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LDEQ’s RECAP. Domenico and Summer’s Models. DOMENICO MODEL. Domenico Model. The Domenico groundwater model is used to calculate a dilution and attenuation factor (DF or DAF) associated with Soil GW2 , Soil GW3 , GW 2 , and GW 3 values

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Ldeq s recap

LDEQ’s RECAP

Domenico and Summer’s Models



DomenicoModel

  • 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 > 1If DF or DAF = 1 then no dilution and/or attenuation


Mo 1 domenico model soil gw2 3 and gw 2 3
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


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


  • 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


  • METHOD 1 cont.

  • Sd = hadv + hdisp

  • hadv = B[1-exp((-I*L)/(B*Dv)

  • hdisp = (2* z*L)(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 > B Therefore, Sd = 10 ft


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


  • MO-1 DF Table

  • Values given in tables in Appendix I

    • X Sd

      • <5 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


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


Mo 2 domenico model
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



  • 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 << v * t)

  • If the POE is in front of plume x > 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.



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


Mo 2 summers model
MO-2 Summers Model

  • DAFSummers = Cl / Csi = (Qp + Qa) / Qp

  • = (I * Sw * L + Dv * Sd* Sw) / (I * Sw * L)

  • = (0.33*148*148 + 30*10*148) / (0.33*148*148) = 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


Estimation of s d
Estimation of Sd

Sd = Thickness of impacted groundwater within permeable zone

Sd = 5’

10’

5’

Un-impacted groundwater

Impacted groundwater

15’


Estimation of s d1
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

15’


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