NEBRASKA ADMINISTRATIVE CODE
NEBRASKA DEPARTMENT OF ENVIRONMENTAL QUALITY

Title 124 - Rules And Regulations For The Design, Operation And Maintenance of Onsite Wastewater Treatment Systems
Chapter 11 - Mound Systems

001 A mound system that receives only domestic wastewater and either serves a dwelling that contains no more than five bedrooms or a non-dwelling that generates no more than 600 gallons per day provided such system does not endanger human health or cause pollution and meets all the provisions for design, setback distances and reserve area prescribed in these regulations may be designed by a Master Installer with a Mound System Endorsement, a Professional Engineer, or a Registered Environmental Health Specialist without the need for a permit from the Department provided the requirements of this chapter are met in addition to all other site location, setback, and other design requirements in this Title unless specifically identified otherwise. The following requirements are specific to mound systems designed, constructed, and operated under provisions in this Title for the mound system endorsement.

002 Site Requirements

002.01 A minimum of one foot of vertical separation of native undisturbed soil is required between the bottom of the sand fill of the mound for a mound system and the top of the seasonal high groundwater level, bedrock, or other limiting soil feature.

002.02 The minimum vertical separation from the treatment media distribution bed to the top of the seasonal high groundwater, bedrock, or other limiting soil feature is four feet.

002.03 The percolation rate of the native undisturbed soil beneath the sand fill shall not be slower than 60 minutes per inch.

002.04 The percolation rate of the native undisturbed soil shall be measured in the top 12 inches of the soil.

002.05 An endorsed mound system shall not be installed on ground with a slope over five percent.

002.06 The location restrictions and horizontal setback requirements for soil absorption systems from Table 5.1 in Chapter 5 apply and shall be measured from the toe of the mound.

002.07 A mound shall not be constructed in a location or manner that causes water to pond on the surface or that blocks and retains runoff from precipitation.

003 Design and Construction of Endorsed Mound Soil Absorption System

003.01 Site Preparation

003.01A Vegetation over two inches tall and loose organic matter shall be removed prior to placing the sand layer. Trees and brush shall be cut flush with the ground surface and the roots left in place.

003.01B The supply pipe from the pump to the effluent distribution system shall be installed prior to preparation of the soil surface with minimal native soil disruption. The pipe trench shall be backfilled using the excavated native soil and compacted level to avoid future settlement.

003.01C The native undisturbed soil under the entire mound area shall be roughened to a depth of six to eight inches using backhoe teeth or chisel plow to improve the surface contact between the native soil and sand fill of the mound. The roughening shall be performed with a four to six inch layer of sand in place and only when the moisture content of the soil is below its plastic limit. The native soil shall not be pulverized or compacted. Rototilling is not permitted. Disking is permitted only if the native soil is sand or loamy sand. The roughening shall be performed along the contour or perpendicular to the slope.

003.02 Sand Layer

003.02A A layer of clean sand shall be installed over the original ground surface to a thickness that provides at least 48 inches of vertical separation between the elevation of the bottom of the treatment media distribution bed as described below and seasonal high groundwater, bedrock, or any other barrier layer. The sand layer must also be at least 12 inches thick below the uphill edge of the Treatment Media Distribution Bed.

003.02B The sand for the sand layer shall be clean, natural silica free of fines and debris, meeting the gradation shown in Table 11.1.

Table 11.1 - Sand Specification for Endorsed Mound Sand Layer

Sieve Size
Percent Passing
3/8 inch
100
No. 4
95 to 100
No. 8
80 to 100
No. 16
45 to 85
No. 30
15 to 60
No. 50
3 to 15
No. 100
0 to 4
No. 200
0 to 2
003.02C The first six inches of the sand layer shall be placed immediately prior to roughening the native undisturbed soil surface. The first sand layer shall be placed without driving vehicles of any kind on the area of the soil surface to be roughened. The remaining sand shall be placed using techniques that minimize compaction and if vehicle traffic is necessary only track-type equipment shall be used in placing and leveling the remaining sand with at least six inches of sand must be kept underneath equipment.

003.02D The top of the sand layer under the treatment media distribution bed shall be level in all directions.

003.02E The sand layer shall extend up on all sides of the treatment media layer to the same elevation as the top of the media.

003.02F The side slopes of the sand layer shall not be steeper than three horizontal units to one vertical unit.

003.02G The sand layer shall be constructed to the dimensions shown in Tables 11.3 through 11.5. Dimensions shall be based on the depth to groundwater or impermeable layer, the percolation rate, the ground slope, and the number of bedrooms for dwellings or the maximum daily wastewater flow for non-dwellings.

003.02H The length direction of the sand layer shall be oriented parallel to ground surface contour lines. On ground slopes greater than one percent, the length of the sand layer shall be curved to match the site contour lines.

003.03 Treatment Media Distribution Bed

003.03A A treatment media distribution bed at least 12 inches thick shall be constructed on top of the sand layer. The media serves a number of purposes including but not limited to providing a biological treatment media, holding the effluent distribution piping in place, and helping to distribute the partially treated effluent flow over the sand layer.
003.03B For rock used as the treatment media the rock shall be ¾-inch minimum to 2 ½-inch maximum dimension, clean, durable, non-calcareous, and meeting the gradation specified in Table 11.2. Alternately, cylindrical bundles of expanded polystyrene synthetic aggregate contained in high-strength polyethylene netting may be used.

Table 11.2 - Rock Specification for Endorsed Mound Media Distribution Bed

Sieve Size
Percent Passing
2 ½
95 - 100
¾
0 – 5
No. 200
0 – 1

003.03C The width of the treatment media distribution bed shall be 10 feet.

003.03D The length of the treatment media distribution bed shall be as given in Tables 11.3 through 11.5. When the sand layer is curved to match site contour lines, the media layer shall be curved to match the curvature of the sand layer.

003.03E There shall be at least eight inches of media below and two inches above the effluent distribution piping. The media shall encase the distribution piping. The effluent distribution piping shall be level. For rock, the bottom nine inches of the media layer shall be placed on top of the sand layer then the effluent distribution piping shall be placed on top of the rock, and the remaining three inches of rock placed over the entire rock bed media area, encasing the distribution piping.

003.03F A minimum four-inch diameter PVC inspection pipe with removable cap shall be installed from the bottom of the media bed extending to six inches above the mound surface. The bottom six inches of the inspection pipe shall have two rows of holes three-eighth inch in diameter spaced nominally three inches apart around the circumference of the pipe.

003.04 Effluent Distribution Piping

003.04A Pressure distribution shall be used to distribute effluent evenly throughout the treatment media bed. Distribution shall be by a piping system consisting of a force main pipe, manifold pipe, and lateral distribution pipes.

003.04B All pipe used for pressure distribution shall be at least Schedule 40 or stronger PVC pipe with a suitable pressure rating for the intended use.

003.04C Force Main

003.04C.1 The nominal force main pipe inside diameter shall be 2 inches.

003.04C.2 If the distribution laterals in the mound are lower than the low water level in the pump tank, a sewage vacuum breaker valve shall be installed at the high point of the force main or a three-sixteenth inch weep hole shall be adequately placed in the bottom of the force main inside the pump tank to prevent siphoning of the pump tank contents to the mound.

003.04C.3 The force main shall be installed at a continuous slope to allow the pipe to drain completely between pump cycles to prevent freezing. There shall be no sags or low spots that collect water. The force main shall be buried between the pump tank and the mound at a depth sufficient to protect the pipe from damage.

003.04D Manifold Pipe

003.04D.1 The nominal manifold pipe inside diameter shall be two inches.

003.04D.2 The manifold pipe shall run perpendicular to the long direction of the treatment media distribution bed.

003.04D.3 The manifold pipe shall be located at either end of the rock bed, or shall be at the midpoint of the length of the mound, with equal-length lateral distribution pipes running each side from the center-located manifold.

003.04E Lateral Distribution Pipes

003.04E.1 The 10-foot wide treatment media distribution bed shall have three lateral distribution pipes running lengthwise, spaced 40 inches apart and 20 inches from the sides of the media bed.

003.04E.2 The nominal inside diameter of the lateral distribution pipes shall be 1.5 inches.

003.04E.3 Each lateral pipe shall have three-sixteenth inch diameter orifice holes drilled at 24 inch centers in a straight line along the bottom of the pipe. When a center-located manifold is used, the first orifice on each lateral shall be 12 inches from the center of the manifold so that the 24 inch center-to-center spacing is maintained. All orifice holes shall be precision drilled using a drill press, and the pipe shall be deburred inside and outside.

003.04E.4 Orifice shields shall be affixed over each orifice to protect the orifice from blockage from contact with the treatment media, except that orifice shields are not required when the lateral distribution pipes are placed in perforated pipe, the perforated pipe shall not exceed four inches nominal diameter, and there shall be at least eight inches of treatment media below and two inches above the perforated pipe. Orifice shields shall be designed with drain holes or slots to allow complete drainage to prevent freezing and shall be removable to allow for orifice cleaning.

003.04E.5 The number of orifices per lateral shall be as shown in Table 11.6.

003.04E.6 The downstream end of each lateral shall be equipped with a sweep elbow turning up and terminating a minimum of six inches above the surface. Each sweep elbow shall be equipped with either a shut-off valve readily accessible from the surface through a valve box or a screw-on cap, to allow flushing of the laterals.

003.05 Soil Cover

003.05A A layer of non-woven geotextile fabric shall be placed over the top and sides of the treatment media distribution layer. The fabric shall be of adequate thickness to resist tearing. The fabric shall allow passage of water and shall prevent migration of soil particles into the media layer.

003.05B A cover layer of loam or sandy loam soil shall be placed over the media and fabric layers as well as the sand side slopes. Clay soil is not acceptable. This cover layer shall be at least six inches thick over the side slopes and at the edges of the media bed, and shall be crowned to provide at least 12 inches of cover soil over the middle of the media bed to promote surface drainage.

003.05C A layer of topsoil at least six inches thick, suitable for sustaining a healthy growth of perennial grass, shall be placed over the entire mound area. After placement of the topsoil layer, the final minimum thickness of the loam and topsoil layers over the sand layer and media bed shall be 12 inches and crowned to a minimum of 18 inches over the middle of the media bed.

003.05D Following construction of the mound, a shallow rooted perennial grass shall be established and maintained on the entire surface of the mound and the ground surface upslope from the mound shall be graded to drain precipitation around the ends of the mound. Brush, trees, or garden plants (including flowers or vegetable plants) shall not be grown on the mound.

004 Primary Treatment (Septic Tank)

004.01 All wastewater discharged to a mound system shall have undergone treatment in a septic tank that is designed, installed, and maintained in accordance with all requirements of this Title.

004.02 The effluent from the septic tank shall pass through a filter with one-sixteenth inch maximum openings before entering the pump to the effluent distribution piping. If more than one septic tank is used then the tanks shall be placed in series and the filter shall be placed in the outlet of the last tank.

005 Effluent Pumping System

005.01 Each mound system shall have an effluent pumping system to transport septic tank effluent to the effluent distribution piping in pressurized doses. The pumping system shall include a pump tank, effluent pump, discharge piping, level controls, and alarm system.

005.02 Pump Tank

005.02A The minimum pump tank capacity shall be as shown in Table 11.7.

005.02B The pump tank shall meet all the requirements for materials, construction, access, and installation as for septic tanks in accordance with this Title.

005.02C The pump tank shall be watertight and access to the pump tank shall extend to the ground surface with a secured lid.

005.03 Dose Pump

005.03A The pump shall be for submersible operation, designed for pumping wastewater or septic tank effluent. The pump shall be capable of passing a one-sixteenth inch particle, or shall be equipped with an adequate screening device to prevent clogging.

005.03B The pump shall be securely supported within the pump tank to resist movement from starting torque and dynamic hydraulic forces in the discharge piping. The pump inlet shall be located at a distance from the tank floor and walls as recommended by the pump manufacturer.

005.03C The pump shall be removable without requiring human entry into the pump tank or other confined space.

005.03D The pump shall be designed to produce the minimum flow rate and minimum discharge pressure listed in Table 11.7.

005.03E A pump with an internal check valve shall not be used, unless the check valve is removed or a one-quarter inch weep hole is drilled in the bottom of the discharge pipe to allow the force main to drain back to the pump tank between pump cycles. The discharge pipe must drain completely between cycles.

005.04 Discharge Piping

005.04A The discharge piping shall include a union or quick-disconnect fitting that allows the pump to be disconnected from the discharge pipe and removed from the pump tank without human entry into the tank.

005.04B The discharge piping shall be Schedule 40 or stronger PVC pipe, shall be no smaller than the pump discharge fitting size, and shall provide a smooth transition to the two-inch diameter force main.

005.05 Pump and Level Controls and Alarms

005.05A The pump tank shall be equipped with a level control system to start the pump at a preset high water level, stop the pump and a preset low water level, and activate an alarm at a preset high water alarm level.

005.05B The level control and alarm switches shall be of the sealed, weighted float or diaphragm type. The cords shall be secured to prevent tangling. The level control switches shall be located where they are visible from the ground surface and accessible for cleaning and adjustment without human entry into the pump tank or other confined space.

005.05C The pump-stop control switch shall be set to stop the pump at or above the minimum pump submergence level recommended by the pump manufacturer.

005.05D The pump-start control switch shall be set to start the pump at a height above the pump-stop level to provide the required dose volume (see Table 11.7) based on the dimensions of the pump tank plus the volume of the force main pipe if the force main drains back to the pump tank. The volume for the two inch diameter pipe should be taken as 0.15 gallons per linear foot of pipe.

005.05E The high-level alarm switch shall be set approximately three inches above the pump-start level.

005.05F The dose volume shall be as shown in Table 11.7.

005.05G The pump control panel shall include externally mounted visible and audible alarms. The alarms shall be mounted in a location readily visible to the owner. If the control panel is mounted outdoors, the enclosure shall be for weather tight duty.

005.05H The pump electrical power shall be supplied on a separate electrical circuit from that of the alarm system.

005.05I The alarm system shall be comprised of both audible and visible alarm indicators.

005.05J Electrical control panel(s) shall be located outside the pump tank, must be protected from the weather and must provide no air path between the panel and the pump tank. Electrical connections inside the tank shall be made using moisture and gas resistant connectors suitable for the wastewater environment.

Table 11.3 - Mound Dimensions for Ground Slope of 0% to 1%

Depth to Seasonal High Ground-water (ft)
Percolation Rate (m.p.i.)
Bed-rooms
Flow (gpd)
Sand Layer Height (ft)
Total Berm Height (ft)
Total Mound Width (ft)
Total Mound Length (ft)
Rock Bed Length (ft)
Uphill Berm Width (ft)
Downhill Berm Width (ft)
End Berm Width (ft)
< 1.0
Construction permit required if less than 12 inches to seasonal high groundwater.
≥ 1.0 and
< 2.0
0
to
30
1
200
3
5
42
49
17
16
16
16
2
300
3
5
42
57
25
16
16
16
3
400
3
5
42
65
33
16
16
16
4
500
3
5
42
74
42
16
16
16
5
600
3
5
42
82
50
16
16
16
31
to
60
1
200
3
5
42
49
17
16
16
16
2
300
3
5
42
57
25
16
16
16
3
400
3
5
42
65
33
16
16
16
4
500
3
5
42
74
42
16
16
16
5
600
3
5
42
82
50
16
16
16












≥ 2.0 and
< 3.0
0
to
30
1
200
2
4
36
42
17
13
13
13
2
300
2
4
36
50
25
13
13
13
3
400
2
4
36
58
33
13
13
13
4
500
2
4
36
67
42
13
13
13
5
600
2
4
36
75
50
13
13
13
31
to
60
1
200
2
4
36
43
17
13
13
13
2
300
2
4
36
51
25
13
13
13
3
400
2
4
36
59
33
13
13
13
4
500
2
4
36
68
42
13
13
13
5
600
2
4
36
76
50
13
13
13












≥ 3.0
0
to
30
1
200
1
3
30
37
17
10
10
10
2
300
1
3
30
45
25
10
10
10
3
400
1
3
30
53
33
10
10
10
4
500
1
3
30
62
42
10
10
10
5
600
1
3
30
70
50
10
10
10
31
to
60
1
200
1
3
34
36
17
12
12
10
2
300
1
3
34
44
25
12
12
10
3
400
1
3
34
52
33
12
12
10
4
500
1
3
34
61
42
12
12
10
5
600
1
3
34
69
50
12
12
10

Table 11.4 - Mound Dimensions for Ground Slope of >1% to 3%

Depth to Seasonal High Ground-water (ft)
Percolation Rate (m.p.i.)
Bed-rooms
Flow (gpd)
Sand Layer Height (ft)
Total Berm Height (ft)
Total Mound Width (ft)
Total Mound Length (ft)
Rock Bed Length (ft)
Uphill Berm Width (ft)
Downhill Berm Width (ft)
End Berm Width (ft)
< 1.0
Construction permit required if less than 12 inches to seasonal high groundwater.
≥ 1.0 and
< 2.0
0
to
30
1
200
3
5
43
49
17
15
18
16
2
300
3
5
43
57
25
15
18
16
3
400
3
5
43
65
33
15
18
16
4
500
3
5
43
74
42
15
18
16
5
600
3
5
43
82
50
15
18
16
31
to
60
1
200
3
5
45
49
17
15
20
16
2
300
3
5
45
57
25
15
20
16
3
400
3
5
45
65
33
15
20
16
4
500
3
5
45
74
42
15
20
16
5
600
3
5
45
82
50
15
20
16






≥ 2.0 and
< 3.0
0
to
30
1
200
2
4
37
43
17
12
15
13
2
300
2
4
37
51
25
12
15
13
3
400
2
4
37
59
33
12
15
13
4
500
2
4
37
68
42
12
15
13
5
600
2
4
37
76
50
12
15
13
31
to
60
1
200
2
4
42
43
17
12
20
13
2
300
2
4
42
51
25
12
20
13
3
400
2
4
42
59
33
12
20
13
4
500
2
4
42
68
42
12
20
13
5
600
2
4
42
76
50
12
20
13






≥ 3.0
0
to
30
1
200
1
3
32
37
17
9
13
10
2
300
1
3
32
45
25
9
13
10
3
400
1
3
32
53
33
9
13
10
4
500
1
3
32
62
42
9
13
10
5
600
1
3
32
70
50
9
13
10
31
to
60
1
200
1
3
39
37
17
9
20
10
2
300
1
3
39
45
25
9
20
10
3
400
1
3
39
53
33
9
20
10
4
500
1
3
39
62
42
9
20
10
5
600
1
3
39
70
50
9
20
10

Table 11.5 - Mound Dimensions for Ground Slope of >3% to 5%

Depth to Seasonal High Ground-water (ft)
Percolation Rate (m.p.i.)
Bed-rooms
Flow (gpd)
Sand Layer Height (ft)
Total Berm Height (ft)
Total Mound Width (ft)
Total Mound Length (ft)
Rock Bed Length (ft)
Uphill Berm Width (ft)
Downhill Berm Width (ft)
End Berm Width (ft)
< 1.0
Construction permit required if less than 12 inches to seasonal high groundwater.
≥ 1.0 and
< 2.0
0
to
30
1
200
3
5
44
49
17
14
20
17
2
300
3
5
44
57
25
14
20
17
3
400
3
5
44
65
33
14
20
17
4
500
3
5
44
74
42
14
20
17
5
600
3
5
44
82
50
14
20
17
31
to
60
1
200
3
5
44
49
17
14
20
17
2
300
3
5
44
57
25
14
20
17
3
400
3
5
44
65
33
14
20
17
4
500
3
5
44
74
42
14
20
17
5
600
3
5
44
82
50
14
20
17






≥ 2.0 and
< 3.0
0
to
30
1
200
2
4
37
43
17
11
16
14
2
300
2
4
37
51
25
11
16
14
3
400
2
4
37
59
33
11
16
14
4
500
2
4
37
68
42
11
16
14
5
600
2
4
37
76
50
11
16
14
31
to
60
1
200
2
4
41
43
17
11
20
14
2
300
2
4
41
51
25
11
20
14
3
400
2
4
41
59
33
11
20
14
4
500
2
4
41
68
42
11
20
14
5
600
2
4
41
76
50
11
20
14






≥ 3.0
0
to
30
1
200
1
3
32
39
17
9
13
11
2
300
1
3
32
47
25
9
13
11
3
400
1
3
32
55
33
9
13
11
4
500
1
3
32
64
42
9
13
11
5
600
1
3
32
72
50
9
13
11
31
to
60
1
200
1
3
39
39
17
9
20
11
2
300
1
3
39
47
25
9
20
11
3
400
1
3
39
55
33
9
20
11
4
500
1
3
39
64
42
9
20
11
5
600
1
3
39
72
50
9
20
11

Table 11.6 - Minimum Force Main Size (inches) – Schedule 40 PVC Pipe

Pumping Rate (gpm)
Total Force Main Length (ft)
0 to 100
>100 to 300
>300 to 500
0 to 20
1 1/4
1 1/2
2
>20 to 40
1 1/2
2
2 1/2
>40 to 60
2
2 1/2
3

Table 11.7 – Design Requirements for Rock Bed Lateral Pipe, Dose Pump, and Pump Tank

Bed-rooms
Flow (gpd)
Rock Bed Length (ft)
End Spacing * (ft)
Number of 3/16" Diameter Holes per Lateral
Number of Spaces at 24" Centers
Minimum Pump Capacity (gpm)
Minimum Pump Discharge Pressure Head ** (ft)
Gallons Pumped per Dose (gal)
Minimum Pump Tank Capacity (gal)
1
200
17
1.5
8
7
15
7 ft + H
70
500
2
300
25
1.5
12
11
22
9 ft + H
95
500
3
400
33
1.5
16
15
29
10 ft + H
120
500
4
500
42
2.0
20
19
36
12 ft + H
145
750
5
600
50
1.0
25
24
44
15 ft + H
170
750
* End Spacing is the distance from either end of the rock bed to the nearest lateral pipe orifice.
** H is the elevation difference between the pump intake and the top of the rock bed.

Enabling Legislation: Neb. Rev. Stat. §81-1505(8).

Legal Citation: Title 124, Ch. 11, Nebraska Department of Environmental Quality.