Investigation of Dry‐Weather Pollutant Entries into Storm‐Drainage Systems

Abstract

This article describes the results of a series of research tasks to develop a procedure to investigate non‐storm‐water (dry‐weather) entries into storm‐drainage systems (Pitt et al. 1993a, 1993b). Dry‐weather flows discharging from storm‐drainage systems contribute significant pollutant loadings to receiving waters, and although they can originate from many sources, the most significant include sanitary wastewater, industrial‐ and commercial‐pollutant entries, failing septic‐tank systems, and vehicle‐maintenance activities. Protocols are discussed to characterize the drainage area, locate and identify polluted outfalls, estimate the magnitudes of non‐storm‐water entries, and locate and correct the non‐storm‐water entries into the storm‐drainage system. If these loadings are ignored (e.g., by only considering wet‐weather storm‐water runoff), only limited improvement in receiving‐water conditions may occur with storm‐water pollution‐control programs.