Design of Stilling Chamber for Qalag Sewage Lifting Station

Brief Description

Overall project objective was to design a stilling chamber inside the Qalag sewage lifting station to receive the flows arriving from the existing and future force mains and discharge to trunk sewers ultimately reaching the Gabal El Asfar main collection chamber. Detailed objectives included the following: 1) redirecting the flow from the 700 mm diameter force main of the Gamaa Lifting Station and the flow from the 710 mm diameter force main of the Tell El Wastani Lifting Station away from the wet well of the Phase II lifting station and into the proposed stilling chamber — their combined flow is estimated at approximately 100,000 m³/day — from which the flows are then conveyed to the collection chamber of the gravity trunk sewers feeding the Phase II Archimedes screw pumping station, thereby reducing the energy consumed by the Phase II screw pumps; 2) redirecting the route of the 1500 mm diameter Ain Shams force main — due to the emissions, gases, turbulence, and vortices it currently causes, since it discharges into the collection chamber at a level higher than the water level inside the Phase II collection chamber, with its flow estimated at approximately 300,000 m³/day — to instead connect it to the proposed stilling chamber; 3) adding wall stub-out connections to the proposed stilling chamber to allow for the future connection of five force mains with diameters of 800, 800, 750, 500, and 450 mm and combined flows of up to approximately 300,000 m³/day, since connecting them to the Phase II collection chamber is impractical due to insufficient space, and would also increase gas emissions.

T&I’s scope included collecting the drawings and data related to the Qalag Archimedes screw pumping station, the trunk sewers arriving to it from the Khosous Archimedes screw pumping station, and the trunk sewers leaving the Qalag station to the Gabal El Asfar treatment plant for both Phase I and Phase II, together with data on the existing force mains currently received at the wet well of the Qalag station; preparing a preliminary design for the construction of the stilling chamber together with a hydraulic analysis of the proposed stilling chamber options; finalizing the hydraulic design taking into account a cost and constructability evaluation of the connection-works alternatives to the existing main collection chamber; preparing the construction drawings for the proposed project; and preparing the technical specifications and remaining project documents.