Downslope Upgrade

June 15, 2013

Clow Road Landfill was an abandoned 35-acre site located north of Houston, TX. It contained discarded building materials and trash, smelled bad, and was an eyesore to the surrounding community. When methane gas, formed naturally from the decaying waste in the underground landfill, began to escape into the air, the site drew environmental concerns from citizens living in nearby neighborhoods.

The Texas Natural Resource Conservation Commission, a state environmental agency, was contacted to develop a plan to bring the abandoned landfill into compliance with state and federal environmental regulations. The agency’s plan included installing vent pipes capped with wind-driven turbines to safely vent the methane gas, constructing a landfill cover using fill dirt to conceal the original site, and constructing a slurry-wall trench to surround the perimeter of the property. Plans specified that the sloped earthen mound and clay cap, as well as surrounding acreage, be covered with topsoil and grass. Four flumes were to be built to direct stormwater runoff away from the 40-foot-high mound. It was critical to manage the preparation of topsoil and vegetation on the sloped mound and to control dust that was disturbing adjacent residents.

But summer drought conditions created two problems for the project. First, the site could be a source of dust generation that might disturb adjacent residents who lived downwind. Second, without plentiful water to help establish its root system, the freshly laid sod would surely die. The existing drought conditions would have made sodding a waste of time and money.

The ideal solution would be a single product to control dust, preserve the freshly planted seed during the drought period, and resist erosion from the heavy rains that the Houston area would eventually receive. PennzSuppress D was selected to tackle the problem of stabilizing the ground to control wind and water erosion on the sloped and bermed soil until the turf could be established after the drought conditions subsided.

PennzSuppress D is a patented product that has proved effective in controlling erosion often occurs in and around road and bridge construction projects. It is a soil binder that prevents erosion on sloping embankments during critical soil stabilization and turf establishment periods without the need for mulch. It does not inhibit plant growth and can be mixed and sprayed together with hydromulch.

Plans specified that the sloped earthen mound and clay cap, as well as surrounding acreage, be covered with topsoil and grass.

Developed more than 20 years ago, the environmentally safe product eliminates wind and water erosion problems on steep embankments bordering highway overpasses and bridges, roads, airport runways, stormwater channels, and other sites. It performs in demanding weather conditions to stabilize the soil and prevent erosion from occurring.

Although the original plans for Clow Road Landfill included applying expensive sod around the sloping dirt mound and on most of the flat ground surrounding the mound, the project specifications were revised to eliminate the sod and add drill-seeding and an application of PennzSuppress D to seal the soil after the grass seed was planted and fertilized. “This approach was significantly more cost effective than the sod alternative,” says PennzSuppress Corp. president Chuck Johnson. “Taxpayers did not have to waste money to replace sod that was sure to die in the drought conditions present at that time.”

PennzSuppress D was applied in ratios of 20:1 dilution (20 parts water to one part product) on the top and 15:1 dilution on the sloping sides of the mound. The product was applied to the landfill slopes from a fantail spray nozzle at the back of a water truck.

PennzSuppress D works as a soil sealant by penetrating deep into the ground to improve the cohesion of the soil surface. This improved cohesion significantly decreases the amount of material available to erode by either wind or water action. At the same time, because PennzSuppress D does not inhibit plant growth, it is a useful binding agent. When sprayed with a hydroseed mixture, it acts as a tackifier until root growth progresses to provide a means to further reduce or prevent surface soil movement and seed loss. These qualities make it effective for controlling erosion on areas where vegetation or ground cover will be grown. The product can also be used to provide temporary reduction of surface soil movement until more permanent measures are taken to eliminate or control erosion.

“The project required a highly effective erosion control product that met or exceeded government environmental and safety regulations,” Johnson explains. “When PennzSuppress D is properly applied, it does not pollute the air or water, harm wildlife in rivers or streams, or inhibit plant growth.”

PennzSuppress D had advantages over other soil sealant products in that it could be sprayed on the soil. This method reduced labor costs associated with installing sod. The non-water-soluble ingredients in the product won’t wash off in a heavy or prolonged rainfall that could eventually interrupt the existing drought conditions.

Within weeks after the PennzSuppress D was applied at the landfill project, torrential rains repeatedly challenged the product’s ability to perform after the seeding and treatment was applied. During one day, a 7-inch rainfall was recorded at nearby Houston Intercontinental Airport.

“A total of 14 inches of rain fell during the three months following the Clow Road Landfill seeding, yet the soil continued to remain stabilized and in place, supporting a vigorous growth of rye grass along with an underlying growth of Bermuda grass,” says Johnson.

Because of the differences in the permeability of sand and clay soils, the concentration of the product is varied to promote its penetration into the surface and improve cohesion of the soil surface. When it is used in slope protection applications on clay soils, the low permeability of clay limits available pore space to absorb a liquid product. Accordingly, the product is diluted with 15 parts water to one part product. Clay soils are generally more cohesive than sandy soils and have better resistance to erosion. Therefore, not as much product is required to stabilize clay soils, and a higher dilution rate can be used to obtain desired erosion control results.

The formula contains no volatile organic compounds or ozone-depleting substances. It is a combination of wetting agents, emulsifiers and bonding agents. It’s classified as nonhazardous, nontoxic, and noncarcinogenic, according to federal EPA and OSHA guidelines, and helps users in complying with federal Clean Air and Water Act requirements by reducing airborne dust emissions and silt runoff.

“PennzSuppress D has been approved by a number of the toughest government agencies and has proved to save 80% or more of the water used in normal dust control applications,” Johnson adds. “It is vastly superior to most traditional methods as an erosion control agent because PennzSuppress D penetrates the soil, rather than simply lying on the surface. This penetration binds the soil together, which causes moisture to run off without carrying the soil with it. With this product, the normal “˜fluting’ erosion of the soil simply does not occur.”