I was not the only one who heard 11 million gallons was the low-end estimate of spill volume and 38 million gallons was the high-end estimate during my first 24 hours in Valdez after the spill. A year later, two separate newspaper accounts reported volumes up to 27 and 38 million gallons (Hennelly 1990; Spence 1990). One article (Hennelly 1990) reported that the Alaska Department of Environmental Conservation (ADEC) and Exxon jointly contracted Caleb Brett, a company that gauges tanker loads for the oil industry, to do tank soundings to estimate the volume spilled. However, Caleb Brett "closed ranks with Exxon" and refused to make public documentation of its findings, citing its employer-client relationship (Hennelly 1990, 14).

I found that the Alaska Department of Law conducted a separate investigation of the spill volume in preparation for a civil lawsuit against Exxon over damages to wildlife and habitat. When this lawsuit was settled in 1991 (Sidebar 2), the State of Alaska shelved its investigation. In 1994, in response to repeated public requests, the state released its investigation files to the Alaska Resources Library and Information Services (ARLIS) in Anchorage, Alaska (AK Department of Law 1991).

According to the one-page report filed by Caleb Brett (1989), the Exxon Valdez left the tanker terminal in Port Valdez on 23 March 1989 with 53.04 million gallons of oil on board. The tanker grounded on Bligh Reef around midnight. Caleb Brett reported 42.2 million gallons of cargo was transferred to three Exxon tankers and a fleet of barges. Since the Exxon Valdez had been carrying a total cargo of 53.04 million gallons, simple math led Caleb Brett to conclude that the total spilled was the difference--10.8 million gallons; however, this volume was never independently verified. In the absence of other information at the time (1989), the media used--and still uses--Exxon's self-reported spill volume estimate.

According to one of the State of Alaska's independent surveyors, "much more oil than the 258,000 barrels [10.8 million gallons] reported [by Caleb Brett] was spilled" (Murchison 1991, ACE 9486070). He continued, "It is my opinion that the major differences [in spill volume estimates] are due to the tremendous 'churning forces' that occurred as the oil gushed from the vessel and the seawater forced itself in, due to the hydraulic pressure[. T]his resulted in the emulsification of oil and water" (ibid.). He found errors in the calculations of oil on board the grounded Exxon Valdez and noted, "Most of the water cuts or soundings are questioned because of the holes in the vessel[. A]pparently the method used to differentiate between oil and water was providing inaccurate results, which resulted in grossly under-estimating the water and over-estimating the oil" (Murchison 1991, ACE 9486069).

State investigators tracked each of the three Exxon tankers used to lighter (transfer) oil from the Exxon Valdez (AK Department of Law 1990). These three tankers went to three different Exxon refineries to offload their cargo. Exxon insisted the cargo was 100 percent oil, however the evidence suggests otherwise. For example, according to the deposition of Claude Wendell Dees, an Exxon Shipping officer in charge of the lightering operation aboard the Baton Rouge (Dees 1991), "We had more water than normal and Captain Solywoda knew that. He left Exxon and took early retirement" (ibid., 193). Exxon never disclosed its shore tank records from each of the three discharge port: these records would show the percentage of water in the offloaded cargo, water which was known to exist. For example, Dees stated, "None of the oil discharged at Hawaii was used because of high water content" (ibid., 164).

However, Exxon did not control all the cargo records of the ill-fated Exxon Valdez, because not all of the cargo was offloaded at each of the refineries. For example, Dees stated, "On the trip to Hawaii, we gauged our tanks to determine water content" (ibid., 222). "I gravitated some of it out into one tank and kept it aboard as dirty ballast. We went back to Valdez with this dirty ballast" (ibid., 46). Similarly, cargo that remained on board the other two lightering tankers also ultimately was returned as ballast water to the tanker terminal. According to papers on file with the state's investigation, the oil content of the former cargo (now ballast water) was estimated as a percentage of the total volume by eyewitnesses before the tankers sailed to Valdez (AK Department of Law 1991, ACE 10864138-10864143). The amount of dirty ballast, and its tank location, is recorded on official ADEC Ballast Water Discharge Certificate Affidavits at the tanker terminal in Port Valdez.. Exxon never accounted for the known volume of water from the Exxon Valdez in the cargo of its three tankers; the State of Alaska investigators did (Table 1).

In light of this evidence, Exxon's self-reported spill volume of 11 million gallons is incorrect. I conclude that the State of Alaska's conservative estimate of 30 million gallons should be used when referring to the Exxon Valdez oil spill volume.