NHI Qualified Team Leader: Who Is Legally Allowed to Sign Your Inspection
By Cheryl Ansel, DOT bridge program engineer, NHI-qualified team leader. Reviewed by Amanda McCallister, editor.
Underwater Bridge Inspection | Cathodic Protection & Anodes I remember my first call as a team leader. A consultant told me he'd just finished an underwater inspection on a 400-foot through-truss bridge. He asked me to send the signature block. I asked who was in the water. "Two commercial divers," he said. Neither had NHI training. I told him he had a dive log, not an inspection. We went back. That's how I learned how often people confuse 'commercial diver' with 'qualified team leader.' They're not the same. I've signed off on roughly 400 underwater inspections since then, and I've turned away plenty of well-meaning crews who simply weren't legal. This post is about who is legally allowed to sign an underwater bridge inspection—and why the NHI qualified team leader designation is the hinge that makes an inspection count.
The NHI Qualified Team Leader Is Not a Diving Card
The National Highway Institute (NHI) runs the course that the FHWA recognizes for underwater bridge inspection team leaders. It's a week-long class covering bridge mechanics, deterioration, inspection methods, and reporting. You learn to identify scour and undermining, and how to document section loss. You learn why an inspection isn't just 'looking around.' The legal basis is 23 CFR 650.309, not 650.311. That section says inspection personnel must be qualified. For underwater work, the team leader must have successfully completed the NHI underwater bridge inspection training. That's the legal minimum. It doesn't say 'or equivalent.' It doesn't say 'commercial diver.' It says NHI. So an ADCI commercial diver without NHI training can be in the water, but he can't sign the report. And he works under a team leader who is qualified. That team leader has to be directly involved. The person who signs the report should be on site, or at least directing the work. I've seen pre-signed blank reports. Not legal, and not safe.
Where It Applies: Bridges, Not Boats or Tanks
Once you hold NHI training, it's tempting to think you're the go-to for every underwater inspection. You're not. The NHI qualification applies to highway bridges under the National Bridge Inspection Standards. It doesn't cover Coast Guard underwater inspections in lieu of drydocking. Those are under 46 CFR Part 71 for passenger vessels, with approval in 71.50-5. Towing vessels fall under Subchapter M. Different standards, different rules. Potable water tanks? Another world. AWWA M42 recommends inspection at least every three years, but state rules govern. Texas requires annual inspection per 30 TAC 290.46(m)(1). Your NHI card transfers to none of this. Liability follows your signature. If you sign for a water tank without proper state qualification, you've exposed yourself and your firm. Always check the owning agency's requirements.
The 60-Month Baseline Myth (and the 72-Month Reality)
The most common misconception I run into is that underwater inspections are every 60 months, no exceptions. In reality, 23 CFR 650.311(b) sets a baseline of 60 months, but paragraph (b)(1)(iii)(A) and (b)(2) allow a 72-month interval if the bridge meets stated conditions—like a history of satisfactory inspections and no susceptibility to scour. It's in the regulation, not an informal FHWA allowance. Same for routine above-water inspections: baseline 24 months, but 48 and 72 are permitted with justification. If you're stretching an interval, you need a written rationale that stays with the inspection file. When I teach, I say: 'If you can't defend it in writing, you can't do it.' And making that call requires a qualified team leader. It's judgment, not a checklist.
The Hardest Lesson: Delta P and Why I Sweat the Details
One thing the NHI course doesn't spend enough time on is the physics of low-head differential pressure. I've seen dive contractors who plan to 'stay clear of the intake.' That's not how it works. The lethal mechanism isn't velocity. It's static head. Once a diver's body seals an opening, the full differential head acts across that area. Static pressure is roughly 0.433 psi per foot of head. A 10-foot differential is about 4.3 psi across whatever is sealed—over a human torso, that's thousands of pounds of force. Flowing water at 10 ft/s is about 0.67 psi dynamic pressure. Dynamic pressure is not the hazard. Plugging is. So I plan every inspection with lockout/tagout, even on small culverts. And I trust a team leader who can explain the difference. If someone says 'we'll just be careful,' that's a red flag. The only safe control is positive isolation and verification, not caution. Why talk about delta P in an article about signing inspections? Because the person who signs is the person who plans. If you don't understand the physical hazard, you can't direct the work safely. The NHI qualification is the bare minimum for that trust. Get the training. If you're hiring, check the certificate. Call it a signature, but it's a judgment.
Frequently Asked Questions
Can a commercial diver sign an underwater bridge inspection without NHI training? No. 23 CFR 650.309 requires a team leader who has completed NHI underwater bridge inspection training. Commercial diver certification is not a substitute; recreational certifications like PADI or NAUI never count. Is a 72-month underwater inspection interval allowed? Yes, under 23 CFR 650.311(b)(1)(iii)(A) and (b)(2), if the bridge meets stated conditions. The baseline is 60 months, but 72 is a permitted interval when documented. It's not an informal allowance. Does an NHI team leader qualification apply to UWILD for vessels? No. It's specific to highway bridge inspections. Coast Guard underwater surveys are governed by 46 CFR Part 71 (passenger) or Subchapter M (towing), with separate approval criteria. How do I verify a candidate's NHI qualification? Ask for their NHI course completion certificate. Also check your state's bridge inspection manual—many states require additional documented experience beyond the course. Then verify with your state program.