300.5(F) Backfill

[infinity]

Had an inspector tell me that he requires conduits and direct burial cables to be placed on a bed of sand due to 300.5(F). His argument is that you would not know if the fill (regular old dirt removed from the trench) is corrosive. Has anyone ever heard of such a thing?

300.5(F) Backfill. Backfill that contains large rocks, paving materials, cinders, large or sharply angular substances, or corrosive material shall not be placed in an excavation where materials may damage raceways, cables, or other substructures or prevent adequate compaction of fill or contribute to corrosion of raceways, cables, or other substructures.
Where necessary to prevent physical damage to the raceway or cable, protection shall be provided in the form of granular or selected material, suitable running boards, suitable sleeves, or other approved means.

 

[RobbieR]

Never heard of this. And I think he is misinterpreting the Code (Imagine that!)

From what I understand, the Code is saying not to bury conduit with corrosive MATERIAL (ie, rebar, scrap metal, etc). It says nothing about corrosive SOIL. Furthermore, PVC conduit and direct burial cable doesn't corrode. At least I have never seen it.

 

[Cow]

I think some inspectors get bored and cook up new ways to interpret the code and turn you down....

Corrosive dirt, NOW THAT'S FUNNY!

 

[RICK NAPIER]

I have never heard of such an interpretation.

 

[infinity]

I kind of thought that he was kidding but he then stated he would accept regular fill if the soil had been tested to prove that the dirt was not corrosive to the conduit or cables. He's not kidding. I could see this type of requirement if the conduit was being run though an old toxic waste dump but in normal terra firma I think that he's reaching a little far.

 

[don_resqcapt19]

Putting clean sand around won't really do anything for corrosive conditions. The corrosive material in the soil will soon leach into the sand. The sand is really to provide physicall protection and is often required by the job specs.

 

[renosteinke]

Sometimes is matters just what the run is for ....

As an example, if I'm running service wires, I need to meet the PoCo specs ... and the PoCo requires a particular type of sand (decomposed granite, gray in color) around the pipe. Unlike 'regular' sand, this "PoCo sand" doesn't compact, and is a different color than the surrounding soil.

I can't speak to your local conditions, but there is merit in using sand to prevent even small rocks from directly pressing on the pipe. I have also seen soils that never seem to completely fill the ditch they just came out of, so adding some sand can help the trench 'disappear' later.

 

[elohr46]

Had an inspector tell me that he requires conduits and direct burial cables to be placed on a bed of sand due to 300.5(F). His argument is that you would not know if the fill (regular old dirt removed from the trench) is corrosive. Has anyone ever heard of such a thing?

I ran into this situation one time about 25 years ago. There's an area in NW Philadelphia called Cheltenham, the soil where the job was located was so corrosive the specs called for all underground conduit to be PVC coated RC. The soil was mixed in with some type of mica material, haven't seen or heard of it anywhere else.