A. Design of Soil Absorption System. The construction of any private sewage disposal system requiring soil for ultimate treatment, shall conform to the requirements herein established. The septic system design shall be prepared by a professional designer meeting the qualifications of § 8.04.370 Q experienced in the field of on-site private sewage disposal system design. The system shall be designed to receive all domestic sewage from the structure proposed to be served. Plans and specifications shall be in accord with the requirements in § 8.04.370 P of this Ordinance.
B. Basis of Design. Septic system sizing is determined by the most restrictive soil boring in the area of the seepage field. (See Table I, Appendix B). When a less permeable soil layer is located less than twenty-four (24) inches in moderate soils; less than thirty-six (36) inches in moderately rapid soils; or less than forty-eight (48) inches in rapid soils; from the bottom of the subsurface seepage system; the seepage system shall be sized at the more limiting permeability. The Department will allow split sizing based upon the most restrictive of two (2) soil borings which delineate that portion of the seepage field.
C. Soil Absorption System Sizing. The minimum design for a private sewage disposal system serving any structure, building or group of buildings, shall be based on the permeability range in inches per hour from Table I (See Appendix B). This shall be used to determine the maximum sewage loading rate (gallons per square foot per day) for establishing bottom soil absorption area (square feet). When the sewage flow exceeds 1500 gal./day, and there is to be a surface discharge system, then approval shall be obtained from the IEPA. Residential designs shall be based upon square footage per bedroom.
D. Metered Water Use Data. The Department will consider, for other than residential properties, metered water use data in lieu of the estimated sewage flow set forth in Table II (See Appendix B). For metered flow considerations, the applicant shall provide authenticated monthly water use data, documenting water consumption for the most recent 12 month period for at least three (3) other establishments of like size operations engaged in the same type geographic environment, and which have approximately the same operating hours.
E. Location and Installation. The private sewage disposal system shall be located in the same area where the soil investigation was conducted for which the system design was approved. All private sewage disposal systems shall be located and installed so that with proper maintenance, the system functions in a sanitary manner, does not create sanitary nuisances or health hazards and does not endanger the safety of any domestic water supply. Sewage waste and effluent from individual on-site private sewage disposal systems shall not be discharged onto the ground surface or into ditches, drainage structures, surface waters, or aquifers. The minimum distances between components of private sewage disposal systems and water supplies, bodies of water, dwellings, property line and field drain tile listed in Table IV (See Appendix B) shall be observed.
F. Artificial Drains. (Curtain drains, vertical drains or underdrains). The following high water table conditions may be capable of being altered when all of the following conditions can be satisfied:
1. Shallow, perched water table but not confined under pressure.
2. Water table conditions are caused by laterally flowing groundwater.
3. Groundwater table is in granular or coarse textured soils. High groundwater table conditions existing in level sites within soils which are saturated for periods of time are considered as being incapable of effective draining by these methods.
G. Proposals to Lower Groundwater Table Levels. For any proposal for the use of these methods of attempting to lower existing groundwater table levels, hydraulic calculations shall be submitted. The proposal shall be acceptable provided that the hydraulic calculations support the ability of the drainage system to lower the existing groundwater table levels and the drainage system will meet the required setbacks outlined in Table IV. (See Appendix B).
I. Discharge from Drainage System. Any proposed drainage system shall have an acceptable gravity outfall which shall not produce surface water or groundwater problems or nuisances. Discharge to roadside drainage ditches is not permitted without written permission from the responsible highway organization or entity.
J. Installation in Existing Fill Material (sites filled at the time of the adoption date of this Ordinance). Filled sites must be evaluated by means of soil pits for their ability to meet the requirements of § 8.04.420 G and Table I. (See Appendix B.)
K. Sizing in Existing Fill Material. The existing fill material shall meet the requirements of § 8.04.420 G and Table I. Due to the unpredictability of fill material, all onsite domestic wastewater systems installed in existing fill material, twelve (12) inches or greater in depth, shall be sized at the largest sizing category in Table I. In addition, the sewage effluent shall be distributed by low pressure pipe distribution.
L. Installation of Septic Systems Which Require Fill. Whenever a private sewage disposal system design incorporates the addition of fill, the designer shall provide a written assessment of the impact of the fill on the retention or drainage of surface waters on the subject and adjacent properties.
M. Site Preparation. Any preparation of the soil absorption area shall be conducted only when the soil is dry. Site preparation shall be conducted under the supervision of the licensed private sewage disposal system installation contractor as established in this Section. All sites shall be mowed and cleared of brush. Sites approved for private sewage disposal system types 3, 4 and 5 (See § 8.04.470 - § 8.04.490 and Illustration 1) shall be plowed prior to the placement of fill or gravel as follows:
1. Equipment. Equipment shall be a chiselplow.
2. Plowing. Plowing shall be done parallel to the site contour.
3. Tillage. Tillage shall be minimal to break the consistency of the sod; maximum depth of tilling shall be eight inches. After tilling, the site shall not be graded or smoothed.
N. Fill Placement. The placement of fill material for private sewage disposal system types 3, 4 and 5 shall be as established in this section. Fill shall be approved coarse graded sand (FA1, FA2, FA3) except in the type 4 at-grade system where only gravel is required, but is handled and placed in the same manner as fill; or porous earth fill (as defined) with certification from a soil classifier; and except that the top four (4) inches shall be top soil for the restoration of vegetation. The fill shall be placed according to the approved plan and shall be placed immediately after site preparation. The storage and transportation of fill shall be as specified on the approved plan; no traffic shall be allowed directly on the plowed area.
O. Method of Fill Placement. Fill shall be placed only from the upslope or ends of the proposed soil absorption area as follows:
P. Using Backhoe. Material may be placed with a backhoe reaching into the soil absorption area.
Q. Using Low Compaction Equipment. Material may be pushed into the soil absorption area by low compression equipment maintaining a minimum of ten (10) inches of material beneath the equipment.
R. Installation in Fine Textured Soils. To prevent soil smearing and excessive compaction, seepage fields shall not be installed within forty eight (48) hours of 1/2 inch or greater rainfall. Seepage fields which are partially or wholly above grade shall not be installed when there is any frost in the ground. Seepage fields which are wholly into grade shall not be installed when there is six (6) inches or more of frost in the ground. It is the responsibility of the private sewage disposal system installation contractor to evaluate site conditions and assure that the installation will not result in smearing of soils or excessive soil compaction.
S. Replacement Systems. There shall be no limit on the number of additional conventional private sewage disposal systems installed as replacements for existing systems.
(Ord. O-201711-51-031, passed 11-14-2017)