The Louisiana Department of Environmental Quality injected 25 gallons of red dye into the Pearl River at the International Paper wastewater treatment plant in Bogalusa Tuesday morning, and by just after 7 a.m. a noticeable stretch of scarlet was heading downstream.

The dye was used to mark a “slug” of the treated effluent, which LDEQ teams would sample and monitor as it made its way 32 miles downriver to Walkiah Bluff in Mississippi.

The testing is part of the response to the outflow problems that led to the fish kill last August, when the company was owned by Temple-Inland, according to David Greenwood, LDEQ environmental scientist manager.

“It is our job to make sure the waters of the state are OK,” he said. “We do not expect to find anything.”

Upgrades at the water treatment plant are continuing, and IP representatives welcomed the LDEQ team that dumped the dye into the “header box” that pushes the effluent into the river.

The marked slug of water is expected to take about 30 hours to get to Walkiah Bluff.