If, while driving along Route 248 near Palmerton on the afternoon of Sunday, April 14, you may have seen fire and smoke emanating from the west side of the Lehigh River, perhaps you thought that might be signs of a forest fire.

It was a forest fire - but a special type of controlled forest fire called a prescribed fire.

It seems that back in 2004, Dan Kunkle and the folks that would later develop the Lehigh Gap Nature Center, had an idea on how to re-vegetate a portion of the Blue Mountain on the west side of the Lehigh River that was contaminated with zinc, cadmium and lead from the smelting operations of the former New Jersey Zinc plant.

They experimented with planting warm season grasses on the Superfund site, and now, nearly a decade later, their experiment has proven successful - and to some extent, too successful.

"Every year the tops of the grasses die back and form an organic layer on top of the existing soil," Kunkle explained. "This layer is pretty much free of metals because these grasses do not take up much of the metals."

"Now birch trees and butterfly bushes coming in, and they take up the metals big-time," he continued. "and when their leaves fall, they drop into that organic layer."

"Our main reason for the burning is to kill the birch and the butterfly bushes, and leave the grasses and not have the woody things that take up the metals and cause problems."

Kunkle explained that caterpillars eat leaves from those trees and the metals can be ingested by birds and so on. He noted that hunters who ate the livers of deer that fed on this vegetation could ingest an elevated level of metals.

"We are trying to make sure that the metals stay where they belong in the ground as the EPA has asked us to do. That's part of what this fire, we hope, will do," he said before the test began. "We don't know what will happen."

"The metals are located in the top 4 to 6 inches of the existing soil. We are building topsoil on top of that. The grasses go down many feet. The grasses also just preferentially exclude metals and no one knows why."

"The birches are pioneer species and grow in poor soils - even on the culm banks in the coal regions. They are very good at getting moisture and nutrients out of the soil. Their root systems are shallow and they are taking up a lot of the metals."

The fire is not intended to immediately kill the birch trees. Instead, the fire is expected to burn the thin outer bark of the birch tree, and cause its sap to boil. "That's the plan," Kunkle said. "We will see if it happens."

The experimental prescribed burn was planned for 10 acres, with an advanced test firing to create a blackened area on the downwind side of the site - a location bounded by a trail which served as a firebreak.

The experimental prescribed burn was monitored by the EPA, DEP, the U.S. Forest Service, and Tom Whitlow, a professor who teaches Restoration Ecology at Cornell University.

"I have been bringing my class here for about five years," explained Whitlow. "A year ago last fall, when Dan Kunkle said that they were going to do a test burn, I thought that it might be a good opportunity, given the unique nature of this place - a Superfund site - no one is ever doing a controlled burn on a Superfund site."

"The particular suite of circumstances made it ideal to monitor the burn. So, I contacted John Hom, a fire ecologist with the Forest Service and he arranged for monitoring equipment to be provided."

Whitlow and Hom erected three mast-mounted sampling instruments and several tripod-mounted particle samplers to monitor the quantity of particles and types of metals discharged into the air during the burn. The particle counters use a laser to measure the size and number of particles sampled by the instrument. The sampling instrument filtered the smoke, and after the test, the filters were removed and sent to a laboratory so that their metal's content could be measured.

The experimental burn was supervised by Shannon Henry, the "burn boss" for Silvix Forestry and Prescribed Fire. He oversaw a crew of about 20 including: those lighting the fire, firefighters from the Department of Forestry, volunteer firefighters from local departments, and researchers.

"We are conducting a prescribed fire on about 10 acres, basically for research," Henry explained. "They want to see what emissions would be in the smoke from the site. One of the main objectives is to produce smoke so that they can monitor what is in it. Other objectives are to control the birch that is coming into the area and continue to propagate the warm seasons grasses that are growing here."

"We begin with a test burn down in the downwind end of the unit. If the fire behavior looks like what we are going for, then we will 'black line' - which is basically lighting the downwind side of the site and let the fire back into it to get a nice solid black and easy to defend line."

"While it's happening and when it's finished, we will monitor it, and then we will go in and do what is called 'mop up' - which means going through and putting out any hot spots and making sure it is safe to leave when the time comes."

"We use drip torches to start the fire. It is a backpack that carries a two gallon mixture of diesel and gas fuel in a tank that has a special wand on it. The wick is lit, and when you tip it down, it drips the fuel out and catches fire."

Henry has bossed between 150 and 200 burns. "Our prescription allows us to go up to 20 mph wind speed. The highest that I've seen is one gust at 15 mph, but it's generally been in the range of 10 to 12 mph. We will just go slow and take our time." It had rained two days earlier, so the ground was moist which helped keep the fire under control.

Also at the burn was Jennifer Lansing, an environmental consultant with Arcadis, representing CBS - one of the settling defendants at the Superfund site.

On the east side of the Lehigh River, Lansing is involved with an alternative approach to re-vegetating the Blue Mountain. "This spring, on the other side of the Lehigh Gap, we are planting in fenced enclosures to restore woody trees and shrubs on National Park Service property."

"We are replanting about 7,000 trees in the next two weeks. A variety of oak species and American Chestnut - we are working with the American Chestnut Foundation. We are trying to reestablish woody trees and shrubs." Oaks and chestnuts tend not to draw metals from the ground.

"The burn went real well," Kunkle concluded. "Now we will be monitoring to find out how effective it was."