WASHINGTON (AP) — Envi ronmentalists have suffered a number of major setbacks on House legislation to curb the abuses of strip coal mining. By a 65 to 19 vote Monday, the House agreed to exempt strip miners who remove entire mountaintops from the strin gent requirements that would apply to those who do their mining on the steep sides of the mountains. The amendment was offered by Rep. John Slack, D-W. Va., who said steep slope regu lations should not apply to mountaintop removal mining because when the top of a mountain is entirely removed, a flat “plateau”’ is created. The problems of strip mining and land reclamation on such a plateau are different from those on a sharp incline, he ar gued. In another defeat for environ mentalists, the House rejected 58 to 13 a proposed amendment by Andrew Young, D-Ga., that would have banned all strip mining on mountain slopes that are steeper than 20 degrees. It also rejected an amend ment that would have estab lished tough federal strip min ing standards within 120 days. The bill provides that these standards be phased in gradu ally over a three-year period. In the meantime, less stringent interim standards would be in force. The controversial legislation has passed the Senate in a slightly different form. House debate was due to resume to day. The legislation would estab lish a federal-state program for regulating strip mining.