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City of Ripon Well#12 Nitrate Study Report May 31,2006 2.0 DWR WELL LOG SEARCH AND COLLECTION OF OTHER INFORMATION The first task carried out was obtaining well logs and other available information for residential water supply wells located within the general vicinity of Well 12. The purposes for obtaining this information were 1) to assess the potential for nitrate migration down to the level of the Well 12 screen through nearby residential wells and 2) identify wells in vicinity of Well 12 for sampling and analysis. 2.1 DWR Visit An SGI Geologist visited the DWR office in Sacramento on July 27, 2005 to conduct a file review and obtain the appropriate well logs. The position of Well 12 was located on a topographic map that included the township, range, and section of the well location. The four sections containing Well 12 or that were closest to it were then identified and the well logs for all wells in those four sections were retrieved (a search radius of approximately 2,000 feet was used for the DWR log search). A total of 89 logs were retrieved. Four of these logs were for abandoned wells. The remaining 85 logs were for domestic, municipal, residential, irrigation, and monitoring wells. 2.2 Well Log Evaluation The following information was recorded from the well logs: • Address and other information related to location, • Well owner, • Year constructed, • Well depth, • Installation type, • Screened interval, • Gravel interval, and • Surface seal depth. After the logs were examined, the locations of wells were plotted on a map of the area surrounding Well 12. Well addresses were used to plot these locations when available. When addresses were not listed on the well log, physical descriptions of the well locations listed on the logs were used to plot locations. In several instances, the addresses listed on the DWR logs were invalid. In these cases, SGI contacted the City of Ripon to find out if any record of old addresses existed. The City determined that the invalid addresses changed when the properties transferred from the unincorporated county to the city jurisdiction. ft.W.412R� 2-1 Pie soupte Group, In.