Ground ring required for reinforced concrete structure, which has NO electric?

[Dark Sparky]

We have a water reservoir, being constructed of reinforced concrete. It is approximately 400' x 200' in size. A subconsultant performed the electrical design.

No electrical equipment and no electric service is present at this structure.

The original design did not include grounding (ground rods) for the structure. The reservoir is now under construction. The subconsultant has had a change of electrical staff, and the new electrical engineer feels that grounding IS required. They are proposing a ground ring around the reservoir, bonded to the rebar in the concrete.

Based on the below comments - from another thread - I am uncertain if the grounding is required.

Does this structure require grounding? If so, please generally describe what is required.

Thank you.

Refer to this thread where the following statement was agreed upon:
"If the water pipe, the structural steel and/or the concrete encased electrodes are present, there is no need for ground rods to be installed.":
http://forums.mikeholt.com/showthre...?highlight=concrete+ground+without+electrical

 

[infinity]

If there is no electric present at the structure then what will you be grounding? If you're looking for lightning protection for the structure then that's a different question altogether.

 

[__dan]

If you have any type of electrical or electronic level controls for the resevoir, water level transmitters, I would ground and bond them to the rebar, to eliminate voltage potential differences between points from lightning strikes.

A ground ring external to the tank would seem to be an expensive redundancy. A ground ring in the concrete with the rebar would be great, only if it bonds to the metal parts of the level controls and level transmitters.

 

[bphgravity]

These projects typcially have extensive lightning protection / counterpoise grounding systems installed. I would consult with the PE to determine the intent and purpose of the grounding / bonding system. It likely is not an NEC related issue.

 

[masterinbama]

If this is a project you already have, price it as a change order and run all the way to the bank.

 

[Dark Sparky]

Responses

Responses

@infinity:
Correct - no electric exists at the structure. From others comments, it would seem then that we'd ground the concrete structure's rebar?
(Regarding lightning protection - no, that was not the intent.)


@_dan
Given that there is no (known to me) instrumentation, is a ground ring "in the concrete with the rebar" helpful? Perhaps to minimize voltage gradients, similar to in a pool like NEC 2008 680.26?


@bphgravity
We will ask the PE the purpose of the grounding/bonding system. Thank you for noting that it does not seem to be an NEC-related issue.


@masterinbama
Unfortunately you're right, if they choose to add grounding, it will likely be a costly change order.

I appreciate everyone's time in responding.

 

[petersonra]

I doubt you can get a better earth connection than the rebar in the concrete, but if someone wants to pay you to do more work, I would suggest being thankful for the gift you are about to receive.

 

[charlie b]

Keep in mind, guys, that the OP is an engineer. We don't get the big bucks on change orders of this type. We get to spend a couple hours, at most, revising a drawing. The ones who would get the big bucks are the supplier of the ground rods and accessories and the installer.