Table
01. Number of Nonmetallic Operations in the United States,
by Primary
Activity, 1978-2007
Year
|
Underground Mines
|
Surface Mines
|
|
|
Underground
|
Surf at UG
|
Total
|
Strip
|
Dredge
|
Other
|
Total
|
|
1978
|
119
|
7
|
126
|
1,110
|
4
|
21
|
1,135
|
|
1979
|
108
|
4
|
112
|
1,060
|
2
|
18
|
1,080
|
|
1980
|
125
|
42
|
167
|
1,081
|
2
|
9
|
1,092
|
|
1981
|
147
|
66
|
213
|
1,064
|
2
|
1
|
1,067
|
|
1982
|
143
|
40
|
183
|
866
|
1
|
1
|
868
|
|
1983
|
90
|
4
|
94
|
782
|
3
|
1
|
786
|
|
1984
|
88
|
2
|
90
|
774
|
4
|
1
|
779
|
|
1985
|
91
|
1
|
92
|
777
|
5
|
1
|
783
|
|
1986
|
86
|
2
|
88
|
728
|
4
|
1
|
733
|
|
1987
|
74
|
-
|
74
|
678
|
4
|
-
|
682
|
|
1988
|
77
|
3
|
80
|
668
|
2
|
-
|
670
|
|
1989
|
75
|
2
|
77
|
673
|
3
|
-
|
676
|
|
1990
|
72
|
2
|
74
|
677
|
2
|
-
|
679
|
|
1991
|
66
|
3
|
69
|
642
|
2
|
-
|
644
|
|
1992
|
63
|
4
|
67
|
593
|
2
|
-
|
595
|
|
1993
|
60
|
2
|
62
|
595
|
2
|
-
|
597
|
|
1994
|
56
|
7
|
63
|
581
|
2
|
-
|
583
|
|
1995
|
53
|
4
|
57
|
568
|
2
|
-
|
570
|
|
1996
|
46
|
4
|
50
|
545
|
2
|
-
|
547
|
|
1997
|
46
|
2
|
48
|
540
|
2
|
-
|
542
|
|
1998
|
46
|
4
|
50
|
554
|
2
|
-
|
556
|
|
1999
|
47
|
3
|
50
|
564
|
1
|
1
|
566
|
|
2000
|
45
|
2
|
47
|
578
|
3
|
-
|
581
|
| |