The company that operates the steam system under Philadelphia streets will pay $18 million to a former University of Pennsylvania medical student who broke his back when he plunged 18 feet into an open manhole in 2004.

Minutes before Marcus Gustafsson, 30, fell into the hole at 19th and Walnut Streets, a homeless man had pried off the cover.

Gustafsson might have received more money if he had waited for a Common Pleas Court jury to rule in the lawsuit he had filed against Trigen-Philadelphia Energy Corp. After a three-week trial, the jury voted 12-0 yesterday to award him $85 million.

But to guarantee that he got something substantial to compensate him for his injuries, Gustafsson had agreed to what lawyers termed a high-low deal. Trigen pledged that, no matter what the jury verdict was, it would pay at least $1 million. Gustafsson, in turn, agreed to cap what he got at $18 million.

Matthew A. Casey, Gustafsson's attorney, said the deal prevented Trigen from appealing the verdict and assured that Gustafsson would be paid.

"This was an extremely unfortunate accident and we extend our sympathies to Mr. Gustafsson and his family," Trigen said in a statement.

Casey, of Ross, Feller, Casey LLP, said other companies Gustafsson sued had agreed to pay $4.9 million.

Gustafsson, a graduate of Germantown Friends School and Brown University, was working toward both a medical degree and a doctorate in molecular biology.

He has completed the biology degree but hasn't been able to finish his medical education because of difficulty standing for long periods during clinical work, Casey said.

The trial showed that Trigen had known for 10 years that homeless men were removing manhole covers, Casey said. It has welded some of them closed.

A Trigen statement said: "In accordance with city and federal regulations, Trigen specifically uses 250-pound snug-fitting manhole covers, which require specific tools to remove."

The jury said 99.99 percent of its $85 million verdict was was to be paid by Trigen and 0.01 percent by the homeless man, who has disappeared. That man's share: $8,500.