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i Draft: March 24, /999 ~ '~ Page 3 <br />' Alluvial aquifer monitoring wells will be located along the eastern boundary of the portion of the <br />Yankee Gulch Lease that lies west of Piceance Creek. <br />' The monitoring well layout is described in Section 2.1 and shown on Figure 1. Figure 2 is <br />a generalized stratigraphic column showing aquifer locations and important stratigraphic horizons. <br />' The monitoring wells will bepositioned up-gradient, down-gradient, and cross-gradient of the mine <br />panel. American Soda has proposed this well configuration for the first panel to assure that potential <br />impacts to groundwater and surface water will be detected. In addition, there are monitoring wells <br />and production wells within the 0-5 yeaz mine panel that will be part of the monitoring well <br />' network. <br />2.1 Monitoring Well Layout <br />' The monitoring well layout, shown in Figure 1, for the first phase of operations includes the <br />' addition of two multiple-completion wells located outside the 0-5 year mine panel, one multiple- <br />completion well located within the 0-5 year panel, and two alluvial aquifer wells located between <br />' the proposed mine panel and Piceance Creek. These proposed wells will augment the four existing <br />wells located outside ofthe 0-5 yeaz panel, and the six existing wells located within [he limits ofthe <br />' 0-5 yeaz panel. A summary of the wells included in the proposed groundwater monitoring plan is <br />presented in Table 1. <br />The monitoring wells can be grouped together to provide four nested or co-located <br />monitoring locations for the Uinta Formation, A Groove, B Groove, and Dissolution Surface. This <br />' network will provide nested or co-located installations for two down-gradient, one up-gradient, and <br />two cross-gradient locations for the first mining panel. <br />' The monitoring well layout, as designed, assumes a groundwater flow direction in the Upper <br />and Lower Aquifers of southwest to northeast. This trend is in accordance with regional <br />' groundwater data (Weeks' et al. 1974). Site-specific data from the Upper Aquifer suggests the flow <br />direction is roughly east to west. Therefore, positions of the up-gradient and down-gradient wells, <br />' relative to groundwater flow direction, are based on an averaged flow direction of N65°E. The <br />monitoring well layout is shown on Figure I . <br />'Weeks, J.B., G. H. Leavesley, F. A. Welder, and G. J. Saulnier, Jr. (1974). "Simulated Effects <br />of Oil-Shale Development on the Hydrology of Piceance Basin, Colorado," USGS <br />Professional Paper 908, 84 p. <br />Agapito Associates, Inc. <br />1 <br />