2012 Determination of RRVs for DEQ-7

What is an RRV? “The RRV (Required Reporting Value) is the detection level that must be achieved in reporting surface water or ground water monitoring or compliance data to the Department unless otherwise specified in a permit, approval or authorization issued by the Department.”

Rules for RRVs 1) The method must be qualified as being an EPA approved 40CFR136 methodology or another method approved by the Department. 2) Regional labs supply the minimum detection limits (MDLs) for each procedure they use to test for a pollutant. These are then used used in the calculation of RRVs: 3) The 75 th percentile of the MDL’s from all reporting labs will be multiplied by 3.18 to calculate an RRV, in accordance with EPA 821-B (Revised Assessment of Detection and Quantitation Approaches).

Rules for RRVs (continued) 4)If one or more of the calculated RRVs is below the most restrictive numeric standard, the calculated RRV closest to 10% of the standard will be used as the RRV in DEQ-7.

Example-Ethylbenzene Ethylbenzene is an aromatic hydrocarbon found in gasoline, and is found in the groundwater in Montana at hundreds of leaking underground storage tank sites.

RRV Calculation for Ethylbenzene HHS in surface water = 530 µg/L 10% = 53 µg/L We choose the RRV closest to 53 µg/L, which is 0.7 µg/L. MethodRRV E µg/L E µg/L E µg/L

Rules for RRVs (continued) 5) If all calculated RRVs for a pollutant are larger than the most restrictive numeric standard, minimum reporting limits (MRLs) or practical reporting limits (PRLs) reported by the labs will be considered in lieu of a calculated RRV. If an MRL or PRL is closer or below the standard, that value will be used as the RRV in DEQ-7. If not, the calculated RRV closest to the standard will be the RRV in DEQ- 7.

Example-Mercury Historic gold mining is a large source of mercury contamination in Montana.

RRV Calculation for Mercury HHS in surface water = 0.05 µg/L 10% = µg/L All of the calculated RRVs were above the standard. We found that one lab reported a MRL of for method is 10% of the standard, so in this case, the MRL will be used as the RRV in DEQ-7. MethodRRVMRL/PRL µg/L0.01 µg/L µg/L0.005 µg/L µg/LNot Reported µg/L0.01 µg/L

Rules for RRVs (continued) 6) If no labs in the survey report MDLs for a given compound, the existing RRV remains or is replaced with a value equal to 10% of the most protective standard listed for the compound.

Example-Ammonium Sulfamate Ammonium sulfamate is an herbicide.

RRV Calculation for Ammonium Sulfamate HHS for ammonium sulfamate is 2,000 µg/L 10% is 200 µg/L No lab reported an MDL for ammonium sulfamate so the RRV in DEQ-7 will be 10% of the most restrictive numeric standard, which is 200 µg/L