Case Study An innovative cover system to close an ash/ sludge impoundment By Paul C. O'Malley, José L. Urrutia and Don DiGuilio T he two projects (confidential client) are industrial sites consisting of coal ash and by-product sludge located in the southeastern United States. The projects included 70 and 67 acres (28 and 27 ha) in closure areas, and the waste source consisted of industrial sludge with a California Bearing Ratio (CBR) of less than 1% in the top 10 feet (3 m) of waste elevation. The objective was to transition the sites into final closure while satisfying all environmental regulations and technical requirements in a cost-effective manner. The closure of the sites was regulated through state and federal air-quality rules. Specifically, all gas coming from the sites needed to be collected and flared off. In addition, all leachate needed to be managed effectively to prevent groundwater contamination. The goal of the projects was to fully dewater with a stable and final impermeable cover that provided a long design life and minimal maintenance requirements. Figure 1 shows the completed 70-acre (28-ha) installation. Additionally, the community sentiment toward these projects was strained due to historical and current odor problems. Improving community relations was a high priority for the solution selected and implemented. The traditional approach for remediating sites such as these would typically entail: 1. Dewatering 2. Adding fill as necessary to achieve desired grade 3. Grading 4. Installing an impermeable layer such as clay or a flexible membrane liner (FML) 5. Adding a protective soil layer on top of the impermeable layer/liner 6. Adding a vegetative cover layer on top of the soil layer to control erosion PROJECT HIGHLIGHTS COAL ASH/SLUDGE IMPOUNDMENT FINAL COVER LOCATION South Georgia GEOSYNTHETICS PRODUCT ClosureTurf patented by Watershed Geosynthetics LLC GEOMEMBRANE MANUFACTURER AGRU America Inc. ENGINEERED SYNTHETIC TURF MANUFACTURER Shaw Industries Paul C. O'Malley formerly served as vice president of sales with Watershed Geosynthetics LLC. José L. Urrutia, P.E., is vice president of engineering with Watershed Geosynthetics LLC. Don DiGiuilio is eastern region marketing manager with AGRU America Inc. All photographs and illustrations courtesy of the authors. www.GeosyntheticsMagazine.com 33http://www.GeosyntheticsMagazine.com