WASHINGTON (AP) - The Supreme Court has agreed to decide what share railroads and an oil company should bear of the cleanup of a contaminated industrial site in Arvin, Calif., near Bakersfield, that threatened drinking water supplies.

Shell Oil Co. and the railroads - Burlington, Northern and Santa Fe Railway Co. and Union Pacific Railroad Co. - say they are being unfairly tagged with an inordinate portion of the cost of cleaning up the site.

The companies contend that they merely transported and sold legal, useful products and were not involved in years of soil and groundwater contamination.

The site was once the home of a fertilizer-and-insecticides manufacturing facility.