Depends where you are. Each pilot association sets there own requirements for a pilot to board.
In theory, the associations have no direct/absolute say on state pilotage requirements. State Pilotage Authorities (usually a board of commissioners, overseen by the state legislature and/or governor) are the ones who decide that. Certainly on paper, that’s how it’s supposed to work. Different stakeholders (pilots, shipping associations, etc) all get their two cents in…
In 46 CFR § 15.812 they reference the barge and the tug as separate vessels and I couldn’t find anything governed by “combined” tonnage save for sea service accrual.
It’s all in 46 CFR 15.812, as you’ve already found. Federal pilotage requirements are the same for all U.S. ports. U.S.-flag vessels meeting certain tonnages (depending on type) under coastwise endorsements and on domestic voyages only require a Federally-licensed Pilot. States are specifically prohibited from imposing further restrictions to vessels that meet these criteria.
The only exception to this is Prince William Sound. There, the pilot must be someone who is not part of the crew and is an Alaska state-licensed pilot even if only piloting a U.S. flag vessel on a domestic voyage. This was put into place as part of OPA '90, supposedly to further protect PWS.
This unit is an ATB, our tank barge is 9787 Gross Tons and the tug is SOLAS at 197 GRT and 682 ITC. Is this true that the “combined” tonnage is the deciding factor?
I don’t see anything that takes into consideration the tonnage of the towing vessel. I’m also not aware of any case law that’s challenged this. If your gross tonnage is only 9787 (and in this context, GRT vs. ITC is irrelevant) then the requirement for a Federal Pilot does not apply and no state can impose any other pilotage requirement on you. The requirements for the person “acting as pilot” to have “recency” do apply though. Keep in mind that it’s not simply just the route requirements, but the annual medical exam is also needed (that’s the Pilot Expiration date on your med cert).
That all being said… lots of terminals (mostly oil ones) require that vessels over a certain size utilize the services of the local pilot group, regardless of the legal requirements. The oil major’s chartering groups tend to require them anyways and since they’re paying the bills, there’s really no skin off the Master’s back to use one. Most (probably close to all) State pilots are also Federal Pilots so the service (other than in ports where there are separate Federal groups) is the same regardless.