FINAL The Owens Lake Turnout Facility End Cap Study

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Prepared by:

Owens Lake Facilities Operations & Maintenance

Water Operating Division

Los Angeles Department of Water & Power

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Table of Contents

PURPOSE 05 INTRODUCTION 05 INCIDENT BACKGROUND INFORMATION 06 RISK ASSESSMENT MATRIX 12 RISK ASSESMENT RESULTS 16 T16 Turnout Facility Information 17 T10 Turnout Facility Information 21 T18 Turnout Facility Information 25 T17 Turnout Facility Information 27 T13 Turnout Facility Information 29 CONCLUSIONS 33

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PURPOSE The High Density Polyethylene (HDPE) End Cap Study was prepared in response to Great Basin Unified Air Pollution Control District (GBUAPCD)’s variance hearing requirements for the

T36 Valve Control Facility (Turnout) end cap failure.

The purpose of the report is to identify and assess the risk of potential HDPE end cap failures

for Owens Lake facilities. The end caps to be investigated are restricted to the 30-inch or larger

HDPE caps for this report. To date, there is no history of other types of ends caps failing

including those of smaller diameter, flanged, steel, or above ground.

Study Objectives:

1. To identify the locations of end caps with heightened risk of potential failure.

2. To identify measures that can be implemented to reduce the potential for end cap

failures.

3. To identify measures that can be implemented to reduce the damage resulting from

an end cap failure.

INTRODUCTION This assessment included a review of the construction plans for end caps and their location

relative to the mechanical concrete equipment pad:

a. The end caps located under the mechanical concrete pad are the primary

concerns due to damage potential in the event of failure. Access to the end caps

may require tunneling under the pad. Visual references are provided below.

End Caps Under The Pad Plan View

End Caps Under The Pad Section View

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b. The end caps located adjacent to the pads are secondary concerns as failures

would result in less damage. Access to the end caps will require trenching

adjacent to the pad. Visual reference is provided below.

End Caps Adjacent to Pad Plan View

End Caps Adjacent to Pad Section View

c. The development of a risk assessment matrix. This matrix was created to

objectively and consistently evaluate each turnout with an end cap for potential

failure risk.

INCIDENT BACKGROUND INFORMATION

To date, three turnout facilities have experienced end cap failures. The turnout facilities are

listed in the following table

Turnout Facilities

Failure Date Location End Cap

Diameter Year of

Construction

T18 01/29/09

Located in the

Lake Bed

30-inch 2004

T29/30 11/04/11

Below Pad

30-inch 2006

T35 12/05/11

Adjacent to Pad

30-inch 2006

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The T18 Turnout Station was constructed under the Owens Lake Phase 4 construction project

(2004). The T29/T30 andT36 Turnout Facilities were under the Owens Lake Phase 5

construction project (Year 2006). Locations of these end caps are shown on the following page.

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T18 Turnout Facility: On Thursday, January 29, 2009 at 2:00 p.m., the 30-inch end cap

experienced a catastrophic failure. The 30-inch end cap was buried in the lake bed.

Turnout Station 18 Overview

The damage caused by the end cap failure was insignificant. When the 30-inch end cap

failed, the water flow was discharged on to the lake bed. The end cap was repaired in

place and the turnout was returned to service.

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Turnout Station T29/30: On Friday, November 4, 2011 at approximately 1:00 A.M., a

pipeline break occurred at the T29/T30 Turnout Facility.

Aftermath of End Cap Failure at T29/30 Turnout Facility

The pipeline rupture undermined the turnout facility concrete pad. The erosion of the

earth base of the concrete pad resulted in the pad failure. The end cap failure was

beneath the concrete pad and the pipeline rupture that created the sinkhole was not

visible until morning. The damage required the redesign and reconstruction of the

turnout facility. The facility is scheduled to be operational by October 1, 2012.

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Turnout Facility T36: On Monday December 5, 2011 at approximately 1:15 pm, an end

cap failure occurred. The SCADA program detected the break and initiated the alarm.

The break was confirmed by an onsite contractor traveling by the turnout.

The contractor reported “boiling” sand adjacent to the turnout facility. Boiling sand will

occur when water under pressure (water pipe break) wells up through a bed of sand.

Aftermath of End Cap Failure at T36 Turnout Facility

The operations staff quickly isolated the water feed to the turnout. At the time of the

investigation, it was daylight with clear visibility. The end cap failure was adjacent to the

concrete pad.

An investigation of the failed turnout facilities revealed the destruction of the T29/T30

and the T36 facilities was due to the failure of the 30- inch end caps. The breakdown at

the T18 facilities was also caused by the failure of a 30-inch end cap. This indicates that

end caps of 30-inch diameter or larger have heightened risk of failure requiring study.

Therefore, for this report end caps of 30 inches and larger were analyzed.

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RISK ASSESSMENT MATRIX The Risk Assessment Matrix was developed to independently evaluate each turnout with

an end cap 30 inches or larger in diameter. All of the turnouts were scored based on the

characteristics of reliability, operations, the potential for damage, and recovery time. The

scores were summed and the turnouts were ranked relative to risk based on the

cumulative score.

Assessment criteria:

• Reliability – An evaluation of the end caps and fittings performance on the lake

based on historical end cap type, size, and date of installation for each turnout:

1. Size and Age – Methodology of adjusting the ranking of the end caps based

on:

a. The size of the end caps: The failures to date involved end caps 30

inches in diameter. The smaller diameter end caps have not

experience similar failures:

1. End caps equal to 36 inches were assigned 20 points.

2. End caps equal to 30 inches were assigned 10 points.

b. Date of installation: The first failure of an end cap occurred 5 years

after installation, which was installed as a part of the Phase 4 project

(2004):

1. End caps installed as a part of the Phase 4 project (2004) or

earlier were assigned 20 points.

2. End caps installed as a part of the Phase 5 project (2006)

were assigned10 points.

3. End caps installed as a part of the Phase 7 project (2010)

were assigned 5 points.

2. Pressure and use: End cap location relative to the inlet side versus the

discharge side of the pad. The failures to date were located on the inlet side.

The end caps located on the inlet side have experience constant

pressurization (24 hours a day and 7 days a week) of 60 psi or greater. The

end caps located on the discharge side will experience pressurization of 40

psi or less on the days when the facility is in use (8 hours a day and 3 days a

week) :

a. End Caps installed on the inlet side were assigned 20 points.

b. End Caps installed on the outlet side were assigned 5 points.

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• Operation – To assess the impact on compliance when turnout failures occur, they

were reviewed based on the type of shallow flooding and total area served.

1. The size of the area impacted. The areas served by the turnout were rounded

to the nearest 500 acres and are identified as small, medium, and large.

a. If the total area served is 2,000 acres or more, it was identified as

large and assigned 30 points.

b. If the total area served was between 1,000 and 2,000 acres it was

identified as medium and assigned 20 points.

c. If the total area served was 1,000 acres or less it was identified as

small and assigned 10 points.

2. Turnout Use (lateral shallow flooding can be restored to compliance

significantly faster than pond shallow flooding):

a. If lateral shallow flood is served, 10 points were assigned.

b. If both lateral shallow flood and ponds are served, 20 points were

assigned.

c. If the turnout serves only ponds, 30 points were assigned.

• Damage Potential and Recovery Time Review – Scoring for damage potential and

recovery time was based on the depth of the end cap and their location. The depth

for the end caps range from 4 feet to 18 feet below grade. The critical depths are:

1. At 5 feet below grade, shoring is required

2. At 18 feet below grade, engineered shoring plans are required.

3. The water table depth ranges from 4 to 12 feet below grade.

Drainage pumps will be required for various locations.

1. The location of the end cap:

a. Adjacent to the concrete pad; requires trenching for access:

1. Trenching 18 feet or more below grade was assigned 20

points.

2. Trenching deeper than 5 feet and less than 18 feet below

grade was assigned 10 points.

3. Trenching 5 feet or less below grade was assigned 5 points.

b. Below the pad; requires tunneling for access:

1. Tunneling 18 feet or greater below grade was

assigned 40 points.

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2. Tunneling deeper than 5 feet and less than 18 feet below

grade was assigned 20 points.

3. Tunneling 5 feet or less below grade was assigned 10 points.

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Ranking Summary

Location End Cap Size

(Inches)

End

Cap

Siz

e Fa

ctor

End

Cap

Loc

atio

n:

Inle

t or O

utle

t

Siz

e of

Are

a S

erve

d

Sha

llow

Flo

od,

Sha

llow

Flo

od a

nd

Pon

d, P

ond.

End

Cap

Loc

atio

n B

elow

Gra

de

Tren

chin

g.

End

Cap

Loc

atio

n B

elow

Gra

de

Tunn

elin

g.

Pot

entia

l for

D

amag

e an

d R

ecov

ery

Tim

e

Tota

l

Cum

ulat

ive

Tot

al

T10 Turnout Facility

Inlet 36 20 20 20 20 5 0 5

165 T10

Turnout Facility Outlet

30 10 5 20 20 10 0 10


Inlet 30 10 20 20 20 10 0 10

90 T13

Turnout Facility 0utlet

N/A* 0 0 0 0 0 0 0


Inlet 36 20 20 10 30 10 0 10

185 T16


36 20 5 10 30 10 0 10


Inlet 30 10 20 10 20 20 0 20

100 T17


N/A* 0 0 0 0 0 0 0


Inlet 30 10 20 30 30 10 0 10

110 T18


N/A* 0 0 0 0 0 0 0

*Not Applicable

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RISK ASSESMENT RESULTS:

Based on the risks assessment scores, the turnouts were ranked from the highest to lowest risk of failure as follows:

1. T-16 (Score = 185 points).





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T16 Turnout Facility Risk Assessment and Potential Mitigation Measures The T16 Turnout Facility was originally installed as a part of the Phase 7 construction project

(Year 2010). The turnout has two 36-inch end caps including the inlet end cap located 6 feet

from the edge and 8 feet below grade, and the outlet end cap located 8 feet from the edge and

13 feet below grade.

Risk reduction measures may include the following:

1. Replace the existing end caps with a reducer and 24-inch or less end cap. The review of

the end cap failures revealed the end caps less than 30 inches in diameter have not

failed on the lake.

2. Vertically raise the inlet end cap to three feet above grade by the installation of a 90

degree elbow and straight pipe. The purpose of the end cap relocation is to direct the

flow of water away from the turnout pad to minimize damage in the event of failure.

3. Horizontally extend the pipe and outlet end cap into the lake bed. The purpose of the

end cap relocation is to direct the flow of water away from the turnout pad to minimize

damage in the event of failure.

4. Install an air/vacuum valve adjacent to the end cap to mitigate the impact of pressure

spikes on the end cap.

5. Bury the end cap in concrete.

6. Restrain the end cap with a concrete (thrust block). A thrust block transfers the resultant

thrust force to the undisturbed soil adjacent to the thrust block. The result is the

undisturbed soil will absorb the thrust force instead of the end cap.

Specific tasks and duration:

The total project duration (186 working days):

• Design (14 working days): The tasks include:

1. Safety review of engineering plans and field location – 4 working days.

2. Engineered shoring plans for the trench located adjacent to the end cap –6 working

days.

3. Completion of the revised as built plans – 4 working days.

• Materials Procurement (125 working days): The tasks include:

1. The purchase of pipe, fittings, and valves – 125 working days.

• Pre-Construction (13 working days): The tasks include:

1. Review of operational schedules for the turnout facility – 3 working days.

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2. Preparation of the environmental control measures for construction activities - 10

working days.

• Construction (34 working days): The tasks include:

1. Site preparation for construction activities. The preparations include access for

construction equipment and material storage area - 14 working days.

2. The modification of the existing end cap. The activities include the trenching,

modification of the existing end cap, and burial of the modified end cap – 20 working

days.

Task Duration Reference Information

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Plans Reference Information

Turnout Facility Phase Drawing

Number Drawing

Title End Cap Location

End Cap Location

Below Grade*

End Cap Location

Plan Coordinates

End Cap Size

(Inches)

T16 Turnout

Inlet

7 (2010) D5734 M013

Enlarged Piping Plan

and Section

8.0 feet off of pad 13.0 feet 15-B 36

T16 Turnout Outlet

7 (2010) D5734 M013


and Section

5.7 feet off of pad 7.5 feet 5-J 36

*Measured from the top of the Pad.

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T10 Turnout Facility Risk Assessment and Potential Mitigation Measures

The T10 Turnout Facility was originally installed as a part of the Phase 7 construction project

(Year 2010). The turnout 36-inch inlet end cap is located 5 feet from the edge and 5 feet below

grade. The 30-inch outlet end cap is located 7 feet from the edge and 12 feet below grade.


1. Replace the existing end caps with a reducer and 24-inch end cap. The review of the

end cap failures revealed the end caps less than 30 inches in diameter have not failed

on the lake.


degree elbow and straight pipe. The purpose of the end cap relocation is so that when

the end cap fails; the resulting force of water is directed away and will not undermine the

existing pad.


end cap relocation is so that when the end cap fails; the resulting force of water is

directed away and will not undermine the existing pad.




6. Restrain the end cap with concrete (thrust block). A thrust block transfers the resultant








days.






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working days.


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days.


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Number Drawing


End Cap Location

Below Grade*

End Cap Location

Plan Coordinates

End Cap Size

(Inches)


Inlet

7 (2010) D5734M009


and Section

5.3 feet off of pad 4.7 feet 15 – K 36

T10 Turnout Facility Outlet

7 (2010) D5734M009


and Section

6.6 feet off of pad 11.5 feet 5-G 30


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(Year 2004). The 30-inch end cap failed January 2009 and was restored to service several

weeks later. The turnout has one 30-inch inlet end cap located 6 feet from the edge and 11 feet

below grade.











1. Safety review of engineering plans and field location – 4 working days. 2. Engineered shoring plans for the trench located adjacent to the end cap –6 working

days. 3. Completion of the revised as built plans – 4 working days.






working days.






days.

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Number Drawing


End Cap Location

Below Grade*

End Cap Location

Plan Coordinates

End Cap Size

(Inches)

T18 Turnout

Inlet

4** (2004) D55582 M008 Site Piping

Plan 8.0 feet

off of pad 11.1 feet 11-D 30

T18 Turnout Outlet

4** (2004) D55582 M008 Site Piping

Plan

*Measured from the top of the Pad. **Rebuilt January 2009

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(Year 2010). The 30-inch inlet end cap end cap is located 3 feet from the edge and 18 feet

below grade.




on the lake.




existing pad.












days.







working days.

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days.




Number Drawing


End Cap Location

Below Grade*

End Cap Location

Plan Coordinates

End Cap Size

(Inches)


Inlet

7 (2010) D5734 M015


and Section

2.5 feet off of pad 18.0 feet 14-C 30

T17 Turnout Facility Outlet

7 (2010) D5734 M015


and Section

NA


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(Year 2006). The turnout has one 30-inch inlet end cap located 7 feet from the edge and 13

feet below grade.




on the lake.




existing pad.


end cap relocation is so that when the end cap fails; the resulting force of water is

directed away and will not undermine the existing pad.












days.






30


working days.






days.


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Turnout Facility

Phase Drawing Number

Drawing Title

End Cap Location

End Cap Location

Below Grade*

End Cap Location

Plan Coordinates

End Cap Size

(Inches)

T13Turnout

Facility

Inlet

5

(2006) D5597 M014

Turnout

Facility

Piping

Plan

6.5 feet

off of pad13.4 feet 13-F 30

T13Turnout

Facility

Outlet

5

(2006) D5597 M014 NA


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CONCLUSIONS This HDPE End Cap study resulted in the identification of five turnout locations with end caps

that may experience similar failures to the T30 and T36 turnouts. These locations have 30-inch

or larger end caps which could be modified or eliminated to mitigate risk of failure. The

identified turnouts listed in order of highest to lowest risk are as follows:






The duration of mitigation measure implementation is expected to take approximately 186

working days for each location including design, material procurement, site preparation, and

retrofit construction. The actual construction period may fit within the off-season (July through

August) so a variance should not be required. Given the scale of the work, it likely would need

to be spread over a number of years to complete, logically beginning with the turnout structures

identified as having the highest risk. Consideration and ultimate approval of mitigation measure

implementation, schedule, and budget will be determined by the Los Angeles Department of

Water and Power Commissioners.

Documents

FINAL The Owens Lake Turnout Facility End Cap Study