CITY OF TALLAHASSEE
CITY COMMISSION AGENDA ITEM
ACTION REQUESTED ON: June 24, 2009
SUBJECT/TITLE: Approve Purdom Unit 8 – Zero Discharge Filter Cake Conveyor Project Reprogramming
TARGET ISSUE:
STATEMENT OF ISSUE
Purdom Unit 8 (PP8) is a 230 MW combined cycle generating unit located at the City’s Purdom Generating Station in St. Marks, Florida. PP8 is equipped with a zero discharge (ZD) water treatment system, which eliminates the discharge of process water from the site during normal operations. Operation of the ZD produces a filter cake that must be collected and disposed of off-site at an appropriately licensed facility. The filter cake consists of the solids and minerals that are in the make up water that is utilized at the plant and it has a high salt content. The Electric Utility included a project to install a conveyor system to handle this filter cake in the FY2009 Capital Improvement Program. The Utility is now recommending that the scope of this project be changed. This agenda item is seeking City Commission approval to modify the scope of the project.
RECOMMENDED ACTION
Option 1: Approve reprogramming Project #0101251 to include the purchase of roll off equipment, replacement vapor compressor, and filter press repair/replacement in lieu of the conveyor system.
FISCAL IMPACT
Option 1: None at this time.
Approval of this scope change will result in a cost savings to the City.
Kevin G. Wailes, General Manager – Electric Utility
Anita Favors Thompson, City Manager
For information, please contact: Rob McGarrah, Manager Power Production, x 5534
SUPPLEMENTAL MATERIAL/ISSUE ANALYSIS
HISTORY/FACTS & ISSUES
1. Purdom Unit 8 (PP8) is a 230 MW combined cycle generating unit located at the City’s Purdom Generating Station in St. Marks Florida. PP8 is equipped with a zero discharge (ZD) water treatment system, which eliminates the discharge of process water from the site during normal operations. The ZD must be in operation for PP8 to operate reliably.
2. The ZD is equipped with an evaporator, vapor compressor, crystallizer, and filter press. The ZD produces two by-products. The first is distilled water that is utilized for process and cooling tower make-up water, and the second is a filter cake. The filter cake consists of the solids and minerals that are in the “make-up” water that is utilized at the plant. Also it has a high salt content. This filter cake is currently collected in a roll off dumpster and transported to the Thomas County Landfill by the City’s Solid Waste Utility.
3. The dumpsters utilized in the collection of the filter press must be moved periodically during normal operations. Historically, the Purdom facility has utilized a Solid Waste “roll-off” truck that has been removed from normal service (i.e., retired) to move the dumpsters on site. While this has worked relatively well since PP8 went into commercial operation, the filter cake is highly corrosive due to the high salt content, and the retired trucks only last 2-3 years. As of this date, the current “roll-off” truck in service at Purdom is nearing the end of its useful life, and Fleet does not have any additional retired “roll-off” trucks for use at Purdom.
4. Project #0101251 – Purdom Zero Discharge Conveyor System was included in the Electric Utility FY2009 Capital Improvement Program. The scope of this project was to design, purchase, and install a conveyor system under the ZD filter press to move the filter cake to dumpsters without having to move the dumpsters. The total budget for this project was $2,000,000.
5. As the Purdom staff has moved forward with the details of this project, it has become apparent that the conveyor system will not be the most cost effective alternative to meet the Plant’s operational needs. After further investigation, staff has identified that: (i) installation of the conveyor system will not eliminate the need to move dumpsters around on the plant site during periods when Solid Waste is not on site; and (ii) the maintenance cost for the conveyor system will likely be more significant than originally anticipated.
6. Staff reviewed other alternatives available to address the long-term operational needs at the plant. Based on this review, staff is recommending that the conveyor system not be pursued at this time. In lieu of the conveyor system, a new roll off piece of equipment will need to be purchased and utilized on the site. The new roll off equipment may include specialty coatings to reduce the impacts from the filter cake corrosion.
7. Subsequent to budget approval, staff has identified additional ZD spare/replacement part needs. As a result, staff is requesting that the scope for Project 0101251 be modified to address the following two additional ZD issues.
a. The City owns two ZD vapor compressors. One is in operation and one is a spare. These compressors are operated at a high speed (7,500 RPM) and are comprised of a motor, gearbox, and compressor. They are an integral part of the ZD operations. Recently, the vapor compressor in operation failed catastrophically. This is the second vapor compressor in nine years of operation that has failed catastrophically. Staff is reviewing replacement options. These options include: replacement with a like vapor compressor, replacement with a different manufacturer vapor compressor, or replacement with multiple smaller vapor compressors. Staff is requesting that the project scope be modified to allow for the replacement once the most cost effective option is identified.
b. The City owns two ZD filter presses. One is in operation and one is a spare. The concept was that the operating filter press would be removed from service and replaced with the spare to allow for the operating filter press to be overhauled on a straight time basis (without use of overtime or expedited services). Staff recently removed one filter press from operation and installed the spare filter press. Staff has obtained an overhaul quote from the filter press original equipment manufacturer. This overhaul quote is approximately 60% of the cost of a replacement filter press. Staff is reviewing the repair/replacement options at this time. Staff is requesting that the project scope be modified to allow for the repair/replacement once the most cost effective option is identified.
8. Failure to have an operational spare for the vapor compressor and filter press exposes the City to reliability issues with Unit 8 should there be another failure of the operating vapor compressor and filter press. This is due to the requirement that PP8 have the ZD in operation for the unit to operate. Delivery of a like kind replacement vapor compressor is approximately 52 weeks.
9. Staff is seeking approval of the scope changes outlined above. Once the scope change is approved, Electric will work with Fleet to purchase the new roll off equipment and bring the filter press and vapor compressor approvals through the standard approval process.
10. Budget and Policy has reviewed this agenda item and concur that it meets budget guidelines.
CHARITABLE CONTRIBUTIONS
Not Applicable
OPTIONS
Option 1: Approve reprogramming Project #0101251 to include the purchase of roll off equipment, replacement vapor compressor, and filter press repair/replacement in lieu of the conveyor system.
Option 2: Approve the scope change for Project #0101251 to include only the purchase of the roll off equipment. Direct staff to bring a future budget item for approval for the vapor compressor and filter press issues.
Option 3: Do not approve the scope change and provide staff with additional direction.
FISCAL IMPACT
Option 1: None at this time.
Approval of this scope change will result in a cost savings to the City.
Option 2: None at this time.
This option is not recommended. The failure to address the vapor compressor and filter press issues will result in an increased reliability risk. Should the existing vapor compressor or filter press fail, Purdom Unit 8 will not be able to operate to meet the City’s customer needs.
Option 3: Unquantifiable until direction is received.
This option is not recommended.