water tank coating rehabilition assessment reportelcometer® 456 dft gauge .....7 appendices...

WATER TANK COATING REHABILITION

ASSESSMENT REPORT

South Tahoe Public Utility District

Prepared for

Prepared by

January 27, 2012

South Tahoe Public Utility District Water Tank Assessment Final Report

VA11-0079 Page i of ii STPUD Final Water Tank Assessment Rpt

TABLE OF CONTENTS 1 EXECUTIVE SUMMARY....................................................................................................................1 2 INTRODUCTION ................................................................................................................................4 3 METHODS..........................................................................................................................................6

3.1 Visual Observations .................................................................................................................... 6 3.2 Dive Inspection ........................................................................................................................... 7 3.3 Dry-Film Thickness ..................................................................................................................... 7 3.4 Paint Sample Analysis ................................................................................................................ 7

4 FINDINGS...........................................................................................................................................8 4.1 Arrowhead Tank.......................................................................................................................... 8

4.1.1 Interior Observations...........................................................................................................8 4.1.2 Exterior Observations..........................................................................................................9

4.2 Christmas Valley Tank ................................................................................................................ 9 4.2.1 Interior Observations...........................................................................................................9 4.2.2 Exterior Observations........................................................................................................10

4.3 Cold Creek Tank ....................................................................................................................... 11 4.3.1 Interior Observations.........................................................................................................11 4.3.2 Exterior Observations........................................................................................................12

4.4 Heavenly Tank .......................................................................................................................... 13 4.4.1 Interior Observations.........................................................................................................13 4.4.2 Exterior Observations........................................................................................................14

4.5 Iroquois No. 1 Tank................................................................................................................... 14 4.5.1 Interior Observations.........................................................................................................14 4.5.2 Exterior Observations........................................................................................................15

4.6 Stateline No. 2 Tank ................................................................................................................. 16 4.6.1 Interior Observations.........................................................................................................16 4.6.2 Exterior Observations........................................................................................................17

4.7 Tata Tank.................................................................................................................................. 17 4.7.1 Interior Observations.........................................................................................................17 4.7.2 Exterior Observations........................................................................................................19

4.8 Paint Sample Analysis .............................................................................................................. 20 4.9 Dry-Film Thickness Results ...................................................................................................... 21 4.10 Protective Coatings................................................................................................................... 22

4.10.1 Epoxies .......................................................................................................................22 4.10.2 Polyurethanes.............................................................................................................23

5 CONCLUSIONS ...............................................................................................................................24 6 RECOMMENDATIONS ....................................................................................................................25


VA11-0079 Page ii of ii STPUD Final Water Tank Assessment Rpt

TABLES Table 1-1 Summary of Water Tank Assessments.................................................................................. 2 Table 1-2 Summary of Recoating Priority and Estimate of Probable Construction Cost ....................... 3 Table 2-1 Summary of Water Tank Information ..................................................................................... 5 Table 3-1 VANDA Metal Corrosion Index for Coated and Uncoated Steel ............................................ 6 Table 4-1 Summary of Paint Sample Analysis ..................................................................................... 21 Table 4-2 Summary of Dry-film Thickness Readings ........................................................................... 22 Table 6-1 Recoating Prioritization and Estimate of Probable Construction Costs ............................... 27

FIGURES Figure 3-1. Elcometer® 456 DFT Gauge ............................................................................................... 7

APPENDICES Appendix A - Previous Reports Summary Table

South Tahoe Public Utility District Water Tank Rehabilitation Assessment Report

VA11-0079 Page 1 of 24 STPUD Final Water Tank Assessment Rpt

1 EXECUTIVE SUMMARY

South Tahoe Public Utility District (STPUD) has retained V&A Consulting Engineers (V&A) to provide

coating engineering services for 15 of 21 potable water tanks that serve the South Lake Tahoe,

California, community. The purpose of the project is to provide STPUD with information about the

existing condition of the tanks and, based on the findings, develop recommendations and contract

documents for the rehabilitation or replacement of the existing coating systems. The evaluation of the

tanks was conducted by reviewing existing dive reports and videos for 11 tanks, performing dive

inspections on five tanks while the tanks were in service, and evaluating one tank while it was out of

service.

On April 26 and 27, 2011 and June 21 and 22, 2011, Bay Area Coating Consultants (BACC) and

Aqua Video Engineering (AVE) performed dive inspections to evaluate the interior linings of the

Arrowhead, Christmas Valley, Cold Creek, Heavenly, Iroquois No. 1, and Stateline No. 2 tanks. On

April 28, 2011, V&A performed an evaluation of the Tata Tank while it was out of service. Based on

the results, the interior linings of the Christmas Valley, Cold Creek, Heavenly, and Gardner Mountain

No. 2 should be removed and replaced within the next 2 years. The exterior coatings of the Cold

Creek, Heavenly, and Flagpole No. 2 tanks should be removed and replaced within the next 2 years

due to excessive chalking and exposure of the primer (Photo 18, Photo 24, and Photo 45). Based on

the existing conditions, the top four tanks that need an interior and exterior recoat include Heavenly,

Cold Creek, Flagpole No. 2, and Christmas Valley.

The exterior coating dry-film thicknesses of the Arrowhead, Christmas Valley, and Stateline No. 2

tanks indicated that they are less than 15 mils and can be overcoated instead of removed and

replaced.

The heavy-metals analysis on the Tata Tank indicated high levels of chromium and lead on the

exterior coating and high levels of cadmium on the interior lining. The exterior coating of the Tata and

Iroquois No. 1 tanks will require lead abatement and containment procedures during the removal of

the existing coating. The concentrations exceed the Total Threshold Limit Concentration (TTLC) per

Title 22 California Code of Regulations (CCR) § 66261.24. If the interior and exterior coatings are

completely removed, the waste that is generated will have to be tested per the Toxicity Characteristic

Leach Procedure (TCLP) before it can be transported and disposed of at a waste site. If the waste

exceeds the TCLP limits stated in Title 22 CCR § 66261.3, the waste must be classified as hazardous

waste and be shipped to a hazardous waste disposal site.

Table 1-1 is a summary of the results of the most recent dive inspections, dry inspections, or

recoating information available from STPUD. Table 1-2 is a summary of an opinion of probable

construction costs and prioritization based on the recoating recommendations mentioned above and

the review of previous reports and dive videos for 21 tanks.



Table 1-1

Summary of Water Tank Assessments

Name Year Built

Dive Inspection Dry Inspection

V&A Document Review/Update

Angora 2010 NR NR None

Arrowhead 1995 7/19/08, Liq. Vision NR March 2011

Christmas Valley 1998 4/27/11, AVE-BACC NR None

Cold Creek 1980 4/27/11, AVE-BACC NR March 2011

Country Club 2009 NR NR None

Echo View 2010 NR NR None

Flagpole No. 1 1998 7/19/08, Liq. Vision NR March 2011

Flagpole No. 2 1999 7/19/08, Liq. Vision 9/12/08, BACC March 2011

Forest Mountain 1999 NR NR Int. Recoated 2010

Echo View 2010 NR NR None

Gardner Mountain No. 1 1998 7/19/08, Liq. Vision 9/11/08, BACC March 2011

Gardner Mountain No. 2 1998 7/19/08, Liq. Vision 8/13/07, BACC March 2011

H Street 1980 11/6/06, Liq. Vision NR Int. Recoated 2011

Heavenly 1984 6/22/11, AVE-BACC NR March 2011

Iroquois No. 1 1967 6/21/11, AVE-BACC NR March 2011

Iroquois No. 2 2000 NR 9/13/08, BACC Int. Recoated 2011

Keller No. 1 1963 NR NR To be Replaced

Keller No. 2 1968 NR NR To be Replaced

Lookout 1998 NR 9/11/08, BACC Int. Recoated 2011

Stateline No. 1 1994 9/12/07, Liq. Vision NR March 2011

Stateline No. 2 1995 9/10/07, Liq. Vision NR March 2011

Tata 1968 NR 4/27/11, V&A Decision TBD NR = No Record Available

Liq. Vision = Liquid Vision

AVE = Aqua Video Engineering

BACC = Bay Area Coating Consultants

A $12 per square foot ($/sq. ft.) unit cost is estimated for lining the interior of all tanks with a

polyamide epoxy and $20/sq. ft. unit cost for recoating tanks that have lead-based paint. Unit costs

should be increased to $15/sq. ft. if a 100% solids epoxy is used to reline the interior of the tanks in

order to account for the higher material cost. A $7/sq. ft. unit cost is estimated for overcoating the

existing coating on tanks. The opinion of probable cost includes a containment system for lead

abatement, dehumidification, mobilization, materials, and labor for the recoating work.



Table 1-2

Summary of Recoating Priority and Estimate of Proba ble Construction Cost

Name Interior Priority

Interior Probable Construction Cost

Exterior Priority

Exterior Probable Construction Cost

Angora 15 $72,000 17 $34,000

Arrowhead 12 $207,000 10 $89,000

Christmas Valley 2 $60,000 9 $30,000

Cold Creek 3 $113,000 2 $85,000

Country Club 14 $99,000 15 $41,000

Echo View 16 $61,000 18 $78,000

Flagpole No. 1 10 $48,000 N/A N/A

Flagpole No. 2 6 $68,000 4 $22,000

Forest Mountain 13 $55,000 11 $27,000

Gardner Mountain No. 1 9 $68,000 7 $32,000

Gardner Mountain No. 2 4 $63,000 8 $29,000

H Street 21 $43,000 6 $19,000

Heavenly 1 $194,000 1 $147,000

Iroquois No. 1 11 $83,000 5 $113,000

Iroquois No. 2 19 $70,000 12 $34,000

Keller No. 1 17 $64,000 19 $29,000

Keller No. 2 18 $44,000 20 $21,000

Lookout 20 $78,000 13 $36,000

Stateline No. 1 5 $246,000 14 $99,000

Stateline No. 2 8 $396,000 16 $152,000

Tata 7 $105,000 3 $128,000



2 INTRODUCTION

South Tahoe Public Utility District (STPUD) has retained the V&A Team, which consists of V&A

Consulting Engineers (V&A), Bay Area Coatings Consultants (BACC), and Aqua Video Engineering

(AVE), to provide coating engineering services for 16 potable water tanks that serve the South Lake

Tahoe, California, community. This report provides the findings from the tank coating assessment and

review, rehabilitation alternatives based on the specific findings of each tank assessment, an opinion

of probable construction costs for the rehabilitation alternatives, and a proposed construction

schedule prioritizing each tank based on existing condition.

The V&A Team performed various tasks, including confined space-entry assessment, dive video

assessment, and review of previous reports and documents, to determine the existing design and

condition of the coating systems of the tanks. The assessment tasks performed by the V&A Team are

described below.

• Dry Assessment (V&A) – A dry assessment was performed on the Tata Tank on April 28, 2011, while the tank was dry and out of service. The dry assessment involved performing a confined-space entry into the tank to determine the general condition of the coatings and dry-film thickness on the interior and exterior, and conducting a visual observation of any existing cathodic protection system components.

� Dive Assessment (BACC and AVE) – Dive assessments were performed on the Arrowhead, Christmas Valley, Cold Creek, and Stateline No. 2 tanks on April 26 and 27, 2011. Dive assessments on Iroquois No. 1 and Heavenly were performed on June 21 and 22, 2011. The dive assessments consisted of AVE divers entering the tanks, while in service, to determine the general condition of the interior coatings and to conduct a visual observation of any existing cathodic protection system components inside the tanks. On the exterior of the tanks, BACC recorded dry-film thickness and evaluated the general condition of the coating system. AVE cleaned the Cold Creek, Heavenly and Iroquois No. 1 tanks prior to conducting the dive inspection.

� Document Review (V&A) – The available dive reports and videos documenting the condition of 11 tanks were reviewed. The documents were used to determine the locations of the dive inspections and a prioritization of tank recoating work.

Some of the general tank information gathered from the assessments and document reviews are

listed in Table 2-1. Tanks that were evaluated during this project are shown in bold text.



Table 2-1

Summary of Water Tank Information

Name Year

Built

Capacity

(Gallons)

Diameter

(feet)

Height

(feet)

Date of Last

Assessment

Bolted Steel Tanks

Tata 1968 395,000 54.5 23.5 4/28/11

Country Club 2009 355,000 55 20 See Note 1

Concrete Reservoir

Flagpole No. 1 1998 202,000 L = 56 W = 56 7/19/08

Welded Steel Tanks

Angora 2010 249,000 38 31 See Note 1

Arrowhead 1995 211,000 34 31 4/27/11

Christmas Valley 1998 200,900 30 38 4/27/11

Cold Creek 1980 480,000 55 27 4/27/11

Echo View 2010 203,000 33.6 22.7 See Note 1

Flagpole No. 2 1999 176,000 38 24 9/12/08

Forest Mountain 1999 150,000 30 33 9/8/08

Gardner Mountain No. 1 1998 211,000 38 25 9/13/08

Gardner Mountain No. 2 1998 212,900 38 28 9/11/08

H Street Reservoir 1980 106,000 34 16 11/9/06

Heavenly Reservoir 1984 1,050,000 71 37 6/22/11

Iroquois No. 1 1967 328,000 40 35 6/21/11

Iroquois No. 2 2000 252,000 35 35 9/13/08

Keller No. 1 1963 208,000 39 24 No Record

Keller No. 2 1968 123,000 30 24 No Record

Lookout Reservoir 1998 300,000 41.5 28.75 9/11/08

Stateline No. 1 1984 1,280,000 90 27.4 9/12/07

Stateline No. 2 1995 2,280,000 120 27.4 4/26/11 Note 1. No assessment since original construction.



3 METHODS

3.1 Visual Observations

The primary investigative method consisted of conducting visual examinations and documenting

observations with digital photographs. The visual assessment focused on the condition of the interior

and exterior coating systems and the corrosion of the steel surfaces, including structural members,

piping, and fasteners. It should be noted that much of the condition assessment data is subjective

and based upon the evaluator’s expertise.

V&A created the VANDATM Metal Condition Index to provide consistent reporting of corrosion damage

based on qualitative, objective criteria. Table 3-1 documents the different deterioration levels of

coated and uncoated steel surfaces. The extent of steel corrosion can vary from Level 1 to Level 4,

with Level 1 indicating little to any corrosion and Level 4 indicating severe corrosion.

Table 3-1

VANDA Metal Corrosion Index for Coated and Uncoated Steel

Level of Corrosion Stage of Corrosion Description

Descriptive

Photograph

Level 1 Staining/Surface Rust – Minor corrosion. First stages of corrosion

damage indicated by corrosion staining or rusting.

Level 2 Pitting – Localized corrosion damage of the ferrous surfaces in the form

of pits. Depth of pits can range from small to large. Measuring these pits

will determine the extent of corrosion loss at the localized area.

Level 3

Flaking/Exfoliation – Top layers of the ferrous surface have corroded and

exfoliated or flaked off (also referred to as scaling). The extent of corrosion

can be determined by removing corroded surfaces until reaching sound

steel, and performing ultrasonic thickness testing. A direct measurement

cannot be used as the exfoliated and corroded metal has expanded to

many times its original thickness during the corrosion process.

Level 4 Significant Loss of Material – The extent of exfoliation has reached a

degree wherein the remaining thickness of metal is not sufficient to

maintain the structural integrity of the structure.

© 02011 V&A Consulting Engineers, Inc. All rights reserved.



3.2 Dive Inspection

V&A retained AVE to conduct the dive inspection of the interior lining of Arrowhead, Christmas Valley,

Cold Creek, Heavenly, Iroquois No. 1, and Stateline No. 2 tanks using a submersible closed circuit

television (CCTV) camera. The diver was instructed to document the existing condition of the roof,

walls, and floor. All dive equipment was disinfected prior to entering the water tanks with 200 parts

per million of chlorine solution. BACC was present during the dive inspections to assist AVE during

the dive inspection. BACC also determined the extent of chalking on the exterior surfaces of the

tanks according to ASTM D4214 Standard Test Methods for Evaluating the Degree of Chalking of

Exterior Paint Films.

The Heavenly and Iroquois No. 1 tanks were cleaned prior to the dive inspection. Arrowhead, Cold

Creek, Christmas Valley, and Stateline were not cleaned so the assessment was limited to those

areas that were not covered in silt or debris.

3.3 Dry-Film Thickness

Dry film thickness (DFT) is the thickness of a coating after it has cured.

DFT measurements on the tanks were recorded using an Elcometer®

456 Dry Film Thickness (DFT) Gauge, shown in Figure 3-1. This DFT

gauge utilizes the measurement technologies of electromagnetic

induction and eddy current to measure a wide variety of coatings on

ferrous surfaces.

Coating thickness measurements on the exterior walls were recorded at

a height of 5 feet above the floor around the circumference of the tanks.

Interior DFT measurements were obtained on the Tata tank while it was

taken out of service. The other tanks were still in service during BACC

and AVE’s site visit so no interior DFT measurements were obtained.

3.4 Paint Sample Analysis

The criteria for whether or not to collect a paint sample was based on the construction date of the

tank. If the tank was built in or prior to 1978, a sample was collected due to a higher probability of

lead-based primers. Coating samples were collected from four of the six tanks that were assessed

between April 26 and June 22, 2011. The samples were tested for 17 heavy metals, including lead,

according to EPA Method 6010B, at Xenco Laboratories, an environmental-analysis lab, in Houston,

Texas.

As a general note, if a potable water tank has an interior tank lining containing lead, the drinking

water must have a lead concentration less than 0.015 milligrams per liter (mg/l) as set forth by

Federal EPA Standards.

Figure 3-1. Elcometer®

456 DFT Gauge



For the removal of lead-based paint, the California Code of Regulations (CCR) Title 8, § 1532.1

states that worker safety measures must be implemented when the lead concentration in the coating

exceeds 600 parts per million (ppm = milligrams/kilograms or mg/kg) or 0.06% by weight. The

requirement for worker health and safety measures during the removal of a lead-based paint depends

on how much airborne lead the workers will be exposed to during a specified length of time as

outlined in CCR Title 8 § 1532.1. It states that the employer shall not expose an employee to lead at a

concentration greater than 30 micrograms per cubic meter of air (µg/m3) averaged over an 8-hour

period. V&A recommends including lead abatement in coating specifications whenever lead

concentrations of existing coatings exceeds 500 ppm.

4 FINDINGS

Review of dive inspection reports and video was conducted on Flagpole No. 2 and No. 2, Forest

Mountain, Gardner Mountain No. 1 and No. 2, H Street, Iroquois No. 2, Lookout Reservoir, and

Stateline No. 1. The table in Appendix A includes a summary of the findings of previous dive

inspections and assessments performed by BACC and Liquid Vision Engineering.

4.1 Arrowhead Tank

4.1.1 Interior Observations

The interior of the Arrowhead Tank was assessed during a dive inspection on April 27, 2011. The roof

plates and rafters are in good condition with minor rust staining from unwelded roof plates. This is

typical (Photo 1). The upper rings of the shell are in good condition (Photo 2). The lowest shell ring,

floor and a manway (Photo 3 and Photo 4) have isolated areas of bubbles that are intact and cover

less than 1% of the total interior surface area. Approximately 15% of the floor has areas of bubbles,

some measuring 2 inches in diameter.

Photo 1. Center roof column is in a good condition.

Photo 2. Overflow and upper wall are in a VANDA Level 1 condition.



Photo 3. Bubbles were found on the tank’s

floor.

Photo 4. Manway has bubbles in the coating

and is in a VANDA Level 1 condition.

4.1.2 Exterior Observations

The exterior coating of the tank is chalked but in fair condition with exposed primer on the roof (Photo

5). The exterior roof has deep scratches exposing the primer. However, the steel is not exposed

(Photo 6). Graffiti was observed on the roof and paint ball marks were observed on the side of shell.

The coating is chalking with a rating of No. 3 per ASTM D4214.

Photo 5. Exterior roof has exposed primer and

chalked surfaces.

Photo 6. Scratches in the roof coating and

chalked surfaces were visible.

4.2 Christmas Valley Tank


The interior surfaces of the Christmas Valley Tank were assessed during a dive inspection on April

27, 2011 and cleaned on June 22, 2011. Significant general corrosion is coming through the epoxy

coating on the roof plates and knuckle above the waterline (Photo 7). The epoxy coating on the roof



rafters, plates, and columns is cracking and detaching from the steel substrate (Photo 8). The shell

has numerous blisters, with 10% of them being fractured. An estimated 20% are on the shell and

100% on the floor (Photo 9). Blisters measured from 1/4-inch to a 1/2-inch. Deep pitting was not

observed on the floor. A 1/8-inch to a 1/4-inch layer of sediment was observed throughout the floor of

the tank (Photo 10).

Photo 7. Delaminated coating was observed

on the outer perimeter roof plates.

Photo 8. Center roof column with cracked

coating is in a VANDA Level 1 condition.

Photo 9. Blisters with corrosion between were

seen on shell rings 2 and 3.

Photo 10. An 1/8-inch thick layer of sediment

sits on floor.


The exterior coating of the tank is in fair condition and the primer on the roof and shell is exposed.

The prime coat is intact and looks to be well-adhered. The coating is chalking with a rating of No. 2

per ASTM D4214. Small trees were observed to be growing near the foundation of the tank and

should be removed as the roots may start to crack the concrete. Fallen debris from tree limbs can

cause the exterior coating to fail prematurely.



Photo 11. Chalked coating on roof and the

primer is exposed.

Photo 12. Chalked coating is visible on the

shell with graffiti.

4.3 Cold Creek Tank


The interior surfaces of the Cold Creek Tank were assessed during a dive inspection on April 27,

2011 and cleaned on June 22, 2011. One of the manways had VANDA Level 2 corrosion on exposed

bare steel (Photo 13).The shell and floor have numerous broken and fractured blisters measuring up

to 1/2-inch in diameter (Photo 14). The shell has sediment or slime below the waterline. The roof

plates, rafters, and knuckle are rusting and the lining has failed (Photo 15 and Photo 16). Sediment

on the floor measured 1/8-inch to 1/4-inch thick. The gauge wire is broken and laying on the floor.

Photo 13. Delaminated coating and Vanda

Level 2 corrosion can be seen on a manway.

Photo 14. Bubbles and blisters are evident on

the weld seams of the shell plates.



Photo 15. Center roof column is in a VANDA

Level 1 condition.

Photo 16. Knuckle area has sediment on wall

and is in a VANDA Level 1 condition.


The anode access hole covers are not tightly sealed and allow dust and debris to fall into the water

(Photo 17). The exterior coating is chalking and has exposed the primer on 90% of the surface (Photo

18). The exterior coating on the roof has reached the end of its design life. The coating is chalking

with a rating of No. 1 per ASTM D4214.

Photo 17. Anode access hole is not tightly

sealed. Exterior coating has chalked.

Photo 18. Red primer is exposed on 90% of

the roof.



4.4 Heavenly Tank


The interior surfaces of the Heavenly Tank were assessed during a dive inspection on June 22, 2011

following a cleaning on the same day. Significant surface corrosion is coming through the epoxy

coating on the roof plates and knuckle above the waterline (Photo 19). The epoxy coating on the roof

rafters, plates, and knuckle is cracking and detaching from the steel substrate (Photo 20). The shell

has numerous blisters, with 10% of them being fractured. An estimated 20% are on the shell and

100% on the floor (Photo 21). Blisters measured from 1/8-inch to a 1-inch. The diver used a knife to

scrape the floor coating and a milky residue was produced which indicates incomplete cure of the

coating (Photo 22).


on the radial beams on the roof.


on the outer perimeter roof plates.

Photo 21. Typical blisters with corrosion on

the outer perimeter floor.

Photo 22. A milky residue was produced

when the floor coating was scraped indicating

and incomplete cure.




The exterior of the tank is in poor condition with localized areas of surface corrosion throughout the

roof. The coating has detached and exposed the steel to the atmosphere at various locations (Photo

23). A roof plate weld was observed to be incomplete and has allowed moisture to escape and

delaminate the coating (Photo 24). The exterior shell is in fair condition with graffiti on the bottom

shell ring on the southwest side. The coating is chalking with a rating of No. 2 per ASTM D4214.

Photo 23. VANDA Level 2 condition on the

exterior roof plate.

Photo 24. Incomplete weld has allowed

moisture to corrode the exterior surface of

the roof plate.

4.5 Iroquois No. 1 Tank


The interior surfaces of the Iroquois No. 1 Tank were evaluated during a dive inspection on June 21,

2011 following a tank cleaning on the same day. The interior center column was in good condition

with minor cracking of the coating around the bolt heads (Photo 25). Minor staining from the roof plate

edges was observed above the water line however the coating was intact and in good condition

(Photo 26). The interior floor and walls were in good condition and the interior roof access hatch was

the only area that exhibited blisters and delaminations. Photo 27 and Photo 28 show the interior floor

and walls of the tank that are in good condition.



Photo 25. Minor cracking at the bolts of the

center column.

Photo 26. Roof and shell plate edges exhibit

minor staining.

Photo 27. Coating on floor and center column

is in good condition.

Photo 28. Coating on walls and overflow pipe

is in good condition.


The exterior roof has delaminated coating with exposed bare steel in VANDA Level 2 condition

(Photo 29). The exterior shell walls of the tank appear to have been coated recently and are in good

shape except for minor scratches done by vandals.



Photo 29. VANDA Level 2 condition at the

weld seam of the exterior roof plates.

Photo 30. Graffiti scratches on the lower

shell ring of the tank.

4.6 Stateline No. 2 Tank


The interior surfaces of the Stateline No. 2 Tank were assessed on April 26, 2011, during a dive

inspection. The lining system in this tank is in overall good condition (Photo 31 and Photo 32). The

rust staining observed on the edges of the roof plates is due to unwelded lap joints which is typical for

water tanks. This staining is considered to be normal wear and tear and is not of great concern.

Several blisters were observed on the lowest shell ring between the manway and interior ladder

(Photo 33). The blisters measured less than 1/2-inchand were not fractured with steel corrosion. No

blisters were observed on the floor of the tank. However, not all surfaces were evaluated due to the

sediment layer. A 1/8-inch thick layer of sediment was observed on the floor (Photo 34).

Photo 31. Outer perimeter columns and

beams are in a VANDA Level 1 condition.

Photo 32. Center roof column is in a VANDA

Level 1 condition.



Photo 33. Bubbles were seen on the lower

shell ring near the manway.

Photo 34. An 1/8-inch thick layer of sediment

is on the floor.


The exterior coating of the tank is in fair condition and the primer and intermediate coat are exposed

on the roof (Photo 35). The prime coating is intact and looks to be well adhered. The coating is

chalking with a rating of No. 2 per ASTM D4214 (Photo 36). Rocks have caused very minor damage

and minor corrosion was noted on the shell of the tank.

Photo 35. Primer is visible under the primer of

the roof finish coat.

Photo 36. Overall view of chalked exterior

surfaces of Stateline No. 2 tank.

4.7 Tata Tank


V&A assessed the interior surfaces of the Tata Tank on April 28, 2011, while the tank was taken out

of service. The rungs and frame of the ladder are made from angle pieces instead of rods. They are

severely corroded and should not be used by District personnel or contractors (Photo 37). The



surfaces above the water surfaces were in poor condition with Vanda Level 2 and Level 3 conditions

observed on the roof plates and radial support beams (Photo 38). Several blisters and delaminations

were observed on the walls of the tank (Photo 39 and Photo 40) with VANDA Level 1 corrosion. It

appears that the overcoat applied over the factory coat has cracked and is flaking off. Most of the

coating on the roof is missing (Photo 41 and Photo 42). Two different types of outer perimeter

columns in VANDA Level 1 condition were observed (Photo 43 and Photo 44). Most of the columns

were similar to the one shown in Photo 44. The south upper roof plate has separated from the shell

and allowed water to leak out during overflow testing.

Photo 37. Top rung of the interior ladder has

failed and is in VANDA Level 4 condition.

Photo 38. VANDA Level 2 and 3 corrosion can

be found on radial support beams and roof

plates.

Photo 39. Typical blisters are on the wall and

the wall is in VANDA Level 1 condition.

Photo 40. Cracking and flaking of the

overcoat is seen on the interior walls.



Photo 41. Roof plates are in VANDA Level 2

condition.

Photo 42. Center roof column and roof plates

are in a VANDA Level 2 condition.

Photo 43. Base of an outer perimeter column

with steel plates welded to floor.

Photo 44. Base of an outer perimeter column

is in a VANDA Level 1 condition.


The exterior roof surfaces are chalking and exposing the red primer (Photo 45). The threads on the

bolts on the exterior of the tank have minor corrosion. Small trees are growing next to the tank (Photo

46) and may have to be removed if scaffolding or a manlift is used to coat the exterior of the tank.

There is evidence of bent shell plates due to seismic movements (Photo 47). Mildew or moss is

growing at the joints (Photo 48). This typically occurs on the north side of tanks and may indicate

moisture at the bolted joints.



Photo 45. The primer is exposed with VANDA

Level 1 condition at the bolts.

Photo 46. Trees are within four feet of the

tank and may have to be removed.

Photo 47. The upper wall shell plate on the north side of the tank is bending.

Photo 48. Moss or mildew is growing on the north exterior joints of the tank.

4.8 Paint Sample Analysis

Coating samples were collected from four of the six tanks that were evaluated by the project team.

Samples were collected from tanks that were constructed prior to 1985. The samples were tested for

17 heavy metals, except for mercury, according to EPA Method 6010B at Xenco Laboratories, an

environmental analysis lab in Houston, Texas. Mercury was tested per EPA Method 7471.

Table 4-1 summarizes the results of the five paint samples that were analyzed.



Table 4-1

Summary of Paint Sample Analysis

Cold Creek Tata Heavenly Iroquois No. 1

Metal

TTLC Maximum

Concentration (ppm)

Exterior, (ppm)

Exterior Wall

(ppm)

Interior Wall

(ppm)

Interior (ppm)

Exterior (ppm)

Antimony 500 BRL 8 BRL BRL 25 Arsenic 500 10 14 3 6 BRL Barium 10,000 2,390 2,850 9,510 14 2,840 Beryllium 75 BRL <1 BRL BRL BRL Cadmium 100 2 <1 46,800 BRL BRL Chromium 2,500 33 4,210 BRL 39 1,050 Cobalt 8,000 106 95 BRL BRL 35 Copper 2,500 26 33 BRL 92 14 Lead 1,000 226 46,800 14 9 42,100 Mercury 20 BRL BRL <1 <1 <1 Molybdenum 3,500 14 54 BRL BRL BRL Nickel 2,000 192 10 5 28 <1 Selenium 100 BRL 36 BRL BRL BRL Silver 500 BRL BRL BRL BRL BRL Thallium 700 BRL BRL BRL BRL BRL Vanadium 2,400 17 BRL BRL BRL BRL Zinc 5,000 11,600 6,670 347 19 243 ppm=parts per million N/A= Not Available BRL= Below Recording Limit

The cadmium concentration of the interior wall coating of the Tata Tank exceeds the Total Threshold

Limit Concentration (TTLC) per Title 22 California Code of Regulations (CCR) § 66261.24. The

chromium, lead, and zinc concentrations on the exterior coating of the Tata Tank also exceed the

TTLC limits. The Cold Creek chromium concentration also exceeded the TTLC limits. If the interior

and exterior coatings are completely removed, the waste that is generated will have to be tested per

the Toxicity Characteristic Leach Procedure (TCLP) before it can be transported and disposed of at a

waste site. If the waste exceeds the TCLP limits stated in Title 22 CCR § 66261.3, the waste must be

classified as hazardous waste and shipped to a hazardous waste disposal site.

The lead concentration on the exterior of the Tata and Iroquois No. 1 tanks warrants lead abatement

measures and will require a containment system since the tanks are surrounded by private homes if

the coatings are disturbed during overcoating or removal.

4.9 Dry-Film Thickness Results

Table 4-2 summarizes the results of the dry-film thickness measurements for the seven tanks that

were evaluated in April 2011. The range of coating thicknesses are given in the minimum and

maximum and an average was calculated for all the readings that were obtained.



Table 4-2

Summary of Dry-film Thickness Readings

Location Mils Arrowhead Christmas Valley

Cold Creek

Iroquois No. 1

Heavenly Stateline No. 2 Tata

Exterior Avg 12.9 8.3 7.6 10.3 9.6 11.3 5.21

Min 7.2 6.5 5.6 9.3 4.6 9.1 2.75

Max 17.3 12.2 13.3 15.9 18.3 14.2 9.0

Interior Avg - - - - - - 32.4

Min - - - - - - 17.0

Max - - - - - - 56.9 Mil= 0.001 inches

Generally coating thicknesses greater than 15 mils (0.015 inches) cannot be overcoated due to the

high possibility of cracking and peeling of the overcoat system. The Stateline No. 2 and Arrowhead

tanks can be overcoated since they are still protecting the primer and steel and do not exceed 15

mils. The exterior coatings on the Tata and Cold Creek tanks have reached the end of the design life

and should be removed and replaced.

4.10 Protective Coatings

Recoating and relining of the tanks may be undertaken during wet or humid weather and short

construction window. Condensation on the exterior surfaces of the tanks can form during cold or high

humidity days. For these reasons, V&A recommends evaluating coating products that are moisture-

tolerant, certified per the National Sanitation Foundation Standard 61 for drinking water, and have

curing times less than 56 hours before they can be immersed.

Below is a discussion of the various protective coatings that are available for this type of project.

4.10.1 Epoxies

Several formulations are available for epoxy coatings. This project will consider polyamide epoxies

and 100% solids epoxies. In general, 100% solids epoxies are more moisture-tolerant than 100%

solids polyurethanes during application and curing because they can be applied to damp surfaces

when there is no standing water or the humidity is less than 90%. Epoxies tend to pinhole, bubble, or

discolor when there is excessive moisture present on the surface or the humidity is greater than 90%.

Epoxies are also sensitive to temperature and mixing conditions during the coating application.

Polyamide epoxy coatings are typically utilized as a primer and/or intermediate coat in the protective

coating system. It is recommended that these types of coatings be applied on steel that has been

prepared to a minimum of SSPC-SP6 Commercial Abrasive Blast for non-immersion service and

SP10 for immersion service and surfaces that have had lead-based paint removed.



4.10.2 Polyurethanes

Moisture Cured Urethanes

Moisture-cured urethane (MCU) intermediate coats can be single-component coatings in which

isocyanate groups react with moisture from the air to polymerize while releasing carbon dioxide gas

as a byproduct. Due to this reaction, these products are more tolerant of surface moisture than other

urethanes. Relative humidity between 30% and 80% is required for this type of coating.

Aliphatic Polyurethanes

In addition to the MCU intermediate coat, aliphatic polyurethane exterior finish coats are typically

applied to steel structures to protect the epoxy undercoats from chalking and to provide some gloss

retention under sunlight (UV) exposure.

100% Solids Polyurethanes

The 100% solids polyurethane (PU) coatings have been commonly used as protective coating

systems for interior steel tank surfaces for water and wastewater. The fast-setting (drying) nature of

the 100% solids polyurethane coatings also means they are very suitable for high production rates.

Similar to 100% solids epoxies, polyurethanes are also very sensitive to temperature, humidity, and

mixing conditions during the coating application. These types of coatings have to be applied on steel

that has been prepared to a minimum of SSPC-SP10 Near White Metal Blast if the surfaces are to be

immersed. One hundred percent solids polyurethanes would be best suited for the Tata interior lining

because it can be built up to 125 mils (1/8-inch thick), which will cover up the bolted joints.



5 CONCLUSIONS

Arrowhead

A. The exterior surfaces of the Arrowhead Tank are in fair condition and may be overcoated. The interior lining of the Arrowhead Tank is in fair condition.

Christmas Valley

B. The exterior surfaces of the Christmas Valley Tank are in fair condition and can be overcoated. The interior lining of the Christmas Valley Tank has reached the end of its design life and should be replaced.

Cold Creek

C. The exterior coating on the Cold Creek Tank has reached the end of its design life and should be replaced. The interior lining of the Cold Creek Tank has reached the end of its design life and should be replaced.

Iroquois No. 1

D. The exterior coating on the Iroquois No. 1 tank roof has reached the end of its design life and should be replaced. The interior lining is in good condition.

Heavenly

E. The exterior coating of the Heavenly Tank has reached the end of its design life and can be overcoated. The interior lining is in poor condition and has reached the end of its design life.

Stateline No. 2

F. The exterior coating on the Stateline No. 2 Tank is in fair condition and may be overcoated. The interior lining of the Stateline No. 2 Tank is in fair condition.

Tata Tank

G. The exterior roof coating of the Tata Tank has reached the end of its design life and should be replaced. Although the exterior walls do not require the coating to be replaced, it may be more economical to remove and replace the exterior wall coating at the same time as the roof. The interior lining of the Tata Tank has reached the end of its design life and should be removed and replaced.

H. The exterior coating of the Tata Tank requires lead abatement and containment procedures during the removal of the existing coating.

General

I. The dry-film thickness measurements of the Arrowhead, Christmas Valley, and Stateline No. 2 Tanks indicate that an overcoat may be performed instead of complete removal of the existing coating.

J. One hundred percent solids epoxies or polyurethanes would be best suited for the Tata interior lining, which has bolted joints. These types of coatings are best for quick turnaround times due to weather or water demand.



6 RECOMMENDATIONS

Based on the conclusions of the field and laboratory analysis, V&A has the following

recommendations for STPUD to consider:

General

Exterior – When District crews are covering up graffiti, remove the existing spray paint as it acts

as a bond breaker. Otherwise the new coating will start peeling if the spray paint is not

removed. Inspect exterior coating every 5 years.

Interior – Clean the interior surfaces and conduct a dive inspection of the coatings of the tanks

every 5 years. If the tank surfaces exhibit severe corrosion, the tank should be drained and

an inspection of the steel with or without scaffolding is recommended as determined by the

height of the defects.

Arrowhead

A. Overcoat the exterior of the tank within the next 2 to 5 years.

B. Conduct another dive or dry inspection of the interior lining system in the next 5 to 10 years.

Christmas Valley

C. Overcoat the exterior in the next 5 to 10 years.

D. Remove and reline the interior surfaces within the next 0 to 2 years.

Cold Creek

E. Remove and replace the exterior coating within the next 2 years.

F. Remove and reline the interior surfaces within the next 2 years.

G. Repair or replace the level gauge indicator.

Iroquois No. 1

H. Remove and replace the exterior roof coating within the next 2 years.

I. Conduct another dive or dry inspection of the interior lining system in the next 5 to 10 years.

Heavenly

J. Overcoat the exterior coating in the next 2 to 5 years.

K. Remove and reline the interior surfaces of the tank within the next 2 years.

Stateline No. 2

L. Overcoat the exterior in the next 2 to 5 years.

M. Conduct another dive or dry inspection of the interior lining system in the next 5 to 10 years.

Tata

N. Do not use the interior ladder. Remove and replace the ladder immediately.



O. Remove and reline the interior surfaces with a 100% solids epoxy or polyurethane within the

next 2 years.

P. Remove and replace the exterior coating within the next 2 years.

Angora, Echo View, Forrest Mountain, and Country Club

Q. Reevaluate the interior and exterior linings per the General Recommendations given above.

Estimate of Probable Cost

Table 6-1 and Table 6-2 are an opinion of probable construction costs based on the recoating

recommendations mentioned above and the review of previous reports and dive videos for 21 tanks.

The Recoating Prioritization of the tanks was based on the amount of coating failures, VANDA

Corrosion Index Rating of the surfaces, and type of failures. STPUD may choose to prioritize the list

differently based on usage, available backups, or budgets. Angora, Country Club, Forrest Mountain,

and Echo View were not reviewed because STPUD indicated that the tank were recently constructed

or repainted. Keller No. 1 and No. 2 are to be replaced and were not evaluated either.

A $12 per square foot ($/sq. ft.) unit cost is estimated for lining all tanks with a polyamide epoxy and

$20/sq. ft. unit cost for recoating tanks that have lead-based paint. Unit costs should be increased to

$15/sq. ft. if a 100% solids epoxy is used to reline the interior of the tanks in order to account for the

higher material cost. Arrowhead, Christmas Valley, and Stateline No. 2 tanks may have the exterior

overcoated instead of complete removal of the existing coating. Other tanks may be overcoated.

However, if the existing coating exceeds 15 mils, it is recommended that it be completely removed

and a new coating be applied. A $7/sq. ft. unit cost is estimated for overcoating the existing coating

on tanks. The opinion of probable cost includes a containment system for lead abatement,

dehumidification, mobilization, materials, and labor for the recoating work.



Table 6-1

Interior Recoating Prioritization and Estimate of P robable Construction Costs

Name Interior Priority

Diameter(feet)

Height(feet)

Interior S.A.(sq. ft.)

Interior Unit Cost ($/sq. ft.)

Interior Probable Cost

Heavenly 1 71 37 16,171 $12 $ 194,056

Christmas Valley 2 30 38 4,995 $12 $ 59,942

Cold Creek 3 55 27 9,417 $12 $ 113,003

Gardner Mountain No. 2 4 38 25 5,253 $12 $ 63,033

Stateline No. 1 5 90 27.4 20,471 $12 $ 245,647

Flagpole No. 2 6 38 24 5,133 $12 $ 61,600

Tata 7 54.5 23.5 8,689 $12 $ 104,271

Stateline No. 2 8 120 27.4 32,949 $12 $ 395,388

Gardner Mountain No. 1 9 38 28 5,611 $12 $ 67,331

Flagpole No. 1 10 L=56 W=56H=10.67

2,390 $20 $ 47,802

Iroquois No. 1 11 40 35 6,912 $12 $ 82,938

Arrowhead 12 76 34 17,191 $12 $ 206,290

Forest Mountain 13 30 33 4,524 $12 $ 54,287

Country Club 14 55 20 8,207 $12 $ 98,489

Angora 15 38 31 5,969 $12 $ 71,628

Echo View 16 38.6 22.7 5,093 $12 $ 61,118

Keller No. 1 17 39 24 5,330 $12 $ 63,957

Keller No. 2 18 30 24 3,676 $12 $ 44,108

Iroquois No. 2 19 35 35 5,773 $12 $ 69,272

Lookout 20 41.5 28.75 6,454 $12 $ 77,443

H Street 21 34 16 3,525 $12 $ 42,298

Recoat in 0 to 2 years

Reevaluate in 2 to 5 years




Table 6-2

Exterior Surface Recoating Prioritization and Estim ate of Probable Construction Costs

Name Exterior Priority

Diameter(feet)

Height(feet)

Exterior S.A.(sq. ft.)

Exterior Unit Cost ($/sq. ft.)

Exterior Probable Cost

Heavenly 1 71 37 12,212$ 12 146,546$ Cold Creek 2 55 27 7,041$ 12 84,493$ Tata 3 54.5 23.5 6,356$ 20 127,128$ Flagpole No. 2 4 38 24 3,999$ 7 27,995$

Iroquois No. 1 5 40 35 5,655$ 20 113,097$

H Street 6 34 16 2,617$ 7 18,319$ Gardner Mountain No. 1 7 38 28 4,477$ 7 31,337$ Gardner Mountain No. 2 8 38 25 4,119$ 7 28,830$ Christmas Valley 9 30 38 4,288$ 7 30,018$

Arrowhead 10 76 34 12,654$ 7 88,580$ Forest Mountain 11 30 33 3,817$ 7 26,719$

Iroquois No. 2 12 35 35 4,811$ 7 33,674$

Lookout 13 41.5 28.75 5,101$ 7 35,707$ Stateline No. 1 14 90 27.4 14,109$ 7 98,762$ Country Club 15 55 20 5,832$ 7 40,821$ Stateline No. 2 16 120 27.4 21,639$ 7 151,475$ Angora 17 38 31 4,835$ 7 33,844$ Echo View 18 38.6 22.7 3,923$ 7 27,461$ Keller No. 1 19 39 24 4,135$ 7 28,946$ Keller No. 2 20 30 24 2,969$ 7 20,782$ Flagpole No. 1

N/AL=56 W=56

H=10.67 - - -

Recoat in 0 to 2 years




VA11-0079 Appendix A STPUD Final Water Tank Assessment Rpt

APPENDIX A – PREVIOUS REPORTS SUMMARY TABLE

water tank coating rehabilition assessment reportelcometer® 456 dft gauge .....7 appendices...

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