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Mr. Gary Leirmoe <br />January 22, 2001 <br />Page Two <br /> <br />The upper level of the digester building will be physically separated from the gas-handlir~g equipment <br />as defined by NFPA 820. Therefore, it will require only 6 ac/hr of continuous ventilatior) to become <br />unclassified per the NEC, <br /> <br />Based on these recommendations, additional work will be required. The additional work is summarized as <br />follows: <br /> <br />1. Physical separation of the upper and lower level; <br /> <br />This wilt require excavation for a new entry into the lower level, as well as removing the existing <br />stairway and closing off the stairway floor opening. The grate between the upper and lower level must <br />be removed. If an.opening is required for removal of pumps, the grate should be replaced with a <br />gasketed, gas-tight cover. All remaining penetrations should be sealed to be gas-tight. <br /> <br />2. Lower Level: <br /> <br />This will require a new heated make-up air unit and exhaust fan to provide 12 ac/hr c.f continuous <br />ventilation. In addition, electrical wiring and devices will have to be changed to bring the area into <br />compliance with Class 1, Division 2 per the NEC. <br /> <br />3. Upper Leveh <br /> <br />This will requi~e a new heated make-up air unit and exhaust fan to provide 6 ac/hr of continuous <br />ventilation. This room will be unclassified per the NEC, so the electrical wiring and devices in the area <br />are currently in compliance. <br /> <br />If the City would prefer to phase in the improvements over the next two years and the City's building official <br />agrees, we recommend one of the following options: <br /> <br />1. Make ail improvements in the digester building this year, then make the improvements in the grit and <br /> screen room next year; or <br /> <br />2. Make the improvements in the screen and grit room and part of the digester building improvements <br /> this year and make the remaining digester building improvements next year. <br /> <br />will call you to discuss and address any of your comments or questions regarding this matter, <br /> <br />Sincerely, <br /> <br />Howard P,. Green Company <br /> <br />Kevin F. Newman, P.E. <br /> <br />attachment <br /> <br />c: Terry Maurer - Howard R. Green Company <br /> <br />Ltr-011701-Leirmoe.doc <br /> <br />Howard R, Green Company <br /> CONSULTING ENGINEERS <br /> <br /> <br />