SEPTIC INSTALLER WASHINGTON STATE
WOSSA STUDY BANK 2026 VERIFIED
SOLUTIONS GRADED A+
⩥ What is a bed?
Answer: Bed - A solid dispersal component, excavation width of 3ft+.
⩥ What is a BOD?
Answer: BOD - biochemical oxygen demand
⩥ How far outside of a building wall will a drain connect to a sewer?
Answer: Building Drain/Sewer Connection - 2ft outside building wall.
⩥ What is a cesspool?
Answer: Cesspool - Collection site for untreated sewage
⩥ What is Cover Material made out of?
Answer: Cover Material - mineral material less than 10% organic
content
⩥ What period does Design Flow account for?
Answer: Design Flow - Max designed capacity for 24 Hour period
,⩥ What is Drain Rock?
Answer: Drain Rock - clean washed gravel/crushed rock (3/4 to 2.5
inch), 3% by weight passing No. 8 sieve or 1% by weight passing No.
200 sieve
⩥ What are CBODs?
Answer: CBODs - carbonaceous biochemical oxygen demand (mg/L)
⩥ What is E. coli? What is Fecal Coliform?
Answer: E. coli - comes from warm-blooded animal wate, colony
forming units/100 mL.
Fecal Coliform - animal/human wate & some environmental, colony
forming units/100 mL
⩥ What is the difference between Gravelly and Extremely Gravelly?
Answer: Gravelly - soils with 15 - 35% rock fragments
Very gravelly - 35 - 60% rock fragments
Extremely gravelly - soils with 60-90% rock fragments.
⩥ What is a LOSS?
Answer: LOSS - large on-site septic system
, ⩥ What is O&M?
Answer: O&M - Operation & Management often referring to OSS
Manuals
⩥ What is DS&G?
Answer: DS&G - Department Standards & Guidance often referring to
OSS Manuals
⩥ What is considered a Minor Repair?
Answer: Minor Repair - doesn't include septic tank, treatment
component, or soil dispersal component.
⩥ What is Minimum Usable Land Area referring to?
Answer: Minimum Usable Land Area - minimum land required for OSS,
free of physical restrictions and minimum separations.
⩥ When excavating test sites, what do Redoximorpic Features signify?
Answer: Redoximorphic Features/Mottling - spots/blotches of different
color/shade of color caused by reduction/oxidation of iron.
Indicate intermittent presence of groundwater or poor aeration and
impeded drainage.
WOSSA STUDY BANK 2026 VERIFIED
SOLUTIONS GRADED A+
⩥ What is a bed?
Answer: Bed - A solid dispersal component, excavation width of 3ft+.
⩥ What is a BOD?
Answer: BOD - biochemical oxygen demand
⩥ How far outside of a building wall will a drain connect to a sewer?
Answer: Building Drain/Sewer Connection - 2ft outside building wall.
⩥ What is a cesspool?
Answer: Cesspool - Collection site for untreated sewage
⩥ What is Cover Material made out of?
Answer: Cover Material - mineral material less than 10% organic
content
⩥ What period does Design Flow account for?
Answer: Design Flow - Max designed capacity for 24 Hour period
,⩥ What is Drain Rock?
Answer: Drain Rock - clean washed gravel/crushed rock (3/4 to 2.5
inch), 3% by weight passing No. 8 sieve or 1% by weight passing No.
200 sieve
⩥ What are CBODs?
Answer: CBODs - carbonaceous biochemical oxygen demand (mg/L)
⩥ What is E. coli? What is Fecal Coliform?
Answer: E. coli - comes from warm-blooded animal wate, colony
forming units/100 mL.
Fecal Coliform - animal/human wate & some environmental, colony
forming units/100 mL
⩥ What is the difference between Gravelly and Extremely Gravelly?
Answer: Gravelly - soils with 15 - 35% rock fragments
Very gravelly - 35 - 60% rock fragments
Extremely gravelly - soils with 60-90% rock fragments.
⩥ What is a LOSS?
Answer: LOSS - large on-site septic system
, ⩥ What is O&M?
Answer: O&M - Operation & Management often referring to OSS
Manuals
⩥ What is DS&G?
Answer: DS&G - Department Standards & Guidance often referring to
OSS Manuals
⩥ What is considered a Minor Repair?
Answer: Minor Repair - doesn't include septic tank, treatment
component, or soil dispersal component.
⩥ What is Minimum Usable Land Area referring to?
Answer: Minimum Usable Land Area - minimum land required for OSS,
free of physical restrictions and minimum separations.
⩥ When excavating test sites, what do Redoximorpic Features signify?
Answer: Redoximorphic Features/Mottling - spots/blotches of different
color/shade of color caused by reduction/oxidation of iron.
Indicate intermittent presence of groundwater or poor aeration and
impeded drainage.
