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Investigating changes The newly revised BS5930 Code of Practice for site investigations, which includes updated sections on soil and rock description, geophysics and contaminated land, is due for rele

When it is replaced at the end of this year, under the new title Site investigations for civil engineering, the current version of BS5930 will be nearly 18 years old.

Time has largely been kind to the code of good practice, which is used extensively in contractual documents and regarded, to those outside this specialised field at least, as an industry bible.

However, the opening up of the European market, major technological developments in investigation and a rise in the use of brownfield sites for new development has meant many changes in site investigation working practices. This is largely reflected in the areas of major change within the code.

Since the last revision of the British Standard in 1981, there has been a move to a European framework of standardised codes through Eurocode 7, currently circulating in draft form. Part 1 of EC7 deals with geotechnical design and parts 2 and 3 cover field and laboratory testing for geotechnical design, but are less advanced.

The revision committee first met in October 1990 to review the code and highlight the perceived problems. Then in July 1991, British Standards Institution gave approval for the revision to start in earnest.

Working groups of five or six committee members were assigned subject areas of the code. These began by seeking informal comment from academia and industry, using some of these suggestions for the draft revision. The first draft was issued for public consultation in December 1995, with a closing date for comments by the end of March 1996. Around 200 copies were sent out to industry, with additional copies available for purchase direct from BSI.

Comments were collated by the institution and sent to the working parties for further revision. The final draft is now being completed by BSI before being sent back to the committee for any last changes. The document will then pass to BSI's editing department for publication.

Roy Wakeling, chairman of the drafting committee, says the main thrust of the revision was to update those areas that had become obsolete and to carry out minor revisions to others. So sections such as cable tool drilling will not have changed greatly but other areas where there has been technological advances, such as cone penetration testing and geophysics, have needed major re-write.

Wakeling adds that one of the main reasons for BS5930 revision was the need to keep in line with the new version of BS1377, Methods of test for soils for civil engineering purposes, updated in 1990. 'The two codes go hand in hand,' he says.

One area of the code criticised in the past was its lack of decent coverage of planning and procurement, considered to be one of the key stages of any site investigation.

There is a wealth of literature suggesting improvements to this section. By far the most comprehensive is the work carried out by the ICE Ground Board Site Investigation Steering Group (SISG). Site investigation in construction, published in 1993, is made up of four volumes - Without site investigation ground is a hazard; Planning, procurement and quality management; Specification for ground investigation; and Guidelines for the safe investigation by drilling of landfills and contaminated land.

The first two volumes were primarily written as aids to the decision making processes of planning, design and imple-mentation of site investigations, but were also intended to be guides for clients and principal technical advisers. This advice was intended as additional information that could be used in conjunction with BS5930. It was also suggested that the code needed positive statements encouraging a flexible approach to site investigation design.

Professor Stuart Littlejohn, SISG chairman, says his group's work was to be published some time in advance of the BS5930 revision. It was decided that the new code would not duplicate material in the first two SISG volumes but would instead give reference to them. 'We discussed it at the time with Roy Wakeling and a complementary approach was taken,' he says, adding that throughout the revised BS5930 there is 'an excellent set of references'.

And he sees the inclusion of a new contaminated land section in the revision being particularly important. 'The fourth volume of the SISG series was not originally planned, but we found that more and more companies were dealing with contaminated land issues.' SISG's main concern was that site safety on contaminated sites was not being dealt with adequately, with workers being put at risk. The move was also necessary because of the introduction of CDM regulations, explains BSI project manager Victor Mordecai.

Another area of the code that has undergone a fundamental change is Section 8 Description of soil and rock. In 1986, David Norbury, Ken Child and Tim Spink recommended a number of changes. Norbury, who works for geotechnical contractor Soil Mechanics, was one of four main authors of the revision of this section. He says recommendations given in the 1986 paper and subsequent work in the early 1990s have been incorporated.

These include a change from distinguishing between fine and coarse soils purely on particle size distribution to one based on cohesive or granular descriptions according to engineering behaviour. And the original weathering scheme (based primarily upon chemical weathering processes that are rare in the UK) has been replaced by one describing the degree of weathering of the whole rock mass.

Norbury adds that there has been an effort to make the section more user friendly. Of particular interest to site staff, he says, will be the revamping of the quick reference field identification and description table. 'The columns are now presented in the order that the engineering descriptions are written,' he explains.

And he was especially pleased with the feedback the working group received from industry during the public consultation period. 'It was encouraging that we received lots of constructive comments,' he says.

Geophysics in site investigation has undergone somewhat of a revolution, with new methods that are more applicable (and indeed more accurate) to shallow investigations on land. Wakeling says one of the major advances has been in data processing, allowing engineers to gain more from the data collected on site.

As a result, the section, which has largely been rewritten, now covers the established and new techniques in this field, offering more insight into this highly specialised field.

And the introduction is more positive than before, highlighting the savings in time and cost that the methods offer, especially in the early stages of investigation. It also emphasises the need to carry out field trials of techniques to check their suitability. It is also essential, it says, that the consulting engineer employs an independent geophysical adviser to ensure that the survey and the interpretation of the data produces useful results.

Littlejohn hopes that BS 5930 will provide the basis for any future European code for site investigation, considering the respect it has attained around the world.

Mordecai agrees, but believes that this is probably the last time BS5930 will undergo extensive revision. He says any further revisions will probably be carried out by CEN. It will then be more than likely be incorporated with the Eurocode system, 'although this is in the distant future', he adds.

Minor revisions will be made, however, in particular the regular review of the health and safety section under BSI's duty of care, and the routine review five years after publication, which is carried out on all BSI codes.

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