Prudhoe Bay, AK - only because that is a unique Arctic facility as explained in 

 Section 3.1. A possible installation of an NGWLMS Data Collection Platform 

 (DCP) with a bubbler system under the ice is illustrated in Figure 6. 



The few existing Arctic marine facilities are typically gravel causeways extend- 

 ing out into the shallow waters, sometimes miles from shore. They are built with 

 a low profile and sloping sides to minimize damage from ice pack movement. 

 Sheet pile is used infrequently along the causeways for various purposes. 

 However, ice scouring and the shallow water depths make it impossible to operate 

 through the winter any system attached to the sheet pile. Even when wells are 

 protected from destruction by ice movement, it is very difficult to prevent the water 

 from freezing inside the wells. 



There have been a few stations designed for year round operation on the 

 gravel causeway type facilities. A sump-type design was utilized to avoid some 

 of the problems discussed above. The installation cost of this type station is very 

 high (several hundred thousand dollars) and none have been built. 



2.3.2 Bench Marks 



Bench mark stability is essential to preserving the datums established at a 

 site. Bench mark stability has been a problem in the Arctic region due to the lack 

 of bedrock and a large active zone. The lack of bedrock (and large concrete 

 structures) eliminates the most stable, easily established type of bench mark. The 

 large active zone, the layer of earth where a jacking action is produced by the 

 freeze-thaw cycle, renders all monument and pipe marks, and a large number of 

 Class B (unsleeved) deep rod marks, unstable. Permafrost, in itself, does not 

 cause instability. High stability bench marks can be established in permafrost 

 areas by anchoring the bench mark into the permafrost. In areas where per- 

 mafrost does not exist. Class A (sleeved) bench marks can be established which 

 are insulated from the active zone. Establishing permafrost-anchored and Class 

 A bench marks is expensive and difficult to do in remote areas due to the need 

 to augur a 1-inch diameter guide hole. 



The remoteness of the arctic region has obvious impact on site accessibility, 

 utilities service, logistics, available resources, maintenance, etc. all of which can 

 be significant cost drivers in addition to installation costs. 



