Going to Seed
A variety of methods can help revegetate disturbed areas.
On September 11, 2001, Flight 93 went down in rural Shanksville, PA, after its passengers fought back against the terrorist hijackers. Ten years later, on September 11, 2011, a memorial site was dedicated.
Hilltop Seeds, of Shippenville, PA, was the subcontractor selected to acquire the seeds and to do the planting for the approximately 180 acres that required revegetation.
“The 180 acres were divided into several meadows, varying by the specific ecology of the ground, whether wet or otherwise. The meadow seed mixes were designed by a landscape architect,” explains Walt Robertson, president and principal owner of Hilltop Seeds.
“The topography was of two different types. Some of the ground that was not disturbed was originally, I believe, in the possession of the Pennsylvania Game Commission. It had been seeded to some extent with native grasses, but it had a lot of goldenrod and other invasive species.
“The plan was to kill that vegetation, but not to disturb [the area]. Then we would no-till plant with seed mixes that our architect had specified. Then there were disturbed areas for which excavation was necessary for the overall site layout. Those were also planted with the same meadow mixes.” He adds that cover crop seeding was originally planned as well, but because of delays in preparing the site, that was not carried out.
“We did attempt to plant some winter oats, so that they would winter-kill and give some protection to the ground, but actually the ground wasn’t really ready for that until too late for the oats to be really beneficial. They helped some, but not as much as they might have.”
Robertson notes that a number of meadow mixes were used. “We had wildflowers, native grasses, and all sorts of native plants, with the idea that they would be colorful and would represent a native meadow.”
According to Robertson, where the topography allowed, all the native grasses were seeded with a Truax no-till drill. “The Truax is designed specifically for planting the fluffy seeds that are typical of the native grass species here,” he explains. “That was the big challenge—to make certain that this stuff went through the drill appropriately. The Truax did do that; it accomplished it very well.”
Nevertheless, Robertson did face some challenging issues that had to be addressed. “One issue for me was having the excavation done on the disturbed ground and getting it ready to seed. For whatever reason, and the contractor may have had ample and good reasons, it was not ready on schedule for the planting. Had we been able to get the oats in around early August, and over the complete disturbed site, those oats would have developed some growth and a root system. Then the winter would have killed them, and we would have gone in and no-tilled right over those dead oats in the spring for the planting.
“We actually started the spring planting a little ahead of schedule, but again, we did it in bits and pieces because the ground just wasn’t ready for us to get down and deal with it. On the undisturbed site, where they were doing no excavation, that wasn’t an issue and we got things planted very quickly and on schedule. As far as the establishment of the meadow mixes, they seemed to do better on the undisturbed sites, where there was vegetative cover and erosion wasn’t a problem, so we had that benefit.”
Robertson notes that he had some difficulty in obtaining the seed mixes requested by the landscape architect for the project. “The seeds that were specified were very scarce, and the quantities that were required were just overwhelming, as far as finding sources. I spent the better part of a winter searching to track down the seeds. Things like marsh marigold we were unable to find in a quantity large enough to plant. But of all the species of seeds that were designated, I think we obtained all but three or four of them. We were able to find seed sources for the vast majority of them. Some were seeds we grew ourselves, but for the most part, these were species that we did not grow.
“The seed inventory at suppliers is pretty low, because of the terrible drought that has presented in Oklahoma, Texas, Kansas, and Missouri. I’m getting information from publications like the High Plains Journal that native grass seed prices this season will go up 20 to 40%, which is pretty dramatic.
“With some of these seeds, we’re talking hundreds of dollars per pound,” he adds. “They’re very tiny, very special, very scarce seeds.”
In Superior, CO, a suburb of Denver, a joint municipal project involving both the Urban Drainage Flood Control District and the city of Superior was completed recently.
|A Tennessee hillside with Flexterra
|Photos: SPECTRA ENERGY
After grasses were established
“They were doing some drainage improvements,” says Rick Kurth of Arrowhead Landscaping. “They put some natural log drop structures in the channel to control the flow of water. In addition, they had some erosion on the banks, so they just went through to fix all of that. Then we followed through and put in prevegetated wetland mats.” A total of approximately 5 acres required revegetation work.
A wide variety of products were used on the project, says Kurth, including prevegetated coir logs. “These came from North Fork, and our native plants out of Idaho. Then we used upland seeding, and a lot of KoirMat 700 on our channel slopes. That’s a coir, or coconut fiber, mat.” The mat was supplied in unseamed 13-foot by 165-foot rolls. “We had wetland plugs and prerooted willow stakes already growing within the logs. We used those at the toe of the slope, to get some revegetation going right away, along with the prevegetated mats.
“Bowman Construction was our supplier for the coir mats and the erosion control blanket,” he notes. “We also used Biosol fertilizer. We put that on at 1,200 pounds per acre. We used mycorrhizae on our seed mixes, and then we used the Soil Guard in the flat areas in our hydromulch areas.
“We installed our coir mats on the slopes with wood stakes. Then we used Flex Guard above the coir mats and out into the flat areas.”
Kurth says the landscape architects specified the various products. “They construct our drawings so that everything is approved and engineer-stamped. The architect is the one who specified the Biosol and all of the other products that we used.”
He adds that he has been using these items for a number of years and is quite pleased with the early results of the revegetation effort. “We’ve been using these products for quite some time, and get along with them fine.
“Our shrubs and our prevegetated wetland mats have already taken root. We watered those probably every other day during construction. It was kind of late in the season for prevegetated mats, but we kept them watered, and we had good water, so they got rooted pretty well. They should be a success in the spring.
“We’ve still got a few trees to put in. These don’t do well in the spring if you put them in during the fall and then have to water them through the winter. So we’ve got a few trees to do in the spring, but other than that, all of our shrubs and grasses are already planted, mulched in, and ready to go.”
According to Kurth, the project proceeded smoothly, for the most part. “We had only one or two rain days, but nothing really to slow us down,” he says. “We do a lot of work in the channels, so a lot of it can be done unless it’s really muddy. But if it’s a little tacky, we can still put down the biolog and the prevegetated mats. It was a pretty good construction project. We had no snow and no rains to speak of.”
He adds, “The Urban Drainage Flood Control District had weekly progress meetings with us on the site as the site was being constructed. Our work, and the general contractor’s work, was getting inspected every week. If any questions came up, we were able to get answers within a day or two. Everything was approved on our final walk-through. We’re just waiting to see what Mother Nature does to us this winter as far as moisture. Then in the spring, we’ll water everything with a hose reel to get our native grasses growing in the native area.”
Where There’s a Rill, There’s a Way
Dietz Hydroseeding was called upon to revegetate approximately 150 acres following a large fire in Simi Valley in southern California.
“After the fire, the California Department of Transportation [Caltrans] had several concerns,” explains owner Ron Dietz. “One was the wind blowing the ash and silt onto the highway, which would cause a traffic hazard. Additionally, the fire was in late October at the beginning of the rainy season. With no vegetation left, they were concerned about the silt and the ash running down, plugging up the drains, and getting onto the freeway.
“The interesting thing about this was that the area that burned hadn’t burned for many, many years. When the brush had been cleared, they found areas that had been so covered with brush that they had suffered severe erosion issues. There was rilling, there were drains that were completely grown over and covered, so water was causing erosion. On a couple of these hillsides, the slopes that came down to the freeway had significant erosion issues that hadn’t been visible before, so they hadn’t been addressed.
“Not only did they have the issue of the immediate erosion control and protection, but they also realized they had to do some structural regrading of these slopes.”
He notes that two slopes in particular had suffered severe damage. “The soil was very sandy, so even with the growth on them, there was significant erosion. That was a big problem for Caltrans. They had to come in and remove three or four feet of this hillside to get down to where the rills had caused the erosion.
“We went in with bonded fiber matrix and made a seed mix that consisted of some native grasses and indigenous plants to match the plant material that was growing around in the area. Our seed mix came from S&S Seeds, who we’ve been using since the mid-’70s. They have a good product, and are one of our best vendors.
“The site was graded, and we installed wattles at about 15 feet on center going up the hillside, and used the bonded fiber matrix with the seed mix. This was all done within four weeks after the fire—it was an emergency project.”
Although several significant rain events occurred shortly after the work was done, the hillside held. “We had stopped the erosion using the wattles and the bonded fiber matrix. If you go back today and look at that hillside, the growth is almost 100% reestablished,” he says.
“The revegetation on the destabilized hillside was largely a product of hydroseeding. They had to remove four feet [of soil], so it wasn’t a case of existing topsoil or existing seed that was still there. It looks fabulous today. It’s not as dense as when it burned, because at the time, there was 25 or 30 years of growth. But now, if you walk on it, there’s no rilling, there’s no erosion.”
Dietz has a theory about the origin of the severe erosion problems. “I think originally when they built the freeway, they hadn’t done any erosion control measures, and they probably either hydroseeded it, or seeded it without wattles and without slope control. During the first several years of establishing native material on the slope, small rills started, because there wasn’t erosion control during that time. The rills started from the first rain events. Plants did grow and get established, but the rilling was continuing underneath the plant material for 25 to 30 years.”
When the fire occurred, the scope of the problem became apparent. “Once you get those rills in the hillside, every time you have a rain event, the water flows down those specific pathways, and aggravates the erosion. If you have good erosion control in the very beginning, when that hillside was first built, first engineered, and you can stop the rilling right from the beginning as the plant material establishes, you don’t end up with those erosion problems that continue for years. If you have those problems at the beginning, it doesn’t stop. It doesn’t go away.”
Dietz says he was fortunate that excessive rain didn’t hamper his work for the most part. “We were pretty lucky in that we had established about 98% of the project before we got a substantial rain. There were some areas that were not completed that had rain, and they did have to go in and regrade those areas and fill any rills before we were 100% completed.”
He adds that Caltrans was especially pleased with the results. “They use those particular hillsides as an example of how native plant materials can be used, and how they pretty much eliminate maintenance other than picking up litter.”
In the fall of 2011, Brian O’Neill of Weeds Inc. was commissioned to revegetate about 33,000 square feet of land as a result of new construction for a home in Philadelphia.
|Photo: WEEDS INC.
Part of a revegetation project near Philadelphia’s Fairmount Park
|Photo: WEEDS INC.
Different seed mixes were chosen for slopes and lower, wetter areas.
Private Residence in Philadelphia
“It was an older home, and they put in new driveways and new garages,” he says. “Because of that, they had to change the various slopes and put in a new catch basin and spillways to move the water around the construction site.”
The property on which the home sits backs up to Fairmount Park, the largest urban city park in America. “It makes up close to 10% of the real estate in the city of Philadelphia,” says O’Neill. “It’s in different areas throughout the city, and this site is right next to it; the waters coming from this site end up going directly into the park.”
The company used two different seed mixes. “One was a low-growing hard fescue mix, known as PennDOT formula L. It’s a seed mix that is made up of hard fescues and fine fescues with a little bit of annual rye grass, which is a low-growing mix that does very well in shaded areas and on slopes and needs very little maintenance after it’s been established. It doesn’t need to be cut. It’s a great mix for establishing an area for very low maintenance. We put that around on the slopes and on the base of the spillways to establish vegetation and eliminate erosion.
“Besides the PennDOT mix, in the lower areas, we put in a wetter mix. It was an Ernst Conservation seed mix 131, a wetland mix. We chose this mix because it will do well in partial shade, and it likes wet feet. This was also planted in late fall, during early November. Erosion control matting was also used to get it established.”
O’Neill notes that within two weeks of seeding, germination had begun.
“Both sites were broadcast seeded in two directions so we got complete coverage,” he says. “We then put down the erosion control matting, and then put 10% of the same mix on top of the mat. At that time, we put down the soil amendments that were required. One site needed calcitic lime, the other site just needed fertilizer to get it started. But the most important thing is to take a look at what the soil tests tell you the soil needs to get these things established, depending on what seed mix you’re using.”
He adds, “At the one site, we also put down some gypsum, because the soil test, per Penn State University, indicated we needed some gypsum in there to get it kick-started.
“With the wetland mix, we just did the edges with the lime. I don’t like using any soil amendments in wet areas because of the surface groundwater. They will go right into the water table.
“The seed mix itself is a mixture of naturalized and native seeds. The native seeds have been here since prehistoric times. Naturalized seeds have been here since man has been here, and they’ve established well enough that they’re not invasive. Plus, you have new generations of seed mixes, so fine fescue or hard fescue may be naturalized because you’re now working on new generations and better quality of seeds.”
According to O’Neill, approximately 80% of the project was completed in the fall, with a warm season meadow scheduled to be phased in during the springtime months.
Pipeline in Eastern Tennessee
Extensive stretches of pipeline had to be constructed to achieve natural gas flows up to 150 million cubic feet per day to the Tennessee Valley Authority’s 880-megawatt combined cycle, natural gas-fired power plant in northeast Tennessee.
“East Tennessee Natural Gas [ETNG], which is owned by Spectra Energy Partners and Spectra Energy Corp., utilized existing utility corridors and pipeline rights of way where possible, minimizing the effects on landowners and the environment,” says Glen Morrow of Spectra Energy. “The project was placed in service on September 1, 2011.”
The work involved several principal elements, Morrow says. About 11.5 miles of existing pipeline was replaced with a new 24-inch-diameter natural gas pipeline in Tennessee’s Washington, Virginia, and Sullivan counties. In addition, 8 miles of 24-inch-diameter natural gas pipeline was constructed within ETNG pipeline easements in Sullivan, Washington, and Greene counties. Another 8.4 miles of 24-inch-diameter pipeline extension was constructed along an existing electric transmission line corridor in Greene and Hawkins counties, and piping at or near three different compressor stations was modified.
A variety of methods were used to revegetate the disturbed areas. “ETNG used cool-season blends of perennial grasses and legumes and annual seasonal grass varieties,” says Morrow. “The blends were developed for pasture lands, forested lands, and forested lands with extreme slopes. The species were selected based on several criteria, which include commonality to the area, landowner preferences for pasturing and haying, establishment success, survivability, and erosion and sedimentation control potential. ETNG worked with Pennington Seed to use engineered varieties, when available, that exhibit various superior growth habitats. Seeds were inoculated with MYCO Advantage and Germax (Rhizokote XL and Apron XL) seed coating.
“Prior to restoration, soil samples were collected and analyzed using the methods and practices prescribed by the University of Tennessee Agricultural Extension Service. Lime and fertilizer rates were established based on the results of the analyses, and these were applied in the rates prescribed.” The lime consisted of either pelletized or agricultural lime and fast-acting lime, as well as a lime supplement for the hydroseeding process. Morrow says 19-19-19 fertilizer was used. Crimped straw mulch was used where drilling seeding occurred. Flexterra High Performance-Flexible Growth Medium was used during hydroseeding.
“The technique of hydroseeding and the use of Flexterra were selected for this particular project due to the presence of many severe slopes, narrow ridges, and rugged terrain, primarily on the extension in Greene and Hawkins Counties,” he notes. “Special rigs were prepared by the restoration subcontractor, Terra Restoration, to perform hydroseeding in this terrain.”
Steve Goldberg writes on issues related to erosion control and the environment.
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