MIL-HDBK-1003/8A
required to clearly show the intent of the Shallow Trench Heat Distribution
System. Also indicate any obstructions in the path of the distribution system
that the Contractor may have to work around.
4.3.5
Valve Manholes. Extend valve manholes at least 9 to 12 inches (175
to 305 mm) above finished grade to prevent seasonal runoff from entering
except where trench will be a pedestrian walk, in which case the vault cover
will be flush with the trench covers.
4.3.6
Inspection Ports. Where required, provide inspection ports at
appropriate locations to enable the user to observe drains or expansion at
loops or locations requiring frequent (monthly) observation.
4.3.7
Crossings. At all road and railroad type crossings, provide
required slab thickness for railroad crossings and H-20 loading for street
crossings. Review railroad track removal/replacement with respective
authority and coordinate all activities. Road and rail crossing where
maintenance of traffic is critical may be accomplished by jacking using an
acceptable conduit/tunnel.
4.3.8
Precast Concrete Shallow Trench Options. In addition to or in
combination with a poured-in-place concrete shallow trench system, a precast
or prefabricated shallow trench system consisting of precast concrete covers,
concrete trench, or supports may be specified. If the designer selects this
option, he must include special details and specification requirements of the
precast system and the transition between the poured-in-place and precast
system.
4.4
Manholes
4.4.1
Drainage. Provide sump pumps in manholes. Units should discharge
by buried piping to nearest storm sewer if possible. Where not economical to
discharge to storm sewer, pumps are to discharge above grade to splashblocks.
Plan discharge locations carefully so water will not be placed over tunnel
tops, sidewalks, etc. Use sump pumps capable of passing 3/8-inch (12 mm)
solid (sphere) minimum. Adjust float switches so the pumps start
sequentially, reducing electrical line surge. Coordinate power requirements
with electrical designer and provide tell-tale light above ground to indicate
that power is available to sump pumps.
4.4.2
Waterproofing. If portions of manholes are installed below the
water table, waterproof that portion below the water table.
4.4.3
Pipe Entry. Pipe entry, for buried pre-engineered systems piping,
shall be in accordance with Figure 24.
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