Urbanization and the Geoenvironment - Sustainable Practices in Geoenvironmental Engineering - page 227

performance (HELP) model (Schroeder et al., 1994), (b) HYDRUS (2D/3D) based on the
early work of Neuman (1972) who developed their UNSAT model, and (c) unsaturated soil
and heat low model (UNSAT-H) (Fayer, 2000). HELP has been the most frequently used
model for inal cover and leachate collection system design and is particularly useful
for humid and semihumid areas (Environmental Laboratory, 2014). Version 3.07 is now
available at http://el.erdc.usace.army.mil/products.cfm?Topic=model&Type=landill.
The HELP model does not simulate geocomposite lateral drainage layers well.
UNSAT-H is more appropriate for arid and semiarid regions for landill cover design.
MIGRATEv9 (Scientiic Software group, 1998) can be used for sorption, radioactive and
biological decay, and transport through fractures, in landills, buried waste deposits,
spills, or disposal ponds. POLLUTE does not utilize a contaminant migration analy-
sis program and thus requires little computational effort for landill designs, from
simple systems to those with composite liners and multiple barriers and aquifers. The
WHI UnSat Suite combines SESOIL, VLEACH, PESTAN, VS2DT, and HELP in a revo-
lutionary graphical environment speciically designed for simulating one-dimensional
groundwater low and contaminant transport through the unsaturated zone such as a
landill.
Wastes can also be classiied as demolition, nonhazardous (municipal) and hazardous
wastes. Inert or nonleachable wastes include many types of construction wastes such
as soil, bricks, concrete, tiles, and gypsum board. As long as they are not contaminated,
these materials can be reused as backill material, subgrade and road materials, and even
as building materials. Organic and inorganic wastes have been discussed previously in
Section 2.3 in Chapter 2.
Wastes can be classiied according to the physical state, origin, degree of hazard, or abil-
ity to be recycled or transformed. Wastes are classiied as hazardous if they have any of the
following characteristics:
• Ignitability : potential for ire hazard during storage, transport, or disposal under
standard temperatures and pressures
• Corrosivity : potential for corrosion of materials in contact with candidate waste,
resulting in environmental and health threats due to a pH less than 2.0 or greater
than 12.5
• Reactivity : potential for adverse chemical reactions when in contact with water, air,
or other wastes
• Toxicity : per the toxicity characteristics leaching procedure (TCLP). The leaching
test system for application of the TCLP procedure is shown in Figure 7.4 and the
regulatory levels of the compounds in the leachate are given in Table 7.3
In common with wastes generated from the various industries and manufacturing facili-
ties, MSWs also will ultimately ind their way into one or all of three disposal media:
(1) receiving waters, (2) atmosphere, and (3) land. Land disposal of waste products and
waste streams appears to be the most popular method for waste containment and manage-
ment. The various impacts arising from this mode of disposal and containment include
degradation of land surface environment and ground contamination by pollutants.
Because of the inhomogeneous nature of wastes, stability problems on the surface of the
landill, slope stability, and settling of the landill can occur. Chemical and biochemical
reactions within the landill and water iniltration will inevitably change the mechanical
properties of the landill.