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Local fill means fewer trucks
What geocells are made of
Most geocell products are made of HDPE, the same material used for a lot of underground piping and conduits. It is a relatively inert material, especially when it isn't exposed to UV light.
The environmental case
Taken as a whole, geocells can provide a net environmental benefit. They substantially reduce the amount of excavation a site needs, and they widen the choice of materials that can serve as road base. Because local materials often work, specialized fills travel shorter distances, and fewer truckloads of muck have to be shipped somewhere else.
Cost and flooding
A road built with geocells can be just as strong and maintenance free for a lower cost, which means asphalt can sometimes be skipped where it would otherwise have been justified. Geocells can also work with cleaner fill that has fewer fines, making the surface more permeable than an asphalt parking lot and cutting the impervious cover that contributes to flooding.
Why does sunlight wreck some plastics?
Ultraviolet photons carry enough energy to break the chemical bonds in polymer chains, which makes the plastic brittle and chalky over time. Manufacturers add carbon black, which absorbs UV, to many HDPE products. Buried under soil or a layer of cover, geocells see no sunlight at all. HDPE is also the plastic of many milk jugs and detergent bottles, marked with recycling code 2.
How does a porous surface reduce flooding?
Rain falling on asphalt cannot soak in, so it runs into drains and streams all at once and raises flood peaks. Soil and gravel absorb part of the rain and release the rest more slowly. Fines are the smallest particles in a fill, and they clog the gaps between larger stones, so a fill with fewer fines leaves open channels for water to pass through. The US Environmental Protection Agency counts impervious surfaces among the main drivers of urban stormwater runoff.
Why is hauling fill so costly?
Fill is heavy and cheap per ton, so the cost of moving it can exceed the cost of the material itself. A typical dump truck carries roughly 20 tons, which means a road job needing thousands of tons of base rock sends hundreds of loaded trucks down public roads. Each of those trips burns diesel and adds wear to the road it travels on. Construction estimators treat haul distance as one of the main drivers of base material cost.