Aerial Hydromulching Helping to Prevent Erosion in Areas Ravaged by Wildfires

      Even after the recent wildfires that have decimated Southern California hillsides have been brought under control, residents and officials still face another major challenge: dealing with soil erosion when the winter rains begin.

      After the devastating Jesusita fire in May in Santa Barbara County — which burned more than 8,700 acres and destroyed 80 homes and damaged 15 others — hillsides were denuded. The fire was the third within the year in the hills above Santa Barbara, Montecito and Goleta on California’s central coast.

      “The Jesusita burn area has no vegetative cover now,” notes Matt Griffin, a civil engineer with the Santa Barbara County Department of Public Works.

Like they did after the 2008 Gap fire, which charred more than 9,400 acres, Santa Barbara County officials are turning to hydromulching to prevent erosion of the hillsides. It will also help trap moisture to help the seeds in the ground re-establish themselves.

“Basically it’s going to act as a protective cover,” Griffin explains. “It’s not going to prevent erosion by any means, but it will reduce some erosion of the hillside.”

The wildfires have been fought from the air using fixed-wing aircraft and helicopters and a similar aerial assault is being employed in the hydromulching effort. That effort began in mid-September under a multimillion dollar contract with Western States Reclamation, Inc., of Frederick, Colo.

Western States employed Aero Tech of Clovis, N.M., to fly five fixed-wing aircraft for the 22-consecutive-day project, and WildLands, Inc., of Richland, Wash., to assist in the mixing of the hydromulch.

All three companies have worked together in the past on fire projects.

“There are three or four companies that we team up with on a lot of projects,” says Colby Reid of Western States. “We usually try to work together to get the projects done in a timely fashion. Usually time is of the essence.”

Some 1,000 acres of private and non-federal public lands  were expected to be treated with the hydromulch, a mixture of paper and wood fiber combined with a binding agent. No seeds or fertilizer were included in the mixture, as they would be in hydroseeding, although the two terms are often used interchangeably.

A contract for applying hydromulch to another 230 acres of U.S. Forest Service land charred in the Jesusita fire is expected to be awarded.

The hydromulch being applied this year will contain no contaminants, such as plastic from recycled newspapers. The use of such materials a year ago in areas burned by the Gap fire prompted complaints from some concerned residents.

“The last time it was done the Forest Service specification called out for recycled material,” Griffin notes. “That specification allowed for a very small portion of plastics and whatnot that can be produced as part of recycled material . . . but it’s a very small percentage. That was a community concern. For this fire, we’re specifying 100 percent plastic-free product.”

Reid, reclamation division manager for Western States, which handled last year’s project and also is heading up the current effort, says concern about plastics in the mulch were unfounded.

“The paper is recycled material, so when people recycle their newspapers they don’t always take the plastic sleeve off their paper, and that was the plastic that was of concern last year,” he explains. “The U.S. Fish and Wildlife Service and the U.S. Forest Service did surveys and found there wasn’t enough out there to be of concern.

“Just to make everybody at ease, we’re using a different paper source this year, where the paper has never been distributed to the public,” he says. “It’s still recycled. It’s just left over paper that has never been circulated. It doesn’t have the garbage that people recycle with their paper.”

Results of the 13-day hydromulch effort last year on areas burned in the Gap fire were difficult to ascertain due to the fact that little rain fell during the winter months, Griffin says. Some 3.5 million gallons of hydromulch were dropped on the burn area by six planes and one helicopter.

“Last year was such a dry rain year that it’s not a good indicator of how effective hydromulching was because we saw very little soil erosion in both the hydromulched areas and the non-hydromulched areas,” he says.

This year, he adds, “We don’t know what the rainy season is going to be like.”

Even so, local officials didn’t want to take any chances that winter rains will cause mudslides, creating more havoc and misery for residents who are still trying to recover from the blaze.

The aerial hydromulching “is just for erosion control purposes, just to hold the soil through the rainy season,” Reid says.

Western States Reclamation has been providing aerial hydromulching services since 2000 and Reid says such efforts have proven highly effective. The company was started in 1983 and primarily provides ground reclamation services for areas such as mines, pipelines and other lands used by the energy industry.

The first aerial hydromulching project undertaken by Western States, as well as by Aero Tech, came after a 2000 fire in Los Alamos, N.M. That blaze blackened 48,000 acres, destroyed 400 homes and destroyed and damaged structures at the Los Alamos National Laboratory. 

The hydromulch consists of a blend of 60 percent wood — aspen and pine — 40 percent paper and an organic tackifier to hold it on the hillsides. The mulch and paper were supplied by outside companies in 50 pound bags, then mixed in a water solution in Western States’ hydromixing trucks which have 3,300 gallon or 4,000 gallon capacity tanks. From the trucks, it is pumped into the aircraft.

“The dry material goes in, the water goes in and the slurry comes out,” Reid says, adding that the process, which includes dumping the bags into the mixer, is extremely labor intensive.

Each plane can hold 800 gallons and applies about 3,000 gallons — one ton of dry material — per acre. The planes were expected to have about a 12-minute turnaround, essentially the time it takes them to load, fly and drop the hydromulch and return to the Santa Barbara Airport. Each plane will do approximately 45 drops per day.

Aircraft made 3,238 flights last year when hydromulching the Gap fire area, according to the U.S. Forest Service.

Reid says because of noise concerns for homeowners, helicopters were not being used this time around. They were used after the Gap fire and in Los Angeles after a 2007 fire in sprawling Griffith Park which threatened the Los Angeles Zoo and the Griffith Observatory.

“We did it [hydromulching] right down to the observatory and the zoo,” he recalls, noting that in most cases, there is a buffer of a few hundred feet between structures and power lines.

“When there’s urban infrastructure, when there are power lines, roads, houses and that sort of thing, you have to buffer away from those a certain amount,” agrees Griffin of Santa Barbara County. “That’s why the Jesusita fire was a little more challenging than the Gap fire.”

While residents will see the planes buzzing the hillsides and dropping the mulch, they will also noticed the hillsides turning green. That’s because the hydromulch contains a green dye, similar to food coloring, to help identify areas where the mulch has been dropped.

That green coloring is designed to quickly start fading and after about a week or so the mulch turns to a natural wood color, Reid says.

While the coloring may disappear, the mulch will remain, he says. The hydromulch dropped last year is still visible on the ground today, he adds.

“It starts to break down with more moisture and weather, but you can still walk up there and see it on the slopes today,” he says.

Originally, the product was designed to hold in moisture for newly seeded areas such as lawns or highway projects.

“That’s its main design, to slow down the rain impact and then hold in the moisture for the new germination of the seed,” Reid explains. “We’re just using it here on top of a seed base that’s already in the ground. After a wildfire, there’s usually enough native seed base already on the ground so you don’t need to reseed. Those seeds are still viable.”

In other cases, particularly non-aerial applications, Western States has mixed the mulch product with seed. It has also mixed the mulch with both seed and fertilizer for a project for the Bureau of Land Management following a fire.

Reid notes that while his company has used different products over the years, the hydromulch wood-paper blend is the most common.

“That’s a Forest Service standard,” he says.

Most of the wood mulch used for the aerial hydromulching of the Jesusita fire area was fir and aspen, he adds.

“There are different brands . . . each company has its own wood source. Most people won’t know the difference when it’s ground up,” Reid says.

In addition to dealing with local, state or federal agencies, Reid says the public often weighs in on hydromulching plans.

“No matter what you do on a project like this, there are going to be people that oppose it and people who are for it,” he says. “Overall, usually the general public loves it because it’s protecting their back yard. But there’s always some group that thinks it’s not natural to do it.”

Criticism of hydromulcing in Santa Barbara County was quick in coming.

“Anyone who has seen the actual result of hydromulching of the Gap fire region knows hydromulching is a total joke,” claimed one Santa Barbara County resident on a community-based  Web site. “After a couple of months the wind blows the hydromulch around so the ground is totally exposed again. You end up with a single thumbnail-sized hydromulch flake ‘protecting’ square yards of bare soil. Hydromulching is just a fancy name for littering. . . And the $4.8 million was totally wasted on a process that ended up doing nothing. Let nature take care of itself, please.”

Others who have studied erosion control methods after a wildfire report that hydromulching and other techniques can be beneficial.

“Straw mulch and hydromulch were effective in reducing post-fire erosion rates in the first two years after high-severity wildfires, as they immediately increased the amount of ground cover,” said researchers in a Joint Fire Science Program that studied the effectiveness of erosion control after wildfires.

“In general, post-fire rehabilitation treatments cannot prevent erosion, but they can reduce overland flow amounts, site soil loss and sedimentation for some rainfall events,” noted another study reported at the American Society of Agricultural and Biological Engineers annual international meeting in 2006. 

For Reid, the arguments for and against hydromulching take a back seat to the actual logistics of coordinating and carrying out the aerial operation.

 “It’s a fast paced, large-scale operation that’s usually done in a short amount of time,” he says.