Over the course of the next forty years , Unocal leaked 18 million gallons of petroleum under the Dunes .
Unocal , an oil company , began operating the Guadalupe Oil Field in the 1950s .
Over the course of the next forty years , oil company leaked 18 million gallons of petroleum under the Dunes .
Unocal , an oil company , began operating the Guadalupe Oil Field in the 1950s .