Burial Depth: Spec, Submittal, and RFI
From Division 26, Section 26 05 33, paragraph 2.4: 'Direct-buried raceways beneath vehicle drive aisles shall have a minimum cover of 24 inches measured from the top of the raceway to finished grade.' From the approved submittal for the PVC conduit being supplied: 'Installation guide - minimum cover: 30 inches beneath driveways and parking areas; 18 inches where a 4-inch concrete slab is installed directly above the raceway.' From Division 01, Section 01 33 00, paragraph 1.3: 'Where the contract documents and an approved submittal differ, the more restrictive requirement governs. Substitutions require an approved RFI.' From RFI-22, answered 3 March: 'The concrete cap over the north drive aisle has been deleted by value engineering. No slab will be placed over the conduit in that area.'
The crew has installed the north drive conduit at 24 inches of cover and asks you to sign the inspection card before backfill.
1. Is the installed work acceptable? Which document controls, and why?
Read the worked answer
Not acceptable. The installed depth is 24 inches, but the controlling requirement is 30 inches.
Chain of reasoning: the specification says 24 inches. The approved submittal says 30 inches generally, with an 18-inch allowance only where a 4-inch concrete slab sits directly above the raceway. Section 01 33 00 says that when the contract documents and an approved submittal differ, the more restrictive requirement governs. Compare the two applicable numbers: 30 is more restrictive than 24, so 30 controls.
The consequence is that 24 inches complies with the specification but violates the submittal, and the general requirements resolve that conflict against the lower number. The work is 6 inches shallow and must be corrected before backfill.
2. What would the crew have needed in order to install at 18 inches?
Read the worked answer
Two conditions, both from the submittal text: the conduit would have to be beneath a location where a 4-inch concrete slab is installed directly above the raceway, and that arrangement would still have to survive Section 01 33 00's more-restrictive test against the spec's 24 inches.
RFI-22 closes the first door: the concrete cap over the north drive was value-engineered out and no slab will be placed there, so the 18-inch allowance is unavailable on this alignment regardless of anything else. The RFI also shows why the submittal footnote cannot be read in isolation - it was written for a design that no longer exists. A crew that saw '18 inches' in the submittal and stopped reading would have installed 6 inches shallower than the spec minimum as well as 12 inches shallower than the controlling requirement.
3. The foreman argues that the conduit is already in and buried is buried. What is the defensible action, and what record should exist?
Read the worked answer
Do not sign the card. The deficiency is documented and known, which makes signing a false verification rather than an oversight. The defensible action is to stop backfill, notify the superintendent and the general contractor in writing, and process the correction through the same channel that created the conflict: an RFI asking whether the north drive may be accepted at 24 inches, or a directive to re-excavate.
A substitution back to 24 inches is possible in principle, but Section 01 33 00 requires an approved RFI for it - the field crew cannot waive a submittal requirement by deciding the difference is small. The record should include the RFI-22 answer, the 01 33 00 clause, the measured depth, photographs before backfill, and the resolution letter. If the work is covered first, the record becomes an argument about what the depth used to be.