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M/V Alvenus

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.