Section 40.0983 - Derivation of Additional Method 1 Groundwater Standards for Use in Method 2If an MCP Method 1 Groundwater Standard has not been promulgated by the Department, the RP, PRP or Other Person may develop an MCP Method 2 Standard for that oil and/or hazardous material on the basis of the following assumptions and procedures:
(1) A site-specific background concentration in groundwater shall be identified for the oil and/or hazardous material.(2) GW-1 Standards shall be calculated as follows:(a) Based on non-cancer health risk, a concentration in drinking water of the oil and/or hazardous material associated with a Hazard Quotient (HQ) of 0.2 shall be identified using the following equation: [OHM]dw, non-cancer = HQ X RfD X BW X C/(IR X RAFdw-oral).
Where:
[OHM]dw, non-cancer = Concentration of oil and/or hazardous material consistent with a non-cancer Hazard Quotient of 0.2, in units of micrograms per liter (µg/L or ppb).
HQ = Hazard Quotient of 0.2 (dimensionless).
RfD = Reference Dose, in units of milligrams per kilogram-day (mg/(kg X d)).
BW = Body weight of 70 kilograms (kg).
C = Conversion factor of 1000 micrograms per milligram (µg/mg).
IR = Intake rate of 2 liters of water per day.
RAFdw-oral = Relative Absorption Factor for oral drinking water exposures (dimensionless).
(b) A concentration of the oil and/or hazardous material associated with an Excess Lifetime Cancer Risk equal to one-in-one million shall be identified using the following equation: [OHM]dw, cancer = ELCR X C x BW/(IR x RAF x CSF).
Where:
[OHM]dw, cancer = The concentration of oil and/or hazardous material in groundwater consistent with a cancer risk limit of one-in-one million, in units of micrograms per liter (µg/L or ppb).
ELCR = The Method 1 Excess Lifetime Cancer Risk limit of one-in-one million (10-6).
C = Conversion factor of 1000 micrograms per milligram (µg/mg).
BW = Body weight of 70 kilograms (kg).
IR = Intake rate of 2 liters of water per day.
RAFdw-oral = Relative Absorption Factor for oral drinking water exposures (dimensionless).
CSF = Cancer Slope Factor in units of risk per milligrams per kilogram-day (mg/(kg x day))-1.
(c) The concentration in water of the oil and/or hazardous material at which 50% of the population can detect its odor is identified, if available;(d) The lowest non-zero concentration estimated in 310 CMR 40.0983(2)(a), (b), and (c) is identified as the risk-based concentration for the oil and/or hazardous material of concern;(e) The site-specific groundwater background concentration identified for the oil and/or hazardous material in 310 CMR 40.0983(1) is considered;(f) The Practical Quantitation Limit (PQL) applicable to the oil and/or hazardous material using an appropriately sensitive analytical method for quantifying the concentration of the oil and/or hazardous material in water shall be identified; and(g) The highest of the three concentrations identified in 310 CMR 40.0983(2)(d), (e) and (f) is adopted as the MCP Method 2 GW-1 Standard for that oil and/or hazardous material.(3) GW-2 Standards shall be determined as follows:(a) A risk-based indoor air concentration shall be identified by choosing the lowest non-zero value from the following:1. Based on a non-cancer health risk, a concentration associated with a Hazard Quotient (HQ) of 0.2 is identified when sufficient information exists using the following equation: [OHM]air, non-cancer =HQ X RfC X C.
Where:
[OHM]air, non-cancer = The calculated indoor air concentration associated with 20% of the reference concentration, in units of micrograms per cubic meter (µg/m3).
HQ = Hazard Quotient of 0.2 (dimensionless).
RfC = Reference Concentration, in units of milligrams per cubic meter (mg/m3) at which adverse non-cancer health effects are unlikely to occur.
C = Conversion factor of 1000 micrograms per milligram (µg/mg).
2. An indoor air concentration associated with an Excess Lifetime Cancer Risk of one-in-one million, using the following equation, when sufficient information exists: [OHM]air-cancer = ELCR / URair.
Where:
[OHM]air = The calculated indoor air concentration in units of micrograms per cubic meter (µg/m3) associated with an Excess Lifetime Cancer Risk of one-in-one million (10-6).
ELCR = The Method 1 Excess Lifetime Cancer Risk limit of one-in-one million (10-6).
URair = The inhalation Unit Risk in air for the chemical, in units of risk per micrograms per cubic meter (µg/m3)-1.
3. The concentration in air of the oil and/or hazardous material at which 50% of the population can detect its odor is identified, if available.(b) A background indoor air concentration for the chemical shall be identified and compared to the risk-based concentration calculated in 310 CMR 40.0983(3)(a). The higher of the two values shall be chosen as the target indoor air concentration.(c) A source attenuation factor, a, shall be determined for the oil and/or hazardous material, assuming conservative site characteristics, including: a depth to groundwater of 213 cm (seven feet), a basement floor both 183 cm (six feet) below grade and 30 cm (one foot) above the groundwater table, a soil water-filled porosity equal to 0.06 cm3/cm3, and sandy-loam soil between the groundwater and the basement.(d) A concentration in groundwater for the oil and/or hazardous material shall be calculated using the following equation: [OHM]gw = [OHM]air / ([ALPHA] x H x C).
Where:
[OHM]gw = The calculated GW-2 Standard, in units of micrograms per liter (µg/L or ppb).
[OHM]air = The target indoor air concentration identified in 310 CMR 40.0983(3)(b), in units of micrograms per cubic meter (µg/m3).
[ALPHA] = A source attenuation factor as determined at 310 CMR 40.0983(3)(c) (dimensionless).
H = The Henry's Law Constant for the chemical (dimensionless).
C = Conversion factor of 1000 liters per cubic meter (L/m3).
(e) The site-specific groundwater background concentration shall be identified for the oil and/or hazardous material in 310 CMR 40.0983(1).(f) The Practical Quantitation Limit (PQL) applicable to the oil and/or hazardous material using an appropriately sensitive analytical method for quantifying the concentration of the oil and/or hazardous material in water shall be identified.(g) The highest of the three concentrations identified in 310 CMR 40.0983(2)(d), (e) and (f) shall be adopted as the MCP Method 2 GW-2 Standard for that oil and/or hazardous material.(4)GW-3 Standards shall be determined as follows: (a) The lowest ecologically-based Water Quality Criterion for the oil and/or hazardous material of concern shall be identified (i.e., the Fresh Water Chronic Criterion, the Fresh Water Acute Criterion, the Marine Chronic Criterion, or the Marine Acute Criterion). If no such criterion exists, an analogous value from the scientific literature may be proposed.(b) The concentration (in µg/liter, or ppb) identified in 310 CMR 40.0983(4)(a) shall be multiplied by a factor of ten.(c) The concentration identified in 310 CMR 40.0983(4)(b) shall be multiplied by:1. a factor of 2.5 if the Koc value for the oil or hazardous material of concern is less than 1,000;2. a factor of 25 if the Koc value for the oil or hazardous material of concern is greater than or equal to 1,000 but less than 100,000; or3. a factor of 100 if the Koc value for the oil or hazardous material of concern is greater than or equal to 100,000.(d) The resulting concentration (in µg/L, or ppb) shall be the MCP Method 2 GW-3 Standard for the oil and/or hazardous material of concern.(5) Any of the MCP Method 2 groundwater standards calculated in 310 CMR 40.0983(2) through (4) shall be adjusted to a ceiling concentration of 50,000 µg/liter (ppb) if the calculated value is greater than 50,000 µg/liter (ppb).Amended by Mass Register Issue 1503, eff. 3/1/2024.Amended by Mass Register Issue S1516, eff. 3/1/2024.