Geogrid reinforcement improves access.
By Ángel Conde
The 25-km dirt road from Jarabacoa to Constanza in the mountainous central region of the Dominican Republic has long been a lifeline for local farmers transporting their bananas, vegetables, strawberries, coffee, and flowers. But the road suffered from landslides, severe erosion, and uneven surfaces, which slowed the transportation of agricultural goods and limited access for locals.
The bumpy one-and-a-half to two-lane dirt road lacked appropriate lighting, proper drainage, and safety barriers. These limitations, combined with several narrow sections of roadway, created an incredibly dangerous road.
Landslides and uneven surfaces were a common problem because the man-made sideslopes were not designed or constructed properly. The road closed frequently due to landslides and would stay closed until the soil was removed or the lanes were repaired after the damage, causing havoc for the locals and daily travelers.
The road would take more than an hour to drive each way due to sharp curves, hazardous road conditions, and topographical changes. The rural road was originally developed in the 1950s as a secondary road for transportation of agricultural goods and for travelers to use to go to their vacation destinations. The damaged road was long overdue for repair to compensate for the increase in traffic and lack of maintenance over time.
A project to transform the road began in February 2011 and its main goal was to reduce the time and cost to transport agricultural goods between Jarabacoa and Constanza, as well as to other towns. A secondary goal was to facilitate access to tourist destinations in the area.
Because the road runs through the island’s largest mountain chain, there was no flat ground on which to build. A retaining wall is a great option when looking to increase the horizontal space on top of any walled structure and was considered for this project to generate the extra space to rebuild a new two-lane road.
The steep, natural slopes were exposed to severe erosion because the previous retaining walls were not properly engineered. By building new retaining walls, the contractor was able to create the necessary space for a two-way road, control erosion, and improve vegetation. A total of 8,3652m of the retaining wall was installed on 20km of the road.
Due to unforeseen conditions on-site, the 15-month design-build project changed daily. Rain was a constant challenge for the construction team that was determined to remain on schedule. The geological formations along the road required deeper excavations to obtain a firm and stable foundation for the retaining walls.
Finance and construction
The $100 million project, financed by the Ministerio de Obras Públicas de la República Dominicana, was subjected to a strict deadline because of the presidential inauguration at the time. Due to the needs of the agricultural and commercial economy in the region, the construction schedule included several daily stoppages to allow traffic activity.
It was important for the team to use materials that were easy to install to produce near-vertical walls that adapted to the geography of the site while staying within the project budget.
The face of the structure was almost vertical, so more space was generated on the top of the structure for an extra lane, without having to go as far down the slope to start the wall—saving materials, costs, and time.
This project was the first time any kind of segmental block retaining wall project had been undertaken in the Dominican Republic, therefore there were no local experienced retaining wall installers. In this case, the manufacturer provided on-site assistance, training, and technical and design support for the project.
An on-site, hands-on installation seminar was conducted for all of the project’s foremen and inspectors. The hands-on experience complemented the information and examples provided during classroom instruction.
The team completed its goal of reducing travel time between Jarabacoa and Constanza by more than 50%. It now takes 30 minutes to travel the entire stretch of road, which translates to lower costs for agricultural transportation. The new road also reduces the travel time to tourist sites in the area and eases travel to locals’ vacation homes.
The road is now wider, cleaner, and vegetation is aiding in erosion prevention. All of the improvements contribute to a more pleasant and safer drive.
Businesses and locals appreciate the ease of travel on the new Jarabacoa–Constanza road, and it has seen an increase in traffic. Before construction began there were about five vehicles on the road per hour, but now there are more than 30 vehicles per hour.
The new road not only improves the lives of the locals by cutting down on travel time, it provides a safer and healthier environment. Road dust has been dramatically reduced and land values near the road have gone up.
Ángel Conde is the Caribbean Regional Manager for Tensar International Corp. Inc.