Structural Rehabilitation of the Kenilworth PCCP Transmission

Main with Steel Slipliner

Jeffrey Peluso, PEProject Manager, Baltimore County Dept. of Public WorksRon BrownSales Representative, Northwest Pipe Company

Presentation OverviewJeffrey Peluso, PEProject Manager

§ Baltimore Water System/Kenilworth Transmission Main

§ Significant Events§ First Investigation/Repairs§ Forensic Analysis§ Second Investigation§ Advanced Condition Assessment

Techniques§ Replacement or Rehabilitation?

Ron BrownSales Representative

§ Criteria for Solution Selection§ Construction Methods and

Material Evaluation§ Project Design§ Project Bid, Award and Pipe

Manufacture§ Installation§ Conclusion

Baltimore Water System

48” Kenilworth Transmission Main

• 48,854 LF (PCCP)

• Serves the Towson 4th Zone and 5 Upper Pressure Zones

• Conduit between Towson Pumping Station and Mays Chapel Reservoir

• Built in four (4) phases between 1970 and 1991

• 30” Redundant Source

48” Kenilworth Transmission Main

July, 2003, the trouble begins …

April, 2004 … the Main Fails Again, Approximately 4000 LF From the First Break

• 7800’-48” PCCP ECP (SP-12)

• Manufactured by Interpace Corporation w/Class IV Wire (1977)

• 4 Design Classes

Break 2

Break 1

Condition Assessment #1: November, 2004

Manned-Sounding P-Wave™

Condition Assessment Findings

• Inspected 394 sections• 16% had wire breaks• 16 sections with >50 wire

breaks• 4 sections with longitudinal

cracks and hollows• Recommended 4 sections to

be replaced• Re-inspect in 5 years

Subsequent Action Taken• 4 pipe sections were replaced

in May, 2005• Forensic analysis done on all • 3 out of 4 sections correlated

well with the P-Wave™ results• The other pipe had several

wire splices which created EM anomalies similar to breaks

• 2 pipes were incorrect design class and, consequently, under designed for existing conditions

Rate of Deterioration Using New Technology

• Hydrophone array launched Summer, 2005

• First commercial installation of a fiber optic acoustic monitoring system launched at the same time.

• 90 day trial• 14 wire breaks• Good correlation between

the systems• Trial discontinued after 90

day trial

Condition Assessment #2: October, 2010

Manned-Sounding P-Wave™

Condition Assessment Findings

• Inspected 386 sections• 16% had wire breaks• 40 sections with 5-75 wire

breaks• 5 sections with longitudinal

cracks and hollows• Pipes with wire breaks in

2004 continue to deteriorate

• Existing pipe does not meet current AWWA design standards

Risk Curve Analysis

What Do We Do Now??

Fix, Repair, Rehab, Replace?Criteria for Solution Selection

Critical Design Path Decision: (1)system, (2) Pipe Selection

1. A Fully Structural, Permanent Repair2. Overall Cost of the Solution /

Technology3. Minimum 100-year Service Life4. Length of Construction Time5. Minimize Hydraulic Flow Loss in Host

PCCP6. Minimize Social & Traffic Cost Impacts

Rehabilitation Methods and Materials Considered

1 2

3 4

1. Remove-and-Replace

2. Carbon Fiber Reinforced Polymers (CFRP)

3. HDPE Sliplining

4. Steel Cylinder Sliplining

§ Excavation of distressed sections followed by replacement with new pipe

§ Fully Structural: YES§ Overall Cost: High§ Min 100 yr Svc Life: YES (with proper

corrosion control)§ Construction Time: High, Pipeline

Alignment Under Pavement of Busy Roadway and in Shoulders

§ Hydraulic Flow: Same as host pipe§ Traffic Disruption: Very High, in Congested

Suburban Locale – Shopping Centers and Large Mall Close by

§ Resident Inconvenience: Very High

Rehab Option – Remove and Replace

Rehab Option – Carbon Fiber Composites (CFRP)§ Manual Application of Layers of CFRP and GFRP wet

lay-up System, Internally. Trenchless

§ Fully Structural: NO§ Overall Cost: Very High (only 33 sections of host

PCCP repair would cost $2.5 million)§ Min 100 yr Svc Life: ?? (first known CFRP in pipes

used less than 15 yrs ago)§ Construction Time: High, CFRP Technology is suited

for repair of short individual sections … therefore full section of Kenilworth Pipelines would take a long time

§ Hydraulic Flow: Minimal loss§ Traffic Disruption: Minimal, only need man-ways into

host pipe, and surface space for Ventilation and Other Equipment

§ Resident Inconvenience: Low

Rehab Option – High Density Polyethylene (HDPE)§ Insertion of continuous sections of HDPE pipe with

butt-fused joints

§ Fully Structural: YES (if grout applied in annulus)§ Overall Cost: Moderate§ Min 100 yr Svc Life: POSSIBLY (use of AWWA 3408

HDPE in water systems in US less than 25 years service)

§ Construction Time: Moderate, dependent on joint butt-fusion

§ Hydraulic Flow: High Loss of ID (42-inch DR 11 HDPE would have an ID of only 33.905, resulting in loss of almost 10-inches in the ID)

§ Traffic Disruption: High (large staging areas needed on surface for making long strings of butt-fused HDPE, as well as space for entry and exit pits)

§ Resident Inconvenience: High

Rehab Option – Steel Pipe Sliplining§ Continuous insertion of sections of Steel Pipe

(“cartridge” system … no continuous chains of pipe sections)

§ Fully Structural: YES§ Overall Cost: LOW compared to other options

considered§ Min 100 yr Svc Life: YES§ Construction Time: Moderate / Relatively Low§ Hydraulic Flow: Very Low Loss of ID (ID of steel pipe

sliplining system would be 40-inch minimum for the 42-inch host PCCP pipe)

§ Traffic Disruption: Low compared to other technologies considered (space needed on surface only for entry and exit pits)

§ Resident Inconvenience: Low

§ Use of welded joints would result in ZERO-leakage.

Final Technical Solution Selected

PCCP REHAB OPTIONS

Relining with Steel

PipeSliplining with Steel Pipe Selected because it met all selection criteria:

1. A Fully Structural, Permanent Repair YES

2. Overall Cost of the Solution / Technology LOW

3. Minimum 100-year Service Life YES

4. Length of Construction Time LOW

5. Minimize Hydraulic Flow Loss in Host PCCP LOW

6. Minimize Social Cost Impacts YES

Project Design

§ County and NWP worked together to develop Sliplining Specification

§ Geotechnical and sub-surface Conditions, Host PCCP Condition, Staging areas, Entry/Exit Pits, Steel Cylinder Strength to withstand Jacking Forces, etc. were determined

§ Host PCCP was 48-inch Diameter§ 7,800 LF of 40-inch ID Steel Pipe Cylinders

w/ 41 ¾-inch OD designed per AWWA M11 and AWWA C200 Steel Water Pipe standard

§ Working Pressure 120 psi, Test Pressure 180 psi

Project Design§ Cylinders designed as a fully structural

solution, to withstand: Internal Pressure, External Earth Loads, and External Hydrostatic Pressures from Ground Water, per AWWA M11

§ Cylinder also had to withstand Grouting Pressure (of grout applied in annular space between cylinders and host PCCP)

§ Since this was first project with Steel Sliplining, the County chose to be conservative against possibility of buckling of cylinder due to improper grouting procedures … used 3/8-inch thick cylinder (approx. 2X the needed thickness per M11). Therefore also handled 2X the required internal pressure

Project DesignCorrosion Control

Sliplining Cylinders§ Cylinder Outside was left bare … corrosion

control provided by use of Low Weight Cementitious Grout, combined with Corrosion Inhibitor

§ Internal Lining provided with ½-inch thick Cement Mortar Lining

Pipe Sections§ For corrosion protection of Welded Steel

Pipe sections in open-cut areas, bonded 80-mil thick dielectric tape-coating was applied per AWWA C214 and field installed Cathodic Protection

§ Internal Lining was ½-inch thick CML

Spiral Welded Steel Pipe Manufacture

Each Cylinder hydro-tested to 75% Min. Yield of Steel. For 41.5-inch OD pipe w/ 0.375-inch Wall, Test Pressure was 566 psi

Installation / Construction§ Exit/Entry Pits: 10 Pits, including tie-in

locations … sized to accommodate full pipe lengths and equipment.

§ Locations based on bends from as-builts, pushing distance and connection areas

§ Annular Spacing: Casing Spacers utilized to center steel slipliner pipe into the host PCCP --- 20-ft sections had 3 casing spacers, 10-ft sections had 2 casing spacers

§ Jacking Equipment: Jacking machine with connection sled used, instead of rail system. Bases of removed PCCP sections in pits served as tracks

Installation / Construction§ Jacking: Jacking limitation was 800-ft. For longer push

lengths of up to 1000-ft, excavator facilitated movement upstream while jacking machine continued to push

§ Reconnections: Mechnical couplings used to connect to new and existing pipe, and to valves, meters and other appurtenances.

§ Butt straps used to join sliplining pipe “trains” together in adjacent pits.

§ Corrosion protection at joints completed in field using heat-shrink sleeves, AWWA C216, and hand-tape, AWWA C209

§ Welding: Each joint was internally lap-welded§ Per AWWA C206 (field welding procedures) and AWS

B2.1 (welding qualifications)§ QC – Magnetic Particle Testing (per ASTM E709)

Installation / Construction§ Grouting§ Light-weight Cellular Foam with High

PH Grout Mix Used§ 28-day Compressive Strength of

Grout per ASTM C495/C796 Greater than 100 psi§ Grouting performed from pit-to-pit§ Low grout pressure of 5psi resulted in

100% of annulus being filled§ Grout Ports, though specified, were

not used due to nature of selected Grout

CONCLUSIONS§ The 48-inch Kenilworth Transmission Main, after failing a couple of

times and undergoing several condition assessment and forensic analysis using various technologies, underwent a permanent structural rehabilitation using Steel Pipe Sliplining

§ Other technologies considered for rehabilitation included Slipliningwith HDPE, Remove-and-Replace with PCCP, and CFRP (Carbon Fiber composites) Lining

§ Project was completed with Steel Pipe in timely fashion, w/o disruption to traffic/ community and as planned by Baltimore County