Type 5 Mound Systems shall be designed to minimum requirements as follows:
A. Pretreatment shall be by septic tank sized for the projected flow and augmented by an effluent filter, or by a Class I aeration device sized for the projected flow.
B. The soil infiltration area shall be plowed and filled in accordance with § 8.04.430 M – Q. The fill material shall cover the soil infiltration area, or basal area.
C. Coarse sand fill shall have an effective diameter of .15 to 2.0 mm with a uniformity coefficient between 4 and 6, and have less than 5% silt and clay.
D. Distribution to and into the application bed shall be by low pressure pipe (LPP). LPP network piping shall be as specified in this section and in § 8.04.540.
F. The invert of the distribution line(s) shall be a minimum of six (6) inches above the fill material.
G. The square footage of the application bed (absorption area) shall be equal to the projected daily flow in gallons per day (200 gallons per bedroom for residential properties, and per Table II for non-residential properties) divided by the loading rate of the coarse sand fill - one gallon per day per square foot (1 GPD/sq. ft.) or 1.2 GPD/sq. ft. where a Class I aeration device is proposed for pretreatment.
H. The minimum length of the application bed parallel to the site contour shall be limited by the maximum linear loading rate. The linear loading rate is equal to the projected daily flow in gallons per day divided by the total length of the application bed in feet, and shall be determined per Column 7 of Table I.
I. The square footage of the infiltration area (basal area) shall be equal to the projected daily flow divided by the assigned soil domestic wastewater loading rate in gallons per day per square foot (Column 6, Table 1).
J. The soil domestic wastewater loading rate is determined by the most restrictive permeability within 24 inches below the sand fill in moderate soils, within 36 inches below the sand fill in moderately rapid soils and within 48 inches below the sand fill in rapidly permeable soils.
K. The basal area is defined based upon the slope of the site. See Illustration 6.
L. The minimum length of the basal area shall be equal to the minimum length of the application bed.
M. The fill material shall be extended beyond the basal area, tapering to grade at a 3:1 slope.
N. The minimum depth of gravel in the application bed shall be twelve (12) inches with six (6) inches of gravel beneath the pipe and two inches above.
O. The minimum depth of coarse sand fill material covering the basal area shall be twelve (12) inches.
P. The entire Type 5 Mound System shall be covered with a minimum of twelve (12) inches of topsoil to support vegetative cover. Additional cover shall be placed over the application bed at a slope in order to shed stormwater.
Q. The gravel of the application bed shall be completely covered with a geotextile fabric prior to the placement of topsoil. Multiple Type 5 systems may be utilized to provide the total seepage area required for a specific application. The minimum separation distance between the basal areas of multiple Type 5 systems shall be six (6) feet. When utilizing multiple Type 5 systems, the fill material for each mound shall taper to grade at a 3:1 slope, which shall be maintained to allow for appropriate drainage off of and between the mounds.
R. Observation ports are optional.
S. Leakage of domestic sewage from the toe of the mound at any time is unacceptable and considered to be a failure of the system.
T. Separation distances from Type 5 septic systems to structures, water wells, bodies of water, etc. shall be measured from the closest portion of the sand fill.
U. Type 5 Mound systems shall meet all requirements of all other applicable sections of the Ordinance and shall comply with the provisions of Wisconsin Mound Soil Absorption System Siting, Design and Construction Manual as incorporated in Appendix A.
V. Illinois Raised Filter Beds shall comply with the requirements of the Illinois Private Sewage Disposal Code, except that:
1. The mantle shall be sized using the formula A=QT/25, where A = Mantle Area, Q = Quantity of domestic sewage per day, and T is thepercolation rate (min/inch). (See Column 10 of Table I). The percolation rate is determined by the most restrictive permeability within 24 inches below the sand fill in moderate soils, within 36 inches below the sand fill in moderately rapid soils and within 48 inches below the sand fill in rapidly permeable soils.
(Ord. O-201711-51-031, passed 11-14-2017)