In the Guadalupe Dunes, 170 miles north of Los Angeles and 250 miles south of San Francisco, an oil spill persisted unattended for 38 years. Over the period 1990-1996, the national press devoted 504 stories to the Exxon Valdez accident and a mere nine to the Guadalupe spill -- even though the latter is most likely the nation's largest recorded oil spill. Although it was known to oil workers in …