FLOOD02929

• County: Statewide
• Community: na
• Basin: Statewide
• Title: Manufactured Home Installation in Flood Hazard Areas
• Date: 9/1/1985
• Prepared By: FEMA
• Floodplain - Doc Type: Educational/Technical/Reference Information

Figure 3.3 Earth Fill and ElevateOFoundatlon

Figure 3.4 Earth Fill Site Plan

The earth fill elevation approach is widely used
throughout the United States in low velocity
"backwater" areas, Another example is shown in
Figure 3,5,

Figure 3.5 Earth Fill

Prior to filling, the area upon which earth fill is
to be placed, including a five foot strip measured

horizontally beyond and contiguous to the top line
of the earth fill, should be cleared of standing trees
and snags, stumps, brush, down timber, other
vegetation, and all objects on and above the
ground surface or partially buried as shown in
Figure 3,6, The area should also be stripped of
topsoil and debris,

Cleared Surface

}Sft.

~ Sft.

After Fill

Figure 3.6 Fill Areas

Earth fill material should be of a selected type,
preferably granular and free-draining, The fill
should be placed in layers not exceeding 12
inches with each layer compacted with rollers or
vibrating compacting equipment. Earth fill selec-
tion and placement should include consideration
of the effects of saturation from floodwaters on
slope stability, uniform and differential settlement,
and scour potential.

The minimum distance from any point of the
building perimeter to the edge of the fill slope
should be either 25 feet or twice the depth of fill
at that point, whichever is greater,
Slopes for granular fills should be no steeper
than one and a half feet horizontal to one foot ver-
tical unless data justifying steeper slopes are
developed, For slopes exposed to flood velocities
of less than five feet per second, grass, vine cover,
weeds, brush, and similar vegetation undergrowth
will provide adequate scour protection, For
velocities up to 10 feet per second, stone or rock
slope protection should be provided. Fill should
not be used in areas subjected to velocities higher
than 10 feet per second,
Depending upon state or' local regulations, in-
dividual sewage systems (septic systems) may be
prohibited in watersheds of the public water supply
system, Where septic systems are allowed the use
of earth fill will most likely be precluded due to its
impact on the performance of the individual
sewage system, This is because the additional
earth fill will affect the absorption rate of the
system, If earth fill is to be considered in conjunc-
tion with individual sewage systems, the local
building department should be consulted,

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