Contaminants and Land Environment Sustainability Indicators - Sustainable Practices in Geoenvironmental Engineering - page 317

Establish
hydrogeological setting

Compositional analysis
of spill or dump

Subsurface soil profile
and analysis

Inorganics and
organic chemicals

Soil and
groundwater
samples

Contaminant-soil laboratory tests
Soil and groundwater composition;
permeability; leaching; partitioning;
environmental mobility;
k ow , k d

Prediction of transport of
contaminants
Time-distribution of
concentrations and
types of contaminants

What are the
environmental and biotic
threat receptors at risk?

Assessment of nature of impacts

FIGURE 9.7
Schematic diagram showing procedures, factors, tests, and analyses required to begin the process for determi-
nation of consequence of surface discharge.

9.3.3 Subsurface Discharges

Subsurface discharges of contaminants arise when leaks or breakages in underground
liquid/gaseous storage facilities and underground liquid or gaseous pipelines occur.
Subsurface discharges of contaminants also occur when leachates escape from waste land-
ills (Figure 9.8). The left-hand portion of the schematic in Figure 9.8 shows the leachate
plume escaping at the bottom of the constructed waste landill. When properly designed,
with adequate barrier and liner systems underlying and surrounding the sides of the land-
ill, and leachate collection intercepts placed in the bottom barrier system, leakages are not
expected. Furthermore, with proper impermeable caps placed on the top of the landills,
water is not permitted to enter into the system. This subject is considered further in the
next chapter. A comprehensive discussion of waste landill barrier systems can be found in
textbooks dealing with the subject of landills and barrier systems (e.g., Yong et al . , 2010).
Leachates emanating from landills result from (a) landills not properly constructed,
(b) breaks in the liner and barrier system, (c) deterioration of barrier system, (d) incompatible
interactions between barrier material and leachate chemistry resulting in failure of barrier
to perform effectively, and (e) historic (old) landills built without any real site preparation
and therefore not constructed with attention to requirements for proper and secure contain-
ment with barrier and liner systems. Typical constituents in municipal solid waste (MSW)
leachates consist of various metals and salts such as Cd, Fe, Pb, Zn, Mn, Na, Ca, Mg, K, and
other inorganics including Cl and SO 4 . Biological and other parameters characterizing MSW