Pollution Prevention - Urban Watersheds: Geology, Contamination, and Sustainable Development - page 442

hazardous substance inventory has been completed, a map should be created showing the
following: location of where each hazardous substance enters the property, where the sub-
stances are stored before use, where they are used, and where they are stored after being
used and before any residuals are discarded. Since many contaminant release locations occur
from low points in buildings, highlighting pits, sumps, and floor drains on the map can also
help provide valuable information for pollution prevention efforts (Rogers et al. 2006).
13.3.3 Step 3: Assessing CRFs of Substances Present
The hazardous substances having the highest contaminant risk factors (CRFs) should
now be evaluated. This evaluation helps to prioritize the pollution prevention efforts.
Many facilities and households may have more than 100 different hazardous substances.
Prioritizing is therefore critical to achieve maximum benefit.
As noted in Chapter 10, chromium VI and DNAPL VOCs have the highest CRFs for
groundwater, with PCBs, mercury, chlordane, and PAHs having the highest CRFs for soil.
Concentrating pollution prevention efforts on those contaminants with the potential to
significantly impact groundwater such as chromium VI and DNAPL VOCs will have the
most long-term benefit; Chapter 14 presents these scenarios.
13.3.4 Step 4: Preliminary Assessment of Geologic Vulnerability
Most urban areas have not been geologically mapped, so the details necessary to accu-
rately evaluate the vulnerability at any location may not be available. The suggestions
offered here can help determine if any given area presents enough potential risk to war-
rant a more detailed examination, and whether an aggressive pollution prevention initia-
tive should be pursued:
• Source, location, and type of potable water. Contact the local municipality to
evaluate the source of potable water for the area in question. In addition, inquire
whether there are any groundwater extraction wells of any type within at least a
1.6 km (1 mi) radius of the location being evaluated. If any wells exist, request a
copy of the installation records for further examination.
• Nearest surface water body. Determine where the nearest surface water body is
located with respect to the location being evaluated. Topographic maps (7.5 min)
can help with this procedure.
• Stormwater collection and discharge. The local municipality should have informa-
tion about stormwater collection, its treatment, and the discharge locations for the
area being evaluated.
• General geological conditions. Examining well records could provide valuable
information on soil type, stratigraphy, and depth to groundwater if they can be
obtained in the vicinity of the location being evaluated.
If the source of potable water in the area being evaluated is obtained from groundwater
and extraction wells are nearby, environmental risk should be considered high. In this
case, the geologic vulnerability rating will likely exceed a score of 50, and pollution pre-
vention efforts should become a top priority (Chapter 6). The other factors listed above will
likely require examination and evaluation by a qualified professional before an appropri-
ate geologic vulnerability rating can be determined.