LDEQ

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LDEQs RECAP

• Domenico and Summers Models

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DOMENICO MODEL
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Domenico Model

• The Domenico groundwater model is used to
  calculate a dilution and attenuation factor (DF
  or DAF) associated with SoilGW2 , SoilGW3 , GW2 ,
  and GW3 values
• DF or DAF is the source concentration of a
  constituent divided by its down gradient
  concentration
• DF or DAF gt 1 If DF or DAF 1 then no dilution
  and/or attenuation

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MO-1 Domenico ModelSoilGW2 3 and GW2 3

• Default assumptions
• Equation accounts ONLY for dilution
• Plume is allowed to expand infinitely
• laterally in 2 directions
• vertically in 1 direction
• Planar plume size is based on
• Sw is 1/2 acre site - 148 ft by 148 ft
• Sd depths vary from 5 to 20 feet

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MO-1 Domenico Model

• Two pieces of data are needed to determine a DF
  from the table
• x - shortest downgradient distance from source to
  exposure point
• Sd - vertical depth of plume

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• Determination of Sd - vertical depth of plume
• METHOD 1
• Sd depth of plume at initial conditions
• Sd hadv hdisp
• advective flow dispersive flow
• Sd can not be greater than the aquifer thickness-B

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• METHOD 1 cont.
• Sd hadv hdisp
• hadv B1-exp((-IL)/(BDv)
• hdisp (2 ?zL)(0.5)
• B aquifer thickness 10 ft
• I infiltration rate 0.33 ft/yr
• L length of source 148 ft
• Dv groundwater transport velocity 30 ft/yr
• ?z vertical dispersivity L/200 148/200
• Sd 1.5 14.8 16.3 gt B Therefore, Sd 10
  ft

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Determination of Sd - vertical depth of plume
METHOD 2

• The thickness of the impacted permeable zone
  shall be used as the Sd if the thickness of
  groundwater plume is unknown

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• MO-1 DF Table
• Values given in tables in Appendix I
• X Sd
• lt5 6-10 11-15
  16-20
• 0-50 1.5 1 1 1
• 51-100 2.6 1.5 1.2 1.1
• 101-150 4.1 2.1 1.6 1.3
• 151-250 8.4 4.3 3 2.3
• 251-500 29 15 9.8 7.4
• 501-750 63 32 21 16
• 751-1000 111 57 37 28
• 1001-1250 173 86 58 43
• 1251-1500 248 124 83 62
• 1501-1750 337 169 113 84
• 1751-2000 440 220 147 110

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• MO-1 Domenico Model

• If Sd is greater than 20 feet then a
  site-specific DAF shall be calculated under MO-2
  or MO-3
• If the distance from the source is greater than
  2000 feet, then (1) the DF for 2000 feet may be
  used under MO-1 or (2) a site-specific DAF may
  be calculated under MO-2 or MO-3

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MO-2 Domenico Model

• Equation can account for dilution and attenuation
• Attenuation must be based on site-specific data
  (NO TEXT BOOK VALUES)
• Plume is allowed to expand infinitely in the 2
  lateral directions
• Plume vertical depth is limited to the aquifer
  thickness and must be accounted for in the
  equation

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• P. WJ1-1 2

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• MO-2 Domenico Model cont.
• If the POE is within the boundary of plume use
  given form of equation - Fig. J-1
• This means the x value, the distance from the
  source to the POE, is much less than the
  groundwater transport velocity multiplied by the
  time since the spill
• (x ltlt v t)
• If the POE is in front of plume x gt v t then
  equation must be modified and time t adjusted to
  account for maximum COC at point x (see model
  reference)
• This is a judgment call. Looking for maximum
  contaminant concentration at the point x.

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Summers Model
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SUMMERS MODEL

• The Summers model is used under MO-2 to calculate
  a site-specific dilution factor for a COC in soil
  water as it moves from the soil column into the
  adjacent groundwater (Appendix K)
• DFSummers chemical concentration in soil
  leachate divided by the chemical concentration in
  the adjacent groundwater Cl / Csi
• Under MO-1 a DF of 20 is used

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MO-2 Summers Model

• DAFSummers Cl / Csi (Qp Qa) / Qp
• (I Sw L Dv Sd Sw) / (I Sw L)
• (0.33148148 3010148) / (0.33148148) 7
• Qp volumetric flow of infiltration into aquifer
• I infiltration rate
• Sw width of impacted area perpendicular to GW
  flow direction
• L length of impacted area parallel to GW flow
  direction
• Qa volumetric flow rate of groundwater
• Dv darcy GW velocity
• Sd thickness of GW plume

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Estimation of Sd

• Sd Thickness of impacted groundwater within
  permeable zone

Sd 5
10
Un-impacted groundwater
Impacted groundwater
5
15
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Estimation of Sd

• Sd Thickness of permeable zone if thickness is
  not known or if the zone is not impacted

Sd 15
10
Un-impacted groundwater
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