§ 30-237. Absorption fields.

(a)

Area computation . The following criteria shall be used to determine the amount of absorption field required:

(1)

Single family residential buildings.

a.

Alternative systems. Alternative systems which have been approved by the health department may be required if either or both of the following conditions are present:

1.

Heavy clay: the soil type in the absorption site is a heavy clay series (as determined by the USDA Soil Survey of Wyandotte County), with or without slope; or

2.

Slowly permeable soil with level surface area: the soil type in the absorption site is of any slowly permeable soil series (0.2 inches per hour or less, as determined by the USDA Soil Survey of Wyandotte County) and the undisturbed absorption site has a level surface area.

b.

Conventional septic tank-lateral field systems.

1.

Conventional sequential step-down septic tank-lateral field systems may be utilized in sloping, slowly permeable soils. The absorption field in those conditions shall be sized as listed below:

Number of bedrooms	1	2	3 or more	For each bedroom beyond 3
Square feet of absorption trench	500	1,000	1,500	+ 500
Linear feet of 3' wide trench	167	334	500

 

2.

Conventional septic tank-lateral field systems may be utilized in sloping or level moderately to rapidly permeable soils (as determined by the USDA Soil Survey of Wyandotte County). The absorption field in those conditions shall be sized as listed below:

Number of bedrooms	1	2	3 or more	For each bedroom beyond 3
Square feet of absorption trench	400	800	1,200	+ 400
Linear feet of 3' wide trench	134	267	400

 

(2)

Non-residential buildings . Requirements for the size of absorption field shall be determined by the health department. Professional manuals such as the EPA Design Manual, International Plumbing Code, or the Uniform Plumbing Code may be referred to for guidance to help determine adequate sizing. When expected non-farm water usage exceeds 10,000 gallons per month, the owner(s) of the establishment shall construct a dual absorption field system according to health department regulations.

(3)

Multi-family buildings . Requirements for the size of absorption fields which will serve multi-family buildings (i.e., group homes, foster homes, etc.) shall follow the same sizing requirements as for a single-family residence. When expected non-farm water usage exceeds 10,000 gallons per month, the owner(s) of the establishment shall construct a dual absorption field system according to health department regulations.

(4)

Existing buildings . Absorption fields constructed or repaired which serve existing buildings shall follow the same absorption field sizing requirements as newly constructed buildings whenever possible. When site or area constraints will not allow adequate area to accomplish sizing requirements for new construction, then absorption fields shall be sized as large as physically possible to meet the same requirements as that of new construction. All other requirements for septic tank and absorption field construction and installation shall be required as stated within these regulations.

(5)

Other . The absorption field size shall be determined by the Health Department based on the anticipated loading, water use, and sewage produced. A minimum of 300 lineal feet of absorption trench shall be required.

(b)

Absorption field location restrictions. Unless otherwise approved by the health department, the absorption field shall be located as set forth in Table 1. Unless otherwise approved by the health department, no part of an absorption field installed after the effective date of this Sanitary Code shall be located within:

(1)

Ten feet of any private water line, septic tank, foundation drain, buried utility line, driveway, property line, or drop-off.

(2)

Twenty-five feet of any house or other building, water meter (p. 4, KDHE Bulletin 4-2, or as amended), or public water main.

(3)

Fifty feet of any in-ground swimming pool, surface water course, creek bank, stream, river, pond, or lake (p. 4, KDHE Bulletin 4-2, or as amended).

(4)

One hundred feet of any water well.

(5)

Absorption fields shall not be installed in the floodplain nor where groundwater or adverse geological formations may interfere with the absorption of treated sewage or result in the contamination of groundwater by sewage.

(6)

The health department may require that a licensed surveyor stake or flag the floodplain in areas where it is difficult to determine floodplain locations.

(7)

Absorption fields shall not be installed in areas subject to excessive surface water, ponding, or runoff, including but not limited to storm water and discharge from building gutters.

(8)

No absorption field, or any portion thereof, shall be placed within any fill material unless such fill material is specifically approved in writing by the health department prior to installation of the absorption field. Installation of any absorption field within fill material not approved by the health department may be cause for revocation of the onsite sewage management system construction permit.

(9)

The health department, after site inspection, may require variations of these distances due to adverse conditions relative to topography, subsurface soil characteristics, and / or groundwater sources. No part of the absorption field shall be covered by buildings or pavement or be used for vehicular traffic or parking.

(c)

Site preparation. The area in which the on-site sewage management system is proposed to be constructed shall not have any of the original topsoil removed from the area without specific written approval from the health department. Removal of topsoil from the area may be cause for revocation of the on-site sewage management system construction permit.

(d)

General requirements for design and construction of absorption fields.

(1)

An absorption trench shall not exceed 100 feet in length from where it is fed unless specific approval is given by the health department.

(2)

Absorption trenches shall be between 27 inches and 39 inches in depth.

(3)

The trench shall be 36 inches wide, unless otherwise specifically approved by the health department.

(4)

Installation of absorption trenches must be along contour lines that the level trenches of uniform depth can be constructed unless otherwise specifically approved by the health department.

(5)

There shall be a minimum of 12 inches of earth cover over the lateral rock or chamber system and a maximum of 24 inches of earth cover over the lateral rock or chamber system.

(6)

Excavation for absorption trenches in wet clay soils and smearing of trench walls and bottoms shall be avoided since reduced permeability may result and approvals may be voided thereby.

(7)

The ground surface of the absorption field area shall be so graded as to prevent the accumulation of surface water and to minimize the flow of surface water over the absorption field. Test holes, diverter ditches or flow control devices will be required under some circumstances. It may be necessary to prepare the ground for the absorption field, such as by removal of rocks, trees, or replacement of soil. The health department may require that the preparation work for the absorption field be inspected and approved prior to the installation of the absorption field.

(8)

There shall be a minimum of four feet between the bottom of the absorption trench and any groundwater table.

(9)

There shall be a minimum distance of 12 feet between absorption trench sidewalls, or 15 feet between trench centers, unless specifically approved by the health department.

(e)

General requirements for field layout methods.

(1)

Sequential step-down or "overhead" conventional system. This method is well suited to terrain with a slope. In this system, effluent is not distributed equally to all the absorption trenches. Instead, the trenches are filled sequentially, and diversion to the next trench does not occur until the fluid level in the preceding trench reaches slightly above the top of the rock fill or chamber system.

a.

The overhead distribution line must be connected toward the center of each absorption trench, unless specifically approved by the health department.

b.

The overhead distribution line must be set on a firm foundation of undisturbed earth or compacted earth or sand. Gravel shall not be placed beneath the overhead line.

c.

The sequential system is illustrated in Figure C.

(2)

Level field conventional system. On flat terrain the level field method may be used. When this method is used, all distribution trenches shall be installed level and at the same elevation, shall not exceed 100 feet in length, and shall be connected at the ends to form a continuous system. A standard tee fitting shall be used to distribute treated sewage. A standard tee fitting shall be used to affect a juncture of the ends of any three distribution lines. The level field method is illustrated in Figure D.

(f)

Additional requirements for absorption fields utilizing lateral rock. The following requirements are in addition to all other requirements noted within these regulations:

(1)

A 15-inch depth of three-fourths to two-inch (p. 12, KDHE Bulletin 4-2, or as amended) washed lateral rock (i.e., aggregate) shall be provided in the bottom of the trench (as detailed in "c" below).

(2)

Perforated pipe shall be laid in the center of the lateral rock. Perforations shall be oriented toward the bottom of the trench.

(3)

Lateral rock shall be placed under the perforated pipe to a minimum depth of six inches and shall extend the full length of the trench. Five inches of lateral rock shall cover the perforated pipe.

(4)

A continuous layer of permeable material shall be placed over the lateral rock before backfilling with the earth cover. The permeable material shall be four to six inches of hay or straw, or another material approved by the health department.

(g)

Additional requirements for absorption fields utilizing chamber systems. The following requirements are in addition to all other requirements noted within these regulations:

(1)

Inspection ports may be required by the health department for monitoring purposes.

(2)

The end plates of each chamber trench shall be constructed of plastic, made by the manufacturer of the chamber system, and shall be securely fastened to the chambers with screws.

(3)

All chamber systems located in sandy soils shall be required to have washed lateral rock, hay, straw, or filter fabric placed between the excavated trench and the outside sidewalls of the chamber units to prevent infiltration of soil into the chamber units.

(4)

The overhead distribution pipe shall be fed into the top of the chamber (unless otherwise specifically approved by the health department) with a standard PVC tee fitting. The PVC tee shall extend downward midway into the depth of the chamber.

(Ord. No. O-51-18 , § 6, 12-6-2018)