| 9/01/1906 to 8/31/1909 | Mr. W.H. Chamberlain (res. Engineer) |
| 9/01/1909 to 1/12/1915 | Mr. W.F. Harrington |
| 1/12/1915 to 5/31/1919 | Mr. Irving J. Cox |
| 6/01/1919 to 10/01/1923 | Mr. D.S. Robinson |
| 9/15/1923 to 9/30/1945 | Mr. F. T. Beers |
| 9/30/1945 to 4/15/1948 | Mr. R.F. Boltz |
| 4/15/1948 to 1/09/1952 | Mr. F. E. Jaquot |
| 1/14/1952 to 8/31/1959 | Mr. G. W. Collins |
| 9/01/1959 to 6/30/1961 | Mr. A. Mellott (acting mgr. at Seneca Plant 7/1/1960 to 6/30/1961) |
| 7/01/1960 to 7/01/1961 | Mr. W. B. Gideon (acting mgr. when Mr. Mellott was absent) |
| 8/01/1961 to 5/31/1971 | Mr. John Main |
| 6/01/1971 to -/--/1971 | Mr. Henry Means |
| -/--/1971 to shutdown | Mr. Tony Ursic |