Geoenvironment Impact Mitigation and Management - Sustainable Practices in Geoenvironmental Engineering - page 361

solutions can be prohibitive because of the extent of the source (if such is known), and
the extent of contamination resulting from such a source. A good example of this is the
transport of contaminants in the ground and on the ground surface in conjunction with
pesticides and herbicides use. One needs to pay more attention to the impacts, from
both atmospheric- and land-based non-point sources of contamination, on the health of
both soil and water resources. If transport of contaminants is to receiving waters such
as streams and rivers, how does one use technological aids and engineered systems to
manage and control the advance of the contaminants? Erecting barriers that run a certain
length of the stream can be prohibitively costly. A good practical solution is to invoke the
properties of the natural soil system as a partner in mitigation-management. Amending
and enhancing the properties to make it more effective as a control tool would also be a
good tactic since this allows the subsoil to remain in place as a mitigation-management
tool. This tactic is now being used in a limited way in passive remediation-treatment of
contaminated sites.
10.5 Soils for Contaminant Impact Mitigation and Management
We use the term contaminant as a more encompassing term that includes both contami-
nants and pollutants. This means to say that the interactions and relationships established
between contaminants and soil particles pay no attention to whether the contaminating
substance is a contaminant or a pollutant. The designation of pollutant is a “human thing,”
made necessary to ensure protection of public health from contaminants that threaten the
well-being of humans if and when they are exposed to such contaminants, by direct con-
tact, inhalation, ingestion, etc. The deinitions for both contaminants and pollutants have
been given in the earlier part of this topic.
The latter part of Chapter 2 dealt with the nature and basic properties of soils as they
relate to the transport and fate of contaminants in soil. To be factually correct, we will use
the term contaminant in all the discussions to follow and reserve the use of the term pollu-
tant when this is factually required. In this section, we will be dealing with the aspects of
soils for mitigation of impacts from containments. The role of soil as a resource material
for management of contaminants is due to its physical, mechanical, chemical, and biologi-
cal properties. These properties constitute the basic tools for the many different strategies
and measures available for passive and aggressive management of the land and water
resources in the geoenvironment. The short discussions of these tools in previous chapters
referred to the total actions of the various soil properties in management of contaminant
waste streams as the natural attenuation process of soils. In this section, we will examine
the basic properties and attributes of soils in respect to “why and how” they can function
as tools for mitigation and management of contaminant waste streams in soils.
The properties of soil directly involved as a contaminant mitigation and control tool
are
a. Those that refer directly to the soil solids themselves. These are primarily the
physical and mechanical properties of the soil, and also the surface properties of
the soil solids responsible for sorption of contaminants. These include the den-
sity, macrostructure and microstructure, porosity and continuity of void spaces,