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i C,eotogical recluucs Inc Page 6 Groundwater Monitoring Report • Project No 770 2 { April 30, 2003 ' Well MW-4 lies adjacent to the former UST field Figure 6- MW-4 TPH-D vs J g Groundwater Elevation suggests an inverse relationship between groundwater elevation and contaminant concentrations in well MW-4 It is noted that the groundwater elevation exceeded the screened interval of well MW-4 prior to the last two events and dilution iriay ' have been taking place Conversely, the water table lies within the screened interval of well MW-5 and this may represent a more accurate reflection of residual contamination leaching into groundwater ' Well MW-5 continues to contain the highest concentrations of detected contaminants (see Figure 7) It has not been down gradient of the former UST location for the ten monitoring events completed by GTI to date The reason for this anomaly is not known, but could be related to geologic units that slope to the west Since only one (MW-105) of the deep wells contained TPH-D, a contour diagram was not produced ' In Figure S — MW-5 & MW-105 TPH-D versus Groundwater Elevation, well MW-5 contaminant concentrations have generally correlated with changes in the water table Well ' MW-105, screened below the water table, exhibits a typically inverse relationship between contaminant concentrations and groundwater elevation GTI makes the following recommendations • Continue quarterly groundwater monitoring for determining direction and contaminant ' trends The completion of the next quarterly event will mark one full year (four consecutive quarters) of monitoring/sampling of the five wells that were installed in May 2002 • Continue monthly groundwater level measurements for one year 3.0 LIMITATIONS This report was prepared in accordance with the generally accepted standard of care and practice in effect at the time Services were rendered It should be recognized that definition and evaluation of environmental conditions is an inexact science and that the state or practice of environmental geology/hydrology is changing and evolving and that standards existing at the present time may change as knowledge increases and the state of the practice continues to improve Further, that differing subsurface soil characteristics can be 1 experienced within a small distance and therefore cannot be known in an absolute sense All conclusions and recommendations are based on the available data and information. The tasks proposed and completed during this project were reviewed and approved by the local regulatory agency for compliance with the law No warranty, expressed or implied, is made 1