were located inside the reservoir room at the southern end of the barge, which 

 is where the large water intakes are located. One orifice was installed outside the 

 barge (on a pile), and the other was installed inside the barge, just inside one of 

 the large intakes to the western reservoir. See Figure 10. 



The purpose of two gages was to determine whether or not the water level in 

 the western reservoir truly reflected the outside water level, so that it might provide 

 a protected environment for the establishment of a permanent station using 

 standard equipment. It was initially thought that the outside orifice would not 

 survive the severe winter conditions. 



After a year of operation, tidal analysts of the Physical Oceanography Division 

 determined that the inside water level does accurately reflect the true outside 

 water level. In addition the outside orifice survived the winter conditions so well 

 that it is now believed that an outside orifice can be permanently maintained. In 

 July, 1990, a full NGWLMS was installed inside the STP. In addition, the outside 

 orifice is being used, and a digital bubbler gauge, using a high precision 

 Paroscientific pressure sensor, is measuring the pressure variation in the gas- 

 purged tubing. This station is the United States' first permanent year-round tide 

 station north of the Aleutians! 



Future projects in this area could be the establishment of other stations, on 

 facilities like the Arco STP if they exist at other oil fields, or on some of the oil 

 companies' artificial islands. Investigations should be conducted to determine 

 the number and locations of these types of facilities and analyses made of their 

 suitability as strategic GLOSS stations. 



3.2 Thermal Bench Marks 



A new type of bench mark was developed inhouse through the application of 

 existing technology. It is being tested for use in remote areas where no bedrock 

 or permafrost exists, and Class A type bench marks are too difficult or expensive 

 to install. The new type bench mark, called a thermopile or "thermo" bench mark, 

 is a type of bench mark specifically designed to resist the frost heave (vertical) 

 forces generated by seasonal freeze/thaw cycles, specifically in Arctic regions. 

 The thermo bench mark operates on a heat transfer mechanism and is generically 

 known as a two-phase closed thermosyphon. Ten foot of a 1-inch diameter iron 

 pipe is sealed and pressurized to 600 psi with carbon dioxide gas. The process 



15 



