Geotechnical info on structural drawings 7

[Taro]

For building projects I work on, geotechnical requirements (subgrade compaction, slab base materials, etc.) are usually contained in a soils report that is not officially included in the contract documents that the contractor bids on. Because the soils report recommendations are not written in mandatory language and are not part of the contract documents, the architect sometimes asks that the information be shown on the structural drawings.

I try to resist this because I am not in responsible charge of the geotechnical engineer and do not want to assume liability for areas beyond my expertise. I suggest that the geotechnical engineer prepare drawings and/or specifications to be included in the contract documents. However, this usually does not seem to be included in the geotech's scope and the client does not want to pay for it.

Have others experienced this? How do you handle this?

 

[SlideRuleEra]

I worked for the Owner of a large industrial project that had extensive geotechnical investigations performed under a dedicated contract. For the follow-on construction contracts, we presented the geotechnical "General Arrangement" drawing as Reference Documents. These drawings showed information such as the location of soil borings, field blow counts, etc. A statement in the Request for Proposal told the bidders that they could review the geotechnical detail information (filling about 3 drawers in a filing cabinet) at the Owner's office. Had no problems or "squabbles" later.

 

[Lutfi]

Here is what I do:

1. I include the geotechnical report as an appendix to the constructions specifications (I hope everyone do these)
2. Edit the specification section for earthwork to either match the soils report or cross reference the contractor to the appendix).
3. On large projects, I draw the boring logs on the plans (usually where piles drawings is involved).
4. I also have notations on the drawings general notes sheet.

I found through the years that some contractors do not read the specifications, as they should. That is why I leave data on the drawings as well.

Good luck

 

[JAE]

We basically do what Lutfi does except we rarely draw boring logs on our plans.

The geotechnical report is either included as an appendix to the specs, or we state in the specs/drawings that the report is available and its recommendations should be followed.

Our first sheet (notes sheet) includes reference to the report and its author/date/project number for future reference if needed and we include our applicable bearing pressures on the same sheet.

While the geotechnical reports are not written in mandatory specification language, they are still an essential part of any building project. Our structural plans can make the geotechnical recommenations "mandatory" by referencing them and stating "Compaction (or fill, or whatever) shall be in accordance with the recommendations of the geotechnical report".

 

[dik]

The following is from standard notes that I use:

FOUNDATIONS HAVE BEEN DESIGNED FOR AN ALLOWABLE SOIL PRESSURE OF 4,OOO PSF, EXCEPT AS NOTED ON PLAN, IN ACCORDANCE WITH THE GEOTECHNICAL REPORT PREPARED BY XXX, DATED XXX. CONTRACTOR SHALL REFER TO THE INFORMATION CONTAINED IN THIS GEOTECHNICAL REPORT SUPPLEMENT IT AS REQUIRED.

(Stuff deleted)

FOOTING BEDS SHALL BE INSPECTED AND REVIEWED BY A GEOTECHNICAL ENGINEER PRIOR TO POURING CONCRETE.

I do not bind the report into the construction documents nor do I refer to only 'part' of the geotech report... I was involved with one 'kerfuffle' where the consultant only included 'pertinent' parts of two separate reports.

 

[JedClampett]

If you're designing in an area that uses UBC, Section 1804.3 says that the "...soil classification and design-bearing capacity shall be shown on the plans..." except for stud bearing walls where specific footings are required.
This is much easier said than done. Within a project, there will be multiple soil classifications and bearing capacities. We don't do it except in vague general terms or when requested to by a plan checker. We either include the Geotechnical Report or make it available on request.

 

[Taro]

I typically do what each of you has stated. I reference the soils report on my drawings, show the parameters that were used in the structural design, and note that the soils report recommendations are to be followed. However, I am usually a subconsultant to an architect and do not have control over whether the soils report is included in the contract documents. Occasionally, the architect does not want the soils report included in the contract documents and asks that the information (slab sub-base materials, type of vapor barrier, etc.) be reproduced on the structural drawings. This is clearly not part of my design and should not be shown on the structural sheets. Agree?

 

[JedClampett]

I usually have no problem with including the Geotechnical information on my sheets. If you're worried about expanding your liability, forget it, you're going to get sued no matter what. I'd rather put the information out there to get the best chance of having it constructed correctly. If the instructions are hidden in a report somewhere, the contractor might (will) miss them and I haven't really gained anything. All of this assumes you correctly use the recommendations.
Think of it this way; You use Geotechnical information indirectly whenever you design a footing or concrete pier. What's the difference in directing the contractor in preparing the subgrade?

 

[JAE]

Taro,
I'm not sure I agree with the thought that geotechnical recommendations that affect my structural design are not part of my services (such as subbase prep and vapor barriers). These are integral aspects of my structural design.

I see the geotech report as a site-specific recommendation that gives me design parameters to create a structural entity. This is really not much different than the results of some research ending up in a code that guides my design as well.

I use the geotech recommendations to size my footings or to prepare the fill under the building. This is my engineering task as the structural engineer of record. Yes, I base it on the geotech report but its my job to ensure the foundation is properly designed and communicated to the contractor. The Geotechs do not prepare plans and specs for the contractor. Where else would this information get communicated to bidders?

Vapor Barrier recommendations are not real critical, and many times I ignore the geotech's advice, but its our job to take those recommendations and do something with them....not assume the contractor can get his hands on the report (non-contract binding) and respond to it intelligently.

 

[Taro]

JedClampett,
In terms of liability, the difference could potentially be HUGE. Say, for example, that there are localized areas of poor soil underneath a slab. The soils report recommends not removing the bad soil and replacing with structural fill, but instead bridging over the areas with geotextile fabric to save money. As a structural engineer, I have no idea whether this system will perform adequately. But if I show it on the structural drawings, I am assuming the liability. I would have a difficult time convincing a judge (who has no technical background) that I am not responsible for the information on the drawing that has my stamp and signature.

JAE,
You wrote "The Geotechs do not prepare plans and specs for the contractor. Where else would this information get communicated to bidders?" That's exactly my point. The geotech SHOULD prepare plans and specs. Most state licensing laws expressly forbid licensees from practicing outside their area of expertise. I am not a geotechnical engineer and should not be specifying geotechnical items. I think there is a BIG difference between that and using allowable soil bearing pressure to size a footing.

 

[JAE]

Taro:
Lets explore this a bit more. Your points are well taken and I agree that we should not "perform engineering" outside our expertise.

When a geotech submits a report for a project, you take their advice and proceed with a structural design (let's say a footing). You have taken the geotech's advice and produced a footing design based upon soil parameters which are theoretically outside your expertise. Are you then practicing engineering outside your area? I don't think so. You are depending upon another engineer's professional recommendation to produce a design of something you are taking responsibility of. This does not make you liable for the accuracy of the geotech's recommendation beyond the "standard of care" that any other competent engineer would take.

Similarly, if the geotech recommends a certain procedure for preparing soil beneath a building, you are not necessarily taking on his liability if you outline the procedure on your plans. If you can show that you followed the geotech report, and even explicitly say on your plans that the geotech report should be followed, then you have done what most prudent structural engineers do all over the country (USA). Many engineers even send their 100% documents back to the geotech to respond/comment on what is specified....which is an excellent practice.

Granted: anyone can sue, but by leaving off this information and expecting the owner/client to ensure that the geotechnical report is followed to prepare that subgrade properly is, in my opinion, not the proper standard of care for a structural engineer.

I have never seen geotechnical "plans" and don't believe this is ever done for most building projects.

Your thoughts?

 

[Taro]

JAE,
Of course we must rely on input from other disciplines in our designs. However, I disagree that we should specify detailed information relating to other disciplines on our drawings.

Let's say that you design a platform to support a mechanical unit. The unit operating weight and dimensions are given to you by the mechanical engineer so you can proceed with your design. You will probably note these criteria on your drawings and might show the unit schematically as well. But you would refer to the mechanical drawings and specs for more detailed information. What if the mechanical engineer said he was not being paid to produce contract documents and asked you to specify the unit model number, operating requirements, etc.? No way.

Just because the owner or architect does not want to pay the geotech to produce specs, that doesn't mean they should be able to foist the responsibility (and liability) off on the structural engineer. It's no big deal to show it on the structural drawings? Ask the architect show it on his own drawings instead and you'll see how big a deal it is.

 

[JAE]

I can agree with that - just seems that every project I've ever worked on (20+ years) and a multitude of 100's of others I reviewed or seen, there has never been a separate geotechnical spec or drawing.

Rather, the standard practice is one where the structural engineer or civil engineer (for site geotechnical work) specify on plans and in specs the required soil work - consistent with the geotech recommendations.

Your points make perfect sense....they just don't seem to be what I see our industry doing.

 

[JedClampett]

Wow! As you might expect, I agree with JAE more than with Taro. If a disaster happens (disaster=lawsuit), everyone is going to be dragged in. If you were given the Geotechnical Report, you're expected to adhere to it. If a structure settles, fails, leaks or whatever the structural engineer, the geotechnical consultant, the contractor, the fire sprinkler guy etc. will be dragged into the lawsuit.
I'd much rather my defense in that case be; "We (or the owner) hired XYZ Dirt Consulting and instructed the contractor to follow his recommendations. Either the contractor didn't follow the instructions or XYZ wasn't correct." I'd not want to explain that he clearly made recommendations and we didn't explicitly place them in the contract documents.

 

[Taro]

Thanks to all for the feedback. I know that the common industry practice is what it is and may be difficult to change. But it has bugged me for several years so I'm just stirring the pot to see what others think. On most projects, I have gotten by with referencing the soils report and requiring that the recommendations be followed. The soils report is included as a reference document to the bidders and everything works just fine. But on occasion I have been asked to reproduce the geotechnical recommendations on my drawings and it always rubs me the wrong way. Like I said, if it was no big deal, the architect wouldn't object to specifying the info in their own documents. But they don't want the liability either.

 

[VAD]

Gentlemen:

Interesting discussion and debate. There are several reasons for and against providing the geotechnical report with the contract documents. Those that prefer not to include the report feel that the report may have information that if not well understood by the structural engineer or architect may be cause for the Contractor to claim if things are not proceeeding well. Some also would like to keep the paper to a minimum. Some do not read the report and fear that it would conflict with their canned specifications.

The alternative used is to specify that the report is available for viewing etc. Very often the Contractors can make their own copies if desirable. Some Clients however have refused that option and restrict Contractors to reading and making their own notes. This is, however, not the norm.

I would assume that once I have provided a geotechnical report and made recommendations I am involved in the development of the project whereby I am able to review aspects that are influenced by the geotechnical investigation and recomendations. In this respect, I should be part of the process may it be for recognition or equally as well for liability if things do not work out well.

Irrespective of what we do today everyone gets sued or is dragged into the mess, hence our professional liability insurance is mandatory. I do not think that any geotech provides information without the understanding that he or she can be liable irrespective of whether being called upon to provide specs, drawings or the like.

Similar to Taro what rubs me the wrong way is when other disciplines just ask for a "soils report" without clearly defining what is required except that a buliding etc is to be constructed and all they want is a soils report.

Here is a schematic of the land and some perspective drawing or sections of the proposed building etc. If questions are asked at that stage then many times work on the design still has to be done. This is clearly understandable. However, likewise, it should be clear that the report by the geotechnical Engineer should also be viewed as a preliminary geotechnical report. However, because of costs that report is rarely seen that way and the geotech has to conjure up what may be typical for the site - spreads, piles, raft etc and other aspects such as compaction, pavement design for roadways etc etc.

Such a report may not therefore be totally acceptable for inclusion in the contract since apart from the geological descriptions, physical site features determined from the investigation there cannot be firm recommendations until the loads are provided and the geotech is able to review those in terms of the variuos types of possible foundation types for building envelope and road infrastructure works.

The provision of allowable bearing pressures for example is preliminary and are subject to modification depending on loading configurations. Granted for many projects this is all that may be needed, but strictly speaking the final design is not technically based on individual elements of the structure but on the entire structure foundations interaction of which the foundation design has to incorporate suitable geotechnical recommendations that should be sanctioned by the geotechnical engineer.

It is understood in many jurisdictions that that the Structural Engineer takes on the responsibility of the foundation design as he determines the loads. However, if any,this is the cruicial aspect that requires the geotechnical input when the foundation system is being finalized. With restrictive budgets this does not happen frequently.

As I see it therefore if the extent of involvement by the geotechnical Engineer is carried out to the fullest then there should be no problem in the geotech preparing plan sheets, specifications etc outlining what some of the issues are in relation to his aspect of work.

In some instances such sheets have been prepared and stamped by the geotechnical Engineer and provided as part of the contract package. This is typical done on larger civil projects or those where unconventional techniques are to be used.

There seems to be no uniformity of practice and one generally follows what the norm is in a particular jurisdiction.

Very often the problem boils down to one of money. Quite recently a driller friend of mine visited a building site with me on my request. I had the plans given to me and visited the site prior to our meeting. The site was covered with tall grasses but not too thick to prevent site reconnaissance. I laid out by tape measure the definition of the building areas. There were to be four buildings and as well positioned my test holes etc.

On his review, he asked me if any other geotechnical company was going to bid on the work. I said as far as I know I would be undertaking same. He then told me that the number of holes that I had laid out would not be done by others and that for those types of work one or two holes and the rest would be obtained from the word processor from past projects. I had laid out 8 holes two per building location. Nickel and dimes that are usually paid for these types of work as all is required is as mentioned before a "soils report" which is often seen as a "cover your rear" as this is required.

He then said to me that he has often wondered in his years of drilling, some 20 plus, why geotechnical companies do not advise their clients that there is merit in undertaking a good soils investigation as money could be saved during construction rather than doing skimpy work.

Well there are many comments to his statement. First some may want to say the more holes for him is more money in his pocket etc, but this is not the case. I think what we do not always know is the change orders that have to be made because of inadequate investigations and recommendations. Of course some one has to pay and it is generally the ultimate owner who is then told that it is so and so's fault and so on and so forth. The next step is claims and suits.

There is a need in my opinion to bring back the system from its progressive plunge into what someone called MacDonald's of Geotechnical Enginering. Unfortunately, this has been promoted by Geotechnical Engineers to a large extent.

There could be a turn around if all concerned disciplines make the Client aware of the importance of not only having a structure in the end but the understanding that the architect, structural engineer, interior designer, mechanical, landscaper, carpenter, labourer and geotechnical engineer etc have an important part to play in the process. I am sure that he will recognize the need to see that the work is adequately done by all and their importance. How often do we recognize the carpenter. He often has to make things work which are impractical on drawings

Too often the geotech is hired as a sub and the Client is hardly aware of his or her importance because the project was awarded to the structural engineer or architect who many times want the cheapest solution as the cheaper it is the more he or she can make on the transaction. So the shop around for the cheapest deal.

In closing I have no fear in providing whatever recomendations are needed at any time in the process. What I would like is to discuss professionally with other disciplines what I can do for them and what I see the project entails and learn from them about the project. The more I learn and understand the better I can be of value with my recommendations.

I am also fed up with hearing that Geotechnical work is too expensive.

Please excuse my digression in some instances from the theme of the topic.

[Cheers]

 

[jheidt2543]

A very interesting discussion! I would make the following comments, which are based on spending most of my career working for general contractors:

1. It has always bothered me that the soils report is the basis of the foundation design, but then is not in the specs or on the drawings. In some instances, the language used specifically excludes the soils report from the project.

If the architect and structural engineer use the report to design the building, then it should be included as part of the necessary information for the project. The more information available to the contractor the better the pricing is going to be. I haven't seen may lawsuits because too much information was available, it is usually the other way around.

2. I agree with earlier statements that once the lawyers get involved, everyone is in the soup. So, I think a thourgh soils report, included in a project specification in its entirety, is cheap insurance for the Owner and everyone connected with the job. Once the work starts, we are all in bed together whether we like it or not. So, you have to do whatever it takes to get the job done.

I once had an architect refuse to review structural steel shop drawings because shop drawing review wasn't part of his contract with the Owner! (he did the steel design in house and it was a design/build contract) You would think he would review them, regardless of his contract, just for self protection!

3. The concern about cost is a valid one on both sides of the contract. However, there are few areas in a project that REALLY affect the overall cost as much as the foundation of the building. A soils report suited to the site and project can save a lot of money by matching the correct foundation to the site conditions. The price of the site investigation is a small percentage of the overall project cost -- again cheap insurance.

 

[dik]

I forgot to include that I generally provide a copy of our engineering documents to the Geotech consultant also... with a covering letter... and, I've often seen Geotech reports with a note that the report is time limited (don't understand why; soil is usually 'forever') as well as a requirement that they be provided with drawings.

The blurb in my posting ties the Geotech report into the construction documents as well stipulates the bearing capacity that was used for the design of the spread footings (note was taken from spread footing part).

I usually tie quality control into an owner responsibility since the 'deal' is between him and the contractor and he directly benefits. I also stipulate minimum testing as a part of the documents with our office being provided with a copy of the results for project records only.

I've also had clients look after their own quality control, requiring that the contractor do same (a copy of the client's data was not to be forwarded to the contractor).

 

[BigH]

Fellow Engineers:

This is a most interesting discussion – I have only the part up through DIK of July 17 and much more may have transpired since. However, based on my reflections to that date, I would like to proffer my comments. I apologise at this time if this turns out to be a bit long. We have an interesting mix of disciplines, ideas, etc. We have structural engineers; engineers for contractors, finally a bona fide geotech in VAD and, of course, JHeidt2543 with his usually spot-on comments. Such a mix leads to interesting discussion. One point is apparent, though – all the respondents have their own agendas. The structural types are miffed by the lack of “mandatory language” in the geotechnical/soils report and why doesn’t he prepare plans and specifications. The geotechs are miffed about the lack of understanding of their siutation – and of course, low fees. You might read some of my other offerings, say in JHeidt’s question about Factor of Safety in this Forum. I have been in the geotechnical consulting business for some 20 years at which time I moved over to actual construction of highway projects overseas (7 years now). You all want to see the dung tossed out by so-called geotechs? designers? – I’ve seen it.

As VAD rightly pointed out – the geotech usually does not have full details on the planned works – he is left to surmise, presume as to the various components that will make up the project. Does the project entail basements? - (excavations/earth pressures on walls) . . . settlement sensitive equipment? - (high speed paper machines with, say, 5mm differential settlement over 25m) . . . dynamic equipment? – (stamping presses, turbines – damping/embedment, perhaps) . . . significant tension loadings involved? (guys for stacks or towers) . . . include . . .

You get my point. I’ve been involved, as many of you have, with quite a number of projects that lacked any real detail at the time the investigation is called for. Geotechs have to surmise on many aspects. VAD is correct – this type of investigation should be called and respected as a “preliminary investigation”. Most of our company’s old reports all had “Preliminary Soils Investigation” (or Geotechnical/Subsurface) in the reports title. We all knew, of course, that there would be no more work done on 75% of the projects until the time that foundation inspections are needed.

Given such sketchy information at the time of the investigation , how can you expect the geotech to use “mandatory language” in his report? He is usually assuming that his allowable bearing pressure, for instance, will be based on “norm” requirements of 25mm and 15mm differential. This is, of course, not the case for high speed paper machines. Most of the time, the machinery (say turbines) has not yet been bought so the dynamic characteristics that will, of course, affect the geotech’s recommendations for, say spring constants, will not be known.

Okay – this is a fact of life in the geotechnical business. And yes, VAD, geotechnical engineers in a large degree have brought this on themselves – my old mentor called it prostituting the profession. When, in Canada, we had Golders, Geocon, EBA, Thurber, Trow, Dominion Soils, National Boring and Sounding – the “old” established firms, there was a playing field that seemed pretty well established. (sorry Quebec) Now, we have so many break-off firms, basement firms, etc. that, well, . . .

Now, to the structural types. I understand the dilemma you are in with respect to handling geotechnical information. Putting the geotech’s boreholes on the drawings – using your design time for someone else’s work. Where to put the soils report: Appendix? Make it available in Info for Bidders? Let others read it – even in the “office”? The dilemma lies, in my view with the that others, not involved in the geotechnical investigation and subsequent design, might read the report. Why is this a problem? As I’ve pointed out earlier, the geotechnical report is usually geared to a project that is not fully specified at the time of the investigation – or the project has changed since the investigation was carried out. Further, the geotechnical report includes recommendations/comments for the design and construction of the project. Do you want the contractors to read these? The geotech might suggest that piled foundations would be the most positive choice for support of the structure with, say, closed end steel tube pipe piles the appropriate choice. Still, though, given the “toys”, you could found at shallow depth after ground treatment or excavation and replace, etc. Now, you have chosen to go for piles but your designer doesn’t like closed end steel pipe piles. He wants to use slender precast concrete piles. In construction, the contractor chooses a hammer that is big and the founding till is hard – the piles show cracking, some breakage during/after driving. Problems. If the soils report containing the recommendations is in the contract – even as an exhibit – the contractor will know that the structural engineer didn’t use the recommended more robust steel pile. This may cause some consternation for the design engineer.

Similarly, most soils reports give a compaction level for fill and the type of fill – say well graded sand and gravel compacted to 95% modified Proctor dry density or higher. The specs, borrowed from another project, indicates that the fill will be compacted to 98% modified Proctor dry density – and the type of fill isn’t defined. Now, if you say on your drawings that the contractor is to follow the soils report – what to do? There is a conflict in the report and on the drawings/specifications. Is it not a tad bit embarrassing to have 95% in the soils report and 98% on the drawings or in the specifications – or vice versa . As the receptor of various other design professionals (electrical, mechanical, etc.) and normally charged with the putting out the project specifications, for uniformity the specs should be written – surely edited – by a single agency.

Now to the contractors. Why do you want to see how the allowable bearing pressure was derived? Sure, you want to know the soils to be encountered (for digging to footing level, e.g., boulders in the deposits), you want to know if your construction methodology may cause disturbance and you need a mud mat (blinding concrete). But, how the designer chose his footing size and the assumptions he used, etc. is not immediately of your concern, really – unless of course, you want this information for subsequent claims.

Given the above, I propose the following for consideration:

1. Have the geotechnical engineer prepare two reports. The first report is the factual report. This report gives facts – undisputable. Includes geological setting, site description, soil strata encountered (including topsoil, pavement layers, etc.), groundwater conditions at the time of the investigation (perched levels, general levels, etc.), borehole logs with laboratory testing information included (liquid and plastic limits, natural water contents, undrained shear strengths). Include other lab data such as e-log p curves, grain size distributions, etc. Include chemical testing that may affect concrete. Borehole location plan. Keep it factual – no interpretation. The second report, is the interpretive report. This report will put forth the engineering discussion for the design and construction of the project for the designer’s use – recommended (primary and/or alternative) foundation type, estimated settlements, suggested fill details, lateral earth pressures, etc. INSIST on the two report system.
2. Include the factual report in your contract documents – either on the drawings or as “Information for Bidders”. The facts are given – all parties will know the soils encountered, the groundwater levels, the laboratory test results.
3. Keep interpretive report for your files. Some of the recommendations/comments may not have been followed if the design is like many I have seen. This report is a guidance report for the designer and does not HAVE to be seen by the contractor. Of course, the structural drawings should state the basic information used in design – you can glean this from the interpretive report or state what you, as the designer, finally chose to use.
4. Advise the geotechnical consultant of any changes in the nature of the project – it may be an adjustment in the building footprint from one part of site to another. I suggest that as the design proceeds, you call him in for an early review of your schemes so that he may comment and advise. If he needs to change his recommendations/comments, this is the time to do it – not after the contract has been let.
5. Consider letting the geotechnical engineer help develop the project specifications for earthwork construction. He will feel more like a team member and the structural engineer may feel better about staying within their expertise. In earthworks – say for highways – standard specifications do not always work. It will force the designer to put together project oriented plans and specification.
6. Let the geotechnical engineer review the final design and specifications to ensure that it is consistent with his understanding – for that is the basis of his recommendations/comments.
7. We, as a geotechnical company, on building of tailings dams (owner build) did put together specifications and drawings – but these projects are 90% geotech oriented.
8. Geotechnical engineers are not too expensive – pay for them now or pay more later.
9. Geotechnical engineers do take the heat for liability – they probably have the highest liability insurance premiums of all (for their level of remuneration).

The points above for consideration are typical of larger projects but should be viewed with the intention of including these in all reports. Of course, the more complex the geotechnical problems, the more the geotech should become involved.

Thanks for permitting me to take your time so I could put forth my views. Snaps to all comments to date.

 

[dik]

BigH...

I have a real problem with Item 3... it does not look so good, during discovery, if the contractor can show that he was not presented with all the information! Best he be given it and make his own decision.

Other than that, the comments are well received from this end.