Greensboro s Confirmation: Documenting I/I Reduction in North Buffalo Basin with Post Rehabilitation Flow Monitoring

Transcription

1 Greensboro s Confirmation: Documenting I/I Reduction in North Buffalo Basin with Post Rehabilitation Flow Monitoring November 2017 Chris Nesbit, PE, BCEE, Meredith Miller, PE, CDM Smith and Robbie Bald, PE City of Greensboro October 2017

2 Agenda Flow Monitoring and Prioritization (2011) SSES and Rehabilitation ( ) Post Rehabilitation Flow Monitoring Analysis (2016) Conclusions Kentucky-Tennessee Water Professionals Conference

3 Flow Monitoring and Prioritization (2011)

4 Performed Flow Monitoring Analysis in 2011 to Identify Areas with High I/I in the Upper North Buffalo Drainage Basin 4

5 Location of SSOs in the Study Area from 2006 to 2011 SSOs from 2006 to SSOs rainfall related 5

6 A Wet-Weather Flow Hydrograph Is Composed of Several Wastewater Flow Components Wastewater Flows are composed of: Base wastewater flow (BWWF) Groundwater Infiltration (GWI) Rain Dependent Infiltration/Inflow (RDI/I) FLOW TIME

7 Prioritizing Sewersheds Based on Peak and Volume of I/I Priority 1 - Sewersheds 1, 6, 9, 13, 14, 17, and 18 Priority 2 Sewersheds 2, 7, 8, 12, and 21 7

8 Of the 480,000 lf of sewer, 213,000 was recommended for CCTV inspection 136,000 lf in Priority 1 and 77,000 lf in Priority 2 8

9 SSES and Rehabilitation (2013 to 2015)

10 Perform SSES and Rehabilitation to Reduce I/I and Control SSOs Priority 1 Sewersheds (red) CCTV d 135,000 feet in Rehabilitation in Priority 2 Sewersheds (orange) CCTV d 70,000 feet in Rehabilitation in Post Rehab Flow Monitoring of Priority 1 in March-April

11 SSES Identified Various Structural & O&M Defects In the Sewersheds that would lead to I/I 11

12 Few Active Infiltration Defects Observed via CCTV Shows Need for Flow Monitoring to Document I/I Table1 Priority 1 Sewersheds, Number of CCTV Defects Sewershed Number of Structural Defects (#) Joint Surface Defects Structura Infiltratio Obstruction Cracks Fractures Broken Holes Deformed Collapsed Offset Damage (Sags) l Defects Deposits Roots n s Defects Inspected Sewershed Sewershed Sewershed Sewershed Sewershed Sewershed Sewershed Number of Pipes with Other Total Number of Number of Operations and Maintenance Defects Total Number of O&M Total Number of Pipes Number of Pipes with No Defects 12

13 Comprehensive Rehabilitation Performed for Majority of Pipes in Priority 1 and 2 Sewersheds Priority 1 Sewersheds CCTV d 135,000 ft., Recommended Rehabilitation 112,000 ft. Recommended Rehabilitation Pipe Length (ft.) Percent of Total Length CIPP 31,170 28% Sliplining 59,960 51% Pipe Bursting 22,337 20% Open Cut 1,547 1% Total 112, % Priority 2 Sewersheds - CCTV d 70,000 ft., Recommended Rehabilitation for 62,000 ft. Recommended Rehabilitation Pipe Length (ft.) Percent of Total Length CIPP 17,377 28% Sliplining 38,956 62% Pipe Bursting 4,046 6% Open Cut 491 1% Other Rehab Method 1 1,787 3% Total 62, % 1 Other Rehab Methods include Heavy Cleaning and Re- CCTV, Point Repair Only, Lateral Rehabilitation Only. 13

14 Post Rehabilitation Flow Monitoring Analysis

15 Goal: Document Reductions in Volume and Peak I/I for Pre to Post-Flow Monitoring Data Phase 1 Historic Meter Data 2015 and 2010 master plan flow monitoring data Phase 2 CDM Smith Sub-basin Meter Data 2011 and 2016 pre- and postrehabilitation flow monitoring data 15

16 Phase 1: Historic Flow Monitoring Data Flow Monitoring Data March 7, 2010 June 20, 2010 January 13, 2015 May 18, 2015 Incremental Areas in the 200,000 ft. 16

17 Preand Post- Rehab Basins Post Rehabilitation Master Plan Flow Monitors NB 16 - Control NB 20 - Pre and Post Rehabilitation Analysis 35% of pipe upstream of NB 20 was rehabilitated. Flow Monitor Total Upstrea m Pipe Length (ft.) Total Rehabili tated Pipe Length (ft.) Percent of Pipe Length Rehabili tated Upstrea m of Monitor Rehab NB ,000 67,000 35% Control NB , % 17

18 Post Rehabilitation 2016 CDM Smith Flow Monitoring Data Control FM 2 Flow Monitors Downstream of Rehabilitated Sewersheds: FM 9, FM 14, and FM 18 Preand Post- Rehab Basins Flow Monit or Total Upstream Pipe Length (ft.) Total Rehabilit ated Pipe Length (ft.) Percent of Pipe Length Rehabilit ated Upstrea m of Monitor Control FM 2 10, % Rehab FM 9 62,100 41,846 67% Rehab FM 14 12,200 10,217 84% Rehab FM 18 16,500 13,664 83% 18

19 Hydrograph Decomposition was performed on Greensboro Flow Data to Determine the Portion of Flow Hydrograph Attributed to RDI/I Average Weekday Dry- Weather Flow = mgd Peak Hour Flow Rate = 0.17 mgd Total RDI/I entering system on May 2 event upstream of Flow Monitor 2 = 110,500 gallons 19

20 R-Value is the Fraction of Rainfall over a Sewershed that Enters the Sanitary Sewer as RDI/I Table 1. Pre- Rehabilitation R-Values for the Phase 2 (CDM Smith) Flow Meters Pre- and Post-Rehab Basins Flow Monitor Total Upstream Sewered Area (ac) Pre-Rehabilitation R-value (%) 2/28/2011 3/6/2011 3/9/2011 3/23/2011 3/30/2011 4/16/2011 Control FM % 4.16% 4.41% 0.71% 4.37% 0.52% Rehab FM % 3.89% 6.37% 0.88% 4.41% 2.57% Rehab FM % 5.16% 6.59% 1.69% 6.63% 2.92% Rehab FM % 4.77% 6.16% 1.74% 6.42% 2.92% Table 2. Post - Rehabilitation R-Values for the Phase 2 (CDM Smith) Flow Meters Pre- and Post- Rehab Basins Flow Monitor Total Upstream Sewered Area (ac) Post-Rehabilitation R-value (%) 2/22/2016 3/27/2016 3/28/2016 4/22/2016 4/27/2016 5/2/2016 5/5/2026 5/12/2016 Control FM % 0.75% 3.21% 1.34% 0.53% 2.85% 5.00% 3.89% Rehab FM % 0.54% 2.51% 0.33% 0.25% 2.91% 5.09% 2.35% Rehab FM % 0.52% 1.00% 0.53% 0.28% 0.97% 1.96% 1.16% Rehab 20 FM % 1.11% 6.41% 0.94% 0.56% 2017 Annual NC AWWA-WEA 1.73% Conference 3.76% N/A1

21 A Ratio of RDI/I Peak Flow Rate to Peak Rainfall Rate was used to Determine Impact of Rehab on Reducing Peak RDI/I Flows Table 1. Pre- Rehabilitation Peak Flow Ratios for the Phase 2 (CDM Smith) Flow Meters Pre- and Post-Rehab Basins Flow Monitor Total Upstream Sewered Area (ac) Pre-Rehabilitation Peak Flow Ratio (GPD/AC/in/hr) 2/28/2011 3/6/2011 3/9/2011 3/23/2011 3/30/2011 4/16/2011 Control FM2 69 4,141 9,802 4,289 1,337 8,789 13,410 Rehab FM ,635 6,554 8,003 2,271 7,039 17,825 Rehab FM ,174 12,502 11,488 3,914 14,397 35,338 Rehab FM ,399 19,735 16,322 3,025 14,604 39,945 Table 2. Post-Rehabilitation Peak Flow Ratios for the Phase 2 (CDM Smith) Flow Meters Pre- and Post- Rehab Basins Flow Monitor Total Upstream Sewered Area (ac) 2/22/ /27/201 6 Post-Rehabilitation Peak Flow Ratio (GPD/AC/in/hr) 3/28/ /22/ /27/ /2/2016 5/5/2026 5/12/201 6 Control FM2 69 9,511 4,314 8,816 4,451 2,272 3,851 6,896 2,068 Rehab FM ,981 1,554 3,744 1,375 1,284 3,308 5,277 1,344 Rehab FM , ,408 1, ,123 2, Rehab 21 FM ,118 3,716 14,479 3,091 3, Annual 4,288 NC AWWA-WEA 7,344 Conference N/A 1

22 Linear Regression Analysis is Used to Compare the Pre- and Post Rehabilitation Monitoring Volume of RDII (R-Value) Sewershed NB20 vs. Control NB16 3.0% R Value for Sewershed NB20 2.5% 2.0% 1.5% 1.0% y = x R² = y = x R² = % 0.0% 0.0% 1.0% 2.0% 3.0% 4.0% 5.0% 6.0% 7.0% 8.0% R Value for Control NB16 22

23 Historic Meter Data Rehabilitated Basin RDI/I Volume NB20 RDI/I Peak Flow NB20 Control Basin NB16 NB16 Percent of Pipe Length Rehabilitated Upstream of Monitor 35% 35% 23 Pre-Rehabilitation Slope Post-Rehabilitation Slope Percent I/I Reduction 53% 39% R Value for Sewershed NB20 3.0% 2.5% 2.0% 1.5% 1.0% 0.5% Volume of RDII (R-Value) Sewershed NB20 vs. Control NB y = x R² = y = x R² = % 0.0% 1.0% 2.0% 3.0% 4.0% 5.0% 6.0% 7.0% 8.0% R Value for Control NB16 Peak Flow Ratio (gpd/ac/in/hr) for Sewershed NB 20 6,000 5,000 4,000 3,000 2,000 1,000 0 y = x R² = Peak RDII NB20 vs. Control NB y = x R² = ,000 4,000 6,000 8,000 10,000 12,000 14,000 16,000 18,000 Peak Flow Ratio (gpd/ac/in/hr) for Control NB16

24 CDM Smith Post Rehabilitation Analysis Results FM 9 R Value for Sewershed FM9 8.0% 7.0% 6.0% 5.0% 4.0% 3.0% 2.0% 1.0% y = x R² = Volume of RDII (R-Value) Sewershed FM9 vs. Control FM y = x R² = % 0.0% 2.0% 4.0% 6.0% 8.0% 10.0% 12.0% R Value for Control FM2 Peak Flow Ratio (gpd/ac/in/hr) for Sewershed FM ,000 18,000 16,000 14,000 12,000 10,000 8,000 6,000 4,000 2,000 0 Peak RDII FM9 vs. Control FM y = x R² = y = x R² = ,000 4,000 6,000 8,000 10,000 12,000 14,000 16,000 Peak Flow Ratio (gpd/ac/in/hr) for Control FM2 RDI/I Volume Rehabilitated Basin FM9 FM9 Control Basin FM2 FM2 Percent of Pipe Length Rehabilitated Upstream of Monitor RDI/I Peak Flow 67% 67% Pre-Rehabilitation Slope Post-Rehabilitation Slope Percent I/I Reduction 44% 54%

25 CDM Smith Post Rehabilitation Analysis Results - FM 14 R Value for Sewershed FM14 7.0% 6.0% 5.0% 4.0% 3.0% 2.0% 1.0% y = x R² = Volume of RDII (R-Value) Sewershed FM14 vs. Control FM y = x R² = Peak Flow Ratio (gpd/ac/in/hr) for Sewershed FM14 0.0% 0.0% 2.0% 4.0% 6.0% 8.0% 10.0% 12.0% 25 40,000 35,000 30,000 25,000 20,000 15,000 10,000 5,000 0 R Value for Control FM2 Peak RDII FM14 vs. Control FM y = x R² = y = x R² = ,000 4,000 6,000 8,000 10,000 12,000 14,000 16,000 Peak Flow Ratio (gpd/ac/in/hr) for Control FM2 RDI/I Volume RDI/I Peak Flow FM14 Rehabilitated Basin FM14 Control Basin FM2 FM2 Percent of Pipe Length Rehabilitated Upstream of Monitor 84% 84% Pre-Rehabilitation Slope Post-Rehabilitation Slope Percent I/I Reduction 2017 Annual NC AWWA-WEA 83% Conference 88%

26 CDM Smith Post Rehabilitation Analysis Results FM 18 R Value for Sewershed FM18 Peak Flow Ratio (gpd/ac/in/hr) for Sewershed FM % 9.0% 8.0% 7.0% 6.0% 5.0% 4.0% 3.0% 2.0% 1.0% 45,000 40,000 35,000 30,000 25,000 20,000 15,000 10,000 5,000 0 y = x R² = Volume of RDII (R-Value) Sewershed FM18 vs. Control FM Peak RDII FM18 vs. Control FM y = x R² = % 0.0% 2.0% 4.0% 6.0% 8.0% 10.0% 12.0% R Value for Control FM2 y = x R² = y = x R² = ,000 4,000 6,000 8,000 10,000 12,000 14,000 16,000 Peak Flow Ratio (gpd/ac/in/hr) for Control FM2 RDI/I Volume Rehabilitated Basin FM18 Control Basin FM2 FM2 Percent of Pipe Length Rehabilitated Upstream of Monitor RDI/I Peak Flow FM18 83% 83% Pre-Rehabilitation Slope Post-Rehabilitation Slope Percent I/I Reduction 35% 57%

27 The City of Greensboro was able to Achieve a % Reduction in I/I Entering Their Collection System by Performing Comprehensive Rehabilitation Rehabilitated Basin RDI/I Volume RDI/I Peak Flow RDI/I Volume RDI/I Peak Flow RDI/I Volume RDI/I Peak Flow RDI/I Volume RDI/I Peak Flow FM9 FM9 FM14 FM14 FM18 FM18 NB20 NB20 Control Basin FM2 FM2 FM2 FM2 FM2 FM2 NB16 NB16 Percent of Pipe Length Rehabilitated Upstream of Monitor 67% 67% 84% 84% 83% 83% 35% 35% Pre-Rehabilitation Slope Post-Rehabilitation Slope Percent I/I Reduction 27 44% 54% 83% 88% 35% 57% 53% 39%

28 Conclusions

29 Conclusions Flow monitoring of small sewersheds (15,000 35,000 lf range) prioritizes areas for comprehensive rehabilitation to reduce I/I. Post rehabilitation flow monitoring of rehabilitated sewersheds is necessary to effectively document I/I reduction. The key to effective post rehabilitation flow monitoring is to monitor a control area where no rehabilitation is performed and use linear regression analysis. Greensboro documented reductions in peak flow from 39% to 88% and reductions in I/I volume from 35% to 83%. No obvious correlation as to why some mini-basins achieved higher percentage reductions in I/I. 29

30 Conclusions Although monitoring the sub-basin where rehabilitation is performed is ideal, monitors of a larger basin area can be utilized as long as a significant percentage (in this case 35%) of the footage upstream was rehabilitated. 30

31 November 2017 Contact Us Chris Nesbit October 2017