TM 5-814-7
particular soil, the compatibility of the soil and the waste
-Proximity to private or community water
to be treated, and the capacity of the soil to receive and
supply wells or reservoirs
transmit water (hydraulic capacity). These variables are
Climate
described in detail in Overcash, 1981, a definitive text on
-Location upwind of large populations
land treatment. In addition to identifying the factors
-Extremely wet or cold conditions
limiting land treatment as a disposal option, Overcash
Topography -Steep slopes -Broken terrain
presents detailed procedures for the design of land
Soils
treatment systems for all waste types.
-Thin soil above ground-water
(3) The third limiting factor, regulatory
-Saline soils
restrictions concerning food-chain crops, is also
-Highly permeable soils above shallow
complex. For most hazardous constituents, RCRA
ground water
stipulates that there can be no uptake by food-chain
-Soils with extreme erosion potential
crops and no greater concentration of the constituents in
Land use -Areas formerly used for landfills
the crop than is found in the surrounding area. As
-Areas
contaminated
with
summarized in 40 CFR 264.276, the owner/operator of a
residues from past chemical spills or waste
land treatment unit must demonstrate that there is no
treatment processing
c. Procedures. Land treatment is both a method of
"substantial risk to human health caused by the growth of
such crops in or on the treatment zone."
disposal and a treatment mechanism.
It involves
(a) This objective may be met either by
applying a waste to land and incorporating it into the soil,
demonstrating that hazardous constituents will not be
where it undergoes biochemical action which attenuates
transferred to food or feed portions of a crop, or will not
its negative impact on the environment. A number of
occur in greater concentrations in or on identical crops
techniques are available for applying the waste,
grown on untreated soils under similar conditions in the
depending largely on the wastewater content, but also
same region. Both of these options require that the
hinging on such considerations as soil properties,
following be addressed: crop uptake, physical adherence
topography and climate.
to the crop, and direct ingestion of contaminated soil by
(1) For land application purposes, wastes are
grazing animals.
generally classified as
(b) With respect to hazardous wastes
* Liquid (less than 8 percent solids, with particle
diameters less than 1 inch)
containing cadmium, even more restrictive limitations
* Semiliquid (8 to 15 percent solids and/or particle
apply. If such wastes are to be land treated, the
diameters greater than 1 inch)
following criteria must be met:
* Solid (greater than 15 percent solids)
A pH of at least 6.5
(2) Application of liquid wastes is generally
An application rate of no more than 0.44
accomplished by either spraying the waste on the land
lb/acres/yr
with sprinklers or by using flood or furrow irrigation
Limits on cumulative application, as dictated
techniques. Semiliquid sludges are normally applied by
by the soil's caution exchange capacity
surface spreading, with subsequent incorporation into
Special conditions for animal feed (specific
the soil, or by subsurface injection 4 to 8 inches below
details are outlined in 40 CFR 264.276)
the soil surface. Low-moisture solids are spread on the
(4) The last limiting factor, environmental
surface and later incorporated into the soil (figure 5-3).
conditions, actually refers to a number of natural features
(3) Waste volatility, site terrain and weather
that restrict the siting of a land treatment unit. The
conditions may dictate the choice of other application
precautions concerning location of landfills in karst
techniques, regardless of the water content of the waste.
terrain or seismic zones 3 and 4 also pertain to land
For example, highly volatile wastes should not be applied
treatment facilities (see para 5-2b(2)).
In general,
by irrigation or surface spreading, but be injected at least
limiting environmental conditions should either be
6 inches below the soil surface. On steep slopes or in
avoided or should serve as design constraints in
freezing weather, alternatives to spray irrigation will
developing the facility layout. These include:
likewise be required.
The objectives in any land
Hydrogeologic Conditions
treatment system, regardless of method used, are
-Bedrock outcrops
uniform application of wastes, and use of application
-Irregularities such as fissures or faults -
rates within the assimilative capacity of the soil.
Aquifer recharge zones
-Flood-prone areas such as river flood plains
-Wetlands
-Karst terrain
-Seasonally high water tables (< 4-6 ft)
5-8
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