ADPH – PUBLIC HEALTH AREA VIII TRAINING FOR PROFESSIONAL ENGINEERS And Associated Onsite System Professionals

1. Design Choices
Options Based on Site Limitations

2. Types of Restrictions Under
Consideration
• ASHES/Water table/Chroma 2’s
– Trumps all other restrictive features
• Fragipan
• Permeability

3. ASHES < 6 Inches
• Drip Irrigation
–
–
–
–
Control Fill System
12 inches of separation between tube and ASHES
Advanced treatment required (420‐3‐1‐.57(8)(c))
Requires less fill due to size of tube and depth of tube (12
cover + 12 separation = 24 inch “mound”)
• Control Fill (not drip)
– 12 inches of separation between trench bottom and ASHES
– Advanced treatment required (Same rule cite)
– Fill could be 36 inches in height (12 cover + 12 trench + 12
separation)

4. ASHES > 6 Inches
• Pre‐treatment allows 12 inches separation distance from
ASHES
• Options
– Drip (always requires pre‐treatment)
– Control Fill
• Any disposal product
• Separation distance is dependent on permeability
– 5‐60 min/inch must have 24 inches
– 61‐240 min/inch must have 18 inches
– Wisconsin Mound
• Permeability <120 min/inch
• Must have 12 inches of original soil before ASHES
– >26 inches allows for shallow conventional (8 inch product & 61‐
240 min/inch) – needs 12 inches of cover

5. Fragipan
• Chroma 2’s trump if present
• Other restriction – 12 inch MVS
• System options depends on depth

6. Permeability
• <1 or > 240 min/inch
– Advanced treatment required
• Options
– Same as ASHES and Rock
• Drip or Control Fill
• Drip may be more attractive due to size of system and
or size of “mound”
• Alabama LPP may also be used

7. Conclusion
• ASHES/Water Table/Chroma 2’s trumps all
other restrictions
• Extreme sites (shallow depth to ASHES &
Fragipans, very slow permeability) are difficult
at best for designing OSS’s
• Options are limited