Soils_ Infiltration_ and On-site

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					                        Applications to Stormwater

        Presented by:

 Mr. Brian Oram, PG, PASEO
       Wilkes University
GeoEnvironmental Sciences and
 Environmental Engineering
   Wilkes - Barre, PA 18766
       Nearly 50% of Soil is Space or
         Space Filled with Water
    • Water – 25+ %
    • Air – 25 + %
    • Pore Space Makes Up
      35 to 55 % of the
      total Soil Volume
    • This Space is called
      Pore Space
Therefore, soil can be used as a storage
system, treatment system, and transport
         Soil Properties Critical To
         Stormwater Management
•   Soil Texture
•   Porosity and Pore Size
•   Water Holding Capacity
•   Bulk Density
•   Aggregate Stability
•   Infiltration Capacity
•   Hydraulic Conductivity
             !!! Just to Name a Few Properties !!!!
                  Types of Pores

   Macropores (> 1,000 microns)-Large
       Mesopores (10 to 1,000 microns)- Medium
             Micropores (< 10 microns)- Small

         Key Points on Soil Pores
Under gravity, water drains from macropores, where as,
water is retained in mesopores and micropores, via matrix
Coarse-textured horizons (e.g., sandy loam) tend to have a
greater proportion of macropores than micropores- but they
may not have more macropores than finer textured soils.
Soils with water stable aggregates tend to have a
higher percentage of macropores than micropores.

Proportion of micropores tends to increase with soil depth,
resulting in greater retention of water and slower flow of
water with depth.
       Water Holding Capacity
                         Available Water Capacity
Textural Class            (Inches/Foot of Depth)
Coarse sand                       0.25–0.75
Fine sand                         0.75–1.00
Loamy sand                        1.10–1.20
Sandy loam                        1.25–1.40

Fine sandy loam                   1.50–2.00
Silt loam                         2.00–2.50
Silty clay loam                   1.80–2.00
Silty clay                        1.50–1.70
Clay                              1.20–1.50

  Please Do Not Use Sand in a Bio-Retention System !
    Bulk Density, Porosity, and Texture
  Textural Class       Bulk Density (Mg/m³)            (%)
        Sand                     1.55                   42
    Sandy loam                    1.4                   48
 Fine sandy loam                  1.3                   51
        Loam                      1.2                   55
     Silt loam                   1.15                   56
     Clay loam                    1.1                   59
        Clay                     1.05                   60
 Aggregated clay                   1                    62

Sands – Tend to have higher bulk density and lower permeability
Please do not use sands in Bio-Retention systems!
  How can a
  silt loam have
  than sand?       Answer: More Water Stable Structures

Brady, Nyle,
C. “ The
Nature and
Properties of
Soils” (1990).

Source: Brady,
Nyle, C. “ The
Nature and
Properties of
Soils” (1990).
         Water Stable Aggregates I
Aggregates on left are
more water stable, i.e.,
aggregate stays
together and do not
separate into the its
components, i.e., three
soil separates.

         Water Stable Aggregates
           Water Stable Aggregates – II
               The Classic Photo

Source: Brady, Nyle, C. “ The Nature and Properties of Soils” (1990)
Great Desk Reference Text !!!!
Permeability                  Inches
   Class        Ksat Class   per hour        Material

                                          Massive, Rock,
Impermeable      Very Low    <0.001417        Fragipan
                             0.001417     Massive, Rock,
                                to            Fragipan,
 Very Slow         Low        <0.0147          clayey
Very Slow to                  0.01417
  Moderately    Moderately      to       clay, silty clay,
     Slow            Low      <0.1417         clay loams
 Moderately                   0.1417     silt, silt loam,
    Slow to     Moderately       to          loam, fine
   Moderate         High      < 1.417        sandy loam

Moderate to                  1.417 to      loamy sand to
    Rapid          High        < 14.17       medium sand

                                           coarse sand,
   Rapid        Very High     > 14.17          gravel

             General Guide – To Ksat and Material
                 Hydrologic Soil Terms
•Infiltration - The downward entry of water into the immediate
surface of soil or other materials.
•Infiltration Flux (or Rate)- The volume of water that penetrates the
surface of the soil and expressed in cm/hr, mm/hr, or inches/hr. The rate
of infiltration is limited by the capacity of the soil and rate at which
water is applied to the surface. It is a volume flux of water flowing
into the profile per unit of soil surface area (expressed as velocity).

•Infiltration Capacity (fc)- The amount of water per unit area of time
that water can enter a soil under a given set of conditions at steady state.

•Cumulative infiltration: Total volume of water infiltrated per unit area
of soil surface during a specified time period.
    Horton Equation, Philip Equation, Green- Ampt Equation
Infiltration Rate
   Infiltration Rate (Time Dependent)

                                                  Steady Gravity
                                                  Induced Rate

  Infiltration with Time Initially    Final Infiltration Capacity
High Because of a Combination of      (Equilibrium)- Infiltration
 Capillary and Gravity Forces        Approaches q - Flux Density
      f = fc +(fo-fc) e^-kt
      fc does not equal K
               Infiltration Rate
             Decreases with Time
1) Changes in Surface and
Subsurface Conditions

2) Change in Matrix
Potential and Increase in Soil
Water Content and Decrease
in Hydraulic Gradient

3) Overtime - Matrix
Potential Decreases and       4) Reaches a steady-state condition
Gravity Forces                fc – final infiltration rate
Dominate - Causing a
Reduction in the Infiltration
            Infiltration Rate
      Function of Slope & Texture

Source: Rainbird Corporation, derived from USDA Data (Oram,2004)
               Infiltration Rate
            Function of Vegetation

Source: Gray, D., “Principles of Hydrology”, 1973.
               Infiltration Rate
   Function of Horizon A, B, Btx, Bt, C, R
    C/R Testing - Areas Fractured Rock

Source: On-site Infiltration Testing - Mr. Brian Oram, PG (2003) and
FX. Browne, Inc. (Lansdale, PA)
        (Compaction/ Moisture Level)

Site Compaction – Can Significantly Reduce Surface Infiltration Rate
       Rain Drop Impact Bare Soil

Destroys Soil Aggregates
Disperses Soil Separates
Seals Pore Space
Aids in Loss of Organic Material
Creates a Surface Crust
                          Source: (D. PAYNE, unpublished)
Percolation Rate
               Percolation Rate
Percolation -Downward Movement of Water
through the soil by gravity. (minutes per inch) at a
hydraulic gradient of 1 or less.
Used and Developed for Sizing Small Flow On-lot
Wastewater Disposal Systems.
On-lot Disposal Regulations (Act 537) has preliminary
Loading equations, but for large systems regulations
typically require permeability testing.
Also none as the Perc Test, Soak-Away Test (UK)

Not Directly Correlated to
or a Component of Unsaturated or
Saturated Flow Equations
                     Comparison Infiltration to Percolation Testing
                4          Infiltraton Test
               3.5                                                         Percolation
                3                                                         Testing Over
                           Percolation Test
Rate (in/hr)

                2                                                        Rate by 40% to
               1.5                                                        over 1000% *
                       1      2     3     4   5     6   7   8   9   10
                Source: On-site Soils Testing Data, (Oram, B., 2003)
Hydraulic Conductivity
           Darcys Law- Saturated Flow
              Vertical or Horizontal
Volume of discharge rate Q is proportional to the head
difference dH and to the cross-sectional area A of the column,
but it is inversely proportional to the distance dL of the flow path and
coefficient K is called the hydraulic conductivity of the soil.

The average flux can be obtained by dividing Q with A.
This flux is often called Darcy flux qw .
             Flux Density or Hydraulic
                Conductivity (Ksp)
Flux Density (q): The volume of water
passing through the soil per unit cross-
sectional area per unit of time.
It has units of length per unit time such as mm/sec,
mm/hour, or inches/ day (q = -K(ΔH/L ))
Actually the term is volume/area/time= q = Q/At

Hydraulic Conductivity (Ksp) quantitative measure
of a saturated soil's ability to transmit water
when subjected to a hydraulic gradient. It can be
thought of as the ease with which pores of a
saturated soil permit water movement .

                                            Side by Side (Pagoda, J, 2004)
Testing Methods
     Goals of the Field Method
• Field Measurement of the Flux Density
  (qw) and calculate hydraulic conductivity –
   qw = Ksp (dh/dl)

• Field Measurement of Hydraulic
  Conductivity (Ksp)
     Single Rings Infiltrometers

Cylinder - 30 cm in Diameter- Smaller Rings Available.

Drive 5 cm or more into Soil Surface or Horizon.

Water is Ponded Above the Surface- Typically < 6 inches.

Record Volume of Water Added with Time to Maintain a
Constant Head.

Measures a Combination of Horizontal and Vertical Flow
           ASTM Double Rings Infiltrometers

Outer Rings are 6 to 24 inches in Diameter (ASTM - 12 to 24 inches)
Mariotte Bottles Can be Used to Maintain Constant Head
Rings Driven - 5 cm to 6 inches in the Soil and if necessary sealed

  Very Difficult to Install and Seal – ASTM Double Rings in NEPA
      Potential Leaking Areas

Significant Effort is Needed to Install and Seal Units

       ASTM requires documentation of the
           Depth of the Wetting Front
Other Double Rings Small Diameter

6” and 12” Double Ring   3” and 5” Double Ring
                         in Flooded Pit
Infiltration Data- Double Ring Test

     Note: Ring Diameter – 26 cm (Oram 2005)
                           Cumulative Infiltration
Infiltration Rate –cm/hr

                             Steady-State Rate (slope)
                             0.403 cm/hr

                           Fc = Ultimate Infiltration
                           Capacity (approx.0.47 cm/hr)
         Estimated Methods- Based
               on Grain Size
                                               C- Factor
Hazen Method                    Very Fine        40 - 80
Applicability: sandy           Sand, poorly
  sediments                      Sorted
• K = Cd10 2                  Fine Sand with     40 - 80
• d10 is the grain diameter   Medium Sand,      80 - 120
  for which 10% of
  distribution is finer,       Well Sorted
  "effective grain size" -    Coarse Sand,      80 - 120
  where D10 is between 0.1    Poorly Sorted
  and 0.3 cm
                              Coarse sand,      120 - 150
• C is a factor that              well
  depends on grain size       Sorted, clean
  and sorting
           Guelph and Amoozegar
           Borehole Permeameters

                             $ 1500

Field Testing (Oram, 2000)   Photo Source:
       Measuring Hydraulic Conductivity
                                     12-inch/ 6-inch Double Ring

 Constant or Falling Head Permeameter- Homemade - $ 15.00
Side by Side Testing Mr. Brian Oram and Mr. Chris Watkins, 2003.
               Constant Head
           Borehole Permeameters

  Talsma Permeameter-
  Could be Homemade
  $ 50.00
  Retail ($ 300.00)

                                        Modified Amoozegar-
                                        Could be Homemade –
                                        $30.00- Retail ($ 200.00)

Side by Side Testing by Mr. Brian Oram and Mr. John Pagoda, 2004
             Measuring Infiltration Rate
      to Estimate / Calculate the Flux Density

• Infiltrometers- Yes !
   – Single ring- May Not Be Advisable – Multiple tests required
   – Double ring- Yes ! - May be difficult in rocky and stony areas
   (i.e., Most of the Poconos !)
   – Smaller Double Ring in Flood Pit – Yes !

• Flooded Infiltrometers – Yes !

• Adoption of a Strict Double Ring ASTM Method – Likely not
  appropriate, but method should be used as a guide by professionals.

• Cased Borehole Permeability Test – ASTM Method– Yes !
   (Minimum diameter casing 4 inches) with bentonite packing of annular
  space – Maximum Pipe Height is a function of soil conditions.
My Recommendation and Opinion !
     Please Do NOT Use a
 Conventional Percolation Rate or
 Percolation Test for Developing
      Engineering Design !
                 Percolation Testing
• Does not directly measure permeability or a flux velocity.

• Has been used to successfully design small flow on-lot wastewater
  disposal systems, but equations and designs have a number of safe

• Results may need to be adjusted to take out an estimate of the
  amount of horizontal intake area.

• Without Correction Percolation Data over-estimated infiltration
  rate data by 40 to over 1000 % with an adjustment for intake area
  error could be reduced to 10 to 200% (Oram, 2003) , but
  infiltration rate can overestimate saturated permeability by a
  factor of 10 or more (Oram, 2005).

• May need to consider the use of larger safety factors and equations
  similar to sizing equations used for on-lot disposal systems. Safety
  factors of 50% reduction may not be enough !!
    • Borehole Permeability Testing can be a Suitable

    • Falling Head , Constant Head, and Quasi Constant
S     Head Methods would be suitable.
M   • Permeability Data for Specific Site should be calculated
M     using Geometric Average.
    • Equations and Methods Based on Darcy’s Law and the
R     result is a value for Ksp or qw.
    • Do not recommend estimating permeability based on
      particle size distribution – Ok for preliminary desktop
      evaluations if data is available – Not for Final Design !

    • Laboratory permeability testing is possible, but it may
      be difficult to get a representative sample and account
      for induced changes. May be Ok for Preliminary
What NOW ?
    The Hydrologic Cycle
Discharge Zone               Recharge Zone

           Where is the Project Site ?
       Save Your Client – Money
      None Structural Development Practices

• Maintain Soil Quality and Maximize the Use of
  Current Grading to Minimize Loss of O, A, and
  upper B horizons.

• Minimize Compaction, Maximize Native
  Vegetation, and Use Good Construction Practices

• Consider Hydrological Setting and Existing
  Hydrological Features in Site Design and Layout

 Answer: New Development/ Construction Practices and
 New and Updated Ordinances and Planning Documents !
          Infiltration System Approach
        Individual Infiltration BMP Units
                                          Soil: Tunkhannock Series
                                          Soil had stratified sand
                                          and gravel lenses
                                          Water Table > 8 feet
                                          Open Voids
                                           (Gravel and Cobbles)
                                          3 to 6 feet
                                          Ksp Field Measured
                                          1 to 10+ inches per hour
                                          Reported Permeability
                                          > 6 inches per hour
        Design Used a Ksp of 0.5 inch per hour (50% reduction)
Note- A few sections of the site had permeability of 0.1 inch per hour
Infiltration Unit Configuration


      Sump and Grass Swale Prior to Unit
      and Geotextile within unit to capture large organic material

      Concrete – Open bottom perforated tank not filled with
      gravel for storage.

                   Conceptual Design by:
                   Malcolm Pirnie (Scranton, PA) and Brian Oram
                   (October 2004), Anticipated Installation 2007.
     Sizing Calculations- Areas 0.5 in/hr
• Impervious Area Roof and Driveway– 3500 ft2
• Design Storm – 1.3 inch
• Volume of Water to Recharge- 2840 gallons (379 ft3)

• Design Loading- Based on Field Measured Soil Permeability-
  0.5 inch per hour or 0.5 in3/in2.hour = 7.481 gpd/ft2

• Minimum Recharge Period – 72 hours (PADEP Recommended)

• Recharge Volume per day – 945 gpd

• Minimum Recharge Area- (945 / 7.481) =126 ft2

• Internal Tank Storage – 3 ft * 8 ft perforated Concrete Tank, plus 3+ foot
  perimeter and subsurface aggregate storage to generate a minimum surface
  area of 150 ft2.

• Additional Gravel Layer was added to Meet System Storage Requirement.
               Primary Limiting Factor is Not Recharge Capacity
           but Providing Detention Storage or Storage in the System !
      Sizing Calculations- Areas 0.1 in/hr
•   Impervious Area Roof and Driveway– 3500 ft2
•   Design Storm – 1.3 inch
•   Volume of Water to Recharge- 2840 gallons (379 ft3)

•   Design Loading- Based on Field Measured Soil Permeability-     0.1 inch per hour or
    0.1 in3/in2.hour =1.49 gpd/ft2

•   Minimum Recharge Period – 72 hours (PADEP Recommended)

•   Recharge Volume per day –945 gpd

•   Minimum Recharge Area- (945 / 1.49) =634 ft2 (over 18 % of impervious)

•   Recommended Changing the Recharge Period to 7 days to Reduce Infiltration Area
    to 270 ft2, but providing a system with 100 % detention storage. (7 % of impervious)

•   This could not be approved and the project implemented a bioretention/ recharge

      Primary Limiting Factor is Area Requirement Caused by Recharge Period
               and not Recharge Capacity or Storage in the System !
            Bio-Retention Systems

Image Source:
                  Bio-Retention Concept

                                 Sump and Grass Swale Prior to Unit and a By-pass Berm
                                 Structure for large runoff events.

                               System has a controlled discharge that maintains a
                               discharge elevation that this consistent with natural water
                               table conditions.
                               Vegetation – Native Seed Mix
                               Soil Media – Native Soil from Site Modified to either a
                               loam texture with 2 to 5 % organic material; covered with
                               compost/mulch layer (on-site source).
                               Washed Stone at the Base of the Unit.
                               Sizing based on detention storage requirements and flow
Conceptual Design by: Malcolm Pirnie (Scranton, PA) and Brian Oram (2004)
       Evaluating Recharge Capacity

•Step 1: Desktop Assessment - GIS

Review Published Data Related to Soils, Geology, Hydrology

•Step 2: Characterize the Hydrological Setting

•Where are the Discharge and Recharge Zones?
•What forms of Natural Infiltration or Depression
Storage Occurs?
•How does the site currently manage runoff ?
•What are the existing conditions or existing
    Evaluation Recharge Capacity
 •Step 3: On-Site Assessment
 Deep Soil Testing Throughout Site Based on Soils and Geological

 Double Ring Infiltration Testing or Permeability Testing to
 calculate qw and provide estimate of loading rates?

 How does the water move through the site ?

•Step 4: Engineering Review and Evaluation
(meet with local reviewers and PADEP)
•Step 5: Additional On-site Testing

•Step 6: Final Design and Final BMP Selection
      How Can We
        Use Site
      Conditons ?

Surface Boulders Created       3 feet Surface
Natural Depression Storage     Boulders
Areas that appeared to range
in width from 5 to 25 feet.
Natural Depression
Storage System –
New Potential BMP !
         Use Of Manufactured Soils
Manufactured soils are loosely defined as soil amendment
products comprised of treated residuals and various industrial
by-products, such as foundry sand and coal ash.
•Use of Organic By-Products – Compost – Organic Soil and
• Recycling of Industrial By-Products and Wood Products
•Improving Quality Structural Stability and Nutrient Content of
Unconsolidated Materials with Poor Soil Quality
• Use of Fly Ash, Incineration Ash, Recycling Remediated
Soil/Unconsolidated Material, Spent Foundry Sands
• Use of Soil Conditioners
• Use of Dredge Materials and Sediment
     I did not say these were off the shelf or easy options !
     Artificial Soil Quality Improvement
     Aggregate Stability- Using a Polymer

No Soil Conditioner   Less Soil Conditioner
                           Source: Brady, N. C., 1990
       Interested – Get Involved
          and Stay Informed?
• Stormwater Manual Oversight Committee
  Website – Keywords in Google: (stormwater
  committee PA- 1st Site)
• Meets at the Rachel Carson Building – First
  Floor Conference Room
• Next Meetings April 25, 2006, May 23, 2006,
  and June 27, 2006.
• Download- Current Manuals, Discussions, and
  Meeting Minutes
     Soils, Groundwater Recharge,
          and On-site Testing
           Presented by:

     Mr. Brian Oram, PG, PASEO
           Wilkes University
   GeoEnvironmental Sciences and
Environmental Engineering Department
      Wilkes - Barre, PA 18766
                                PADEP in the Field
Darcy Equation- What is Delta H?

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