A. General Sewage Collection And Disposal Requirements:
1. Developments and occupied facilities shall be connected to an approved and functioning public or community sewage collection and centralized treatment system, where such a system is available. Where public or community sewers and a centralized treatment plant are not available, developments shall provide and occupied facilities shall be connected to such a collection and treatment system when required by the county, as discussed in this section.
2. The use of individual lot or building on site sewage disposal systems or facilities shall be restricted and shall be dependent on local soil and groundwater conditions and the known or anticipated extent/density of development within the area. The use of cluster on site disposal systems may be required by the county health department to overcome adverse site conditions.
3. Depending on the number of dwelling units, residential developments shall be connected to an existing sanitary sewer system if service is available, within the following distances from the nearest property line to the sanitary sewer as shown in table 8-6-3-6, "Sanitary Sewer System Distance Requirements", of this section.
Development Size | Distance |
1 unit | 300 feet |
2 units | 400 feet |
3 units | 600 feet |
4 units | 800 feet |
5 - 15 units | 1,000 feet |
4. When a residential subdivision or development with more than fifteen (15) units is located within one mile of an existing sanitary sewer system, adequate justification shall be provided as to why it should not be connected to the existing sewer system. For residential developments with more than fifteen (15) units and located more than one mile from an existing system, sewage disposal strategy shall be determined on a case by case basis, taking into consideration the density of development, costs, and the concerns and criteria noted in this section.
5. Small scale nonresidential developments may be required to be connected to an existing sanitary sewer system if service is available within one thousand feet (1,000'). Requirements for large scale nonresidential development within or more than one mile from an existing system shall be as indicated in subsection A4 of this section. Judgments and decisions regarding nonresidential factors such as size, water use, and suitability of on site sewage disposal facilities shall be as reasonably determined by the county on an individual basis taking into account the specific characteristics of the development.
6. A complete public or community sewage collection and centralized treatment system may be required by the county in order to:
a. Protect the quality of groundwater that may be used for potable water.
b. Protect the quality of surface waters including wetlands, streams, ponds, lakes, and rivers.
c. Maintain the quality of aquatic habitats, thereby protecting a variety of plant and animal species.
d. Prevent failure of individual sewage disposal systems.
e. Protect citizens from the health hazards associated with the failure of individual sewage disposal systems.
f. Protect public investments in public sewer systems.
7. The following conditions shall be evaluated in determining the necessity of a public or community sewage system in place of individual or cluster on site sewage disposal systems:
a. Location of the development with regard to extraterritorial limits of municipalities with public sewage systems.
b. Classification of the soils within areas proposed or needed for septic ground absorption fields, with regard to the suitability or restrictions of these soils for such absorption fields. The land use department requires that, prior to permitting and installing a new septic system, a soil evaluation, performed by a member of the Illinois Soil Classifier Association, must be made in the area that the proposed system is to be installed. This percolation ("perc") test is necessary to determine the absorption capacity of soils, and the test results will be useful in determining the appropriate type of sewage disposal system.
c. The possibility of future adjacent development that could negatively impact the concerns noted in subsection A6 of this section.
8. If a sanitary sewer system is not available and a new community sewage system with centralized treatment is not warranted or feasible, residential housing units and nonresidential facilities shall be served by individual or cluster on site sewage disposal systems.
a. Development density and lot sizes shall be in accordance with county requirements for the use of such on site disposal systems.
b. The type and design of these on site systems shall be subject to specific site conditions listed by the county health department. They include, but are not limited to, topography, soil types, bedrock, and groundwater.
c. The use of cluster systems or other alternative on site collection and treatment systems may be required to overcome unsuitable conditions. A cluster system shall typically consist of individual septic tanks for each lot or building, a gravity or pressure sewer system, and a small neighborhood treatment facility such as a sand filter or aerobic plant.
d. The use, design, installation, and operation of all on site sewage disposal systems shall conform to the requirements of the county health department and will require a permit issued by said department.
(1) In some cases, permit approval of the Illinois EPA will be required in lieu of county approval. Systems that are regulated by the IEPA are not regulated by the county health department.
(2) The county health department enforces the Illinois private sewage disposal act and code which is promulgated, published, and enforced by the Illinois department of public health (IDPH). The county has adopted and does enforce standards that are more stringent than those of the IDPH.
9. If it is determined that soil conditions will not support on site disposal and a satisfactory central collection and disposal system cannot be provided and maintained, the subdivision or development project shall be denied by the county board.
10. Due to adverse soil or water table conditions, the following requirements shall apply: Individual dwellings within subdivisions of three (3) or more lots and nonresidential and multi-family residential facilities within any size development that are otherwise permitted to have individual on site sewage disposal systems may be required to have one of the following alternative on site disposal systems in lieu of a conventional septic tank seepage field system. Specific requirements shall be as specified by the county health department upon determination of actual site conditions.
a. Septic tank with pumped discharge to an elevated sand filter (Wisconsin mound).
b. Septic tank with a buried sand filter and trickle trenches.
c. Aerobic treatment plant with pumped discharge to a full size seepage field, a buried sand filter, or an elevated sand filter (Wisconsin mound).
d. Aerobic plant with a trickle trench connected to a subsurface drainage pipe or storm sewer.
e. Other approved "alternative" systems.
11. Developments that are permitted to have individual sand filter or aerobic plant on site sewage disposal systems will be required to install common, community discharge sewers connecting all individual on site systems to an acceptable receiving stream or body of water, if the local site, soil, and groundwater conditions indicated in subsection A10 of this section will prevent adequate subsurface disposal of effluent from seepage fields or sand filters. Determination of local conditions and the need for common discharge sewers shall be by the county health department.
12. When soil conditions are rated severe for ground absorption disposal of effluent, installation of a subsurface drainage system may be required (by the county health department) to lower the groundwater level. Such drainage systems shall be designed to prevent entry of sewage system effluent.
13. If a public or community sewage collection and treatment system is required, an agreement between the county and the applicant (developer) may be established (at the county's option) to enable equitable recoupment of system construction and operating costs if other developments connect to the system.
14. If a sanitary sewer system will be provided to the area within a five (5) year period as indicated in a sewer master plan, official map, or other official document, the county may require installation of a capped system, or "dry lines" (mains only), or the county may require a payment in lieu of the improvements.
15. All proposals for new sanitary sewer systems, or extensions to existing sewer systems, or the installation of "dry lines", or the use of individual on site disposal systems shall be subject to the approval of the county.
B. Public System Capacity:
1. Sanitary sewer systems shall be adequate to handle anticipated flows based on complete development of the defined service area. Sewer flow from future development areas shall be based on estimates of development type and density as determined by the Illinois EPA. Sewers shall be designed to carry peak flows from the areas served.
2. Average and peak flows from proposed development areas and facilities shall be calculated from sewage flow guides and standards determined to be acceptable to both the county and the Illinois EPA.
3. Daily sewer flows from residential areas shall be determined from the population served. For design purposes, average daily wastewater flow shall be assumed to be one hundred (100) gallons per day (gpd) per person. A lower per capita flow rate may be used if it can be substantiated to the satisfaction of both the county and the Illinois EPA.
4. Peak flows for residential area systems with populations of less than five hundred (500) people shall be assumed to be four (4) times average daily flow. Peak flow ratios for larger systems shall be determined from the following formula:
O max | = | 18 + (P)1/2, where P = population in thousands |
O avg | 4 + (P)1/2 |
C. System Design And Layout:
1. General Design And Layout Requirements:
a. Sewage system criteria and standards shall be in accordance with accepted engineering practices regarding such systems. The county shall have the prerogative to make use of those practices that it believes to represent the best available information and procedures.
b. Alternatives to standard gravity sewer systems such as pressure sewers (grinder pump or septic tank effluent pump), small diameter gravity sewers, and vacuum sewers may be permitted by the county, depending on specific development and site conditions and circumstances.
c. Sewage collection and treatment facilities shall be designed and constructed to conform with all applicable EPA regulations and permit requirements.
2. Location Of Public Sewers:
a. Sanitary sewers shall typically be located within street rights of way or in utility easements adjacent to street rights of way.
b. Sanitary sewers may be located within open space areas or along rear or side lot lines, if such a layout provides an efficient system and if adequate maintenance access is provided to all manholes.
c. If maintenance access cannot be provided to an entire section of sewer between manholes, or if a sewer is close to a building or within a high groundwater area, or if it passes under a creek or river, the use of water main quality pressure pipe shall be required.
d. All sewers not within dedicated street rights of way shall be located within defined utility easements. Easements adjacent to street rights of way shall be at least ten feet (10') wide. Sanitary easements otherwise located shall have a minimum width of twenty feet (20').
e. Sanitary sewers shall not be located closer than twenty feet (20') from any building or structure.
f. Any sewer within one hundred feet (100') of a water supply well or a below ground water storage reservoir shall be constructed of water main quality pressure pipe.
3. Public Sewer Mains (Standard Gravity Systems):
a. Sewer flow capacity shall be calculated by the Manning formula using n = 0.013. Minimum allowable velocity with pipe full or half full shall be two feet (2') per second (fps). Maximum velocity shall be ten (10) fps.
b. The minimum sewer size shall be eight inches (8") in diameter.
c. The minimum slope for eight inch (8") sewers shall be 0.4 percent. Where possible, a slope greater than minimum shall be provided for sewers with limited use to minimize blockages due to low flow.
d. The maximum manhole spacing shall be four hundred feet (400').
e. The minimum sewer depth shall typically be eight feet (8') to avoid utility conflicts. The minimum depth in a special case circumstance shall be five feet (5').
4. Building Services:
a. Minimum gravity service sewer size shall be four inches (4") in diameter. The minimum slope shall be one percent (1%).
b. Two (2) service sewers may be placed in the same trench when they serve adjacent attached units.
c. A common service sewer may be permitted for multi-family housing or multi-unit nonresidential buildings where there is an entity (such as an owners' association) responsible for the maintenance of the common services.
d. Service risers shall be provided where the sewer depth exceeds twelve feet (12').
5. Additional Requirements: Sanitary sewer system material, equipment, and construction requirements shall be as indicated in the specifications included in this chapter. (Ord. 10-001, 1-12-2010)
Notes
| 1 | 1. See also title 5, chapter 2 of this code. |