Not All Secondary Containment Is Created Equal: The Burdens of Earthen Berms




Editor’s note: This is the third in a series of posts discussing all of the various secondary containment solutions available, subsequent tradeoffs and/or maintenance associated with each, and how C.I.Agent Solutions offerings can enhance the different containment systems. Today’s post focuses on natural containment solutions, such as earthen berms. Read the first post on composite walls here, or the second post on concrete containment here.

 

Deciding what sort of secondary containment to implement at your facility to comply with SPCC regulations can be tricky. There are many options available, and all have advantages as well as tradeoffs. Some companies choose to utilize solutions that have a more “natural” appeal, such as earthen berms, as well as a couple others.

In the simplest terms, an earthen berm can be described as a level, raised bench or barrier, composed of the earth. The term berm derives from the French word berme, which means brim. The engineering of berms came about to aid the military during medieval times. Berms were used to ensure level space between defensive walls and adjacent steep-walled ditches or moats, and were intended to reduce soil pressure on the walls of the excavated part to prevent it from falling down.

Earthen Berm
This is an example of a typical earthen berm containment application

 

In most cases, earthen berms sites require excavation and special equipment to install, and are subject to water and wind erosion, as well as animal burrowing. They often utilize clay or bentonite mixtures as sealants. Free of chemicals, additives or anything toxic, sodium bentonite is an environmentally safe natural sealant that, when wetted by water, swells to 15 to 18 times its dry size. Clay liners obviously crack if they get too dry, though cracking will depend on the proximity to the water table and the how much it rains. Also, while a liner may be cracked at the surface, the cracks may not penetrate the entire liner. The effectiveness of a liner depends on a variety of factors. If clay liners are exposed to liquids, they will swell and the cracks will close. Once created, because they will likely hold water, earthen berms still require ongoing O&M, such as the use of manual valves, pumps, water inspection before pumping, or oil water separators.

One solution for this problem is to add a synthetic membrane or filtration media to the mix, such as C.I.Agent® Oil Filtration Panel. Oil Filtration Panels are designed to allow the unimpeded flow of water during normal rainfall or snow event, but become an impervious barrier in the event of an oil release. Constructed from non-woven geotextile materials filled with C.I.Agent Granules, a proprietary blend of USDA food-grade polymers, and backed with Agent-X, a non-woven geotextile materials with C.I.Agent embedded in the fabric, Oil Filtration Panels have become the accepted full containment solution for providing Secondary Containment as required by 40 CFR 112.7 (C) SPCC. Plus, if properly installed, it requires little or no maintenance and eliminates the need for other types of containment, sump pumps, oil-water separators, pits, manual valves and hydrocarbon detectors.

If the subsoil around the area to be contained is sandy or non-impervious, you may also need a liner for full protection, such as our C.I.Agent® Polyvinyl Blanket System. This containment system allows storm water to flow through the C.I.Agent® Oil Filtration Panel side walls while removing hydrocarbons. In the event of a catastrophic spill, the side walls solidify and capture the oil, keeping it from escaping.

Another major drawback of earthen berms is that maintenance workers have to step over the mound or dike, and they can’t drive their trucks over them. For these situations, we recommend constructing a vehicle ramp of finely crushed, packed limestone on the earthen berm, so workers can easily drive up to the equipment. Driving over a berm without the ramp could crush the Oil Filtration Panel system and cause product failure. Just be sure to discuss this request with your engineer during the initial planning phase.

In this natural solution, dubbed “water gate,” Oil Filtration Panels are strategically placed only at the bottom of a grade to process runoff through a water gate. River rip rap is placed on both sides to protect the gate, then covered with stone to complete the installation.

 

Barrier Boom
Water will be processed through C.I.Agent® Oil Filtration Panel and a water gate.
River rip rap will be placed on both sides to protect the gate.
River rip rap will be placed on both sides to protect the gate.
The finished application is covered with stone.
The finished application is covered with stone.

 

Then there are some natural methods of secondary containment currently in use that would probably do nothing to stop the ground contamination in the case of an unexpected leak. (They also couldn’t stop the PR nightmare associated!) This 2”x6” wooden board is an actual example of what one major utility company believed to be adequate containment for their substations. Seriously?

Does this look like adequate secondary containment to stop a transformer from leaking oil? We didn’t think so!
Does this look like adequate secondary containment to stop a transformer from leaking oil? We didn’t think so!

 

It’s So Easy To Install

Check back for next week’s post on containment options designed to leave a smaller footprint. Read our post on composite walls here and concrete containment here.

 

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