Perspective on validating the natural resource damage assessment model system

Oil & Chemical Pollution 5 (1989) 217-238

Perspective on Validating the Natural Resource Damage Assessment Model System

Thomas A. Grigalunas, James J. Opaluch Department of Resource Economics, University of Rhode Island, Kingston, Rhode Island 02881, USA

Deborah P. French & Mark Reed Applied Science Associates, Inc., 70 Dean Knauss Drive, Narragansett, Rhode Island O2882, USA

ABSTRACT This paper describes a preliminary effort to validate the Natural Resource Dam age Assess men t Model fo r Co asta 1a n d Ma rin e En viro n men ts (NR DAM/ CME). After describing the general requirements that the model should meet, the problems inherent in validating the NRDAM/CME by a retrospective comparison with the results of field studies are reviewed. Due to these problems, an order-of-magnitude standard of accuracy is argued to be appropriate. Comparisons of the model results with those of selected field studies suggest that the NRDAM/CME provides reasonable results given this standard. In light of the fact that this preliminary validation effort is based on the use of only readily available information for a few studies, additional efforts are in order to validate the model and refine it, as appropriate.

1 INTRODUCTION Attempts to validate the N R D A M / C M E (Reed et al., 1989) can proceed along several lines. Clearly the concepts a n d theory e m b e d d e d in the N R D A M / C M E s h o u l d be a p p r o p r i a t e for the p r o b l e m s a d d r e s s e d a n d s h o u l d reflect the state o f the art. Further, the specification o f the 217 Oil & Chemical Pollution 0269-8579/89/$03.50 © 1989 Elsevier Science Publishers Ltd, England. Printed in Ireland.

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equations, parameters and data used in the model should be the best estimates available in the literature. Based on comments received during an extensive public review process, and revisions made to the model in response to those comments, the N R D A M / C M E would appear to meet these general requirements. From another viewpoint, the N R D A M / C M E can be validated by comparing the model's estimates of damages for various spills in a variety of different environments. For example, a reasonable model should result in damages which increase as a spill size increases, all else being equal. In this regard, the results shown in Section I.G of Volume I of the technical documents (Economic Analysis, Inc. and Applied Science Associates, 1987) and in companion papers in this issue appear reasonable. Typically damages are very small or negligible for very small spills and increase with spill size. Further, for a given spill, damages generally are higher for estuarine environments than for marine environments, as would be expected, given the typically higher levels of biota and shallower water depths of estuaries as opposed to the open ocean areas. However, validation of such a complex model requires a greater effort than simply examining the results for reasonableness. Ideally, it would be preferable to validate the N R D A M / C M E retrospectively, by comparing the results obtained through use of the model with the results of carefully documented case studies of spills in the coastal and marine environments. In particular, it would be preferable to compare the detailed results of actual case studies in the literature with the results of the physical fates, biological effects and economic damages submodels of the N R D A M / CME, given the specific characteristics of the incidents reported in the individual case studies. Through such a process, it would be possible to examine situations where the results differed significantly or where they coincided. It then may also be possible to explain why the results were similar or different and, on this basis, to refine the N R D A M / C M E or its data bases, as appropriate. This type of analysis is implicit in Section 301 (c)(3) of C E R C L A which requires that the type A and type B damage assessment regulation be reviewed and revised as appropriate every two years. This paper provides a preliminary attempt to validate the N R D A M / CME model and addresses some of the issues which arise when trying to validate the model using a retrospective approach. The principal conclusion is that it is probably not possible to provide a complete and definitive validation of the N R D A M / C M E model in its entirety by comparing it with the results obtained from past case studies, due to a n u m b e r of difficulties to be discussed in detail below. In combination,

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the problems are serious enough so that generally speaking, the results of available field studies cannot be presumed to be 'correct'. By virtue of this fact, case studies rarely, if ever, can be used to provide a clear standard against which to compare the results of the N R D A M / C M E . Nonetheless, comparisons with case studies may provide useful qualitative insights into the reasonableness of parts of the N R D A M / C M E model and are clearly a necessary part of the process of review and revision of the type A natural resource damage regulations. This paper is organized as follows. First, in Section 2, the problems inherent in attempts to validate the N R D A M / C M E using a retrospective approach are described. Secondly, these problems are illustrated in Section 3 through a brief review of selected case studies. In each instance, the results presented in the case studies are compared with the measures provided by the N R D A M / C M E in order to assess the reasonableness of the N R D A M / C M E relative to the case study, and vice versa. The final section presents a summary and concluding comments. 2 PROBLEMS I N H E R E N T IN A T T E M P T I N G TO VALIDATE THE N R D A M / C M E T H R O U G H COMPARISON WITH CASE STUDIES Attempts to validate the N R D A M / C M E by means of comparison with the results of the past case studies present several major problems. These problems include: (1) Relatively few spills have been comprehensively studied in the field. Those which have been most heavily researched have primarily been major, highly visible incidents and not the relatively small incidents for which the model was designed and a type A assessment most often will be employed. (2) Very few field studies of spills have involved a systematic damage assessment within a framework that specifically integrates physical fates, biological effects and economic damages as does the N R D A M / C M E . Hence, it is difficult to find studies against which the N R D A M / C M E model, as a whole, can be compared. (3) Those case studies which have included an economic assessment of damages generally have been seriously limited by the lack of biological information and, moreover, have employed economic concepts and data which differ considerably from those incorporated in the N R D A M / C M E . (4) Assessments of damages from spills in the marine and coastal environments in the past often have taken place in an adversarial setting, in which the objectivity of the analysis may be open to

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question. Under such circumstances, the interpretation of comparisons between the measure of damages obtained from case studies and from use of the N R D A M / C M E becomes problematical. (5) The chance nature of spills confronts researchers with severe logistical problems in terms of launching a research program quickly before evidence of the spill is lost, for example, by being dispersed or eaten by scavengers. The importance of this final point should not be underestimated. As described by the National Research Council of the National Academy of Sciences in a recent comprehensive review (1985; p. 549): Scientific studies of tanker spills present several problems for the serious s c i e n t i s t - - a w e s o m e difficulties in field sampling, and readiness of personnel and equipment. Spills are not anticipated, and in the past, personnel and equipment have seldom been readily available. Also, most spills occur in areas that have not been studied previously, and adequate controls are rare. Spills frequently occur in weather conditions that make sampling difficult or impossible. These problem s are c o m p o u n d e d in offshore spills, where sampling becomes much more difficult, background data are less available, and the expense of large ship operations is difficult to finance on short notice. Concerning the potential problems in quantifying possible injuries to fisheries from oil spills, the National Research Council review (1985) points out (p. 424): If any large mortalities [to fish] do occur, they probably occur in the egg and larval stages found in the surface waters. Being more sensitive than the adult stages, eggs and larvae may have been killed in large numbers following spills. However, such kills are extremely difficult to document, simply because these fragile life stages are difficult to sample, since the dead fall out of the water column and decompose within hours, becoming unrecognizable tissue debris. The same difficulties in quantifying biological injuries also apply to potentially more visible injuries, such as birds killed by oil spills. Only a fraction of the birds killed by a spill can be expected to be observed (National Research Council, 1985; Page & Carter, 1986). For example, the National Research Council (1985) concludes: An accurate estimate of the n u m b e r of seabird casualties from oil pollution is not now and may never be possible. The only firm figures available are from counts of oiled birds found on shore surveys, but

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these are subject to severe limitations imposed by the intensity of the search, accessibility of the shore, reporting efficiency by cleanup crews, etc., and there is often doubt about the proportion of corpses found on beaches that were in fact oiled after death. A very large and probably significant source of error is the u n k n o w n proportion of oiled birds that die at sea but which never reach the coast, thereby escaping the shore surveys. The evidence suggests that, in fact, 30% or fewer of the bird corpses drift ashore (Hope-Jones et al., 1978). Estimates of actual losses in major incidents are therefore usually little more than informed guesses. They do probably indicate the orders of magnitude, however, whether hundreds, thousands, or, exceptionally, tens of thousands. In the light of the above observations, it is reasonable to conclude that even extensive field studies of spills will have difficulty providing accurate estimates of injury from spills. Even detecting injury to adult fish is difficult, because of the problems inherent in studying the effects of spills under realistic conditions. Detecting injury to larvae or via the food chain remains elusive. This is particularly true for offshore spills or spills which take place during severe weather conditions. In this regard, the N R D A M / C M E offers a n u m b e r of advantages. It is a simplified approach which simulates the incident and its consequences over a period which may involve several years. The model allows for consideration of a variety of natural resource damages arising through complex processes which rarely, if ever, could reasonably be expected to be quantified in the field. In summary, validation of the N R D A M / C M E and improvements of the model and its databases through comparison with the results of past incidents is desirable. However, given the many problems faced by investigators in field studies, and given the different data and methodologies generally used, it is not clear what the results of this type of retrospective validation for the model as a whole would mean. As noted, in-field assessment studies face m a n y serious problems, and such studies rarely have integrated economics with physical fates and biological effects research. Finally, those studies which have included economics have done so on a limited basis, have used concepts which differ in important ways from those employed in the N R D A M / C M E and may not always be objective. In combination, these factors make it difficult to argue that the results of case studies of past spills are 'correct' and, therefore, are the appropriate standard against which to compare the results of the NRDAM/CME. Although it does not appear to be possible to use the results of case

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studies of incidents to provide a definitive validation o f the entire N R D A M / C M E , it is possible to compare selected case study results with those obtained through use of the model. Such comparisons are useful in documenting the importance of the problems with retrospective validation suggested above. Given these difficulties, it seems that an order of magnitude standard of accuracy may be expected between estimates of damages based on field investigation and estimates provided by the N R D A M / C M E model. For the validation cases described below, this order of magnitude standard is employed. Thus, cases where the N R D A M / C M E model results fall well within an order of magnitude of field study estimates of damage are viewed as confirming the results. Cases where results deviate by nearly an order of magnitude are viewed as open to question, while results which deviate by more than an order of magnitude are viewed as inconsistent. This type of comparison may be useful in qualitatively assessing the N R D A M / C M E .

BRIEF C O M P A R I S O N OF T H E RESULTS OF SELECTED CASE STUDIES W I T H T H E RESULTS OBTAINED WITH THE NRDAM/CME In this section selected case studies are reviewed and compared with the results obtained through use of the N R D A M / C M E . The case studies considered meet three requirements: (1)they are specific incidents as opposed to long-term, continuous discharges or releases, (2) they can be reasonably considered within the type A framework, and (3)they are reasonably well documented. The results for the case studies presented below are only approximate applications of the N R D A M / C M E to these incidents, since in many cases available reports describing the incident were lacking important information and a n u m b e r of judgments had to be made, as described below. Because of the lack of complete information, approximations rather than precise values are employed in setting the N R D A M / C M E environmental parameters.

3.1 An example ofa nearshore spill: Long Island Lighting Company spill, Island Park, New York This incident took place on 10 February 1985, when a spill from a storage tank of No. 2 fuel oil was discovered. A containment dike surrounding the tank subsequently leaked, and about one-half of the 400 000 gallons (1348 t) spilled escaped from the containment area. According to Ott (1987),

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about one-half of this escaped oil soaked into the soils at the facility, and the other half(about 100 000 gallons, 337 t) flowed into the shallow-water channels dividing the facility. Containment booms were rapidly deployed, but the oil could not be totally contained because of subsequent high winds. Sampling and inspection studies carried out on site following the spill showed no effects outside the immediate channel area (Milhous & Gross, 1985). Within the channel area, short-term effects included some mortality to soft-shell clams and oiling of 90 waterfowl, none of which survived. The major long-term effect was the lack of re-emergence of salt marsh vegetation along heavily oiled areas, about one-half acre (0.202 ha) in size. No attempt was made to measure the resulting long term, indirect losses. However, the vegetation in the area is expected to recover within a few years (Milhous & Gross, 1985). In general, the results presented in the Gross study suggest relatively modest short-term biological injuries from this spill, although no assessment of damages was made. From the diagram of the spill site provided by Ott (1987), the spill into the shallow channel (Simson's Channel) was simulated using the N R D A M / C M E with the following study area: +X, 1400 feet (427 m) to land; - X , 800 feet (244 m) to land; + Y to - Y , 100 feet (30 m). The depth was assumed to be 2.0 m, the tide 0.5 m s -~ in the X direction only (no perpendicular component), and no mean ocean current was assumed. The N R D A M / C M E estimated that 335 metric tons of the spill would come ashore within the day of the spill. Subtidal losses estimated by the N R D A M / C M E included 50 waterfowl killed by oiling, which may be compared with the 90 oiled waterfowl recovered from the field after the incident. Subtidal fishery losses amounted to 11 pounds (5 kg) of lost catch, with $3 in value. Thus, the subtidal losses estimated by the N R D A M / CME agree well with the field assessment of impact. The intertidal portion of the spill was re-run with the N R D A M / C M E , using the same initializing conditions as used by Ott (1987). Other specific environmental parameters used were air temperature (1.7°C) and wind speed (8.9 m s -~) based on incident-specific information obtained from Gross, A. C. (pers. comm., 18 February 1987). The N R D A M / C M E results indicate reasonably large damages of $160 141 for the intertidal portion of the spill. Most of the damages ($130 266) are a result of injury to shorebirds: a direct kill of 1044 birds and an indirect kill (via lost food supplies) of 8197 additional birds were indicated. The fishery damages ($29 875) were attributable to injury to decapods (e.g. blue crabs) which the model quantified over a period of several years. The N R D A M / C M E indicated a total of 1 165 500 kg of saltmarsh vegetation production also was lost due to the spill. This is

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equivalent to the loss of productivity of 2.6 acres (1.05 ha) for eight years, the length of time effects remained in the marsh, according to the NRDAM/CME. One problem which arises in attempting to compare the results of the Gross study with the N R D A M / C M E results is that the Gross study was carried out over a relatively short period of time and did not consider indirect losses due to lost vegetation. Hence, it is difficult to infer longterm biological injuries and, therefore, these losses could be understated in the field assessment. Nonetheless, it appears that in this instance the N R D A M / C M E agrees with what field information is available for the subtidal damages. The intertidal damages estimated by the N R D A M / CME are substantial but remain unverified.

3.2 An example of an estuary spill: The Arco Anchorage tanker spill, Port Angeles, Washington

3.2.1 Summary of the incident On 21 December 1985 theArcoAnchorage, en route to a petroleum refinery at Cherry Point, Washington, ran aground spilling 5690 barrels (239000 gallons) of North Slope crude oil. Within about two hours of the spill the first skimmer vessels and a containment boom were dispatched to Port Angeles; however, because heavy fog conditions hampered air travel along m u c h of the West Coast, arrival of the Arco spill response team from Long Beach, California was delayed. Nonetheless, over time an active response, clean up and recovery operation was carried out. Of the 5690 barrels spilled, about 55% (3126 barrels) was recovered (US Coast Guard, 1986). The remainder, some 2564 barrels, was unaccounted for and evaporated into the atmosphere or was taken up in the water column or in bottom or shoreline sediments.

3.2.2 Summary of damage assessment study The Arco Anchorage spill was reviewed in detail by the US Coast Guard On-Scene Coordinator (OSC) (US Coast Guard, 1986), and a marine resource damage assessment report was prepared by the State of Washington's Department of Ecology (1986). The OSC report contains primarily qualitative information concerning the effects of the spill; however, a detailed analysis of damages is contained in the State of Washington's report. Summarized below are the methodology and data employed and the resulting estimates of damages for the two categories of natural resource damages reported in the Washington study, clams and what are referred to in the study as waterbirds.

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3.2.2.1 Clams. This category includes butter clams, native littleneck, horse clams and macoma and cockles. Estimates of biological injury were based on a survey of the areas affected by the oil spill. While no direct mortality was observed, the clams were tainted, and it was believed that the biological stress caused by the spill 'could take the form of anomalous decreases in populations of affected organisms' (State of Washington, 1986). Because of the spill, 20 470 m 2 of clam grounds were closed from 21 December 1985 to 1 March 1986. An estimated 12 468 pounds (5655 kg) of clams were affected because of the spill (L. J. Kittle, Jr., pers. comm., 23 December 1986; State of Washington, 1986). In order to assess damages, recreational clamming values ranging from $1-39 to $2.31 (in 1986 dollars) per pound ($0.63-$1.05 per kg) were applied, using the numbers presented in Stokes (1979). It should be noted that these unit values are based on commercial prices since recreational values were unavailable. Multiplying these values by the number of pounds (or kg) of each species estimated to have been affected, the aggregate clam losses amounted to $20 356.40 (State of Washington, 1986). 3.2.2.2 Waterbirds. This category encompasses ducks and 'marine fowl' (loons, grebes, cormorants, rails, shorebirds, gulls and alcids). The N R D A M / C M E divides these waterbirds into three categories: waterfowl, shorebirds and seabirds (Economic Analysis, Inc. and Applied Science Associates, 1987). According to the damage assessment report, it was documented that 1917 oiled waterbirds were collected, of which 1562 were alive and the remaining 355 were dead. The documented number of birds oiled, 1917, judgementally was increased in the State's damage assessment report in order to account for the birds which were believed to have died from oiling but could not be observed. By assuming a 50% rate of recovery for injured birds, it was estimated that, in total, 4000 waterbirds were oiled and died (State of Washington, 1986). Hence, despite the considerable effort made by on-scene investigators to assess damages, their apparent inability to quantify accurately biological injuries to birds compelled them to account for unobserved bird losses by approximately doubling the number of injured birds observed. To assess the value of the lost waterbirds, the authors of the marine damage assessment report adopted unit recreation (hunting) values presented in an earlier report by Stokes (1979), inflated to 1986 dollars using the Consumer Price Index. It should be noted here that the State of Washington analysis, unlike the NRDAM/CME, includes no viewing value. The three 1986 unit waterbird values used in the report are $5.53,

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$9.45 and $11.03. According to the Stokes (1979) report, these values were determined as follows: Waterfowl values are based on a study by Hammack of duck hunting in the Pacific Flyway. 'High quality' waterfowl species are evaluated at $5.63 each at 1976 prices. Geese are evaluated at three times this value and 'low quality' waterfowl at one half. The high unit value of$11.03 used in the State of Washington damage assessment report is simply the 1976 recreational (hunting) value of $5-63 inflated to 1986 dollars, while the low unit value of $5.53 is one-half of the 1976 value of $5.63 restated in 1986 dollars. Finally, the intermediate value used in the damage assessment report is $9.45. The $9.45 unit value is based on the 1976 value of $4.82, the average of the $5.63 recreational value plus the estimated replacement cost of $4.00 per bird for the species concerned (Stokes, 1979), inflated to 1986 dollars. Eighteen species of ducks were represented in the damages. The majority (229) of the 475 ducks injured were white-winged scoter (State of Washington, 1986). As noted above, the lost ducks were valued at from $5.53 to $11.03 each, depending upon the species. Using this approach and the relevant numbers for each species, aggregate duck losses were estimated to be $3 681.39 in 1986 dollars (State of Washington, 1986). All of the marine birds were valued at $5.53 per bird, one-half the basic duck value of $11.03. Using this unit value, the total estimated losses for marine birds amounted to $8 892.24 (State of Washington, 1986, p. 92). In summary, the Arco Anchorage oil spill resulted in apparent biological injury amounting to 67 892 clams (12 468 pounds, 5655 kg). In addition, some 4000 birds were estimated to have been contacted by the oil. Of these, an estimated 2083 died as a result of the spill. Total damages presented in the damage assessment report amounts to $32 930.03 (=$3681-39 + $8892.24 + $20 356.40). Note that this figure excludes the loss of 1243 birds which were processed in the bird cleaning station but subsequently died. Including this loss in the damage assessment would lead to bird losses somewhat less than double the $12 573.63 actually assessed, resulting in total damages of about $45 thousand. It should be pointed out that in the US Coast Guard On-Scene Coordinator's report the cost estimate for this spill is reported to be $12 million, $7 million for cleanup and $5 million for 'liability claims'. However, the basis of the liability claims estimate is not indicated. 3.2.3 Summary of the information used in the NRDAM/CME A natural resource damage assessment for the Arco Anchorage crude oil spill was carried out using the NRDAM/CME model. The parameters and responses used to run the NRDAM/CME are described below.

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The incident was assessed as a spill on 21 D e c e m b e r 1985 of 774 metric tons of P r u d h o e Bay crude oil (CAS # 0 0 0) in the subtidal, estuarine e n v i r o n m e n t of the C o l u m b i a n Province on a sand bottom. A water depth of 25 m was used for the subtidal spill, with no pycnocline. The air temperature was 4.4°C (L. J. Kittle, Jr. pers. comm. 23 D e c e m b e r 1986). The w i n d speed was 3.2 m s -~ from the south. The m e a n surface current was 0.7 knots to the west. L a n d boundaries were established at 15 k in the - X direction, a n d 0.5 a n d 15 k, respectively, in the +Y a n d - Y directions. A b o u n d a r y of 500 k was set in the + X direction. The spill was a s s u m e d to reach shore in 36 h, the approximate time which elapsed before the oil came ashore (L. J. Kittle, Jr. pers. comm., 18 D e c e m b e r 1987). Because a significant portion of the oil struck the shoreline, intertidal damages also were assessed. A n intertidal spill of the same oil was run for an estuary with a cobble shoreline type for the C o l u m b i a n Province. The spill date was set at 23 D e c e m b e r 1985. The air temperature of 4.4°C a n d the wind speed of 3.2 s-1 used for the subtidal spill also were used for the intertidal spill. As indicated previously, three c l a m m i n g areas extending over 20 470 m 2 were closed from 21 D e c e m b e r 1985 to 1 March 1986. Hence, w h e n using the N R D A M / C M E for the intertidal case, losses were measured using a 70-day closure of an intertidal area for mollusc harvesting. As noted, some 55% of the spilled oil (425 metric tons) was recovered from the surface a n d shoreline of the affected areas. Recovery at different levels of activity took place over an extended period, b e g i n n i n g shortly after the time of the spill. However, almost half of all the spilled oil cleaned up was recovered within several days, mostly at sea; a n d most of the spill was cleaned up by 3 January 1986 (L. J. Kittle, Jr., pers. comm., 1 December 1986). For the purposes of using the N R D A M / C M E , it was a s s u m e d that three-fourths of the oil cleaned up was removed from the surface a n d one-fourth from the shoreline. All cleanup from the surface (41% of the oil spilled)was assumed to have occurred 1.5 days from the date of the spill; the shoreline cleanup of 14% of the oil spilled (109 metric tons) was assumed to take place seven days after the spill.

3.2.4 Comparison of the case study results with NRDAM/CME results 3.2.4.1 Injuries and damages to birds. W h e n the N R D A M / C M E was used in this case, the total direct kill of all birds, estimated as 5358, may be c o m p a r e d with approximately 4000 in the State of W a s h i n g t o n study, although the 1913 birds processed through the bird rehabilitation facility were not counted as part of damages by the state. Hence, the N R D A M /

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CME quantification of injury to birds is one-third higher than the estimate in the State study, which is well within the order of magnitude standard of accuracy. Examining the categories of birds killed, the NRDAM/CME results indicate that 977 waterfowl and 4381 seabirds were killed. Assuming that 50% of all dead birds of both categories are observed, the corresponding estimates in the State of Washington damage assessment study would be 950 for ducks and 3216 for seabirds. Hence, the NRDAM/CME estimated kill of waterfowl is extremely close to that of the Washington assessment study, and the NRDAM/CME results indicate that about one-third more seabirds were killed than was estimated by the State's damage assessment. The State of Washington's (1986) estimate of damages for the birds killed was $12 574. As described above, waterfowl damages were based on lost hunting value, adjusted by the 'quality' of the ducks killed. For all 0ther birds, the value was set at $5.53, one-half of the basic unit duck levy. In comparison, damages from injury to birds from the NRDAM/CME totalled $104 913, larger almost by a factor of nine. Why are the NRDAM/ CME damages for injury to birds so much higher than in the State's study? The major reasons include: (1) All estimated dead birds were not included in the State of Washington's assessment. Inclusion of the birds which were processed in the bird cleanup center would result in approximately double the State's assessment; (2) the number of birds killed is about a third higher in the NRDAM/ CME than in the State report; (3) the NRDAM/CME includes lost viewing value for each year over the period of resource recovery, while the State's approach does not include any viewing losses. Thus, the NRDAM model used a higher value for birds than did the State of Washington. In summary, the NRDAM/CME measure of injury to birds is quite close to that estimated by the State of Washington, and well within the order of magnitude standard of accuracy. However, the NRDAM/CME measure of economic damages from injury to birds is over eight times larger than that arrived at in the State of Washington's damage assessment study. Most of this difference is due to Washington State's excluding from their assessment birds which were brought to the cleanup center, but subsequently died, and the fact that the Washington State study includes no viewing value for birds, while the hunting values per bird are comparable for the two approaches.

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3.2.4.2 Injuries and damages to clams (molluscs).The State's damage assessment study found no evidence of mortality to clams. However, tainting was found, and it was believed that one season's spawning would be lost because of the oil spill. As noted, 20 470 acres (8284 ha) of clam beds were closed for 70 days. Damages of $27 157 were assessed for the State's estimated loss of 12 468 pounds (5655 kg) of clams. Using the N R D A M / C M E , some short-term, direct injury (4264 pounds, 2097 kg) to molluscs also was measured. However, in addition to the short-term losses, long-term injuries resulted from the residual amount of oil in the sediments after cleanup of the intertidal area and from the kill of mollusc larvae. The N R D A M / C M E results indicated a total lost catch over a several-year period of 21 606 pounds (9800 kg) and damages of $6766. Two important reason appear to explain why the State of Washington's value for damages to molluscs is higher than that of the N R D A M / C M E ($27 157 versus $6766). First, the State's estimate of damages assumes that all molluscs lost would have been harvested and, moreover, would have been harvested in the year of the spill. Natural mortality and the fishing mortality are not considered in the State study. In contrast, the lost in-situ use value measured in the N R D A M / C M E is a discounted value which recognizes that a fraction of the molluscs killed by the spill would have died in any case in the absence of the spill, and that not all individuals would be caught in a given year. Second, the values of $1.39 and $2.31 per pound ($0-63-$1.05 per kg) used by the State to assess damages greatly exceed the $0-57 per pound ($0.26 per kg) used in the N R D A M / C M E . The State of Washington's value per p o u n d is a 'recreational' value - based on judgments that commercial retail values can be regarded as a m i n i m u m recreational value. By comparison, the N R D A M / C M E values lost mollusc catch using a National Marine Fisheries Service ex-vessel price which is used because no acceptable recreational studies of clamming are available. 3.2.4.3 Injuries and damages to other biological resources. The State of Washington measure of damages as a result of the Arco Anchorage oil spill included only clams and birds. In contrast, the N R D A M / C M E results indicate some kills of adult finfish and their larvae and of decapods (a category that includes crabs) in addition to the loss of birds and clams. In the N R D A M / C M E , the damages total $146 669, while the total damage claim by the State is only $32 930.03 attributable to the lost birds and clams. Including lost birds which were processed at the bird cleanup center would increase the State of Washington damage estimate to somewhere around $45 thousand.

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A reasonable explanation for the differences in the measure of damages to finfish between the two approaches is that the NRDAM/ CME methodology has the advantage of using integrated physical fates and biological effects submodels to simulate direct, indirect, short- and long-term injury and damages to finfish and decapods. Thus, while the State's study considers only short-term, direct effects on commercial biota, the NRDAM/CME also includes indirect effects, such as losses through the food chain, and long-term effects, such as future losses due to lost recruitment of larvae. As pointed out earlier, while it is difficult to account for killed birds in field research, it is even harder to observe killed larvae and adult fish. Indeed, despite significant efforts during the period following the spill, the State of Washington apparently was unable to quantify injury to biological resources other than to clams and birds, although some evidence of other injury was found. For example, unusually high mortality rates were found in sampling of surf smelt eggs; however, this mortality could not be definitively tied to the spill, and for this reason was not included in the assessment. Hence, the fact that the NRDAM/CME indicates damages for finfish and decapods, unlike the State study, is not unreasonable and, in fact, is to be expected.

3.2.4.4 Summary of comparison. In the case of the Arco Anchorage crude oil spill, the damages measured through use of the NRDAM/CME ($146 669) are about four and a half times those assessed by the State of Washington ($32 930). In this particular case the difference appears to be explainable in that (1) the State's damage assessment did not include lost birds which were processed in the bird cleanup center, (2) the NRDAM/ CME offers advantages as an operational framework for simulating injuries which could not be observed in the field (kills of juvenile and adult fish, larvae, birds and, to a lesser extent, shellfish) and (3) different concepts were used to value injury to biological resources; in particular, the NRDAM/CME includes viewing value for birds. It should be reemphasized that in applying the NRDAM/CME to this case, only readily available information was used, and some simplifications of this complicated incident were made. A more extensive analysis of this spill might have yielded somewhat different environmental parameters or assumptions for use in the NRDAM/CME and, thereby, might have resulted in somewhat different measures of injury and damages. 3.3 An example of an offshore spill: The San Joaquin Valley crude oil spill

3.3.1 Summary of the incident This January 1986 crude oil spill polluted beaches and injured wildlife along a stretch of the central California coast ranging from Salmon

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Creek, Sanoma County to Point Lobos, Marin County. The estimated 616 barrels (25 800 gallons or 84 metric tons) of crude oil spilled is believed to have as its source a tank barge under tow, which later was discovered to have a hatch cover out of place. The oil is believed to have been lost along the route taken by the barge during a period of rough seas at the end of January, during the early part of its voyage (Page & Carter, 1986). This route was about 15 k offshore. Approximately 100 barrels of the lost oil were removed from beaches along the affected shoreline. During and immediately after the spill, winds were from the southsoutheast and ranged from 15 to 40 knots (Page & Carter, 1986).

3.3.2 Summary of the biological injuries to birds study The spill and its estimated effects on birds were extensively studied by scientists at the Point Reyes Bird Observatory (Page & Carter, 1986). Although the scientists involved did not attempt to measure economic damages, they did undertake field research to observe and quantify the n u m b e r of oiled birds washed ashore. I n a d d i t i o n , they estimated the total n u m b e r of birds killed (observed plus unobserved). A total of 10 577 birds were estimated to have been killed or debilitated by the spill. This includes 3364 debilitated, live oiled birds which were collected from beaches, 5880 dead oiled birds estimated to have washed up on beaches, and 1533 birds estimated to have been killed but lost at sea (Page & Carter, 1986). The authors indicate that their estimate of 10 577 birds affected by this spill is conservative because their analysis was confined to a shorter time frame and a smaller area than was likely to have been encompassed by the spill and because they only considered a subset of the bird species affected by the spill (Page & Carter, 1986). The precise timing and location of the spillage involved in this incident is unknown, although through a reconstruction of events, informed judgments were reported in the study by Page & Carter (1986). As noted, this crude oil spill is believed to have occurred along the route of the tank barge during the rough seas which characterized the first part of the voyage (Page & Carter, 1986). The area traversed during the first part of the voyage extended from about Pigeon Point to just south of Point Sur.

3.3.3 Summary of data used in the NRDAM/CME For the purposes of using the N R D A M / C M E for this incident, the spill was assessed as a heavy crude oil (CAS # 0 0 5) spill occurring in a subtidal environment of the Californian Province on 29 January 1986. Because the precise location of the one or more spills associated with this incident is unknown, it was assumed that all 84 metric tons of the oil was spilled in one general location. This location was taken to be 15 km from

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shore, approximately 50 km down the coast from the G o l d e n Gate Bridge. This is roughly the center point of the estimated route that the vessel was on when the releases are believed to have occurred. Specifically, the spill location was set with the - X , +X, - Y a n d + Y dimensions set at 50, 1000, 1000 a n d 15 km, respectively. General currents in this area are believed to run toward the southeast, and the wind of 20 knots was from the south. Hence, the wind direction was set at 165 degrees in the N R D A M / C M E . The other parameters were set as follows: m e a n surface current: 0.036 tidal velocity - - parallel to m e a n surface current: 0.1 tidal velocity -- perpendicular to the m e a n surface current: 0 Oil from the spill first appeared on shore on 1 February a n d by 3 February several beaches in Matin, San Francisco a n d San Mateo counties were reported to have been oiled in varying degrees (Page & Carter, 1986). As indicated above, about 100 barrels ofoil were recovered from beaches, a n d by 4 February or shortly thereafter the a m o u n t ofoil which could be observed was apparently m i n o r (Page & Carter, 1986). Since a substantial a m o u n t of the oil from this incident came ashore, the N R D A M / C M E was used to assess an intertidal oil spill on a sandy beach. The physical fates submodel of the N R D A M / C M E was allowed to quantify both when the spilled oil would come ashore a n d how m u c h would reach shore. The clean up of 90% of the oil from the affected beaches was assumed to take place four days after the oil arrived on shore.

3.3.4 Comparison of results W h e n the N R D A M / C M E was used to simulate this crude oil spill under the environmental conditions described above, the physical fates submodel indicated that the spilled oil reached the coastline after 1.7 days, a n d some 38 metric tons ofoil was determined to have come ashore. These results are generally consistent with what was observed following the spill a n d with the oil spill trajectory results reported in Page & Carter (1986). The N R D A M / C M E subtidal results indicated that 426 seabirds were destroyed by the spill, while for the intertidal portion of the spill, the model indicated that 477 shorebirds were lost. R e m e m b e r i n g that in the N R D A M / C M E 58% of the birds contacted are assumed to be killed, the total n u m b e r of birds contacted would be 1557. This compares with the estimate in Page & Carter that 10 577 birds were oiled by this spill. Using the N R D A M / C M E , total damages a m o u n t to $19 639, virtually all of

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which is attributable to lost birds. No damage estimate is provided in the Page & Carter report. In summary, in this case the physical fates submodel of the N R D A M / CME appears to have led to reasonable results. However, the quantification of the n u m b e r of birds contacted in the biological effects submodel is only about one-seventh the n u m b e r believed to have been contacted as estimated in the Page & Carter study. This is within the order of magnitude standard of accuracy. The large n u m b e r of birds estimated by Page & Carter to have been affected would not be realized in the N R D A M / C M E except in the case of a m u c h larger spill. It should be noted that the estimated n u m b e r of birds impacted is an extraordinarily large n u m b e r per barrel spilled; it is two to three orders of m a g n i t u d e higher per barrel than estimates reported in the literature from the Argo Merchant (University of R h o d e Island, 1978), the Amoco Cadiz (US D e p a r t m e n t of Commerce, 1983), the Puerto Rican (US D e p a r t m e n t of Commerce, 1986) a n d the Arco Anchorage spills (State of Washington, 1986). Perhaps a partial reason for the large impact on birds from this particular spill is the fact that the oil was lost continuously over a long period of time which m a y have resulted in the surface slick being spread over a larger area, thus contacting a relatively large n u m b e r of birds.

3.4 Comparison of N R D A M / C M E results with an economic study of the economic value of Louisiana coastal wetlands The N R D A M / C M E measure of damages from a spill in a coastal area which causes a total loss in the natural e n v i r o n m e n t services provided by that area can be viewed as representing the damages from a loss of 'habitat'. The loss in habitat value is derived from, a n d can be measured by, the aggregate loss in use values resulting from an incident. This example compares the results of the N R D A M / C M E for a hypothetical oil spill a n d an a s s u m e d area loss (treated as an area closure for all area) with the results of a recent economic study of the value of Louisiana coastal wetlands by Costanza & Farber (1985). Note that this c o m p a r i s o n is not a retrospective validation, in that the results o f C o s t a n z a & Farber are estimates derived from available secondary data, not field observations of an actual wetland area. Nevertheless, it may be instructive to c o m p a r e their results with those of the N R D A M / C M E model.

3.4.1 Summa~ of the Costanza & Farber study of Louisiana coastal wetlands In order to estimate the economic value of Louisiana coastal wetlands, Costanza & Farber estimated separately the value of wetlands in (1) the production of commercial fishery harvests, (2)the p r o d u c t i o n of

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muskrats and nutria for commercial trapping, (3) supporting recreational activities, and (4)serving as a buffer to protect urbanized areas from storms. Two approaches were used by Costanza & Farber to measure economic values: willingness to pay and energy analysis. However, since the energy analysis approach has no basis in economic theory (see S h a b m a n & Batie, 1978), only the willingness-to-pay results are considered here. Also, the value of storm protection benefits of wetlands is a private benefit and, therefore, losses of this type would not be considered a damage under CERCLA. Hence, this value is not included in the comparisons which follow. Essentially, for commercial fisheries Costanza & Farber used regression and other techniques and the results of others (Lynne et al., 1981) to estimate the marginal productivity of coastal wetlands in the production of major commercial species such as shrimp, menhaden, blue crab and oysters. For recreation, a travel cost approach was used to measure the set of recreational services provided by wetlands in Terrebonne Parish. Option and existence values were not measured by Costanza & Farber. Their willingness-to-pay based estimates, stated in 1983 dollars, are presented in Table 1. As indicated in the Table 1, the value per hectare of Louisiana coastal wetlands estimated by Costanza & Farber is $68.31 per year (about $76 in 1987 dollars), and the present value is $983 (approximately $1095 in 1987 dollars). As can be seen from the above figures, storm protection benefits of wetlands is a private benefit and therefore losses of this type would not be considered a damage under CERCLA. Hence, this value is not TABLE 1

Estimates of Willingness-to-pay for Services Provided by Louisiana Coastal Wetlands (in 1983 dollars) Source

Annual value per hectare ($)

Present value per hectare (8%) ($)"

Commercial fishery Trapping Recreation Storm protection

10-28 4.87 1.24 51-92

128 61 19/' 775t'

Total

68.31

983

Source: Costanza & Farber (1985). "8% discount rate. ~'Theseresults presume a 1.3%rate of growth in population, with an associated increasein benefits over time.

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included in the comparisons which follow. In total, the value of a hectare of coastal Louisiana wetland after removing the storm protection benefits is $16 per year with a present value of $208, both expressed in 1987 dollars.

3.4.2 Summary of results using the NRDAM/CME In order to provide some insight into the value of coastal estuaries as a 'habitat ', the N R D A M / C M E was used to measure damages from the hypothetical loss of a hectare of wetlands. To consider possible seasonal effects, two cases in a Louisiana Province subtidal coastal estuary were considered: one case a s s u m e d that the loss resulted from a s u m m e r spill (set at 15 July 1986) a n d the second a s s u m e d that the loss of wetlands resulted from a winter spill (on 15 January 1986). (A negligible spill of 0.001 metric tons of m e d i u m oil - - CAS # 0 0 8 -- was a s s u m e d in each case in order to run the model.) Using the N R D A M / C M E , a one-hectare closure was set for one year for all fishing and hunting. The resulting measure of damages was capitalized at an 8% rate to arrive at an estimate of the asset value of a hectare of Louisiana coastal wetland.

3.4.3 Comparison of the Costanza & Farber (1985) results with the NRDAM/CME result,; When this case was tested with the N R D A M / C M E , the resulting damages a m o u n t e d to $1795 per hectare for the wetland loss resulting from the hypothetical s u m m e r oil spill and $1988 per hectare for the loss stemming from the winter spill. For the s u m m e r spill, bird losses were negligible a n d fishery losses predominated, while for the January spill, bird losses were about 15% of all losses, reflecting the presence of a large n u m b e r of waterfowl in this area during the winter. The average for the two N R D A M / C M E results, about $1892 per hectare, is nearly ten times higher than the $219 per hectare estimate of Costanza & Farber. Recognizing that the N R D A M / C M E includes viewing values for lost birds, lost catch for a variety of fish a n d shellfish species not considered by Costanza & Farber, a n d lost recreational as well as commercial value for these species, one would expect the N R D A M / C M E results to be higher t h a n those of Costanza & Farber, although it is difficult to determine how m u c h higher the N R D A M / C M E results would be expected to be given the major difference in methodologies a n d the scope of resources considered. It should again be e m p h a s i z e d that the results of Costanza & Farber are based on literature estimates of p r o d u c t i o n within wetlands a n d resulting impacts on associated uses, a n d not based on actual field observation.

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4 CONCLUSIONS The use of the N R D A M / C M E as a simplified approach for determining liability for spills under C E R C L A is a novel approach and, as such, raises a n u m b e r of important issues. One central issue is the extent to which such a model can be validated through comparison of model results With damage estimates from case studies of actual incidents. As can be seen from the cases discussed above, comparing damage estimates from the model to those obtained from case studies of actual incidents is not a straightforward task. Rather, a comparison of results requires a significant level of interpretation due to differences in the categories of damages which are included and concepts of valuation which are employed. This necessarily introduces a somewhat subjective element in the validation process. Nevertheless, validation of the model is a sufficiently important task that it requires a much greater level of research and a more systematic approach than was possible within the context of this paper. The m a n y difficulties inherent in making comparisons between field studies and the results obtained using the N R D A M / C M E were reviewed and, because of these difficulties, an order-of-magnitude standard of accuracy was presumed. Thus, cases where N R D A M / C M E results which fall well within an order of magnitude of field study estimates of damage are viewed as confirming the model results. Cases where results deviate by nearly an order of magnitude are viewed as open to question, while results which deviate by more than an order of magnitude are held to be inconsistent. Based on this standard of accuracy, the N R D A M / C M E appears to perform well for the case studies examined. All cases examined fall within the order-of-magnitude standard of accuracy. Those cases which fall near the standard tend to be easily explainable. For example, an alternate estimate of the mortality of birds resulting from the San Juaoquin Valley crude oil spill was significantly larger than was predicted using the N R D A M / C M E model, although within the order-of-magnitude standard. This alternate estimate, however, resulted in extraordinarily large numbers of birds impacted per barrel spilled; two to three orders of magnitude larger per barrel than that from theArgo Merchant, theAmoco Cadiz, the Puerto Rican and theArco Anchorage spills, for example. Thus, the N R D A M / C M E indicated a large n u m b e r of birds impacted per barrel compared to other well-studied spill incidents, although results were lower than those estimated by alternate methods. These results suggest that an inexpensive and easy-to-implement approach, such as that developed in the N R D A M / C M E , provides a cost-

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effective means of deriving 'reasonable' damage estimates for relatively m i n o r pollution incidents. Nonetheless, it is important to continue to explore ways to improve the model, both through additional a n d more systematic attempts to validate the model for different types of spills in a variety of environments, a n d through updating the model a n d its databases as new data a n d results in environmental a n d resource economics, toxicology, m a r i n e biology, modeling of fates a n d related fields become available.

REFERENCES Costanza, R. & Farber, S. C. (1985). The Economic Value of Coastal Wetlands in Louisiana. Louisiana State University, Baton Rouge, LA. Economic Analysis Inc. and Applied Science Associates (1987). Final Report: Measuring damages to coastal and marine natural resources: Concepts and data relevant for CERCLA Type A damage assessments. US Department of the Interior, Washington, DC. National Technical Information Service, Springfield, VA. (NTIS DOI/SW/DK-87/002). Hope-Jones, P., Monnat, J. Y., Cadbury, C. J. & Stowe, T. J. (1978). Birds sited during the AMOCO CADIZ i n c i d e n t - an interim report. Mar. Pollur Bull., 9, 307-10. Milhous, M. N. & Gross, A. C. (1985). Interim report of biological effects ofE. F. Barrett, G. T. oil spill on affected areas, Long Island Lighting Company, Hicksville, New York. National Research Council, National Academy of Sciences 1985. Oil in the Sea: Inputs, Fates and Effects. National Academy Press, Washington, DC. Ott, G. L. (1987). Comparison of Federal guidelines for natural resources damage assessment of a major oil spill Island Park, NewYork. InAmerican Petroleum Institute Proceedings, 1987 Oil Spill Conference." Prevention, Behavior and Cleanup, Baltimore, MD, 6-9 April 1987. American Petroleum Institute, Washington, DC, Publication No. 442, pp. 533-40. Page, G. W. & Carter, H. R. (1986). Impacts of the 1986 San Joaquin Valley Crude Oil Spill on Marine Birds in Central California. Point Reyes Bird Observatory, Stinson Beach, CA. Reed, M., French, D., Grigalunas, T. & Opaluch, J. (1989). Overview of a natural resource damage assessment model system for coastal and marine environments. Oil & Chemical Pollution, 5 (this issue), 85-97. Shabman, L. & Batie, S. S. (1978). Economic value of natural coastal wetlands: A critique. Coastal Zone Manage. J., 4 (3), 231-47. State of Washington (1986). ARCO ANCHORAGE Marine Resource Damage Assessment. Department of Ecology, Olympia~ Washington. Stokes, R. L. (1979). Economic Evaluation of Marine Biological Resources. Institute for Marine Studies, University of Washington, Seattle. US Department of Commerce, National Oceanographic and Atmospheric Administration (1983). Assessing the Social Costs of Oil Spills." The AMOCO CADIZ Case Study. US Department of Commerce, Washington, DC, p. 144.

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US Department of Commerce, National Oceanographic and Atmospheric Administration (1986). Resource Damage Assessment of the T/J/ PUERTO RICAN Oil Spill Incident, Report by James Dobbin Associates, Inc. US Department of Commerce, Washington, DC, p. 126. US Coast Guard (1986). T / V ARCO ANCHORAGE Major Oil Spill, Port Angeles, Washington, 21 December 1985. On-Scene Coordinator's Report, Marine Safety Office Puget Sound, US Coast Guard, Washington, DC, p. 236. University of Rhode Island, Center for Ocean Management Studies (1978). In the Wake oftheARGO MERCHANT. Center for Ocean Management Studies, Kingston, RI, p. 181.