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i i AUGEAS Corporation California Natural Products Problem Assessment Report June, 1991 in each boring, due to large anticipated changes in water levels as a result of large-scale agricultural pumping of groundwater in the area. Approximately 10 feet of well screen was located both above and below the water table with five feet of blank casing extending to a subsurface locking Christy Box.Each well was also equipped with a locking pressure cap to avoid the potential for vandalism. 4.1 Surveying Once well installation was complete, each well was surveyed to determine its precise location and the elevation of the top of each casing. Table 1 presents the results of this survey and water depth/elevation measurements for each monitoring well. Based on this information, the direction of groundwater movement was determined to be generally to the north with a slight seasonal fluctuation due to the pumping • of nearby high volume irrigation wells. The northerly gradient on August 30, 1990 was .004 feet/feet. I 4.2 Well Development and Sample Collection Within 24 hours of well installation,each monitoring well was developed by purging a sufficient amount of water to remove all suspended material from the well.Approximately 55 gallons of water were removed from each well and contained and stored onsite until an analysis of the water could be obtained. Following the purging activities,duplicate groundwater samples were collected using a clean PVC hand bailer,and placed into 40 ml vials. Prior to sampling,the bailer was completely disassembled, washed in deionized water and reassembled. Each water sample was labeled, placed on ice, and transported to California Water Labs under Chain of Custody within 24 hours of collection. Each water sample was analyzed for EPA Method 602 (purgeable aromatics) and EPA Method 8020 (total petroleum hydrocar- bons (TPH)). i i i i � 7 :i `