Crews seal poison pits along the San Jacinto River Two toxic paper mill waste sites contained, but a new dump found nearby

Crews have capped and sealed two pits of paper mill sludge that poisoned the San Jacinto River for decades, Harris County officials said Wednesday.

But as County Attorney Vince Ryan and others toured the Superfund site to promote the progress, they raised fears about a similar pit recently uncovered nearby.

Preliminary soil samples indicate that the 3- to 5-acre pit, which is located beneath a shipyard on the other side of the Interstate 10 bridge from the larger Superfund site, contains dioxins and other toxic chemicals. The federal Environmental Protection Agency says it's too early know if they are linked.

Still, the discovery means there may be more than one source of the San Jacinto's toxic stain, said Valmichael Leos, a project manager for the EPA.

"We're still looking for other sources," he said.

Meanwhile, the primary concern remains the cleanup of the two submerged waste pits, which the EPA placed on its Superfund roster of the nation's most polluted places in 2008.

A year of monitoring

In the first phase of the project, crews installed a polyethylene liner and poured 70,000 tons of rocks over it to prevent the further spread of the contamination. The cap is intended to withstand a 100-year storm event, said Randy Brown, an engineer with Anchor QEA, the firm working on the project.

The $10 million phase is scheduled to be complete by the end of July, followed by years of regular monitoring. Under federal law, McGinnes Industrial Maintenance Corp. and International Paper Co., as the companies responsible for the mess, must perform and pay for the cleanup.

"The No. 1 goal is to stop the bleeding of dioxins into the river," said Snehal Patel, chief of the environmental regulatory unit at the Harris County Attorney's Office.

The next step may be the removal of the contaminated soil. But the EPA, state and county officials will study whether digging up the muck will create new problems for the river before moving ahead.

If dredging isn't feasible, then the armor cap could be the permanent solution, Leos said. "But that's not the intent. It's not over after they place the cap."

McGinnes, which is no longer in business, owned and operated the pits in the 1960s, filling a 15-acre site on dry land with waste from a now-closed paper mill near the Washburn Tunnel.

In the bleaching process, paper mills generated large amounts of dioxins, a family of compounds so toxic that scientists measure them in trillionths of a gram. The EPA says there is no safe level of exposure to the chemicals, which are known to cause cancer and disrupt immune and reproductive systems.

'Safe to eat'

The San Jacinto began to run through the waste pits by the early 1970s because of subsidence — the sinking of soft soils as water is pumped from underground.

With the McGinnes pits under water, the dioxins spread into the river and worked their way through the ecosystem.

For more than a decade, the Texas Department of Health has warned that fish and crab caught along this stretch of water, north of the Lynchburg Ferry, are tainted with cancer-causing dioxins, pesticides and PCBs. No one should eat more than one 8-ounce meal a month.

"The goal is that within a short period of time the river will be cleaned up and it will be safe to eat fish again from these waters," Ryan said.

matthew.tresaugue@chron.com