Written by: Cory Schneider, Business Development Manager
When contaminated material such as landfill waste or contaminated soil is encountered, there are typically two options available—removal of the material or placing a “cap” over it. In most cases, capping is the easier and more cost-effective of the two options. Caps serve to isolate the contaminated material, preventing people and wildlife from coming into contact with it.
Factors Influencing Landfill Cap Design
Landfill cap design for any particular site depends on many factors, including the type and quantity of contaminants, size of site, amount of rainfall, and future use of the area. It can consist of one or several of the following: asphalt or concrete, vegetative layer, drainage layer, and/or an impervious layer (geomembrane or compacted clay).
Preventing Slope Erosion with Advanced Geosynthetic Technology
When using vegetative covers, especially in sloped areas, one of the best ways to prevent long-term erosion of the cap is to confine the topsoil component using geosynthetics like the GEOWEB Soil Stabilization System (geocells). The GEOWEB Geocells, which are three-dimensional ultrasonically welded strips of high-density polyethylene (HDPE), create small pockets to hold soil in place. By doing so, the system prevents erosion or sloughing when the soil becomes saturated, thereby maintaining the integrity of the cap.
Understanding Superfund Sites
Superfund sites are contaminated areas that require a long-term response to clean up hazardous material contaminations. The federal government designates these sites, and the Environmental Protection Agency (EPA) leads the remediation efforts to ensure public safety and environmental protection.
Case Study: 68th Street Dump Superfund Site
One notable example of using the GEOWEB Geocells in a Superfund site is the 68th Street Dump in Baltimore, MD. This project involved capping 51,000 square feet of landfill with slopes up to 60 feet high ranging from 3:1 to 1.5:1. Slopes flatter than 3:1 were deemed to not be at risk of significant erosion, and therefore, no geosynthetics were used on them. The solution effectively stabilized the topsoil, met EPA guidelines requiring a 12-inch cover, and ensured long-term erosion control and environmental safety.
Read the full case study: Superfund Site Landfill Capping | Presto Geosystems
North Carolina Pre-Regulatory Landfill Unit
In 2007, North Carolina established the Pre-Regulatory Landfill Unit within the Inactive Hazardous Sites Branch to address pre-1983 non-industrial landfills and dumps (any land area on which municipal solid waste disposal occurred before January 1, 1983). A tax of $2 per ton on municipal solid waste and construction and demolition debris was imposed to fund the program.
As part of the program, the team published a comprehensive document outlining Unit procedures for completing assessments and implementing remedial action plans. This document includes acceptable procedures and products for dealing with pre-regulatory landfills. Specifically, the document lists GEOWEB Geocells as an approved product for creating soil cover “caps” at these landfills.
Case Study: Franklinton County Landfill
Another example of the GEOWEB Geocells in action is the Franklinton County Landfill in North Carolina. This project involved installing 102,810 square feet of 4-inch GEOWEB GW30V (mid-sized geocell) over 8-ounce nonwoven geotextile fabric, filled with about 2,320 tons of structural fill and 2,500 tons of topsoil. The GEOWEB geocell panels were connected with ATRA® Keys and secured with Woven Polyester Tendons and ATRA® Tendon Clips.
Read the full case study: Franklinton Landfill Remediation Project | Presto Geosystems
Incorporating geosynthetics like the GEOWEB Geocells in landfill capping applications offers an effective solution for isolating contaminants, preventing erosion, and ensuring long-term environmental safety. These case studies demonstrate the practical benefits and successful implementations of these advanced materials in real-world scenarios.
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