R2026-124 Resolution Authorizing Agreement with Burns and McDonnell Engineering Company, Inc., to Provide Professional Engineering Services to the City of Decatur for the South Water Treatment Plant Expansion Plan, City Project 2025-03

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City's existing and proposed treatment processes for treating the above contaminants. While the presence and treatment requirements of these emerging contaminants will be considered, there are necessary limitations for stating defined treatment processes for emerging regulations. Since the details for these emerging considerations are forward looking,the treatment recommendations will also be forward looking.As a result,the analysis for establishing guiding design decisions will be qualitative in nature. 4) PRIMARY TREATMENT EXPANSION a) Obtain and review existing documentation, drawings, and operational data, including flow rates, raw water quality, and chemical dosages, for the two square solids contact clarifiers and the two Claricone units. Raw water data review will consider trends and compare changes between original raw water quality data on which the existing WTP was designed and raw water quality data from the last 5 years.This data will be from the previous 5 years and will include statistical consideration such as standard deviation for use in bookending statistically significant variances in the data. The purpose of these analyses is to become generally familiar with the current performance of the primary clarifiers and Claricones. Special consideration will be given to the impact of operating the Claricones at a greater pH than the square solids contact basins and how that would affect finished water quality with respect to TOC removal, residuals production and hardness removal. b) Analysis will focus on the time period when the existing solids contact clarifiers were carrying the entire treatment load (i.e. during Claricone construction). c) Field Performance Testing: i) Prepare and submit a testing plan to evaluate the performance of the existing square solids contact clarifiers under various hydraulic and solids loading rates to the City for approval. The testing plan will outline the proposed testing procedures, operational adjustments, and monitoring parameters intended to evaluate the clarifiers'performance under specific conditions. ii) Upon City review and approval of the testing plan, the City will conduct up to three (3)full-scale field performance tests on the existing primary clarifiers at incremental loading rates (e.g., 8 MGD, 10 MGD, 12 MGD, or maximum achievable) and three (3) different pH set points to evaluate performance limitations. The duration of testing at each different loading rate is proposed to last until equilibrium is reached. This is anticipated to take a minimum of 1 week but may last up to 4 weeks. BMcD will provide two (2) staff for up to three(3) days of testing,assumed to one day per round of testing to confirm collected water quality parameters. iii) Upon completion of the testing, data gathered and collected by the City during testing will be provided to BMcD to form the basis of the alternatives analysis. The data is anticipated to include effluent turbidity, pH, alkalinity,total hardness, flow, and sludge blanket stability, including mixer speed, rake arm torque, blowdown frequency, blowdown duration, blowdown solids, and sludge blanket elevation, on the primary clarifiers, Claricones, and combined effluent(except for sludge blanket stability). d) Identify and develop viable alternatives for the square solids contact clarifiers based on data analysis and field testing results. i) The alternatives are anticipated to include: 3