underground steel piping - Compacting of soil using seawater

[Eduardo1982]

Dear guys. I would like to know if someone has any idea (if there is any specification or code) that mentions about the use of sea water for compacting soil above underground Steel pipelines. Although this steel pipeline will have a PE coating, I think that high percentage of chlorides that sea water contains will attack directly the weak zones of touch-up. any advice or opinion?
Thanks in advance!!

 

[zdas04]

I'm not sure where you are at, but you could never get a permit to do this in the U.S. The problem is that the TDS of sea water is so high that nothing would grow where you put it down. Enviro departments require re-vegetation.

David Simpson, PE
MuleShoe Engineering

In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. Galileo Galilei, Italian Physicist

 

[cvg]

this has been studied in the past and may result in improvement in atterberg limits, compaction characteristics and unconfined compression strength. given that your project is apparently in close proximity to the ocean, the native soil may already have increased levels of salts. You should quantify the amount of added salt to determine what the effect might be. Given that a relatively small amount of water is necessary to obtain optimum moisture content, the amount of added salt may not be that much.

as far as re-vegetation is concerned, topsoil should be stripped and then replaced with minimal compaction. I would not see a need to add water to compact topsoil.

http://www.eijst.org.uk/images/frontImages/gallery/Vol._3_No._2/2.pdf

 

[zdas04]

I've tried to do it with produced water (around 10,000 mg/L TDS) and been denied a discharge permit. Sea water tends to be 350,000 mg/L TDS.

David Simpson, PE
MuleShoe Engineering

In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. Galileo Galilei, Italian Physicist

 

[bimr]

Many are of the opinion that road salts cause corrosion in buried ductile iron water mains.

However, the Welded Steel Pipe Design Manual does not mention sea water.

http://www.google.com/url?sa=t&rct=...cd=1&cad=rja&uact=8&ved=0CB4QFjAA&url=http://

http://www.steeltank.com/Portals/0/...=VQm2rxeb8D9nySZyj-QHCg&bvm=bv.86475890,d.aWw

 

[Eduardo1982]

ummm.. I also was checking some books and codes of reference and I did not find nothing concrete yet.

 

[BigInch]

Ignoring general environmental implications of salts, and in the context of piping alone, this is not a problem for PE coated pipe when the coating has been well applied, holiday tested just before installation and any pinholes in the coating repaired according to the coating manufacturer's recommendations. There should not be any undiscovered "weak zones" remaining after adequate inspection and coating repairs have been made, but if there are...

Cathodic protection would also normally be provided to the pipe to counter the affects of any undetected pinholes or those that might develop in future.

NACE SP0169 covers the design of cathodic protection systems for pipelines.
Free Copy is provided by NACE here,

http://www.nace.org/uploadedFiles/Corrosion_Central/Industries/SP016907PHMSA.pdf

 

[rconner]

When you say "sea water for compacting soil", was curious are you talking about some scheme of flooding or jetting etc. to try to somehow settle soil below and around pipe, or instead is the plan to add just enough water to achieve optimum moisture content in terms of a laboratory density curve etc?