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ovv <br /> CLEARWATER <br /> G R O U P I N C <br /> Ennironmen ta! 5ernices <br /> The ORP over the past quarter ranged from a low of +14 1 0 millivolts (mV) in IW-3 recorded <br /> in February to a high of+366 1 mV in IW-11 recorded on January 10, 2006 <br /> Conclusions for the Fourth Quarter <br /> ■ Groundwater flow and direction are consistent with previous observations made during <br /> the same period of the hydrologic cycle (SE at approximately 0 015 ft/ft) <br /> ■ Groundwater samples were collected from all eight monitoring wells and submitted for <br /> analysis of TPHg, BTEX and MTBE <br /> ■ Analytical concentrations reported for the samples collected from all of the monitoring <br /> wells increased (with the exception of xylenes in MW-7 and MTBE in MW-5B) since the <br /> last sampling event conducted on December 9, 2005 <br /> ■ The samples collected from MW-2, MW-3, MW-4 and MW-6 did not contain detectable <br /> concentrations of any of the constituents of concern above the standard laboratory <br /> reporting limit for each compound analyzed <br />. ■ O&M site visits were conducted on January 10, February 7 and March 8, 2006 <br /> ■ DO levels increased in the monitoring wells and increased in the ISOCTM system wells <br /> ■ ORP values remained positive in the monitoring and iSOCTm system wells <br /> Recommendations <br /> As previously stated in the Third Quarter 2005 Groundwater Monitoring and iSOC Remediation <br /> Activity Report prepared by Clearwater dated December 30, 2005, the results of the indirect <br /> geochemical study performed in conjunction with the third quarter groundwater monitoring <br /> event indicated that there is some microbial growth occurring within the hydrocarbon plume <br /> sourcing from the project site The number of colony forming units per milliliter reported was of <br /> a magnitude of 102 to 104. For greater hydrocarbon consumption the ideal range of colony <br /> forming units per milliliter should fall between 105 and 106 The concentration of nutrients such <br /> as ammonia as nitrogen and orthophosphate which were reported during the third quarter of 2005 <br /> may be a lvnitmg factor for microbial growth Low levels of these nutrients could potentially <br /> limit biodegradation activity even if all other growth needs such as adequate dissolved oxygen <br /> (electron acceptor) levels and petroleum hydrocarbon sources are available <br /> ZB178I 7 of 10 May 2006 <br />