He, JianmingSong, Charles C. S.2011-08-162011-08-162002-01https://hdl.handle.net/11299/113150Numerical studies of hydraulic transients for the Phase I Mainstream system of the Tunnel and Reservoir Plan (TARP) were conducted in 1988 [1] and 1992 [2]. These studies revealed that due to storage and/or conveyance limitation of the TARP Phase I Mainstream system, flow must be substantially reduced to avoid geysering problems induced b'y hydraulic transients. Later in 1994 [3], hydraulic transient studies of the preliminary design of Mainstream & Des Plaines TARP Phase II systems were also conducted under various tunnel operation conditions. It was found that a reservoir at the downstream end does little help to reduce the transient problem in the Mainstream system due to the conveyance limitation during the simulated storm event. The main objective of this study is to investigate the hydraulic event which occurred in the TRAP system on June 1, 1999, resulting in flooding of the Dewatering Valve Chambers at the Mainstream Pumping Station, and damage to. the. mechanical and electrical equipment therein. The study uses District operation data, reports and findings, photographs of the damage, rain data, as-built facility plans, and all other available, applicable information to characterize the event. In addition to identifying the underlying causes of the event, the study is also to investigate the methods of operation of the Mainstream and Des Plaines T ARP tunnel systems, separately and in combination, to optimize CSO pollution capture while avoiding adverse hydraulic transient phenomena such as tunnel geysering, severe pressure surges, etc. in T ARP facilities. The study is also to identify possible additional and/or revised control features of the TARP system necessary to achieve the aforementioned optimum operation.en-USReport