Pentagon plans call for closing Mather Air Force Base in four years, but cleaning up hazardous waste there will take at least 30 years, according to Air Force documents. The documents, obtained under the Freedom of Information Act, show that the commission that recommended the base's closure did not determine how toxic waste cleanup would affect the sale and conversion of Mather to other uses. Nor did the commission conduct an environmental review of its plan to move Mather's navigator training school to Beale Air Force Base 40 miles north of Sacramento, even though its charter required such a review, according to the records. The records also reveal that the panel did not study the effect of closing Mather's hospital on medical treatment for the 43,000 military retirees in the Sacramento area. Mather is one of 86 military installations nationwide that the commission recommended be closed as a cost-saving measure.