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Home My WebLink About1979-01-02; City Council; 5444-2; EWPCF Phase III ModificationW CITY OF CARLSBAD AGENDA BILL NO. *S<*/*/tf- ^J^^a^/^^e^ **<£ ' Dept Hd> DATE: _ January 2, 1979 _ C. Atty . DEPARTMENT: Public Works C* Subject: ~~ ENCINA WATER POLLUTION CONTROL FACILITY - PHASE III MODIFICATION Statement of the Matter Following the Joint Advisory Committee (JAC) meeting of December 20th, the JAC Design Review Committee met to review the latest progress report con- cerning the secondary treatment processes included in Phase III. The latest findings of the design engineer indicate that the use of biof i 1 tration, as proposed to date, is only very slightly more expensive than the use of ac- tivated sludge while activated sludge gives a more flexibly system and a higher quality effluent. The summary of that meeting, as well as the cost analyses and pros and cons of each type of secondary treatment, are attached. It was the recommendation of the Design Review Committee that the project be modified to use activated sludge rather than biof i 1 tration. To do this would require a modification of the existing design contract with Brown & Caldwell. In order to keep the project on its time schedule, it has been suggested that Brown & Caldwell proceed with elements of the design not affected by this change while we are going through the administrative steps of modifying the contract. It is suggested that each agency act to acknowledge the necessary change by the passage of a minute motion authorizing the General Manager of the End na facility to act on our behalf. Exhibit Report from Encina General Manager dated December 21, 1978 Recommendation That City Council authorize the Encina General Manager to direct Brown & Caldwell to proceed only with those tasks in the approved design contract which would not be affected by a change in the treatment process from biofi1tration to activated sludge. Agenda Bill No. 5444 - Supplement #2 Page 2 Council action: 1-2-79 Council authorized the Encina General Manager to direct Brown & Caldwell to proceed only with those tasks in the approved design contract which would not be affected by a change in the treatment process from biofi1tration to activated sludge. ENCINA JOINT POWERS 6200 Avenida Encinas • Carlsbad, California 92008 Telephone (714) 438-3941 December 21, 1978 Mr. Ron Beckman City of Carlsbad 1200 Elm Avenue Carlsbad, CA 92008 Re: Agreement between Vista Sanitation District and Brown and Caldwell for Engineering Services for the Phase III Upgrading and Expansion of the Encina Water Pollution Control Facility The Vista Sanitation District was authorized to enter into an agreement for engineering services with Brown and Caldwell for the Phase III Enlargement and Upgrading of the Encina Water Pollution Control Facility. The approved contract describes the treatment process as preliminary and primary treatment followed by biofiltration and secondary sedimentation. As part of the design process, an evaluation of treatment alternatives was prepared which compared biofiltration, rotating biological contactors and activated sludge. Attached are the results of that study. Surprisingly, the activated sludge process was very close to the biofiltra- tion process in the annual cost comparison. In cost to construct, the ac- tivated sludge process was $1,570,000 less than the biofiltration process. After reviewing Brown and Caldwell's "Evaluation of Secondary Treatment Al- ternatives", it was the consensus of the Encina Design Review Committee that the Design Contract be modified to reflect the activated sludge process rather than biofiltration. Their reasoning was that the activated sludge treatment would produce a much higher g_uality effluent with little additional total annual cost. The higher quality effluent would be more compatible with possible reclama- tion plans as well as with the legislated mandate to have the "best practi- cable wastewater technology" on line by 1983. Mr. Ron Beckman City of Carlsbad December 21, 1978 Page 2 The lower capital cost of the activated sludge processs would also reduce the local share of the construction costs of Phase III by about $196,250 of which Carlsbad's share is about $48,964. In order to revise the existing agreement for engineering services to accom- modate the treatment process change, Brown and Caldwell would like to nego- tiate additional fees and a longer design period. The additional fees could amoun to $24,950 to Carlsbad if grant funds are not authorized for the re- design. If grant funds are allocated, the local share would be only 12.5% of $24,950. The additional time necessary for the redesign would probably add about a month to the present 10 month design period. Due to the time necessary to prepare an amended contract for consideration by the Encina Agencies , with negotiated fee and a fixed time , the Design Review Committee has suggested the following: "That each agency authorize the Encina General Manager to direct Brown and Caldwell to proceed only with those tasks in the approved design contract which would not be affected by a change in the treatment process from bio- filtration to activated sludge." The authorization from your agency should be by letter to the Encina General Manager . If each of the agencies agree to the change in treatment process, then a for- mal contract amendment will be prepared and submitted to the six Encina Powers for approval. Les Evans General Manager LE/mgt attach. ENCINA PHASE III - PRELIMINARY DESIGN BIOLOGICAL SECONDARY TREATMENT PROCESS, ANNUAL COST COMPARISON Cost in thousand dollars Rotating biological Item Activated Sludge contactors Biofiltration Capital cost 8,730 11,700 10,300 Operation and maintenance O&M labor Power Chemicals Expandables and misc. Subtotal - O&M Capitalized annual cost Total annual cost 320 175 20 50 • 565 710 1,275 280 175 20 50 525 935 1,460 265 155 20 45 485 785 1,270 Based on an ENR Construction Cost Index of 3,400 and includes engineering, administrative and contingencies. DBased on 6-5/8 percent annual interest, 40-year life for structures and 20 years for equipment. 12/21/78 ENCINA PHASE III - PRELIMINARY DESIGN ADVANTAGES AND DISADVANTAGES OF SECONDARY TREATMENT ALTERNATIVES Options Advantages Pis advantage s Activated sludge Rotating biological contactors 1. Ability to produce a higher quality 1. effluent than required 2. 2. Easily adaptable to nitrification 3, or future tertiary process for re- 4. clamation 3. Greater ability to remove heavy metals 4. Minor odor production 5. Highest efficiency of coliform removal 6. Lowest capital cost 1. Simpler operation 2. No recirculation 3. Ability to nitrify 4. Better sludge handling characteris- tics . Sludge can be thickened in secondary sedimentation tanks 5. Modular design, flexible and abil- ity to accommodate future expansion 6. Ability to handle wide load fluctu- ations 1. 2. 3. 4. 5. 6. 8. 9. 10. 11. 12. 13. 14. Greater O&M efforts required Higher energy consumption More sophisticated controls Requires more land Highest annual capital and O&M cost Energy consumption higher than biofiltration Greatest potential for odor production Relatively new process in Western USA - lack of operational data Largest volume of odorous air to be treated Worst operating environment due to foul air in RBC enclosure (corrosion) Requires substantial land areas. Cannot accommodate tertiary units Longest open channel to be areated Higher energy (hydraulic) loss through plant Higher noise production (ventila- tion and blowers) High potential for short circuiting Not enough competition between man- ufacturers (high price). Only Autotrol makes air drive Less efficient in coliform reduction Inability to remove heavy metals u Page 2 ENCINA PHASE III - PRELIMINARY DESIGN ADVANTAGES AND DISADVANTAGES OF SECONDARY TREATMENT ALTERNATIVES Options Advantages Disadvantages Biofiltration o 1, Lowest O&M cost 1, 2, Simplest operation and least maintenance 2. 3, Greater ability to resist shock 3, loads and wide load (flow and 4, strength) variation 5. 4, Least energy requirement 5, Less noise produced 6, 6, Compact - Least amount of land required Reduced control over process effi- ciency Potential for odor production Possibility of ponding (plugging) Difficult to achieve nitrification Reduced ability to remove heavy metals Less efficient in coliform reduction 12/21/78