Yes you could drill another hole through that. You would use a regular hole saw.

What material is the countertops? If its laminate then easy, if its granite then you would need a different hole saw.

Sometimes they have the indents for the other holes on the underside of the sink.

Thanks guys for the responses. I have done some more checking, and it looks like there may be 'prearranged' knockout holes on the decking. Wish it was really clear on the description. I ordered it online from Home Depot, so perhaps my local store would know the answer.

Since I live 1000 miles away from my son, it is hard to try and organize this all for him. I can do the online searches and order online, but since I'm not dealing with his restoration company I just want to keep everything as simple as possible, and not leave room for error.

There will be laminate countertops going in. But the holes would be knocked out/drilled BEFORE installation. I just need to confirm that there are the knockout holes on this sink. Wouldn't it be great if HD and or Blanco made that crystal clear?

Yes, I believe there are knockouts on the underside, (drilled partially through) ...either way, Silgranite can be drilled, so you should be good to go.

There were many other knockouts on the underside of the single bowl Silgranite sink I got from Home Depot. They had stickers on them underneath explaing what they were and how to tap them out.

You just need a carbide hole saw and not go too fast.

Carbide hole saws are not easy to find, but I agree that's the ticket.

Sometimes the home centers in large cities carry them though.

Thanks for the help! I just spoke to Blanco Customer Service. There are four additional knockouts for accessories. However, it took half a day, lots of internet searching, a couple of phone calls, one to HD and one to Blanco to find this out. I wouldn't even have known to look for the additional knockouts if you GWebbers hadn't led me in that direction! When I kindly suggested to Blanco that they add this on to the description and make it clear to future potential customers that these knockouts are an option, well, she was let's say 'less than grateful'.."ma'am we have that information on our website". Well, perhaps not every customer wants to go back to the manufacturer's website to try and find that out (model numbers are different from what is stated on the HD site, and in fact she gave me the wrong model number at first...)

Anyhow, now I know, I thought I was doing Blanco a service letting them know it was not that clear, and it could be helpful to add that to the HD description..." Ma'am that is HD's description" Oh well, you can lead them to water....

Bought a Blanco Lexa SK sink. Had two pre drilled cutouts that are visible between the double sinks but none in the drain board to allow filtered drinking water dispenser installation. This sink does not have any additional pre drilled holes and Blanco customer service just advised me i void warranty if we drill one. DUD!

A 1 3/8" diamond dry bit on an angle grinder will drill your hole without ruining the sink in half a minute.