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interval of a well was identified. The sensing interval is defined as the interval in which the <br />well is in communication with the adjacent aquifer; it is the interval between the bottom of the <br />well and a location where the well casing is grouted above the screen interval. Once a sensing <br />interval was determined for a well, this information was used in conjunction with aquifer <br />configuration data gathered in Phase 1 to determine if a well was completed in more than one <br />aquifer. <br />The information contained in the images of the well permits confirmed that 109 wells in the <br />SEO bedrock water level monitoring network have well sensing zones within one bedrock <br />aquifer. The remaining wells were either completed in multiple aquifers or the information <br />available on the well permit was insufficient to confirm if the well was completed in a single <br />aquifer. The 109 wells were supplemented with 11 alluvial wells located in the Designated <br />Basins that overly the Denver Basin Region to identify 120 well candidates for autumn water <br />level measurement. The alluvial wells in the designated basins that overly the Denver Basin are <br />not measured by SEO staff in the fall. <br />2.0 Water Level Measurement Collection and Solicitation <br />Task 39.1 involves obtaining autumn water levels in up to 120 wells in the Denver Basin Region. <br />The objective is to collect water levels in these wells during the post irrigation season to help <br />characterize the seasonal variation in water levels in the aquifer system. Although all of the <br />candidate wells identified are part of the SEO water level measurement network, many of these <br />wells are not measured directly by the State. Water level measurements from approximately <br />100 wells (of the 269 in the SEO bedrock network) are solicited from individual municipalities, <br />water conservancy districts or other entities. To keep consistent with the State's water level <br />data collection protocols, the wells typically measured by the State were measured under this <br />Task, and wells that are typically solicited by the State were solicited by CDM under this Task. <br />The details of each of these activities are discussed in the following sections. <br />2.1 Water Level Measurement Collection <br />A total of 90 wells of the 120 wells for which water levels were collected under Task 39.1 were <br />identified for measurement by CDM project staff. Measurements in the autumn post-irrigation <br />season were targeted to begin in late October. Due to delays in reviewing well completion data <br />to identify candidate wells completed in a single aquifer, the Phase 2 (2004) program started in <br />early December. <br />Water levels collected in this task were measured using equipment and procedures that are <br />equal or similar to those used by the State in their ongoing water level data collection efforts. <br />Water levels were measured using steel tape, electric M-scope, airline, water level conductivity <br />meter and sonic water level meter. With the exception of the sonic meter, State equipment was <br />used during the data collection to maintain consistency with past measurements at a given well. <br />The variety of methods used to measure water levels in this task was necessary due to well <br />access limitations, presence of in-well wiring and equipment, and depth to water. Explanations <br />of each method with their pros and cons are discussed below to assist others in deciding what <br />equipment to use in the future. A comparison of the sonic meter to other methods is presented <br />in Appendix A. <br />