Wilmette - Background

Transcription

1 Reducing Basement Backups through Intergovernmental Cooperation and Design-Build Presented By Michael N. Young, P.E. Brigitte Ann Berger, P.E. Wilmette - Background North Shore Suburb of Chicago 5 Square Miles / Population 27,000 Fully Developed East Half: Combined Sewers (late 1800 s 1930 s) West Half: Separate Sewers (1940 s 1970 s) Sanitary and Combined Flows Treated by MWRD Separate Storm System North Branch Chicago River 1

2 Wilmette Sewer System Wilmette Sewer System Investment $77 Million Since Early 1990 s Combined Sewer Area Relief sewers, drainage berms and inlet restrictors Separate Sewer Area Relief sewers and flow reduction Second stormwater outfall and backup generator Village Wide Maintenance (On-Going) Sewer cleaning, televising and lining 2

3 Storm Events Past 35 Years Resident Survey Basement Backups 3

4 Sanitary System Focus Village Board Prioritized Separate Sanitary System Why? Federal and State Laws address backups and SSOs 3x more residents reported structure damage from sanitary backups than street flooding Flow metering and modeling System bottlenecks Evidence of downstream control from MWRD system Selected RJN in Early 2012 Basement Backups Survey Findings Regional and severe backups in major events Isolated backups in moderate events Potential Cause Insufficient capacity? Excess flow? Downstream limitations? All of the above? 4

5 Initial Study Existing Data Reports Flow monitoring Backup history Detailed Hydraulic Model Utilize previous flow monitoring Rim and invert survey of all manholes Calibration Identify areas of concern Evaluate alternatives Initial Study Recommendations Address Back pitched Sewer Address Two Local Hydraulic Bottlenecks Flow Reduction Manhole inspection and rehabilitation Continue sewer televising and lining Kenilworth Gardens SSES More Detailed Evaluation of Harms Basin Additional long-term flow monitoring Better understanding of downstream control Quantify storage needs Storage location options 5

6 Wilmette Harms Basin Study Longer-Term Flow Monitoring Various size rain events Evidence of downstream control Improvement Options Flow reduction Public Private Storage options Volume required? Side stream sewers in ROW Large scale location options Major Rain Event 6

7 Model Target Event Conclusions and Recommendations Conclusions Significant reverse flow Significant excess flow Storage and/or flow reduction Recommendations Backflow prevention Pump over? Storage Volume? Location? Flow reduction 7

8 Sizing Storage Hydraulic Model Number of Properties Subject to Backup by Alternative Storm Event Average # of Events Per Year Existing Condition 1.5 MG 3.0 MG 4.5 MG 5.5 MG 8.0 MG 11.0 MG 9.0 MG (P) 2 Month Month Year Year 0.5 1, Year 0.2 1,669 1,626 1,651 1, Year 0.1 1,711 1,680 1,679 1,679 1,553 1,228 1,213 1, Year ,711 1,700 1,690 1,687 1,678 1,489 1,374 1, Year ,711 1,711 1,708 1,690 1,690 1,689 1,467 1, Year ,712 1,712 1,712 1,712 1,712 1,695 1,681 1,700 Project Stakeholders Village Residents 2008 and 2011 rain events April and June 2013 rain events Village Board July 2013 Presentation Small scale capacity improvements Flow reduction Harms Road Storage MWRD (Regulatory) Storage Location Property Owner 8

9 MWRD Conceptual Approval Present Flow Monitoring Data April and June 2013 Reverse flow Backflow Prevention Pump Over Lift Station Local precedent Limited to 150 gpcpd Flow ~1 mgd 5.5 MG Storage Flow Reduction Program Selecting Storage Location Parameters 5.5 million gallons Near MWRD interceptor Large site Options Golf course Private HS field IDOT cloverleaf West Park Selected West Park Site (Park District) 9

10 Park District Coordination October 2013 Park District Board Presentation Spring flooding Project concept Construction impact Post-construction use Negotiations Park District Conditions New turf field Village partial cover Start October 2014 Finish November 2015 Tight Schedule Park District Conditions Construction Start: 6 Months Just Starting Preliminary Design Standard Design-Bid-Build Design Permits Bidding Contract Award Feasible? 10

11 Potential Design-Build Schedule Phase Storm Relocation and Excavation Easier Design Partial MWRD Permit? Phase Tank and Backfill Building and Mechanical Electrical and Controls Park District Field Detailed Design During Phase 1 MWRD Permit Over Winter 6 Months to Construction April and May Preliminary Design Meet with MWRD June and July Set Plan with Village Start 100% Phase 1 and 40% Phase 2 Plans August Set Guaranteed Maximum Price Approve Village Park District IGA September Village Board Approves Design-Build Contract 11

12 Groundbreaking Guaranteed Maximum Price Set Prices Bid Sub Work Phase 1 Phase 2 Allowances Overhead and Profit Contingency Engineering General Conditions Original Contract Amount: $15,024,432 12

13 Advantages of Design-Build Accelerated Schedule Guaranteed Maximum Price Early Cost Certainty Cost Containment Contractor Flexibility Qualifications Experience Specialists Keys to Design-Build Good Project Manager with Expertise Mike Henderson Good Contractor Partner Boller Construction Open Relationship with Owner Park District and Village Open book (financial) Regular meetings Early Communication with Permit Agencies 13

14 Backflow Prevention/Pump Over LS Check Valve on 36 Interceptor 1 MGD Pump Station (Flow Set by MWRD) Excavation and Backfill Quotes from Three Qualified Subcontractors Start in October ,000 Cubic Yards Excavated 15,000 Cubic Yards Stockpiled to East Up to 500 Trucks Per Day Ramps to Lower Level Finished in December Mud Slab Start Backfill in June 2015 Finish Backfill in August 14

15 Storage Tank 5.5 MG Cast-In-Place Concrete Tank 310 Long x 168 Wide x 22 High 24 Base Slab Checkerboard Pours Sloped to Center Trough 24 Walls Poured in 20 Sections 98 Columns (14 x 7 Grid) Elevated 12 Drop Slab and 18 Top Slab Top of Tank 4 Below Field Turf Account for Weight Above Sewer Overflow to Tank (No Mechanical / Electrical) Lift Station 24 Sewer Between Interceptor and Tank Lift Station Structures Manhole on 24 sewer Wet well Valve vault Three Pump Station Pump out Mixing Flushing Add clear water in tank for final flush All Drains to Sump Pump in Wet Well 15

16 Control Building Backup Generator Odor Control Unit System Controls Automatic Operation Odor control Mixing Pump out Flushing Sump pump Nuisance Storms Phase 1 Original Site 16

17 Phase 1 Storm Sewer Relocate Phase 1 - Excavation 17

18 Phase 1 - Excavation Phase 1 - Excavation 18

19 Phase 1 Mud Slab Meanwhile... Phase 2 Design Village Approval Park District Approval MWRD Permit Phase 2 Bidding Three qualified subcontractors Mechanical HVAC Electrical Miscellaneous 19

20 Can We Start Phase 2 Early? No It Is Winter in Chicago! 20

21 Phase 2 Storage Tank Phase 2 Storage Tank 21

22 Phase 2 Storage Tank Phase 2 Storage Tank 22

23 Phase 2 Storage Tank Wettest June on Record 9.6 of Rain Finishing Tank Starting Backfill Settling Concerns Geotechnical Undercut Initial CA-7 8 Lifts 95% Proctor Lime Stabilization Settlement Tests 23

24 Phase 2 Backfill Phase 2 Backfill 24

25 August 2015 Coordination Contract Deadlines Park District Access September 15: Substantial Completion September 1: Early Completion Bonus All Construction Under Turf Field Complete Tank Backfill to Specific Grade Piping and Conduit Many Simultaneous Disciplines Access to Tank, Building and Lift Station Substantial Completion 25

26 Phase 2 Lift Station Phase 2 Building 26

27 Phase 2 Odor Control Phase 2 Electrical and Controls 27

28 Phase 2 Final Completion Final Cost Bid Sub Work Phase 2 Savings Returned to Village Allowances Increase in Lime Stabilization Decrease in Other Items Contingency Early Completion Bonus Final Payment Amount: $14,493,490 Project Savings: $530,942 28

29 Project Purpose Address Basement Backups! Items Addressed Stop reverse flow Maximize allowable pump over Store remaining Village excess flow Remaining Items of Concern Excess flow Capacity of sewers to convey flow to tank How Does It Work? Original Level of Protection 29

30 Updated Level of Protection July 23, 2016 Rain Event 6.05 inches in ~8 hours (100-year) Two Waves 2.91 in 1.25 hours 3.14 in 4 hours Project Status Pump over LS: Operated for 18 hours Flow Into Storage: 10 Hours Maximum Depth: 13 feet Total Volume: 4.5 million gallons Time to Empty Tank: 68 hours 30

31 Findings and Conclusions Backup Calls to Village 2013: 150 (25-year event) 2016: 66 (100-year event) Backflow Valve and POLS: Operated as Designed Storage Tank: Operated as Designed Remaining Issues: Flow exceed sewer capacity Surface flooding Additional I/I Reduction Required Flow Reduction Completed Comprehensive manhole rehabilitation Ongoing Sewer lining Planned Stormwater Cross Connections Laterals Private Sector 31

32 Final Thoughts Flow Monitoring and Modeling Stakeholder Communication Consider Design-Build Use Storage with Flow Reduction Time Lapse Video!? 32