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the controller be bypassed (as long as some surge voltage protection is still provided) to allow the motors to use the line frequency directly rather than a recreated waveform 4 2 2 3 Remote Pump Restart Because of the frequent power disruptions (see Sec 4 1 7 1, Retuning Problems or Issues), modifying the control of the extraction wells, to include an remote VFD pump re-start option should be considered Although it is recognized that in some cases the cause of the pump shutdown should be confirmed, if the operator has clear indication that power fluctuations occurred at the time the pumps went down, then an inspection is not necessary and the remote restart capability could be used This would potentially save 100 person-hours per year (25 outages times 4 hours per restart) 4 2 2 4 Conduit Protection Seasonal cattle grazing is allowed in the site area Conduit to the extraction well heads have been severed by cattle rubbing up against the well heads Reinforcing the attachment of the conduit to the well head should be considered to make the well heads `cattle-proof 4 2 3 Operating Parameter Changes 4 2 3 1 Air Stripper Operation Currently two blowers, with a third on standby, are providing air to the two air strippers The air strippers were designed to reduce TCE levels from 250 ppb to 0 78 ppb The number of gas transfer units (N) is a measure of the capacity to remove contaminants by air stripping Given information about the contaminant (including concentration), packing material, and the air and water flow rates both the required and actual (operational) number of gas transfer units can be estimated The higher the N, the more ability the stripper has to remove contaminants As currently configured, the air strippers are estimated to offer a 5 7 N capacity The current level of TCE in the influent is about 20 ppb The Ns needed to reduce the TCE levels from 20 ppb to 0 78 ppb are estimated to be 3 4, less than what is currently available Thus, the strippers have excess capacity to remove TCE Reducing the depth of the packing would result in lower energy consumption by the blowers and estimated electricity savings of about $300 per month The cost of removing packing would have to be recovered within a relatively short period of time to justify the change The cost (mostly labor) of removing the packing was not estimated Reducing the air input to the strippers should also be evaluated If the air rate is reduced by half with, the input concentration of TCE at 20 ppb, and the required effluent concentration remaining at 0 78 ppb, an estimated capacity of only 0 8 Ns are needed Performance curves should be obtained from the manufacturer to determine if the blower will operate efficiently and correctly at the reduced rate This would also result in lower energy consumption Using a combination of both reduced airflow and reduced packing should also be evaluated If both the airflow rate and the packing height can be reduced, a single blower may M dble to pio-vide sullil,lent air too booth all Jtrippels at Mr, 1VWer required pres,�?lLre T11e NT values are based on a flow rate through each air stripper of 13,425 cfrn (from the AE design analysis) and 4-inch of water pressure drop across the packing (observed during the site visit) If the actual values are different, the above figures need to be adjusted accordingly Finally, if at a later time the influent concentration approaches the concentration that can be reinfected, it may be possible to strip only a portion of the water and recombine it with the other portion for reinfection 06/07/99 Page 10 of 14