HomeMy WebLinkAboutMound Design Procedure E-19E-19
MOUTJD DESIGN PROCEDURE
(For Flows up to 1200 gpd)
A. Sewage Flow Rate
See D-7 or 1-3, A, or 5, or use
metered value; Flow Rate =
<^0 0 gpd
B. Septic Tank Liquid Volume
(see C-3 or C-5) /£fao gallons
C. Soil Characteristics
1. Depth to restricting layer
such as seasonally saturated
soil, bedrock, coarse soil,
etc. ; 7^ inches
2. Depth of percolation tests;
/4 inches
3. Number of percolation test
holes; V holes
4. Ave. percolation rate;
/?. 2 mpi
5. Landslope = 3 %
D. Rock Layer Dimensions
1. Multiply gpd by 0.83 to
obtain required area of
rock layer;
(,0 0 gpd X 0.83 ° SOO sq ft
2. Select width of rock layer
(10 feet or less) = /O feet
3. Length of rock layer = Area
■1 Width-T££_sq ft -j- tO ft
" SO ft
E. Rock Volume
1. Multiply rock area by rock depth
to get cubic feet of rock;
SOO sq ft X O.-ySit = 375cu ft
2. Divide cu ft by 27 cu ft/cu yd
to get cubic yards; /3. 9
3. Multiply cubic yards by 1.4 to
get weight of rock in tons;
fjcu yds X 1.4 “ /y, y tons
F. Pressure Distribution System
1. Select number of perforated
laterals _ _£_ _ _
2. Select perfor"..ion spacing
= 3_ _ft
3. Select perforated lateral
length; Note if manifold is
at end of rock layer, lateral
length is rock layer length
less half a perforation
spacing. If manifold is in
center of rock layer, lateral
length is one-half rock layer
length less half a perforation
spacing. Perforated lateral
length = 23.5 ft.
4. Divide lateral length by perfor
ation spacing to get number of
perforations per lateral
5 feet f _3_feet = 2 porfs
Note: last perforation must be
in end cap, (see page E-14)
5. Multiply perforations per
laternl by number of laterals
to got total number of
perforations;
2 pcrfs/lat X ^ lats = ^2
uur/i
•/‘i"
6. Determine required flow rate
by multiplying number of
perforations by flow per
perforation (see page E-17)
perfs X .7/ gpm/perf =Jf^gpm
7, Select minimum required lateral
diameter from table on Page E-17;
enter table with perforation
spacing, perforation diameter,
and number of perforations per
lateral. Select minimum
diameter for perforated lateral
= / y<f " inches t//<f z'/i"
G. Basal V/idth
1. Percolation rate in top 12
inches of soil is /?. ^mpl
2. Select allowable soil loading
rate from table on page E-lb;
O. (50 gpd/f t^-