Goals of today s presentation

Transcription

1 Fast-tracked Fircrest Pipe Bursting Project Leads to Success Darrel Frame, P.E. - Civil Engineer - Murray, Smith and Associates, Inc. Goals of today s presentation Review of City of Fircrest Pipe Bursting Project Case Study. Identify what factors increase the level of difficulty for a pipe bursting project. Overview of the pipe bursting process. Identify typical equipment and parameters associated with pipe bursting. Discuss combining trenchless methods to overcome construction challenges. 1

2 Welcome to Fircrest The Team!! 2

3 Location History Initially incorporated in Just under 1.6 total square miles census population was 6,439 people. Last dry city in State of Washington (illegal to sell alcohol by the glass prior to November 30, 2015). 3

4 The Problem Deteriorating concrete sewers more than 50 years old. Many sewer mains located in back yards of homes. Substantial root intrusion requiring excessive amount of maintenance (not surprising in a City named FIR -crest). Backyard View 4

5 Street View The Original Solution Relocate sewers out of backyard easements and into public right of way. Pros Easier access for maintenance. Cons Proposed sewers would be significantly deeper. Estimated cost to relocate sewers to right of way or replace sewers in right of way $21.5 million. 5

6 Even the logo suggests trees and hills Tree with roots Hilly topography More trees with more roots Photo of Elevation Difference 6

7 Funding Obtained several low interest loans from the State of Washington. 1 st loan from Public Works Board via Public Works Trust Fund. 2 nd loan from Department of Ecology. $7,633,500 at 2.8% for 20 years. 6,439 people. 2,847 housing units (assumed 1 sewer connection per housing unit). Assuming entire payment of DOE loan absorbed by rate increase. $14.60 per month per household. If entire project cost (approximately $21.5 million) is funded by rate increase. Over $40 per month. The Bigger Problem City did not want to substantially burden its citizens with a rate increase. 7

8 The Better Solution Replace sewers in same location using pipe bursting. Schedule Challenges Department of Ecology loan expires on March 15, 2016 and is non-renewable. Project needs to be designed and constructed in less than one year. Construction will take place in the backyards of single family residences during the wet season. Required Washington State Department of Ecology approval prior to advertising for bids. 8

9 Scope of Work Replacement of approximately 2,900 LF of 6 sewer main with 8 HDPE installed by pipe bursting. Installation of approximately 500 LF of 8 sewer main by open trench excavation. Reconnection of approximately 80 side sewer laterals. Replacement of approximately 17 manholes. Proposal Schedule Milestone Proposal # Days Between Milestones Authorization to Proceed 3/31/2015 N/A Design Complete 9/30/ Bid Opening 10/15/ Notice to Proceed 11/15/ Substantial Completion 2/21/ Project Acceptance 2/29/ Dept. of Ecology Loan Expires 3/15/ Total Days 350 9

10 Project vs. Proposal Schedule Milestone Proposal # Days Between Milestones Initial Schedule # Days Between Milestones Authorization to Proceed 3/31/2015 N/A 4/14/2015 N/A Design Complete 9/30/ /2/ Bid Opening 10/15/ /22/ Notice to Proceed 11/15/ /12/ Substantial Completion 2/21/ /25/ Project Acceptance 2/29/ /20/ Dept. of Ecology Loan Expires 3/15/ /15/ Total Days Approach Obtain easements from all property owners with sewers in backyards. Assume same type of pipe bursting that was previously successful would work again. Rely on limited geotechnical info since a similar pipe bursting project was completed in close proximity. 10

11 Project Comparison Project Comparison-Aerial 11

12 Level of Difficulty Criteria Level of Difficulty Analysis-Depth All segments of sewer main less than 12 feet deep. All segments classified as routine. 12

13 Level of Difficulty Analysis-Diameter All segments of sewer main 6 inches in diameter. All segments classified as routine. Level of Difficulty Analysis-Replacement Size All segments of sewer main increasing by one upsize in diameter. All segments classified as routine. 13

14 Level of Difficulty Analysis-Burst Length Six segments less than 350 long. Classified as Routine. Two segments greater than 350 long but less than 450 long. Classified as Challenging to Moderately Difficult. Two segments greater than 450 long. Classified as Difficult to Extremely Difficult. Bid Results Bidder Cost (excluding WSST) High Bid $1,729, #4 $1,667, #3 $1,509, #2 $1,499, Engineer s Estimate $1,487, Low Bid $1,196,

15 Bid Results Statistics Description Cost (w/o WSST) % Change from Engineer's Estimate Engineer's Estimate $1,487, N/A Low Bid $1,196, % Mean Bid Price $1,520, % Median Bid Price $1,509, % Pipe Bursting Process Overview 15

16 Pipe Bursting Head The Schnoz 16

17 Hydraulic Winch Winch Controls 17

18 Air Compressor Control Panel Entry Pit 18

19 Entry through Manhole Sidewall Fusion Equipment 19

20 Sidewall Saddle Fusion Joint Using Trenchless Methods to Avoid Challenges Originally designed 135 LF of 8 PVC sewer as installation by open trench excavation/cut and cover. Contractor wished to avoid disrupting existing environment: Poor AC and cement concrete pavement. Avoid disturbing two large fir trees on either side of driveway. Elegant landscaping in backyard. 20

21 View from Street View from Backyard 21

22 Options Install as designed. Use pipe moling to create bore hole and pull pipe through bore hole using winch. Use micro HDD to create bore hole and pull pipe through bore hole using winch. Using Micro HDD to create bore hole 22

23 HDD Entry Pit Final Schedule Milestone Proposal # Days Between Milestones Initial Schedule # Days Between Milestones Actual Schedule # Days Between Milestones Authorization to Proceed 3/31/2015 N/A 4/14/2015 N/A 4/15/2015 N/A Design Complete 9/30/ /2/ /7/ Bid Opening 10/15/ /22/ /23/ Notice to Proceed 11/15/ /12/ /8/ Substantial Completion 2/21/ /25/ /15/ Project Acceptance 2/29/ /20/ /29/ Dept. of Ecology Loan Expires 3/15/ /15/ /15/ Total Days

24 Final Cost Comparison Description Cost % Change from Engineer's Estimate Engineer's Estimate $1,487, N/A Low Bid $1,196, % Mean Bid Price $1,520, % Median Bid Price $1,509, % Final Construction Cost $1,182, % *Excludes Washington State Sales Tax Mission Possible was a Success! Completed on time to avoid losing DOE funding. Completed significantly less than original project cost. Completed for less than contract amount (both design and construction). Final project cost was approximately $1.367 million. If financed over 20 years at 2.8%, result would be $2.62 rate increase. 24

25 Questions? Contact Information: Darrel Frame, P.E. Civil Engineer Murray, Smith and Associates, Inc. Office: Cell: