How much ground work is there in Jujutsu?

Jujutsu encompasses hundreds of styles as an art. The focus of what is taught can be highly dependent on the instructor, instructor's knowledge, and style. Jujutsu is different from BJJ, in that BJJ is a sporting application derived from judo. While it does have some practical self-defense, many of the positions you have to put yourself in with BJJ can get you killed by an attacker's friend by going to the ground, or leaving a part of your body exposed.

I believe what you're referring to is the type of Jujutsu native to Japan which was brought to Hawaii such as the kind practiced by Prof. Wally Jay and George Kirby. There is a lot of ground work in Japanese and Hawaiian systems, but Brazilian Jiu Jitsu makes ground fighting (ne waza) the basis and the strength of their fighting system, unlike Japanese and Hawaiian jujutsu systems.

The same way that Aikido has some similarities with Judo because it comes from the same Samurai source, so too does Brazilian Jiu Jitsu have similarities from is parent and cousin systems found in Japan and Hawaii.

yes ground work is invovled