Borrow  Areas When material is to be borrowed from adjacent areas,  make  borings  carried  2  to  4  feet  below  the anticipated depth of borrow in these areas. Classify and test samples for water content, density, and strength. Explore areas within a reasonable haul from the site for  possible  sources  of  select  material  suitable  for  use as a subbase. Exploration procedures are similar to those described for subgrades. You need test pits or large auger borings drilled with power augers for gravelly materials. RECOMMENDED  PROCEDURES FOR SOIL SURVEYS The following guide and step-by-step procedures will help the military engineer when conducting soil surveys: l  considerations  include  soil  types,  securing  of samples, density and moisture content of soil in place, drainage  characteristics,  and  depth  to  groundwater  and bedrock. l Published information includes geological and topographic reports with maps and agricultural soil bulletins with maps. These require careful interpretation and knowledge of local terms. Aerial photographs used to   predict   subsurface   conditions   and   previous explorations  for  nearby  construction  projects  are  also useful. l Field information requires general observation of road  cuts,  stream  banks,  eroded  slopes,  earth  cellars, mine shafts, and existing pits and quarries. Test holes may be made with a hand auger or a power auger, if necessary and available. Test pits are necessary where a hand auger cannot penetrate or where large samples are required. .  Local  inhabitants,  preferably  trained  observers such as contractors, engineers, and quarry workers, can provide  valuable  information. Preparation Planning  of  the  general  layout  will  determine  the extent of the various soil types, vertically and laterally, within the zone where earthwork may occur. Large cuts and  fills  are  the  most  important  areas  for  detailed exploration. . Airfield exploration. Place borings at high and low spots, wherever a soil change is expected and in transitions from cut to fall. There is no maximum or minimum  spacing  requirement  between  holes;  however, the  number  of  holes  must  be  sufficient  to  give  a complete  and  continuous  picture  of  the  soil  layers throughout the area of interest. As a general rule, the number of exploration borings required on a flat terrain with uniform soil conditions will be less than in a terrain where the soil conditions change frequently. Exploration borings should be conducted at the point of interest and located in a manner to get the maximum  value  for  each  boring.  This  may  require exploration boring in the centerline as well as edges of runways or roads, but no specific pattern should be employed except as perhaps a staggered or offset pattern to permit the greatest coverage. It is accepted policy to conduct the exploration borings at the edge of existing pavements,   unless   these   pavements   have   failed completely. In this case, the reason for the failure should be found. l  Depth  exploration.  Take  a  cut  section  4  feet below subgrade, if possible, and a fill section 4 feet below  original  ground  level,  if  possible.  Effort  should be made to locate the groundwater table. Procedures l l l Log the exploration holes or pits. Locate  and  number  the  samples. Determine the elevation and exact location of each hole and tie into the site layout. Technical Soils Report A  good  program  for  soils testing not only requires that  careful  and  complete  tests  be  performed  but  also that the tests be completed as quickly as possible and that the data be clearly and accurately presented in a technical soils report. The organization and presentation of the soils report is highly important. The report must be well-organized and must be presented in a logical and concise format with emphasis on technical conclusions. For further discussion and a suggested outline for a soils report, you should refer to Materials Testing, NAVFAC MO-330. 16-10