Because there’s no cookie cutter oil containment solution that applies to all substations, we get a lot of questions from customers and potential customers in the field concerning the adaptability of our innovative secondary containment offerings. We initiated our Subject Matter Expert blog post series to tackle some of these specific queries.
“Can we use your secondary oil containment systems even if we need to drive our maintenance trucks, equipment and vehicles into the containment area?”
We hear this question often, generally regarding older substations that need to be retrofitted for secondary oil containment systems. Routine maintenance procedures allow workers to drive vehicles very close to the oil-filled electrical equipment on site. Ideally, the utilities prefer to incorporate oil containment systems that don’t require them to adjust standard maintenance processes. We understand, so on that note, the short answer is yes, our secondary containment solutions would accommodate frequent drive over use.
However, because we’re established SMEs in this industry, the short answer just isn’t good enough. Protecting the environment while complying with strict regulations demands an upmost attention to detail, and it’s important to understand the different drivability options available with our oil containment systems.
Drivability Scenario 1: Below-Grade Oil Containment Systems (Geomembrane Liner with Oil Filtration Panels System, or Oil Filtration Wall System)
The keyword is “below-grade.” For below-grade oil containment systems, drivability can usually be accommodated without the addition of a vehicle berm or ramp, as long as the design planned for such activity and was correctly installed. In most cases, the only requirements to drive over our below-grade systems is a simple matter of using the correct stone. Six inches of pea stone must be laid below the liner, and geotextile fabric must be placed over the liner floor before the system is backfilled with clean, washed stone. Even without using compacted aggregate, a natural compaction will occur with substantial traffic. We recommend backfilling with 12-18 inches of stone (sized ¾ to 1.5 inches) to ensure the integrity of the liner is not compromised under additional weight, and to provide at least 30 to 40 percent void space. The formula for the size of material compaction and the acceptable displacement of 14 lbs. per square inch will ensure minimal compaction takes place.
Basically, the deeper the oil containment system is, the fewer concerns exist about vehicles driving over it. The only way the oil containment system can be compromised is if that weight displacement is exceeded. For example, if a crane outrigger is required, a 2 foot square pad will allow you 8000 or more pounds of lifting before compression would become a concern.
A word of caution: While drivability is easily accomplished with this system, care should be taken in regards to the maneuverability of the vehicles, at least initially. Abrupt turns can cause displacement of the gravel. Always inspect the area after it is driven on, and rake gravel back into place if necessary. In cases in which larger equipment is required to drive over the containment, consider using a temporary weight displacement or ground protection mat.
Drivability Scenario 2: Oil Containment System with Berm
If it isn’t possible to install an oil containment system to grade or below grade, we recommend constructing a secondary containment berm as an alternative. The two types of permanent containment berms used most often are earthen berms and DGA (dense grade aggregate) berms. An earthen berm is constructed of soil, debris and stone to form an impervious surface. The DGA berm utilizes a finely crushed densely-graded mix to construct a relatively impermeable subsurface.
In diked applications of our Geomembrane Liner and/or Oil Filtration Walls oil containment systems, we suggest combining these two berms to allow vehicles to drive over it. First, a permanent secondary containment earthen berm should be constructed over the Oil Filtration Walls (or liner walls with the Oil Filtration Panels) to allow for water flow. Designate an area for a vehicle ramp that will allow drive over use without high maintenance. The vehicle ramp should be packed using finely crushed limestone or similar to form a DGA berm. The best part about the DGA berm is that it turns into an almost asphalt state that is compliant with secondary containment regulations.
We urge all our customers to discuss drivability options with their engineer during the initial planning phases.
The C.I.Agent Secondary Containment Solutions Tool Can Assist in Exploring All Available Options
Like we mentioned before, there’s no one-size-fits-all secondary containment option for transformer oil protection. It seems there’s not even a one-size-fits-most solution, at least according to a 2012 IEEE survey regarding the IEEE P980 Standard Guide for Containment and Control of Oil Spills in Substations. The results of that particular survey could not indicate a single containment system or discharge control method that is preferred the most; in fact, the respondents employ a number of methods successfully, and tend to favor their own method in regards to effectiveness.
Lucky for you, the process to identify the ideal containment solutions for your specific site is as simple as a few clicks of the mouse with our FREE, online Secondary Containment Solutions Tool. This is the logical starting place for deciphering what’s needed to provide a complete oil containment system. Not only does is assist in navigating the variables that directly contribute to the decision-making process, it also delivers real-time oil containment suggestions.
Interested in more of our secondary containment solutions for your oil-filled transformers? Do you have a larger containment need that involves a manhole or vault? We have you covered. Download / fillout our Site Assessment Sheet to request a quote today!