A Sigh of Relief: Completion of the San Mateo El Cerrito Relief Line. Kourosh Iranpour, PE

Transcription

1 A Sigh of Relief: Completion of the San Mateo El Cerrito Relief Line Kourosh Iranpour, PE

2 Presentation Outline Background information Selection of preferred alignment Primary project challenges Selection of trenchless method (PTGB vs. HDD) PTGB Construction challenges Conclusions

3 Background Information Installed10,000 LF 27 and 30 SS Pipe Required by the Regional Water Quality Control Board Cease and Desist Order (CDO)

4 Agencies Contributing to Relief Line City of San Mateo (City) Lead Agency Crystal Springs County Sanitation District (CSCSD) Town of Hillsborough (Town) County of San Mateo

5 Jurisdiction Map El Cerrito Relief Line

6 Objective of Wet Weather only Relief Line Eliminate surcharge in SS system Minimize sanitary sewer overflows (ground inflow and infiltration) Monitor/Measure wet weather flow upstream

7 City of San Mateo Hydraulic Model Completed model in 2005 Identified Capacity deficiencies Potential improvements New sewer relief lines

8 Estimated SS Flows Dry weather = 1.2 MGD Combined dry & wet weather = 9.9 MGD Relief line to convey = 8.7 MGD ( )

9 Various Alternative Alignments

10 Decision Matrix

11 Weighted Score = Importance Rating X Impact Rating

12 Preferred Alignment (Grant St.) ``

13 Primary Challenges Crossing under Caltrain bridge Crossing Caltrans right-of-way Utility congested corridor in Tilton Avenue Crossing San Mateo Creek (CDFW Streambed Alteration Agreement)

14 Utility Congestion in Tilton Ave. CaltrainTilton Ave. Bridge 32 Upsize ex. 18 SS to 27

15 Overflow structure Siphon under San Mateo Creek Upsize exist 18 SS to 27 to carry W.W. and D.W. flows Connect to newly installed 27 in Hillsborough Install 30 SS pipe to carry W.W. flow only Connect to exist 33 SS pipe

16 8.7 MGD W.W. GRANT ST. Overflow structure D.W. W.W. + D.W. TILTON AVE.

17 Construction of Siphon Under San Mateo Creek Trenchless Options Considered Pilot Tube Guided Boring (PTGB) Horizontal Directional Drilling (HDD) Grant St. E. 3rd. Ave. Gateway Park E. 2nd Ave. Grant St.

18 Plan View (HDD and PTGB) Launching pit for HDD Receiving pit for PTGB Receiving pit for PTGB Receiving pit for HDD Launching pit for PTGB

19 Profile View (HDD and PTGB)

20 Comparison of HDD and PTGB Pilot Tube Guided Boring (PTGB) Pros Precise exit accuracy No risk of frac-out Shorter drilling distance - decreases likelihood of conflicts due to shorter tunneling length Shorter siphon pipe to maintain 6 vertical clearance from creek bed Lower overall cost Less Traffic Disruption Launching pit can also be utilized for boring under 3 rd Avenue Cons Excavation in the Gateway Park Larger launching pit Boring distance limited to 500 +/-

21 Comparison of HDD and PTGB Horizontal Directional Drilling (HDD) Pros No excavation in Gateway Park Smaller launching pit Longer distance boring capability Cons Less accurate Potential for frac-out Longer drilling distance increases likelihood of conflicts due to longer tunneling length Higher overall cost Longer siphon pipe to maintain More traffic disruption

22 PTGB Shaft Locations Designed Receiving Shaft Designed Jacking Shaft Designed Receiving Shaft

23 Crossing San Mateo Creek in Gateway Park Different Views of Alignment Under Creek

24 Jacking Shaft Location in Gateway Park Before Construction During Construction

25 Receiving Shaft Location at 2nd Ave. During Construction Before Construction

26 Receiving Shaft Location at 3rd Ave. During Construction 3rd Ave. 3rd Ave. Before Construction

27 Pilot Tube Guided Boring Equipment 36 Powered Cutter Head 30 Jacking Clay Pipe Jacking Frame Bentonite & Lubrication Pumps

28 PTGB Construction Challenges Construction time constraints: June 15 October 15 Stoppage of work due to equipment malfunction - At Creek crossing (filter nozzle clogged) - At 3rd Ave. (gauge reading error) Construction of additional jacking shaft

29 PTGB Construction Challenges Designed Receiving shaft Designed Jacking Shaft Designed Receiving Shaft Gauge Reading Error Additional jacking Shaft Rescue Shaft

30 Conclusions Achievements Met CDO deadline Completed construction 4% under budget APWA (Northern California Chapter) Project of Year Award No reported SSOs Lessons Learned Extensive pre-design investigation Utility locating and potholing Comprehensive geotechnical investigation Allowance for additional investigative work Thorough alignment study Determination of most practical trenchless method Expect the unexpected

31 Utility Locating and Potholing Instrumental in decision making process Safety Minimizes down time Minimizes surprises during construction Minimizes number of potholes

32 Conclusions Achievements Met CDO deadline Completed construction 4% under budget APWA (Northern California Chapter) Project of Year Award No reported SSOs Lessons Learned Extensive pre-design investigation Utility locating and potholing Comprehensive geotechnical investigation Allowance for additional investigative work Thorough alignment study Determination of most practical trenchless method Expect the unexpected

33 QUESTIONS? Acknowledgements City of San Mateo McMillen Jacobs (Geotechnical) Ranger Pipeline (Contractor) Subtronic Corp (Utility Locating) Towill (Surveying and Mapping) H.T. Harvey (Biological and Environmental) Ayala Boring (PTGB Sub) Akkerman (PTGB Equipment) NorthStar Drilling (Drilling Sub) The Hanna Group (Construction Management) 1401 Willow Pass Rd, Ste 500 Concord, CA Tel: