This API survey represents an important milestone in the petroleum industry's ongoing efforts to improve its environmental performance. At EPA's request, API members in the refining, marketing, and transportation sectors voluntarily participated in a survey of AST facilities.(Footnote 1) The purposes of the survey were to document recent AST facility improvements, determine the prevalence of groundwater contamination,(Footnote 2) rank the relative sources of groundwater contamination, and determine the status of remedial activities at API member company facilities.

The survey was sent to a random sample of 350 API member company facilities.(Footnote 3) Responses were received from 299, or 85 percent, of the sampled facilities. Names and locations of responding facilities were kept confidential by SRI International, the independent survey research firm that conducted the sampling and tabulated the data.

Footnote 1 - The survey addressed only the tank farm portion of facilities in the three industry sectors. In the transportation sector this involved pipeline bulk storage facilities.

Footnote 2 - The survey results indicate only the presence of contamination; the data do not indicate the volume of contamination at individual sites.

Footnote 3 - Because of the random nature of the sample, survey results are estimates of actual values for the total population of API member company facilities.