USING THE NEW REGULATIONS DESIGNING OWTS… Prepared for the Colorado Professionals in Onsite...
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Transcript of USING THE NEW REGULATIONS DESIGNING OWTS… Prepared for the Colorado Professionals in Onsite...
U S I N G T H E N E W R E G U L AT I O N S
DESIGNING OWTS…
Prepared for the Colorado Professionals in Onsite Wastewater (CPOW) 2014 Conference
by Roger J. Shafer, P.E.
A CLASSIC EXAMPLE“THE EASY LOT”
High Mountain Rd.
Well
SOIL TREATMENT AREA SIZING
• 3 Bedroom Home = (3) x (150 GPD) = 450• No 1.5 factor
• Sandy Loam Soil (16-25 MPI)• LTAR = 0.6 GPD/ft² (Taken from Table 10.1)
• STA = 450 ÷ 0.6 = 750 ft² required
USE 3 TRENCHES – 3’ WIDE BY 84’ LONG
High Mountain Rd.
Well
100’
99’
98’
TRENCHES VERSUS BEDS
• Trench Cons• Trenches take up more area
• 6 foot separation between trenches
• Harder to install• Especially with 3+ trenches• Slower to install dispersal gravel
• Inspection coordination can be difficult
TRENCHES VERSUS BEDS, CONT.
• Trench Pros• Sidewall Area
• Three 3’ X 60’ trenches have 189 s.f. of sidewall versus a 9’ X 60’ bed has 69 s.f. of sidewall area
• Trench resting or alternating• Maintain shallow depths on steep hillsides• Greater dispersion• Greater oxygen transfer• Less soil compaction…
SERIAL VERSUS PARALLEL DISTRIBUTION
• Serial Distribution• Sequential trench failure• Biomat for treatment (creates unsaturated flow)
• Parallel Distribution• Lower loading (hydraulic and organic) to the soils• Allows trench resting• Requires dosing (siphon or pump)• Requires d-box or distributing valve
High Mountain Rd.
Well
100’
99’
98’
IT ALL FLOWS DOWNHILLOR DOES IT?
High Mountain Rd.
Well
100’
99’
98’
PUMP SYSTEM REQUIREMENTS
• Section 43.8 I – Wastewater Pumping and Dosing Systems (items to note)• Floats to be mounted on a stem separate from the pump
discharge assembly• Discharge assembly must have a disconnect union• Must have access riser to grade, and have a watertight
connection to the pump tank• Splice box outside the access riser• Pump breaker separate from alarm breaker• A switch to manually operate the pump• Panels to be UL listed
EXAMPLES
Not good Not good
EXAMPLES
Not good Good
EXAMPLES
Not good Good
EXAMPLES
Not good
SPECIFYING A PUMP SYSTEMWHAT TO PUT IN AND WHAT TO LEAVE OUT
SPECIFYING A PUMP SYSTEM, CONT.
• THE TANK; COMPARTMENT; BASIN• Size• State Approved• Materials (concrete; fiberglass; plastic)• Bury depth• Risers to grade• Type of risers• Inlet and Outlet locations• Anti-floatation• Make and Model
SPECIFYING A PUMP SYSTEM, CONT.
• THE PUMP SYSTEM• Horsepower• Total Dynamic Head and Flow Rate• Voltage• Conventional low-head or well-style• Floats (mechanical; low-voltage; transducer)• Splice Box• Control Panel (indoor; outdoor; etc.)• Audible and Visual Alarm• Make and Model
WHAT ABOUT THE NEIGHBOR’S WELL?
High Mountain Rd.
Well
100’
99’
98’
100’ radius Well
High Mountain Rd.
Well
100’
99’
98’
100’ radius
Well
TABLE 10.2 SIZE ADJUSTMENT FACTORS
Gravity Bed = (450 GPD) ÷ (0.6 GPD/ft²) x (1.2 factor) = 900 ft²
Pressure Dosed Bed = (450 GPD) ÷ (0.6 GPD/ft²) x (1.0 factor) = 750 ft²
TABLE 10.3 SIZE ADJUSTMENT FACTOR
Reduction for Chambers:
Gravity Bed = (900 ft²) x (0.7 factor) = 630 ft² required
Pressure Dosed Bed = (750 ft²) x (0.7 factor) = 525 ft² required
High Mountain Rd.
Well
100’
99’
98’
100’ radius
Well
High Mountain Rd.
Well
100’
99’
98’
100’ radius Well
Well100’
radius
ADVANCED TREATMENT LOADING RATES
SOIL TREATMENT AREA SIZING
• 3 Bedroom Home = (3) x (150 GPD) = 450 GPD• No 1.5 factor
• Sandy Loam Soil (16-25 MPI)• LTAR = 1.0 GPD/ft² (Taken from Table 10.1 for TL3N)
• STA = (450 GPD) ÷ (1.0 GPD/ft²) = 450 ft² required
• Pressure Dosed Bed = (450 ft²) x (1.0 factor) = 450 ft²
• No additional reduction for chambers
• Compared to 525 ft² for a bed with chambers• Not that much difference!
MINIMUM DISTANCES
PRESSURE DOSING REQUIRED
ITEM OWTS DESIGN CONSIDERATION
Treatment Levels 1 and 2
Treatment Level 2N
Treatment Level 3
Treatment Level 3N
Horizontal Separation Distances
1 Distance from soil treatment area to on-site well
Greater than or equal to 100 feet
Greater than or equal to 100 feet
Greater than or equal to 100 feet
Greater than or equal to 75 feet
2 Distance from soil treatment area to pond, creek, lake, or other surface water feature
Greater than or equal to 50 feet
Greater than or equal to 25 feet
Greater than or equal to 25 feet
Greater than or equal to 25 feet
3 Distance from soil treatment area to dry gulch or cut bank
Greater than or equal to 25 feet
Greater than or equal to 10 feet
Greater than or equal to 10 feet
Greater than or equal to 10 feet
Vertical Separation Distances
4 Depth in feet from soil treatment area infiltrative surface to restrictive layer or ground water
4 feet (3 feet with pressure dosing)
Greater than or equal to 2 feet
Greater than or equal to 2 feet
Greater than or equal to 2 feet
TABLE 7-2SEPARATION DISTANCES FROM SOIL TREATMENT AREA
High Mountain Rd.
Well
100’
99’
98’
100’ radius Well
Well100’
radius
75’ radius
Alt. area
REAL-WORLD EXAMPLES
> 25 feet with TL3N
Soil Treatment Area
Residence
Treatment Unit
Stream
Retaining Wall Retaining Wall
STREAM
PROPERTY LINE
HOUSE
WELL
SOIL TREATMENT AREA
TREATMENT UNIT
> 25’ with TL3
<75’ with TL3
WHY USE ADVANCED TREATMENT?
• Separation Distance Reduction• Horizontal and vertical
• Required by County• Special Watershed Requirement• Lot Size Requirement• Distance Reduction to Wells (for counties with greater
distance requirements)
• Higher loading rates = smaller STA• If you don’t use chambers or chamber reduction not
allowed in your county
WHY USE ADVANCED TREATMENT, CONT.
• In Very Clayey Soils• Biomat plugging a bigger issue in clayey soils
• An accumulation of risk factors• Development Density• Shallow bedrock or ground water• Proximity to surface water• Lack of repair field location• Steep slopes
QUESTIONS?R O G E R J . S H A F E R , P. E
r s h a f e r @ s c g e n t e r p r i s e s . c o m