Design-Build Services for the Improvements to the Existing Cogeneration Facility at the South District Wastewater Treatment Plant, MIAMI, FL
Miami-Dade County recently completed studies that indicated that methane gas produced by the neighboring landfill could provide up to 30% of the energy used at the South District Wastewater Treatment Plant (SDWWTP) through additional cogeneration, thus reducing the facility’s reliance on fossil fuel. Miami-Dade Water and Sewer Department (MDWASD) issued a Request for Design-Build Services to obtain proposals for the improvements
to the existing Cogeneration Facility.
The Poole & Kent Design-Build team met with MDWASD to review the technical approach and proposed value engineering for additional cost savings to the County. First, they updated the previously established design criteria and then developed the Preliminary Design Development Report to be utilized as the basis of design for the entire construction period. The team worked diligently to brainstorm cost saving ideas which were incorporated into the Design-Build Proposal. The ideas, benefitting the County from cost and planning perspectives, included:
- The use of an iron sponge digester gas conditioning system, resulting in a cost savings of $200,000.
- Installation of four cogeneration units in lieu of the two originally planned and the infrastructure for a future unit was installed under this project, simplifying the process of adding the fifth unit in the future.
- Integrating the new cogeneration units within the existing facility with minimal downtime. Several well thought out approaches, such as pre-fabrication of important piping components, significantly reduces the amount of facility downtime.
- Additionally, since the existing basement piping is extremely complex, a 3D modeling effort was undertaken during the preliminary design development phase, to help mitigate conflicts and effectively visualize inefficient piping arrangements.
SCOPE OF SERVICES
Poole & Kent reviewed the design criteria, provided beneficial value engineering ideas, and developed a Preliminary Design Development Report which would be the basis of our design through the construction period. The evaluation/selection process was two steps:
1) design-build team’s qualifications and experience; and 2) technical approach and price proposal. Additionally, the County required presentations from each proposer. The Poole & Kent team was not only determined to be the highest rank of proposing firms but additionally provided the lowest bid price for the work. The contract includes design, permitting, and construction of the following improvements:
- Four new Cummins cogeneration units with infrastructure for a fifth unit in the future
- Digester and landfill gas conditioning systems
- Hot oil heat recovery system, consisting of 11 pumps, expansion and overflow tanks, and insulated carbon steel pipe
- New hot water and supply system integrated with existing system
- New electrical room with new 480V MCC panels and 5kV arc flash resistant switchgear
- Engine room ventilation system, including eight large supply fans, ten large exhaust fans and 30-inch diameter duct work
- 100-ton non-electric absorption chiller
- Programming of controls
- On-site training of MDWASD Operating and Maintenance staff
- Digester Scrubbing System
- Siloxane Removal System
Poole & Kent is also responsible for permitting, designing, scheduling, coordination, procurement, and execution of all aspects of construction of the facilities and equipment.
Permitting for this project was a meticulous task. To expedite construction of the New Electrical Building, Poole & Kent submitted the plans to Miami-Dade County Building Department in two phases, the “shell” permit and “tenant improvements” permit. By breaking out the “shell”, the design team could finalize the process mechanical, electrical systems, and integration while enabling construction of the building to begin. Once the final design was complete, the second permitting phase began. Another innovative solution by Poole & Kent was during the installation of the 100-ton absorption chiller; P&K decided it would be best to invert the unit, hoist it through an opening in the newly constructed building, and carefully lower it by a crane through the hatch to the basement. This saved the client time and costly modifications.
The existing Cogeneration Facility was originally built in 1991 by Poole & Kent.