action must be taken to close the isolation valves on drains located below the CHT tank overflow line discharge and divert upper deck drains over- board to preclude flooding of space. In the event of leakage or snagging of the transfer hoses, close valve F (shown in figures 8-5 and 8-6) at the deck connection only (closure of pier valve may cause the  discharge  hose  to  rupture).  Line  up  pump discharge  diverter  valve  C  for  overboard discharge,  to  prevent  overflow  or  backup  of drains located below the tank overflow. At-Sea  Mode In order to set the CHT system up for the At- sea mode (refer to figures 8-5 and 8-6) set soil and waste drain diverter valves H and J to the OVER- BOARD position. Open pump discharge valves B and set pump discharge diverter valve C to the overboard position. Check to insure that gag scup- per valve at the hull in the pump discharge line is open. Set the discharge pump controller selec- tor  switches  to  the  MAN1  position.  After  the pumps lose suction, set both controller selector switches to the AUTO position. Open the tank washdown supply valve and wash the tank for 30 minutes. Close the tank washdown supply valve. Set the controller selector switches to MAN1 posi- tion. After loss of pump suction, set controller switches in the OFF position. Close pump suc- tion valves A, discharge valves B, and, in the strainer  system  only,  close  the  inflow  stopvalves G. For  CHT  systems  outfitted  will  comminutors and aeration systems, secure the comminutor after setting the soil drain diverter valves. Close air blower discharge valve M and secure air blower, or close ship supply valve N after tank washdown procedures have been completed and the pump has lost suction. If an air aspirator system is in- stalled,  shut  the  system  down  and  secure  the aspiration pump. The CHT system is now secured with all soil and waste being discharged overboard through the gravity  drainage  system. For  additional  information  on  the  CHT system and its components, refer to the manufac- turer’s   technical   manuals   and   Naval   Ships’ Technical Manual, Chapter 593. NOISE  POLLUTION Hearing loss problems have been and continue to be a source of concern within the Navy, both ashore and afloat. In the Navy the loss of hear- ing can occur from exposure to impulse or blast noise  (i.e.,  gunfire,  rockets,  etc.)  or  from  con- tinuous or intermittent sounds such as jet or pro- peller  aircraft,  marine  engines,  boiler  equipment operations, and any of a myriad of noise sources associated with industrial type activities (such as shipyards).  Hearing  loss  may  be  temporary,  and will disappear after a brief period of nonexposure, or it may become permanent through repeated exposures to intense noise levels. The loss of hear- ing sensitivity is generally in the higher frequen- cies  of  4000-6000  Hertz  (Hz)  with  many  people sustaining extensive impairment before the all im- portant  speech  range  of  500-3000  Hz  is  ap- preciably   affected. The  Navy  recognized  noise  pollution  to  be  a problem  and  started  to  combat  it  through  the Hearing Conservation Program. The main pur- pose of this program is to establish and imple- ment  an  effective  occupational  noise  control  and hearing conservation program which has as its goal the elimination/prevention of hearing loss. HEARING CONSERVATION PROGRAM Hearing  loss  associated  with  exposure  to hazardous  noise  and  the  high  cost  of  compensa- tion claims have highlighted a significant problem which  requires  action  to  reduce  or  eliminate hazardous occupational noise levels. An effective occupational noise control and hearing conserva- tion program will prevent or reduce the exposure of personnel to potentially hazardous noise. Such programs will incorporate the following elements: 1. Identification of hazardous noise areas and their sources. 2.  Elimination  or  reduction  of  noise  levels through the use of engineering controls. 3. Periodic hearing testing of noise-exposed personnel to evaluate program effectiveness. 4. Education of all hands in the command’s program and their individual responsibilities. 5. Strict enforcement of all prescribed occupa- tional  noise  control  and  hearing  conservation measures   including   disciplinary   action   for violators and supervisors, as necessary. Chapter  8—ENVIRONMENTAL  POLLUTION 8-19