they are conducting.

The laboratory chosen should be competent to carry out the testing and analyses required by the test methods. Laboratories are accredited for each test and this should be checked as required (see Foreword).

NOTE It is desirable that the laboratory participates in external proficiency testing schemes, as available, relevant to the work being commissioned; see the AG5 website ⁶⁾.

6.6 Interpretation

COMMENTARY ON 6.6

The preparation of the report, including the factual information obtained and the engineering interpretation of the data in the report, is described in Section 10.

The report should be prepared by suitably qualified and experienced persons (see 6.2b) under the supervision of the geotechnical adviser.

6.7 Field technicians

Field technicians who carry out sampling and testing in boreholes and probing (see Section 4), geophysical data acquisition (see Section 5), field tests (see Section 7) and instrument installations (see Section 8) should be suitably qualified and experienced in the work.

6.8 Operatives

6.8.1 Lead driller and driller (support operative)

There should be a lead driller in charge of each individual drilling rig, who should be skilled in the practice of exploration of the ground by means of boreholes, sampling and in-situ testing, in making groundwater observations in boreholes, and properly recording the information obtained.

NOTE 1 The qualification criteria for personnel is given in BS 22475-2.

NOTE 2 It is advisable that all lead drillers employed on the contract hold a valid audit card of competence applicable to the work and the specific drilling operation (e.g. dynamic sampling, cable percussion, rotary) on which they are engaged, as issued by the British Drilling Association or an equivalent body. It is also advisable that they hold a Construction Skills Certification Scheme (CSCS) blue skilled (Land Drilling) card and that drillers who are support operatives to the lead driller hold an appropriate, valid and current audit card of competence and a blue skilled (Land Drilling) CSCS card.

6.8.2 Operators of the excavating plant and ancilliary plant

Operators of the excavating plant should be skilled and experienced in its safe use for digging trial pits and trenches.

NOTE 1 It is advisable that operators hold a valid and current Construction Plant Competence Scheme (CPCS) card for the category of excavating plant being used.

Support of excavations should be designed by competent persons and installed by suitably skilled operatives. The appointment of a temporary works coordinator is strongly advised.

NOTE 2 It is advisable that operators of other plants listed as a CPCS category hold a valid and current CPCS card.