When is Geotech Report not reliable anymore (how many years)? 3

[delagina]

Is there a rule of thumb if geotech report is 10 yrs old or whatever, it's not reliable anymore?
Assuming no fill is added or any other soil modification.

 

[CANPRO]

Depends on the nature of the site and what you’re using the report for. If the site/soil/structure is sensitive to groundwater levels/changes you might want to consider getting an updated report.

 

[MIStructE_IRE]

Not sure of a hard n fast rule..but 10 years would be enough for me to want a new report. Groundwater etc..

 

[cvg]

I've used boring logs and geologic profiles that were 50 years old. the data was still useful

 

[Agent666]

You can get logs re-interpreted like cvg notes if their investigation proximity to your building location is applicable.

You are also possibly carrying the risk if original company isn't round any more and you use their report and something goes wrong. Likewise that company wouldn't want to be dragged into it if something went wrong as they had no involvement in the project but you applied their recommendations to another project. Best to get client to accept the risk here, otherwise insist on a specific report for a specific project.

I'd certainly feel ok with using the old report to get a head start on design and assumptions around foundations, etc.

 

[oldestguy]

The two above said it well.

 

[JStephen]

I'm thinking the reports I see often have a blurb in there to the effect that if construction is delayed excessively, the report should be reviewed and/or updated- anyway, just check with the geotech to confirm. If they're dead or out of business or whatever, that sort of answers the question anyway.

 

[msquared48]

Some Geotech reports are more conservative than others, just like other engineering reports.

If you have any doubt in your guts about the original report, get another opinion.

It's only money!

Mike McCann, PE, SE (WA)

 

[GeoEnvGuy]

I think most geotechnical reports have the disclaimer that they drilled the holes in specific spots at the time of investigation for the intended owner and project.

If nothing changed the conditions should be the same, except for the variable seasonal groundwater conditions. If your not working for the owner or on the project referenced you probably won't be able to have any legal reliance on the report. Also if you are relying on really old reports some sections can be out of date and are no longer relevant.

 

[canwesteng]

I've used old geotech reports, probably wouldn't think twice about using a 10 year old report, at least for deep foundations. Assuming of course it's for the site and not adjacent.

 

[JAE]

For me, if the original geotechnical engineer is in jail, has left the country, or is selling life insurance, I will get a new report.

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[BridgeSmith]

I'd agree with Agent666 on having the report updated. If the report is out-of-date, the soil conditions may not have changed, but the design parameters (load and/or resistance factors) probably have. Possibly, further research may also have changed how some materials are evaluated.