"...the minimum altitude recorded on the FDR was 59 feet above ground level." [emphasis added] AGL (elevation above ground level), not MSL (elevation above mea

"...the minimum altitude recorded on the FDR was 59 feet above ground level." [emphasis added] AGL (elevation above ground level), not MSL (elevation above mean sea level). The runway/taxiway elevation is already taken into account. They were 59 feet above the taxiway.