Geoenvironment Impact Mitigation and Management - Sustainable Practices in Geoenvironmental Engineering - page 382

Determine if
all necessary parameters
are present

Site
conditions

No

Determine type of
remediation
procedure required
consistent with
regulatory
requirements and
economic feasibility

Yes

Determine
if patterns of natural
attenuation are sucient
evidence

Patterns of
natural
attenuation

No

Yes

Supporting
laboratory
research

Evaluate
supporting studies to
determine if MNA can
proceed

Determine if NA can
be used in support of
other technological
remediation scheme

No

Predictions
from transport
and fate models

Yes

Develop
monitoring
requirements
and scheme

Determine if
MNA process will satisfy regulatory
requirements

Yes

No

FIGURE 10.13
General protocol for considering MNA as a remediation tool. (From Yong, R.N. and Mulligan, C.N., Natural
Attenuation of Contaminants in Soils , CRC Press, Boca Raton, FL, 310 pp., 2004.)

properties, and hydrogeology, and (c) regulatory requirements governing evidence of suc-
cess of the MNA remediation project. Lines of evidence and evidence of success will be
discussed in the latter portion of this section.
The data and information inputs shown on the left-hand side of the diagram in Figure
10.13 tell us what is required to satisfy site-speciic conditions, and whether the indica-
tors for natural bioremediation are suficient to proceed with further examination to sat-
isfy that the use of MNA is a viable treatment option. Negative responses from the irst
two decision steps will trigger technological and/or engineered solutions to the remedia-
tion problem. As will be seen, laboratory research and transport and fate modeling are
needed to inform one about the ability of the site materials and conditions to attenuate the
contaminants.
Adoption of natural attenuation (NA) as an active tool in the management of contami-
nant impact and transport, as opposed to the use of MNA as a passive tool, has been
hampered because of insuficient knowledge of the many processes that contribute to the
natural attenuation process. The designation of MNA as more of a passive tool as opposed
to an active tool is based on the fact that except for the monitoring requirement, the use
of natural attenuation processes as existent in situ is essentially a “do-nothing” solution.
The do-nothing part refers to human contribution to the processes resulting in natu-
ral attenuation of contaminants. As a clariication, we should point out that the acronym
NA is used to denote natural attenuation as a process tool. When we wish to discuss the
processes that result in the natural attenuation of contaminants, we will use the complete
term natural attenuation . To make NA an active tool, we can (a) enhance the processes that