<ARTICLE> 5
<LEGEND>
THIS SCHEDULE CONTAINS SUMMARY FINANCIAL INFORMATION EXTRACTED FROM FORM 10-Q
AND IS QUALIFIED IN ITS ENTIRETY BY REFERENCE TO SUCH FINANCIAL STATEMENTS.
</LEGEND>
<MULTIPLIER>                               1,000

       
                                  
<PERIOD-TYPE>                              6-MOS
<FISCAL-YEAR-END>                    DEC-31-1997
<PERIOD-END>                         JUN-30-1997
<CASH>                                     16322
<SECURITIES>                                   0
<RECEIVABLES>                              78474
<ALLOWANCES>                                   0
<INVENTORY>                                41794
<CURRENT-ASSETS>                          159499
<PP&E>                                   1182224
<DEPRECIATION>                            629426
<TOTAL-ASSETS>                            883704
<CURRENT-LIABILITIES>                     131115
<BONDS>                                        0
<PREFERRED-MANDATORY>                          0
<PREFERRED>                                    0
<COMMON>                                     209
<OTHER-SE>                                148058
<TOTAL-LIABILITY-AND-EQUITY>              883704
<SALES>                                   383286
<TOTAL-REVENUES>                          393576
<CGS>                                     340925
<TOTAL-COSTS>                             360967
<OTHER-EXPENSES>                               0
<LOSS-PROVISION>                               0
<INTEREST-EXPENSE>                          6792
<INCOME-PRETAX>                            26352
<INCOME-TAX>                                4200
<INCOME-CONTINUING>                        22152
<DISCONTINUED>                                 0
<EXTRAORDINARY>                                0
<CHANGES>                                      0
<NET-INCOME>                               22152
<EPS-PRIMARY>                               1.06
<EPS-DILUTED>                               1.06