Groundwater Ingestion
ACarcinogenic COCBNon-carcinogenic COC
(1)Category I(1)Category I & II:
C = C =
(2)Category II(2)Category III:
C = C =
(3)Category III(3)Future groundwater ingestion
C = C =
(4)Future groundwater ingestion
C =
Groundwater Protective Soil ConcentrationSaturated Soil Concentration
C = C =
Health-Based Soil Concentration
AResident Soil Ingestion and Inhalation
VFr= where α =
PEF =
(1) Carcinogenic COC(2)Non-carcinogenic COC
C = C=
For COC with SFo and RfC (no URF) toxicity values (e.g., dichlorobenzene 1, 4), use the following equations:
Soil ingestion: Ccarc =Soil vapor inhalation: Cnc =
Total Combined C = =
BCommercial/Industrial Worker
VFi =(refer to resident soil ingestion/inhalation for α)
PEF – refer to resident soil ingestion and inhalation
(1) Carcinogenic COC(2) Non-carcinogenic COC
C =C =
For COC with SFo and RfC (no URF) toxicity values (e.g., dichlorobenzene 1,4), use the following equations:
Soil ingestion: Ccarc =Soil vapor inhalation: Cnc =
Total Combined C = =
Construction worker
A. Soil (ingestion and inhalation pathways)
VFconst = (refer to health-based soil for α)
PEFconst= = 9*108
(1) Carcinogenic COC(2) Non-carcinogenic COC
C = C =
For dichlorobenzene 1, 4 which has no URF, but RfC for the inhalation pathway, then
Soil ingestion: Ccarc =Soil vapor inhalation: Cnc =
Total Combined C = =
BGroundwater (inhalation and dermal contact pathways)
NOTE: The number C (calculated in (1)-(3) below) shall be divided by Cavg (calculated in (4) below) to obtain the target number.
If tevent.const<t*, Z = 2Kp;If tevet.const> t*, Z=Kp(
(1) Carcinogens
C =
(2) Non-carcinogens
C =
(3)For dichlorobenzene 1,4:
C =
(4)For all COCs, the equations for Cavg are:
a = + + + b = + +Cavg = [b*τ+( - 1)()]
Irrigation Well
Assumptions: Lawn watering duration and frequency are two hours every three days from March 1 to October 31, 82 events per year.
AResidential irrigationwell: located at residential properties. Three pathways are involved: groundwater ingestion, dermal contact, and
vapor inhalation
(a)Incidental ingestion
(1)Carcinogens(2)Non-carcinogens
Cing= Cing=
(b)Incidental dermal contact(as with soil ABSGI is only adjusted ifABSGI <0.5, otherwise set ABSGI=1, SFd = SFo and RfDd = RfDo)
(1)Carcinogens
DAevent.AgeAdj (mg/cm2-event)=
If tevent.AgeAdj< t*If tevent.AgeAdj > t* (all carcinogens’ tevent.AgeAdj are < t*, the equation does not apply)
Cderm=*CFwat Cderm=
(2)Non-carcinogens
DAevent.C=
Iftevent< t*Iftevent > t*(acetone, Formaldehyde, and methyl ethyl ketone)
Cderm =Cderm=
(c)Vapor inhalation on the lawn
Assumptions: A receptor is standing on the lawn for two hours per eventimmediately after watering.
DA(cm2/s) = andE (mg per cm2/s per mg/L in water)=
(1)Carcinogens(2)Non-carcinogens
CinhCinh
(d)Total Combined Concentration:
C (mg/L) =
(B)Commercial Irrigation well: located on commercial properties. Two pathways are involved: dermal contact and vapor inhalation.
(a) Ingestion - NA
(b)Incidental dermal contact
(1)Carcinogens
DAevent(mg/cm2-event) =
If tevent<=t*If tevent>t* (benzene only)
Cderm= Cderm =
(2)Non-carcinogens
DAevent(mg/cm2-event) =
Iftevent< t*:If tevent > t*:(acetone, Formaldehyde, and methyl ethyl ketone)
Cderm =Cderm=
(c) Inhalation
Assumptions – refer to resident pathway
(1)Carcinogens(2)Non-carcinogens
CinhCinh
(d)Total Combined Concentration:C (mg/L) =
ParametersDefinition units
A Absorption factor1 (refer to GW ingestion pathway)
AHBArea of contamination for residential or C/I properties1,500,000 cm2 for VFi or VFr
150 m2 for PEF
Aconst.soilArea of excavation floor and four walls1,087,000 cm2 for VFconst or
108.7 m2 for PEFconst
Aconst.waterArea of excavationfloor for construction worker22.3 m2
AIWArea of irrigation 9,000,000 cm2
ABSGIGastrointesinal absorption fraction COC-specific, (unitless)
ATcAveraging time for carcinogens 70 years
AT.CChild averaging time for carcinogens6 years
ATnAveraging time for non-carcinogens30 years
ATn-IIIAveraging time for non-carcinogens in Category III groundwater9/years
ATn.const-sAveraging time for soil to construction worker0.24 year
ATn.const-wAveraging time for groundwater to construction worker0.06 years
ATn.CChild averaging time for non-carcinogens6 years
ATnwWorker averaging time for non-carcinogens25 years
BRelative contribution of permeability coefficient(B=Kp)COC specific, cm/hour
BWAdult body weight70 kg
BW.CChild body weight15 kg
CCalculated concentrationmg/kg (soil) or mg/L (water)
CoInitial dissolved COC concentration1 mg/L
CavgAverage diossolvedCOc concentration over time τCOC-specific, mg/L
CcarcCalculated default concentration for carcinogenmg/kg (soil) or mg/L (water)
CcategoryPlan A default number for each groundwater categoryCOC-specific, mg/L
CncCalculated concentration for non-carcinogenmg/kg (soil) or mg/L (water)
CdermCalculated concentration for dermal contactmg/L
CinhCalculated concentration for vapor inhalationmg/L
CingCalculated concentration for groundwater ingestionmg/L
CwGroundwater concentration in irrigation well exposure1 mg/L
CFairConversion factor1000 ug/mg
CFuUnit conversion factor1000 g/kg
CFvVolume conversion factor1000 L/m3
CFwWeight conversion factor10-6 kg/mg
CFwatConversion factor1000 cm3/L
dDepth of water in the excavation pit1 m
dcmDepth of water in the excavation pit100 cm
deeffective diameter of excavation pit (de = ) 5.3285 m
DAApparent diffusivityCOC-specific, cm2/sec
DairDiffusion coefficient in air COC-specific, cm2/sec
DeiEffective diffusivity(Dei = Dair*θ0.33)COC-specific, cm2/sec
DwatDiffusion coefficient in waterCOC-specific, cm2/sec
DetherDiffusivity of ether in water8.5*10-6 cm2/s
DAevent.AgeAdjDermal absorbed dose per event for age adjust exposure mg/(cm2-event)
DAevent.CDermal absorbed dose per event for child exposuremg/(cm2-event)
DAeventDermal absorbed dose per event for C/I workermg/(cm2-event)
DHDiffusion height or air mixing zone height2 m
EEmission rateCOC-specific, (mg/cm2/sec per mg/L in water)
EDExposure duration30 years
EDIIIExposure duration for Category III groundwater9 years
ED.AgeAdjAge adjust exposure duration24 years
ED.CChild exposure duration6 years
EDwC/I worker exposure duration25 years
EDconst.sConstruction worker exposure duration (soil)12 weeks
EDconst.wConstruction worker exposure duration (water)3 weeks
EFExposure frequency350days/year
EFconstConstruction worker’s exposure frequency 5 days/week
EFIWIrrigation well exposure frequency82 days/year
EFIW-inhIrrigation well inhalation exposure frequency (2 hrs/ev for 82 ev/yr)6.83333 days/year
EFwWorker’s exposure frequency250 days/year
EVExposure event for groundwater to construction work2 events/day
EVIWExposure event for dermal contact with water from irrigation well1 event/day
FAChemical specific adsorbed, default conservatively set to 11 (unitless)
F(x)Function dependent on Um/Ut0.0497 (unitless)
GFraction of vegetative cover0
H’Dimensionless Henry’s Law ConstantCOC-specific (cm3-H2O/cm3-air)
HExcavation height2 m
HQHazard quotient1
iHydraulic gradient0.025 (unitless)
IFsoil.adjAge-adjusted soil ingestion rate114 (mg-year)/(kg-day)
IRaVapor inhalation rate for resident15 m3/day
IRa.wVapor inhalation rate for worker20 m3/day
IRIWIncidental ingestion rate of groundwater from irrigation well0.4 (L-year)/(kg-day)
IRIW.CChild incidental ingestion rate of groundwater from irrigation well0.32 (L-year)/(kg-day)
IRsConstruction work soil ingestion rate480 mg/day
IRsoil.CChild soil ingestion rate200 mg/day
IRswWorker soil ingestion rate100 mg/day
IRwDaily adult water ingestion rate2 liters/day
IRw-IIIDaily adult water ingestion rate for category III groundwater1.4 liters/day
KHydraulic conductivity1.7*10-4(cm/sec)
KasSoil-air partition coefficient (Kas= )COC-specific (g-soil/cm3-air)
KdSoil-water partition coefficient (kd = Koc*foc)COC-specific (cm3-H2O/g-soil)
KocSoil organic carbon-water partition coefficientCOC-specific (cm3-H2O/g-Carbon)
KpDermal permeability coefficient (LogKp=0.66LogKow-2.8-0.0056*MW)COC-specific, cm/hour
KowOctanol-water partition coefficient COC-specific (cm3-H2O/cm3-octanol)
KwsOverall mass transfer coefficientCOC –specific, m/s
Kws =
lCharacteristic length for diffusion30.48 cm
LLength or width of excavation 4.7 m
LSLength of contamination area21 m
MLEMost likely exposure (1.4 L/day*235 days/year*9 years)2961 Liters
MWMolecular weightCOC-specific, g/mole
PEFParticulate emission factor2.917*1010,m3/kg
PEFconstParticulate emission rate in construction work scenario9.0*108 m3/kg
RfCInhalation reference concentrationCOC-specific, mg/m3
RfDdDermal reference dose (RfDd = RfDo when ABSGI50%)COC-specific,mg(kg-day)
RfDiInhalation reference dose (RfDi= )COC-specific, mg/(kg-day)
RfDoOral reference doseCOC-specific, mg/(kg-day)
SPure compound solubility in waterCOC-specific, mg/L
SAAdult skin area18,000 cm2
SAconstConstruction worker skin area6170 cm2
SA.CChild skin area6,600 cm2
SFdDermal cancer slope factor (SFd = SFo when ABSGI >50%)COC-specific, mg/(kg-day)-1
SFiInhalation cancer slope factor(SFi=)COC-specific,mg/(kg-day))-1
SFoOral cancer slope factorCOC-specific,mg/(kg-day))-1
τExposure interval (3 weeks for groundwater to construction worker)1.8144*106 seconds
τeventLag time (τevent = 0.105*100.0056*MW)COC-specific, hour/event
tExposure interval for vapor inhalation after watering7200 seconds
teventExposure duration in irrigation well scenario0.73 hours/event
Assume sufficiently warm (>700F) for 60 of the 82 events and 1 hour
sprinkler play time (RME bathing time, USEPA RAGS Part E, 2001), (60*1)/82 = 0.73
tevent.AgeAdjExposure duration for resident contact with water from irrigation well0.48 hours/event
for age adjust, tevent.AgeAdj = = 0.48 hours/event
tevent.constExposure duration for construction worker2 hours/event
t*Time to reach steady-stateCOC-specific, hour
If B<= 0.6, t*= 2.4*
If B > 0.6, t* = 6**{[]-}
TResident soil vapor exposure interval9.4608*108 seconds
TC/IC/I worker soil vapor exposure interval7.844*108 seconds
TconstConstruction worker soil vapor exposure interval3.78432*108 seconds
TRLife time cancer risk for Category I groundwater10-6
TRII-IIILife time cancer risk for Category II and III groundwater10-5
TRIWLife time cancer risk for irrigation well10-5
TRfLife time cancer risk for future exposure10-4
VWind speed in mixing zone2.25 m/sec
VexcWind speed in the excavation pit0.225 m/sec
UgViscosity of air1.81*10-4 g/(cm*s)
UmMean annual wind speed4.5 m/sec
UtEquivalent threshold value of wind12.8 m/sec
URFInhalation unit risk factorCOC-specific, m3/ug
VFiSoil-to-air volatilization factor for C/I workerCOC-specific, m3/kg
VFrSoil-to-air volatilization factor for residentCOC-specific, m3/kg
VFconstSoil-to-air volatilization factor for construction workerCOC-specific, m3/kg
wWidth of excavation pit470 cm
WiwWidth of lawn30 m
ZDermal factorCOC-specific, cm/event
βDry soil bulk density1.7225 g/cm3
θTotal soil porosity0.35 (unitless)
θaVolumetric air content of soil0.22 (unitless)
θwVolumetric water content of soil0.13 (unitless)
θasVolumetric air content of top soil (lawn)0.1 (unitless)
θwsVolumetric water content of top soil immediately after irrigation0.4 (unitless)
θTTotal soil porosity of top soil (lawn)0.5 (unitless)
ρbDry soil bulk density for lawn soil1.67 g/cm3
ρgDensity of air1.2*10-3 g/cm3
ρsSoil particle density2.65 g/cm3
focFraction of organic carbon in soil0.002
foc.iwFraction of organic carbon in lawn soil0.02
Revised September 2, 2011