required for this waste generation rate if the landfill is designed for the minimum recom-
mended depth of fill? Determine the engineer's role in site cleanup and in the economic
studies needed for evaluation of available alternatives.
Calculation Procedure:
- Analyze the available treatment technologies for cleaning
contaminated waste sites
Table 3 lists 13 available treatment technologies for cleaning contaminated waste sites,
along with the type of contamination for which each is applicable, and the relative cost of
the technology. This tabulation gives a bird's eye view of technologies the engineer can
consider for any waste site cleanup.
When approaching any cleanup task, the first step is to make a health-risk assessment
to determine if any organisms are exposed to compounds on, or migrating from, a site. If
there is such an exposure, determine whether the organisms could suffer any adverse
health effects. The results of a health-risk assessment can be used to determine whether
there is sufficient risk at a site to require remediation.
This same assessment of risks to human health and the environment can also be used
to determine a target for the remediation effort that reduces health and environmental
risks to acceptable levels. It is often possible to negotiate with regulatory agencies a re-
mediation level for a site based on the risk of exposure to both a maximum concentration
of materials and a weighted average. The data in Table 2 are useful for starting a site
cleanup having the overall goals of protecting human health and the environment. - Make a health-risk assessment of the site to determine
cleanup goals^1
Divide the health-risk assessment into these four steps: (1) Hazard Identification—Asks
"Does the facility or site pose sufficient risk to require further investigation?" If the an-
swer is Yes, then: (a) Select compounds to include in the assessment; (b) Identify exposed
populations; (c) Identify exposure pathways.
(2) Exposure Assessment—Asks "To how much of a compound are people and the en-
vironment exposed?" For exposure to occur, four events must happen: (a) release; (b)
contact; (c) transport; (d) absorption. Taken together, these four events form an exposure
pathway. There are many possible exposure pathways for a facility or site.
(3) Toxicity Assessment—Asks "What adverse health effects in humans are potentially
caused by the compounds in question?" This assessment reviews the threshold and non-
threshold effects potentially caused by the compounds at the environmental concentration
levels.
(4) Risk Characterization—Asks "At the exposures estimated in the Exposure Assess-
ment, is there potential for adverse health effects to occur; if so, what kind and to what ex-
tent?" The Risk Characterization develops a hazard index for threshold effects and esti-
mates the excess lifetime cancer-risk for carcinogens. - Select suitable treatment methods and estimate the
relative costs
The site contains polluted water, solid wastes, dangerous metals, and organic contami-
nants. Of these four components, the polluted water is the simplest to treat. Hence, we
will look at the other contaminants to see how they might best be treated. As Table 3
Copper, David R., "Cleaning Up Contaminated Waste Sites," Chemical Engineering, Aug.,
1989.