Hydraulic Model Studies of The Lake Avenue Control Structure Site 45

Abstract

The tunnel system for the Combined Sewer Overflow .Abatement Project (CSOAP) for the City of Rochester, New York, requires numerous control structures. Site 45 is the designated name and location of one such control structure. It is located on the west bank of the Genesee River and receives flow from the Lake Avenue Tunnel and the Tiger Carlisle Tunnel. The Site 45 control structure performs three functions. First, it contains a centrally located chamber which provides relief from waterhammer and surge pressures that will occur in the tunnels as a result of stormwater inflows. Second, if the inflow volume is great enough, the structure provides overflow relief by directing excess stormwater to two dropshafts which lead to the Genesee River below. Third, the structure controls the rate of flow through two parallel conduits which cross over to the east side of the Genesee River, and to additional structures located downstream, including the Frank E. Van Lare Sewage Treatment Plant. The control structure at Site 45 is designed to pass up to 375 cfs across the Genesee River to the Van Lare Treatment Plant. Flows greater than 375 cfs will exceed the capacity of the treatment plant and will be directed via the overflow relief to the Genesee River. The design maximum inflow to the Site 45 structure is 3000 cfs. Control of the rate of flow to the sewage treatment plant will be accomplished by means of control gates within the Site 45 structure. The gate openings will be set automatically to pass a given flow with a range· of head differences. These head differences are dependent on the water surface elevation in the surge chamber within the structure and the head required to establish a specific flow to the sewage treatment plant. A model of the Site 45 structure was built at the St. Anthony Falls Hydraulic Laboratory from drawings of the proposed structure supplied by Harza Engineering Company (Dwg. 1330 HYD 4500 RJ). Figures 1 and 2 show the plan and elevation of the structure obtained from these drawings. Photographs of the model are shown in Photos 1 and 2. The details of the specific parts of the model will be explained as the functions of the various components are discussed. Froude law scaling was used to establish dynamic similarity between the model and prototype, as gravity is the dominant force producing motion. The following expressions were used to convert the geometric, kinematic, and dynamic quantities from the model to the prototype.