5837 soil assessments?

[Jesse]

I don't think many arb folk would have the skills or equipment to carry out a proper soil analysis. Normally on development sites, where soils are assessed, the structural engineer will make recommendations as to construction issues. I can't believe that a developer will take the word of an untrained arby when deciding what type of foundations to use. How many arby's can take soil cores down to 4m or more and then correctly analyse the soils within the core.

 

Even something which sounds simple like a pH soil test is full of potential problems. Many different pH kits give different readings for the same lump of soil. pH should be obtained from a sample base taken from a particular depth and in a particular pattern across the site.

 

My view is to tell the developer to get his own soil analysis carried out and then send you the results to include within your report.

You are correct, my comments were more towards those reports which I produce for the more domestic type of application ie single development or a garden plot or extension. There is no harm in commenting on a potential issue if you can quantify your findings or if your own knowledge extends a little further. When I left school I gained additional qualifications at college for the construction industry up to that of a building control officer and so the blend of knowledge which I now possess including my current arb qualifications works very well for me.

[Jesse]

I don't think many arb folk would have the skills or equipment to carry out a proper soil analysis. Normally on development sites, where soils are assessed, the structural engineer will make recommendations as to construction issues. I can't believe that a developer will take the word of an untrained arby when deciding what type of foundations to use. How many arby's can take soil cores down to 4m or more and then correctly analyse the soils within the core.

 

Even something which sounds simple like a pH soil test is full of potential problems. Many different pH kits give different readings for the same lump of soil. pH should be obtained from a sample base taken from a particular depth and in a particular pattern across the site.

 

My view is to tell the developer to get his own soil analysis carried out and then send you the results to include within your report.

A good example of an issue which I raised within one of my reports was this -Background - I was the last to be asked to produce 5837 report it had been overlooked and it was needed urgently, the proposal was to create a new wing for a private care home (new 3 storey wing), all the other reports were in and the drawings had been completed by the commissioned architects and surveyors. There was supposedly an issue with a tpo'd tree regarding protection which I dealt with without any problems. One thing which no one had taken into account was the presence of a large poplar tree located off site and some distance away from the proposal. I cross referenced all relevant info 5837 guidance nhbc guidance including gs maps and carried out some soil tests and gave the info regarding foundation type to protect the tpo'd tree and recommended that they re-instruct the structural engineer/surveyor to review my findings because of the given soil type which I had identified at that site and most importantly the precise extent that the poplar tree could influence soil change at that location. As a direct result of my detailed input the whole foundation design for that proposal was changed considerably much to the annoyance of the developer but the client was extremely pleased with my findings and to the extent of detail that I had produced. The architect also was extremely pleased with my findings.

[Pedroski]

There's no 'simple' pH test. If the goal is to characterise a whole site then a properly designed sampling protocol needs to be employed, so that you can obtain a result that means something. This can involve taking many sample, measuring pH, and using analysis of variance, to get an idea of the uncertainty in pH measurements across the site and to determine how the pH varies both across the site and at varying depth.

 

If you pop along to the site, take a sample, measure the pH and put in a report that the 'soil pH is 8.1'. then it means nothing. You could well measure pH at a different depth or at a different sample location and get a completely different result.

[sloth]

There's no 'simple' pH test. If the goal is to characterise a whole site then a properly designed sampling protocol needs to be employed, so that you can obtain a result that means something. This can involve taking many sample, measuring pH, and using analysis of variance, to get an idea of the uncertainty in pH measurements across the site and to determine how the pH varies both across the site and at varying depth.

 

If you pop along to the site, take a sample, measure the pH and put in a report that the 'soil pH is 8.1'. then it means nothing. You could well measure pH at a different depth or at a different sample location and get a completely different result.

 

That what I thought. It seems silly to go all out testing soils at the off set of the planning/design process, an unnecessary expense. A better option would be to leave pi tests etc for the engineers; test soil ph etc where there is to be planting (when its decided where it will be); and use best judgement of where long term areas of compaction etc may have affected the distribution of roots for rpa purposes. Could be included in the detailed AMS perhaps?

[sloth]

As a direct result of my detailed input the whole foundation design for that proposal was changed considerably much to the annoyance of the developer but the client was extremely pleased with my findings and to the extent of detail that I had produced. The architect also was extremely pleased with my findings.

 

A good outcome how much of an engineering/building background do you have, just out of curiosity?

Edited May 7, 2012 by sloth

[Amelanchier]

My view is to tell the developer to get his own soil analysis carried out and then send you the results to include within your report.

 

My sentiments entirely - notwithstanding a degree in physical geography.

[Jesse]

There's no 'simple' pH test. If the goal is to characterise a whole site then a properly designed sampling protocol needs to be employed, so that you can obtain a result that means something. This can involve taking many sample, measuring pH, and using analysis of variance, to get an idea of the uncertainty in pH measurements across the site and to determine how the pH varies both across the site and at varying depth.

 

If you pop along to the site, take a sample, measure the pH and put in a report that the 'soil pH is 8.1'. then it means nothing. You could well measure pH at a different depth or at a different sample location and get a completely different result.

PH is just 1 consideration more to do with plant & tree selection with regard to the new planting scheme for a development. Within my geographical area we are mostly on clay soils so I am more interested in assessing & providing if appropriate an indication of plasticity index of a soil or I can even provide a measurement value of the category of soil taken from a site. The definitive soil type of a site can only be identified by laboratory analysis and to provide this I send the samples off. British Geological Survey sheets provide additional information regarding the underlying strata of a site. Samples are taken from a range of locations around the build area and at a range of depths using spade and a small auger, a simple tactile test also helps. Details of the location and depth from where the samples were taken are also included within my reports. I also carry out Subsidence Risk Assessments.

[Pedroski]

PH is just 1 consideration more to do with plant & tree selection with regard to the new planting scheme for a development. Within my geographical area we are mostly on clay soils so I am more interested in assessing & providing if appropriate an indication of plasticity index of a soil or I can even provide a measurement value of the category of soil taken from a site. The definitive soil type of a site can only be identified by laboratory analysis and to provide this I send the samples off. British Geological Survey sheets provide additional information regarding the underlying strata of a site. Samples are taken from a range of locations around the build area and at a range of depths using spade and a small auger, a simple tactile test also helps. Details of the location and depth from where the samples were taken are also included within my reports. I also carry out Subsidence Risk Assessments.

 

That's good, but I do have one concern. You are taking on soil analysis, sending samples off for analysis, producing a report - is this something you are qualified to do? I know you mentioned a college course, but if you're providing soil analysis reports then it might be worth considering the implications of a wrong decision being made on the basis of the report you are providing. Just as a 'what if?', what if a developer was put to a load of additional expense and decided to seek a second professional opinion, which showed that your report was incorrect? There would be potential for a claim for compensation. Would your insurance cover it?

[Jesse]

That's good, but I do have one concern. You are taking on soil analysis, sending samples off for analysis, producing a report - is this something you are qualified to do? I know you mentioned a college course, but if you're providing soil analysis reports then it might be worth considering the implications of a wrong decision being made on the basis of the report you are providing. Just as a 'what if?', what if a developer was put to a load of additional expense and decided to seek a second professional opinion, which showed that your report was incorrect? There would be potential for a claim for compensation. Would your insurance cover it?

 

I very much take on board what you are saying, yes i am insured to produce Subsidence Risk Assessments , I did when i first obtained insurance to carry out these type of surveys and reports have to provide evidence to my insurance company including my qualifications and experience in this field together with a number of examples of the reports and type of work i am involved with. Regarding my own expansion into this area (soil) its just evolved over time, the other draw has been from 5837 and the cross over point where different surveys can join. Now i know i am referencing from 5837:2005 but i suppose its your own interpretation of the document-"1.4(d) the approximate location of trees on land adjacent to the development site that might influence the site or might be important as part of the local landscape character." "Influence" being the key word, above or below ground. The water uptake of a given sp should be taken into account as well as shade pattern, future growth and its suitability in general as a retained tree. Where clay soils are known to be present a cross reference to NHBC Chap 4.2 will provide the equation to calculate the extent to which the zone of influence can be measured. Assumptions on the PI of a soil can be made using field tests and GS sheets (As an indication only) definitive results can only be obtained by laboratory analysis. In a way I just collect samples and data , its all fairly straightforward to me, if that's the way my investigations take me. I know this ref is from the land survey but if it's not being raised in other reports/surveys it should be. I don't go in both guns firing but i do read all other reports first if available to see if anything has been missed.

[Paul Cleaver]

you can get a PI test from ADAS