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r ` Steven Sasson -S- February 5, 1996 indication of a maximum concentration of hydraulic fluid in the ground water that would not cause any adverse health effects should the hydraulic fluid migrate to ground water and should ground water be used for potable purposes (e.g , drinking) This is considered a conservative assessment because the ground water is not currently being used for potable purposes The equation in the PEA Guidance Manual (DTSC 1994) is actually used to calculate the hazard from a particular concentration of a chemical in ground water. However, using the USEPA/DTSC safe hazard level of 1, the equation can be solved for a safe concentration of hydraulic fluid in the ground water This is conducted using the following methodology- Hazard (water) = ((Cw I RfDo) x (0 0639)) + ((Cw I RfDi) x (0 063 9) + ((CwlRfDo) x 0 0644 x Kp)) Cw — Concentration in water, mg/hter RfD, = Oral reference dose, mg/kg-day (6 mg/kg-day) RfD, = Inhalation reference dose, mg/kg-day' (6 mg/kg-day) Kp — The chemical specific dermal permeability coefficient from water (3 2 x 10-1)4 If the hazard value is set equal to 1, the concentration of hydraulic fluid in water is calculated to be 50 mg/titer (or parts per mullion (ppm)) Therefore, using this extremely conservative assessment, the hydraulic fluid would need to be present at a concentration greater than 50 ppm to present any adverse health effects This is lughly unlikely for two reasons First, the source of the hydraulic fluid is no longer present, and second, hydraulic fluid is not soluble in water, rendering it highly unlikely to reach a concentration of 50 ppm 3.0 Conclusions FNVIRON's screening nsk assessment was performed to evaluate the potential for adverse health effects from residual hydraulic fluid in the soil under the Bridges Specialty Center. This assessment addressed dermal contact with soil and inhalation of vapors from soil The hazard index calculated was less than 1 Therefore, the presence of hydraulic fluid in the soil is not expected to present any adverse health effects Ground water monitoring results showed non-detectable levels of TPH Because a large majority of the hydraulic fluid has been remediated from the soil, the source for hydraulic fluid is no longer I 3 The oral reference dose was used for the inhalation reference dose This assumes equal absorption by the oral and inhalation routes 4 In the absence of a chemical-specific dermal permeability coefficient for hydraulic fluid, a dermal permeability coefficient for a similar hydrocarbon mixture was used