Road Ecology Center

South America’s Amazon River basin rainforest contains perhaps the world’s greatest abundance of life, supporting over half of all known species of plants. Over the millennia, organic materials of similar origin have become buried and transformed into deep reservoirs of heavy crude oil. Commercial quantities are available within the Amazon’s headwaters region in the Colorado-sized country of Ecuador. In a country whose economy is largely dependent on oil, the formidable challenge is one of developing this vital resource in an environmentally sound and responsible manner, recognizing both the sensitivity of the rainforest and the rights of its indigenous peoples. The “lifeline” of the development (i.e., exploration, recovery, and transport) of the oil resource is the main road which serves as the haul-and-access corridor for personnel and equipment as well as the means by which pipeline is constructed and serviced. Left unsecured, the road could also create a conduit for unwanted colonists - speculators seeking to clear-cut the fragile forest for farmland or livestock pasture. Clearly, the patrolled road must be as narrow and inconspicuous as possible, while at the same time being economical and functional over the service life of the oilfield, and beyond. These challenges are further compounded by the area’s tropical and geological setting, forcing the project’s planners, engineers and builders to deal with the 500-cm (200-in) annual rainfall; weak, saturated, and highly plastic jungle floor subgrade; and acutely limited aggregates. Conventional road construction in this part of the world has been graveled “log corduroy rip-rap” — split tree trunks laid side-by-side, perpendicular to the road alignment like so many matchsticks to create a stiffened roadbed. With about 70 percent of the felled timber requirement coming from beyond the road’s edge, this methodology is environmentally prohibitive and economically unfeasible over the long term. A better solution was imperative. This paper describes the design, construction, maintenance, and performance of a 150-km (90-mi) long, 6-meter (20-ft) wide road comprising dredged river-sand subbase sandwiched between and reinforced by two layers of stiff polymer geogrid, confined along its edges by a non-woven geotextile and topped with a single course of processed, unbound aggregate base/surfacing. By eliminating the use of felled timber, the road’s right-of-way “take” could be minimized, and the resulting environmental and ecological impacts mitigated. Further, the use of geosynthetics permitted maximum structural utilization of precious sand and gravel, reducing borrow and haul requirements as well as enhancing the road’s long-term serviceability, while maintaining the thinnest possible section. Now 10 years after construction, the road continues to perform well. Government officials have realized the benefits of the new geosynthetic technology, and have re-written their environmental regulations for road building to encourage its use.