The measured hydrologic performance of three phosphogypsum stack system top gradient final cover alternatives and six side slope final cover alternatives over a 3-year period are presented. Hydrologic measurements consisted of monitoring: (i) rainfall, air temperature and pan evaporation; (ii) infiltration and runoff volumes and water table levels; (iii) runoff water quality; (iv) changes in soil and gypsum moisture content; and (v) root depth penetration. Measured hydrologic performance was used to calibrate the HELP model (Schroeder et al. (1994), Version 3.07) for top gradient and side slope final covers.
Recommended values for runoff curve number, evaporative zone depth and leaf area index are presented for the final cover alternatives investigated. The calibrated HELP model provides reliable estimates of long-term post-closure hydrologic performance.
This document provides data tables associated with the study.
Nadim F. Fulihan and Thomas S. Ingra with Rodrigo Home, Ardaman & Associates, Inc. March 2005.