2022-11-07_PERMIT FILE - M2022001 (13)

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RECEIVED NOV 0 7 2022 ' of RedarrtaGon, SECTION 2 - PREVIOUS STUDI a'd i TA COLLECTION, AND MAPPING OF DEPTH TO GROUNDWATER PREVIOUS STUDIES AND DATA COLLECTION Previous studies by CGS, Brown and Caldwell, and others were reviewed to identify aquifer and groundwater data available in the vicinity of the Town. The information and data included: groundwater level data, groundwater recharge data, groundwater model input data, mapping, geologic characterizations and other information pertaining to the shallow groundwater conditions within the Town. In addition, we completed a review of groundwater information available from Town staff, Palmetto Environmental, Tetra Tech, Central Colorado Water Conservancy District, the Division of Water Resources, Colorado State University and input from residents and individuals with relevant knowledge. MAPPING OF DEPTH TO GROUNDWATER The starting point for developing the Town dewatering plan is to identify the areas within the Town that are affected by shallow groundwater conditions. Water level data were compiled to prepare maps of groundwater elevation and depth to groundwater for the recent high-groundwater condition. Previous studies have included depth to groundwater mapping,but those studies did not include water level data from the Town's wells and were of a regional as opposed to local scale. Ground level elevation data from the USGS and CDWR, were supplemented with new survey information developed from our own survey and data available from Tetra Tech and Palmetto for monitoring wells located adjacent to the Town. Additional water level data were collected from the Town's existing wells and new monitoring points in and around the Town, identified in Figure 2.1 and summarized in Table 2.1 on the following pages. Water level hydrographs were prepared for each of the monitoring wells relied upon in this study, as presented in Appendix A. Historically, the depth to water within the Town limits has been as deep as 45 feet below ground surface, based on information reported on well permit forms and information provided by the Town regarding sewer line and pump station conditions. The current depth to water within the Town ranges from 9 to 17 feet below ground surface. During 2015, groundwater levels were as shallow as 6 feet below ground surface near Main Street and 11`h Street (RE-1 Well) and 4 feet below ground surface near the wastewater treatment plant (located in the northeast corner of Town). The hydrographs indicate that water levels have generally trended down since the monitoring was initiated in 2015;with the water level decline for the approximate 16-month period ranging from 0.4 to 6.4 feet, and averaging approximately 2.5 feet. 3