Type 3 private sewage disposal systems shall be designed to minimum requirements as follows:
A. Pretreatment shall be by septic tank sized for the projected design flow or by a Class I aeration device sized for the projected design flow.
B. The soil absorption area shall be prepared prior to placement of any fill in accordance with § 8.04.430 M - Q. The fill material shall extend a minimum of five (5) feet beyond any absorption trench.
C. Distribution to the absorption trench may be by drop box, distribution box, or low-pressure pipe (LPP) distribution. LPP network piping shall be as specified in § 8.04.540.
E. No perforated pipe shall be located closer than three (3) feet to the distribution device.
F. The invert of the distribution pipe shall be a minimum of six (6) inches above the trench bottom.
G.
1. The square footage of a gravel trench bottom shall be per Column 8 of Table 1 for residential properties; and equal to the projected flow in gallons per day (GPD) divided by the assigned domestic wastewater loading rate in gallons per day per square foot (Column 9, Table I) for non-residential properties.
2. The soil loading rate is determined by the most restrictive permeability within 24 inches below the aggregate in moderate soils, 36 inches below the aggregate in moderately rapid soils and 48 inches below the aggregate in rapidly permeable soils.
3. Illinois Department of Public Health approved chambers will be sized at one (1) lineal foot of chamber per lineal foot of three (3) foot wide gravel trench for those chambers with approved absorption areas of at least three (3) square feet per linear foot; OR
4. Will be sized at one (1) lineal foot of chamber per lineal foot of two (2) foot wide gravel trench for those chambers with approved absorption areas of at least two (2) square feet per lineal foot but less than three (3) square feet per linear foot.
H. The maximum trench length shall be one hundred (100) feet from the distribution device (excluding the solid header).
I. The maximum trench width shall be thirty-six (36) inches; the minimum trench width shall be twelve (12) inches.
J. Trenches shall be separated by a minimum of five (5) feet of undisturbed soil. See Tables VI and IX.
K. The bottom of trench of a Type 3 system shall penetrate the original soil surface by a minimum of six (6) inches.
L. The minimum depth of gravel in the absorption trench shall be twelve (12) inches, with six (6) inches of gravel below the pipe and two (2) inches above.
M. Gravel shall not be placed closer than three (3) feet to the distribution device.
N. Every Type 3 system shall be covered with a minimum of six (6) inches of earth cover, and a maximum of twenty four (24) inches.
O. Seepage beds shall be sized at 1.5 times the absorption area specified in Table I.
P. Type 3 systems shall meet the requirements of all other applicable sections of the Ordinance.
(Ord. O-201711-51-031, passed 11-14-2017)