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Mr Ronald Rowe March 25, 1998 Page 3 • The transducer data was downloaded from the data logger into an Excel spreadsheet format Barometric pressure readings were obtained from a weather station located at the Stockton Airport, approximately twenty miles south of the site The barometric pressure data was converted from millibars to feet-water in order to calculate the barometric efficiency (BE) of the wells The BE was applied to the transducer data to correct for changes in head data due to barometric pressure Barometnc pressure data and transducer data are included in Attachment A Figure A-1 shows the data plots of MW-1 and barometric pressure used to calculate the BE Figure 2 shows the transducer data of the unused well and MW-1 both uncorrected and corrected for barometric pressure The following interpretations can be made from the data 1 Overall the water level rose during this monitoring period 2 The pressure data in the unused well and MW-1 are nearly identical, indicating that both wells screen the same potentiometric surface 3 Barometric pressure changes have little influence on the magnitude of water table fluctuations (barometric efficiency = 18%) This is not unusual given the fact that wells screened within unconfined aquifers are normally not influenced by barometric pressure This is due to the atmospheric pressure being equally applied across the entire aquifer and not just the column of water within the well, therefore there is no pressure gradient within the well (Groundwater Pumping Tests Design and Analysis, Walton, 1987) 4 The water level data does not show any influence from pumping of the supply well The evidence which would have indicated such influence would have been significant positive or negative fluctuations The lack of influence on the water table by the supply well during normal use may indicate the presence of an aquitard between the upper unconfined water-bearing zone and a lower, confined water-bearing zone screened by the supply well If present, the aquitard may prohibit the downward migration of petroleum hydrocarbons If you have any questions or comments, please call me at (916)444-0123 Sincerely, BROWN AND CALDWELL lr Tina Bauer )/ Project Manager TBjw cc Mr Terry Tardrti, T&T Trucking, Inc Use or disclosure of data continued on this sheet is subject to the restriction specified at the beginning of this document KI EUVM62T i ICORRESMTR-2 DOC