Duct Bank Cover Depth

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Table 300.50 Minimum cover requirements, 13KV installation, in concrete encased PVC.

We have an existing duct bank we are crossing over, getting close to the surface, assume it is 20' wide.

1. For column 4, under a 4" concrete slab, the cover requirement is 4". I'm assuming this is 4" from the surface, so the conduit could be directly below the slab. Is that correct?

2. In general note 2, it says if solid rock prevents compliance, to use 2" of concrete extending down to rock. Can the existing duct bank be considered "solid rock" so we would be able to use the 2" of concrete, extending down to the existing duct bank, only over that area?
 

petersonra

Senior Member
Location
Northern illinois
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engineer
Table 300.50 Minimum cover requirements, 13KV installation, in concrete encased PVC.

We have an existing duct bank we are crossing over, getting close to the surface, assume it is 20' wide.

1. For column 4, under a 4" concrete slab, the cover requirement is 4". I'm assuming this is 4" from the surface, so the conduit could be directly below the slab. Is that correct?

Not my area of expertise but look at the definition of "cover" in note a.
2. In general note 2, it says if solid rock prevents compliance, to use 2" of concrete extending down to rock. Can the existing duct bank be considered "solid rock" so we would be able to use the 2" of concrete, extending down to the existing duct bank, only over that area?
I don't see how you can claim a duct bank is rock.
 
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