Section Env-Dw 709.18 - Invalidation of Total Coliform Samples(a) A sample result that is positive for total coliforms or E. coli that is invalidated under this section shall not be used to meet the minimum monitoring requirements of this part.(b) The department shall invalidate a sample result that is positive for E. coli only if the laboratory establishes that improper sample analysis caused the positive result.(c) Subject to (d), below, the department shall invalidate a sample result that is positive for total coliforms only if: (1) The laboratory establishes that improper sample analysis caused the positive result;(2) The department, on the basis of the results of repeat samples collected as required by Env-Dw 709.15, and source water samples collected per Env-Dw 717, if required, determines that the positive sample resulted from a domestic or other non-distribution system plumbing problem, provided that all repeat samples collected at the same tap as the original positive sample are also positive for total coliforms, and all other repeat and source water samples are negative for total coliforms; or(3) The department has substantial grounds to believe that a positive total coliform result is due to a circumstance or condition that does not reflect water quality in the distribution system, provided the PWS owner collects all repeat samples required under Env-Dw 710.15 and uses them to determine whether a treatment trigger as specified in Env-Dw 709.22 has been exceeded.(d) The department shall not invalidate a total coliform-positive sample result on the basis of repeat samples if: (1) All of the repeat samples are negative for total coliforms;(2) Any source water sample collected pursuant to Env-Dw 717 is total coliform positive, unless the system provides continuous disinfection; or(3) The PWS has only one service connection.(e) If a sample is invalidated for the reason specified in (c)(1), above, the PWS owner shall collect another sample from the same sampling point as the original sample within the same monitoring period after being notified of the sample invalidation.(f) If the department invalidates a total coliform sample result for the reason specified in (c)(3), above, then: (1) The department shall document the rationale for the decision in writing and have the document approved and signed by the director of the department's division of water, or designee;(2) The written documentation shall state the specific cause of the positive sample, and what action(s) the PWS owner has taken or will take to correct the problem; and(3) The department shall make the document available to the EPA and the public.(g) A laboratory shall invalidate a total coliform sample result where total coliforms are not detected if the sample: (1) Produces turbid culture in the absence of gas production using an analytical method where gas formation is examined, such as the multiple-tube fermentation technique;(2) Produces turbid culture in the absence of an acid reaction in the presence-absence coliform test; or(3) Exhibits confluent growth or produces colonies too numerous to count with an analytical method using a membrane filter.(h) If a sample is invalidated for a reason specified in (g), above, the PWS owner shall: (1) Collect another sample from the same sampling point as the original sample within 24 hours of being notified of the sample invalidation;(2) Have the sample analyzed for the presence of total coliforms; and(3) Continue to resample within 24 hours and have the samples analyzed until a valid result is obtained.(i) The department shall extend the 24-hour limit established in (h), above, if the PWS owner is unable to collect the sample within 24 hours for reasons that are beyond the owner's control.N.H. Code Admin. R. Env-Dw 709.18
(See Revision Note #1 at chapter heading for Env-Dw 700) #9700, eff 5-1-10
Amended by Volume XXXV Number 06, Filed February 12, 2015 , Proposed by #10771, Effective 2/1/2015, Expires2/1/2025.