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III IIIIIIIIIIIIIIII 999 aJ -~~g4~ EXHIBIT G MATER INFORMATION 'l G.1 Introduction The San Luis Project is situated within the Rito Seco drainage basin. The Rito Seco is a perennial stream which transects the mine property. In addition to the main stem of Rito Seco, there are several tributaries, most of which are ephemeral streams, which flow through the property. The principal groundwater found in this area is in the Tertiary ~- age Santa Fe Conglomerate and the Precambrian biotite and biotite- amphibole gneiss ore zone underlying the Santa Fe (:onglomerate. Groundwater found in the Santa Fe Conglomerate is con~:idered to be part of a regional aquifer system, while the groundwater found in the Precambrian rock is judged to be a local, limited aquifer system. A hydrologic monitoring network has been established at the San Luis Project to monitor both surface water and groundwater flowing through the mine property. Monitoring locations have been set up in an upgradient and downgradient position t~ assess the potential impacts of mining on the hydrologic system. The surface water monitoring system consists of six gaging stations located on the main stream transecting the mine property, Rito Seco, and the major tributaries entering Rito Seco along this reach. The locations of the six gaging stations are shown on Figure G-1. Table G.1-1 presents the installation dates for Each station. The groundwater monitoring network was designed to evaluate y groundwater flow and groundwater quality in two distinct areas; the mine pit areas and the proposed plant site and heap leach area. A ' total of seven monitoring wells were completed in the mine ore zones to establish background water quality and to monitor groundwater ' levels. G-1 EXHIBIT G REVISED 2/15/89