Managing reservoir sediments remains challenging due to their propensity to significantly sequestrate trace elements. Moreover, many artificial reservoirs were located downstream of former mining sites. However, the knowledge of the exact trace element speciation and its fate in sediments submitted to reoxidation and drying events, such as dredging operations, is still limited. In this study, we examined the degree of contamination and solid speciation of trace elements and radionuclides in case of lake sediments dredging influenced by former mining activities. Finally, to assess the consequences such management i.e., dredging, by mimicking drying and oxidizing conditions, Toxicity Characterizing Leaching Procedure (TCLP) tests combined with parallel chemical extractions and mineralogical analyses were performed. Our results showed enrichments for Cu, Sn and Bi related to the former extractions activities of Charrier Cu–Sn mining site, as well as an enrichment for U partially due to the Bois-Noirs-Limouzat U mining site, in lake sediments. Moreover, the reoxidation and drying of initially anoxic sediments led to metal solid speciation dominated by: (i) Cu and Bi inherited sulfide minerals such as chalcopyrite, (ii) Cu, Bi and U associated with natural organic matter, and (iii) large grain-size refractory cassiterite SnO2 crystals. Additionally, results from the TCLP indicated a limited leachability of the studied elements, confirming the significant stability of U, Cu and Bi associated with natural organic matter. Finally, Cu and U concentrations extracted by TCLP are lower than threshold values indicating that these sediments are not considered as hazardous regarding these elements.