State environmental workers checking the dikes below Stroudsburg, Pa., last October first spotted the small black blobs in the rushing waters of Brodhead Creek. The cold, crystalline stream, famous in northeast Pennsylvania for its swarms of two-foot brown trout, was eating into a previous incarnation of the synthetic fuels industry.

The black blobs were coal tar, a syrupy goo that the Pennsylvania Department of Environmental Resources traced to a coal gasification plant that operated in Stroudsburg from the 1880s to about 1945. The Stroudsburg Gas Co. plant was one of hundreds nationwide that turned coal into gas for town street lights until the advent of cheap and hotter-burning natural gas.

This plant used an airless heating process called pyrolysis, which can leave up to 20 gallons of tarry wastes for each ton of coal it processes.

Dr. Joseph P. Lafornara, a chemist on the Environmental Protection Agency emergency response team, said the tar contains several known cancer-causing agents like benzene and naphthalene plus chemicals like toluene and xylene that are toxic to fish.

The EPA estimates that 8 million gallons of the stuff were dumped into unlined pits or lagoons on the banks of the Brodhead, right at the foot of Stroudsburg's main shopping area. A gravel vein runs through there, and the tar has seeped out to contaminate an underground area of six to eight acres, Donovan said.

The pits were covered over and forgotten until 1959, when the Army Corps of Engineers straightened and controlled the Brodhead, which has flooded in 1955 and killed 500 people. "We now think they redirected the creek over the top of the coal tar lagoons," says Joseph Donovan of the EPA.

The fast-flowing stream, 70 feet wide at that point, has eroded downward at about a foot a year. The tarry blobs, some as large as golf balls, percolated to the surface in natural springs that feed the Brodhead. "We know the pollutant is now only six inches below the bed in some places," Donovan said.

EPA has closed off the creek and has built earthworks and set booms and filters around the springs to catch the tar.

Stroudsburg gets its water upstream and while tests have found no sign of contamination so far, the Brodhead flows into the Deleware River three miles down and towns from Easton to Philadelphia that drink from the Delaware are worried.

Possible solutions may be to drill a well and pump the stuff out, use bacteria to decompose it, or build walls around it to contain it. It could be a $150 million disposal problem.