CODES

ADOPTS WITHOUT AMENDMENTS:

International Private Sewage Disposal Code 2012 (IPSDC 2012)

Copyright

Preface

Effective Use of the International Private Sewage Disposal Code

Legislation

Chapter 1 Scope and Administration

Chapter 2 Definitions

Chapter 3 General Regulations

Chapter 4 Site Evaluation and Requirements

Chapter 5 Materials

Chapter 6 Soil Absorption Systems

Chapter 7 Pressure Distribution Systems

Chapter 8 Tanks

Chapter 9 Mound Systems

Chapter 10 Cesspools

Chapter 11 Residential Waste Water Systems

Chapter 12 Inspections

Chapter 13 Nonliquid Saturated Treatment Systems

Chapter 14 Referenced Standards

Appendix A System Layout Illustrations

Appendix B Tables for Pressure Distribution Systems

The provisions of this chapter shall govern the design and installation of mound systems.
A minimum of three soil borings per site shall be conducted in accordance with Chapter 4 to determine the depth to seasonal or permanent soil saturation or bedrock. Identification of a replacement system area is not required.
A mound system shall be prohibited on sites not having the minimum depths of soil specified in Table 902.2. The installation of a mound in a filled area shall be prohibited. A mound shall not be installed in a compacted area or over a failing conventional system.

TABLE 902.2
MINIMUM SOIL DEPTHS FOR MOUND SYSTEM INSTALLATION

RESTRICTING FACTOR MINIMUM SOIL DEPTH TO
RESTRICTION (inches)
High ground water 24
Impermeable rock strata 60
Pervious rock 24
Rock fragments (50-percent volume) 24
For SI: 1 inch = 25.4 mm.
Percolation tests shall be conducted at a depth of 20 inches to 24 inches (508 mm to 610 mm) from existing grade. Where a more slowly permeable horizon exists at less than 20 inches to 24 inches (508 mm to 610 mm), percolation tests shall be conducted within that horizon. A mound system shall be suitable for such site condition where the percolation rate is greater than 60 minutes per inch and less than or equal to 120 minutes per inch (2.4 min/mm to 4.7 min/mm).
Percolation tests shall be conducted at a depth of 12 inches to 18 inches (305 mm to 457 mm) from existing grade. Where a more slowly permeable horizon exists within 12 inches to 18 inches (305 mm to 457 mm), percolation tests shall be conducted within that horizon. A mound system shall be suitable for such site condition where the percolation rate is between 3 minutes per inch and 60 minutes per inch (0.12 min/mm and 2.4 min/mm).
Percolation tests shall be conducted at a depth of 20 inches to 24 inches (508 mm to 610 mm) from existing grade. Where a more slowly permeable horizon exists at less than 20 inches to 24 inches (508 mm to 610 mm), percolation tests shall be conducted within that horizon. A mound system shall be suitable for such site condition where the percolation rate is between 0 minutes per inch and 60 minutes per inch (0 min/mm and 2.4 min/mm).
A minimum of 24 inches (610 mm) of unsaturated natural soil shall be over creviced or porous bedrock.
A minimum of 24 inches (610 mm) of unsaturated natural soil shall be present over high ground water as indicated by soil mottling or direct observation of water in accordance with Chapter 4.
A mound shall not be installed on a slope greater than 6 percent where the percolation rate is between 30 and 120 minutes per inch (1.2 and 4.7 min/mm). The maximum allowable slope shall be 12 percent where there is a complex slope (two directions).
The mound shall be located so the longest dimension of the mound and the distribution lines are perpendicular to the slope. The mound shall be placed upslope and not at the base of a slope. The mound shall be situated so the effluent is not concentrated in one direction where there is a complex slope (two directions). Surface water runoff shall be diverted around the mound.
A minimum of 60 inches (1524 mm) of soil shall be present over uncreviced, impermeable bedrock. Where the soil contains 50 percent coarse fragments by volume in the upper 24 inches (610 mm), a mound shall not be installed unless there is at least 24 inches (610 mm) of permeable, unsaturated soil with less than 50-percent coarse fragments located beneath this layer.
For one- and two-family dwellings and other buildings with estimated waste water flows less than 600 gallons (2271 L) per day, the mound dimensions shall be determined in accordance with this section or Tables 903.1(1) through 903.1(12). Dimensions and corresponding letter designations listed in the tables and referenced in this section are shown in Appendix A, Figures A-6 through A-10. For buildings with estimated waste water flows exceeding 600 gallons (2271 L) per day, the mound shall be designed in accordance with this section. Daily waste water flow shall be estimated as 150 gallons (568 L) per day per bedroom for one- and two-family dwellings. For other buildings the total daily waste water flow shall be determined in accordance with Table 802.7.2.

TABLE 903.1(1)
DESIGN CRITERIA FOR A MOUND FOR A ONE-BEDROOM HOME ON A 0- TO 6-PERCENT SLOPE
WITH LOADING RATES OF 150 GALLONS PER DAY FOR SLOWLY PERMEABLE SOIL

DESIGN PARAMETERSLOPE (percent)
0246
ATrench width, feet 3333
BTrench length, feet
Number of trenches
42
1
42
1
42
1
42
1
DMound height, inches 12121212
FMound height, inches 9999
GMound height, inches 12121212
HMound height, inches 18181818
IMound width, feeta15151515
JMound width, feeta11888
KMound length, feet 10101010
LMound length, feet 62626262
PDistribution pipe length, feet 20202020
Distribution pipe diameter, inches1111
Number of holes per distribution pipeb9999
Hole spacing, inchesb30303030
Hole diameter, inchesb0.250.250.250.25
W Mound width, feet 25262626
For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 gallon = 3.785 L.
a. Additional width to obtain required basal area.
b. Last hole is located at the end of the distribution pipe, which is 15 inches from the other hole.

TABLE 903.1 (2)
DESIGN CRITERIA FOR A TWO-BEDROOM HOME FOR A MOUND ON A 0- TO 6-PERCENT SLOPE
WITH LOADING RATES OF 300 GALLONS PER DAY FOR SLOWLY PERMEABLE SOIL

DESIGN PARAMETERSLOPE (percent)
0246
ATrench width, feet 3333
BTrench length, feet
Number of trenches
42
2
42
2
42
2
42
2
CTrench spacing, feet 15151515
DMound height, inches 12121212
EMound height, inches 12172525
FMound height, inches 9999
GMound height, inches 12121212
HMound height, inches 18181818
IMound width, feeta 12202020
JMound width, feet 12888
KMound length, feet 10101010
LMound length, feet 62626262
PDistribution pipe length, feet 20202020
Distribution pipe diameter, inches1111
Number of holes per distribution pipesb9999
Hole spacing, inchesb30303030
Hole diameter, inches0.250.250.250.25
RManifold length, feet
Manifold diameter, inchesc
15
2
15
2
15
2
15
2
WMound width, feet 42464646
For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 gallon = 3.785 L.
a. Additional width to obtain required basal area.
b. Last hole is located at the end of the distribution pipe, which is 15 inches from the other hole.
c. Diameter dependent on the size of pipe from pump and inlet position.

TABLE 903.1(3)
DESIGN CRITERIA FOR A THREE-BEDROOM HOME FOR A MOUND ON A 0- TO 6-PERCENT SLOPE
WITH LOADING RATES OF 450 GALLONS PER DAY FOR SLOWLY PERMEABLE SOIL

DESIGN PARAMETERSLOPE (percent)
0246
ATrench width, feet 3333
BTrench length, feet
Number of trenches
63
2
63
2
63
2
63
2
CTrench spacing, feet 15151515
DMound height, inches 12121212
EMound height, inches 12172025
FMound height, inches 9999
GMound height, inches 12121212
HMound height, inches 18181818
IMound width, feeta12202020
JMound width, feeta12888
KMound length, feet10101010
LMound length, feet62626262
PDistribution pipe length, feet
Distribution pipe diameter, inches
Number of holes per distribution pipeb
Hole spacingb, inches
Hole diameter, inches
31
11/4
13
30
0.25
31
11/4
13
30
0.25
31
11/4
13
30
0.25
31
11/4
13
30
0.25
RManifold length, feet
Manifold diameter, inchesc
15
2
15
2
15
2
15
2
WMound width, feet 42464646
For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 gallon = 3.785 L.
a. Additional width to obtain required basal area.
b. First hole is located 12 inches from the manifold.
c. Diameter dependent on the size of pipe from pump and inlet position.

TABLE 903.1(4)
DESIGN CRITERIA FOR A FOUR-BEDROOM HOME FOR A MOUND ON A 0- TO 6-PERCENT SLOPE WITH
LOADING RATES OF 600 GALLONS PER DAY FOR SLOWLY PERMEABLE SOIL

DESIGN PARAMETERSLOPE (percent)
0 246
ATrench width, feet 3 333
BTrench length, feet
Number of trenches
56
3
56
3
56
3
56
3
CTrench spacing, feet 15 151515
DMound height, inches 12 121212
EMound height, inches 12 202836
FMound height, inches 9 999
GMound height, inches 12 121212
HMound height, inches 24 242424
IMound width, feeta 12 202020
JMound width, feeta 12 888
KMound length, feet 12 121214
LMound length, feet 80 808084
PDistribution pipe length, feet
Distribution pipe diameter, inches
Number of holes per distribution pipeb
Hole spacing, inchesb
Hole diameter, inches
27.5
11/4
12
30
0.25
27.5
11/4
12
30
0.25
27.5
11/4
12
30
0.25
27.5
11/4
12
30
0.25
RManifold length, feet
Manifold diameter, inchesc
30
2
30
2
30
2
30
2
WMound width, feet 57 616161
For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 gallon = 3.785 L.
a. Additional width to obtain required basal area.
b. Last hole is located at the end of the distribution pipe, which is 15 inches from the previous hole.
c. Diameter dependent on the size of pipe from pump and inlet position.

TABLE 903.1(5)
DESIGN CRITERIA FOR A ONE-BEDROOM HOME FOR A MOUND ON A 0- TO 12-PERCENT SLOPE WITH
LOADING RATES OF 150 GALLONS PER DAY FOR SHALLOW PERMEABLE SOIL OVER CREVICED BEDROCK

DESIGN PARAMETERPERCOLATION RATE (minutes per inch)
SLOPE (percent)
3 to 603 to less than 30
0246810a12a
ABed width, feetb10101010101010
BBed length, feet 13131313131313
DMound height, inches 24242424242424
EMound height, inches 24262931343638
FMound height, inches 9999999
GMound height, inches 12121212121212
HMound height, inches 18181818181818
IMound width, feet 12131417182126
JMound width, feet 12111010999
KMound length, feet 12121213131315
LMound length, feet 37373739393943

(continued)

TABLE 903.1(5)—continued
DESIGN CRITERIA FOR A ONE-BEDROOM HOME FOR A MOUND ON A 0- TO 12-PERCENT SLOPE WITH
LOADING RATES OF 150 GALLONS PER DAY FOR SHALLOW PERMEABLE SOIL OVER CREVICED BEDROCK

PERCOLATION RATE (minutes per inch)
SLOPE (percent)
DESIGN PARAMETER3 to 603 to less than 30
0246810a12a
PDistribution pipe length, feetc
Distribution pipe diameter, inches
Number of distribution pipes
12.5
1
6
12.5
1
6
12.5
1
6
12.5
1
6
12.5
1
6
12.5
1
6
12.5
1
6
RManifold length, feet
Manifold diameter, inchesc
6
2
6
2
6
2
6
2
6
2
6
2
6
2
SDistribution pipe spacing, feet3333333
Number of holes per distribution piped6666666
Hole spacing, inchesd30303030303030
Hole diameter, inches 0.250.250.250.250.250.250.25
WMound width, feet 34343437374145
For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 gallon = 3.785 L, 1 minute per inch = 2.4 s/mm.
a. On sites with a 10- to 12-percent slope, the fill depth (D) shall be reduced to a minimum of 1.5 feet or the bed width shall be reduced to decrease E [downslope fill depth, feet (mm)].
b. Bed widths shall not be limited.
c. Use a manifold with distribution pipes on only one side.
d. Last hole is located at the end of the distribution pipe, which is 15 inches from the previous hole.

TABLE 903.1(6)
DESIGN CRITERIA FOR A TWO-BEDROOM HOME FOR A MOUND ON A 0- TO 12-PERCENT SLOPE WITH
LOADING RATES OF 300 GALLONS PER DAY FOR SHALLOW PERMEABLE SOIL OVER CREVICED BEDROCK

DESIGN PARAMETER PERCOLATION RATE (minutes per inch)
SLOPE (percent)
3 to 60 3 to less than 30
0 2 4 6 8 10a 12a
A Bed width, feetb 10 10 10 10 10 1010
B Bed length, feet 25 25 25 25 25 2525
D Mound height, inches 24 24 24 24 24 2424
E Mound height, inches 24 26 29 31 34 3638
F Mound height, inches 9 9 9 9 9 99
G Mound height, inches 12 12 12 12 12 1212
H Mound height, inches 18 18 18 18 18 1818
I Mound width, feet 12 13 14 17 18 2126
J Mound width, feet 12 11 10 10 9 99
K Mound length, feet 12 12 12 13 13 1315
L Mound length, feet 49 49 4951 51 5155
P Distribution pipe length, feetc
Distribution pipe diameter, inches
Number of distribution pipes
12
1
6
12
1
6
12
1
6
12
1
6
12
1
6
12
1
6
12
1
6
R Manifold length, feet
Manifold diameter, inches
6
2
6
2
6
2
6
2
6
2
6
2
6
2
S Distribution pipe spacing, feet
Number of holes per distribution piped
Hole spacing, inchesd
Hole diameter, inches
3
5
30
0.25
3
5
30
0.25
3
5
30
0.25
3
5
30
0.25
3
5
30
0.25
3
5
30
0.25
3
5
30
0.25
W Mound width, feet 34 34 3437 37 4145
For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 gallon = 3.785 L, 1 minute per inch = 2.4 s/mm.
a. On sites with a 10- to 12-percent slope, the fill depth (D) shall be reduced to a minimum of 1.5 feet or the bed width shall be reduced to decrease E [downslope fill depth, feet (mm)].
b. Bed widths shall not be limited.
c. This design is based on a manifold with distribution pipes on both sides. An alternative design basis is 24-foot distribution pipes, with manifold at the end.
d. Last hole is located 9 inches from the end of the distribution pipe.

TABLE 903.1(7)
DESIGN CRITERIA FOR A THREE-BEDROOM HOME FOR A MOUND ON A 0- TO 12-PERCENT SLOPE
WITH LOADING RATES OF 450 GALLONS PER DAY FOR SHALLOW PERMEABLE SOIL OVER CREVICED BEDROCK

DESIGN PARAMETERPERCOLATION RATE (minutes per inch)
SLOPE (percent)
3 to 603 to less than 30
0246810a12a
ABed width, feetb10101010101010
BBed length, feet 38383838383838
DMound height, inches 24242424242424
EMound height, inches 24262931343638
FMound height, inches 9999999
GMound height, inches 12121212121212
HMound height, inches 18181818181818
IMound width, feet 12131417182126
JMound width, feet 12111010999
KMound length, feet 12121213131315
LMound length, feet 62626264646468
PDistribution pipe length, feetc
Distribution pipe diameter, inches
Number of distribution pipes
18.5
1
6
18.5
1
6
18.5
1
6
18.5
1
6
18.5
1
6
18.5
1
6
18.5
1
6
RManifold length, feet
Manifold diameter, inches
6
2
6
2
6
2
6
2
6
2
6
2
6
2
SDistribution pipe spacing, feet
Number of holes per distribution piped
Hole spacing, inchesd
Hole diameter, inches
3
8
30
0.25
3
8
30
0.25
3
8
30
0.25
3
8
30
0.25
3
8
30
0.25
3
8
30
0.25
3
8
30
0.25
WMound width, feet 34343437374145
For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 gallon = 3.785 L, 1 minute per inch = 2.4 s/mm.
a. On sites with a 10- to 12-percent slope, the fill depth (D) shall be reduced to a minimum of 1.5 feet or the bed width shall be reduced to decrease E [downslope fill depth, feet (mm)].
b. Bed widths shall not be limited.
c. Use a manifold with distribution pipes on only one side.
d. Last hole is located at the end of the distribution pipe, which is 27 inches from the previous hole.

TABLE 903.1(8)
DESIGN CRITERIA FOR A FOUR-BEDROOM HOME FOR A MOUND ON A 0- TO 12-PERCENT SLOPE WITH
LOADING RATES OF 600 GALLONS PER DAY FOR SHALLOW PERMEABLE SOIL OVER CREVICED BEDROCK

DESIGN PARAMETERPERCOLATION RATE (minutes per inch)
SLOPE (percent)
3 to 603 to less than 30
0246810a12a
ABed width, feetb10101010101010
BBed length, feet 50505050505050
DMound height, inches 24242424242424
EMound height, inches 24262931343638
FMound height, inches 9999999
GMound height, inches 12121212121212
HMound height, inches 18181818181818
IMound width, feet 12131417182126
JMound width, feet 12111010999
KMound length, feet 12121213131315
LMound length, feet 74747476767678
PDistribution pipe length, feetc
Distribution pipe diameter, inches
Number of distribution pipes
24.5
1
6
24.5
1
6
24.5
1
6
24.5
1
6
24.5
1
6
24.5
1
6
24.5
1
6
RManifold length, feet
Manifold diameter, inches
6
2
6
2
6
2
6
2
6
2
6
2
6
2
SDistribution pipe spacing, feet
Number of holes per distribution piped
Hole spacing, inchesd
Hole diameter, inches
3
10
30
0.25
3
10
30
0.25
3
10
30
0.25
3
10
30
0.25
3
10
30
0.25
3
10
30
0.25
3
10
30
0.25
WMound width, feet 34343437374145
For SI: 1 inch 25.4 mm, 1 foot = 304.8 mm, 1 gallon = 3.785 L, 1 minute per inch = 2.4 s/mm.
a. On sites with a 10- to 12-percent slope, the fill depth (D) shall be reduced to a minimum of 1.5 feet or the bed width shall be reduced to decrease E [downslope fill depth, feet (mm)].
b. Bed widths shall not be limited.
c. Use a manifold with distribution pipes on only one side.
d. Last hole is located 9 inches from the end of the distribution pipe.

TABLE 903.1(9)
DESIGN CRITERIA FOR A ONE-BEDROOM HOME FOR A MOUND ON A 0- TO 12-PERCENT SLOPE WITH LOADING RATES OF 150 GALLONS PER DAY FOR PERMEABLE SOIL WITH A HIGH WATER TABLE

DESIGN PARAMETERPERCOLATION RATE (minutes per inch)
SLOPE (percent)
0 to 600 to less than 30
024681012
ABed width, feet 4444444
BBed length, feet 32323232323232
DMound height, inches 12121212121212
EMound height, inches 12131414161718
FMound height, inches 9999999
GMound height, inches 12121212121212
HMound height, inches 18181818181818
IMound width, feet 9101112131415
JMound width, feet 9988776

(continued)

TABLE 903.1(9)—continued
DESIGN CRITERIA FOR A ONE-BEDROOM HOME FOR A MOUND ON A 0- TO 12-PERCENT SLOPE WITH
LOADING RATES OF 150 GALLONS PER DAY FOR PERMEABLE SOIL WITH A HIGH WATER TABLE

DESIGN PARAMETERPERCOLATION RATE (minutes per inch)
SLOPE (percent)
0 to 600 to less than 30
024681012
KMound length, feet 10101010101111
LMound length, feet 52525252525353
PDistribution pipe length 15.515.515.515.515.515.515.5
Distribution pipe diameter, inches1111111
Number of distribution pipes2222222
Number of holes per distribution pipea7777777
Hole spacing, inchesa30303030303030
Hole diameter, inches0.250.250.250.250.250.250.25
WMound width, feet 22232324242525
For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 gallon = 3.785 L, 1 minute per inch = 2.4 s/mm.
a. Last hole is located at the end of the distribution pipe, which is 21 inches from the previous hole.

TABLE 903.1(10)
DESIGN CRITERIA FOR A TWO-BEDROOM HOME FOR A MOUND ON A 0- TO 12-PERCENT SLOPE WITH
LOADING RATES OF 300 GALLONS PER DAY FOR PERMEABLE SOIL WITH A HIGH WATER TABLE

DESIGN PARAMETERPERCOLATION RATE (minutes per inch)
SLOPE (percent)
0 to 600 to less than 30
024681012
ABed width, feet 6666666
BBed length, feet 42424242424242
DMound height, inches 12121212121212
EMound height, inches 12131417181922
FMound height, inches 9999999
GMound height, inches 12121212121212
HMound height, inches 18181818181818
IMound width, feet 9101112131516
JMound width, feet 9988776
KMound length, feet 10101010101111
LMound length, feet 62626262626464
PDistribution pipe length, feeta
Distribution pipe diameter, inches
Number of distribution pipes
20
1
4
20
1
4
20
1
4
20
1
4
20
1
4
20
1
4
20
1
4
RManifold length, feet
Manifold diameter, inches
3
2
3
2
3
2
3
2
3
2
3
2
3
2
SDistribution pipe spacing, feet
Number of holes per distribution pipeb
Hole spacing, inchesb
Hole diameter, inches
3
9
30
0.25
3
9
30
0.25
3
9
30
0.25
3
9
30
0.25
3
9
30
0.25
3
9
30
0.25
3
9
30
0.25
WMound width, feet 24252526262829
For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 gallon = 3.785 L, 1 minute per inch = 2.4 s/mm.
a. Use a manifold with distribution pipes only on one side.
b. Last hole is located at the end of the distribution pipe, which is 15 inches from the previous hole.

TABLE 903.1(11)
DESIGN CRITERIA FOR A THREE-BEDROOM HOME FOR A MOUND ON A 0- TO 12-PERCENT SLOPE WITH
LOADING RATES OF 450 GALLONS PER DAY FOR PERMEABLE SOIL WITH A HIGH WATER TABLE

DESIGN PARAMETERPERCOLATION RATE (minutes per inch)
SLOPE (percent)
0 to 600 to less than 30
024681012
ABed width, feet 8888888
BBed length, feet 47474747474747
DMound height, inches 12121212121212
EMound height, inches 12121618192224
FMound height, inches 9999999
GMound height, inches 12121212121212
HMound height, inches 18181818181818
IMound width, feet 9111213151718
JMound width, feet 9988776
KMound length, feet 10101010101112
LMound length, feet 67676767696971
PDistribution pipe length, feet
Distribution pipe diameter, inches
Number of distribution pipes
23
1
6
23
1
6
23
1
6
23
1
6
23
1
6
23
1
6
23
1
6
RManifold length, feet
Manifold diameter, inches
64
2
64
2
64
2
64
2
64
2
64
2
64
2
SDistribution pipe spacing, feet
Number of holes per distribution pipea
Hole spacing, inchesa
Hole diameter, inches
32
10
30
0.25
32
10
30
0.25
32
10
30
0.25
32
10
30
0.25
32
10
30
0.25
32
10
30
0.25
32
10
30
0.25
WMound width, feet 26282829303232
For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 gallon = 3.785 L, 1 minute per inch = 2.4 s/mm.
a. Last hole is located at the end of the distribution pipe, which is 21 inches from the previous hole.

TABLE 903.1(12)
DESIGN CRITERIA FOR A FOUR-BEDROOM HOME FOR A MOUND ON A 0- TO 12-PERCENT SLOPE WITH
LOADING RATES OF 600 GALLONS PER DAY FOR PERMEABLE SOIL WITH A HIGH WATER TABLE

DESIGN PARAMETERPERCOLATION RATE (minutes per inch)
SLOPE (percent)
0 to 600 to less than 30
024681012
ABed width, feet 10101010101010
BBed length, feet 50505050505050
DMound height, inches 12121212121212
EMound height, inches 12141719222426
FMound height, inches 9999999
GMound height, inches 12121212121212
HMound height, inches 18181818181818
IMound width, feet 9111314171819
JMound width, feet 9988776
KMound length, feet 10101010111112
LMound length, feet 70707070727274

(continued)

TABLE 903.1(12)—continued
DESIGN CRITERIA FOR A FOUR-BEDROOM HOME FOR A MOUND ON A 0- TO 12-PERCENT SLOPE WITH
LOADING RATES OF 600 GALLONS PER DAY FOR PERMEABLE SOIL WITH A HIGH WATER TABLE

DESIGN PARAMETERPERCOLATION RATE (minutes per inch)
SLOPE (percent)
0 to 600 to less than 30
024681012
PDistribution pipe length, feet
Distribution pipe diameter, inches
Number of distribution pipes
24.5
1
6
24.5
1
6
24.5
1
6
24.5
1
6
24.5
1
6
24.5
1
6
24.5
1
6
RManifold length, feet
Manifold diameter, inches
6
2
6
2
6
2
6
2
6
2
6
2
6
2
SDistribution pipe spacing, feet
Number of holes per distribution pipea
Hole spacing, inchesa
Hole diameter, inches
3
10
30
0.25
3
10
30
0.25
3
10
30
0.25
3
10
30
0.25
3
10
30
0.25
3
10
30
0.25
3
10
30
0.25
WMound width, feet 28293132343536
For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 gallon = 3.785 L, 1 minute per inch = 2.4 s/mm.
a. Last hole is 9 inches from the end of the distribution pipe.
The following symbols and notations shall apply to the provisions of this section.
A=Bed or trench width, feet (mm).
AA=Required absorption area, square feet (m2).
B=Bed or trench length, feet (mm).
BA=Basal area, square feet (m2).
C=Trench spacing, feet (mm).
CI=Infiltration capacity of natural soil, gallons per foot
per day (L/mm/day).
D=Fill depth, feet (mm).
E=Downslope fill depth, feet (mm).
F=Bed or trench depth, feet (mm).
G=Minimum cap and topsoil depth, feet (mm).
H=Cap and topsoil depth at center of mound, foot
(mm).
I=Downslope width, feet (mm).
J=Upslope width, feet (mm).
K=End slope length, feet (mm).
L=Total mound length, feet (mm).
N=Number of trenches.
P=Distribution pipe length, feet (mm).
R=Manifold length, feet (mm).
S=Distribution pipe spacing, feet (mm).
SD=Downslope correction factor.
SU=Upslope correction factor.
TW=Total daily waste-water flow, gallons per day
(L/day).
W=Total mound width, feet (mm).
X=Slope, percent.
The absorption area shall be sized based on the daily waste-water flow and the infiltrative capacity of the medium sand texture fill material, equaling 1.2 gallons per square foot (0.03 L/m2) per day. The required absorption area shall be determined by the following equation:
(Equation 9-1)
For SI: 1 square foot = 0.0929 m2, 1 gallon = 3.785 L.
Effluent shall be distributed in the mound through a trench system for slowly permeable soils with or without high ground water. Trench length shall be selected by determining the longest dimension perpendicular to any slope on the site. Trench width and spacing is dependent on specific site conditions. Trenches shall be 2 feet to 4 feet (610 mm to 1219 mm) wide. Trench length (B) shall be not more than 100 feet (2540 mm). Trenches shall be of equal length where more than one trench is required. A mound shall not have more than three trenches. Trench spacing (C) shall be determined by the following equation:
(Equation 9-2)
For SI: 1 gallon = 3.785 L, 1 square foot = 0.0929 m2.

The calculated trench spacing (C) shall be measured from center to center of the trenches. Facilities with more than 1,500 gallons (56 775 L) per day shall be specifically engineered and approved for use with a trench system.

A long, narrow bed design shall be used for permeable soils with high water tables. The bed shall be square or rectangular for shallow permeable soils over bedrock. The bed length (B) shall be set after determining the longest dimension available and perpendicular to any slope on the site.
The mound height consists of the fill depth, bed or trench depth, the cap and topsoil depth.
The fill depth (D) shall be not less than 1 foot (305 mm) for slowly permeable soils and permeable soils with high water tables and not less than 2 feet (610 mm) of fill shall be required for shallow permeable soils over bedrock. Additional fill shall be placed at the downslope end of the bed or trench where the site is not level so the bottom of the bed or trenches is level. The downslope fill depth for bed systems shall be determined by the following equation:
E = D + XA(Equation 9-3)

For SI: 1 foot = 304.8 mm.

The downslope fill depth for trench systems shall be determined by the following equation:

E = D + X (C + A)(Equation 9-4)

For SI: 1 foot = 304.8 mm.

The bed or trench depth (F) shall be not less than 9 inches (229 mm) and not less than 6 inches (152 mm) of aggregate shall be placed under the distribution pipes and not less than 2 inches (51 mm) of aggregate shall be placed over the top of the distribution pipes.
The cap and topsoil depth (H) at the center of the mound shall be not less than 18 inches (457 mm), which includes 1 foot (305 mm) of subsoil and 6 inches (152 mm) of topsoil. Outer edges of the mound, G (the minimum cap and topsoil depth), shall be not less than 1 foot (305 mm), which includes 6 inches (152 mm) of subsoil and 6 inches (152 mm) of topsoil. The soil used for the cap shall be topsoil or finer textured subsoil.
The total mound length (L) shall be determined by the following equation:
L = B + 2K(Equation 9-5)

For SI: 1 foot = 304.8 mm.

where:

The mound width for a bed system shall be determined by the following equation:
W = J + A + I(Equation 9-6)

For SI: 1 foot = 304.8 mm.

The mound width for a trench system shall be determined by the following equation:
(Equation 9-7)

For SI: 1 foot = 304.8 mm.

where:

J = 3(D + F + G)SU

I = 3(E + F + G)SD

The upslope correction factor (SU) and the downslope correction factor (SD) shall be determined based on the slope in accordance with Table 903.5.5.

TABLE 903.5.5
DOWNSLOPE AND UPSLOPE WIDTH CORRECTIONS
FOR MOUNDS ON SLOPING SITES

SLOPE
(percent)
DOWNSLOPE CORRECTION
FACTOR (SD)
UPSLOPE CORRECTION
FACTOR (SU)
011
11.030.97
21.060.94
31.100.915
41.140.89
51.180.875
61.220.86
71.270.83
81.320.80
91.380.785
101.440.77
111.510.75
121.570.73
The minimum basal area required shall be determined by the following equation:
(Equation 9-8)

For SI: 1 square foot = 0.0929 m2.

The infiltrative capacity of natural soil shall be determined on the percolation rate in accordance with Table 903.6.

TABLE 903.6
INFILTRATIVE CAPACITY OF NATURAL SOIL

PERCOLATION RATE
(minutes per inch)
INFILTRATIVE CAPACITY
(gallons per foot per day)
Less than 301.2
30 to 600.74
More than 60 to 1200.24
For SI: 1 gallon per foot per day = 0.012 L/mm/day,
1 minute per inch = 2.4 s/mm.
The available basal area for a bed system shall be determined by one of the following equations:
BA = B( A + I) for sloping sites (Equation 9-9)
BA = BW for level sites(Equation 9-10)
For SI: 1 square foot = 0.0929 m2.
The available basal area for a trench system shall be determined by one of the following equations:
for sloping sites(Equation 9-11)
for level sites (Equation 9-12)
For SI: 1 square foot = 0.0929 m2.
The downslope width (I) on a sloping site shall be increased or the upslope width (J) and downslope (I) widths on a level site shall be increased until sufficient area is available if the basal area available is not equal to or greater than the basal area required.
The dose volume and pump shall conform to the requirements of Chapters 7 and 8.
Construction shall not commence where the soil is so wet a soil wire forms when the soil is rolled between the hands. Installation of mound systems where the soil on the site is frozen shall be prohibited for new construction.
Excess vegetation shall be cut and removed from the mound area. Small trees shall be cut to grade surface, leaving the stumps in place.
The force main from the pumping chamber shall be installed before the mound site is plowed. The force main shall be sloped uniformly toward the pumping chamber so the force main drains after each dose.
The site shall be plowed with a moldboard plow or chisel plow. The site shall be plowed to a depth of 7 inches to 8 inches (178 mm to 203 mm) with the plowing perpendicular to the slope. Rototillers shall not be used. The sand fill shall be placed immediately after plowing. All foot and vehicular traffic shall be kept off the plowed area.
The fill material shall be medium sand texture defined as 25 percent or more very coarse, coarse and medium sand and a maximum of 50 percent fine sand, very fine sand, silt and clay. The percentage of silt plus one and one-half times the percentage of clay shall not exceed 15 percent. Fill materials with higher content of silt and clay shall not be used.
The medium sand fill shall be moved into place from the upslope and side edges of the plowed area. Vehicular traffic shall be prohibited in the area extending to 25 feet (7620 mm) beyond the downslope edge of the mound. The sand fill shall be moved into place with a track-type tractor and not less than 6 inches (152 mm) of sand shall be kept beneath the tracks at all times.
The bed or trenches shall be formed within the sand fill. The bottom of the trenches or bed shall be level. The elevation of the bottom of the trenches or bed shall be checked at the upslope and downslope edges to ensure that the fill has been placed to the proper depth.
A minimum of 6 inches (152 mm) of coarse aggregate ranging in size from 1/2 inch to 21/2 inches (12.7 mm to 64 mm) shall be placed in the bed or trench excavation. The top of the aggregate shall be level.
Distribution systems shall be placed on the aggregate, with the holes located on the bottom of the distribution pipe. The ends of all distribution pipes shall be marked at the surface, and an observation pipe shall be placed to the bottom of the bed or each trench.
The top of the bed or trenches shall be covered with not less than 2 inches (51 mm) of aggregate ranging in size from 1/2 inch to 21/2 inches (12.7 mm to 64 mm) and not less than 4 inches to 5 inches (102 mm to 127 mm) of uncompacted straw or marsh hay or approved synthetic fabric shall be placed over the aggregate. Cap and topsoil covers shall be in place and the mound shall be seeded immediately and protected from erosion.
When the septic tank is pumped, the pump chamber shall be inspected and pumped to remove any solids present. Excess traffic in the mound area shall be avoided.
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