Section Env-Ws 381.03 - Lead and Copper Action Levels(a) The lead action level shall be exceeded if the concentration of lead in more than 10% of tap water samples collected during any monitoring period conducted in accordance with Env-Ws 381.15 through Env-Ws 381.21 is greater than 0.015 mg/L, that is, if the 90th percentile as computed in (c) below, is greater than 0.015 mg/L.(b) The copper action level shall be exceeded if the concentration of copper in more than 10% of tap water samples collected during any monitoring period conducted in accordance with Env-Ws 381.15 through Env-Ws 381.21 is greater than 1.3 mg/L, that is, if the 90th percentile as computed in (c) below, is greater than 1.3 mg/L.(c) The 90th percentile lead and copper levels shall be computed as follows: (1) The results of all lead or copper samples taken during a monitoring period shall be placed in ascending order from the sample with the lowest concentration to the sample with the highest concentration;(2) Each sample result shall be assigned a number ascending by single integers beginning with the number "one" for the sample with the lowest contaminant level;(3) The number assigned to the sample with the highest contaminant level shall be equal to the total number of samples taken;(4) The number of samples taken during the monitoring period shall be multiplied by 0.9;(5) The contaminant concentration in the numbered sample yielded by the calculation in (c) shall be the 90th percentile contaminant level; and(6) For water systems serving fewer than 100 people that collect 5 samples per monitoring period, the 90th percentile shall be computed by taking the average of the highest and second highest concentrations.N.H. Admin. Code § Env-Ws 381.03
(See Revision Note at chapter heading for Env-Ws 300) #6521, eff 6-4-97, ss by #7734, eff 8-2-02