66. At least 3 times a year, in the spring, summer and fall, the operator of an engineered landfill must take or have a groundwater sample taken at each sampling point of the observation wells installed pursuant to section 65, and have the samples analyzed to monitor the parameters or substances listed in section 57 and compliance with section 58, and to measure the following indicative parameters or substances:
(1) electrical conductivity;
(2) phenolic compounds;
(3) 5-day biochemical oxygen demand (BOD5);
(4) chemical oxygen demand (COD);
During sampling, the groundwater piezometric level must also be measured.
After a minimum 2-year monitoring period, the samples taken need no longer be analyzed for the parameters or substances whose concentration measured in the leachate before treatment, if any, has consistently been lower than the limit values listed in section 57, except in the case of indicative parameters or substances. The reduction in the number of parameters or substances to be analyzed applies as long as the annual analyses of leachate, before treatment, show that that condition is met. In addition, the analysis for 2 of the 3 required annual samplings may pertain only to the indicative parameters or substances listed in the first paragraph.
The Minister may establish a different list of indicative parameters or substances according to the composition of the residual materials received for disposal, in which case the parameters or substances may be in addition to or in substitution for the parameters or substances listed above.
Despite the foregoing, as soon as the analysis of a sample shows significant fluctuation for a parameter or substance or that a limit value has been exceeded, all the subsequent samples taken at the sampling point concerned must undergo a comprehensive analysis of the parameters or substances listed in section 57 until the situation is remedied.