On-Site Wastewater Treatment and Disposal Systems - Forced ...

the top soil. It is only in the more slowly permeable soils where addi-
tional basal area is required, and a conservative design may be appro-
priate for these situations.
TABLE 7-10
INFILTRATION RATES FOR DETERMINING MOUND BASAL AREA (4)
Natural Soil Texture
Sand, Sandy Loam
Loams, Silt Loams
Silt Loams, Silty Clay Loams
Clay Loams, Clay
d. Effluent Distribution
Percolation Infi 1 trati on
Rate Rate
ml n/in. gpdlft
O-30 1.2
31-45 0.75
46-60 0.5
61-120 0.25
Although both gravity and pressure distribution networks have been used
in mound systems, pressure distribution networks are superior (4)(24)
(25). With pressure distribution, the effluent is spread more uniformly
over the entire absorption area to minimize saturated flow through the
fill and short circuiting, thus assuring good treatment and absorp-
tion. Approximately four doses per day is suggested (25). The design
of pressure distributed networks is found in Section 7.2.8.
e. Porous Media
The porous media placed in the absorption bed of the mound is the same
as described in Section 7.2.2.3.
f. Inspection Pipes
Inspection pipes are not necessary, but can be useful in observing pond-
ing depths in the absorption bed (see Figure 7-6) of the mound.
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