Rehabilitating a 105-inch Interceptor Innovations and Lessons Learned

Transcription

1 Rehabilitating a 105-inch Interceptor Innovations and Lessons Learned Pipe User Group Northern California March 13, 2018 Tim Karlstrand and Gary Warren

2 Agenda System Overview Project Need Video Lessons Learned Technology Evaluation Hydraulic Analysis Cost Savings Odor Management Reducing Community Impacts Phase 1 Lessons Learned 2

3 East Bay Municipal Utility District Overview EBMUD provides wastewater treatment for 680,000 of its 1.3 million water customers ( west of hills ) Wastewater is collected in large diameter interceptors from seven satellite communities Alameda Albany Berkeley Emeryville Oakland Piedmont Stege Sanitary District

4 Wastewater Flow Range Wastewater flow from satellites (MGD = million gallons per day) Average annual flow = 50 MGD Peak wet weather = 415 MGD (at MWWTP) Peak wet weather = 700 MGD (system-wide) Primary treatment = 320 MGD (max) Secondary treatment = 168 MGD (max) Significant peaking factor is a key challenge

5 Wastewater Interceptor System EBMUD 29 miles of gravity interceptors 8 miles of force mains 15 pump stations MWWTP, plus 3 WWFs Satellites ~1,600 miles of regional collection system ~1,600 miles of private sewer laterals

6 Background Project Need Corrosion of the South Interceptor is active and rehabilitation is necessary Due to high levels of hydrogen sulfide 6

7 Background Capital Improvement Program 7

8 CIP Update Four Phases of 3 rd Street Four phases of work over 8+ years Project Segment Total Project Cost 3rd St Rehab Phase 1* $9.0M 3rd St Rehab Phase 2 $24.9M Special Structures Rehab $8.3M Embarcadero Rehab $12.8M Total $55.0M *3 rd St Rehab Phase 1 construction estimate is $6.8M 8

9 Video California Association of Sanitation Agencies (CASA) 2017 award for Outstanding Capital Project 9

10 Phase 1 4 Project Scope Phase 1 Phase 2 Phase 4 (Embarcadero) *Phase 3 not shown (Special Structures) 10

11 Constraint Analysis Flow Dry weather construction No pumped bypass (of interceptor flow) Tributary flow management Daily sediment deposition Capacity Reliability during construction Method cannot significantly restrict capacity during nonwork hours Rehabilitated pipe New profile cannot significantly reduce capacity 11

12 Lessons Learned Damage Repair Project 1993 Danby Rigid sheets Grouted in place No repairs needed 12

13 Lessons Learned Wood St Projects 2001 Linabond Flexible sheets glued with structural polymer Many repairs needed due to hydrostatic failures Linabond Rigid sheets glued with structural polymer 13

14 Technology Evaluation Overview 10 methods evaluated, 5 screened as feasible Alternative Project Installation Danby Crown Linabond Post Construction Manned Inspection Repairs To-date SD-205A None SD *, 2017** SD n/a n/a Ameron SD None Hobas Sekisui & Danby Spiral Numerous Waterside Large Diameter Large Diameter Numerous Some?? * individual repairs, 1567 square feet of repairs. ** 17 9 repair of repairs 14

15 Rehabilitation Systems Slipliner Detail (complete liner) diameter 15

16 Rehabilitation Systems Spiral Liner (complete liner) diameter 16

17 Rehabilitation Systems Crown Liner Manufacturer Danby specified No known equal Linabond not be specified Higher cost Longer schedule Quality concerns by Linabond Lower life cycle Unresolved safety concern Ameron Arrow-Lock specified for repairs 17

18 Rehabilitation System Evaluating Alternatives (Operations) Alternative Operations Impacts* Remote Plant 1. Crown Lining Medium Medium 2. Slip Lining Low Low 3. Spiral-wound Liner Medium Medium 18

19 Rehabilitation System Evaluating Alternatives (Cost) Item Number of Potential Bidders Historic Bid Spread* Alternative Crown Liner Slip Lining Spiral Liner % 10-25% n/a Marketplace Volatility High Low Medium *Actual bid range $ M, Engr Est $5.9M 19

20 Rehabilitation Systems Crown Liner Detail (Ph1 Selected Danby) 101 diameter Lower Termination Level Platform 20

21 Flow Management Strategy Extended Work Hours to Lower Cost and Community Impacts Weir Wall Schematic of In-System Storage 21

22 Flow Management and Working Hours Control Gate Location 22

23 Flow Management and Working Hours Control Gate Layout District purchased standard wastewater control gate District designing the bulkhead wall Contractor got O&M training District tested before rehab starts 23

24 Flow Management and Working Hours Remote Operations Impacts PS-H Off PS-H On South Interceptor Diurnal Water Level Possible Work Hours Platform Level Flow modeling in work area 24

25 Flow Management and Working Hours Plant Operations Impacts Projected Storage at Plant ~7 MG South Interceptor Projected Flow at IPS Total Projected Flow at IPS Assumed Plant Base Flow Rate 25

26 Flow Management and Working Hours Comparison to Wood St Work Hours Scenario Available Work Hours Productivity Work Hours Wood St rd St 10 8 Productivity Improvement % Potential Cost Savings -- $0.5-1 million Potential Schedule Savings months Extended work hours due to control gate Cost of control gate assembly ~$100K 26

27 Safety and Odor Odor Treatment System Study Overview Feed hypo from SAC Dechlor at 1 to 4 gpm Goal is to reduce sulfide loading and release during construction Collect liquid and gas sulfide data 27

28 Safety and Odor Odor Treatment System Initial Liquid Results Grab samples taken at S54 and S60 Avg. Sulfide (mg/l) Baseline Week 1 Baseline Week 2 1GPM Hypo 3 GPM Hypo S S Conclusions Clear reduction in liquid sulfides with 3 GPM hypo feed 28

29 Safety and Odor Odor Treatment System Baseline Gas Results 29

30 Safety and Odor Odor Treatment System Initial Gas Results Average Value During Work Times Reduction from Baseline 4AM-4PM ppm Baseline % 1 GPM % 3 GPM % Average during 3 GPM hypo feed -> 58% reduction in H 2 S 30

31 Safety and Odor Odor Treatment System Contractor Scope Contractor operates hypo feed system Cost Savings: Dosing 3 gpm is $108K versus $325K for odor scrubber Contractor provides redundant odor control system in work area 31

32 Challenges/Risks Community/Business Risk Initial Risk Level Mitigations Residual Risk Level Residential neighborhood construction impacts Shift work hours to daytime with control gate (working hours and traffic on narrow streets) High Add temporary manhole outside residential area (inside Post Office) Limit work hours for staging and access in residential area Low Design traffic controls to minimize traffic impacts Public upset about construction impacts (noise, light, and odor) Medium Clearly define contractor requirements for controlling construction impacts to threshold values Low Measure and enforce requirements Public upset about displaced street parking and towing Medium Provide resident notice about no parking via mailers and changeable message signs Secure an alternative parking area for residents, if needed Low Impact to Post Office operations caused by traffic disruption High Add new manhole outside roadway Limit work hours for manholes in the path of travel for freight trucks Low Work closely with Post Office 32

33 Challenges/Risks Safety/Regulatory/Permitting Risk Initial Risk Level Mitigations Residual Risk Level Manned entry into active sewer under confined space conditions with hazardous sewer gases High Design an odor treatment system that reduces hazardous sewer gas levels below OSHA limit Clearly define safety requirements Low Monitor compliance with safe work practices Sanitary sewer overflow in tributary system (Oakland) caused by contractor s operations Medium Clearly define requirements to maintain free flowing condition in Oakland system Clearly define penalties in special provisions for sanitary sewer overflow in Oakland system Low Not receiving obstruction and excavation from City of Oakland on schedule Medium Obtain pre-approval of traffic control plans Work closely with City of Oakland Medium Criminal activity jeopardizes safety of District staff High Clearly define site security requirements in special provisions Medium Worker exposure to toxic rehabilitation materials in a confined space condition High Only specify materials that are proven safe in a confined space condition Specify requirements for ventilation system Low 33

34 Challenges/Risks Technical/Quality Risk Initial Risk Level Mitigations Residual Risk Level Design does not provide flow management strategy that provides enough working hours for proper application High Utilize flow equalization available at Plant and South Interceptor to extend working hours Utilize temporary bulkhead wall and control gate to extend working hours Low Design does not incorporate lessons learned from previous Wood St. Rehab projects High Utilize project team from Wood St. Rehab projects for design submittal review Incorporate details from Wood St. Rehab project RFIs and COs into bidding documents Low Design does not anticipate challenges associated with managing tributary flows Medium Collect best available data on tributary flows (size, peak flow rate, etc) Clearly define contractor s responsibility to convey tributary flows in special provisions Low Rehabilitation materials are applied under unsuitable conditions High Only specify rehabilitation materials that are proven under active flow condition Require manufacturer representative assistance during application Apply rigorous quality assurance test procedures Medium 34

35 Questions 35