Tank_948_Final_(Q&A_27_Aug).pdf

www.corrtech-inc.com • (888)842-3944 • Offices in CT, MA, MD, NY

5-Year Water Storage Tank Inspection

Tank #948 Brevard County, FL

CorrTech Report No. 12896-FOR-01

Prepared For:

Patrick AFB 1060 South Patrick Drive

Patrick AFB, FL 32925

25 South Street Hopkinton, MA 01748

January 2018

STATEMENT OF LIMITATION

The conclusions presented in this document are based on the services described and not on tasks or procedures beyond the scope of the described procedures or the time and budgetary constraints imposed by the contract limitations.

CorrTech, Inc. has performed this assessment in a professional manner using that degree of skill and care exercised for similar projects under similar conditions by reputable and competent consultants, and in accordance with the procedures established within CorrTech’s quality assurance, quality control protocol.

CorrTech, Inc. shall not be responsible for conditions or consequences arising from relevant facts that were concealed, withheld or not fully disclosed at the time the evaluation was performed.

Report Written by: Ted Lund NACE CIP Level III #050

July 2019

Report Reviewed by: Scott Paul, P.E.

FL P.E. Lic. No: 75784

NACE Corrosion Specialist No. 4163 July 2019

TABLE OF CONTENTS

INTRODUCTION

EXECUTIVE SUMMARY

OBSERVATIONS

RECOMMENDATIONS

APPENDIX I

Photographs

APPENDIX II

Dry Film Thickness Readings

Patrick Air Force Base

INTRODUCTION

On January 23, 2018 CorrTech representatives Bob Meskill and Ben Palmer performed a corrosion and structural assessment of the exterior and interior of the Patrick Air Force Base Tank #948 in accordance with Florida Administrative Code 62.555.350. The inspection was conducted to establish the current condition of the tank's coatings and steel substrate. The tank inspected included:

♦ 400,000 Gallon Tank #948

This work was completed under an agreement between Patrick AFB and CorrTech referenced under Patrick Airforce Base contract no. FA252117C0027 and performed under CorrTech project no. 12896.

The interior of the tank was inspected after it had been drained and the sediment had been removed. Digital cameras were used to photograph the interior coating condition.

The exterior portions of the tank were inspected by walking the roof and shell portions that were accessible from the ground.

The objectives of the assessment were to:

1. Perform field inspections and tests to assess the structural and coating integrity of the tank.

2. Review the safety compliance of tank ladders and access.

3. Review sanitary conditions and protection

4. Provide recommendations for rehabilitation.

EXECUTIVE SUMMARY

The condition and recommendations for the tank are briefly summarized in this section. For detailed information regarding detailed tank conditions and the specific recommendations please refer to the designated section for the tank.

Cathodic protection system should be energized if the tank is full even if not in active service.

Pinpoint corrosion is beginning to form.

Spot coating repairs for exterior corrosion and repairs to corroding areas around cathodic protection covers would preserve the overall tank coating and appearance.

This tank should be inspected in 2023 in accordance with current AWWA standards.

OBSERVATIONS

Photos provided in the report were created from a digital camera. The copies in the report provide a reference for our comments.

400,000 Gallon Tank #948

This tank is located on the Patrick AFB in Brevard County, Florida. The tank is a welded steel elevated double ellipsoid. Estimated overall height of the tank is 130-ft with the water vessel 44-ft diameter and 35-ft from dome to bowl. Tank site is fully fenced in and the access gates have locks in place.

INTERIOR

The interior of the tank was accessed through the roof hatch and interior ladder with the tank empty. Roof hatch is a 29.5-in square with a 4-in sanitary neck and a 1.75-in hatch overlapping cover. There is no lock or securing pin in place on the roof hatch.

Roof (ceiling)

Edge corrosion has formed along 15% of the roof seams. Edge corrosion has caused delamination around the cathodic protection covers in the roof. There is shadowing in the coating of the roof. It appears touch ups were made with spray paint near several of the cathodic protection covers. Light was visible around the cathodic protection covers due to them not being positioned and sealed properly.

Ladders

There is an interior ladder that runs from the roof hatch to the bowl of the tank. Ladder has non-skid rebar type rungs. Ladder is only connected at roof and floor there are no intermediate wall braces. No signs of metal loss or section loss was observed on the ladder.

Shell/Bowl

Active corrosion has formed on 1% of the tank bowl and shell. Areas of dark staining are visible around the riser opening. Lighter areas of stained spots are visible throughout the bowl of the tank. It appears that at the time of the last coating application water may have contacted the new coating before it was fully cured causing the discoloration and staining. No adhesion loss or coating loss was observed on the shell or the bowl of the tank.

Prior to removal there was an accumulation of 0.25-in of sediment in the bowl of the tank.

Riser

Riser pipe had edge corrosion forming on 2% of the weld seams. At the base of the riser sediment had accumulated up to 0.5-in in depth which was removed prior to inspection. Areas of uncured coating were observed at the base of the riser.

Inlet/Outlet

A combination inlet and outlet pipe is located at the base of the riser. It is equipped with a sediment ring.

Cathodic Protection

A roof hanging cathodic protection system is installed in the tank. The impressed current anode wires appear to be intact. Due to the tank being empty at the time of the inspection the system could not be tested. CP system operation will be tested at the next bi-monthly read schedule.

EXTERIOR

Roof

Active corrosion was observed on 2% of the roof forming mostly around the vent and the cathodic protection covers. No significant adhesion loss or coating loss was observed on the roof.

Dry film thickness readings were taken on the exterior roof coating. The average reading was

20.69 mils with a minimum reading of 14.1 mils and a maximum reading of 44.6 mils, see Appendix II.

No destructive adhesion testing was conducted due to the age and condition of the coating.

Vent

A central finial vent is installed on the roof of the tank. The vent measures 24-in in diameter with a 4.5-in flange. There is intact fine mesh screening and the vent cap is 7-in above the roof plates.

Ladders and Balconies

The roof of the tank is accessed through the use of a leg ladder that runs from the ground and a separate shell ladder that runs up from the balcony. The ladders have a rung to rung distance of 12-in and are 16-in wide. The shell ladder is mounted 8.5-in from the shell and the leg ladder is mounted 8-in from the leg. The ladder has a locking ladder guard and a notched rail safety climb system.

The shell balcony is 30-in wide and has localized areas of surface corrosion. The railings of the balcony have a 42-in tall top rail, a mid-rail at 24.5-in, and a 6-in toe kick plate. Leg ladder opening is protected with a self-closing gate.

Overflow Pipe

Overflow exists the roof dome with an anti-vortex plate and consists of an external pipe that runs from the top of the tank to the ground. The 6-in pipe has a flapper valve installed and fine screening.

Shell

One very minor area of active corrosion was observed on the shell of the tank. An air bubble was observed under the vinyl Air Force decal. There was no visible adhesion loss or coating loss on the shell.

Dry film thickness readings were taken on the shell. The readings averaged 10.85 mils with a minimum reading of 6.9 mils and a maximum reading of 24.5 mils, see Appendix II.

Bowl

Edge corrosion was observed along 5% of the bowl seams near the riser pipe attachment collar.

No coating loss or adhesion loss was observed on the bowl of the tank.

Legs and Riser

There are seven (7) 30-in diameter tubular support legs. A single riser pipe is located at the center of the tank. The riser pipe measure 6-ft in diameter. Edge corrosion was observed on 5% of the riser pipe and leg weld seams.

Dry film thickness readings were taken on the legs and riser coating. The average reading was

14.74 mils with the minimum reading at 8.3 mils and a maximum reading of 30.4 mils, see Appendix II.

Tension Rods

Tension rods run between legs for support. Rod position was observed with the tank full and empty. The 1.75-in rods were intact, however when the tank was full one had visible bowing and three appear to not have enough tension. When the tank was emptied all the rods were pulled tight. The clevis points and turn buckles were intact with no excessive corrosion or metal loss.

Foundation

Each leg has a pad that measures 52-in by 52-in and 10 to 15-in exposed above ground. The riser pipe foundation ring wall measures 92-in by 92-in and is 12-in above ground. There was no evidence of new spalling or racking on the foundations. The coating was intact on the foundation as well.

Each leg has eight (8) anchor bolts, two that are 1.5-in in diameter and six that are 1.25-in in diameter. The larger anchor bolts sit in 4.5-in by 5-in by 12-in anchor chairs. The remaining bolts sat in 5-in by 8-in chairs.

The riser pipe has four 1.5-in anchor bolts that sit in 4.5-in by 4.5-in by 12-in chairs.

Riser Manhole

An 18-in by 12-in oval pressure style manhole is installed in the riser pipe.

RECOMMENDATIONS

Cathodic protection system should be energized if the tank is full even if not in active service.

Pinpoint corrosion is beginning to form. All roof CP access covers must be properly positioned and caulked to provide a solid sanitary seal.

Spot coating repairs should be made at each of the cathodic protection access holes on the roof to address corrosion. Coating application can be completed using quick curing moisture tolerant NSF-61 products.

Corroding locations on the exterior that can be reached from the ground, ladders, balcony and roof should be power tool cleaned to bare metal and then receive two coats of epoxy and a finish coat of urethane to maintain the tank appearance and overall coating life. Exterior work can be accomplished with tank in service if weather is correct.

Appendix I Photographs

Patrick AFB - Tank #948

DP#01

Tank overview

DP#02

Tank overview, overflow side

DP#03

Tank overview, logo side

DP#04

6-in overflow pipe with flapper valve

DP#05

Intact screening on overflow pipe

DP#06

Typical condition of leg foundation pad

DP#07

Anchor bolts for leg foundation

DP#08

Typical condition of tank tension rods

DP#09

Tension rod clevis point attachements on leg

DP#10

Typical coating condition on tank leg

DP#11

2-in Sample tap on riser

DP#12

Intact coating on tank leg base

DP#13

Active corrosion along tank leg base plate edge

DP#14

Intact coating on tension rod clevis point

DP#15

Tension rods with no visible bowing

DP#16

Typical tension rod clevis yoke and pin

DP#17

Typical tension rod turnbuckle

DP#18

Riser pipe 18-in by 12-in pressure style hatch

DP#19

Typical condition of riser pipe coating

DP#20

Active corrosion on riser pipe anchor chair

DP#21

Cathodic Protection system rectifier

DP#22

Leg ladder with rung guard

DP#23

Leg ladder with notched rail safety climb

DP#24

Typical condition of bowl coating

DP#25

Edge corrosion on bowl riser weld seams

DP#26

Shell balcony

DP#27

Balcony with self-closing ladder gate

DP#28

Shell ladder

DP#29

Typical condition of tank shell and overflow pipe

DP#30

Typical condition of balcony

DP#31

Typical condition of shell coating

DP#32

Intact coating along horizontal weld seam

DP#33

Bubble in vinyl logo

DP#34

Minor area of corrosion forming on tank shell

DP#35

Surface corrosion on balcony

DP#36

Intact shell coating

DP#37

Roof overview and fixed ladder with rail climb

DP#38

Intact roof coating

DP#39

Intact roof coating with no active corrosion or adhesion loss

DP#40

Roof overview with CP access covers

DP#41

Roof hatch with interior ladder

DP#42

Overcoated pitting on tank roof

DP#43

Active corrosion forming on roof ladder

DP#44

Cathodic protection cover with edge corrosion

DP#45

Overcoated pitting

DP#46

Central 24-in roof vent

DP#47

Active corrosion on vent flange

DP#48

Intact vent screening

DP#49

Interior tank roof coating condition, prior to draining

DP#50

Tank roof with intact coating

DP#51

Roof rafter with no signs of edge corrosion

DP#52

Roof seams with no signs of edge corrosion

DP#53

Typical condition of roof coating

DP#54

Intact coating on rafter and roof seams

DP#55

Intact coating with no signs of adhesion loss

DP#56

Interior ladder

DP#57

Open riser hatch

DP#58

Interior of the riser pipe before sediment removal

DP#59

Interior riser pipe condition

DP#60

Sediment staining on riser pipe

DP#61

Interior tank bowl before sediment removal

DP#62

Interior roof with edge corrosion around cathodic protection access holes

DP#63

CP cover opening with spray paint touch up

DP#64

Sediment accumulation in bowl of the tank prior to wash out

DP#65

Interior ladder base

DP#66

Cathodic protection reference cells

DP#67

Sediment accumulation of 0.25-in

DP#68

Overflow pipe opening

DP#69

Tank bowl after sediment removal with staining

DP#70

Edge corrosion around cathodic protection hole

DP#71

Ambient light through cp cover that is not fully sealed

DP#72

Spray paint touch up near cp cover

DP#73

Active corrosion on tank roof knuckle

DP#74

Active corrosion along tank knuckle

DP#75

Tank bowl overview post washout

DP#76

Coating cracking with corrosion on tank bowl

DP#77

Active corrosion on tank bowl

DP#78

Active corrosion on tank bowl

DP#79

Dark staining around riser opening with grate in place

DP#80

Staining on tank bowl

DP#81

Staining in tank bowl coating

DP#82

Discolored coating on tank bowl

DP#83

Staining on tank floor coating

DP#84

Riser base and inlet pipe after sediment removal

APPENDIX II

Dry Film Thickness Readings

- 1 -

B63 Leg B64 Shell B65 Roof

Patrick AFB Tank #948 Summary # x σ ↓ ↑

PosiTector 6000 Coating Thickness (mils) 135 15.43 5.87 6.9 44.6

- 2 -

- 3 -

- 4 -

B63 Created: 2018-01-23 12:56:49

PosiTector Body S/N: 722083 Probe Type: PosiTector 6000 FS

Probe S/N: 178008 CAL: Cal 1

Summary # x σ ↓ ↑

Thickness (mils) 45 14.74 4.24 8.3 30.4

Readings # Thickness Time

(mils)

1 14.1 2018-01-23 12:56:51 2 13.4 12:56:52 3 13.4 12:56:53 4 14.8 12:56:59 5 17.0 12:57:00 6 15.0 12:57:01 7 11.8 12:57:08 8 11.6 12:57:09 9 13.7 12:57:10

10 30.4 12:57:34 11 25.6 12:57:35 12 26.2 12:57:36 13 14.5 12:57:40 14 12.4 12:57:41 15 10.9 12:57:42 16 13.3 12:57:50 17 12.2 12:57:51 18 12.2 12:57:52 19 11.3 12:57:57 20 11.7 12:57:58 21 14.0 12:57:59 22 14.3 12:58:06 23 14.7 12:58:07 24 15.8 12:58:08 25 11.6 12:58:15 26 11.6 12:58:17 27 11.2 12:58:17 28 8.3 12:58:23 29 12.0 12:58:24 30 11.4 12:58:27 31 14.2 12:58:34 32 18.9 12:58:35 33 12.9 12:58:36 34 14.2 12:58:47 35 14.9 12:58:48 36 18.7 12:58:49

- 5 -

B63 Readings # Thickness Time

(mils)

37 18.4 12:58:53 38 18.1 12:58:54 39 20.3 12:58:55 40 15.2 12:59:00 41 16.1 12:59:01 42 15.0 12:59:02 43 12.7 12:59:07 44 11.3 12:59:08 45 11.9 12:59:09

- 6 -

- 7 -

B64 Created: 2018-01-23 14:06:09

PosiTector Body S/N: 722083 Probe Type: PosiTector 6000 FS

Probe S/N: 178008 CAL: Cal 1

Summary # x σ ↓ ↑

Thickness (mils) 45 10.85 3.81 6.9 24.5

Readings # Thickness Time

(mils)

1 11.2 2018-01-23 14:06:11 2 10.6 14:06:12 3 10.7 14:06:13 4 9.6 14:06:19 5 8.5 14:06:20 6 9.0 14:06:21 7 9.8 14:06:34 8 8.3 14:06:36 9 9.1 14:06:37

10 22.1 14:06:43 11 24.5 14:06:44 12 24.0 14:06:45 13 10.2 14:07:34 14 10.7 14:07:35 15 12.1 14:07:36 16 9.5 14:07:43 17 12.4 14:07:44 18 9.1 14:07:45 19 11.4 14:08:15 20 8.7 14:08:16 21 10.1 14:08:17 22 10.6 14:08:22 23 10.5 14:08:23 24 8.9 14:08:24 25 11.9 14:09:06 26 12.0 14:09:07 27 12.1 14:09:08 28 13.7 14:09:12 29 12.7 14:09:13 30 12.6 14:09:14 31 8.9 14:09:30 32 9.2 14:09:31 33 6.9 14:09:32 34 8.1 14:09:34 35 8.5 14:09:35 36 7.0 14:09:36

- 8 -

B64 Readings # Thickness Time

(mils)

37 11.4 14:10:16 38 9.3 14:10:17 39 8.4 14:10:18 40 9.7 14:10:36 41 10.6 14:10:37 42 11.0 14:10:39 43 7.7 14:11:19 44 7.8 14:11:20 45 7.1 14:11:21

- 9 -

- 10 -

B65 Created: 2018-01-23 14:40:30

PosiTector Body S/N: 722083 Probe Type: PosiTector 6000 FS

Probe S/N: 178008 CAL: Cal 1

Summary # x σ ↓ ↑

Thickness (mils) 45 20.69 4.70 14.1 44.6

Readings # Thickness Time

(mils)

1 16.1 2018-01-23 14:40:34 2 16.2 14:40:35 3 18.9 14:40:36 4 23.6 14:40:39 5 23.6 14:40:40 6 23.9 14:40:41 7 19.5 14:40:43 8 17.6 14:40:44 9 17.5 14:40:45

10 18.5 14:40:47 11 19.1 14:40:48 12 16.3 14:40:49 13 18.7 14:40:56 14 17.5 14:40:57 15 19.5 14:40:58 16 20.6 14:41:02 17 18.2 14:41:04 18 19.6 14:41:05 19 24.1 14:41:13 20 21.4 14:41:14 21 18.6 14:41:15 22 29.4 14:41:17 23 23.8 14:41:18 24 44.6 14:41:19 25 16.2 14:41:41 26 21.5 14:41:42 27 19.8 14:41:43 28 19.2 14:41:45 29 20.4 14:41:45 30 19.6 14:41:46 31 14.1 14:41:49 32 15.3 14:41:50 33 16.6 14:41:51 34 22.0 14:41:56 35 22.8 14:41:57 36 21.5 14:41:58

- 11 -

B65 Readings # Thickness Time

(mils)

37 19.3 14:42:06 38 18.7 14:42:07 39 21.7 14:42:08 40 24.2 14:42:11 41 21.7 14:42:12 42 23.3 14:42:13 43 21.4 14:42:16 44 21.9 14:42:17 45 23.1 14:42:18

- 12 -