Lumps in yard and lots of worms!?

anyone know what chemical is used to bring worms to the surface for collecting. I have a million lumps in my yard and lots of worms. I met a man who noticed the lumps and told me i had to get rid of the worms because they would cause hepatitis... It scared me so that day he came over with his 6 boys and put a chemical that he mixed in a huge barrel. he dumped the barrel on the lawn and then waited for like 30 seconds. a ton of worms crawled up for air i guess and the boys collected the worms. He eventually sold them for cash to bait shops...and didn't even pay me a nickel. he wants more worms from my yard but won't share his fortune..my fortune. he also will not share the name of the product that he used to un earth them. i found out he was selling the worms and telling ppl in my area the same lie. the truth is he collects worms, puts them in foam cups and sells them to fishermen. the worms he collected from me may have filled about 100 foam cups. anyone have any idea about what chemical i can use? sure would love to make a few bucks for my family. thanks guys.