Page 164 - Pipeline Risk Management Manual Ideas, Techniques, and Resources

Product hazard 71141
Products that are not specifically listed with an EPA- linked to the solubility, and the lighter products are usually
assigned RQ but do fit the definition of hazardous are now more soluble. However, it can also be generally stated that
divided into categories of volatile or nonvolatile. These prod- the lighter petroleum substances may more easily penetrate
ucts that do not meet the definition of “hazardous substance” the soil and reach deeper groundwater regions. This is also a
set forth above OR are not volatile AND do not require a formal solubility phenomenon. We now have conflicting results of
cleanup are assumed to have a RQ designation of “none” (see a single property. To adequately include the property of den-
Figure 7.4). sity (or solubility), we would have to balance the benefits of
Following the “hazardous substance” AND volatile branch quicker degradation with the potential of more widespread
of the flowchart (Figure 7.4), we now assess these volatile environmental harm.
substances. Highly volatile products of concern produce We have now established a methodology to assign a rank-
vapors, which when released into the atmosphere, cause poten- ing, in the form of an RQ category, for each pipeline product.
tial acute hazards, but usually only minimal chronic hazards. An important exception to the general methodology is noted.
Common pipeline products that will fall into this category If the quantity spilled is great enough to trigger an RQ of
include methane, ethane, propane, ethylene, propylene, and some trace component, this RQ should govern. This scenario
other liquefied petroleum gases. These products also meet the may occur often because we are using complete line rupture
definition of “hazardous substances” set forth above. as the main leak quantity determinant. For example, a crude
We can assume that the bulk of the hazard from highly oil product that has 1% benzene would reach the benzene RQ
volatile substances occurs in leaks to the atmosphere. We number on any spill greater than 1000 pounds. This is because
assume that all leaks of such products into any of the three the benzene RQ is 10 pounds and 1% of 1000-pound spill
possible environmental media (air, soil, water) will ultimately of product containing 1% benzene means that 10 pounds of
cause a release to the air. We can then surmise that the hazard benzene was spilled.
from these highly volatile liquids is mostly addressed in the To easily account for this general exception to the RQ
atmospheric dispersion modeling analysis that will he per- assignment, the evaluator should start with the leak quantity
formed in the acute leak impact consequences analysis. The calculation. She can then work from the CERCLA list and
chronic part ofthis leak scenario is thought to be in the potential determine the maximum percentage for each trace component
for (1) residual hydrocarbons to be trapped in soil or buildings that must be present in the product stream before that compo-
and pose a later flammability threat, and (2) the so-called nent governs the RQ determination. Comparing this to an
“greenhouse” gases that are thought to be harmful to the ozone actual product analysis will point out the worst case compo-
layer of the atmosphere. These threats warrant an RQ equiva- nent that will determine the final RQ rating. An example illus-
lent of 5000 pounds in this ranking system. trates this.
This leaves the less volatile hazardous substances, which
also need an assigned RQ. Included here are petroleum prod- Example 7.2: Calculating the RQ
ucts such as kerosene, jet fuel, gasoline, diesel oil, and crude
oils. For spills ofthese substances, the acute hazards are already An 8-in. pipeline that transports a gasoline that is known to
addressed in the flammability, toxicity, and reactivity assess- contain the CERCLA hazardous substances benzene, toluene,
ment. Now, the chronic effects such as pollution of surface and xylene is being evaluated. The leak quantity is calculated
waters or groundwater and soil contamination are taken into from the line size and the normal operating pressure (normal
account. pressures instead of maximum allowable pressures are used
Spills of nonvolatile substances must be assessed as much throughout this company’s evaluations) to be 10,000 pounds.
from an environmental insult basis as from an acute hazard This calculated leak quantity is now used to determine com-
basis. This in no way minimizes the hazard from flammability, ponent percentages that will trigger their respective RQs for
however. The acute threat from spilled flammable liquids is this spill:
addressed in the acute portion of the leak impact. The longer
term impact of spilled petroleum products is obtained by Benzene (RQ = 10): 10/10,000 = 0.001 = 0. I%
assigning an RQ number to these spills. It is recommended that Toluene (RQ = 1000) 1000/10,000=0.1= 10%
these products be classified as category B spills (reportable Xylene (RQ= 1000) 1000/10,000=O.I = 10%
quantities of 100 pounds) unless strong evidence places them in
another category. This means the RQ equivalent is 100 pounds. The evaluator can now look at an actual analysis to see If the
An example of evidence sufficient to move the product down actual product stream exceeds any ofthese weight percentages.
one category (more hazardous) would be the presence of a sig- If the benzene concentration is less than 0.1 % and the toluene
nificant amount of category X or category A material (such as and xylene concentrations are each less than lo%, then the RQ
methylene chlonde--category X). This is discussed further is set at 100 pounds, the default value for gasoline. If, however,
below. Evidence that could move the petroleum product into a actual analysis shows the benzene concentration to be 0.7%,
category C or category D (less hazardous) would be high then the benzene RQ set at 10 pounds governs. This is because,
volatility or high biodegradation rates. more than 10 pounds of benzene will be spilled in a 10,000-
To make further distinctions within this group, more com- pound spill of this particular gasoline stream.
plex determinations must be made. The value of these addi-
tional determinations is not thought to outweigh the additional Gasolines generally are rich in benzene, but they are also
costs. For instance, it can perhaps be generally stated that the fairly volatile. Heating oils, diesel, and kerosene are more per-
heavier petroleum products will biodegrade at a slower rate sistent, but may contain fewer toxicants and suspected carcino-
than the lighter substances. This is because the degradability is gens. Crude oils, of course, cover a wide range of viscosities