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Item 4F-4G Attachement AM E M O R A N D U M TO: FROM: SUBJECT: April 21, 2023 Alison Ortowski, Assistant City Manager Rob Cohen, Director of Public Works Wastewater Master Plan Modeling Recommendation REQUEST We respectfully recommend completing a modified wastewater system modeling prior to the adoption of the updated Wastewater Master Plan, and request to enter into an agreement with Freese and Nichols for these services. Freese and Nichols provided an updated scope of work in November 2022, and we recommend proceeding with the scope as presented. BACKGROUND As required by charter, the City of Southlake updates certain master plan documents every four years. The most recent Wastewater Master Plan was adopted in 2012 and utilized modeling from 2009 that identified needed improvements for current and future capacity. Since that time the City has conducted flow monitoring with the Town of Westlake for the N-1 interceptor in 2016, and flow monitoring along with smoke and dye testing in 2017 - 2018. In 2021, Public Works and Planning & Development Services began preparations for a master plan update, and with that the evaluation of updated studies and modeling to inform plan recommendations. The following questions and information shaped the basis of the request and recommendation above: •What will modeling tell us that we don’t already know? At a fundamental level, modeling the wastewater system will ensure that our system can meet the demand of both our residential and day-time population. The modeling will also inform us to direct resources toward correcting issues with current capacity and building out our system to handle future capacity. Our current knowledge of the wastewater system is largely based on the 2007 -2010 Sanitary Sewer Evaluation Study (SSES), which included the above referenced 2009 model. Since that time the North Service Area has had an increase in development, and staff recommends modeling this area to best plan future capital projects and determine the efficiency and capacity of the existing infrastructure. •What needs to be further investigated? The following summarizes the major items requiring further investigation: o The original model only included all 10-inch mains and larger, and some 8-inch mains (approximately 40% of the 2009 infrastructure), the proposed scope Page 2 includes all wastewater lines within the North Service Area. This will allow for a more accurate model. o This model will inform issues with the design and capacity of existing infrastructure, for example the Lonesome Dove lift station and wet well. o Improve wastewater basin accuracy, including the design of flow, volume, and capacity throughout the basins. The City is divided into two service areas (north and south) and within these areas are basins that map where wastewater collects before flowing to the outfall area. o Identify impacts of development segments that were not modeled previously. o Inform the capital improvements program and impact of future growth on the wastewater system. • Do we need to model the full system to answer our questions? No, it does not need to be modeled as a full system. The wastewater system is divided into two basins (also referred to as service areas) and then further sub -basins. The wastewater system requires individual models for each sub-basin. Our recommendation is to model the nine sub-basins within the north service area due to the south service area being largely developed and not having much capacity for growth or expected additional flow from development. SCOPE & TIMELINE The proposed project scope and timeline is attached to this memo, and includes all needed elements to finalize the master plan. The estimated time to complete the full modeling is an estimated 6 – 9 months, with an additional three months to finalize master plan recommendations. FINANCIAL IMPACT The financial impact of this agreement is estimated at $169,800. Funding for this agreement is budgeted in the AWIA project of the Capital Improvements Program (CIP). Attachments: Scope of Work Guide, updated November 2022 CC: Daniel Cortez, Director of Economic Development & Tourism Dennis Killough, Director of Planning and Development Services Lauren LaNeave, Deputy Director of Public Works – Administration Page 1 of 5 City of Southlake Wastewater Master Plan Update - Scope of Services November 21, 2022 DRAFT Project Background: This project is an update to the City’s Wastewater Master Plan in order to proactively plan for the future of the Denton Creek/Grapevine Lake collection system in the City of Southlake. The master plan process will update the future flow projections, update the hydraulic wastewater model, and provide an updated Capital Improvements Plan (CIP) for the Denton Creek/Grapevine Lake service areas (for the purposes of this report, this will be referred to the North Service Area). As the City approaches its ultimate buildout conditions, the Master Plan update will focus on developing projects needed to promote a high level of service for existing and future customers in the North Service Area. FNI will compare proposed projects to projects in the current Master Plan to determine if they are still needed or can be removed from the City’s long-term plan. This project scope assumes FNI is updating the City’s Water Master Plan and will utilize demographic projections from the water project. BASIC SERVICES Task A. North Service Area Project Management, Data Collection, and Wastewater Flow Projections A.1 Administration: Perform general administration duties with the project, including progress meeting scheduling, general correspondence, office administration, and monthly invoicing. A.2 Project Kick-off Meeting: FNI will conduct a kick-off meeting with the City to discuss and solicit input for objectives and goals of the project. The team will also review project scope, schedule, communication, and present a data request memorandum. A.3 Document Control: FNI has established Document Control procedures to enable proper recordkeeping and retrieval. The Document Control procedures use a standardized electronic index, set up at the outset of the project. Protocols are observed for electronic and paper records, confidentiality and security, and proper distribution and retention. Documents will be assigned unique names and the filename and path included in the footer of each document. A.4 Monthly Progress Reports: A Monthly Status Report will be submitted, summarizing progress against specific tasks and scheduled tasks to be accomplished in the upcoming month; outlining upcoming key decisions which will require input from, or discussion with, City staff; and listing any problems or unresolved issues. A.5 Data Collection: FNI will compile information from the City including GIS files, as-built, work order data and preliminary design drawings for projects currently under design in the North Service Area. FNI will review the data request memorandum with the City to determine what data and data format is available from the City. FNI will obtain input on historical problem areas in the collection system. A.6 Review Historical Wastewater Flows: FNI will review historical wastewater flows and analyze historical per-capita rates and peaking factors to establish baseline conditions for existing and future wastewater flows in the North Service Area. Page 2 of 5 A.7 Develop Wastewater Flow Projections in the North Service Area: FNI will use the land use assumptions from the Water Master Plan, historical usage data and input from the City’s staff to develop wastewater flows for existing, 5-year, 10-year, and ultimate buildout conditions for residential and commercial land uses in the North Service Area. FNI will develop the wastewater flows utilizing per-capitas, peaking factors values that are specific to the City of Southlake, taking into account historical characteristics, and in accordance with TCEQ guidelines. FNI will also compare the historical flow data by land use type and provide recommendations for per-capita flow ranges within a specific land use type (i.e. commercial, industrial, etc.). A.8 Meet with the City to Review the Wastewater Flow Projections in the North Service Area: FNI will prepare for and conduct a meeting with City staff on the updated wastewater flow projections for the North Service Area. Task B. North Service Area Historical Flow Monitoring Review and Data Evaluation B.1 Review of Historical Wastewater System Planning Documents: FNI will review historical planning documents, including the previous Wastewater Master Plan and Wastewater Collection System Flow Monitoring Report, plus other relevant documents. Results and recommendations from the historical studies will be considered when evaluating capacity modeling and development of the updated CIP for the North Service Area. B.2 Historical Flow Monitoring Data Evaluation: FNI will review the flow monitoring and rainfall data from the 2017-2018 temporary flow monitoring assessment and prepare the data to be used in calibration of the revised model. It should be noted that this data is nearly 5 years old and could impact the accuracy of the calibrated model with existing system flow conditions. Task C. North Service Area Wastewater Model Development and Calibration C.1 Evaluate and Review Wastewater System GIS for Developing All-Pipes Wastewater Model for the North Service Area: FNI will analyze wastewater system GIS information and historical mapping data to determine additional pipeline attribute data or connectivity corrections needed for wastewater model development including recently constructed lines that may not be included in the GIS. This evaluation will be conducted for the North Service Area. C.2 Sewer Basin, Sub-Basin, and Subcatchment Generation for the North Service Area: FNI will review and update sewer basin delineation for the North Service Area using ground contour and system mapping. FNI will develop sewer sub-basin delineation representing meter areas and geographical areas within each sewer basin that is more refined than the flow meter basin delineation. FNI will generate subcatchments for each sewer sub-basin showing which areas feed into each sewer manhole within their respective flow meter basins. FNI will develop a flow meter schematic showing which sewer basin and metered sub- basins feed into each sewer interceptor for model analysis and data output review. C.3 All-Pipes Hydraulic Wastewater Model Development for the North Service Area: FNI will develop the wastewater model and utilize GIS data to include all wastewater lines within the North Service Area in the selected modeling software. FNI will create an electronic shapefile of the City’s water customers showing location and usage by assigning a spatial location to each meter through a process called geocoding. This information will be used as part of the model validation and verification process. Page 3 of 5 C.4 Dry Weather Calibration for the North Service Area: FNI will select a dry weather calibration event to isolate projected flows as primarily domestic contributed flows. FNI will perform dry weather calibration of the selected dry weather flow event using calibrated flow volume by adjusting antecedent conditions, per capita flows, diurnal curves, and dry weather infiltration in the North Service Area. FNI shall prepare charts and profiles at selected calibration points showing metered vs. modeled dry weather calibration for flow, depth, and velocity. C.5 Wet Weather Calibration for the North Service Area: FNI will review the flow meter data and select a wet weather calibration storm event. FNI will perform wet weather calibration using the EPA approved RTK methodology on selected wet weather flow events using calibrated peak I/I. FNI will adjust model parameters to calibrate flow, velocity and flow depth in the North Service Area. FNI will prepare charts and profiles at selected calibration points showing metered vs. modeled wet weather calibration results. C.6 Design Storm Evaluation: FNI will evaluate design storms and develop recommendations on design storms using return period and storm intensity for individual sewer basins and interceptors, based on level of service recommendations using existing available data. C.7 Meet with City to Review Model Development and Calibration: FNI will meet with the City to discuss the model development, model calibration, and design storm evaluation. Task D. North Service Wastewater System Modeling and Performance Analysis D.1 Design Criteria and Level of Service Evaluation: FNI will evaluate and recommend wastewater system planning criteria, including design flows, minimum and maximum pipeline velocities, TCEQ requirements and surcharging guidelines. The criteria will determine the level of service and what surcharging, if any, is allowed, minimum and maximum velocity constraints, etc. Criteria will be developed for overall master planning purposes, development reviews, and environmentally sensitive areas. D.2 Wastewater System Capacity Evaluation for the North Service Area: FNI will run the calibrated wastewater model with design storm(s) and identify existing surcharging and overflow locations and other capacity/restriction issues in the North Service Area. This will provide the baseline evaluation of where the collection system currently has issues. This task will establish critical projects that will be included in the short-term recommendations. FNI will perform the capacity evaluation on the existing and future collection system (5-year, 10-year, and ultimate buildout) using the flows developed in Task A. FNI will prepare mapping and model results for the North Service Area showing all surcharging and overflow locations by magnitude and locations. FNI will categorize manholes by overflow amounts during design storm and sewer line surcharging by amounts during design event(s). D.3 Wastewater System Lift Station Assessment for the North Service Area: In parallel with the gravity main assessment, FNI will evaluate the lift station in the North Service Area for potential capacity issues, pump cycling and lifespan, and wet-well sizing. FNI will also evaluate the feasibility of eliminating any existing lift stations with gravity sewer improvements. No on-site field inspection assessment will take place as part of this task. Page 4 of 5 D.4 Develop Wastewater System Improvement Alternatives for the North Service Area to Address Capacity Issues: Using the results of future system modeling, FNI will develop improvements to eliminate excessive surcharging and overflows in the collection system resulting from increased wastewater flow from projected future growth, development, and redevelopment in the North Service Area. FNI will develop improvements alternatives for gravity lines, lift stations, force mains, and special structures within the North Service Area. Improvements needed to correct existing deficiencies will also be included. FNI will utilize model results to develop improvements to serve areas that are currently not developed or served by the City. FNI will prioritize rehabilitation areas based on flow monitoring results and operational data to help reduce infiltration/inflow. FNI will develop mapping showing improvements required for the 5- year, 10- year, and ultimate buildout planning periods as well as improvements needed to correct existing deficiencies in the North Service Area. D.5 Meeting to Review System Performance Modeling and Alternatives Analysis: FNI will prepare for and conduct a meeting with the City to discuss the system modeling and associated evaluations. Task E. North Service Area Wastewater System CIP and Master Plan Report E.1 Develop Draft Capital Improvement Plan Costs, Phasing Plan, and Project Drivers for the North Service Area: FNI will develop costs for each proposed project, draft CIP scheduling of projects based upon wastewater system modeling requirements, project drivers (such as growth, regulatory, renewal, etc.) and mapping showing project locations. Costs will be in existing year dollars and will include engineering and contingencies. Projects will be phased by fiscal year for the first five year and by planning period for subsequent projects. E.2 Compare Proposed Improvement Alternatives to 2012 CIP List: FNI will compare the developed list of projects in this Wastewater Master Plan update to the existing 2012 CIP project list. FNI will note differences and provide justification for potential changes to CIP projects. E.3 Meeting to Review Draft Capital Improvements Plan: FNI will prepare for and conduct a workshop with the City to discuss draft CIP, project phasing and results of prioritization. E.4 Revise CIP and Prepare Draft Wastewater System Master Plan Update Report for the North Service Area: FNI will revise the hydraulic modeling and CIP based upon the City’s comments and feedback and prepare a master plan report discussing field test results, assumptions, wastewater flow projections and recommended capital improvement plans including phasing and costs of improvements for the North Service Area. The report will include colored maps showing proposed system improvements as well as GIS digital copies. FNI will provide the City with three (3) copies of the draft report for review plus an electronic PDF copy. E.5 Finalize Wastewater System Master Plan Update Report for the North Service Area: FNI will conduct a comments review meeting with City staff and will finalize the Master Plan Report based on feedback received. FNI will provide the City with five (5) copies of the final report, and electronic PDF copy, and any requested modeling/GIS files. E.6 Public Involvement and Presentations: FNI will prepare for and attend up to four (4) public meetings with various stakeholder groups to review and discuss the results and recommendations of the Wastewater Master Plan Update. Page 5 of 5 E.7 Coordination Meetings with TRA: FNI will prepare for and attend up to two (2) meetings with City Staff on the following items, if necessary: · Outstanding data needs · Wastewater flow projections · TRA point-of-entry hydraulics · Planned CIP projects (TRA and Southlake) Task Task Name Labor Cost Expense Cost Total Cost A North Service Area Project Management, Data Collection, and Wastewater Flow Projections $21,698 $1,476 $23,175 B North Service Area Historical Flow Monitoring Review and Data Evaluation $12,699 $719 $13,418 C North Service Area Wastewater Model Development and Calibration $26,463 $1,809 $28,272 D North Service Area Wastewater System Modeling and Performance Analysis $39,394 $2,983 $42,377 E North Service Area Wastewater System CIP and Master Plan Report $57,597 $4,960 $62,556 $157,851 $11,947 $169,800 $157,851 $11,947 $169,800GRAND TOTAL Basic Services Total City of Southlake Wastewater Master Plan Update - North Service Area UPDATED 4/5/2023 Summary by Task DRAFT Basic Services A North Service Area Project Management, Data Collection, and Wastewater Flow Projections B North Service Area Historical Flow Monitoring Review and Data Evaluation C North Service Area Wastewater Model Development and Calibration D North Service Area Wastewater System Modeling and Performance Analysis E North Service Area Wastewater System CIP and Master Plan Report Southlake Wastewater Master Plan Update Project Schedule DEC JAN 2023 2024 Draft Wastewater CIP - October 2023 Draft Wastewater Master Plan Report - December 2023 Final Wastewater Plan Report - January 2024 NOVAUG SEP OCTFEB MAR APR MAY JUN JUL Project Task Key Project Milestones (Dates Approximate)