Provides guidance to municipalities for investigating non-stormwater entries into storm drainage systems. These entries may originate from many diverse sources including sanitary wastewaters from leaky or directly connected sanitary sewerage and from poorly operating septic tank systems, washwaters for laundries and vehicle service facilities, and many types of industrial wastewaters that are discharged to drains leading to storm drainage or from direct industrial wastewater connections to the storm drainage system. 28 charts, tables and graphs.