For the past couple of months, a group of University of Iowa students has been growing lettuce in an unconventional way.“I’ve known about hydroponics for a while,” said UI senior Grant Gregory, who works at the university’s office of sustainability. “There’s probably a market for it in Iowa City and Cedar Rapids and it is economically viable.”Gregory’s group — which also includes seniors Jake Krishel, Natalie Spetter, and Andrew Hirst and junior Cecelia Wolf — is using PVC pipes and the nutrient film technique to grow the lettuce in Biology Building East.“It uses about one-tenth or one-third of water as traditional lettuce,” Gregory said.