Info

i Waste 1

FIGURE 3.36 Typicalmultiplayer landfill cap. Minimum of 4 percent surface slope is usually preferred (Source: U.S. EPA, Handbook Remedial Action at Waste Disposal Sites, EPA/625/6-85/006, Hazardous Waste Engineering Research Laboratory, Office of Research and Development, EPA, Cincinnati, OH, 1985.)

FIGURE 3.36 Typicalmultiplayer landfill cap. Minimum of 4 percent surface slope is usually preferred (Source: U.S. EPA, Handbook Remedial Action at Waste Disposal Sites, EPA/625/6-85/006, Hazardous Waste Engineering Research Laboratory, Office of Research and Development, EPA, Cincinnati, OH, 1985.)

wind and water erosion and contribute to transpiration and evaporation. The final slope should be maintained at 1:30. A tight cover or membrane cap requires provision for effective gas collection and release.

Landfill Vegetation Four feet or more earth cover is recommended if the area is to be landscaped, but the amount of cover depends on the plants to be grown. Native grasses may require 2 feet of topsoil, and large trees with deep tap roots may require 8 to 12 feet. The carbon dioxide and methane gases generated in a landfill may interfere with vegetation root growth, if not prevented or adequately diffused. The gases can be collected and disposed of through specially designed sand or gravel trenches or a porous pipe gas-venting system. Oxygen penetration to the roots is necessary. Carbon dioxide as low or lower than 10 percent in the root zone can be toxic to roots; methane-utilizing bacteria deplete the oxygen. Precautions to help maintain a healthy vegetation cover include selecting a tolerant species and seeking professional advice, avoiding areas of high gas concentrations, excluding gas from root zone (use built-up mounds for planting or line with membrane or clay soil barrier and vent trench and plant in suitable backfill soil), avoiding heavily compacted soil (loosen first if necessary and

FIGURE 3.37 Final cover with passive gas vent. (Source: New York State, Municipal Energy Recovery Facilities Handbook, New York State Environmental Facilities Corporation, Albany, 1988.)

supplement soil fertility and improve its physical condition following good nursery practice), using smaller plant stock, and providing adequate irrigation (see Figure 3.38).

Landfill Mining

The excavation and recycling of a landfill waste appears to be feasible where there has been adequate moisture to permit decomposition and stabilization of the waste. On the one hand, in locations where rainfall averages 60 inches/year or more, a portion of the decomposed waste is generally suitable for recycling or for use as cover material for a new landfill at the same location excavated. On the other hand, in arid regions where the rainfall averages 10 to 20 inches/year or less, the waste placed in landfills is often well preserved after more than 20 years. Other factors such as landfill design, type of cover material, waste composition, and age of the landfill must be evaluated and regulatory approval obtained.

FIGURE 3.38 Completed landfill with irrigation system.

A thorough hydrogeological investigation of an old landfill site is necessary before considering its excavation (mining), recycling, and possible reuse. The up-gradient and down-gradient groundwater levels and quality, the depth and type of soil beneath the fill, the thickness of the fill and its composition, including the possible presence of hazardous wastes, are among the conditions to be investigated. Numerous tests are necessary as landfill waste is not homogeneous. If reuse of the excavated site as a municipal landfill site is proposed, preliminary discussions with the regulatory agency are essential.

Renewable Energy Eco Friendly

Renewable Energy Eco Friendly

Renewable energy is energy that is generated from sunlight, rain, tides, geothermal heat and wind. These sources are naturally and constantly replenished, which is why they are deemed as renewable.

Get My Free Ebook


Post a comment