Figure: 30 TAC §285.91(13)

TABLE XIII: DISPOSAL AND TREATMENT SELECTION CRITERIA

ON-SITE SEWAGE FACILITY⁽⁹⁾ (OSSF)

SOIL TEXTURE OR FRACTURED ROCK⁽¹⁰⁾
(MOST RESTRICTIVE CLASS ALONG
MEDIA⁽¹⁾ or 2 FEET BELOW EXCAVATION)

MINIMUM DEPTH TO GROUNDWATER

MINIMUM DEPTH TO RESTRICTIVE HORIZON⁽¹⁾

Disposal Method (section) Treatment	Class Ia	Class Ib, II⁽⁸⁾ or III⁽⁸⁾	Class IV	Fractured Rock	MEASURED FROM BOTTOM OF MEDIA⁽⁷⁾	MEASURED FROM BOTTOM OF MEDIA⁽⁷⁾
Absorptive drainfield⁽²⁾ (285.33(b)(1))Septic tank	U	S	U	U	2 feet	2 feet
Absorptive drainfield⁽²⁾ Secondary treatment	S⁽⁵⁾	S	U	S⁽⁵⁾	2 feet	2 feet
Lined E-T⁽²⁾ Septic tank	S	S	S	S	N/A	N/A
Lined E-T⁽²⁾ Secondary treatment	S	S	S	S	N/A	N/A
Unlined E-T⁽²⁾ Septic tank	U	S	S	U	2 feet	2 feet
Unlined E-T⁽²⁾ Secondary treatment	S⁽⁵⁾	S	S	S⁽⁵⁾	2 feet	2 feet
Pumped Effluent Drainfield⁽³⁾ Septic tank	U	S	S	U	2 feet	1 foot
Leaching chamber⁽²⁾ Septic tank	U	S	U	U	2 feet	2 feet
Leaching chamber⁽²⁾ Secondary treatment	S⁽⁵⁾	S	U	S⁽⁵⁾	2 feet	2 feet
Gravelless pipe⁽²⁾ Septic tank	U	S	U	U	2 feet	2 feet
Gravelless pipe⁽²⁾ Secondary treatment	S⁽⁵⁾	S	U	S⁽⁵⁾	2 feet	2 feet
Drip Irrigation Septic tank/ filter	U	S	S	U	2 feet	1 foot
Drip Irrigation Secondary treatment/ filter	S⁽⁵⁾	S	S	S⁽⁵⁾	1 foot	6 inches
Low Pressure Dosing Septic tank	U	S	S	U	2 feet	1 foot
Low Pressure Dosing Secondary treatment	S⁽⁵⁾	S	S	S⁽⁵⁾	2 feet	1 foot
Mound⁽⁴⁾ Septic tank	S	S	S	S	2 feet	1.5 feet
Mound⁽⁴⁾ Secondary treatment	S	S	S	S	2 feet	1.5 feet
Surface application Secondary treatment	S⁽⁶⁾	S⁽⁶⁾	S⁽⁶⁾	S⁽⁶⁾	N/A	N/A
Surface application Non-standard treatment	S⁽⁶⁾	S⁽⁶⁾	S⁽⁶⁾	S⁽⁶⁾	N/A	N/A
Soil Substitution⁽²⁾ Septic tank	S	S	U	S	2 feet	2 feet
Soil Substitution⁽²⁾ Secondary Treatment	S	S	U	S	2 feet	2 feet

S = Suitable
U = Unsuitable

(1)   An absorptive drainfield may be used, if a rock horizon is at least 6 inches above the bottom of the excavation, see §285.33(b)(1).
(2)   If the slope in the drainfield area is greater than 30% or is complex, the area is unsuitable for the disposal method.
(3)   Can only be installed in an area where the slope is less than or equal to 2.0%.
(4)   Can only be installed in an area where the slope is less than 10%.
(5)   Requires disinfection before disposal. A form of pressure distribution shall be used for effluent disposal in fractured or fissured rock.
(6)   Requires vegetation cover and disinfection.
(7)   When no media exists, measure from the bottom of the excavation or pipe, whichever is less.
(8)   May require gravel analysis for further suitability analysis (see §285.30(b)(1)(B)).
(9)   If OSSF is located within a Flood Hazard, see §285.31(c)(2) for special planning requirements.
(10) Includes fissured rock.

All OSSFs require surface drainage controls if slope is less than 2%.