1. Each of the signatory states agrees, that in so far as waters within its jurisdiction may flow into any portion of the district, all sewage discharged or permitted to flow into any stream tributary to the tidal waters of the district shall be treated to that extent, if any, which may be necessary to maintain such tributary immediately above its confluence with the tidal waters of the district in a sanitary condition at least equal to the classification requirements determined by the commission for the tidal waters of the district into which it discharges. The waters of the Hudson river, immediately above the mouth of Sparkill creek on the westerly side and the New York-New Jersey boundary extended on the easterly side of the river, shall be maintained in a sanitary condition at ebb tide at least equal to the sanitary condition prevailing in the waters of the river immediately below said boundary at flood tide.