10 January 2002
GENERAL DISTRIBUTION SYSTEM DESIGN
3-1. GENERAL. Some aspects of a heating or cooling distribution system design are similar regardless
of the system type. These aspects are covered in this chapter.
3-2. SITE SOIL SURVEY. After general routing has been proposed and before specific design has
begun, a detailed soil survey will be conducted for all distribution systems.
a. The survey will be made after the general layout of the system has been determined, will cover
the entire length of the proposed system, and will be made by a geotechnical engineer. The geotechnical
engineer will be a registered professional engineer with a minimum of three years of experience in the field
of soil mechanics and foundation design. This engineer must also be familiar with the local soil
b. If at all possible, the survey should be conducted during the time of the year when the
ground-water table is at its highest point; if this is not possible, water table measurements will be
corrected, on the basis of professional judgement and local knowledge, to indicate conditions likely to
exist at the time of year when the water table is at its highest point. It may be necessary to dig test pits
at the worst locations to investigate the soil for evidence of high water table.
c. As a minimum, information on ground-water conditions, soil types, terrain, and precipitation
rates and irrigation practices in the area of the system will be collected. This information will be obtained
from available records at the installation. In addition, soil resistivity will be determined for
protection system design for Pre-Engineered Underground Heat Distribution Systems.
d. Information on ground-water conditions and soil types (in most cases not necessary for
Prefabricated Underground Heating and Cooling Distribution Systems and Aboveground Heat Distribution
Systems) will be obtained through borings, test pits, or other suitable exploratory means. Generally, a
boring test pit will be made at least every 100 feet along the line of the proposed system within areas of
prior construction. In open undisturbed natural areas the spacing of borings may be increased. Each
exploratory hole will extend to a level at least five feet below the anticipated elevation of the bottom of
the proposed system. If a significant difference in underground conditions
is found at adjacent
exploratory points, additional explorations will be made between those points in order to determine more
precisely where the change occurs. Upon completion of the survey, each exploration point will be
classified on the basis of the criteria presented in the guide specification for Pre-Engineered Underground
Heat Distribution Systems or in the guide specification for Heat Distribution Systems in Concrete Shallow
Trenches. The classification criteria is different for each system. Note that although classification is not
a requirement for design of Prefabricated Underground Heating and Cooling Distribution Systems or
Aboveground Heat Distribution Systems, the site survey , except for borings or test pits, must be
conducted to ensure that actual site
characteristics have been identified so that accurate plan and
profile drawings can be generated.
3-3. UTILITY INVESTIGATION. All existing, concurrently constructed and new utilities will be identified
if within 25 feet of the proposed distribution system routing. If the proposed routing crosses any utilities,
burial depths will be determined. Utility locations and depths can be verified through base personnel
familiar with utilities, base/post utility maps and by site visits. The designer is responsible for these site
visits to verify locations of utility interferences and to coordinate all other construction items with the user.
In the event utility information is not available, utility location consultants may be procured who specialize
in the location, identification and depth determination of utilities. If interferences exist, details will be
provided in the design to relocate utilities or modify system routing to avoid the interference.