A laboratory operated by a waste discharge facility licensed pursuant to Title 38, section 413 may analyze waste discharges for total suspended solids, settleable solids, biological or biochemical oxygen demand, chemical oxygen demand, pH, chlorine residual, fecal coliform, E. coli, enterococcus, conductivity, color, temperature and dissolved oxygen without being certified under this section. The exception provided under this paragraph applies to a laboratory testing its own samples for pollutants listed in its permit or license; pretreatment samples; and samples from other wastewater treatment plants for up to 60 days per year. The time period provided in this paragraph, which is a maximum period for each treatment plant for which analysis is provided, may be extended by memorandum of agreement between the Department of Environmental Protection and the Health and Environmental Testing Laboratory.