Perancangan Sequence Backfill Di Lokasi Penambangan Bukit 7A Baru Studi Kasus PT. ANTAM, Tbk UBP Bauksit Tayan, Kabupaten Sanggau, Kalimantan Barat | Fathurrohman | Al-Fiziya: Journal of Materials Science, Geophysics, Instrumentation and Theoretical Physics