Section Env-Ws 382.10 - Monitoring for Chlorite(a) An owner of a community or non-transient noncommunity water system using chlorine dioxide for disinfection or for oxidation shall monitor for chlorite as follows:(1) At least one daily sample shall be collected at each entrance to the distribution system; and(2) For any daily sample that exceeds the chlorite MCL specified in Env-Ws 317.70, the system owner shall: a. Continue to collect at least one daily sample at each entrance to the distribution system as specified above; andb. Collect additional samples in the distribution system the following day at the following locations: 1. As close to the first customer nearest to the entry point to the distribution system as possible;2. In a location representative of average residence time in the distribution system; and3. As close to the end of the distribution system as possible, reflecting maximum residence time in the distribution system.(b) In addition to the daily sampling pursuant to (a) above, a system owner shall collect a 3-sample set once per month at each of the following locations in the distribution system: (1) As close to the first customer nearest to the entry point to the distribution system as possible at a location representative of average residence time;(2) At a location representative of average residence time in the distribution system; and(3) At a location reflecting maximum residence time in the distribution system.(c) Any additional routine monitoring conducted at the system owner's discretion shall be conducted as 3-sample sets as specified in (b) above.(d) A system owner may use the results of additional monitoring in (c) above to meet the monthly monitoring requirement in (b) above.(e) After one year of monthly sampling, a system owner may submit to the department a written request to reduce the chlorite monitoring frequency in (b) above.(f) The written request shall include: (2) The system EPA number; and(3) A summary of daily and monthly chlorite sampling results for the previous year.(g) The department shall respond to the request in writing and decrease the monthly monitoring requirement to one 3-sample set per quarter if the department determines that: (1) No individual chlorite sample collected in the distribution system under (b) above, has exceeded the chlorite MCL specified in Env-Ws 317.70; and(2) The system owner has not been required to conduct additional monitoring under (a)(2)above.(h) The system may remain on the reduced monitoring schedule unless: (1) Any of the 3 individual chlorite samples taken quarterly in the distribution system exceeds the chlorite MCL; or(2) The system owner is required to conduct monitoring under (a)(2)above, at which time the system owner shall revert to routine monitoring as specified in (a) and (b) above.(i) Additional routine monitoring conducted at the system owner's discretion shall be at the locations specified in (b) above.(j) A system owner may use the results of additional daily monitoring conducted pursuant to (i) above to meet the required monthly monitoring of (b) above.(k) Daily chlorite monitoring at the entrance to the distribution system as specified in this section shall not be reduced.N.H. Code Admin. R. Env-Ws 382.10
(See third Revision Note at chapter heading Env-Ws 300); #7735, eff 8-2-02