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Report - Technical

DATE 21 SEPTEMBER, 1984  TO   CAPT. SHAW, MSO GALVESTON  FROM LT. BAXTER, NOAA
SSC  SUBJECT  MASS BALANCE OF ALVENUS OIL In preparing for the up-coming RRT
meeting, Lt. Ocken has asked questions about the accounting of lost and
recovered ALVENUS oil which should be discussed in detail before the referenced
meeting. At issue is the accuracy with which we are able to account for the oil
lost from the ALVENUS.  Stated mathamatically the mass balance formula is:   T =
R + E + D + S + X  Where  T is the total estimate of oil lost from the vessel, 
R is the total estimate of oil recovered by cleanup,  E is the estimated loss to
evaporation  D is the estimated loss to decomposition ( emulsification, photo- 
oxidation, microbial uptake, etc.)  S it the estimated loss to sedimentation,
and the remaining  portion on the sea wall,  X is the unaccounted factor. The
ability to account for oil spilled is a very difficult task. A brief review of
mass balance calculations from other recent spills shows that on average only 20
to 75% of the lost volume of oil is ever accounted for with any degree of
accuracy. A case in point is the spill of the AMOCO CADIZ in 1978. a very
considerable ammount of time and money was spent in sampling and measurements
specifically designed to aid in an oil mass balance. Of the 233,000 metric tons
(mt) lost in the incident, 75% was accounted for, leaving the fate of the
remaining 25% open to speculation. Oil mass balance estimates are subjective at
best, despite all attempts to present the information in a mathematical format.
 In the case of the ALVENUS spill extensive resources were not committed to
collecting data for a mass balance. Rather, estimates and analytical values
obtained for other purposes were adapted and used in a mass balance equation.
Many of these values were adequate for the intended purpose, but are not
accurate enough for a signifigant mass balance computation. With this in mind
the following details how specific values for the above equation were derived,
and the relative strength of the figures. The total spill volume, T, is usually
the most accurate value of the equation. In the case of the ALVENUS the total
loss was reported as 66,572 barrels which converts to about 10,000 mt (see ref
2).  The total recovered, R, is arrived at by averaging estimates of oil removed
from the beach as a sand-oil mix, sorbed in the vicinity of the sea wall and
from other removal efforts. Many of these figures are adequate for the intended
purpose, that is guiding the removal of oiled sand from the beaches. They are
not accurate enough, or statistically valid for a comprehensive mass balance. A
range of values between 4600 and 6100 mt is suggested for a total oil removed
from Galveston Island beaches to pit disposal sites (see ref 2). It is estimated
form removal records that 350 mt of oil from highly oiled sand was disposed of
at the BFI facility , and that 750 mt was left on Bolliver Island in windrows
above the vegitation line (see ref 4). Thus the total recovered may range
between 5700 and 7200 mt.  The loss to evaporation, E, has been estimated based
upon the results of anaylitical chemistry and a weathering model performed by
S.A.I.(see ref 3). Consultation with Dr. Ed Overton of LSU and Dr. Jim Payne of
S.A.I. has provided a value for evaporation of 20%, by empiricle estimate.  The
loss to decomposition, D, is quite low. Emulsification of the oil was noted at
sea, but was later reversed as the oil beached (see ref 3). Both micobial and
photo-oxidation processes are thought to be quite low since the fractions most
often involved in these processes are already in low proportion in the Merey and
Pilon crudes (see ref 3). A value of 5% has been selected based upon the
emulsification-deemulsification data presented (see ref 3).  The data on
viscosity in reference 3 should not be used as an indication of evaporation.
Viscosity is a complex phenomenon which combines emulsification, evaporation,
polymerization and other processes in a non-linear relationship. Thus, changes
in the viscosity of a spilled oil are of very limited value in understanding
changes to that oil over a period of time. The loss to sedimentation and
unremoved oil, S, may range between 500 and 1000 mt. These figures are very
subjective, and are the "weak link" in the estimate. They are based on the
results of beach profiling, observed beach re-oiling events and visual estimates
of oil seen over the spill area (see ref 2, 4 and 5). In particular, the
profiling was conducted to address the natural beach processes, with oiled
sediment observations made as an aside. As the natural erosional-depositional
cycle "works" the sedimented oil in the beach these values will change. Thus the
mass balance may be calculated using the high and low range values, ignoring for
the moment any statistical sampling or estimation variations to the input
values. low range-  10,000 mt = 5700 mt + 2000 mt + 500 mt + 500 mt + X  = 8700
+ X  high range-  10,000 mt = 7200 mt + 2000 mt + 500 mt + 1000 mt + X  = 10,700
+ X In the first case we have 1300 mt unaccounted for, while in the second we
have gained 700 mt of oil above what was lost from the vessel.  What we can say
is that we have accounted for a signifigantly higher proportion of ALVENUS oil,
compared to other crude oil spills. Within the limits of the data we can feel
reasonably sure that any remaining unaccounted oil is contained in estimating
errors among the various catagories. References:  1. The Fate of Amoco Cadiz
Oil.  Gundlach, Boehm, et.al., Science, Vol. 221, 8 July, 1983.  2. Calculations
of Removed Oil and Sediment.  RPI, NOAA Spill Report Number 22, ALVENUS Oil
Spill, Aug. 28, 1984.  3. Summary of Chemical Analysis and Physical
Properties...  SAI, Report to SSC, Sept. 4, 1984.  4. Preliminary Oil Budget for
ALVEWNUS Oil.  Pavia, SSC Report to OSC, Aug.14, 1984.  5. Field Notes and
Observations During Beach Profile  Gundlach, not compiled.