Fort Walton Beach Council agenda — 04-29-03 workshop agenda — reading text

control equipment to direct the RAS to the process basin. I primary clarifier will remain in operation and another 70- foot diameter final The clarifier will be necessary once AADFs approach 3.50 MGD. The total probable I opinion of cost for the upgrades to the City' s WWTP to incorporate the WesTech STM- AerotorTM is estimated to be approximately $ 2, 938, 750. Based on the I proposed plan described above it is anticipated that the overall program should be completed within 26 months from inception and no downtime of the facilities should be required. ill fit ES. 5.3 Oxidation Ditch - Modified Ludzack- Ettinger Process 1M III For the third alternative, there are a number of activated sludge processes that can be used to replace the existing RBCs. Based on our evaluation of the various 1M alternatives available for the City, a Modified Ludzack- Ettinger ( MLE) process I with mechanical aeration is considered the preferred alternative. This process is III commonly referred to as an oxidation ditch system. This type of system was selected for its ease of operation, lower maintenance costs, successful track record, and ability to meet more stringent future pennit requirements. Two ( 2) process trains are recommended, which will provide good operational flexibility and the close proximity of the aeration equipment for this layout iii simplifies construction, piping, electrical and installation. It was detennined that III 150 HP aerators are necessary for each basin. As with the previous alternative, the MLE process is an activated sludge process I,' which will require recycle pumping of RAS from the secondary clarifiers and the addition of a third clarifier when AADFs approach 3. 50 MGD. The RAS is a II necessary component in an activated sludge process and will require the addition of recycle pumps, recycle wet well, yard piping, and control equipment to direct III! the RAS to the process basin. Additional yard piping will be required to bring the F:\2001\ 01.0387. 000\Report\ R-4\ 041403 FINAL\Excecutive Summary 041503. doc HAI# 01.0387. 000 ES- 7 04/ 14/ 03 M II constructed oxidation ditch online. Other components that will be newly incorporated into the design of the oxidation ditch system are the necessary W instrumentation and controls. These features are key elements that can have a profound effect on the perfonnance of the system and operational costs. The total probable opinion of cost for the upgrades to the City's WWTP is estimated to be approximately $ 4, 262, 500. Based on the proposed plan described above it is anticipated that the overall program can also be completed within 26- months from I inception, with no downtime of the facilities required. I Based on the cost infonnation researched for the improvements, modifications, and/ or upgrades that are required for the existing wastewater facilities, a 3D- year present value I analysis was perfonned for each of the three ( 3) alternatives. The purpose of this analysis was to accurately weigh the financial components of each alternative, the r historical operating expenses, projected operating expenses, and projected capital costs to ill determine a present value. The present value analysis for each wastewater treatment facility alternative utilizes data provided by the City and several other considerations and assumptions which are summarized below: i III 1. and maintenance ( O& M) expenses remained constant for the Operating purpose of comparing the various wastewater treatment alternatives. III 2. The operating and maintenance expenses were estimated from the City' s Wastewater Utilities Fund, power costs were projected, and labor expenses were estimated. 3. Capital costs were projected utilizing actual component replacement costs from City records as well as unit costs obtained from bid experiences of III similar wastewater facilities and cost estimates from equipment suppliers. II1II 4. An analysis period of 3D- years was used, together with an assumption of a II discount rate of 5- percent. 5. An average capital inflation rate of 2. 72- percent was assumed as reported in I~>::~ the Engineering News Record ( ENR) and Handy- Whitman Index ( HWI). 6. An average operating inflation rate of2. 5- percent was assumed. 7. Average service lives were assumed for each process component based on industry standard values. till! II The present value analysis perfonned for each of the treatment alternatives included the estimated construction cost and the present worth of O& M costs. Construction costs F:\2001\ 01.0387. 000\Report\ R-4\ 041403 FlNAL\ Excecutive Summary 041503. doc HAI# 01.0387. 000 ES- 8 04/ 14/ 03 p- ili ill y<3 were estimated based upon vendor' s quotations, estimated installation costs, cost data for similar projects, and published cost data, as previously discussed. e II The O& M costs utilized for this analysis included the cost of labor, power, and nonnal I replacement parts. Inflated component replacement costs are added to the present value analysis at the end of each components average service life (ASL). A residual value was added back to the present value for components with a useful life remaining after the 30- I year analysis. These residual values were based on an assumed ASL and straight- line depreciation over the ASL for each component. The estimated capital costs and I component residual values for each alternative are shown in Tables A-4, A-5, and A-6. I The 30- year present values detennined for the original three ( 3) alternatives are summarized below in Table ES- l. I Table ES- l Summary of Present Value Analysis for Initial Three Alternatives I WesTech STM- MLE Oxidation Ditch I. Existing RBC' s Aerator System filii Present Value $ 5, 887, 585. 00 $ 5, 298, 999. 00 $ 6, 715, 312. 00 ill Residual Value $ 950, 000.00 $ 656,250.00 $ 925, 000.00 II Total Value $ 4, 937,585. 00 $ 4, 642, 749. 00 $ 5, 790,312. 00 iiJ iii To detennine the most appropriate alternative, each process alternative underwent a I weighted alternative analysis. Based on the results of the subjective analysis of the three 3) alternatives, the MLE process was the most favorable alternative option. While this fit option is the highest in tenns of capital outlay, it provides the City with numerous advantages over the other alternatives considered. As noted previously, there are fill I approximately 283 WWTPs in the State of Florida with pennitted capacities from 1. 0 III MOD and greater. Of these WWTPs, 101 of these facilities or approximately 35. 7- percent are oxidation ditch facilities. Moreover, recent trends have been to replace fixed film treatment processes, similar to the City' s with activated sludge systems similar to the one recommended for the City. In addition, an added advantage of this type of system is I this process can be modified to achieve a higher degree of treatment, such as for nutrient F:\2001\ 01.0387.000\ Report\ R-4\ 041403 FINAL\Excecutive Summary 041503. doc HAI# 01.0387. 000 ES- 9 04/ 14/ 03 lit it.: I removal, should the need arise from stricter discharge limits imposed on the City' s WWTP by the FDEP. I ES. 6 PROPOSED WWTP CAPITAL IMPROVEMENTS i Based on the findings in this report, it was determined the MLE oxidation ditch III alternative, was the most viable option to replace the City' s existing RBC treatment Ii process. Although the MLE oxidation ditch system was the recommended alternative, the City desired to further investigate the option of replacing the existing RBC process I with new RBC equipment compared to the MLE process. The initial capital expenditures associated with installing new RBC units were detennined to be substantially less than I that of the MLE oxidation ditch alternative. However, each of these treatment alternatives has unique requirements separate from the secondary process, which impact I the total capital expenditures. The screening and pretreatment facilities at the beginning of the City' s existing treatment I system are common to both the RBC process and MLE process. The total capital cost associated with the screening and pretreatment facility rehabilitation including engineering, contingency, and pennitting is estimated to be $ 131, 250. lilt II From the pre- aeration basin wastewater discharges to the primary clarifiers. The City' s WWTP utilizes two ( 2) 65- foot diameter circular primary clarifiers, with operating I sidewater depths of 12- feet. The concrete appears to be in good condition, however the bridges to the clarifier drives are corroded. It is estimated that it will cost approximately I 312, 500 for rehabilitation of the clarifiers drive units for these two ( 2) units. This iii capital expenditure is associated only with the RBC process since the MLE process does not require primary