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Water System Design

Technical Review Needed Fire Flow Analysis Developer Services Summit November 16, 2010 Engineering - Asset Planning Joe Dugandzic, PE. Water System Design Public water systems are generally designed and analyzed hydraulically based on: Peak hour domestic demands

cynthia-strong
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Water System Design

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  1. Technical ReviewNeeded Fire Flow AnalysisDeveloper Services SummitNovember 16, 2010Engineering - Asset PlanningJoe Dugandzic, PE

  2. Water System Design Public water systems are generally designed and analyzed hydraulically based on: • Peak hour domestic demands • Emergency condition purposes (typically fire fighting and or power outage)

  3. Service Application Process: Who Does What? • Developer: Procures Design Professional to calculate domestic and fire flow demands. Ensures that Fire Official signs Needed Fire Flow (NFF) Worksheet. • Design Professional: Calculates expected domestic demands and building’s NFF. Typically will prepare and sign the NFF Worksheet on behalf of Developer. • Water Company: Evaluates system hydraulic and storage capabilities based on Design Professionals demand calculations. If necessary, identifies system improvements to adequately deliver NFF.

  4. What Water Company Does Not Do • Prepares or reviews any Automatic Fire Suppression System (AFSS) calculations • Requests Fire Official to sign NFF Worksheet • Requires existing customer base to finance system improvements to be used for applicant’s benefit.

  5. Water Company “Behind the Scenes” Analyses • Performs regulated Supply Capacity review to ensure system can add new customer demand. • Performs Hydraulic Modeling analyses using applicant’s projected demands. Extended Period Simulation identifies if new demands will create any service pressure, excessive velocity, or storage impact(s) to existing system.

  6. Water Supply Essentials for Fire Fighting • Rate of flow (gpm) • Residual pressure at that flow (psi) • Expected duration to contain a fire (hours) • Total quantity of supply needed (gallons)

  7. Example: NFF creates <20 psi residual pressure Existing System + New Demands + 750 gpm NFF 48 psi 17 psi 750 gpm 1,000 feet, 6-inch Diameter, C=100 NG Existing System + New Demands + 750 gpm NFF 48 psi 29 psi 750 gpm OK 500 feet, 6-inch Diameter, C=100 500 feet, 8-inch Diameter, C=100

  8. 75,000 gallons 15,000 gallons 500 gpm x 120 mins = 60,000 gallons OK Existing System + New Demands & 750 gpm NFF 75,000 gallons 0 gallons 750 gpm x 120 mins = 90,000 gallons Example: NFF could drain existing storage volume Existing System with 500 gpm NFF NG

  9. American Water Planning Criteria • DISTRIBUTION PIPING, PUMP AND STORAGE EVALUATION • The ability of distribution system facilities to provide safe, adequate and reliable service to customers is analyzed based on: • forecasted customer demands, and • fire protection requirements

  10. Analysis of Facilities • Pipelines • Storage tanks • Booster stations • Emergency power • Under peak demand conditions, a number of minimum standards should be met for each of these facilities.

  11. Pipelines • Distribution system mains are considered adequate if they can meet customer demands at a minimum system pressure of 20 psi. • Fire protection requirements should be met while maintaining a minimum pressure of 20 psi in the distribution system. • Note: State and local guidelines may require that higher pressures be maintained.

  12. Distribution Storage • Storage facilities are considered adequate if the effective volume of the facility, or groups of facilities acting together, provide sufficient volume to meet equalization needs and a fire protection reserve (if necessary) during maximum day demand events. • State regulations are also considered as they relate to a particular distribution system.

  13. Calculating Fire Flow Rates:ISO Guide For Determination of Needed Fire Flow Chapter 6 – Determining Recognition of Automatic Sprinkler Systems. ISO uses Specific Commercial Property Evaluation Schedule (SCOPES) to determine credit reduction of NFF for automatic sprinkler system protection. Must be installed and maintained in accordance to NFPA. Potential NFF credit reduction is not given until an ISO field inspection is conducted.

  14. Calculating Fire Flow Rates • What NFF should be requested on an application for service to New Jersey American Water? • ISO Non-Sprinklered • NFPA Sprinklered • Somewhere in between

  15. AWWA Manual of Water Supply Practices M31: Preface • Addresses the planning, design, and maintenance of distribution systems that supply water for fire protection and suppression. • The emphasis is on public water systems and not on water systems exclusively designed for fire protection. • The adequacy of a water distribution system for fire protection depends on the fire flows required.

  16. AWWA Manual of Water Supply Practices M31 • Water Supply Requirements for Sprinklered Properties (p. 40) • A fire can occasionally overcome the capacity of a sprinkler system. • Required fire flow for sprinklered properties consists of the flow required for sprinklers, including a hose-stream allowance or 500 gpm, whichever is greater.

  17. Calculating Fire Flow Rates • Based on the initial capital cost and operational expense incurred by building owners for installing an AFSS, American Water believes that some credit could be provided at the time of a service request. The NFF Calculation Worksheet was developed to ascertain NFFs at both ends of the spectrum. • It also is used to provide the local fire official an opportunity to acknowledge the building plans and provide experienced input for additional allowances for “outside” hose streams and adjacent structure exposure.

  18. Calculating Fire Flow Rates • NFF Calculation Worksheet • Developed by New Jersey American Water as a screening tool • Although the higher NFF value is based on ISO’s “non-sprinklered” formulas, the worksheet is not endorsed or sanctioned by the ISO • The NFPA 13 Automatic Sprinkler System value is not checked or approved by the water company or the local Fire Official • Should be used as a guide in determining the “water system” NFF

  19. Calculating Fire Flow Rates: Commercial and Multi-Family Buildings • New Jersey American Water is not responsible for operating and maintaining an AFSS. With an agreement from a building or property owner to be diligent in the AFSS maintenance, the company will consider recognizing an AFSS reduction for commercial or multi-family buildings or structures to a minimum of 1,000 gpm, should the NFPA 13 automatic sprinkler system flow, and requested fire official hose stream allowances be equal to or lower than 1,000 gpm.

  20. Calculating Fire Flow Rates: Residential One- and Small Two-Family Dwellings • If a new one- and small two-family dwelling is proposed with individual AFSSs, New Jersey American Water will recognize a NFF credit. In lieu of using ISO’s “non-sprinklered” NFF determinations (Table 7, Guide For Determination of NFF), the company will reduce the small residential dwelling NFF to a minimum of 500 gpm, provided the NFPA 13D automatic sprinkler system flow and requested fire official hose stream allowances are equal to or lower than 500 gpm. • If the proposed development does not include AFSS, ISO’s Table 7 NFF will then govern.

  21. Thank You. Questions? Lets now review the NFF Calculation Worksheet. Emphasize Residential vs. Commercial/Industrial

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