Authorities hope new soil and groundwater tests will show whether the flammable chemical that exploded Saturday under downtown streets leaked into city storm drains from the Howard Street Tunnel, site of last month's train derailment and fire.
City officials think some tripropylene entered a separate pipe network - the sanitary sewer system - after the July 18 wreck. The next day, fumes identified as the chemical were reported at the Eastern Avenue pumping station on President Street, more than a dozen blocks away.
The chemical's apparent migration was not reported at the time. But the odor forced the adjacent Baltimore Public Works Museum to close for several days and briefly sickened one employee, assistant curator Vince Pompa said yesterday.
"At that time no one knew what it was, but it certainly wasn't the regular smell we experience here," he said, recalling a "tremendous odor" similar to gasoline or paint thinner. "You had to leave and get some fresh air."
Public works engineers have found no drain linking the tunnel to the sewer system, but a 22-inch sewer line does flow west to east under the tunnel at Pratt Street toward the pumping station. Today, the Department of Public Works plans to send a camera into the aged pipe to look for breaks that might have admitted the chemical.
The tripropylene, the vapor of which exploded under Pratt and Light streets Saturday, is thought to have lingered in storm drains for some time and possibly was pushed to the intersection by Friday's heavy rain. CSX Corp. says the tunnel connects to storm drains, though city maps don't show the link. Nor do city plats show a culvert that CSX says lies beneath the tunnel's rail bed.
One possibility being explored, city officials say, is that the chemical found a way into a storm drain that crosses underneath the tunnel at Camden Street - several blocks south of the sewer line - and flows to the Inner Harbor. How the chemical could have gotten in the drain is not known.
"That is still very much an unanswered question," said Jerry Young, chief of training and safety for public works.
The quest for answers has bogged down amid apparent contradictions. For example, while a punctured tanker railcar containing about 18,000 gallons of tripropylene might have been the source of a leak, soil samples in the tunnel showed no trace of it. That led to speculation that the chemical burned off in the five-day fire.
To help solve the mystery, CSX officials said yesterday the company would have two monitoring wells drilled near Howard and Lombard streets, alongside the portion of the tunnel where the tanker car derailed. The wells, 5 to 7 inches in diameter, would be drilled 30 to 40 feet to at least the base of the tunnel, they said.
"It will answer the questions of what happened to the material: How much was spilled? How did it get there?" said Richard J. McIntire, spokesman for the Maryland Department of Environment.
CSX spokesman Robert L. Gould said there is no "definitive information" to say the tunnel was involved.
Public works spokesman Kurt L. Kocher said it would be "a heck of a coincidence" if the tripropylene were to be traced to a manufacturer in the city that dumped it in the drain system.
The Department of the Environment had planned to use a fluorescent dye to determine how the city's antiquated network of pipes are integrated and function. But McIntire that plan has been scrapped because it "would have been too complicated" to replicate the tunnel fire scenario.
The agency hopes the soil and water tests yield valuable clues. They will take two weeks to conduct and two more weeks to analyze, he said.
Also yesterday, McIntire said crews removed 2,200 gallons of tripropylene from beneath Pratt and Light streets after explosions in two vaults housing cables and wiring shot a manhole cover four feet in the air. He said the amount was revised upward from an initial estimate of 1,000 gallons.
The fumes at the pumping station were unpleasant, Pompa said, adding that a museum employee felt ill and complained that "it was very bothersome."
About a week later, tests confirmed the substance was tripropylene, said Young, the public works safety officer. He said monitors never indicated risk of an explosion at the station, which can process 180 million gallons of sewage daily.