<TABLE> <S> <C>

<ARTICLE>                                          5
<RESTATED>
<MULTIPLIER>                                                    1,000
       
<S>                                                  <C>                             <C>                        <C>
<PERIOD-TYPE>                                                   3-mos                       6-mos                      9-mos
<FISCAL-YEAR-END>                                         Dec-31-1997                 Dec-31-1997                Dec-31-1997
<PERIOD-END>                                              Mar-31-1997                 Jun-30-1997                Sep-30-1997
<CASH>                                                         27,283                      29,465                     15,755
<SECURITIES>                                                        0                           0                          0
<RECEIVABLES>                                                 135,949                     149,346                    146,049
<ALLOWANCES>                                                        0                           0                          0
<INVENTORY>                                                    15,486                      13,638                     18,271
<CURRENT-ASSETS>                                              191,539                     207,720                    196,505
<PP&E>                                                      2,099,143                   2,177,335                  2,241,442
<DEPRECIATION>                                                844,353                     890,298                    933,638
<TOTAL-ASSETS>                                              1,490,268                   1,537,768                  1,548,277
<CURRENT-LIABILITIES>                                         189,982                     210,415                    207,534
<BONDS>                                                       564,936                     588,752                    604,783
<PREFERRED-MANDATORY>                                               0                           0                          0
<PREFERRED>                                                         0                           0                          0
<COMMON>                                                        6,334                       6,343                      6,375
<OTHER-SE>                                                    609,884                     613,919                    615,789
<TOTAL-LIABILITY-AND-EQUITY>                                1,490,268                   1,537,768                  1,548,277
<SALES>                                                       159,573                     281,753                    402,408
<TOTAL-REVENUES>                                              159,573                     281,753                    402,408
<CGS>                                                          16,722                      23,966                     28,523
<TOTAL-COSTS>                                                 110,657                     211,913                    314,218
<OTHER-EXPENSES>                                                 (698)                       (913)                    (1,539)
<LOSS-PROVISION>                                                    0                           0                          0
<INTEREST-EXPENSE>                                             10,410                      19,995                     29,985
<INCOME-PRETAX>                                                36,894                      45,335                     49,427
<INCOME-TAX>                                                   19,640                      25,460                     26,350
<INCOME-CONTINUING>                                            17,254                      19,875                     23,077
<DISCONTINUED>                                                      0                           0                          0
<EXTRAORDINARY>                                                     0                           0                          0
<CHANGES>                                                           0                           0                          0
<NET-INCOME>                                                   17,254                      19,875                     23,077
<EPS-PRIMARY>                                                    0.27  <F1>                  0.31  <F1>                 0.36 <F1>
<EPS-DILUTED>                                                    0.27  <F1>                  0.31  <F1>                 0.36 <F1>

<FN>
<F1> Earnings per share has been restated to reflect the Company's adoption of
     Statement of Financial Accounting Standards No. 128, "Earnings Per Share."
</FN>

        


</TABLE>