Dan Ott Managing Engineer Collection System Johnson County Wastewater, KS and Rick Nelson CH2M HILL

Transcription

1 Dan Ott Managing Engineer Collection System Johnson County Wastewater, KS and Rick Nelson CH2M HILL

2 What is JCW s strategy for meeting wet weather performance targets? SSO s Basement Back-ups

3 Serving Johnson County, Kansas Located in south west portion of Kansas City metro. Serves over 500,000 people Employs ~ 200 people Operates & Maintains: 2,200 miles of sewer pipe 55,000 manholes 32 pump stations 4 peak excess flow treatment facilities (PEFTFs) 7 conventional treatment plants 70 MGD total treatment capacity

4 Early 1980 s Over 300 Wet Weather Backups per year (30 per 100 miles of sewer) Mid 1980 s Early 1990 s I/I Removal and System Improvements $56 Million Project (1990 $) Included $11 Million in Private I/I Removal 16,000 Private I/I Sources Removed 50% reduction in I/I O&M commitment to improved system maintenance

5 Year Miles of Sewer Dry Weather Backups Wet Weather Backups Improvement was achieved by focusing efforts in the following areas I/I reduction Capacity enhancement System maintenance (O&M) Backup Prevention Program (BUPP)

6 Aging System.including private building service lines Peak Flows Older watersheds have projected peak to average flows of 10 to 1 Capacity Issues Locations of chronic wet weather overload still exist Continuous Improvement Cost effectiveness of I/I reduction in the public and private sector needed refinement to properly evaluate alternatives

7 Response to an EPA 308(a) data request with a focus on continuing to improve system performance. JCW s current projects & programs focus on further definition of solution alternatives Key Questions: What is the right balance (LOS)? What is a cost effective strategy (CEA)? How much I/I removal is feasible & sustainable? What private I/I removal is optimal? Building sources Lateral sources Sustainable Wet-Weather Flow Management

8 Public & Private I/I Removal Traditional + Service Laterals Voluntary Private I/I Rehab Funded by JCW Effective Public Outreach Program Evaluated Various Rehabilitation Strategies Detailed pre-rehab & post-rehab evaluation Rehabilitation Strategy Public Sewers & Manholes Private Service Lines Private Building Sources Everything X X X Public Only Private Only X X Typical Comprehensive Typical Comprehensive + Lower Lateral (LL) X X (selected) X (selected) X (lower) X X Control

9 Flow Data Analysis Comprehensive review/selection of flow analysis methods to evaluate pre- and post-rehabilitation flows I/I Source Quantification I/I defect source quantification completed for pre- and postrehabilitation conditions to assess source flow estimates based on measured I/I at each flow meter Service Line & Sump Pump Flow Monitoring Cost Tracking Construction costs by strategy area and asset type were tracked to evaluate cost per unit I/I removal by strategy and asset type.

10 calculate peak total flow rate calculate peak total flow volume relationship to rainfall defined Inflow Coefficient (current JCW) RTK (US EPA SSO Tool Box) Predictive equationlinear regression (Kurz) Additional Outputs calculates total RDII flow volume 2.5 calculates peak RDII flow rate Includes simple Q to i chart differentiates between infiltration and inflow Estimates annual volume of I/I 95% CONFIDENCE 95% CONFIDENCE 24-HR INFILTRATION/INFLOW VOLUME (mg) E-11 Base 24-Hr I/I HOUR RAINFALL (inches) 24-HR RAIN I/I 24-hr best fit line REMAINING CAP.(I/I)

11 Monitored Flows 33% 31% I/I Quantification and Costing Tool (defect database) 1% 35% Select Sources for Rehab Mains Manhole Lateral Building I/I Source Data

12 Sump Pump Flow Monitoring 35 flow meters Service Lateral 9 flow meters 4 Categories 1 Laterals in good condition, no suspect foundation drain 2 Laterals in good condition with suspect foundation drain 3 Laterals in good condition with visible connection near foundation 4- Lateral with defects, no connection 12

13 4.5 gpm 13

14 Everything maximum is 55% Typical is 28% Typical+LL is 31% Note: Private is repair of all building sources and all laterals (regardless of defects) and Public is repair of all manholes and main lines (regardless of defects)

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17 Note comparison of Typical and Typ+LL Little additional I/I removal by including all LL but a much more cost. Therefore, focus on DEFECTIVE (cost-effective) laterals, not all laterals.

18 I/I can be cost-effectively reduced. Requires proper planning and execution to develop best strategy Reasonable predictions of I/I removal and costs can now be made to manage I/I reduction The most effective I/I reduction strategy would address both the private and public sectors Lateral rehabilitation should focus on cost-effective lateral repairs only Need to conduct further evaluation of revised strategy

19 Long term system-wide flow monitoring, modeling and data management system. Revised public and private sector implementation plans Integrate public sector rehabilitation strategy into existing system maintenance and asset management programs. Validate updated strategy by conducting proposed I/I reduction strategy in other priority basins. Ongoing efforts to optimize system improvements

20 Dan Ott, P.E. Managing Engineer Collection System Johnson County Wastewater Johnson County, KS Rick Nelson, P.E. Global Conveyance Service Team Lead CH2M