PSA - Long-Termed Control Plan Stantec Consulting Services

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Stantec Consulting Services Inc. 12 of 16 TO1 – Randolph-Sampson RTB PER the formulation of the recommended concept and used to define the scope for CFD modeling to be performed during subsequent phases of design (not part of this scope). STANTEC will work with the CITY to define RTB dewatering operation criteria including set points for initiation of dewatering operations, pumping flow range and control approach to empty the RTB in 24 to 72 hours, whichever criteria is determined to be required. The hydraulic design analyses will be documented in a Technical Memorandum and included in the PER as an appendix. Subtask 4.2- Screening and Floatables Control STANTEC will evaluate screening alternatives to reduce the amount of solids and floatables entering the RTB and protect the dewatering pumps. Both manually cleaned bar rack and mechanically cleaned screen systems will be evaluated for their applicability to this project. The preliminary clear spacing of the screen will be evaluated based on the hydraulic analysis and RTB dewatering pump requirement. Subtask 4.3- Solids Management STANTEC will evaluate alternatives for management of solids that will accumulate in the RTB during operation. The alternatives may include manual and automatic flushing systems and interior access for mechanical removal of the solids as well as provisions for conveyance of solids downstream via the CITY’s interceptor system or containerization of the solids at the RTB site. Requirements for confined space entry safety and RTB ventilation will be considered in the alternatives analysis. Subtask 4.4- Disinfection Process STANTEC will evaluate three disinfection technologies for meeting the design criteria established in the LTCP. Alternatives to be considered include sodium hypochlorite /sodium bisulfite (for dechlorination), peracetic acid (PAA), and ultraviolet (UV) light. If sodium hypochlorite or peracetic acid is selected as the disinfectant, STANTEC will coordinate with the CITY to conduct a bench-scale test to determine the chemical dose required to meet “RTB Treatment Performance Criteria,” in the Table-1 of the LTCP. The testing will be performed on the wet weather samples collected by the CITY from the 90” interceptor near the proposed diversion structure. The rainfall event that triggers the sampling will be determined during the hydraulic design of the RTB under Subtask 4.1. Three (3) sampling events will be conducted. The testing will include the following activities: • STANTEC will develop a testing plan and protocol for the CITY to review. • STANTEC will conduct a meeting with the CITY staff to discuss the testing plan and detailed logistics for sample collection, transport, and analysis. • The CITY will furnish all testing materials and equipment, collect wastewater samples, conduct the bench-scale tests, and provide laboratory analyses. • STANTEC will analyze the test data and develop a dose-performance curve which can be used in conjunction with the RTB size and flow to estimate the effluent E. coli count. Based on the chemical dose and analysis of flow (e.g., activation frequency, duration and flow of the RTB), STANTEC will develop the design criteria for chemical storage and feed facilities, including