V/ater is pimped through the center of either E (1 5/16") or A 

 (1 5/8") size drill rod by a water swivel on the upper end of the drill- 

 rod string. This swivel allows rotation of the drill string in the hole 

 without twisting the hose which carries the water from the pump to the 

 drill -rod string. 



When drilling in sandy material, wash water is no longer returned up 

 the hole as the washbit passes beyond the end of the casing because of 

 the porosity of the sand. The drill-rod string is removed from the hole 

 in 10-foot sections, and a sampler is lowered into the hole by reassembl- 

 ing the drill string. A sample is taken beyond the end of the casing 

 before advancing it 5 more feet. 



Samplers are of several types. The type to use depends on the sedi- 

 ment being sampled and the preference of the operator. Figure 8 shows 

 two more common samplers used in shallow holes. The split-spoon sampler 

 is used in sand, clay or till; the Shelby tube works best in silt or clay. 



A variety of sample retainers are used in the shoe of the split spoon. 

 The more successful ones are also pictured in Figure 8. The metal spring 

 fingers with the plastic bags surrounding the fingers proved most depend- 

 able. Prophylactics of latex rubber are far superior to the plastic bags 

 sold as retainers, and are a recommended substitute. When working in 

 clays with either the Shelby tube sampler or the split spoon, no retainer 

 is necessary if the ball check valve in the head of the split spoon and 

 the Shelby tube is kept free of sediment. The ball valve should be flush- 

 ed clean with water before sampling to prevent sediment from being driven 

 into it. Unless a heavy-duty, split-spoon sampler is used near gravel or 

 till, metal fatigue caused by forced penetration of the sampler will 

 result in a lost sampler. 



The presence of clay or fine silt the entire length of a drill hole 

 eliminates the need for casing. Clay is self -casing and retains the hole 

 even if drilling is suspended overnight. Many crews use a drilling mud to 

 case sandy parts of a hole, because mud mixed with water fills the pores 

 of the sand and causes the hole to retain its shape. In very porous sand, 

 this process may be tedious. Here, the choice between drilling mud or 

 steel casing depends on the type of equipment available and the preference 

 of the crew. The use of mud simplifies drilling deeper holes as there 

 is no casing to be retrieved. However, certain pumps cannot handle the 

 clay -water mixture. 



A common problem results from sandy till or gravel under a thick layer 

 of glaciomarine clay. Because the clay part of the hole is not cased, and 

 could be cased only with great difficulty, there is a water loss when the 

 washbit passes from the clay into the more porous material beneath. This 

 usually blocks further drilling, and is one of the more difficult problems 

 of using nonrotary, limited-capability equipment. 



