When factory-built pumping and pressure control equipment is a significant portion of project scope, design-build contracting is an important option. Engineers, owners and developers have gained a high degree of confidence in the specialized engineering, design and fabrication skills of EFI. The company has been asked to participate on the project team for a broad range of design-build projects, and the outcomes have been better project control, decreased time to completion, higher quality and a reduction in total project cost.
In 2005, Bowling Green Kentucky Municipal Utilities (BGMU) solicited proposals for the replacement of their Red, White & Blue Booster Pumping Station. The station, more than 90 years old, was obsolete, worn out and undersized for current demand.
With the involvement of EFI and its representative, Delaney & Associates, BGMU saw wisdom in approaching the project as a design-build collaboration. The new booster pumping station was to be the major portion of the project. BGMU sent out solicitations stipulating the station manufacturer as the project lead holding ultimate and single source responsibility for the overall project performance.
Foundation contractor employees work on the simple station foundation. Site disturbance had to be minimal.
One reason for choosing design-build was that the station mechanical and electrical design was to be a cooperative effort between BGMU engineering personnel and their EFI counterparts. The outcome was a cost-efficient design conforming to a tight budget. EFI selected quality components and subsystems capable of being delivered quickly to meet a short delivery and installation schedule.
Site design peripheral to the station was handled by BGMU. The owner's responsibility was to set the performance standard; EFI's responsibility was to meet that standard–a simple path to success.
The BGMU project involved furnishing all materials, labor, tools, equipment and excavation for the completion of the new installation. EFI designed, delivered and constructed the above-ground booster pumping station; concrete foundation/pad; site electrical power service for the booster pumping station; controls; software; telemetry interface as required; and site piping to connect the booster pumping station inlet, outlet and drain connections to existing site piping.
The new pumping station is capable of delivering the fluid medium at the following capacities and heads when operating at 0-ft minimum suction pressure: a design 2,500 gal per minute (gpm) at 185 ft total discharge head (TDH); a maximum 3,300 gpm at 130 ft TDH; and an 87% efficiency at design point gpm.
The new EFI station, shown here, kept the same character as the old station and was finished on time and on budget.
Pump control valves
All project valves are solenoid controlled. The main valve is hydraulically operated by means of a double-chambered diaphragm actuator. It has a wide Y-pattern body with low lead losses and high cavitation resistance. Two pressure chambers are separated and sealed from one another by means of a flexible, nylon-fabric-reinforced neoprene rubber diaphragm.
The control valves lend themselves to conversion from one function (i.e., pressure relief, pump control) to another by changing the control pilots and the control loop. No changes need to be made in the internal valve structure.
The valves are capable of withstanding working pressures up to 175 psi and a testing pressure of 400 psi. The pump and valve controls are synchronized in a way that guarantees pump startup and shutoff while a valve is closed.
The internal mechanical and plumbing system for the two 125-horsepower end suction centrifugal pumps is shown here. The building supports a 2,000-lb capacity bridge crane that can be used for servicing the pumps and valves.
In essence, design-build is a team approach to construction. The owner develops a clearly written document of specified outcome–cost and performance. Then the owner selects a project team made up of design engineers, contractors, managers and major equipment/system suppliers. The team, in active cooperation, defines how to meet the owner's required outcome and at what cost. The team moves the project to completion, and the owner judges if the intended outcome has been met.
More and more state governing and funding agencies for municipal water and wastewater are turning to the advantages of design-build and allowing this approach to project development. The active cooperation aspect breaks down the enmity and conflicts that can occur at the interfaces caused by the bid process. It reduces overall project time, as the process is no longer a serial activity. Furthermore, costs are more controllable because optimum constructability is factored in from the beginning of the design stage, and risk is spread more equitably.