Article 21 2.

For all agglomerations referred to in Article 5(1) and (3), Member States shall ensure that competent authorities, appropriate bodies or operators of the collecting system carry out representative monitoring, at relevant points, of storm water overflows into water bodies and of discharges of urban runoff from separate systems, in order to estimate the concentration and loads of the parameters listed in Table 1 of Annex I, and, where relevant, in Table 2, as well as the content of microplastics and relevant pollutants. Member States may use the results of that monitoring for the purposes of modelling where appropriate.