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DG°~Q~'~ seepage in response to rainfall or snowmelt, or from ditch seepage. The direction of groundwater flow in the sedimentary strata is to the east, primarily along bedding planes. The western highwall of C-Pit was dry this year, before the water began to flow in / the Boulder Feeder Canal. About 3 days after the Canal started flowing, seepage appeared in the C-Pit highwall. This fact indicates that groundwater is not the source of these observed seeps. Figures 2A, 2B and 2C show a sequence of photographs of the western highwall of C-Pit before and after the Canal started flowing. The alluvial aquifer of St. Vrain Creek is in contact with the sedimentary strata east of C-Pit but not in contact with C-Pit itself. Groundwater in the alluvial aquifer is typically 5-8 feet below ground surface and flows east-southeast, generally towards St. Vrain Creek. There is no apparent hydraulic connection between C-Pit and the alluvial aquifer. 6.0 Surrounding Wells and Local Aquifers There are two aauifers in the area that are typically used for water supply. They are the al~vial aaoi_ifPr_of St. Vrain Creek and the Dakota sandstone. Both of these aquifers are isolated from C-Pit by 800-1000 fegt of relatively imaermeablE sedimentary rocks. Figure 3 shows a plot of wells in the area based on data from the Colorado Division of Water Resources (permitted wells database). The list of wells from the Colorado Division of Water Resources is included in Appendix B. Wells are shown by quarter -quarter section. It should be noted that many of the wells are piezometers and monitoring wells installed by Western Mobile in their sand and gravel property. Recent water quality data is available from wells in both the Dakota sandstone and in the alluvial aquifer. Water quality in both aquifers is generally good with no indication of any impact from CKD disposal. A well completed in the Dakota sandstone (located in the extreme southeast corner of section 28) was sampled in April, 1 ersonnel from Grant Environmental, Inc. The laboratory results (Table 6.1) 'ndicate that the water quality is in compliance with almost all app' ndards. Results of water quality analysis in A-Pit Reservoir are also shown in Table 6.1. The pH (which would serve as a key indicator of impacts due to CKD disposal) of Dakota Well water is 8.28, within the natural, expected range. Table 6.1 shows the measured water quality in this well compared to the groundwater standards suggested by the DMG. 13