Remediation: Techniques and Cost - Urban Watersheds: Geology, Contamination, and Sustainable Development - page 410

100000

10000

1000

100

10

1

Sand and
silty clay

Clay Silty clay Sand

Geology
Chrome VI
DNAPL

LNAPL
PAHs

Lead
PCBs

FIGURE 11.32
Remediation cost per kilogram of contaminant by soil type.

Figure 11.32 shows that remediation costs are highest for DNAPL and Chromium VI.
The figure also illustrates how contaminants with a high CRF GW released into a vulner-
able geologic environment produce a synergistic effect. The cost of remediating chromium
VI and DNAPL VOCs in geologically vulnerable areas results in a cost of remediating a
kilogram of contaminant that is greater than $77,000 and $66,000, respectively. The cost of
remediating chromium VI and DNAPL VOCs in the soils with lower geological vulner-
ability is over 50 times less.
The cost to remediate a kilogram of PCBs is the third highest for the contaminants evalu-
ated. This elevated cost results from two factors: (1) PCB remediation is heavily regulated
and requires intensive investigation and review and (2) PCBs are occasionally detected in
sediments requiring a remedial action.
LNAPL VOCs, lead, and PAHs are not influenced by geology to the extent exhibited by
chromium VI and DNAPL VOCs. These contaminants do not exhibit a sufficiently high
mobility or persistence, which results in a lower CRF GW . As a result, these contaminants
are more cost effective to remediate on a per kilogram basis.
Overall, cost effectiveness in remediating groundwater has improved, but still remains
high. On average, groundwater is six times more expensive to remediate than soil, and
this cost differential increases to a factor of 10 when remediating contaminated ground-
water with Chromium VI or DNAPL. The time required for remediation is a key factor
contributing to the cost differential between soil and groundwater. When only soil was
contaminated, the average time required to investigate and remediate a site was 2 years; if
groundwater was contaminated, the same operations took 13 years.

11.11 Summary and Conclusion
This chapter has highlighted the different remedial approaches for cleaning up our air,
water, and soil. The approaches taken for remediating the air and surface water are heavily