4.4.7.5   Short-Term Effectiveness -- Alternative 7

The short-term effectiveness of solvent extraction technology
application involves the effects to on-site workers and
residential communities during implementation.  The technology's
impact on these areas is discussed below.

Worker Safety

The solvents used in extraction are not considered hazardous;
however, they must be stored in appropriate containers with
secondary containment.  Fire hazards could occur because of the
flammable and explosive properties of solvents such as propane. 
All electrical equipment must therefore be explosion-proof, and
all equipment must be spark-proof, and all potential ignition
sources must be eliminated.

Certain chemical hazards are associated with solvent extraction. 
Potential chemical hazards include inhalation, ingestion, and
dermal contact with PCB-contaminated material, solvents, or waste
oil containing PCBs.  Site workers would be provided with
adequate PPE to minimize these risks, and only properly trained
personnel would be involved in site operations.  The specific
protection worn would be determined by the level of dermal and
inhalation protection necessary.  Air monitoring would be
conducted to assist in determining the required level of
protection.  Workers should also be monitored for heat and cold
stress.

Potential Community Exposure

Pretreatment activities required for solvent extraction such as
sizing and screening may cause exposure to contaminants through
fugitive dust emissions.  Dust control measures, such as wetting
the material with water or foam, would be needed to minimize
fugitive dust emissions.  Access to the CTF would be restricted
to authorized personnel to protect the community from accidental
exposure.

Air monitoring would be conducted during solvent extraction to
monitor the impact on site workers and residential communities. 
Air emissions from solvent extraction would be minimal because
the process basically operates in a closed loop.  Vent gases, if
any, would be treated by APC equipment such as carbon filters
prior to discharge to minimize presenting little risk to the
potentially exposed population.

The results of air monitoring conducted during solvent extraction
demonstration tests indicate that air emissions would not be a
significant problem.  During the SITE demonstration of the
B.E.S.T.  system, the ambient air was monitored for organic
vapors.  The maximum limit for organic vapor concentration in the
ambient air was 10 ppm above background levels.  None of the
measurements taken during the B.E.S.T.  system demonstration
exceeded this limit (EPA 1993d).

During the B.E.S.T.  demonstration, vent gases were filtered by
primary and secondary activated carbon canisters, and the TEA
concentration in the air between the two carbon canisters was
monitored daily with reaction tubes.  The maximum limit for the
TEA concentration in the air between the two carbon canisters was
3.5 ppm.  This limit was exceeded twice during the demonstration
test (15 ppm and 30 ppm).  In each instance, the primary carbon
canister was replaced immediately, and the TEA concentration
returned to below 3.5 ppm.  Vent gas TEA emissions were not
measured at over 0.2 ppm at any time during the demonstration
(EPA 1993d).

During the CF System LG-SX pilot-scale demonstration, air
monitoring did not detect "significant" leaks of propane from the
system.  No sudden releases of any of the materials used or
treated in the process occurred.  One "minor" leak was reported. 
It was also reported that results of background air sampling and
personnel monitoring for organic vapors and PCBs were below
detection limits (EPA 1990b).

During the Terra-Kleen Solvent Extraction Treatment System pilot-
scale demonstration, solvent vapors were released during sampling
and biological treatment activities.  The full-scale system
incorporates a closed-loop design to prevent these emissions (PRC
1994a).