Sewer Authority Mid-Coastside1307B359-C05A...Sewer Authority Mid-Coastside References Nayyar, Mohinder L. Piping Handbook - Sixth Edition. McGraw-Hill, Inc. Lindeburg, Michael R. Civil

Meeting Date: January 25, 2010

Board Agenda Item No: 6A

SEWER AUTHORITY MID-COASTSIDE

Staff Report

Subject / Title

Receive Update and Provide Direction to Staff on the Intertie Pipeline System (IPS) Review and

Evaluation Report Findings and Recommendations

Staff Recommendation:

Receive Update and Provide Direction to Staff on the IPS Review and Evaluation Report

Findings and Recommendations

Fiscal Impact:

None this Fiscal Year; The Board’s Direction to Staff will be incorporated in the FY2010-11

Budget

Discussion/Report:

The Sewer Authority Mid-Coastside (SAM) retained SRT Consultants (SRT) to perform a desk-

top review of the IPS force main condition. The work resulted in the development of the 2009

SAM IPS Review and Evaluation Report (Report), which documented the findings and provided

the resulting recommendations.

The purpose of this work was to:

Identify possible factors contributing to the IPS force main failures,

Identify high risk areas force main segments prone to failure in the future, and

Develop short- and long-term strategies for minimizing the possibility of future IPS force

main failures and allowing for proactive asset management of the facilities.

The IPS is over 30 years old and has experienced several failure episodes. Due to the lack of

redundancy in the pipeline system, opportunities for pipeline inspections, physical condition

assessment, and preventive maintenance are extremely limited. SAM requires a short- and long-

term plan for the IPS rehabilitation to achieve its goals of:

(1) Minimizing potential for IPS failure-related sanitary sewer overflow (SSO) events, and

(2) Extending the IPS service life in the most cost-effective and efficient manner.

The work on this Report identified the following probable root causes of the IPS force mains'

condition and resulting failures:

IPS age coupled with low flow velocities resulting in internal pipeline corrosion;

Lack of redundancy preventing SAM staff from conducting preventative maintenance;

Corroded air/vacuum valves not operating properly further contributing to corrosion.



The Report detailed the following alternatives for the IPS replacement and/or rehabilitation:

Alternative 1: Replace All IPS Force Mains

Alternative 2: Slip-line All IPS Force Mains

Alternative 3: No Project – O&M Activities

It is important to note that every IPS replacement and/or rehabilitation alternative included

installing bypass stations to create redundancy in the system and develop opportunities for

periodic inspections, preventative maintenance and repairs. Installing bypass stations on the IPS

force main will allow SAM replacing the current emergency-driven approach to proactive asset

management approach. The bypass stations with flexible hose connections can provide the most

efficient and cost-effective approach to the IPS force main rehabilitation. No permanent

underground bypasses were included in this approach.

Table 1 below summarizes alternatives developed in this Report for the IPS force main

rehabilitation and provides estimated 20-year present-worth costs for each alternative. Table 2

summarizes the recommended IPS Rehabilitation Plan - Alternative 3.

Table 1 IPS Rehabilitation – Summary of Alternatives

Description Probable Total 20-year

Present Worth Project Costs

Alternative 1: Replace All IPS Force Mains $25 M - $35 M

Alternative 2: Rehabilitate All IPS Force Mains through rigid

slip-lining

Alternative 3: Operational and Maintenance Activities over

20 years

$15 M - $22 M

$8.7M - $13.1M



Table 2 Recommended IPS Rehabilitation Plan

Plan Components Funding Level

Required, Dollars

Phase I – Short-Term Activities FY 2010/11 –

FY 2014/15

•Replace existing 18 Air/Vac Valves

•Install Bypass Stations – 2 stations

•Conduct Pump Station Flow Adjustment and FM Velocity Review

•Conduct Grit Survey

•Develop and Conduct an IPS Sampling Program

•Install Three New Isolation Valves

•Purchase Composite Wrap or Similar Equipment

•Inspect high-risk force main segments

•Conduct Hydraulic Surge Analysis

•Conduct another IPS Review in 2 to 5 years

$1.2 M - $1.6 M

Phase II – Long-Term Activities FY 2015/16 –

FY 2019/20

•Install additional 12 bypass stations

•Install 6 new flow control valves

•Disconnect Montara Pump Station hydraulically from the IPS

•Slip-line high risk segments

$2.5 M - $3.5 M

Phase III – Long-Term Activities FY 2020/21 –

FY 2030/31

•Slip-line remaining pipeline segments $5.0 M - $8.0 M

Total Rehabilitation Funding Required $8.7M - $13.1M

Tanya Yurovsky of SRT Consultants will be available at the meeting to address questions the

Board may wish to ask.

Attachments:

2009 IPS Review and Evaluation Report

Project Budget Sheet for Alternative 3

Intertie Pipeline System Reviewand Evaluation Report

December 2009

2009 IPS Review and Evaluation ReportSewer Authority Mid-Coastside

Table of ContentsExecutive Summary....................................................................................................................11 Purpose....................................................................................................................................52 Background..............................................................................................................................5

2.1 Recent IPS Failure Events................................................................................................72.1.1 Sanitary Sewer Overflows – Regulatory Implications...............................................8

2.2 Previous Studies...............................................................................................................82.2.1 Intertie Pipeline System Evaluation and Corrosion Study.........................................82.2.2 2007 Granada Force Main and Gravity Line Evaluation.........................................102.2.3 2008 SRT Memorandum.........................................................................................102.2.4 2009 SRT Memorandum.........................................................................................11

3 Current IPS Operation............................................................................................................133.1 IPS Pump Stations..........................................................................................................13

3.1.1 Montara Pump Station.............................................................................................133.1.2 Vallemar Pump Station............................................................................................133.1.3 Princeton Pump Station...........................................................................................133.1.4 Portola Pump Station...............................................................................................13

3.2 IPS Force Mains.............................................................................................................143.2.1 Montara Force Main................................................................................................143.2.2 Princeton Force Main..............................................................................................153.2.3 Granada Force Main................................................................................................16

4 IPS Hydraulic Analysis and Operational Assessment............................................................194.1 2008 SCADA Data Analysis............................................................................................194.2 EPANET Modeling..........................................................................................................194.3 IPS Force Main Velocities...............................................................................................194.4 IPS Force Main Pressures..............................................................................................234.5 IPS Air/Vac Valves..........................................................................................................254.6 Deposit Attack Damage..................................................................................................254.7 Sediment Impingement/Scour Damage..........................................................................264.8 High Risk Areas..............................................................................................................26

5 Conclusions and Recommendations.....................................................................................295.1 Replace All IPS Force Mains..........................................................................................295.2 Rehabilitate All IPS Force Mains....................................................................................305.3 No Project – O&M Activities............................................................................................31

5.3.1 Grit Survey/Grit Removal........................................................................................315.3.2 Pump Flow Adjustments and Velocity Review .......................................................325.3.3 Sampling Program...................................................................................................325.3.4 Surge Analysis.........................................................................................................325.3.5 Hydraulically Disconnect Montara PS from the IPS................................................325.3.6 Air/Vacuum Valve Replacement Program...............................................................325.3.7 Composite Wrap Technology...................................................................................34

December 2009 Page i of v


5.3.8 Install Bypass Stations............................................................................................345.3.9 Install Isolation Valves.............................................................................................365.3.10 Install Control Valves.............................................................................................37

5.4 Development of Alternatives...........................................................................................375.4.1 Alternative 1 Replace All IPS Force Mains..............................................................375.4.2 Alternative 2 Rehabilitate All IPS Force Mains........................................................375.4.3 Alternative 3 No Project...........................................................................................38

5.5 Evaluation of Alternatives...............................................................................................386 Recommended IPS Rehabilitation Plan.................................................................................41

6.1 Phase I – Additional Studies and O&M Activities - Short-Term......................................416.2 Phase II Rehabilitation – Long-Term Activities...............................................................426.3 Phase III Rehabilitation – Long-Term Activities..............................................................42

December 2009 Page ii of v


List of TablesTable ES-1 IPS Replacement and Rehabilitation Options.........................................................2Table ES-2 Recommended IPS Rehabilitation Plan..................................................................3Table ES-3 Phase I Cash Flow..................................................................................................3Table 2.1 Corrosion Terms.........................................................................................................9Table 3.1 IPS Pump Station Summary.....................................................................................14Table 3.2 IPS Force Main Summary........................................................................................17Table 4.1 2008 IPS FM Flows, MGD........................................................................................19Table 4.2 Estimated 2008 IPS FM Velocities, FPS..................................................................20Table 4.3 Flow Rates Needed to Provide 3.5 FPS Velocity.....................................................23Table 4.4 2008 IPS FM Pressures...........................................................................................23Table 4.5 Montara FM Flow and Pressure Conditions.............................................................24Table 4.6 High Risk Failure IPS Segments..............................................................................27Table 5.1 Estimated Unit Cost for Open-Trench Installation of New Pipe...............................30Table 5.2 Estimated Unit Cost for Fusible PVC Rigid Slip-Lining Installation.........................31Table 5.3 EZ Value Cost Estimate...........................................................................................36Table 5.4 IPS Rehabilitation Activities Summary.....................................................................39Table 5.5 IPS Rehabilitation – Summary of Alternatives.........................................................40Table 6.1 Recommended IPS Rehabilitation Plan...................................................................41Table 6.2 Phase I Cash Flow...................................................................................................42

List of FiguresFigure 2.1 Intertie Pipeline System Map....................................................................................6Figure 2.2 December 2008 Temporary Repairs.........................................................................7Figure 2.3 2008 IPS Force Main Failure..................................................................................11Figure 2.4 2009 IPS Force Main Failure..................................................................................11Figure 3.1 Montara FM Profile.................................................................................................15Figure 3.2 Princeton FM Profile...............................................................................................16Figure 3.3 Granada FM Profile................................................................................................17Figure 4.1 Montara FM (Leg 1) 2008 Velocity Distribution (Montara – Vallemar PS).............20Figure 4.2 Montara FM (Leg 2) 2008 Velocity Distribution (Vallemar PS – Princeton Tie-In). 21Figure 4.3 Montara FM (Leg 3) 2008 Velocity Distribution (Princeton Tie-In – Junction #1)...21Figure 4.4 Princeton FM 2008 Velocity Distribution.................................................................22Figure 4.5 Granada FM 2008 Velocity Distribution..................................................................22Figure 4.6 High Risk Failure IPS Segments............................................................................28Figure 5.1 Old Air/Vac Valves vs. Newly Installed Model.........................................................33Figure 5.2 Schematic Representation of a Bypass Station.....................................................34

December 2009 Page iii of v


List of AbbreviationsCCTV Closed Circuit TelevisionDIP Ductile Iron PipeFM Force MainFPS Feet Per SecondFT FeetGPM Gallons Per MinuteGSD Granada Sanitary DistrictHDPE High Density PolyethyleneHMB Half Moon BayHP HorsepowerID Inner DiameterIPS Intertie Pipeline SystemLF Linear FeetMG Million GallonsMGD Million Gallons Per DayMIC Microbiologically-Induced CorrosionMWSD Montara Water and Sanitary DistrictNPDES National Pollutant Discharge Elimination SystemO&M Operations & MaintenancePS Pump StationPVC Polyvinyl ChlorideROW Right-Of-WayRPM Revolutions Per MinuteRWQCB Regional Water Quality Control BoardSAM Sewer Authority Mid-CoastsideSRT SRT ConsultantsSSO Sanitary Sewer OverflowSTA StationUSEPA United States Environmental Protection ServiceUV UltravioletVCP Vitrified Clay PipeVFD Variable Frequency DriveWBA Whitley Burchett & AssociatesWWTP Wastewater Treatment Plant

December 2009 Page iv of v


ReferencesNayyar, Mohinder L. Piping Handbook - Sixth Edition. McGraw-Hill, Inc.

Lindeburg, Michael R. Civil Engineering Reference Manual - Ninth Edition. Belmont, CA: Professional Publications, Inc., 2003.

American Society of Civil Engineers. Sulfide in Wastewater Collection and Treatment Systems. New York, NY: American Society of Civil Engineers, 1989.

Jones, Garr M., Bayard E. Bosserman II, Robert L. Sanks, and George Tchobanoglous, eds. Pumping Station Design – Third Edition. Burlington, MA: Butterworth-Heinemann / Elsevier, 2006.

Roberson, John A., John J. Cassidy, and M. Hanif Chaundry. Hydraulic Engineering – Second Edition. New York, NY: John Wiley & Sons, Inc., 1998.

SRT Consultants. Corrosion Assessment Survey and Recommendations for the Montara 12-Inch Ductile Iron Force Main. Technical Memorandum to Sewer Authority Mid-Coastside. January 30, 2009.

SRT Consultants. El Granada Ductile Iron Pipe Force Main Corrosion Assessment. Technical Memorandum to Sewer Authority Mid-Coastside. November 2, 2009.

Whitley Burchett & Associates. Engineering Report for the Granada Force Main and Gravity Line Evaluation. Report to Sewer Authority Mid-Coastside. March 2007.

Whitley Burchett & Associates. Intertie Pipeline System Evaluation. Report to Sewer Authority Mid-Coastside. October 2005.

December 2009 Page v of v


Executive SummaryThe Sewer Authority Mid-Coastside (SAM) retained SRT Consultants (SRT) to perform a desk-top review of the SAM Intertie Pipeline System (IPS) condition. This 2009 SAM IPS Review and Evaluation Report (Report) documents the findings and provides the resulting recommendations. The purpose of this work was to:

• Identify possible factors contributing to the IPS force main failures, • Identify high risk areas force main segments prone to failure in the future, and • Develop short- and long-term strategies for minimizing the possibility of future IPS

force main failures and allowing for proactive asset management of the facilities.

The IPS is a network of force mains, gravity interceptors, and pump stations delivering raw sewage to SAM's Wastewater Treatment Plant (WWTP) for treatment and ocean outfall discharge. This Report's scope was limited to the review of the IPS force mains under current flow conditions only, future flow conditions and gravity lines were not part of the work scope.

The IPS is over 30 years old and has experienced several failure episodes. Due to the lack of redundancy in the pipeline system, opportunities for pipeline inspections, physical condition assessment, and preventive maintenance are extremely limited. SAM requires a short- and long-term plan for the IPS rehabilitation to achieve its goals of:

(1) Minimizing potential for IPS failure-related sanitary sewer overflow (SSO) events, and(2) Extending the IPS service life in the most cost-effective and efficient manner.

The work on this Report identified the following probable root causes of the IPS force mains' condition and resulting failures:

• IPS age coupled with low flow velocities resulting in internal pipeline corrosion;• Lack of redundancy preventing SAM staff from conducting preventative maintenance;• Corroded air/vacuum valves not operating properly further contributing to corrosion.

The Report details the following alternatives for the IPS replacement and/or rehabilitation:

Alternative 1: Replace All IPS Force Mains Alternative 2: Slip-line All IPS Force MainsAlternative 3: No Project – O&M Activities

It is important to note that every IPS replacement and/or rehabilitation alternative includes installing bypass stations to create redundancy in the system and develop opportunities for periodic inspections, preventative maintenance and repairs. Installing bypass stations on the IPS force main will allow SAM replacing the current emergency-driven approach to proactive asset management approach. The bypass stations with flexible hose connections can provide the most efficient and cost-effective approach to the IPS force main rehabilitation. No permanent underground bypasses are included in this approach.

December 2009 Page 1 of 42


Table ES.1 below summarizes alternatives developed in this Report for the IPS force main rehabilitation and provides estimated 20-year present-worth costs for each alternative.

Table ES.1 IPS Rehabilitation – Summary of Alternatives

Description Probable Total 20-year Present Worth Project Costs

A. Capital Improvement Alternatives

Alternative 1: Replace All IPS Force Mains $25 M - $35 MAlternative 2: Rehabilitate All IPS Force Mains through rigid slip-lining $15 M - $22 M

B. Alternative 3 - Operational and Maintenance Activities over 20 years

Phase I – Short-Term Activities FY 2011 - FY 20151. Replace existing 18 Air/Vac Valves2. Install Bypass Stations – 2 stations3. Conduct Pump Station Flow Adjustment and FM

Velocity Review4. Conduct Grit Survey5. Develop and Conduct an IPS Sampling Program6. Install Three New Isolation Valves7. Purchase Composite Wrap or Similar Equipment8. Inspect high-risk force main segments9. Conduct Hydraulic Surge Analysis10.Conduct another IPS Review in 2 to 5 years

$1.2 M - $1.6 M

Phase II – Long-Term Activities FY 2016 - FY 2020• Install additional 12 bypass stations• Install 6 new flow control valves• Disconnect Montara Pump Station hydraulically from

the IPS• Slip-line high risk segments

$2.5 M - $3.5 M

Phase III – Long-Term Activities FY 2021 - FY 2031• Slip-line remaining pipeline segments $5.0 M - $8.0 M



Table ES.2 summarizes the recommended IPS Rehabilitation Plan.

Table ES.2 Recommended IPS Rehabilitation Plan

Plan Components Funding Level Required, Dollars

Phase I – Short-Term Activities FY 2011 - FY 2015• Replace existing 18 Air/Vac Valves• Install Bypass Stations – 2 stations• Conduct Pump Station Flow Adjustment and FM Velocity

Review• Conduct Grit Survey• Develop and Conduct an IPS Sampling Program• Install Three New Isolation Valves• Purchase Composite Wrap or Similar Equipment• Inspect high-risk force main segments• Conduct Hydraulic Surge Analysis• Conduct another IPS Review in 2 to 5 years

$1.2 M - $1.6 M

Phase II – Long-Term Activities FY 2016 - FY 2020• Install additional 12 bypass stations• Install 6 new flow control valves• Disconnect Montara Pump Station hydraulically from the IPS• Slip-line high risk segments

$2.5 M - $3.5 M


Short-term cash flow projections for Phase I, Short-Term Activities, over the first five years of the IPS Rehabilitation Plan implementation are included in Table ES.3.

Table ES.3 Phase I Cash Flow Projection

Fiscal Year Y1 Y2 Y3 Y4 Y5

FY 2010/11 FY 2011/12 FY 2012/13 FY 2013/14 FY 2014/15Funding $380 k $315 k $180 k $140 k $185 kActivities 1, 2, 3, 4, 5 1, 6, 7 1, 6, 8 1, 6, 8 1, 8, 9, 101See Table 6.1 for detail on Phase I Activities



1 PurposeFollowing recent force main failure events, the Sewer Authority Mid-Coastside (SAM) retained SRT Consultants (SRT) to perform a desk-top evaluation of the SAM Intertie Pipeline System (IPS) condition. This 2009 SAM IPS Review and Evaluation Report (Report) documents the evaluation findings and lists the resulting recommendations. The purpose of this work was to:

• Identify possible factors contributing to the IPS failures, • Identify high risk areas that could be susceptible to failure in the future , and • Develop short- and long-term strategies for minimizing the possibility of future IPS

failures and allowing for proactive asset management of the facilities.

The scope of this Report was limited to the review of the IPS force mains at current flow conditions, gravity interceptors and future flow conditions were not part of the scope.

2 BackgroundThe IPS is a network of pump stations and pipelines, force mains and gravity interceptors that delivers raw sewage from SAM member agencies to SAM's Wastewater Treatment Plant (WWTP) located in the City of Half Moon Bay. Figure 2.1 represents the IPS map. SAM member agencies include Montara Water and Sanitary District (MWSD), Granada Sanitary District (GSD), and the City of Half Moon Bay (HMB). While the IPS is owned and operated by SAM, each member agency owns and operates their respective collection systems located upstream of the IPS1.

Sewage from MWSD enters the northernmost portion of the IPS system at the Montara Pump Station (PS) and the Vallemar PS. Sewage from GSD enters the mid-portion of the system via the Princeton PS and the Portola PS. Sewage from the City of Half Moon Bay enters the IPS at the very end of the system, flowing directly into the SAM WWTP's headworks. All pump stations are owned by SAM with exception of Vallemar PS, which is owned by MWSD.

The IPS includes three force main segments: Montara, Princeton, and Granada, constructed in 1979 of ductile iron pipe (DIP). The pipelines vary in diameter from 8 to 14 inches. Montara, Vallemar and Princeton pump stations all discharge into the Montara Force Main (FM), while only the Portola PS discharges into the Granada FM (see Figure 2.1).

1 SAM currently operates member agencies' lift stations under contract



Figure 2.1 SAM Intertie Pipeline System Map



2.1 Recent IPS Failure EventsOn December 6, 2008, SAM staff received a report of a possible sewer leak on Vallemar Avenue in Moss Beach. Staff discovered a leak in the 12-inch-diameter ductile-iron IPS sewer force main between the Montara PS and the Vallemar PS. To facilitate repairs, the flow was diverted via “The Strand” utilizing a bypass at Vallemar PS to gravity feed sewage back to the Niagara Lift Station and pump it back to the Montara Wet Weather Storage Tank (Montara Tank). Temporary repair clamps were placed on the 12-inch DIP (see Figure 2.2) until the leaky pipe segment was replaced with C900 PVC pipe on December 8, 2008.

Figure 2.2 December 2008 Temporary RepairsOn November 1, 2009, a leak occurred on the Granada FM located near Santiago Avenue and Highway 1 in El Granada. The leak was described as a sharp hole approximately the size of a coin that occurred at the pipe invert. SRT staff and a Winzler & Kelly corrosion engineer visited the site shortly after the leak was discovered and immediately conducted an investigation of probable mechanisms of corrosion. It was determined that external corrosion by means of low resistivity, aggressive soil or an induced stray current, were not likely contributors to the failure. The investigation concluded that the perforation was caused by an internal degradation mechanism, most likely sediment impingement or scouring.

According to SAM records, other sizable corrosion-related leaks previously occurred on December 24, 2003 on Vallemar Street in Moss Beach (Montara Force Main) and on February 21, 2006 at Highway 1 and Alto Avenue in El Granada (Granada Force Main).



2.1.1 Sanitary Sewer Overflows – Regulatory ImplicationsSanitary Sewer Overflow (SSO) is a violation of SAM’s National Pollutant Discharge Elimination System (NPDES) permit. In 1995, SAM had been fined by the Regional Water Quality Control Board (RWQCB), received a warning letter and a cease-and-desist order for its WWTP in 1996, underwent a federal investigation in 2003, and was once threatened with a $212-million-dollar fine by the United States Environmental Protection Agency (USEPA). Any future SSOs will likely expose SAM and its member agencies to high risk of fines and litigation due to potential public health impacts. Recently, the City of Pacifica was fined $2.3M by the RWQCB for the 6.9-million-gallon (MG) SSO in 2008.

2.2 Previous StudiesSAM has previously conducted several IPS studies. These studies were reviewed for the purpose of this Report along with operational data provided by SAM staff. The findings of these studies and their respective recommendations related to the IPS force mains are summarized below.

2.2.1 Intertie Pipeline System Evaluation and Corrosion StudyIn 2005, Whitley Burchett & Associates (WBA) completed the Intertie Pipeline System Evaluation and Corrosion Study (2005 Study). The work reviewed the condition and operation of all pipeline sections, force mains and gravity lines, and reviewed the system's pump stations operations. The evaluation included a corrosion study for all force mains in the IPS.

Corrosion StudyThe 2005 Study found the IPS force mains to have been placed in “mildly to very corrosive soil conditions,” with the most corrosive area located approximately 500 feet upstream of the Vallemar PS and extending south to Vermont Street area surrounding Station (STA) 28+00. The 2005 Study placed the remainder of the force mains in zones of “corrosive to moderately corrosive” soils. The 2005 Study recommended that the area surrounding STA 28+00 be carefully inspected and cathodic test stations be installed. Installation of the cathodic test stations was recommended for all IPS force mains at an interval of every 1,000 feet. A total of 27 cathodic test stations were recommended at a total estimated cost of $25,000. The 2008 work by SRT confirmed that the test station installed at Sta 28+00 currently provides sufficient cathodic protection.



The corrosion terms are summarized in Table 2.1 for reference.

Table 2.1 Corrosion Terms

Internal Corrosion Term Description

Deposit Attack

If particulates are firmly deposited at the bottom of the pipe, the residue can cause corrosion due to a change in the environment (i.e., the generation of a galvanic cell much like crevice corrosion). Whether inert or electrochemically active, this form of corrosion is called deposit attack2.

Sediment Impingement (Scouring)

Sediment impingement is the process in which particulates that are part of the normal flow in a pipe, travel along the bottom and remove any protective scale layers, thereby accelerating the possibility of corrosion attack. This is sometimes referred to as erosion corrosion.

Microbiologically Induced Corrosion (MIC)

Microbiologically-induced corrosion (MIC), which is sometimes referred to as hydrogen sulfide (H2S) corrosion, can occur in gravity sewers that are open to the atmosphere. It occurs when bacteria in the anaerobic slime layer reduces existing sulfates to hydrogen sulfide. The H2S is liberated into the crown area of the pipe above the flow line, where Thiobacillus bacteria further metabolizes the H2S into very low pH sulfuric acid (H2SO4). The sulfuric acid is corrosive to iron and cement-mortar. MIC usually does not occur in force mains since they are constantly full, disallowing the pipe walls from coming into contact with oxygen.

Air/Vacuum Combination Relief ValvesThe 2005 Study also reviewed the condition of the 20 combination air/vacuum relief valves (air/vac valves) located on the IPS force mains. The 2005 Study found that all of the air/vac valves reached the end of their service life and were in various state of disrepair mostly due to the valve configurations requiring confined space entry for access. The 2005 Study recommended that the existing air/vac valves be replaced with more modern air/vac valve assemblies which are more easily accessible for service and testing. The cost for replacing all existing dilapidated air/vac stations was estimated at $150,000 at that time. Only two of the air/vac valves have been replaced to date.

IPS Pump StationsThe 2005 Study examined the IPS pump stations. Major recommendations included replacing the entire Princeton PS with a submersible pump system similar to Vallemar due to inoperable

2 Jones, D. A., Localized Corrosion in Forms of Corrosion Recognition and Prevention, Edited by C. P. Dillon, NACE, Houston, 1982, p.20



pumps and operational inefficiencies (pump overrunning due to ragging problems) further exacerbated by the pumps being located within a confined space.

The hydraulic analysis indicated the Vallemar pumps were oversized, cycling on and off too often, taking “only 20 seconds to pump the water out during normal operations.” Montara PS pump output was reduced by 20 to 30 percent when the Vallemar pumps turned on. The Vallemar pumps often discharged into an empty pipe due to the pump station's location on a high point in the force main, “when the pumps first turn on, there is little or no resistance to flow, and the pumps discharge at very high rates.” The recommendation was to install variable frequency drives (VFDs) for pumps at the Vallemar PS to eliminate the pumping inefficiency and relieve the impact the Vallemar pumps have on the Montara PS. The 2005 Study further stated that “a single pump at Princeton needs to have flow in the force main from Montara or Vallemar to keep it from operating at too high of flow” and that a substantial amount of grit backs up into the Montara PS essentially clogging the intake line of one of the three pumps and preventing its use.

2.2.2 2007 Granada Force Main and Gravity Line EvaluationIn 2007, WBA completed the Granada Force Main and Gravity Line Evaluation (2007 Study). The 2007 Study looked at capacity needs in the “Granada Segment,” consisting of an 8,950-foot, 14-inch DIP force main between the Portola PS and Junction Structure #2, and a 7,150-foot, 24-inch vitrified clay (VCP) gravity line between Junction Structure #2 and Junction Structure #3. Based on a 2020 peak wet weather flow projection of 8.3 million gallons per day (MGD), the 2007 Study found the Granada force main to be undersized for meeting future demands and recommended construction of a new 14-inch-diameter polyvinyl chloride (PVC) FM parallel to the existing FM in the existing right-of-way (ROW). The 2007 Study recommended the gravity line be also paralleled, however, stated that the hydraulic capacity could be increased by merely enlarging an 18-inch-diameter portion of pipe located at the entry drive to the SAM WWTP to a 24-inch-diameter, possibly by pipe-bursting.

2.2.3 2008 SRT MemorandumFollowing the December 8, 2008 IPS failure, once the leaky pipe segment was removed, SAM hired SRT to conduct a corrosion investigation conduct (see photographs on Figure 2.3). The exposed pipeline exterior and surrounding soils were investigated for the possibility of external corrosion, uniform electrolytic corrosion or stray current discharge. No symptoms of external corrosion were found and external corrosion was discarded as a potential contributing factor of the December 2008 pipe failure. Graphitization was also ruled out by the corrosion engineer as the potential cause of failure.

The removed IPS pipeline segment was further reviewed for internal corrosion possibilities. Metallographic analysis of the effected pipe section indicated deposit attack as the primary cause of the pipe wall rupture further exacerbated by sediment impingement (“scour” or erosion corrosion), which removes the protective layers of the pipe lining and wall making it more susceptible to deposit attack. The 2008 SRT Memorandum prepared by SRT with



assistance of the corrosion engineer from Winzler and Kelly, subconsultant to SRT, indicated that microbiologically induced corrosion (MIC) may also be causing pipe damage, however, to a lesser extent than the deposit attack.

Figure 2.3 2008 IPS Force Main Failure

2.2.4 2009 SRT MemorandumOn November 1, 2009, a leak occurred on the Granada FM located near Santiago Avenue and Highway 1 in El Granada (see Figure 2.4). The leak was described as a sharp hole approximately the size of a coin that occurred at the pipe invert. SRT staff and a Winzler & Kelly corrosion engineer visited the site shortly after the leak was discovered, and immediately conducted an investigation of probable mechanisms of corrosion. It was concluded in the Technical Memorandum that external corrosion by means of low resistivity, aggressive soil or an induced stray current, were not likely contributors to the failure. The investigation concluded that the perforation was likely caused by an internal degradation mechanism, most likely sediment impingement or scouring.

Figure 2.4 2009 IPS Force Main Failure



3 Current IPS OperationA review of current IPS operations, essential in evaluating the factors possibly contributing to the pipeline damage, was performed for the purpose of the current study by SRT. The following sections describe the IPS system components, their operations and condition.

3.1 IPS Pump StationsFour sewage pump stations feed into the IPS. Flow from MWSD enters the IPS system at the Montara and the Vallemar PS, while flow from GSD enters the mid-portion of the system via the Princeton PS and the Portola PS.

3.1.1 Montara Pump StationThe Montara PS currently operates two Clow/Yeoman pumps equipped with VFDs. The VFDs allow steady-state conditions and limiting the pump on and off cycles. Only one of the pumps operates during normal conditions. The Montara 460,000-gallon wet weather storage tank provides additional storage volume during storm events.

3.1.2 Vallemar Pump StationThe Vallemar PS operates two constant-speed Flygt submersible pumps in a lead-lag mode. The pumps were designed for peak wet weather flows and are over-sized for dry weather. Having oversized pumps with a small wetwell causes the pumps to cycle on and off very frequently. During dry weather conditions, the filling of the wetwell happens in 3 to 4 minutes and it takes approximately 20 seconds to empty wetwell.

3.1.3 Princeton Pump StationThe Princeton PS operates two pumps with VFDs. However, even though the pumps are equipped with VFDs, they are operated at full speed at all times due to ragging problems. The pumps are located in a dry pit with very narrow ladder access. The pit is considered a confined space and requires controlled access. It is safer for staff to operate the pumps at full speed, which minimizes the ragging issues, than to operate the pumps at the best efficiency.

3.1.4 Portola Pump StationThe Portola PS operates three large pumps and one small pump. Two of the larger pumps are equipped with VFDs and operate in a lead-lag mode. The third large pump is a constant-speed pump and is utilized only during the wet weather flow as lag-lag. The small pump is a lead-lead Clow pump running an average of 16 hours per day during dry weather conditions.

Table 3.1 provides a summary of information for all four IPS pump stations, their pumping equipment, and respective rated capacities.



Table 3.1 IPS Pump Station Summary

Pump Station Pump Model Power

Rating, HP1Flow Rating,

GPM2

Speed Rating, RPM3

Head Rating,

FT4

Montara#1 Yeomans 6123 50 1400 1750 83#2 Clow 6312 50/15 1400/900 1790/188 83/36

Vallemar#1 Flygt 88 850 1770 115#2 Flygt 88 850 1770 115

Princeton

#1 Yeomans 4315-SC

75/22.5 1100 1795/1195 183

#2 Yeomans 4315-SC

75/33.3 1100 785/1190 183

Portola

#1 Clow 4315 20 700 1145 71#2 Clow 6315 75 1250/800 1774 122/72#3 Clow 6315 60 1250 1770 122#4 Clow 6315 60 1250 1770 122

1HP – horsepower2GPM – gallons per minute3RPM – revolutions per minute4FT – feet

3.2 IPS Force MainsThe IPS includes three force main segments: Montara, Princeton, and Granada, constructed in 1979 of DIP. The pipelines vary in diameter from 8 to 14 inches. Montara, Vallemar and Princeton PS all discharge into the Montara FM, while only the Portola PS discharges into the Granada FM (see Figure 2.1).

3.2.1 Montara Force MainThe Montara FM is the northern-most IPS section connecting the Montara PS, Vallemar PS, and the Princeton PS (via the Princeton FM tie-in) to a discharge point at Junction Structure #1. The Montara FM is approximately 16,850 feet in length. The line is 12 inches in diameter for approximately 14,200 feet from the Montara PS to the Princeton FM tie-in, and is 14 inches in diameter between the Princeton FM tie-in and Junction #1. Elevations fluctuate from 19 feet to 95 feet above mean sea level, with the Montara and Vallemar pump station elevations being above the Junction #1 elevation. The force main has several large peaks and valleys between the pumped sources and the discharge point.

SAM currently has the ability to direct sewage via a separate pipeline, that stems from the



Vallemar PS to the Montara Wet Weather Storage Tank via the Niagara Lift Station. This pipeline is very old, exposed in places, and subject to the effects of surrounding bank erosion. Therefore, it cannot be depended upon in the long-term. In addition, sewage can only be stored in the Montara Tank for a limited time before it must be pumped back into the Montara FM, especially during wet weather.

Other than the Vallemar bypass connection, no other redundancy exists in the IPS. In addition, there is no ability to isolate shorter pipeline segments without isolating an entire pipeline. Any leak or rupture on the Montara FM requires that the entire line be taken out of service until the pipe can be repaired. Figure 3.1 presents the Montara FM profile.

Figure 3.1 Montara FM ProfileDue to the many peaks and valleys in the Montara FM and the overall flow direction downward towards Junction Structure #1 (see Figure 3.1), the Montara FM appears to become unpressurized (flowing partially full) under certain flow scenarios (air/vac valves open at peaks).

3.2.2 Princeton Force MainThe Princeton FM is a 4,300-foot section of an 8-inch-diameter DIP. It connects the Princeton PS, located on West Point Avenue in Princeton, to the Montara FM, which flows into Junction #1. Elevations fluctuate between 3 feet and 19 feet above sea level, with the pump being lower than the discharge point. The force main has very small peaks and valleys and maintains a fairly consistent positive slope between source and discharge.

The force main currently has no redundancy and no ability to isolate shorter pipeline segments without isolating the entire pipeline. Any leak or rupture on the Princeton FM requires that the entire line be taken out of service until it can be repaired. Being the lowest


0 20 40 60 80 100 120 140 160 1800

10

20

30

40

50

60

70

80

90

100

STA

Elev

atio

n, F

T

Montara PS

Dec 2008 FailureSTA 9+30

Vallemar Tie-In

Princeton Tie-In

Junction Structure #1


point in the Montara/Princeton FM segment, a leak on the Princeton FM could produce a large discharge to the surrounding environment.

Figure 3.2 represents the Princeton FM profile.

Figure 3.2 Princeton FM Profile

3.2.3 Granada Force MainThe Granada FM, a 14-inch-diameter DIP, extends from the Portola PS for approximately 8,950 feet to Junction Structure #2. Following Junction Structure #2, a 24-inch-diameter VCP empties the entire IPS effluent by gravity into the SAM WWTP. Elevations fluctuate between 10 feet and 65 feet above mean sea level, with the pump being lower in elevation than Junction #2, and a very large peak existing between the pump and discharge point.

No other pump station discharges into the Granada FM. Although this force main carries all flow from the northern portion of the IPS, it has no redundancy and no ability to isolate shorter pipeline segments. Any leak on this FM would require that the entire pipeline be taken out of service until it can be repaired. It should be noted that design and installation of additional storage at the Portola PS is currently underway, which will certainly help provide additional repair time during a downstream force main failure, however, it cannot be relied upon during wet weather.


0 5 10 15 20 25 30 35 40 450

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STA

Ele

vatio

n, F

T

Princeton Tie-InPrinceton PS


Figure 3.3 presents the Granada FM profile.

Figure 3.3 Granada FM Profile

Table 3.2 summarizes characteristics of the IPS force mains.

Table 3.2 IPS Force Main Summary

Force Main Leg Length, FEET

Pipe Material

Diameter, INCHES

Number of Air Valves1

Number of Blowoffs1

Montara

Leg 1 - Montara PS to Vallemar PS 2,450 Ductile

Iron 12 1 none

Leg 2 - Vallemar PS to Princeton Tie-In

11,786 Ductile Iron 12 5 6

Leg 3 - Princeton Tie-in to Junction Structure #1


Princeton Princeton PS to Princeton Tie-in 4,254 Ductile

Iron 8 22 22

GranadaPortola PS to Junction Structure #2


1 From 1979 MAC “Project Unit 1 – Intertie Pipeline” Design Drawings2 No information was available between STA 32+00 and 42+54


0 10 20 30 40 50 60 70 80 90 1000

10

20

30

40

50

60

70

80

90

100

STA

Elev

atio

n, F

T

Nov 2009 FailureSTA 17+50

Portola PS

Junction Structure #2


4 IPS Hydraulic Analysis and Operational AssessmentThis section describes the analyses conducted for the purpose of this Report to identify the high risk areas for future failures. As force main failure episodes indicate internal corrosion mechanism potential due to sediment accumulation resulting from low flow velocities, the IPS analyses focused on estimating flow velocities and pressure ranges in the IPS force mains to determine the areas with high failure risk potential.

4.1 2008 SCADA Data AnalysisAverage daily flow rate data for 2008 was provided by SAM for the Montara PS, Vallemar PS, and Princeton PS. For the Portola PS, SAM provided 10-hour averages for 2008. These data points were analyzed to determine flow statistics and velocity ranges and utilized in EPANET hydraulic modeling.

4.2 EPANET ModelingThe 2008 flow data provided by SAM was combined with pipeline profile information for preliminary hydraulic modeling using the EPANET modeling software. An EPANET model was created for each of the three force mains (Montara FM, Princeton FM, and Granada FM). The FM models were used to analyze pressures and to determine if the pipelines were fully pressurized at various flow scenarios. Flow scenarios included running each pump station alone and concurrently with other IPS pump stations and analyzing them at minimum, average, and maximum daily flow rates. The modeling was conducted utilizing the Hazen-Williams formula with an assumed C-factor of 80 for aged DIP. This modeling was limited to defining the range of working pressures. No surge analysis was included in this study scope.

4.3 IPS Force Main VelocitiesTable 4.1 summarizes the 2008 IPS pump station flow data provided by SAM staff. All flow data is in million gallons per day (MGD).

Table 4.1 2008 IPS FM Flows, MGDPump Station Minimum Flow Average Daily Flow Maximum Daily Flow

Montara1 0.10 0.18 1.30Vallemar1 0.11 0.19 1.05Princeton1 0.13 0.18 0.70Portola2 0.18 0.79 2.381Estimated from 2008 average daily flow data provided by SAM2Estimated from 2008 10-hour flow data provided by SAM



Table 4.2 summarizes the estimated velocities in feet per second (FPS) in the various force main segments based on the flow data listed in Table 4.13.

Table 4.2 Estimated 2008 IPS FM Velocities, FPS1

Force Main Minimum Velocity Average Velocity Maximum VelocityMontara Leg 1 0.20 0.35 2.56Montara Leg 2 0.28 0.72 4.18Montara Leg 3 0.41 0.78 3.65Princeton 0.55 0.78 3.08Granada 0.26 1.14 3.441Assumes pipe is flowing full

The minimum velocity necessary to prevent sedimentation and biological growth in sewer pipes and to provide conditions for self cleaning is 2.0 FPS4. Velocities between 2 FPS and 3 FPS are usually recommended to ensure all but the heaviest particles remain in suspension. Since the IPS has a significant amount of larger, heavier grit, a velocity of 3.5 ft/s is the recommended velocity for the IPS force mains.

Based on the 2008 flow data provided by SAM and summarized in Table 4.1, the charts below demonstrate 2008 estimated velocity distribution for each of the IPS force mains.

Figure 4.1 Montara FM (Leg 1) 2008 Velocity Distribution (Montara – Vallemar PS)

3 Velocities are calculated based on 2008 cumulative pump station flow data4 2003 Civil Engineering Reference Manual, Michael R. Lindeburg


November January February April June July September October December February0.000.501.001.502.002.503.003.504.004.505.00

Montara Force Main Velocities

Betw een Montara PS and Vallemar PS

Month

Vel

ocity

, FPS


The first leg of the Montara FM (Figure 4.1) has an estimated average velocity of 0.35 FPS, and is likely even lower velocities for 9 to 10 months of the year. The velocity in this leg only rose above 2 FPS once during the largest storm on January 26, 2008. Back pressure from the Vallemar PS likely further decreases the velocity in this segment.

The remainder of the Montara FM (Legs 2 and 3, Figures 4.2 and 4.3) exhibits similar problems with average velocities of 0.75 FPS and lower for most of the year.

Figure 4.2 Montara FM (Leg 2) 2008 Velocity Distribution (Vallemar PS – Princeton Tie-in)

Figure 4.3 Montara FM (Leg 3) 2008 Velocity Distribution (Princeton Tie-in – Junction #1)




Betw een Vallemar PS and Princeton Tie-In

Month

Vel

ocity

, FPS



Betw een Princeton Tie-In and Junction #1

Month

Vel

ocity

, FPS


Recognizing that 2 FPS is the minimum velocity to keep solids suspended, and 3.0 to 3.5 FPS is recommended for force mains, it is probable that the Montara FM, especially Leg 1, experiences a large amount of sedimentation and possibly only experiences a sizable scour and re-suspension during the rainy season and flushing operations.

The Princeton FM (Figure 4.4) operates similarly to the Montara FM, with velocities averaging at 0.78 FPS, even lower for the majority of the year, and only occasional scour velocities occurring in the wet season.

Figure 4.4 Princeton FM 2008 Velocity Distribution The Granada FM (Figure 4.5), with an average velocity of 1.14 FPS, has higher estimated velocities than the Montara and Princeton force mains, however still lower than 2 FPS for the majority of the year. From January to March, the force main likely experiences some scouring and re-suspension of settled solids, however settlement is likely to occur the remainder of the year.

Figure 4.5 Granada FM 2008 Velocity Distribution


November January February April June July September October December February0.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

4.00

4.50

Granada Force Main Velocities

Month

Vel

ocity

, FPS

November January February April June July September October December February0.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

4.00

4.50

Princeton Force Main Velocities

Month

Vel

ocity

, FPS


Based on analyses summarized in Table 4.2 and Figures 4.1 through 4.5, it is apparent that velocities in all IPS force mains remain very low, under 2.0 FPS, for most of the year.

Table 4.3 summarizes the flow rates required in each IPS force main to ensure scouring velocities of at least 3.5 FPS.

Table 4.3 Flow Rates Needed to Provide 3.5 FPS VelocityForce Main Combined Flow Target, MGD

Montara, 12-inch-diameter 1.78 Montara 14-inch-diameter 2.42 Princeton 8-inch-diameter 0.78 Granada 14-inch-diameter 2.42

The flow and velocity data supports the findings of the 2008 work by SRT that cites deposit attack as the major cause of corrosion and the pipe failure that occurred in December 2008 and November 2009. Areas with high amounts of settlement, and by extension, areas with an increased deposit attack potential include force main sections just downstream of pump stations, low points in the IPS, and pipes with reverse slopes.

4.4 IPS Force Main PressuresThe EPANET model was utilized to estimate average working pipeline pressures based on the 2008 maximum daily flow rates indicated in Table 4.1. Table 4.4 summarizes the EPANET model results.

Table 4.4 2008 IPS FM PressuresForce Main Flow Scenario, MGD Estimated Average

Pressures, PSI1,2Location

MontaraMontara PS = 1.30Vallemar PS = 1.13 Princeton PS = 0.70

95 Vallemar TroughSTA 27+25

PrincetonMontara PS = 1.30 Vallemar PS = 1.13 Princeton PS = 0.70

52 Princeton PS

Granada Portola PS = 2.38 43 Portola PS1PSI – pounds per square inch2Maximum pressures will most likely be higher during peak hourly flows

As demonstrated in Table 4.4, IPS FMs experience moderate to low pressures. The highest average pressure of 95 PSI is estimated at the Vallemar trough under 2008 maximum daily



flow conditions. Generally, pressures under 150 PSI should not be of concern for DIP. However, when the IPS suddenly becomes re-pressurized after it was temporarily de-pressurized, it is likely subjected to high surge pressures and wide pressure fluctuations. Further analysis of surge conditions and pressures is recommended.

Table 4.5 summarizes the IPS average pressure and flow conditions at various flow scenarios based on EPANET modeling results.

Table 4.5 IPS Flow and Pressure Conditions

Flow Scenario Flow RatesFlowing Full,Yes/N

o

Minimum Flow Required to Flow

Full, MGDCritical Point,

STA

Montara PS Only

Min = 0.10 MGD No1.04 Montara Peak Air

Valve, STA 5+35Avg = 0.18 MGD NoMax = 1.30 MGD Yes

Vallemar PS Only

Min = 0.11 MGD No1.131 Montara Peak Air

Valve, STA 5+35Avg = 0.19 MGD NoMax = 1.05 MGD No

Montara and Vallemar PS2

Min = 0.21 MGD No~1.11 Montara Peak Air


Montara, Vallemar, and Princeton PS2

Min = 0.34 MGD No~1.40 Montara Peak Air


11.05 MGD required to pressurize the FM downstream of Vallemar PS 2 Flows at individual pump stations are per Table 4.1

The EPANET hydraulic modeling results summarized in Table 4.5 indicate that the Montara FM and the Granada FM may not be flowing full at low and average flow conditions. These conditions can occur in systems where pumps are located at higher elevations than their respective discharge point and where system peak elevations are substantially higher than the discharge points. These conditions exist in the Montara and the Granada FMs.

Since Junction Structure #1 is at a lower elevation than both the Montara PS and the Vallemar PS, presenting a negative static head condition and the peaks are higher in elevation than Junction Structure #1, the pumps need only overcome the local static head condition (high peaks) and the pipe friction head to discharge sewage into Junction Structure #1. Friction head on the 12- and 14-inch-diameter lines is insignificant under low flow



conditions. This means the pumps only need to push sewage to the tops of their respective local peaks after which gravity and siphon action conditions develop on the downward slopes. Although the Portola PS elevation is higher than Junction Structure #2, the Granada FM still has a very large peak elevation that is substantially higher than Junction Structure #2. At low flows Portola PS only needs to pump to the top of this high peak with gravity condition the rest of the way. These conditions persist until there is sufficient flow, and subsequently, sufficient friction head, to pressurize the pipe (See Table 4.5).

Generally, downhill pumping is not recommended and can cause the following FM issues:

• Partial vacuum/siphonage at high points• Gravity drain/airlocking • Pressure surges from velocity changes associated with pumps being turned on and off• Open channel flow on downward slopes during pump startup and low-flow conditions• Trapping of air/sewer gases at high points and downward slopes

4.5 IPS Air/Vac ValvesLow flow conditions on the IPS force mains require air/vac valves to remain open most of the time to allow air into the pipe and prevent vacuum on the downward slopes. Introduction of air may exacerbate corrosion due to MIC. When the pipeline becomes pressurized under a higher flow condition preceded by low flow, this air needs to be very quickly released. If the air/vac valve is not working properly, air can become entrained in the sewer pipe. Also, if the air/vac valve is corroded and does not allow proper operation for air to enter the pipe during low flow conditions, a vacuum could occur stressing and eventually damaging the pipe. Either air or vacuum scenario may have contributed to the recent IPS failures. It is imperative that air/vac valves function properly. Immediate replacement of the existing corroded air-vac valves is recommended.

4.6 Deposit Attack DamageDeposit attack was found by the corrosion engineer to be the most likely cause of the internal corrosion at both the 2008 and 2009 leak locations. The biggest contributor to deposit attack is low flow velocities causing deposit of grit and sediment in the pipe. These factors can lead to the long-term settlement of the grit/sediment onto the pipe bottom, creating a corrosive environment. December 8, 2008 investigation showed that the pipe had several inches of grit inside. The 2005 WBA Report stated that the Montara PS had significant grit accumulation, and that one of the original three pumps located at the station was incapacitated due to grit damage.

If Montara PS, or any other pump station in the IPS has a significant inflow of grit/sediment, and velocities are not sufficient to keep the material suspended, the pipeline sections immediately downstream of the pump station have likely developed the conditions for deposit attacks. The 2008 flow data indicates that low velocities under 2 FPS are prevalent throughout the entire IPS (See Table 4.2 and Figures 4.1 through 4.5). Pipeline sections with



increased slope (flowing uphill) and low lying areas (dips) also exhibit sedimentation due to gravity and low velocities.

Pipeline sections that become unpressurized during low flows (down-slopes just downstream of system peaks) may have added sediment deposits caused by downstream pumps pushing water backwards when the line re-pressurizes (reverse flow). During re-pressurization, sedimentation may increase further at the interface between open channel flow (pipe flowing partially full) and pressurized flow (pipe flowing full), as the flow directions compete and contribute to settlement. The recent failure locations are very close to this type of interface. Grit survey is recommended.

4.7 Sediment Impingement/Scour DamageConversely to deposit attack, sediment impingement is caused by grit/sediment accumulation followed by periods of increased velocities that suddenly moves the sediment down the pipe. This sudden movement likely causes significant abrasion resulting in pipe wall erosion. Due to the low velocities most of the year, the pipes likely become full of grit/sediment. Following a storm event, the grit/sediment is likely re-suspended, and is pushed very rapidly through the pipe. Heavier grit likely remains at the bottom of the pipe, eroding the pipe bottom as it slowly migrates down the pipe. In addition, new grit is likely introduced by the pump stations during wet weather. When the storm event is over, long-term settlement restarts. The pipe is now exposed for further deposit attack or MIC.

Since downward slopes located just downstream of peaks may become unpressurized during low-flow conditions for most of the year, a reverse flow condition may occur once flows increase enough to re-pressurize the pipe, caused by downstream pump stations filling upstream air or vacuum gaps. In this scenario, a reverse scour may occur at the interface between open channel flow and closed conduit flow. The recent failure locations are very close to this type of interface.

Sediment impingement is probably occurring throughout the IPS, most likely at the same locations as the deposit attacks just downstream of pump stations, areas of increased slope, and low dip areas. A bi-directional scour could be happening in downward slopes located just downstream of large peaks.

4.8 High Risk AreasAnalyses conducted for the purpose of this Report indicated that the corrosion and pipe failure due to deposit attack is likely occurring in areas just downstream of pump stations, as the low velocities that are prevalent most of the year cause grit and other large sediment to quickly settle once it enters the IPS. Areas of steep up-slopes and low-dip points in the IPS may be areas of secondary concern. The first leg of the Montara FM (between Montara PS and Vallemar PS) has the lowest velocities of anywhere in the IPS.

Areas that are unpressurized most of the year (downward slopes located just downstream of



system peaks), and more specifically the interface between open channel and closed conduit flow, may have even a higher possibility of deposit attack and sediment impingement, depending on the flow condition.

Sediment impingement is likely in the deposit attack areas. During a storm event velocities increase but are still lower than the minimum 3.5 FPS needed to re-suspend solids. In these velocity ranges, the grit and sediment likely creep along the pipe bottom, causing abrasion damage. Once velocities increase to over 3.5 FPS, which is rare, the particles probably begin to re-suspend, however abrasion still occurs. If MIC is occurring, it likely exacerbates the problem.

Table 4.6 summarizes the most probable high and medium to high risk areas in the IPS.

Table 4.6 High Risk Failure IPS SegmentsLocation Potential Causes

Interfaces between open-channel and closed conduit flow during low flow conditions:

• Montara FM, STA 11+00• Montara FM, STA 78+20• Montara FM, STA 122+00 • Granada FM, STA 64+64

• Oxygen-causing MIC possible• Increased sedimentation at low flows• Increased sediment impingement

(scouring) at high flows• Possible high pressures when refilling,

depending on air/vac valve functionality

Upslopes immediately downstream of pump stations:

• Montara FM, STA 1+00 to STA 5+35• Montara FM, STA 25+50 to STA 58+16• Princeton FM, STA 1+00 to STA 20+00• Granada FM, STA 1+00 to STA 22+00

• Severe low velocity most of the year• Increased sedimentation at low flows• Increased sediment impingement

(scouring) at high flows

Unpressurized areas downstream of peaks:• Montara FM, STA 5+35 to STA 11+00• Montara FM, STA 58+16 to STA 78+20• Montara FM, STA 110+00 to STA

122+00• Granada FM, STA 53+02 to 64+64

• Oxygen-causing MIC possible• Possible high pressures (water or air)

when refilling, depending on air/vac functionality



Figure 4.6 graphically depicts the areas summarized in Table 4.6 above.

Figure 4.6 High Risk Failure IPS Segments



5 Conclusions and RecommendationsCurrently, the IPS has no means of bypassing a pipe leak or major pipe rupture, aside from the ability to re-route wastewater back to the Montara Wet Weather Storage Tank via the Vallemar gravity connection to the Niagara Lift Station. Even this bypass line, however, cannot be fully depended upon due to its proximity to the ocean and exposure to ocean bluff erosion. This condition places SAM in a very precarious position in terms of IPS failures and resulting SSO potential coupled with SAM's inability to take pipeline segments out of service due to lack of redundancy in the IPS. If recent failures are any indication of future failure potential and due to high probability of a catastrophic failure from a large seismic event, SAM must consider options for improving the IPS condition and developing opportunities for redundancy.

The IPS force mains are aging and approaching the end of their service life. Based on the analyses conducted for the purpose of this Report, the large number of high risk pipelines sections identified (see Table 4.6 and Figure 4.6), and the high cost of emergency repairs and SSO fines, SAM needs to conduct activities to rehabilitate or replace the force mains. The recent IPS failures provide an indication of potential serious future problems. Two main strategies exist for SAM to continue relying on the IPS force mains to deliver sewage to the WWTP, including:

1. Replace all IPS force mains with new pipes through capital improvements;2. Rehabilitate all IPS force mains through:

• Capital Improvements or• Operational and Maintenance Activities

It is important to note that every option for the IPS force main replacement and/or rehabilitation includes installing bypass stations to create redundancy in the system and develop opportunities for periodic inspections, preventative maintenance and repairs. Installing bypass stations on the IPS force mains will change the current emergency-driven approach to proactive preventative maintenance approach to asset management. The bypass stations with flexible hose connections will provide the most efficient and cost-effective approach to the IPS rehabilitation. No permanent underground bypasses are recommended.

The strategies and their respective components are further detailed in this section.

5.1 Replace All IPS Force MainsThe IPS force main replacement will involve installing new non-metallic pipes or metallic pipes (most likely DIP) with cathodic protection parallel to the existing pipelines and installing bypass stations from the new pipelines to the old pipelines. This is a viable option and would allow for system redundancy. However, the redundancy would still depend on the existing dilapidated pipelines, the condition of which is expected to continue deteriorating, and which



may not be dependable in the next 5 to 10 years. Installing a new parallel piping system constructed of either PVC, High Density Polyethylene (HDPE), or cathodically protected DIP, depending on pressure, would likely also require complete rehabilitation of the existing force mains at a very high cost. The cost for securing an easement for the new pipe, the permitting process, the off-haul and import of trench material, and the long timeline for this work makes this option non-feasible for SAM to address the immediate operational and maintenance issues.

A planning level estimate of probable construction unit cost for new pipeline installation is provided in Table 5.1 for reference. The range of probable total project costs for the IPS replacement option is estimated at $25 million to $35 million. These costs include installing new pipelines parallel to the existing pipelines, installing bypass stations between the parallel pipelines, and rehabilitation of the existing pipelines.

Table 5.1 Estimated Unit Cost for Open-Trench Installation of New Pipe1, 2

Pipe Diameter, INCHES Unit Costs, $/LF3

C900 Class 150 PVC Pipe8 $17412 $21714 $239

SDR 11 Class 160 HDPE Pipe8 $37212 $46414 $512

1 Includes trenching, soil off-haul, import, pipe installation and backfill

2 Metal pipe is not recommended due to higher costs3 LF – Linear Feet

Installing new pipes in place of the existing pipes by an open-trench method is not really a feasible option and is not recommended due to the exorbitant cost to demolish, remove, and dispose of the existing pipe and fill, rehabilitate the trench, and then install a new line with new fill. The project would be time-consuming and require that bypasses be installed ahead of time since the IPS cannot be shut down for any substantial length of time. This option is associated with high risk and high cost for SAM.

5.2 Rehabilitate All IPS Force MainsThe IPS force main rehabilitation by means of rigid slip-lining using HDPE or PVC pipe is a feasible option for SAM provided bypass stations are installed before the slip-lining activities take place. Rigid slip-lining is the process of utilizing existing pipe cavity for installing new pipe. New pipe is fused together and then pulled through the existing pipe and void spaces



between the new and old pipe are filled with grout. Rigid slip-lining is preferred over “fold-in-form” slip-lining, because the latter depends on the existing pipe wall for structural integrity while the former does not. PVC is usually preferred over HDPE due to PVC having a thinner pipe wall (less of a size reduction) and lower costs. In addition, fusible PVC allows pipe segments to be welded together, increasing strength and reducing leaks and inflow and infiltration potential. The benefits of this option include: substantial savings on excavation, backfill, soil export and import, paving, finish-work, environmental permitting, and easement procurement.

Bypass stations would need to be installed on the force mains prior to utilizing this option, so the IPS can remain in service while a certain section of pipe is slip-lined. Slip-lining with PVC would result in a reduced inner diameter (ID), however, since PVC is a much smoother than aged DIP, the hydraulic capacity will be comparable to the present capacity, while providing the increased velocities for keeping solids suspended. A detailed hydraulic analysis would be required to review the smaller ID pipelines under maximum wet weather flows.

In general, unit costs for installing fusible PVC rigid slip-lining are estimated at about 70 percent of the cost for installing pipe using conventional open-trench method5. Table 5.2 provides a summary of estimated unit costs.

Table 5.2 Estimated Unit Costs for Fusible PVC Rigid Slip-Lining Installation Pipe Diameter, INCHES Unit Costs, $/LF

8 $12212 $15214 $167

The range of probable total project costs to rehabilitate the entire IPS is estimated at $15 million to $22 million.

5.3 No Project – O&M ActivitiesThe No-Project option includes minimizing capital improvements by utilizing cost-effective operational and maintenance strategies and conducting additional studies, sampling, and pipeline inspections. These strategies can be implemented to extend the service life of the existing IPS force mains and to provide much-needed redundancy at a fraction of the cost of implementing major capital improvements. The potential strategies are detailed below.

5.3.1 Grit Survey/Grit RemovalA grit survey at all IPS pump stations would assist in determining the amount of grit flowing into the IPS and to define if any particular pump station requires installation of a grit removal/screening system. Removing or decreasing the amount of grit entering the IPS will

5 November 19, 2009 Personal communication with Underground Solutions representative.



likely decrease any deposit attack potential and resulting damage to the pipelines and pumps.

5.3.2 Pump Flow Adjustments and Velocity Review According to SAM 2008 flow data, the IPS force mains rarely reach velocities capable of keeping grit and sediment suspended in the flow stream (See Section 4). This results in significant deposits throughout the IPS piping. Velocities should consistently remain between 2 and 3.5 FPS for solids to remain suspended. SAM should consider increasing pump flow rates on VFDs to ensure average velocities are in the recommended range.

5.3.3 Sampling ProgramSAM may consider conducting regular sampling for sulfide, sulfate, sulfuric acid, and dissolved oxygen concentrations at pump station wet wells, at locations along the IPS force mains, and at junction boxes, to determine if MIC is occurring in the IPS. At a minimum, SAM should test sulfuric acid concentrations in sewage entering and leaving the IPS.

5.3.4 Surge AnalysisIt is possible that the Vallemar PS operation may be causing surge under certain conditions. Hydraulic surge analysis is recommended to determine if this is the case and to take the necessary steps to minimize the issue, for instance, installing VFDs at Vallemar PS or installing surge control/anticipation valves on the pump station discharge.

5.3.5 Hydraulically Disconnect Montara PS from the IPSAs described in Section 4, sewer force main systems that pump downhill, or have very large peaks, are very complex and problematic to operate and maintain. Problems include vacuum/siphonage, airlocking, pressure surges, loss of pressure, and trapping of air and sewer gases. The traditional means for moving sewage is to take advantage of topography and utilize gravity flow (open-channel flow) whenever possible, only utilizing pumps to move sewage to the next peak. A major benefit of open-channel flow is providing self-cleansing velocities at lower flow rates. Since the Montara FM peak located at STA 5+35 is the highest and most critical point in the Montara FM, it may be beneficial to install a junction box at this location, break head, and gravity feed the flow to the Vallemar wetwell. The Vallemar PS would then be hydraulically disconnected from the Montara PS, and, therefore, would no longer supply back pressure to the Montara PS. The Vallemar PS appears to be fully capable of handling this added flow, however, additional hydraulic analysis is required to analyze this option, to ensure the new configuration could handle wet weather flows.

5.3.6 Air/Vacuum Valve Replacement ProgramThe 18 air/vac valves in the IPS must be functional at all times to allow air to enter and escape the pipes as necessary during flow and pressure fluctuations. Existing air/vac valves are severely deteriorated and are not functioning properly, which could have catastrophic effects on the IPS. Properly functioning air/vac valves will prevent vacuum conditions and MIC caused by air and gases in force mains.



Eighteen of the existing 20 air/vac valves currently installed on the IPS force mains are in poor condition and reached the end of their service life (see photographs on Figure 5.1). Inspection of the existing valves indicates that all 18 are severely corroded. The existing corroded air/vac valves should be replaced as soon as possible. Two valves have already been replaced by SAM with new single-body combination air/vac valves designed for wastewater. Air/vac valves of this type are recommended for future installations. SAM should also consider above-ground canisters or modifying/replacing existing vaults to provide safe access. The new air/vac valves should be installed with quick-connect couplings, so the valves can be easily removed for maintenance on a regular basis. The air/vac valve replacements could easily be combined with bypass station installations, further reducing costs.

Figures 5.1 Old Air/Vac Valve vs. Newly Installed Model

Although replacement of all air/vac valves are recommended, the highest priority replacements include the following five (5) valves:

• Montara FM STA 5+35• Montara FM STA 58+16• Montara FM STA 110+00• Granada FM STA 22+00• Granada FM STA 51+66

The estimated cost for air/vac valve replacement is $12,000 to $15,000 each.



5.3.7 Composite Wrap TechnologyFor future pipe repair of existing IPS pipelines, SAM may want to explore alternative repair technologies, such as composite wrap or Carbon fiber wrap. This option is provided by EA Services, a pipe repair specialist company located in Benicia, CA and other specialty firms in the Bay area. EA Services and other similar companies can either be on call to install the product or can train SAM staff to install the product. Composite wrap utilizes carbon fiber to wrap the leaking pipe and then utilizes a ultraviolet (UV) cure method. The entire repair is reportedly completed in 2 to 3 hours (not including mobilization). The wrap provides protection for pressures up to 200 PSI, and is considered to be a permanent solution with a 50-year service life. Utilizing the wrap negates the need for installing temporary repair clamps or a new pipe segment, and preserves the conductivity of any corrosion protection system in place, and requires only one mobilization. Depending on the leak size and pipe size, a repair utilizing the composite wrap would cost between $8,000 and $16,000 per incident including excavation costs.

5.3.8 Install Bypass StationsBypass stations should be installed throughout the IPS at predetermined intervals starting with locations around the high risk areas outlined in Table 4.6 and near the air/vac valves needing replacement. This activity should be considered for implementation concurrently with the air/vac valve replacement.

The bypass stations would consist of installing a pipe-stopping mechanism (valve or proprietary method) with a hot-tap or tee on either side for connecting a bypass hose (or two hoses). In an event of a pipeline failure, flexible piping (hoses) are connected to each station to secure a temporary bypass allowing isolation of the damaged section to conduct repairs (see Figure 5.2). SAM would purchase and store sufficient lengths of the flexible piping.

Figure 5.2 Bypass Station Schematic



Bypass stations offer the following benefits:

1. Provide opportunities for much needed near-term redundancy throughout the IPS system and around high risk areas.

2. Allow for continued service in an event of a pipeline failure. 3. Allow SAM sufficient time for repairing failed pipe or replacing damaged sections. 4. Create an opportunity to systematically assess each area of force main by allowing

sufficient time to take a section of pipe out of service and conduct closed circuit television (CCTV) inspections.

5. Create an opportunity for sections of pipe to be replaced or slip-lined.

The main drawback of installing bypass stations is the innate risk of attempting to work on an old deteriorated pipe. The pipe walls need to be in good condition to withstand the process of securing a valve and a tee to them. Attempting to install new valves on pipe with thin pipe walls or even merely unearthing a thin-walled pipe can cause further pipe damage and failure. This could result in SAM staff having to “chase” the pipe back until they reach a stable pipe section, requiring more costly repairs. The only information gathered on the condition of IPS pipes have been obtained during leak investigations, and the condition of those pipes appear poor. The condition of the remaining IPS pipe sections remains unknown and disturbing these pipes without knowing their condition represents considerable risk. However, the benefits of installing bypass stations may out-weigh the risks.

Two options were reviewed for bypass station installation:

• Option 1 involves the installation of bypass stations utilizing off-the-shelf appurtenances such as tees, valves, flanges and flexible pipe (hose) to accomplish the bypass.

• Option 2 includes the installation of bypass stations by a third party utilizing proprietary (pipe stop) methods.

Although the proprietary option requires that SAM be dependent upon the technology and availability of a third party, this option is recommended due to perceived lower risk.

Insertion Valve/Hot-Tap Bypass InstallationThis approach includes proactively installing bypass stations at predetermined locations ahead of any pipe failures. This option assumes that all force mains are in poor condition and anticipates the possibility of a pipe failure anywhere within the IPS. An insertion valve would be installed at each of the predetermined locations as a means for temporarily blocking the flow. Insertion valves can be installed without taking the pipe out of service. Two hot-tap saddles would be installed, one on either side of the valve, to provide future hot-tap connection points for the temporary bypass. These connection points would be canned and covered at the surface to allow access at any point in the future.



Table 5.3 provides a summary of information on EZ Valve, one of the products reviewed for this Report, and its estimated cost. This information is included for reference purposes.

Table 5.3 EZ Valve Cost EstimatesProduct Name: EZ ValveVendor: Advanced Valve Technologies, Blue Island, ILProduct Description:

The EZ valve can be installed on a DI pipe in one day without interrupting flow in the pipe. Tapping sleeves would be installed on either side of the valve.

Cost: The cost estimate was provided by Advanced Valve Technologies for installing an EZ valve on a 8-inch and 12-inch pipe (EZ Valves are not available in 14-inch; other vendors need to be explored for a 14-inch insertion valve):

• 8-inch DIP: $7,000• 12-inch DIP: $14,000• Additional cost for two (2) tapping sleeves per installation: $6,000• Additional cost for 200 feet of 4-inch-diameter flexible pipe (hose):

$3,000• Total cost for one station on a 8-inch line: $16,000• Total cost for one station on a 12-inch line: $23,000• Total cost for two stations (one bypass setup): $30,000

Another approach for installing bypass stations, is to install one every time there is a force main failure and associated repair. This option and is unreliable and is not recommended for planned activities.

5.3.9 Install Isolation ValvesIsolation valves should be installed at several locations in the IPS force mains, to allow SAM staff isolate portions of the force mains in failure events, as follows:

1. An isolation valve should be installed on the Montara FM, upstream of the Vallemar PS, to allow Vallemar PS to operate normally if a leak or rupture occurs upstream of Vallemar PS, or to allow Princeton PS flow to be pumped to the Niagara bypass via Vallemar PS.

2. Another valve should be installed just downstream of the Vallemar PS, to allow Montara PS flows to be bypassed through Niagara, if necessary, without effecting Princeton PS.

3. A valve should be installed on the Montara FM just upstream of the Princeton Tie-in, to allow Princeton to operate normally if a leak or rupture occurs upstream of the tie-in.

4. Finally, a valve should be installed on the Princeton FM, just upstream of the Princeton Ti-In, to allow the Princeton FM to be isolated if a leak occurs on this line, to decrease



the rate of leakage on the Princeton FM, and to not interrupt flow from the Montara and Vallemar pump stations towards Junction #1.

These isolation valves could be combined with the bypass station effort. The valves would need to be insertion valves to allow IPS to remain in operation during installation. Costs for insertion valves range from $7,000 to $14,000 for the 8-inch- to 12-inch-diameter.

5.3.10 Install Control ValvesThere are control valve technologies available that could be utilized in the IPS. These include surge control or surge anticipation valves that could be installed on the Vallemar PS discharge to control surge pressures. In addition, pressure-relief valves could be placed on the downslopes of the IPS that do not open unless the upstream pressure is over a predetermined amount. This would ensure that the downslopes stay pressurized even at low flow conditions. Costs range from $8,000 to $18,000 per installation.

5.4 Development of AlternativesThis section provides a summary of the IPS rehabilitation and replacement alternatives' development. Based on the detailed discussion of various activities in the previous sections, the alternatives under consideration can be summarized as follows:

Alternative 1: Replace All IPS Force Mains Alternative 2: Slip-line All IPS Force MainsAlternative 3: No Project – O&M Activities

5.4.1 Alternative 1 Replace All IPS Force MainsThe IPS force main replacement will involve installing new non-metallic pipes or metallic pipes (most likely DIP) with cathodic protection parallel to the existing pipelines and installing bypass stations from the new pipelines to the old pipelines. This is a viable option and would allow for system redundancy. Installing a new parallel piping system would also include complete rehabilitation of the existing force mains. The range of probable total project costs for the IPS replacement option is estimated at $25 million to $35 million. These costs include installing new pipelines parallel to the existing pipelines, installing bypass stations between the parallel pipelines, and rehabilitation of the existing pipelines.

5.4.2 Alternative 2 Rehabilitate All IPS Force MainsThe IPS force main rehabilitation by means of rigid slip-lining using HDPE or PVC pipe is a feasible option for SAM provided bypass stations are installed before the slip-lining activities take place. The benefits of this option include: substantial savings on excavation, backfill, soil export and import, paving, finish-work, environmental permitting, and easement procurement. Bypass stations would need to be installed on the force mains prior to utilizing this option, so the IPS can remain in service while a certain section of pipe is slip-lined. The range of probable total project costs to rehabilitate the entire IPS is estimated at $15 million to $22 million.



5.4.3 Alternative 3 No ProjectThe No-Project option includes minimizing capital improvements by utilizing cost-effective operational and maintenance strategies, conducting additional studies, sampling, and pipeline inspections. These strategies can be implemented to extend the service life of the existing IPS force mains and to provide much-needed redundancy at a fraction of the cost of implementing major capital improvements.

This alternative includes the following activities:

1. Conduct Pump Station Flow Adjustment and Force Main Velocity Review2. Conduct Grit Survey3. Develop and Conduct an IPS Sampling Program4. Conduct IPS Hydraulic Surge Analysis5. Hydraulically Disconnect Montara Pump Station from the IPS6. Replace existing 18 Air/Vac Valves7. Install Isolation Valves8. Purchase Composite Wrap or Similar Equipment9. Install Bypass Stations10. Inspect high-risk force main segments11. Conduct another IPS Review in 2 to 5 years12. Install Flow Control Valves13. Inspect remaining force main segments14. Slip-line High Risk Segments

5.5 Evaluation of AlternativesThe alternatives were evaluated according to their respective priority rankings. The priority rankings are based on the following key considerations:

1. Implementation Efficiency2. Short- and long-term benefits3. Cost effectiveness4. Implementation risks

The rankings are qualified as low, moderate, and high. Since Alternative 3 represents a list of various activities, each one of them is ranked separately to show relative rankings within the alternative. Based on a large number of “high” rankings inside Alternative 3, it is ranked “high” overall. Table 5.4 lists the alternatives with their respective assigned priority rankings.



Table 5.4 Evaluation of the IPS Rehabilitation AlternativesDescription Ranking

Alternative 1: Replace All IPS Force Mains Low1

Alternative 2: Slip-line All IPS Force Mains Low to Moderate1

Alternative 3: No Project – O&M Activities High1. Conduct Pump Station Flow Adjustment and FM Velocity

Review High2

2. Conduct Grit Survey High2

3. Develop and Conduct an IPS Sampling Program High2

4. Conduct Hydraulic Surge Analysis High2

5. Hydraulically Disconnect Montara PS from the IPS Moderate3 6. Replace existing 18 Air/Vac Valves High4

7. Install Isolation Valves High4

8. Purchase Composite Wrap or Similar Equipment High4

9. Install Bypass Stations High4

10. Inspect high-risk force main segments High2

11. Conduct another IPS Review in 2 to 5 years High4

12. Install Flow Control Valves Moderate5

13. Inspect remaining force main segments High4

14. Slip-line High Risk Segments Moderate to High5

1Due to high cost and risk of implementation2Low-cost/high benefit items3Need to study the risks and implications before making this adjustment4Moderate- to Low-cost/critical to continued operation items5These activities must be preceded by installation of bypass stations on the IPS force mains

Table 5.5 details alternatives and their associated Total 20-year Present Worth costs. Phasing is developed for Alternative 3, the only alternative under consideration that allows implementation over a 20-year period while minimizing the risk for SAM.



Table 5.5 IPS Rehabilitation – Summary of Alternatives

Description Opinion of Probable Total 20-year Present Worth Project Cost, Dollars

A. Capital Improvement Alternatives

Alternative 1: Replace All IPS Force Mains $25 M - $35 MAlternative 2: Rehabilitate All IPS Force Mains through rigid slip-lining $15 M - $22 M

B. Alternative 3 - Operational and Maintenance Activities over 20 years

Phase I – Short-Term Activities FY 2011 - FY 20151. Replace existing 18 Air/Vac Valves2. Install Bypass Stations – 2 stations3. Conduct Pump Station Flow Adjustment

and FM Velocity Review4. Conduct Grit Survey5. Develop and Conduct an IPS Sampling Program6. Install Three New Isolation Valves7. Purchase Composite Wrap or Similar Equipment8. Inspect high-risk force main segments9. Conduct Hydraulic Surge Analysis10. Conduct another IPS Review in 2 to 5 years

$1.2 M - $1.6 M

Phase II – Long-Term Activities FY 2016 - FY 2020• Install additional 12 bypass stations• Install 6 new flow control valves• Disconnect Montara Pump Station

hydraulically from the IPS• Slip-line high risk segments

$2.5 M - $3.5 M


Based on the overall “high” ranking received in the evaluation and the lowest apparent cost, Alternative 3, No Project, is recommended for development and implementation.



6 Recommended IPS Rehabilitation PlanThis section presents the discussion of the recommended IPS Rehabilitation Plan based on implementing Alternative 3, No Project, and its associated components. Phasing of implementation includes conducting the highest priority activities within the next 5 years starting in Fiscal Year 2010/2011. This constitutes Phase I of the IPS Rehabilitation, which mostly includes operational and maintenance (O&M) activities and capital purchases. Phase II, which will span the next 5-year period, will include additional O&M improvements, followed by Phase III as detailed below in Table 6.1.

Table 6.1 Recommended IPS Rehabilitation Plan

Plan Components Funding Level Required, Dollars

Phase I – Short-Term Activities FY 2011 - FY 20151. Replace existing 18 Air/Vac Valves2. Install Bypass Stations – 2 stations3. Conduct Pump Station Flow Adjustment and FM

Velocity Review4. Conduct Grit Survey5. Develop and Conduct an IPS Sampling Program6. Install Three New Isolation Valves7. Purchase Composite Wrap or Similar Equipment8. Inspect high-risk force main segments9. Conduct Hydraulic Surge Analysis10.Conduct another IPS Review in 2 to 5 years

$1.2 M - $1.6 M

Phase II – Long-Term Activities FY 2016 - FY 2020• Install additional 12 bypass stations• Install 6 new flow control valves• Disconnect Montara Pump Station hydraulically from

the IPS• Slip-line high risk segments

$2.5 M - $3.5 M


6.1 Phase I – Additional Studies and O&M Activities - Short-TermThis section addresses near-term high-priority activities proposed for the next five years to initiate the IPS force main rehabilitation process. In addition, it provides the estimated funding requirements for the next 5 years for this Phase I. Table 6.2 illustrates the anticipated cash flow requirements for Phase I. The numbering system for the activities follows the assigned numbering in Table 6.1.



Table 6.2 Phase I Cash Flow

Fiscal Year Y1 Y2 Y3 Y4 Y5

FY 2010/11 FY 2011/12 FY 2012/13 FY 2013/14 FY 2014/15Funding $380 k $315 k $180 k $140 k $185 kActivities 1, 2, 3, 4, 5 1, 6, 7 1, 6, 8 1, 6, 8 1, 8, 9, 101See Table 6.1 for detail on Phase I Activities

6.2 Phase II Rehabilitation – Long-Term ActivitiesThe following activities are recommended for Phase II:

1. Install additional 12 bypass stations2. Install six (6) new control valves3. Disconnect Montara PS from the IPS4. Slip-line high risk segments

The five-year cost for the activities is estimated at about $2.5 million to $3.5 million.

6.3 Phase III Rehabilitation – Long-Term ActivitiesPhase III will include slip-lining the remaining force main segments. The estimated cost ranges between $5.0 million to $8 million.


Improve

Improvement Description:

Improvement Justification:

Risk

Schedule

Board Approval - Project 07/10

Start Construction 07/10

Complete Construction 06/31

Five-Year Program

Improvement Cost Development Total FY10-11 FY11-12 FY12-13 FY13-14 FY14-15

Design / Consulting / Permitting $117,000 $22,400 $22,500 $12,300 $7,500 $52,300

Land Acquisition $0 $0 $0 $0 $0 $0

Purchase, installation, inspection $1,408,300 $452,900 $387,500 $212,700 $177,500 $177,700

Contingency (20% included) $0 $0 $0 $0 $0 $0

Flow Monitoring/Hydraulic Modeling $74,700 $54,700 $5,000 $5,000 $5,000 $5,000

Total $1,600,000 $530,000 $415,000 $230,000 $190,000 $235,000

Financial requirements Total FY09-10 FY10-11 FY11-12 FY12-13 FY13-14

Total $1,600,000 $530,000 $415,000 $230,000 $190,000 $235,000

Intertie Pipeline System (IPS)

Replace existing 18 Air/Vac Valves

Install 2 Bypass Stations

Conduct Pump Station Flow Adjustment and FM Velocity Review

Conduct Grit Survey

Develop and Conduct an IPS Sampling Program

Install 3 New Isolation Valves

Purchase Composite Wrap or Similar Equipment

Inspect High-Risk Force Main Segments

Conduct Hydraulic Surge Analysis

Conduct IPS Review

The IPS is over 30 years old and has experienced several failure episodes. Due to the lack of redundancy in the pipeline system,

opportunities for pipeline inspections, physical condition assessment, and preventive maintenance are extremely limited. SAM

requires a short- and long-term plan for the IPS rehabilitation to achieve its goals of: (1) Eliminating IPS failure-related sanitary

sewer overflow (SSO) events, and (2) Extending the IPS service life in the most cost-effective and efficient manner. Staff identified

the following probable root causes of the IPS force mains' condition and resulting failures:

(1) IPS age coupled with low flow velocities resulting in internal pipeline corrosion;

(2) Lack of redundancy preventing SAM staff from conducting preventative maintenance;

(3) Corroded air/vacuum valves not operating properly further contributing to corrosion.

This project includes installing bypass stations to create redundancy in the system and develop opportunities for periodic

inspections, preventative maintenance and repairs. Installing bypass stations on the IPS force main will allow SAM replacing the

current emergency-driven approach to proactive asset management approach. The bypass stations with flexible hose connections

can provide the most efficient and cost-effective approach to the IPS force main rehabilitation. No permanent underground

bypasses are included in this approach.

If these improvements are not implemented, SAM risks losing significant asset and facing high-cost emergency repairs, significant

fines, and public health endangerment.

Improve

20-Year Program

Improvement Cost Development Total FY10-11 FY11-12 FY12-13 FY13-14 FY14-15

Design / Consulting / Permitting $117,000 $22,400 $22,500 $12,300 $7,500 $52,300

Land Acquisition $0 $0 $0 $0 $0 $0

Purchase, installation, inspection $12,908,300 $452,900 $387,500 $212,700 $177,500 $177,700

Contingency (20% included) $0 $0 $0 $0 $0 $0

Flow Monitoring/Hydraulic Modeling $74,700 $54,700 $5,000 $5,000 $5,000 $5,000

Total $13,100,000 $530,000 $415,000 $230,000 $190,000 $235,000

$1,600,000

Financial requirements Total FY09-10 FY10-11 FY11-12 FY12-13 FY13-14

Total $13,100,000 $530,000 $415,000 $230,000 $190,000 $235,000

Improvement Cost Development FY15-16 FY17-18 FY18-19 FY19-20 FY20-21

Design / Consulting / Permitting

Land Acquisition

Purchase, installation, inspection $700,000 $700,000 $700,000 $700,000 $700,000

Contingency (20% included)

Flow Monitoring/Hydraulic Modeling

$700,000 $700,000 $700,000 $700,000 $700,000

$3,500,000

FY15-16 FY17-18 FY18-19 FY19-20 FY20-21

$700,000 $700,000 $700,000 $700,000 $700,000



Land Acquisition




$800,000 $800,000 $800,000 $800,000 $800,000

$4,000,000

FY21-22 FY22-23 FY23-24 FY24-25 FY25-26

$800,000 $800,000 $800,000 $800,000 $800,000



Land Acquisition




$800,000 $800,000 $800,000 $800,000 $800,000

$4,000,000

FY26-27 FY27-28 FY28-29 FY29-30 FY30-31

$800,000 $800,000 $800,000 $800,000 $800,000

Intertie Pipeline System (IPS)

Documents

Sewer Authority Mid-Coastside1307B359-C05A...Sewer Authority Mid-Coastside References Nayyar, Mohinder L. Piping Handbook - Sixth Edition. McGraw-Hill, Inc. Lindeburg, Michael R. Civil