ALTERNATE ONLOT SEWAGE SYSTEMS

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ALTERNATEON-LOT SEWAGE SYSTEMS

• by
• Albert Jarrett,
• Professor of Biological Engineering
• Penn State University

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The Pennsylvania Protocol

• In Chapter 73 (Conventional).
• In-Ground Systems (Limiting Zone gt60 in).
• Beds.
• Trenches.
• Subsurface Sand Filters.
• Elevated Sand Mounds (Limiting Zone gt20 in).
• Individual Residential Spray Irrigation System
• Bedrock Limiting Zone gt 16 in.
• Water Table Limiting Zone gt10 in.

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The Pennsylvania Protocol

• There are two additional categories
• Alternate Systems.
• Started as an Experimental System.
• Was tested and approved for use.
• Listed in the Alternate Systems Guidance.
• Experimental Systems.
• Proposed systems.
• Being tested.

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The Pennsylvania Protocol

• You either have
• A Conventional system its in Chapter 73.
• An Alternate system its in the alternate
  guidance.
• An Experimental system being tested.

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Conventional (Chapter 73) Systems

• Listed in Chapter 73.
• Maybe used if conditions fit.

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Conventional Beds Trenches

• Soil Conditions
• Limiting Zone ? 72 inches.
• Perc. Rate 6 to 90 min/in.

12 to 24 inch backfill
12 in aggregate
48 inches
?72 inches
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Shallow PlacedBeds Trenches

• Soil Conditions
• Limiting Zone ? 60 inches.
• Perc. Rate 6 to 90 min/in.

0 to 12 in above grade fill
0 to 12 in backfill
12 in aggregate
48 inches
?60 inches
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Elevated Sand Mound

• Soil Conditions
• Limiting Zone ? 60 inches ? 20 inches.
• Perc. Rate 3 to 120 min/in.

Top Berm
12 in aggregate
SAND
? 60 inches ? 20 inches
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Individual Residential Spray Irrigation System
(IRSIS)

• Soil Conditions
• Bedrock Limiting Zone gt 16 inches.
• Water Table Limiting Zone gt 10 inches.

gt 16 inches
gt 10 inches
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IRSIS Overall System(side view)

• Four Major Components

Treatment Tank
Chlorine Disinfection
Spray Area
Filtration
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IRSIS Spray Area
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The Alternate Systems

• As of February, 2007.
• Alternate Systems may be substituted for
  Conventional Systems.
• Alternate Systems are generally more costly than
  Conventional Systems.
• Alternate Systems require more maintenance than
  Conventional Systems.

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Filtration Units

• A biological filtration unit designed to
  breakdown carbon.
• Type of unit required is controlled by Limiting
  Zone soil conditions
• Placed after the treatment tank.
• Placed before the final disposal.

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Filtration Units Required

• Limiting Zone 48 inches
• No filtration required.
• Limiting Zone 20 to 48 inches
• Secondary Treatment Unit
• Aerobic Treatment Tank
• Free Access Sand Filter.
• Subsurface (Buried) Sand Filter.

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Filtration Units Required

• Limiting Zone
• 16 inches to Rock Limiting Zone, or
• 10 inches to Seasonal High Watertable
• Advanced Treatment Units
• Recirculating Subsurface Sand Filter.
• Free Access Sand Filter.
• Subsurface (Buried) Sand Filter.
• Peat Bio-Filter

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Aerobic Treatment Tank

• Replaces the Septic Tank.
• Is considered a Secondary Treatment Unit.

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Free Access Sand Filter

• Can be loaded by Gravity or Pressure Dosed.
• Secondary Treatment when
• Loaded at 5 gal/d/ft2 or less.
• Advanced Treatment when
• Loaded at 1.25 gal/d/ft2 or less.

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Free Access Sand Filter(Gravity or Pressure
Dosed)
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Subsurface (Buried) Sand Filter

• Must be loaded by pressure dosing.
• Secondary Treatment when
• Loaded at 0.8 gal/d/ft2 or less.
• Advanced Treatment when
• Loaded at 0.67 gal/d/ft2 or less.

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Subsurface (Buried) Sand Filter(Pressure Dosed)
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Recirculating Subsurface Media Filter

• 75 of filter effluent is recirculated back
  through the filter.
• 25 of filter effluent is sent on to next step in
  process.

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Recirculating Subsurface Media Filter
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Peat Filter
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Peat Filter
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Alternate Systems

• These systems have been evaluated and approved
  for use where conditions fit.
• Types of Alternate Systems
• At-Grade.
• Shallow Limiting Zone At-Grade.
• Drip Irrigation.

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At-Grade System

• gt 48 inches to LZ
• May use Option A or B
• No pre-treatment is required.
• 20 to 48 inches to LZ
• Requires Secondary Treatment
• May use Option A or B.

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At-Grade Bed System

• Aggregate placed on the soil surface.
• Perc Rate must be 3 to 180 min/in.
• Slope lt 12.
• Minimum 41 length to width ratio.
• Sized according to a Elevated Sand Mound.
• Must be pressure dosed.

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At-Grade System

• Two basic geometries
• Gravel parallel to land slope (Option A).
• Gravel level (Option B).

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At-Grade Bed System
10 in aggregate 6 in below pipes, 2 in above
pipes.
8 min. topsoil cover
1
6
6
3
Subsoil Berm
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Option A
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At-Grade Bed System
41 LW Ratio
2 to 5
Option A
3 wide subsoil berm
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Absorption Area Geometries

• Option A
• Aggregate is placed at a 10-inch uniform depth
  over chisel-plowed soil surface.
• Aggregate footprint must have at least a
  4(L)1(W) ratio across the slope.
• 3-foot wide subsoil berm must be placed on both
  ends and bottom of aggregate.
• Cover aggregate with separation layer.
• 8 to 10-inch depth of topsoil is placed over the
  aggregate and berm and planted with suitable
  plants.

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At-Grade Bed System
10 in min aggregate 6 in min below pipes, 2 in
min above pipes.
8 min. topsoil cover
2 to 5
6
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Option B
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At-Grade Bed System
41 LW Ratio
2 to 5
Option B
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Absorption Area Geometries

• Option B
• Aggregate is placed at a minimum 10-inch depth
  over chisel-plowed soil surface. Top of aggregate
  must be level.
• Aggregate footprint must have at least a
  4(L)1(W) ratio across the slope.
• Cover aggregate with separation layer.
• 8 to 10-inch depth of topsoil is placed over the
  aggregate and planted with suitable plants.

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Shallow LZ At-Grade System

• lt 20 inches to LZ.
• gt 16 inches to ROCK Limiting Zone.
• gt10 inches to WATER Limiting Zone
• Requires Advanced Treatment.
• Must use UV disinfection.
• Trench Absorption Area required.
• But when the depth to the Limiting Zone is 20
  inches or less, the system is assumed to dispose
  of the effluent differently.

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Shallow LZ At-Grade System
Must Use Trench Format
10 in aggregate Min
10 inch backfill

• 10 inches Water
• 16 inches Rock

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Shallow LZ At-Grade System

• Depth to Limiting Zone
• 16 inches to rock.
• 10 inches to seasonal high watertable.
• It is the UV disinfection that is added to make
  land disposal of effluent possible with these
  shallow depths to the limiting zone.

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Shallow LZ At-Grade System (Absorption)

• Principles of operation.
• Primary treatment in the septic tank.
• Advanced treatment required.
• Disinfected in the UV disinfection unit.
• Distributed to the soil surface via the At-Grade
  absorption system.
• B/c the soil is so shallow, the aerobic soil
  treatment occurs as the wastewater moves
  laterally down the slope parallel to the soil
  surface.
• Requires Assessment by a Soil Scientist.

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Drip System

• Soil scientist must classify the soils as well
  drained or moderately well drained.
• Slope 0 to 25.
• Watertable L.Z. greater than 20 inches.
• Rock L.Z. must be at least 20 inches below buried
  drip tubing.
• Drip tubes, spaced as close as 12 inches and
  buried up to 12 inches deep, replace the
  absorption field.

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Filtration Units Required

• Limiting Zone 48 inches
• No filtration required.
• Limiting Zone 20 to 48 inches
• Secondary Treatment Unit
• Aerobic Treatment Tank
• Free Access Sand Filter.
• Subsurface (Buried) Sand Filter.

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Drip System

• With Water Limiting Zone ? 20 inches.

? 20 inches
0 to 12 in deep 6 to 12 in of cover over the
tubing.
Emitters spaced 2 feet apart 0.68 gal/d/em
Maybe as small as 8 in
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Drip System

• With Rock Limiting Zone ? 20 inches.

? 20 inches
0 to 12 in deep 6 to 12 in of cover over the
tubing.
Emitters spaced 2 feet apart 0.68 gal/d/em
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Subsurface Sand Filter

• Soil Conditions
• Limiting Zone ? 72 inches.
• Perc. Rate (above 36 inches) ? 90 min/in.
• Perc. Rate (36 to 60 inches) ? 3 to 90 min/in.

12 to 24 inch backfill
12 in aggregate
SAND
Slow
Slow
? 12 inches
? 72 inches
? 60 inches
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Subsurface Sand FilterBeds Trenches

• Limiting Zone must be ? 72 inches.
• Used where a slowly permeable layer exists in
  normal effluent intake zone.
• Perc Rate 3 to 90 min/in in zone below the slowly
  permeable soil.
• Excavate slowly permeable soil and replace with
  at least 12 inches of mound sand (May only
  excavate to 60 inches).

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Modified Subsurface Sand Filter

• Site Design

12 to 24 inch backfill
12 in aggregate
SAND
Fast
Fast (Rock)
Good Soil
? 12 inches
? 72 inches
? 60 inches
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Modified Subsurface Sand Filter for Fast Perc
Rate, Shallow Bedrock, No Watertable.

• Instead of limiting the removal of slowly
  permeable soil to 3 feet, you can extend the
  removal of slowly permeable soil to 5 feet.
• At the deeper depths you may replace very fast
  soil material.

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Modified Subsurface Sand Filter

• Soil Conditions
• Limiting Zone ? 72 inches, but rock/gravel may be
  present in the 72 inches.
• Perc. Rate (above 36 inches) ? 3 min/in.
• Must be a 20-inch thick horizon the top of which
  must be between 36 and 60 inches that has
  sufficient fines to support an acceptable Perc.
  Rate of 3 to 90 min/in.
• Perc. Rate (between 36 and 60 inches) must be 3
  to 180 min/in.

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Modified Subsurface Sand Filter

• Maximum depth of excavation is 60 inches.
• Total depth od suitable soil and sand must be ?
  48 inches.
• At least 12 inches of sand must be used.
• Bottom of aggregate must be no more than 36
  inches from the soil surface.
• There must be a 4-foot perimeter of sand around
  the absorption area.

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Modified Subsurface Sand Filter

• Absorption area shall be 1.5 ft2/gpd if Perc.
  Rate is between 3 and 6 min/in.
• If Perc. Rate is slower than 6 min/in use the ESM
  guidelines.
• Trenches may not be used.

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Shallow Placement Pressure Dosed Systems

• Soil Conditions
• Limiting Zone ? 58 inches.
• Perc. Rate 6 to 90 min/in.

12 in above grade fill
10 in aggregate
48 inches
?58 inches
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Shallow Placement Pressure Dosed Systems

• For sites with a L.Z. ? 58inches.
• Bottom of aggregate maybe brought as close as 10
  inches to the land surface.
• Pressure Dosing is required.
• System must be installed on the contour.
• Must maintain 48-in separation between the
  aggregate-soil interface and the L.Z.

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Shallow Placement Pressure Dosed Systems

• Perc Test Modifications
• Initial Pre-soak conditions
• Fill to 10 inches (full).
• Let 2 inches soak into the soil.
• Add 2 additional inches (to make a total of 12
  inches).
• Finish as before.

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Steep-Slope Elevated Sand Mound

• Soil Conditions Slope 12 to 15
• Limiting Zone ? 20 inches.
• Perc. Rate 3 to 30 min/in.

Top Berm
12 in aggregate
? 10 ft
SAND
? 20 inches
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Steep Slope Elevated Sand Mound

• Maybe used on
• Slopes between 12 and 15
• Perc. Rates between 3 and 30 min/in.
• Must be 20 inches to L.Z.
• Like Regulated ESM except you must
• Daily flow ? 600 gpd flow.
• Limit bed width to 10 feet.

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Greenhouse System

• Low-flow plumbing fixtures.
• Aerobic treatment tank.
• Modified solar greenhouse beds.
• That evapotranspire all the effluent.
• No soil-based absorption area used.
• These systems are very expensive
• gt50,000

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Miscellaneous Systems System Components

• Leaching Chambers.
• Alternate Aggregate.
• Two-Chamber Septic Tank.
• Composting Toilet.
• Flow Equalization.
• Graywater System.

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Leaching Chambers

• Leaching Chambers are plastic domes installed in
  beds and trenches in place of aggregate.
• If used with a septic tank, you may reduce the
  size of the absorption area by 40.
• If used with an aerobic tank or composting
  toilets, no reduction permitted.

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Leaching Chambers
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Alternate Coarse Aggregate

• Type C coarse aggregate
• Tire-chip derived aggregate
• Maybe used as an alternative material in the
  construction of on-lot sewage absorption areas.

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Two-Chamber Septic Tank

• Chapter 73 states and implies round one-chamber
  septic tanks are permissible.
• Research at Del Val confirms that two-chamber,
  rectangular septic tanks are better.
• Therefore, all new installations and repairs must
  use two-chamber, rectangular septic tanks OR Two
  single-chamber septic tanks in series.

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Two-Chamber Septic Tank
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Alternate Individually Designed Composting Toilet

• This is a set of specifications on how to design
  and build a composting toilet.
• Has only been met by one company.

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Flow Equalization

• Tanks, controls and dosing equipment are used to
  equalize high peak flows.
• Collect and store sewage for later treatment.
• Most appropriate in State parks and other day-use
  facilities.

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Graywater Systems

• If you are willing to separate graywater from
  blackwater, then
• Use a non-flush toilet alternative to collect and
  treat the blackwater.
• You may reduce the size of the absorption field
  (used to dispose of the graywater) by 40.
• No reduction in septic tank size.

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QUESTIONS??