40 CFR § 265.92 - Sampling and analysis.
(a) The owner or operator must obtain and analyze samples from the installed ground-water monitoring system. The owner or operator must develop and follow a ground-water sampling and analysis plan. He must keep this plan at the facility. The plan must include procedures and techniques for:
(1) Sample collection;
(2) Sample preservation and shipment;
(3) Analytical procedures; and
(4) Chain of custody control.
(b) The owner or operator must determine the concentration or value of the following parameters in ground-water samples in accordance with paragraphs (c) and (d) of this section:
(1) Parameters characterizing the suitability of the ground water as a drinking water supply, as specified in appendix III.
(2) Parameters establishing ground-water quality:
(3) Parameters used as indicators of ground-water contamination:
(ii) Specific Conductance
(iii) Total Organic Carbon
(iv) Total Organic Halogen
(1) For all monitoring wells, the owner or operator must establish initial background concentrations or values of all parameters specified in paragraph (b) of this section. He must do this quarterly for one year.
(2) For each of the indicator parameters specified in paragraph (b)(3) of this section, at least four replicate measurements must be obtained for each sample and the initial background arithmetic mean and variance must be determined by pooling the replicate measurements for the respective parameter concentrations or values in samples obtained from upgradient wells during the first year.
(d) After the first year, all monitoring wells must be sampled and the samples analyzed with the following frequencies:
(1) Samples collected to establish ground-water quality must be obtained and analyzed for the parameters specified in paragraph (b)(2) of this section at least annually.
(2) Samples collected to indicate ground-water contamination must be obtained and analyzed for the parameters specified in paragraph (b)(3) of this section at least semi-annually.
(e) Elevation of the ground-water surface at each monitoring well must be determined each time a sample is obtained.