Grantee Research Project Results
Final Report: Sustainable Erosion Control in Developing Countries Using Industrial By-Products
EPA Grant Number: SU835079Title: Sustainable Erosion Control in Developing Countries Using Industrial By-Products
Investigators: Chrysochoou, Maria , Boyer, Dana , Cipoletti, Scott
Institution: University of Connecticut
EPA Project Officer: Hahn, Intaek
Phase: I
Project Period: August 15, 2011 through August 14, 2012
Project Amount: $15,000
RFA: P3 Awards: A National Student Design Competition for Sustainability Focusing on People, Prosperity and the Planet (2011) RFA Text | Recipients Lists
Research Category: Pollution Prevention/Sustainable Development , P3 Challenge Area - Sustainable and Healthy Communities , P3 Awards , Sustainable and Healthy Communities
Objective:
The purpose of this project is to utilize locally available industrial by-products to stabilize the road in the community of La Prusia, Nicaragua and sustainably mitigate the erosion, eliminating the need for annual repairs. Intense rainfalls cause extensive damage to the main dirt road every year, to the extent where the road becomes unusable to the 1,000 people living adjacent to the road. Without a functioning road, community members lose access to education, jobs, and other services of the city. The city currently utilizes a mix of volcanic rock and ash for the surface of the road, which cannot withstand erosion; paving the road with cement or asphalt requires approximately $400,000, which the community and the city cannot afford. The successful use of these byproducts for erosion control is a function of several parameters: a) waste properties; b) soil properties; c) slope characteristics; d) amount and velocity of runoff on the road. In addition, the mix design and compaction process for the waste-soil combination have to be devised so that it can be easily implemented with the means available within the community. The feasibility and sustainability of this project entails not only the use of waste products, but relies also heavily on the ability of implementation without the use of expensive, specialized construction equipment and on the involvement of the local community for construction and maintenance. Finally, an important component of the project is to investigate the environmental implications of placing waste products back into the environment and exposing them to large amounts of water, which could leach contaminants from the waste products into the natural environment.
The purpose of this project is to utilize locally available industrial by-products to stabilize the road in the community of La Prusia, Nicaragua and sustainably mitigate the erosion, eliminating the need for annual repairs. Intense rainfalls cause extensive damage to the main dirt road every year, to the extent where the road becomes unusable to the 1,000 people living adjacent to the road. Without a functioning road, community members lose access to education, jobs, and other services of the city. The city currently utilizes a mix of volcanic rock and ash for the surface of the road, which cannot withstand erosion; paving the road with cement or asphalt requires approximately $400,000, which the community and the city cannot afford. The successful use of these byproducts for erosion control is a function of several parameters: a) waste properties; b) soil properties; c) slope characteristics; d) amount and velocity of runoff on the road. In addition, the mix design and compaction process for the waste-soil combination have to be devised so that it can be easily implemented with the means available within the community. The feasibility and sustainability of this project entails not only the use of waste products, but relies also heavily on the ability of implementation without the use of expensive, specialized construction equipment and on the involvement of the local community for construction and maintenance. Finally, an important component of the project is to investigate the environmental implications of placing waste products back into the environment and exposing them to large amounts of water, which could leach contaminants from the waste products into the natural environment.
- Investigate the resistance of soil-waste blends to runoff-induced erosion as a function of soil properties and runoff characteristics.
- Determine the environmental quality of the runoff and the infiltrated water that comes in contact with the stabilized soil blend.
- Design a mixing and compaction process that can be implemented with locally available manpower and equipment.
Summary/Accomplishments (Outputs/Outcomes):
Two waste products were identified in Nicaragua that can be used for sustainable soil stabilization: Lime Kiln Dust (LKD) and Rice Husk Ash (RHA). LKD is the by-product of burning limestone to produce lime (CaO), while RHA is the residue of burning rice husks after harvesting. LKD is a cementitious product and be used on its own to stabilize clayey soils, while RHA is used as supplement in cement and in conjunction with lime and non-plastic soils. We discovered that no by-products are landfilled in Nicaragua; everything is marketed. We identified a lime-producing plant in San Juan del Sur, Nicaragua and a rice processing facility in adjacent Granada and collected samples. In addition to LKD, we also collected samples of the industrialgrade lime that is produced from the same facility in order to conduct a comparison of properties versus price. Industrial-grade lime is sold at $9.2 per quintal (local unit equal to 46 kg), while LKD is sold at $2.3 per quintal or 25% of the price. We found that the LKD contains 40% free CaO (the active ingredient), while industrial-grade lime contains 70% CaO, rendering LKD a cost-effective alternative. Soil analyses indicated that the native soil exhibited sufficient plasticity to be mixed with LKD without additional pozzolans.
We gauged the erosion resistance of the soil by performing unconfined compressive strength (UCS) tests on untreated soil and soil treated with varying levels. We observed that the addition of 7.5, 12 and 19.5% of LKD doubled soil strength from 20 to 40 psi within 7 days of reaction, and that there was no additional benefit in increased dosages. Thus, we chose to perform the field trial with 12% LKD; the medium dosage was chosen because mixing in the field is not optimal and performance may be lower due to a variety of factors (poor mixing, sub-optimal compaction, scavenging of CaO by CO2 etc.).
The field trial took place in the week of March 2nd to March 9th, 2012. The EPA P3 procured the LKD with the assistance of the local NGO, Casas de la Esperanza. The city of Granada provided the personnel and equipment necessary to conduct the trial, consisting of one engineer, four workers, one excavator and compactor and one watering truck. Two sections of 10 m length and 3 m width each were selected along the road, one with medium and one with severe erosion problems, in order to compare the performance of the mix under different conditions. A short video of the execution of the field trial can be found on the project site www.engr.uconn.edu/geo/epap3. The procedure is shown in Figure 1.
Figure 1.
The EPA P3 team provided instructions to the field engineer (Fig. 1e – not the child) and to the workers throughout the process, and also participated actively in the placing of the material (Fig. 1c). The team also took soil water content, density and strength measurements before and after the trial, which will be utilized to assess the performance of the mix after the rain season commences in May. The installation of permanent monitoring equipment is not feasible because reportedly everything exposed is bound to be stolen. Finally, the team informed several of the community members along the road on the activities, conducted interviews and met with representatives of the city and the NGO to coordinate a potential full-scale application. The city and field engineers were satisfied from the outcomes of the laboratory and field trials and showed interest to apply this methodology not only to the road in La Prusia, but to other constructions projects as well.
Conclusions:
The utilization of lime kiln dust for stabilization of the erosion-prone road in La Prusia, Nicaragua, appears to be a viable and cost-effective solution on the basis of our laboratory analyses and field trial. Laboratory results indicate a rapid increase in soil strength upon mixing with LKD, which is necessary to counter the stresses induced by water flow. The field trial indicated that the equipment available locally is adequate to achieve satisfactory mixing and compaction of the material. Even though process control was not optimal, compaction conditions were comparable to those achieved in U.S. subgrade compaction processes. Additionally, the logistics and costs of procuring and transporting the necessary amounts of LKD to the road are manageable and are estimated to be 10% of the cost to pave the road with conventional materials. Finally, the municipality of Granada is amenable to adopting this approach not only for La Prusia, but for other projects as well. We therefore consider the project to be successful and our approach to be very promising for application in regions with similar conditions, in Central America and elsewhere. The main obstacle to achieve these goals was found to be that the flow of information and pace of action are much slower in developing countries; engagement of local NGOs and stakeholders is paramount to the success of any such project.
Supplemental Keywords:
erosion, soil stabilization, industrial by-products, developing countriesRelevant Websites:
EPA Grant to Support EWB Work in Nicaragua Exit
UConn EWB: Recon in Nicaragua Exit
The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.