Geo Tech Parameter

8/11/2019 Geo Tech Parameter

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Geotechnical ParameterGeotechnical Parameter

DocumentationDocumentation

Hashim Mukhtar Hashim MukhtarEnvironmental SpecialistEnvironmental Specialist

Tanks SectionTanks Section


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ObjectiveObjective

To highlight the importance of accuratelyTo highlight the importance of accurately

determining and documenting sitedetermining and documenting site --specificspecificgeotechnical parameters during riskgeotechnical parameters during riskassessmentassessment


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Introduction: MRBCA risk assessment processIntroduction: MRBCA risk assessment process

1. Characterization of contamination1. Characterization of contamination

2. Geotechnical parameters2. Geotechnical parameters


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DeterminationDetermination ofof MRBCA geotechnicalMRBCA geotechnicalparametersparameters

(Sections 5.6 and 8.0)(Sections 5.6 and 8.0)

A. A. SiteSite --specific valuesspecific valuesB.B. Default values (Default values ( soil type dependantsoil type dependant ))C.C. Literature values (USGS)Literature values (USGS)D.D. Adjacent site values Adjacent site values


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The soil subsurfaceThe soil subsurface

Soil

particle

Water Air space

Adsorbedphase


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Vadose zone lithologyVadose zone lithology

Silty clay

Silty clay

Silty clay

Silty clay

Stiff clay

Silty clay

Fine sand

Coarse sand

One sample Many subsamples

Homogeneous soil Heterogeneous soil


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MRBCA geotechnical parametersMRBCA geotechnical parameters

11 -- Dry bulk densityDry bulk density22 -- Soil porositySoil porosity33 -- Volumetric water content (VWC)Volumetric water content (VWC)44 -- Fractional organic carbon contentFractional organic carbon content

(FOC)(FOC)


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Dry bulk density (g/cc)Dry bulk density (g/cc)

The dry weight (110 degrees C) of anThe dry weight (110 degrees C) of anundisturbedundisturbed soil sample divided by its fieldsoil sample divided by its field

volume (ASTM Method D2937volume (ASTM Method D2937 --94)94)

Dry bulk density is inversely related toDry bulk density is inversely related toporosity (high porosity/more friableporosity (high porosity/more friablesoil/less compacted/low bulk density)soil/less compacted/low bulk density)


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How to obtain dry bulk density?How to obtain dry bulk density?

1.1. Soil sampling:Soil sampling:

-- Collect soil samples using Shelby tubeCollect soil samples using Shelby tubeor thinor thin --walled sampler or equivalentwalled sampler or equivalentmethodmethod

-- Homogeneous soil: one sampleHomogeneous soil: one sample-- Heterogeneous soil: one soil sampleHeterogeneous soil: one soil sample

from each soil type (horizon)from each soil type (horizon) -- considerconsiderthe % of each soil type in the vadosethe % of each soil type in the vadosezonezone


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Dry bulk density (continued)Dry bulk density (continued)

2. Literature values:2. Literature values:-- USGSUSGS --CARES value (depth)CARES value (depth)

3. MRBCA default value (1.5)3. MRBCA default value (1.5)

Generally reasonable values are reportedGenerally reasonable values are reported(range of 1.0 to 2.0)*(range of 1.0 to 2.0)***California Department of Pesticide RegulationCalifornia Department of Pesticide Regulation


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Soil porosity (cc/ccSoil porosity (cc/cc --soil)soil)

The ratio of volume of voids in a soilThe ratio of volume of voids in a soilsample to the volume of the samplesample to the volume of the sample(ASTM Method D854)(ASTM Method D854)


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How to determine soil porosity?How to determine soil porosity?

We need to determine:We need to determine:-- dry bulk densitydry bulk density

-- specific gravityspecific gravityPorosity = 1Porosity = 1 dry bulk density/specificdry bulk density/specific

gravity or particle densitygravity or particle density

At MRBCA Tier 2 porosity for the vadose zone, capillary At MRBCA Tier 2 porosity for the vadose zone, capillaryfringe, & foundation or wall cracks are assumed identicalfringe, & foundation or wall cracks are assumed identical


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Specific gravity (ASTM D854)Specific gravity (ASTM D854)

The mass of solid matter in a givenThe mass of solid matter in a given

soil sample as compared to ansoil sample as compared to anequal volume of water equal volume of water


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Specific gravity values*Specific gravity values*

SoilSoil Specific gravitySpecific gravitySandSand 2.632.63 2.672.67

SiltSilt 2.652.65 2.72.7Clay & silty clayClay & silty clay 2.672.67 2.92.9Organic soilsOrganic soils


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Verification of soil porosity valueVerification of soil porosity value

-- Boring logs information/ soil type/MRBCABoring logs information/ soil type/MRBCAdefault values (0.38, 0.44)default values (0.38, 0.44)

-- Literature value of comparable lithologyLiterature value of comparable lithology

-- Adjacent site value of comparable lithology Adjacent site value of comparable lithology


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Soil porosity valuesSoil porosity values

MaterialMaterial USGSUSGS

Argonne Argonne

Nat. Lab.Nat. Lab.

TanksTanks

MRBCAMRBCA

SandSand 0.250.25 0.250.25 -- 0.500.50 0.380.38

SiltSilt NANA 0.350.35 -- 0.500.50 0.440.44

ClayClay 0.500.50 0.400.40 -- 0.700.70 0.440.44


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Volumetric water content (cc/cc)Volumetric water content (cc/cc)

The ratio of volume of water to the volumeThe ratio of volume of water to the volumeof soil (ASTM Method D2216of soil (ASTM Method D2216 --92)92)

-- VWC is used in modelsVWC is used in models-- Convert gravimetric value to volumetricConvert gravimetric value to volumetric

valuevalue

VWC = GWC x dry bulk density/density ofVWC = GWC x dry bulk density/density ofwater water


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How to determine volumetric water content?How to determine volumetric water content?

11 -- Collect multiple soil samples across the site atCollect multiple soil samples across the site atvarying depths and determine the water contentvarying depths and determine the water contentfrom each of the vadose zone lithologic unitsfrom each of the vadose zone lithologic units

22 -- Calculate average water content in lab reports forCalculate average water content in lab reports forsoil samples collected from the vadose zonesoil samples collected from the vadose zone

33 -- USGS valueUSGS value -- CARES (check depth)CARES (check depth)

44 -- MRBCA default value (determine soil type)MRBCA default value (determine soil type)


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General volumetric water contentGeneral volumetric water content

issuesissues

1.1. Volumetric water content higher thanVolumetric water content higher thanporosity?porosity?

2.2. High volumetric water content for sitesHigh volumetric water content for siteswith shallow depth to groundwaterwith shallow depth to groundwater ((3 to 53 to 5feetfeet SSTLs >effective saturated concentration forSSTLs >effective saturated concentration for

soil and groundwater)soil and groundwater)


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Fractional organic carbon contentFractional organic carbon content

(g(g --C/gC/g --soil)soil)

The weight of organic carbon in the soilThe weight of organic carbon in the soildivided by the weight of the soildivided by the weight of the soil


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How to determine fractional organicHow to determine fractional organic

carbon content?carbon content?

1.1. Collect soil samples from area of noCollect soil samples from area of nopetroleum impact (PIDpetroleum impact (PID --log)log)

Consideration of lithology: compositeConsideration of lithology: compositesamples from two or more boringssamples from two or more borings

2. USGS2. USGS --CARESCARES -- organic matter contentorganic matter content --correction factor correction factor


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Fractional organic carbon contentFractional organic carbon content

(continued)(continued)Vadose zone:Vadose zone:

Three subsamples from 3 feet depth to theThree subsamples from 3 feet depth to thetop of the water table (from 0 to 3 feet/soiltop of the water table (from 0 to 3 feet/soilzone/high OMC)zone/high OMC)

Saturated zone:Saturated zone:

two subsamples, one immediately below thetwo subsamples, one immediately below thetop of the saturated zone and one 3 feettop of the saturated zone and one 3 feetbelow the top of the groundwater tablebelow the top of the groundwater table


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Sensitivity illustrationsSensitivity illustrations

-- Assess Indoor inhalation of vapor Assess Indoor inhalation of vapor

exposure pathwayexposure pathway-- Use MRBCA software version 2.1 of 2005Use MRBCA software version 2.1 of 2005

-- Use soil type 1 default parametersUse soil type 1 default parameters-- Determine tier 2 siteDetermine tier 2 site --specific target levelsspecific target levels

for benzene for soil and groundwater for afor benzene for soil and groundwater for aresident and nonresidentresident and nonresident


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Effect of porosity on BenzeneEffect of porosity on Benzene

SSTLsSSTLs

0

2

4

6

8

10

12

14

16

18

20

0.2 0.25 0.3 0.35 0.4 0.45 0.5 0.55

POROSITY

B e n z e n e

S S T L s

Resident so il

Resident GW

Nonr esident soil

Nonresident GW

Porosity VAC0.35 0.27

0.38 0.30

0.40 0.32

0.44 0.36

0.50 0.42

VWC = 0.08FOC = 0.006


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Effect of VWC on Benzene SSTLSEffect of VWC on Benzene SSTLS

0

500

1000

1500

2000

2500

0.08 0.09 0.1 0.15 0.17 0.19 0.2 0.25 0.3 0.35Volumetr ic Water Content

B e n z e n e

S S T L s

Resident soil

Resident GW

Nonresident soil

Nonresident GW

VWC VAC0.08 0.300.10 0.280.17 0.210.20 0.180.25 0.130.30 0.080.35 0.05

P = 0.38FOC = 0.006


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Effect of FOC on Benzene SSTLsEffect of FOC on Benzene SSTLs

0

1

2

3

4

5

6

7

0.003 0.004 0.005 0.006 0.007 0.008 0.009 0.01 0.02 0.03 0.04Fractional Organic Carbon

B e n z e n e

S S T L s

Resident soil

Resident GW

Nonresident soil

Nonresident GW

OMC* FOC

Soil (1,340) 0.02 0.01Subsoil (1,220) 0.008 0.005MRBCA 0.006

*Journal of the American Chemistry Society

P = 0.38VWC = 0.08


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SummarySummary

Collect soil samples for geotechnical parametersCollect soil samples for geotechnical parametersaccording to the guidance proceduresaccording to the guidance procedures

Collect soil samples from all soil horizons atCollect soil samples from all soil horizons atsites where the soil profile is heterogeneoussites where the soil profile is heterogeneous

Submit laboratory reports and calculationsSubmit laboratory reports and calculations

Submit boring logs with PID resultsSubmit boring logs with PID results

Support results with literature or comparable siteSupport results with literature or comparable sitevaluesvalues


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QUESTIONS?QUESTIONS?

COMMENTS?COMMENTS?

Geotechnical parametersGeotechnical parameters

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