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A Balancing Act: Complex Distribution System Planning in Western NC Foothills

This presentation discusses the water system master plan in Caldwell County, NC, addressing operational challenges and providing a roadmap for the future. It includes an overview, approach, findings, and alternative solutions.

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A Balancing Act: Complex Distribution System Planning in Western NC Foothills

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  1. A Balancing Act: Complex Distribution System Planning in the Western North Carolina FoothillsTina Whitfield - HDR

  2. Agenda 01 Overview 02 Approach 03 Findings 04 Alternatives and Solutions

  3. 01 Overview

  4. Background What? Water System Master Plan Why? Address Operational Challenges and Provide Roadmap for the Future Where? Caldwell County, NC Who?Caldwell County Water System • 8,800 customers over 140 square miles • Distribution-only water system • 300 miles of distribution line • Elevation ranges from 940 to 1550 feet AMSL When?2015 - Current

  5. Caldwell County Water System – Populationand Supply • Rural water distribution system serving a population of 22,600 in four (4) distinct water systems: • Southeast System • North System • West System • Addison Lane • Purchases water from the City of Lenoir, Town of Granite Falls and the City of Hickory through numerous master meter connections. • Also sells back water to the City of Lenoir and Town of Granite Falls

  6. Challenges and Drivers • Experiencing both ends of the spectrum for pressures • Excessively high • Low • Fire Flow Deficiencies • Water quality problems in long stretches of distribution main • Low volume/supply in certain areas of the system

  7. 02 Approach

  8. Traditional Master Planning Elements • Basis of Planning • Model Update • System Evaluation

  9. Unique Analyses to Caldwell County • Master Meter Pressure Variation Analysis • PRV Operational Strategies • Water Supply and Availability over Varying Terrain • Storage Requirements

  10. Basis of Planning Approach • Evaluate Current Population and Customer Breakdowns • Review Historical Demand • Analyze Large User Demands • Review Past Growth Trends • Review Current Local Growth and Land Use Plans • Review Recent Growth Studies and Projections • Develop Growth Projections and 20-Year Forecast

  11. Model Update and Calibration Approach • Update Physical Network • GIS • As-Builts • Staff Interviews and Windshield Surveys • Review Service Zone Boundaries • Update Demands • Geo-coded Billing Data • Model Calibration • Master Meter Pressure Recorder Data • Fire Hydrant Flow Tests

  12. System Evaluation and Criteria • Wide Range of Operating Pressures due to Topography • Experiencing Severe Deficiencies in Fire Flows. Criteria established low, with intent to raise as system improvements are made. • System Storage based on NC DEQ “Rules Governing Public Water Systems”

  13. 03 Findings

  14. Basis of Planning Findings • Loss of Population in the Recession • Slow Increase over Last 3 Years

  15. Basis of Planning Findings • Consistent Average Day Demands, Maximum Month Demand and Per Capita Demand

  16. Basis of Planning Findings • Previous Plan had been completed in 1993 • Since that time a number of studies have been completed including: • 2010 Census and NC Office of State Budget and Management • 2004 Yadkin Valley Water Supply Planning Study • 2012 Catawba-Wateree Water Management Group (CWWMG) Water Supply Master Plan

  17. Basis of Planning Findings

  18. Basis of Planning Findings • Review of Supply from Water purveyors • Needed Supply • Contractual Obligations and Timeline • Available Supply and Treatment Capacity

  19. Model Update • Confirmed Service Zone Boundaries • Confirmed Service Zone HGL • Updated Supply from City of Lenoir at Master Meter Locations • Updated Storage and Pumping • County had transferred ownership of two (2) tanks to the City of Lenoir • County had removed one (1) tank from service due to landfill expansion • Five (5) booster pump stations • Updated Network • Additional distribution mains • PRV stations and operation(s) • Updated Demands • Existing Billing Data (Geocoded)

  20. Model Calibration • Based on recent M32 Update and “Calibration Guidelines for Water Distributions System Modeling” (AWWA, 1999). • The calibration criteria applied for this hydraulic model are: • The absolute difference between the pressure drop simulated in the model and that observed in the field should be less than and equal to 2 psi in 85 percent of the observations. • For all observations, the absolute difference in pressure drop should be less than or equal to 5 psi.

  21. Master Meter Pressure Variation Analysis

  22. Existing System Evaluation

  23. Future System Evaluation

  24. Storage Analysis

  25. 04 Alternatives and Solutions

  26. A Question of Storage • Additional Storage needed to meet system requirements. • Storage should be located in proximity to demand • Southeast System • West System

  27. A Question of Storage • Maximizing Existing Storage • Southeast System: Draco Tank • Water cycling difficult during low to regular demands • Rapid drain during high demands • Long straw • Far end of system • Solution: Install control valve at master meters to read level at Draco Tank and allow system to float during low/regular demands • Solution: Provide additional storage to meet storage deficit in a location more central to demand

  28. A Question of Supply • Low Fire Flow Availability • Low Residual Pressures • Reason? • Lack of storage requires flow through master meters • PRVs isolating sections of system and restricting flow to areas • Long sections of pipe with not sufficient enough response for a fire flow • Solution • Provide additional storage • Evaluate PRV operation

  29. A Question of Supply • Specific Recommendations: • Pump station and hydropneumatic tank rehabilitation is recommended for the Drag Strip system. It serves a small modular development and experiences problems with pressure and supply.

  30. PRV Operational Strategies • Southeast System: Modify and/or repair existing PRVs so that flow can move through the system. PRVs are currently closed. • A pressure reducing valve is recommended to address the operational issues associated with the Cedar Rock tank. This will allow the County to better utilize this tank.

  31. PRV Operational Strategies

  32. Next Steps

  33. Conclusion • While a small system, faced with complex obstacles to providing sufficient supply, pressure, and fire flow to the system. • Distribution-only system that depends on others for supply provides an additional challenge • Careful planning can result in solid path forward to success.

  34. Questions? Tina Whitfield tina.whitfield@hdrinc.com Karen Maye kmaye@caldwellcountync.us

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