Uni-Directional Flushing Program Planning, Development, and Implementation. July 12, 2018

Transcription

1 Uni-Directional Flushing Program Planning, Development, and Implementation July 12, 2018

2 Agenda Introductions UDF Overview Kevin Williams Example Sequence Water Quality Considerations Planning for UDF Kevin Williams Model and GIS Updates Budget Considerations Development James Linton Design Criteria and Requirements City of Richmond, Henrico County UDF Overviews System Examples QA/QC Implementation James Linton Schedule Consideration Contractor Selection and Inspections Water Quality Sampling Public and Customer Notifications Lessons Learned Kevin Williams Benefits Kevin Williams

3 Uni-Directional Flushing Pull Clean Water from the Source, at High Velocity, Through the Entire System Advantages Significant Improvement in Water Quality Lower DBPs Decrease in Customer Complaints Due to Taste, Color, and Odor Can Incorporate into Valve and Hydrant Maintenance Program Disadvantages Manpower to Implement Program High Water Use Cost to Repair Valves and Hydrants

4 UDF Flushing Sequence Example

5 UDF Flushing Sequence Example

6 UDF Flushing Sequence Example

7 UDF Flushing Sequence Example

8 Uni-Directional Flushing Water Quality Considerations Biological and Mineral Deposits Form on Every Wetted Surface The Organic Matter Provides a Rich Ground for Bacteria and Biofilms that Consume Chlorine Disinfection, Lowering Residuals, Forming DBPs To Maintain Residuals, Utilities Increase Chlorine and Chloramines that Further React with Biological Matter and Form Greater Levels of DBPs Eventually, Because of the Biological Interference, Residuals Cannot Be Maintained and DBPs Cannot Be Reduced Without Distribution System Intervention

9 Planning for UDF Design Model Development Pressure Zones System Configuration Source Waters Confirm Function and Location of All Assets Valves, Hydrants, Blowoffs, etc. Confirm System Boundary Conditions Update GIS (Needs to Include All Pipes, Valves, and Hydrants) Plan Operations Support with Neighboring Jurisdictions Confirm Public Notification Procedure Budget (Design & Implementation) Implementation (Contractor or In-House)

10 Planning for UDF Budget Considerations Program Development Internal Management GIS and Model Updates System Maintenance and Repair Implementation (Contractor/Inspector, In-House Resources) Water Usage

11 UDF Development Design Criteria Flushing Velocity (Min, Max) Turbidity Requirements Minimum Pipe Volume Turnover Design Requirements GIS Data Software Time (Hrs. Per Sequence) QA/QC

12 UDF Development Henrico County UDF Henrico County System 7 Pressure Zones 1,700 Miles of Pipe Approximately 1,500 Miles Can Be Flushed (<16 diameter)

13 UDF Development System Maintenance and Water Quality

14 UDF Development Henrico County UDF Coordinated Sequences for Proper System Flushing and Continued Operation

15 UDF Development Henrico County UDF Coordinated Sequences for Proper System Flushing and Continued Operation

16 UDF Development Henrico County UDF Coordinated Sequences for Proper System Flushing and Continued Operation

17 UDF Development Henrico County UDF

18 UDF Development Henrico County UDF Costs Design Costs for Year 7 Phase A $77,221 Modeling/Map Development of 660 Flushing Sequences Estimate for Design = Total LF for 3 to 12 mains/800 = 660 of Sequences $117/Sequence Current Status Design/Map Development for Year 7 Phase A Completed Total of 666 Sequences over 71 Sections Average of 9.38 Sequences per Section Average Total Flushing Time of 58 Minutes Per Section Design of Year 7 Phase B Consisting of 480 Sequences Planned for Summer/Fall 2018

19 QA/QC Once Created, All Maps Are Reviewed on an Individual Basis for the Following Key Components Does the Design: Impede Water Flow to Any Given Area? Account for Topography and Water Drainage? Account for Future Section Flushing Requirements? Achieve the Necessary Velocities to Clean the Pipes Without Exceeding Design Constraints? Prevent Excessive Use of Multiple Hydrants/Valves? Is the Design: Able to be Flushed in a Single Day (Per Section)? Easy to Interpret and Follow?

20 UDF Implementation Schedule Considerations Schedule Winter Potential Freezing Within Next 24 hours Drought and Water Restrictions Public Perception Peak Demand WTP Overtime Realistic Expectations Understand Sensitive Customers Hospitals Dialysis Centers Assisted Living Facilities Bottling Companies

21 UDF Implementation Contractor Selection and Inspections Contractor Selection Experience Implementing UDF Water System Maintenance Knowledge to Make Field and Program Adjustments Years in Business Crews Available Equipment Experience Clause, Requirements Inspection Services Daily Review Single Record of Completed Work Making Field Decisions on Changes Follow-Up on Assets Restoration

22 UDF Implementation Water Quality Sampling Samples Collected Pre- and Post-Flushing No More Than 2 Weeks Before and After Critical Sampling Can Include Historical Water Complaint Locations Field Kits with Periodic Bottle Tests Results Should Show: Increased Disinfectant Residual Large Drop in Turbidity Reduction in Iron, etc.

23 Uni-Directional Flushing Discharge Location Review Field Verify All Discharge Locations, Prior to Flushing

24 UDF Implementation Public and Customer Notifications Color Coded Flushing Scheduled Maps, Posted on Website Initial Notifications by Mail Notifying Street Signs Posted Prior to Flushing Customer Hotline Door Hangers Postcards within 2 Weeks of Flushing Contain FAQs Contact with Questions

25 Lessons Learned Maintain 5-8 FPS in Pipes Smaller than 16 Throttle Hydrant Discharge Last Sequence of Each Section Should Return Valves to Open Position Required Velocities in Smaller Lines Equate to Lower (Non Scour) Velocities in Larger Lines i.e., 550 gpm Flushes a 6 Dia. Pipe at 6 FPS, but Flushes a 12 Dia. Pipe at 1 FPS Watch Flushing Hydrant Discharge

26 Lessons Learned Isolating an Entire Section then Flushing Individual Sequences Saves Valves from Being Operated for Each Sequence Use Flush Times as a Guideline to Achieve Proper Turnover The Contractor Should Not Continue to Flush Sequentially within a Zone If an Acceptable Turbidity is Not Achieved In Many Cases, the Turbid Water in the First Sequence will be Carried through to the Rest of the Sequences, Leading to Longer Required Flush Times Flush to Reach Target Turbidity Add Valves and Hydrants to Create More Efficient Sequences

27 UDF Program Benefits Proper Planning Can Reduce Amount of Flushing Water vs. Spot Flushing Significant Improvement in Water Quality Lower DBPs Decrease in Customer Complaints Due to Taste, Color, and Odor = Improved Customer Relations Can Incorporate into Valve and Hydrant Maintenance Program Valuable Updates to GIS, Supporting Models, Asset Management Programs Identification of Future Maintenance and System Improvements

28 Uni-Directional Flushing QUESTIONS & ANSWERS