Water Quality Analysis, Sampling, and Reporting
Water Quality Analysis, Sampling, and Reporting covers the defensibility of data: sample siting, collection, preservation, holding time, chain of custody, laboratory QA/QC, and reporting to NHDES and the public.
Rules
Bacteriological samples under the Revised Total Coliform Rule follow a written sample siting plan; routine samples are collected at designated sites, and a positive total coliform triggers repeat samples and, at a threshold, an assessment. E. coli positives are an MCL violation. Lead and copper compliance is based on the 90th percentile of first-draw samples at high-risk sites; action levels are 0.015 mg/L Pb and 1.3 mg/L Cu. Disinfection byproducts use locational running annual averages: TTHM 80 µg/L and HAA5 60 µg/L. Nitrate MCL is 10 mg/L as N; nitrite is 1 mg/L.
Preservation and holding time matter: chlorine residual is measured in the field; nitrate can be acid-preserved and chilled; bacteriological bottles are sterile, sodium thiosulfate-treated, and held cold. QA/QC includes blanks, duplicates, spikes, calibration, and MDL verification.
Worked example
Five lead samples: 0.004, 0.006, 0.009, 0.014, 0.021 mg/L. For five samples the 90th percentile is the average of the two highest: (0.014 + 0.021) ÷ 2 = 0.0175 mg/L, above the 0.015 action level, so the system exceeds and must conduct public education and corrosion-control steps.
Traps
Averaging all five samples, reporting non-detects as zero, missing holding time, sampling at a softened kitchen tap, and forgetting that a discharge monitoring report is a legal document.