Neal Bolton

By Neal Bolton

When new areas of a landfill are developed, often there is surplus soil that must be placed into one or more stockpiles. The location and use of each of these stockpiles should be evaluated as part of the landfill's overall soil management plan. Here are some things to consider before you decide where to stockpile that surplus soil.

Safety
Traffic control at landfills is a major safety concern that can be magnified when customer vehicles are mixed with scrapers or haul trucks. Minimize this risk by using dedicated roads for hauling soil. Also consider placing the stockpiles nearer the active fill area. With careful planning, the potential safety issues related to mixing scrapers or haul trucks with landfill traffic can be reduced or perhaps eliminated altogether.

Minimize Handling Cost
Keep your costs down by selecting stockpile location(s) that provide quick and easy access. When we're talking about heavy equipment, time is money.

Efficient hauling can be boiled down to two things: payload and cycle time. When I first started operating equipment, an old-timer told me, "Don't try to get the biggest load or the fastest cycle time. It's the guy who gets the most dirt to the stockpile at the end of the day that wins." So try to find the combination of payload and cycle time that yields the best overall productivity. In general, average-sized loads and shorter, flatter haul routes are best.

Avoid Multiple Handling
Before you start hauling soil, take time to evaluate the stockpile's placement in relation to the long-term development of the site. There is considerable frustration that comes from moving the same soil two or more times because of poor planning.

To avoid multiple handling, balance stockpile size with soil needs for specific areas. Be sure to consider daily, intermediate, and final cover requirements in addition to soil used for roads, benches, liner construction, and other projects. Short-term fill sequence plans are a vital part of managing soil stockpile sizes and location.

A basic rule when handling soil is to move it fast and move it once. But there is another consideration: using stockpiles to increase settlement and create airspace.

Managed Settlement
Why not follow the example of progressive landfills that make free airspace by strategically placing soil stockpiles on top of the landfill? Your competitors may already be taking advantage of the accelerated waste settlement that can be achieved by surcharging the existing landfill with soil stockpiles.

You could gain a significant amount of settlement (several feet) by surcharging the landfill with one or more soil stockpiles. The amount of settlement achieved will depend on several factors:

• Age of the landfill
• Depth of the landfill
• Moisture content of the waste
• Depth of the soil stockpile
• How long the stockpile is in place

Other Factors
What might you expect? Well, I can't tell you what you'll get, but I can tell you what I've seen. In some cases, landfills have gained 10% settlement (of the total waste depth) in one to three years beneath a 10-foot-deep soil stockpile. The amount of settlement will vary, but in most cases it's a significant amount.

But, despite the benefits associated with surcharging, there are two important issues that should be addressed before surcharging the landfill with soil.

Issue 1: Survey the area prior to placement of the soil stockpile. The amount of soil placed in the stockpile should be recorded (i.e., by load counts). Similarly, the amount of soil removed from the stockpile should also be recorded (again, by counting loads). This ensures that no soil is left behind. It's a common oversight to leave portions of a temporary stockpile unexcavated, thereby voiding the intended goal of creating additional airspace.

Issue 2: It's always a good idea to obtain approval from the design engineer prior to surcharging any portion of the landfill. Soil stockpiles, if improperly placed, could damage the liner or leachate collection system, or potentially cause slope instability.

Finally, while soil stockpiles are the most common means of surcharging a landfill, they are not the only one. Remember, it's all about weight. The same benefits could apply by surcharging with greenwaste, woodwaste, rubble, compost, etc.

Be creative—airspace is where you find it.

Neal Bolton is a consultant specializing in landfill operations and management. He is principal of Blue Ridge Services in Atascadero, CA, and author of The Handbook of Landfill Operations.

MSW - March/April 2005