Sewer sediment is one of major sources of pollutants in urban wet-weather flow (WWF) discharges that include combined-sewer overflow (CSO), separate sanitary-sewer overflow (SSO), and stormwater runoff. During low-flow, dry-weather periods, sanitary wastewater solids deposited in combined sewers have significant adverse impacts on the integrity of the sewerage system and receiving-water quality. In the US, estimates of dry-weather flow deposition in combined sewers vary from 5 to 30% of the daily inputs of solids and pollutants. In Europe, average deposition rates have been measured at between 30 and 500 g/m/d. Even sewers that are supposedly designed to be self-cleansing will have transient sediment deposits and part of the load in transport will move near the sewer invert. Deposited organic matter contains high concentrations of sulfates that can be reduced to hydrogen sulfide (H2S) under anoxic conditions often reached in a sewer. The H2S is then oxidized to sulfuric acid, a highly toxic and corrosive gas, by biochemical transformation. The concentration of Biochemical Oxygen Demand (BOD), Chemical Oxygen Demand (COD), and ammonia (NH-3N) in sewer sediments can be as high as 150,000 mg/L, 200,000 mg/L, and 300 mg/L, respectively. During a storm event, resuspended sediments are discharged directly into receiving waters. This report covers sources of sewer solids, sewer solids loading, sewer sediment and associated pollutants and their impacts, sewer cleaning, and in-sewer sediment control. For in-sewer sediment control, the report presents a number of in-sewer flushing systems with case studies.