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

Bed Dimensions: A = 6 ft
B = 65 ft
Step 6: Calculate Mound Dimensions.
a. Mound Height
Fill Depth (D) = 1 ft (Table 7-9)
Fill Depth (E) = D + [(Slope) x (A)]
= 1 ft + C(O.06) x (6)1
= 1.4 ft (This is only approximate. Criti-
cal factor is construction of level bed
bottom.)
Bed Depth (F) q 9 in. (min) (Table 7-9). (A minimum of 6
in. must be below the inverts of the dis-
tribution laterals.)
Cap at Edge of Bed (G) = 1 ft (min) (Table 7-9)
Cap at Center of Bed (H) = l-1/2 ft (min) (Table 7-9)
b. Mound Perimeter
Downslope Setback (I): The area below and downslope of the
absorption bed and sloping sites must be sufficiently large
to absorb the peak wastewater flow. Select the proper
natural soil infiltration
case, the natural soil
rate
infiltration
from Table 7-10. In
rate is 0.25 gpd/ft
his
t
.
Upslope Setback (J) = (mound height at upslope edqe of bed)
X (3:l slope) ’ ’ -
Side Slope Setback (K) =
=
=
=
=
L(D) + (E) + (G)l x (3)
(1.0 + 0.75 + 1.0) x (3)
(2.75) x (3)
8.25 ft (This will be less because
of natural ground slope, use 8 ft.)
(s;~;;;' height at bed' center) x (3:l
1
2
(D) + (E)
+ (F) + (H) x (3)