Tank 1935 Evaluation - Guam Power Authority

GUAM POWER AUTHORITY

PITI TANK FARM

TANK 1934 INSPECTION REPORT

Tank System Integrity Testing Report

August 2006

GPA TANK 1934 INTEGRITY TESTING REPORT

TABLE OF CONTENTS

ES EXECUTIVE SUMMARY 1.0 INTRODUCTION 1.1 Background 1.2 Site Description 1.3 Inspection Description 2.0 TANK BOTTOM INSPECTION 2.1 Bottom Plating 2.1.1 Bottom Plate Fillet Weld 2.1.2 Shell-to-Bottom Plate Fillet Weld 3.0 TANK SHELL INSPECTION 3.1 Tank Shell 3.2 Tank Shell Appurtenances 3.2.1 Manholes 3.2.2 Access Openings 3.2.3 Overflow Vents 3.2.4 Pipe Nozzles 3.2.5 Stairway 3.2.6 Liquid Level Sensor 3.2.7 Wind Girders 3.2.8 Ground Strap 3.2.9 Gate Valves 4.0 TANK ROOF INSPECTION 4.1 Roof Plating 4.2 Roof Top Appurtenances 4.2.1 Gooseneck Vents 4.2.2 Access Openings 4.2.3 Sampling Port 4.2.4 Painter’s Hitch 4.3 Roof Support Framing 5.0 TANK IN-PLANE LEVEL SURVEY 6.0 CATHODIC PROTECTION EVALUATION 7.0 LEAK DETECTION EVALUATION

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8.0 RECOMMENDATIONS

8.1 Tank Bottom 8.2 Tank Shell 8.3 Tank Roof 8.4 Appurtenances 8.4.1 Tank Roof 8.4.2 Tank Shell 8.5 Cathodic Protection System 8.6 Leak Detection System 8.7 Tank Inspection Program Tables 1.0 Ultrasound Thickness Measurements – Floor 2.0 Bottom Plate Pitting Assessment 3.0 Ultrasound Thickness Measurements – Shell 4.0 Ultrasound Thickness Measurements – Roof 5.0 Repair Quantities Figures 1.0 Roof Plate Layout 2.0 Roof Framing Layout 3.0 Bottom Plate Plan 4.0 Shell Plate Layout 5.0 Column Foundations 6.0 Tank Shell Thickness 7.0 Tank Roof Thickness Appendices Appendix A – Administrative Order – Scope of Work Appendix B – Minimum Thickness Calculation Appendix C – Tank Level Survey Results Appendix D – Tank Inspection Pictures Appendix E – Tank Description

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ES EXECUTIVE SUMMARY Tank 1934 was determined to be in fair condition, and with the implementation of the

recommended repairs can be suitable for service without the requirement for major reconstruction. Based on the tank inspection, the following are the recommendations for the repair of the tank.

Tank Bottom Plating:

Some pitting was noted on the tank bottom plates. The deeper pits will require repair in the form of welding. Where pitting is extensive (six locations), doubler plates of various sizes are required. Leaks were found in some of the fillet welds connecting the bottom plates as well as the shell-to-bottom plate fillet weld. These welds will require repair. The tank bottom plate thickness readings indicate the bottom plates are acceptable for continued use.

Tank Shell: The tank shell is in good condition with no major corrosion cells or loss in plate

thickness. There does not appear to have ever been a coating on the interior shell. The interior shall be sand blasted and a new coating system applied to the entire interior shell. The coating on the exterior side exhibits corrosion in some areas and shall be entirely sand blasted and recoated. Repairs of various tank shell appurtenances are necessary. The items to repair include: manholes, access openings, overflow vents, pipe nozzles, stairway, and liquid level sensor. Additionally, the wind girder shows evidence of deep pitting in ten areas that need repair using lap-welded repair plates.

Tank Roof: The tank roof plating is in fair condition with adequate plate thickness. Paint blisters on

the exterior side of the plating are present as well as a number of fillet welds that are defective. It is recommended that the roof exterior be sand blasted and recoated. The underside of the roof plating has never been painted, and a new coating system is not recommended. However, the overflow vent that was dislodged during water blasting activities needs repair.

The tank channel roof rafters are in good condition as well as the supporting wide flange

beams with no visible deterioration or deflection. The only remedial repair work required is replacement and re-welding of eleven loose roof rafter spacers. A new coating system is not recommended for the roof rafters and supporting beams.

The steel channel columns supporting the roof beams as well as the foundation at the

base of each column are in good condition. However, a new coating system is recommended for the columns.

Leak Detection System:

A new leak detection system is currently under construction for both Tank 1934 and 1935 by the Tank 1935 contractor.

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Cathodic Protection System:

A new cathodic protection system was installed for both Tank 1934 and 1935 by the Tank 1935 contractor.

Oil Water Separator Repair: Repairs for the oil water separator were completed by the Tank 1935 contractor.

1.0 INTRODUCTION

1.1 Background

Guam Power Authority (GPA) owns two bulk fuel storage tanks, 1935 and 1934, located in Piti Tank Farm in the Municipality of Piti between the Atlantis Submarine pier and the former Navy Power unit on the Piti Channel. These tanks are used to supply fuel to the Cabras and the Tanguisson Power Plant located adjacent to the tank farm. GPA has contracted the operation of the two-tank facility to Peterra Inc. The tanks and associated infrastructure were completed in 1976 by the United States Military and resides on compacted coral limestone fill with no previous history of hydrocarbon contamination. The operations at the site include the storage of fuel oil, transfer of fuel oil into and out of the facility, and the processing of oily water. The tanks have been in service continually since construction was completed except for a period of time while the facility was transferred from military to civilian control. The type of fuel stored in these two tanks is Fuel Oil #6, or Bunker Fuel C. Fuel Oil #6 is a mixture of petroleum distillate hydrocarbons and has a boiling point greater than 400 degrees Fahrenheit. This fuel is commonly broken into two categories depending on the relative levels of sulfur contained in the fuel. High sulfur fuel, also known as sour fuel, is more corrosive and often has increased sulfur levels in stack emissions. The second type fuel is low sulfur fuel also known as sweet fuel. Both of these fuels are used at the Power Plants. Previously both of these fuels were mixed between the two fuel storage tanks on site. This practice was stopped some years before and Tank 1934 is now used to store the low sulfur fuel. These tanks have not been drained and inspected prior to this report so a base line of corrosion cannot be established. In addition, no construction records or record drawings for the tanks could be located. In February 2001 the United States Environmental Protection Agency (USEPA) Region IX issued a Unilateral Administrative Order For Piti Tank Farm to GPA to “perform abatement activities necessary to address conditions that may present an imminent and substantial endangerment”. These abatement activities “require integrity inspections, maintenance, installation of leak detection and repair of cathodic protection.”

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Due to continued operations at the Power Plants, one tank is to be inspected and repaired at a time. PSC Industrial Services Group is the contractor that has been retained by GPA to clean the tank. Winzler & Kelly Consulting Engineers has been retained to perform the tank inspection and repair reports. This report is the result of the integrity testing and inspection of tank 1934 in accordance with the Scope of Work issued in Appendix A of the Administrative Order. This Scope of Work is included within this report in Appendix A.

1.2 Site Description

The two bulk storage tanks at the Piti Tank Farm are approximately 48 ft high with a diameter of 200 ft, having capacity of approximately 254,000 barrels each. They are supplied by a 24” above-ground pipeline that is interconnected to the U.S. Navy and Shell Tank farms. The supply line terminates with a double gate valve at Tank 1935 and a single gate valve at Tank 1934. Discharge from the tanks is through a 12” pipeline with a gate valve at the tank discharge port. This piping is connected to a pump manifold that distributes fuel to GPA Cabras and Tanguisson Power Plants. Tank 1935 and the oil-water separator (OWS) situated within the containment berm of tank 1934 has been repaired in accordance with the Scope of Work in the Administrative Order. 1.3 Inspection Description Tank 1934 was drained of fuel and cleaned in accordance with the “Tank Cleanout Work Plan” dated September 2003 and developed for the sludge removing and cleaning of both Tank 1934 and Tank 1935 by PSC Industrial Group. The contractor will remain on site to assist in the inspection by providing compressed air, scaffolding in the interior of the tank and general support tasks. The tank inspection was conducted in accordance with the “Work Plan For Life Extension and Refurbishment of the GPA Bulk Storage Tanks 1934 & 1935 for the Piti Fuel Tank Farm, Guam” dated April 2003. Island Certs personnel conducted the structural evaluations, tank bottom leak evaluations (vacuum box testing) and tank inspections in accordance with American Petroleum Institute (API) reference standard 653. Island Certs personnel also conducted the ultrasonic thickness measurements, coating thickness. Pit depth readings were performed by a Winzler & Kelly engineer with GPA personnel. Prudencio R. Balagtas & Associates performed the tank level survey. All tank inspections and evaluations were conducted in accordance with API Standard 653 “Tank Inspection, Repair, Alteration, and Reconstruction”. The results of this inspection are presented in this report.

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2.0 TANK BOTTOM REPAIRS

2.1 Tank Bottom Plating The tank bottom plating was found to be in fair condition, but in need of various repairs. There was evidence of pitting on the floor plates and a visual inspection found that no through pitting had occurred. There was no remaining evidence of a coating system on the floor and a scale of corrosion product had formed over the plates. This scale was removed by power grinding at the locations used for ultrasonic thickness and pit depth measurements. There are four water sumps located on the tank floor. These sumps are to collect water and then discharge it through the nozzles located on the shell. These sumps are 58 inches in diameter and approximately three feet deep. A six-inch pipe rises out of the sumps and connects to the discharge nozzle. These sumps need further cleaning in order for the inspector to perform the inspection. In some areas the bottom plating does not slope uniformly to the sumps resulting in small amounts of water ponding on the tank bottom. A large number of plates were not bearing on compacted fill below the tank, and exhibited a springing characteristic when walked upon. These areas were discovered by feeling the movements of the plate when walked upon. When the tank is operational and full of fuel this condition should be eliminated. The ultrasonic thickness measurements were obtained using a Panametrics Epoch LT Digital Flaw detection and Panametrics D709-RM, 5Mhz, 0.50” diameter dual element transducer. These instruments utilize a “pulse-echo to echo” circuit wherein a short duration electrical pulse excites a piezoelectric transducer. This meter is capable of reading steel plate thickness without removal of coatings. The transducer emits ultra high frequency sound waves that are transmitted to the test material through a couplant such as glycerin, water, or oil that is placed between the test material surface and the transducer. Sound waves pass through the test material and reflect back through the material from the opposite face. The transducer receiver converts the sound wave to electrical pulses. The time (t) for sound travel is the total time between pulse and echo minus the transducer delay time. The material thickness (y) is determined by the following equation:

Y=Vt/2

Where V is the velocity of sound through the material. The velocity of sound through low carbon steel is generally consistent and can be verified and programmed into the gauges using specially manufactured, steel calibration blocks traceable to NBS standards. Approximately 800 readings were taken and the results are uniform over the tank bottom. The general thickness of the plates is 0.2724”. No thickness readings were below the API

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653 minimum allowable 0.1” thickness requirements. See Table 1 for a listing of the plate bottom thickness readings. The pit depths were taken on the floor plates using a pit depth gauge. A pit depth gauge is a mechanical gauge that measures the difference between the bottom of a pit and the surrounding plate. Pitting varies over the bottom of the tank and on some plates. The results of these measurements are in Table 2. After the floor is sand blasted in entirety, more areas may become evident where repair is necessary.

3.0 TANK SHELL REPAIRS

3.1 Tank Shell

The tank shell is in good condition. There is no evidence of buckling or deformation of the shell. The exterior surface of the shell has surface rust in some areas, as did the wind girder, stairwell and level gauge. This rust did not appear to be significant or to have caused pitting; however, GPA will require sand blasting and recoating of the entire tank shell exterior and appurtenances.

The thickness of each shell plate was measured by an ultrasonic thickness gauge. All six courses were measured with the upper courses measured using a man basket apparatus. These plate thickness values are in Table 3.

The average of the 21 measurements taken on the bottom shell course was 1.138 inches and the lowest reading was 1.120 inches. No precise previous information is available for shell plate thickness to determine original shell thickness or shell deterioration rates. A calculation for the minimum thickness required by API 653 for the shell bottom course is provided in Appendix B. The minimum allowable thickness of the bottom shell course was calculated to be one inch (tmin = 1.00 inches). All measurements on the base course exceeded this thickness.

The thickness of each measurement on the shell plate is shown in Figure 6.0. There are areas along the foundation seal where standing water and vegetation are present. These areas will need to be addressed during repair. The foundation was found to have numerous areas of asphalt failure due to settlement. Numerous areas under the projection plate have small voids from erosion. These areas should be repaired utilizing epoxy grout or similar material to prevent accelerated corrosion of the steel reinforcement and to permit drainage away from the tank. No moisture barrier presently exists, allowing water to enter the tank bottom, resulting in

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accelerated corrosion of the projection plate. A seal should be installed after any projection plate repair.

3.2 Tank Shell Appurtenances

Several different types of appurtenances are attached to the tank shell. Each component was visually inspected for soundness of welds and signs of corrosion. The results are as follows.

3.2.1 Manholes

There are four manholes or entrance points, see Figure 4.0 for the locations. These consist of a 48-inch diameter circular entrance with a doubler plate stiffener on the shell plate. The manhole protrudes from the plane of the shell with a spool piece and has a flanged cover with approximately 35 – 3/4” bolts. Each manhole was in good condition with only minor corrosion at points where the coating had failed.

3.2.2 Access Openings

There is one access opening through the tank shell that consists of a doubler plate bolted over an opening, see Figure 4.0 for the location. This opening is approximately 57 inches tall and 170 inches wide with 160 – 1 ¾” bolts. There was no indication of product leakage, but a new gasket will be required when upon reinstallation of the plate. 3.2.3 Overflow Vents

There are eight overflow vents around the perimeter of the tank. The overflow vents consist of a funnel inside the tank that is at the maximum liquid level within the tank. This funnel reduces to an eight-inch pipe that then protrudes out the tank at the top shell plate course and then runs to within a foot of the ground terminating at a 22.5 degree bend. These overflows are designed to relieve interior pressure that could occur due to overfilling. One of these overflow vents is the lowest of the vents and is designed to discharge product first. This vent is connected to above-ground piping through a gate valve and is connected to the tank discharge piping. No seepage was noted at any of the connections. Some of the exterior overflow vents exhibit major corrosion on the bottom bent portion of the vent. One of the overflow vents inside the tank became dislodged during water blasting activities and will require repair. The repair will include installation of a 48 inch x 12 inch x ¼ support bracket and weld in a 12 inch Sch. 80 elbow.

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3.2.4 Pipe Nozzles

There are five pipe nozzle connections protruding from the base course of the shell. These nozzles are approximately six inches in diameter terminating at a gate valve and a blind flange. Each nozzle is in good condition with minor corrosion due to point failures of the coating system. 3.2.5 Stairway

One stairway extends up the side of the tank to provide access to the roof. A small platform is located at the top of the stairway and is level with the tank roof. The stairway consists of metal grate steps welded to the tank shell and metal handrails welded to the steps. The stairway and platform are in fair condition with minor corrosion due to point failures of the coating system.

3.2.6 Liquid Level Sensor

One liquid level sensor is located on the exterior side of the tank in the middle of a vertical black coating stripe. The level sensor was manufactured by Varec International. The sensor is attached from the roof of the tank to hang a float in the interior of the tank. Several of the level support hangers exhibit severe corrosion due to point failures of the coating system. The top 2 brackets are corroded to extent of total metal loss and will require replacement; the remaining 5 have minor corrosion.

3.2.7 Wind Girders

Two wind girders or shell stiffeners are located near the top of the tank and extend for the entire circumference of the tank. These girders consist of L6x6x3/4 angles spaced vertically at 6’-3” and are welded to the top portion of the tank shell. Welded plate stiffeners help support the angles. The wind girders were inspected from a suspended man basket for entire circumference of the tank. Some of the welds are in need of repair and the coating system at several joints has failed and corrosion has propagated to shell plate base metal, resulting in deep pitting. These will require repair.

3.2.8 Ground Strap

All earthing straps are intact.

3.2.9 Gate Valves

No leakage is evident at the gate valves.

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4.0 TANK ROOF INSPECTION

4.1 Roof Plating

The tank roof plating is in poor condition. An exterior visual inspection indicated that there are several areas of coating failure at lap fillet welds, resulting in weld corrosion. The weld was also found to be intact at the circumference where the roof plates are welded to the angle stiffener that extends around the tank perimeter. There are 19 locations where the coating has failed resulting in severe corrosion at the circumference where the roof plates are welded to the angle stiffener that extends around the tank perimeter. These areas will require abrasive blasting to clean base metal, evaluating for metal loss and re-coating. Weld repair is minimal, approximately 3 feet. This should be confirmed after removal of active corrosion. Surface rust and small blisters are evident on the roof plates. These defects do not affect the integrity of the roof plating and are easily repaired; however, it is recommended that the roof be sand blasted and recoated. Sixty four tank roof plating thickness measurements were taken around the perimeter of the roof, twenty-eight thickness measurements were taken on a 99 foot radius, thirty thickness measurements were taken on a 50 foot radius and six thickness measurements were take on a 10 foot radius. See Table 4 for roof thickness measurements. The average thickness of the roof plating was 0.254 inches with a minimum reading of 0.225 inches. This corresponds with an as-built thickness of 0.25 inches. The minimum thickness reading exceeds the API 653 minimum requirement of 0.09 inches by 100 square inches, and is therefore acceptable. A visual inspection was conducted on the underside of the roof plating from a moveable scaffold. The bottom of the roof plating appears to be unpainted and is covered by a thin coating of rust throughout. The roof plating is not welded to the supporting rafters.

4.2 Roof top Appurtenances

Several different types of appurtenances are attached to the tank roof. Each component was visually inspected for soundness of welds and signs of corrosion. The results of this investigation on the following components are as follows.

4.2.1 Goose Neck Vents

There are eight gooseneck vents located around the perimeter of the tank. These vents prevent rain from entering while ensuring adequate airflow through the zone above the product level and the tank roof. These vents are in good condition with corrosion evident on the nozzle neck and underside of the flange. In addition, most of the bolts attaching the vents have significant corrosion. The north side vent as some minor weld corrosion on the reinforcement plate.

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There are four access openings in the roof of the tank. These openings are approximately 42 inches in diameter and have approximately 35 – ¾” bolts attaching a blind flange. The condition of these access openings is poor with corrosion evident at mating surfaces of flange and cover. In addition, all of the bolts attaching the access openings have significant corrosion, as well as two of the access port rims.

4.2.3 Sampling Port

There is one six-inch diameter sampling port near the stairway landing. This access port is for sampling and manual level sensing. The access port is in good condition. 4.2.4 Painter’s Hitch The painter’s hitch in center of roof has severe corrosion with total metal loss. This will require replacement. This hitch mounts to a 6 inch pipe with end cap and 10 inch reinforcement.

4.3 Roof Support Framing

The roof plating is supported by roof rafters radiating from the roof center. See Figure 2.0 for the roof-framing plan. The rafters are supported by roof beams, which are in turn supported by standard API columns. Each column terminates at a steel member foundation at the tank bottom. The column support foundation is not welded to the bottom plate. Plate clips welded to the tank bottom prevent lateral movement of the column foundation. A moveable scaffold was erected inside the tank and used to inspect the roof plating and framing. The scaffold was positioned at the center column and then subsequently moved to an inner column, outer column and then located at the tank shell adjacent to a roof vent opening.

The rafters and beams are in good condition with no indications of deterioration or loss of metal. The rafters and beams have a light coating of rust and there is no evidence that they were ever painted. The bolted connection of the roof beam to the column top is slightly rusted but intact with all nuts visible and in good condition.

The rafters are held in position with L2x2x3/16 angles welded to each rafter at midspan. The fillet weld on several of these spacers failed causing the angle to fall to the tank floor. It appears that these angles were used to maintain the spacing between the rafters during initial installation of the roof plating. There are 11 loose rafters that require spacer replacement and re-welding.

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The roof support columns, consisting of channels welded together, are in good condition with no evidence of corrosion or horizontal deflection. The supporting channel foundation at each column location is also in good condition. These columns are bare and beginning to rust from environmental exposure since the tank cleaning has occurred.

5.0 TANK IN-PLANE LEVEL SURVEY

A survey was conducted to analyze the type of settlement that has occurred. No prior survey has been conducted to establish a rate or progression of settlement occurring. This information is however able to detect the magnitude of the existing out of plane alignment. The survey, Appendix C, was conducted in accordance with API 653 “Evaluation of Tank Bottom Settlement”. On June 22, 2006, Prudencio R. Balagtas & Associates performed a level survey around the exterior perimeter of the tank. Three temporary benchmarks were created and twenty elevations were read at equal intervals around the tank. The outer “shell” created by the shell-to-bottom connection was used for the survey. The datum used for the survey elevations is GGTN U.S.O. (GGN 2068) with elevation = 15.56’ Mean Sea Level (MSL). The results of this survey are included in Appendix C. The results indicate that there has been little to no differential settlement of the tank bottom. The average difference in elevations between the 31 feet intervals around the tank is 0.020 feet or 0.24 inches with a maximum difference of 0.048 feet or 0.58 inches. The average settlement corresponds to a slope of 0.065% slope between points. The magnitude of settlement is insignificant and no further analysis has been performed.

6.0 CATHODIC PROTECTION EVALUATION

A new cathodic protection system was installed for both Tank 1934 and 1935 by the Tank 1935 contractor.

7.0 LEAK DETECTION EVALUATION

A new leak detection system is currently under construction for both Tank 1934 and 1935 by the Tank 1935 contractor.

8.0 RECOMMENDATIONS

The following are recommended repairs and improvements for Tank 1934 as a result of the inspection and evaluations noted above. The primary goal is to achieve a sound level of operation to allow continued service until the next scheduled inspection. The quantities of tank repairs are dependant on the scope of the repairs selected. The estimated quantities for each recommended repair and improvement are included in Table 5.

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8.1 Tank Bottom The defective welds found in the tank bottom, should be repaired by air-arc gouging of the weld and re-welding the fillet weld for both the bottom plate lap joint welds and the interior bottom-to-shell connection weld. There are approximately 72 LF where these repairs are required. The deepest pits should be filled with weld and made flush with the top of the plate. Approximately 99 deep pits were found to require filling. More pits may become evident after sand blasting of the tank floor is completed. Six doubler plates are required and should be fully welded to the tank bottom plates. Once the repairs have been completed, a new coating system should be applied to the tank bottom.

8.2 Tank Shell The coating of the tank shell exterior is of sufficient thickness to protect the metal where the coating has not been compromised due to the presence of small areas of corrosion; however, GPA will require sandblasting and recoating of the entire exterior. The wind girders on the shell have flaking paint on the underside and will need to be recoated. Shell repairs are needed where the welds have failed between the shell and wind girder. There are 10 separate areas requiring repair: 5 at the top wind girder elevation and 5 at lower wind girder elevation. These areas have heavy metal loss and may be repaired with lap-welded patch plates per API 653 Para 9.3. It is not anticipated that the shell exterior will require additional coating. A new coating system should be applied to the entire tank shell interior and the entire length of the roof support columns. The existing scale should be removed and the entire surface cleaned to bare metal prior to application of the new coating system. The plate edge along the foundation seal shall be exposed, sand blasted, evaluated for metal loss, recoated and a proper seal put back in place. Include removal of any standing water or vegetation at the plate edge. 8.3 Tank Roof The coating of the topside roof plating is inadequate and a new coating system is required for the entire roof. The entire surface should be cleaned to bare metal prior to recoating. The 19 welds, at the tank roof perimeter, approximately three inches long each will need to be ground or abrasive blasted to base metal and re-welded. There are also approximately 10 feet of plate welds on the roof that require cleaned and re-welded. The eleven loose roof rafters require spacing replacement and re-welding. The roof underside does not require a new coating system.

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8.4 Appurtenances 8.4.1 Tank Roof The access openings, gooseneck vents and reinforcement plates exhibit some light surface rust and will need to be sand blasted to bare metal and then recoated. The four access opening covers should be replaced and the mating surface corrosion removed, re-coated, and all bolts replaced. Two of the access port rims also require replacement. The painter’s hitch in center of roof requires replacement. This hitch amounts to a 6 inch pipe with end cap and 10 inch reinforcement. 8.4.2 Tank Shell

The large bolted access opening on the tank shell has been removed. The door should be reinstalled with gasket for sealing the area and the bolts retightened. The bolts should be vacuum tested to ensure 100% seal. The minor corrosion present on the manholes, pipe nozzles and stairway shall be sand blasted and recoated. The liquid level sensor has two support brackets that require total replacement and five that have minor corrosion, in need of repair. The Varco Level Gauge shall be replaced, along with the pipe supports and accessories.

The bottom portion of the exterior overflow vents requires replacement in some areas. The overflow vent that is dislodged inside the tank needs to be repaired and re-welded. The repair will include installation of a 48 inch x 12 inch x ¼ support bracket and weld in a 12 inch Sch. 80 elbow. 8.5 Cathodic Protection System A new cathodic protection system was installed for both Tank 1934 and 1935 by the Tank 1935 contractor. 8.6 Leak Detection System A new leak detection system is currently under construction for both Tank 1934 and 1935 by the Tank 1935 contractor. 8.7 Tank Inspection Program It is recommended that the Guam Power Authority establish a Tank Inspection Program. Inspections should be performed every ten years unless subsequent inspection information can be used to justify a longer period. This tank should be drained, cleaned and inspected in ten years to re-evaluate the condition of the tank interior. At this

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inspection time, rates of corrosion can be determined, remaining life of the tank bottom can be reassessed and the structural integrity can be recorded. A regular external inspection regiment should be established to aid in the inspection scope and intervals. This should be comprised of two types of inspections: routine in service inspections and external inspections. Owner/operator personnel knowledgeable of the storage facility operations, the tank and the characteristics of the product stored should perform routine in-service inspections at least every month. The external inspections should be performed every five years by and authorized inspector. The scope of the external inspections should be established using API 653 as a guide. All existing tank information, including external and internal inspection reports and tank service records, should be maintained in one location or Tank 1934 File. This File will contain all information known concerning the operation and maintenance of this tank and will provide future inspectors the background information to accurately access the integrity of the tank.

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GPA Tank 1934

Table 1 - Ultrasound Thickness Measurements – Floor Floor Plates 1-84

Reading #: (inch) Reading #: (inch) Plate # 1 2 3 4

Average thickness

Plate # 1 2 3 4

Average thickness

1 .268 .282 .270 .273 43 .295 .269 .271 .290 .281 2 .271 .274 .240 .260 .261 44 .257 .249 .285 .250 .260 3

3A .288 .273

.292

.284 .303 .261

.273

.281 .287 .274

45 .264 .240 .259 .260 .255

4 .274 .290 .283 .281 .282 46 .265 .274 .281 .286 .276 5 .274 .269 .285 .269 .274 47 .282 .260 .269 .284 .273 6 .240 .284 .240 .260 .256 48 .284 .290 .272 .279 .281 7 .267 .256 .271 .266 .265 49 .286 .283 .262 .276 .276 8 .264 .273 .267 .248 .263 50 .289 .277 .299 .273 .284 9 .269 .260 .272 .259 .265 51 .299 .302 .288 .303 .298

10 .240 .261 .240 .247 52 .282 .261 .281 .290 .278 11 .265 .271 .289 .285 .277 53 .286 .269 .276 .282 .278 12 .283 .281 .271 .260 .273 54 .287 .274 .271 .260 .273 13 .292 .274 .288 .290 .286 55 .254 .249 .275 .240 .254 14 .277 .273 .268 .269 .271 56 .272 .266 .271 .286 .273 15 .287 .284 .240 .271 .270 57 .274 .269 .285 .274 .275 16 .277 .283 .269 .276 58 .275 .240 .277 .273 .266 17 .285 .283 .268 .272 .268 59 .265 .258 .267 .260 .262 18 .268 .280 .267 .260 .268 60 .305 .274 .269 .284 .283 19 .242 .286 .281 .285 .277 61 .298 .270 .272 .290 .282 20 .268 .274 .271 .272 .271 62 .256 .286 .266 .274 .270 21 .264 .260 .269 .264 63 .308 .290 .273 .293 .291 22 .280 .269 .277 .273 .274 64 .309 .260 .286 .307 .290 23 .265 .274 .290 .281 .277 65 .296 .304 .280 .299 .294 24 .245 .255 .278 .268 .261 66 .298 .272 .261 .270 .275 25 .238 .273 .240 .259 .252 67 .285 .260 .253 .284 .270 26 .253 .266 .282 .248 .262 68 .289 .299 .281 .283 .288 27 .249 .261 .240 .269 .254 69 .301 .276 .277 .264 .279 28 .279 .274 .264 .286 .275 70 .298 .283 .282 .275 .284 29 .289 .284 .280 .272 .281 71 .299 .274 .283 .287 .285 30 .298 .283 .275 .260 .279 72 .297 .279 .303 .280 .289 31 .290 .287 .303 .285 .291 73 .243 .248 .244 .240 .243 32 .285 .276 .290 .299 .287 74 .272 .240 .273 .260 .261 33 .259 .273 .284 .279 .273 75 .296 .299 .285 .276 .289 34 .301 .281 .307 .286 .293 76 .287 .266 .269 .276 .274 35 .298 .280 .277 .269 .281 77 .298 .274 .290 .284 .286 36 .291 .300 .264 .283 .284 78 .281 .269 .281 .271 .275 37 .299 .274 .302 .278 .288 79 .275 .280 .272 .283 .277 38 .285 .270 .266 .287 .277 80 .294 .303 .287 .275 .289 39 .232 .240 .255 .268 .248 81 .246 .249 .273 .240 .252 40 .227 .284 .238 .279 .257 82 .258 .261 .270 .267 .264 41 .275 .241 .264 .261 .260 83 .254 .276 .281 .248 .264 42 .239 .244 .267 .277 .256 84 .239 .266 .264 .258 .256

GPA Tank 1934

Table 1 continued - Ultrasound Thickness Measurements – Floor Floor Plates 85-168


Average thickness

Plate # 1 2 3 4

Average thickness

85 .280 .269 .282 .270 .275 127 .283 .281 .271 .260 .273 86 .295 .269 .271 .290 .281 128 .288 .277 .283 .269 .279 87 .274 .269 .285 .274 .276 129 .292 .274 .288 .290 .263 88 .287 .274 .271 .260 .273 130 .271 .274 .240 .260 .261 89 .286 .269 .276 .282 .278 131 .282 .260 .269 .284 .273 90 .240 .261 .272 .240 .253 132 .267 .256 .271 .266 .265 91 .299 .302 .288 .303 .298 133 .272 .277 .299 .273 .280 92 .264 .273 .267 .248 .263 134 .268 .285 .279 .253 .271 93 .269 .260 .272 .259 .265 135 .286 .283 .262 .276 .276 94 .284 .290 .272 .279 .281 136 .282 .261 .281 .290 .278 95 .265 .271 .289 .285 .270 137 .240 .284 .240 .260 .256 96 .274 .269 .285 .269 .274 138 .265 .274 .281 .286 .276 97 .254 .249 .275 .240 .254 139 .274 .290 .283 .281 .282 98 .275 .240 .277 .273 .266 140 .272 .266 .271 .286 .273 99 .287 .284 .240 .271 .270 141 .277 .273 .268 .269 .271

100 .264 .240 .259 .260 .255 142 .257 .249 .275 .250 .257 101 .291 .300 .264 .283 .284 143 .281 .269 .281 .271 .275 102 .298 .280 .277 .269 .281 144 .287 .266 .269 .276 .274 103 .301 .281 .307 .286 .293 145 .296 .299 .255 .276 .281 104 .308 .290 .273 .293 .291 146 .256 .286 .266 .274 .270 105 .274 .276 .260 .269 .269 147 .298 .283 .275 .260 .279 106 .296 .304 .280 .299 .294 148 .309 .260 .286 .307 .290 107 .301 .276 .277 .264 .279 149 .289 .284 .270 .272 .278 108 .253 .266 .282 .248 .262 150 .282 .260 .273 .284 .274 109 .248 .273 .240 .259 .255 151 .277 .281 .289 .268 .278 110 .298 .272 .261 .270 .275 152 .289 .299 .281 .283 .288 111 .249 .261 .240 .269 .254 153 .245 .245 .268 .268 .256 112 .279 .274 .264 .286 .275 154 .265 .274 .290 .281 .277 113 .298 .283 .282 .275 .284 155 .299 .274 .283 .287 .285 114 .287 .279 .303 .280 .287 156 .280 .279 .277 .273 .277 115 .290 .287 .303 .285 .291 157 .243 .248 .244 .240 .243 116 .268 .274 .271 .272 .271 158 .272 .240 .273 .260 .261 117 .259 .273 .284 .279 .273 159 .285 .276 .290 .299 .287 118 .288 .270 .272 .290 .280 160 .242 .286 .281 .285 .273 119 .305 .274 .269 .284 .283 161 .298 .274 .290 .284 .286 120 .265 .258 .267 .260 .262 162 .268 .270 .267 .260 .266 121 .299 .274 .302 .278 .288 163 .275 .280 .272 .283 .277 122 .275 .270 .266 .287 .274 164 .294 .303 .287 .275 .289 123 .232 .240 .255 .268 .248 165 .246 .249 .273 .240 .252 124 .227 .284 .238 .279 .257 166 .258 .261 .270 .267 .264 125 .265 .241 .264 .261 .257 167 .254 .276 .281 .248 .264 126 .239 .244 .267 .277 .256 168 .239 .266 .264 .258 .256

GPA Tank 1934

Table 1 continued - Ultrasound Thickness Measurements – Floor Floor Plates 169-198


Average thickness

Plate # 1 2 3 4

Average thickness

169 .240 .261 .272 .240 .253 185 .272 .277 .299 .273 .280 170 .295 .269 .271 .290 .281 186 .277 .273 .268 .269 .271 172 .287 .284 .240 .271 .270 187 .275 .240 .277 .273 .266 173 .274 .290 .283 .281 .282 188 .274 .269 .285 .269 .274 174 .240 .284 .240 .260 .256 189 .284 .290 .272 .279 .281 175 .286 .283 .262 .276 .276 190 .283 .281 .271 .260 .273 176 .280 .269 .282 .270 .275 191 .249 .268 .274 .255 .261 177 .264 .273 .267 .248 .263 191A .268 .285 .279 .253 .271 178 .269 .260 .272 .259 .265 192 .267 .256 .271 .266 .265 179 .288 .277 .283 .269 .279 193 .282 .261 .281 .290 .278 180 .265 .271 .289 .285 .270 194 .282 .260 .269 .284 .273 181 .286 .269 .276 .282 .278 195 .265 .274 .281 .286 .276 182 .254 .249 .275 .240 .254 196 .271 .274 .240 .260 .261 183 .272 .266 .271 .286 .273 197 .292 .274 .288 .290 .263 184 .287 .274 .271 .260 .273 198 .274 .269 .285 .274 .276

GPA Tank 1934

Table 3 - Ultrasound Thickness Measurements – Shell Shell Course 1 - 6

Course # Plate # Plate Thickness (inch)


1 1 1.130 3 1 .710 1 2 1.141 3 2 .751 1 3 1.120 3 3 .764 1 4 1.135 3 4 .761 1 5 1.139 3 5 .770 1 6 1.140 3 6 .765 1 7 1.142 3 7 .769 1 8 1.135 3 8 .773 1 9 1.132 3 9 .742 1 10 1.141 3 10 .754 1 11 1.149 3 11 .765 1 12 1.145 3 12 .752 1 13 1.139 3 13 .749 1 14 1.150 3 14 .741 1 15 1.131 3 15 .737 1 16 1.136 3 16 .748 1 17 1.137 3 17 .759 1 18 1.144 3 18 .764 1 19 1.134 3 19 .782 1 20 1.140 3 20 .768 1 21 1.149 3 21 .756 2 1 .912 4 1 .560 2 2 .863 4 2 .553 2 3 .920 4 3 .566 2 4 .890 4 4 .564 2 5 .865 4 5 .570 2 6 .853 4 6 .552 2 7 .846 4 7 .559 2 8 .857 4 8 .561 2 9 .871 4 9 .549 2 10 .879 4 10 .564 2 11 .862 4 11 .569 2 12 .860 4 12 .538 2 13 .858 4 13 .545 2 14 .869 4 14 .549 2 15 .876 4 15 .557 2 16 .866 4 16 .562 2 17 .852 4 17 .560 2 18 .844 4 18 .548 2 19 .862 4 19 .541 2 20 .874 4 20 .533 2 21 .859 4 21 .554

GPA Tank 1934

Table 3 continued - Ultrasound Thickness Measurements – Shell

Shell Course 1 – 6 Cont



5 1 .370 6 1 .390 5 2 .354 6 2 .318 5 3 .399 6 3 .284 5 4 .349 6 4 .302 5 5 .370 6 5 .311 5 6 .339 6 6 .292 5 7 .348 6 7 .290 5 8 .358 6 8 .321 5 9 .361 6 9 .310 5 10 .342 6 10 .294 5 11 .372 6 11 .299 5 12 .350 6 12 .291 5 13 .349 6 13 .305 5 14 .367 6 14 .307 5 15 .376 6 15 .315 5 16 .371 6 16 .295 5 17 .362 6 17 .312 5 18 .359 6 18 .307 5 19 .360 6 19 .293 5 20 .352 6 20 .298 5 21 .343 6 21 .301

Ultrasound Min., Max., Average Thickness Measurements Shell Course 1 – 6

Course # Nominal

Thickness (in.) Minimum

Thickness (in.) Maximum

Thickness (in.) Average

Thickness (in.) 1 1.125 1.120 1.150 1.138 2 0.875 .844 .920 .868 3 0.750 .710 .782 .756 4 0.562 .533 .569 .555 5 0.375 .339 .399 .359 6 0.312 .284 .390 .306

GPA Tank 1934

Table 4 - Ultrasound Thickness Measurements – Roof

UT thickness readings were taken at 10 ft and 50 ft radius on each plate, and 1 ft from perimeter. 10 foot radius – 6 each readings

Plate # 115 116 125 138 137 126 UT Readings .249 .254 .264 .253 .255 .252

50 foot radius – 30 each readings

Plate # 51 60 74 80 95 101 118 123 140 70 UT Readings .253 .262 .261 .265 .259 .262 .264 .260 .245 .251 Plate # 145 160 167 182 189 201 200 191 178 62 UT Readings .235 .253 .263 .232 .264 .256 .257 .261 .254 .241 Plate # 171 156 150 135 128 113 106 91 84 52 UT Readings .263 .238 .255 .261 .261 .249 .268 .262 .265 .259

99 foot radius – 28 each readings

Plate # 14 12 7 2 21 47 76 98 142 163 UT Readings .237 .254 .256 .225 .253 .259 .244 .263 .260 .249 Plate # 185 205 222 238 241 244 247 231 215 196 UT Readings .252 .258 .240 .255 .253 .248 .256 .261 .259 .258 Plate # 175 153 152 131 88 67 66 46 UT Readings .246 .258 .253 .248 .255 .248 .236 .238


APPENDIX A

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APPENDIX B

17

GPA Tank 1934

Shell Course Heights and Thickness Calculations GPA Tank 1934

The minimum acceptable shell plate thickness for tanks with a diameter equal to or less than two hundred feet (200') is calculated as follows, per API 653, Para 4.3.3.1.

t min = 2.6 (H-1) DG SE where: S = Allowable Stress (psi) D = Nominal Diameter of tank G = 1.000 Highest Specific Gravity of Contents* H = product Height (Ft) E = Joint Efficiency

Course

Course Hgt. (ft.) Product Hgt. (ft.) Allowable Stress (psi)

Joint Efficiency API 653 Table 4-2

Actual Average Thickness (in.)**

Required Thickness Min. (in.)

Meets or Exceeds

1 8.1 46.5 23,595 1.00 1.139 1.00 Yes

2 8.1 38.4 23,595 1.00 .868 .824 Yes

3 8.1 30.3 25,960 1.00 .756 .586 Yes

4 8.1 21.5 25,960 1.00 .555 .410 Yes

5 8.1 13.4 25,960 1.00 .359 .248 Yes

6 8.1 5.3 25,960 1.00 .306 .100*** Yes

* Specific gravity - the highest calculated product specific gravity the tank can hold at full shell height. ** Actual thickness taken from average UT shell readings per course (see Para. 6.1) *** Minimum allowable thickness for any tank course API 653 4.3.3.1.

Calculations for minimum thickness of bottom shell course

t min = 2.6 (H-1) DG SE where: S = (0.429 x 55,000) = 23,595) lbf/in² D = 200 ft G = 1.000 Highest Specific Gravity of Contents* H = 46.5 ft E = Joint Efficiency (1.00 – API 6th Edition Appendix D)

t min = 2.6 (46.5-1) x 200 x 1.0 = 1.00 inch 23,595 x 1.0


APPENDIX C

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APPENDIX D

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July - August 2006 API 653 Out-of-Service Inspection Report Report No. GPA06-3 Tank: Cabras 1934 Cabras Piti, Guam Guam Power Authority, Guam

Tank # 1934 Photos Photo #1: North Tank # 1934 Photo #2: East Tank # 1934 Photo # 3: South Tank # 1934 Photo # 4: West Tank # 1934


Photo #5: Removing access door Photo #6: Windgirder typical corrosion

Photo # 7: Shell corrosion under side of windgirder Photo # 8: Underside windgirder corrosion


Photo # 9: Windgirder - typical Photo # 10: Varec Gauge bracket corrosion Photo # 11: Windgirder weld corrosion w/metal loss Photo # 12: Windgirder/Shell Corrosion


Photo # 13: Broken overflow at 46 ft elevation Photo # 14: Underside of roof plate-light surface rust Photo # 15: Top of intermediate support column-typical Photo # 16: Overflow funnel and pipe


Photo # 17: Underside of Varec Gauge nozzles Photo # 18: Underside of sample hatch Photo # 19: Typical intermediate column support Photo # 20: Center ring top center column support


Photo # 21: Typical roof plate corrosion Photo # 22: Roof plate # 176 general corrossion Photo # 23: Roof coating failure Photo # 24: Roof manway flange and bolt corrosion


Photo # 25:Plate #14 weld corrosion at roof edge Photo # 26: Roof plate #1 weld corrosion Photo # 27: Roof plate #75 corrosion w/hole Photo # 28: Roof vent bolt corrosion


Photo # 29: Roof vent flange corrosion Photo # 30: Roof painter’s hitch corrosion Photo # 31: Roof vent bracket corrosion Photo # 32: Standing water and vegetation at projection edge


Photo # 33: 24 in. inlet Photo # 34: Bottom stairway Photo # 35: Typical of 4 earthing strap Photo # 36: Overflow piping


Photo # 37: Overflow piping and brackets Photo # 38: 30 in manway Photo # 39: Corroded overflow pipe end – Sta 164’ Photo # 40: Overflow pipe blank


Photo # 41: Vacuum box testing of floor plates Photo # 42: Internal shell metal loss from isolated pitting Photo # 43: 60 in sump-typical of 4 Photo # 44: Varec gauge float with loose weight


Photo # 45: Weld corrosion at plate # 142/143 Photo # 46: Lap weld defects Photo # 47: Floor-to-shell weld, typical Photo # 48: Varec gauge and lower previous bracket


Photo # 49: Inspection of shell and windgirders Photo # 50: Oil residue on floor after cleaning


APPENDIX E

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GUAM POWER AUTHORITY

PITI TANK FARM TANK 1935 INSPECTION REPORT

Tank System Integrity Testing Report

April 2004


TABLE OF CONTENTS

ES EXECUTIVE SUMMARY 1

1.0 INTRODUCTION 2

1.1 Background 1.2 Site Description 1.3 Inspection Description

2.0 TANK BOTTOM INSPECTION 4 2.1 Bottom Plating

2.1.1 Bottom Plate Fillet Weld 2.1.2 Shell-to-Bottom Plate Fillet Weld

3.0 TANK SHELL INSPECTION 6 3.1 Tank Shell 3.2 Tank Shell Appurtenances

3.2.1 Manholes 3.2.2 Access Openings 3.2.3 Overflow Vents 3.2.4 Pipe Nozzles 3.2.5 Stairway 3.2.6 Liquid Level Sensor 3.2.7 Wind Girders

4.0 TANK ROOF INSPECTION 8 4.1 Roof Plating

4.2 Roof Top Appurtenances 4.2.1 Gooseneck Vents 4.2.2 Access Openings 4.2.3 Sampling Port

4.3 Roof Support Framing

5.0 TANK IN-PLANE LEVEL SURVEY 10

6.0 CATHODIC PROTECTION EVALUATION 11

7.0 LEAK DETECTION EVALUATION 11

8.0 RECOMMENDATIONS 11 8.1 Tank Bottom 8.2 Tank Shell 8.3 Tank Roof

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8.4 Appurtenances 8.4.1 Tank Roof 8.4.2 Tank Shell

8.5 Cathodic Protection System 8.6 Leak Detection System 8.6.1 Intermittent Monitoring with Portable Sensor 8.6.2 Continuous Monitoring with Permanent Sensors

8.7 Tank Inspection Program

Tables

1.0 Ultrasonic Thickness Measurements 2.0 Corrosion Pit Depths 3.0 Cost Estimate

Figures

1.0 Roof Plate Layout 2.0 Roof Framing Layout 3.0 Bottom Plate Plan 4.0 Shell Plate Layout 5.0 Column Foundations 6.0 Tank Shell Thickness 7.0 Tank Roof Thickness

Appendices

Appendix A – Administrative Order – Scope of Work Appendix B – Minimum Thickness Calculation Appendix C – Tank Level Survey Results Appendix D – Tank Inspection Pictures

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ES EXECUTIVE SUMMARY

Tank 1935 is in fair condition and with the implementation of the recommended repairs can be suitable for service without the requirement for major reconstruction. Based on the tank inspection, the following are the recommendations for the repair of the tank.

Tank Bottom Plating: Some of the tank bottom plates are heavily pitted. The deeper pits will require repair in the form of welding. Where pitting is extensive doubler plates of various sizes are required. Leaks were found in some of the fillet welds connecting the bottom plates as well as the shell-to-bottom plate fillet weld. These welds will require repair. The tank bottom plate thickness readings indicate the bottom plates are acceptable for continued use. Tank Shell: The tank shell is in good condition with no major corrosion cells or loss in plate thickness. The coating on the interior side of the tank has deteriorated to the extent that it provides little protection for the shell. The coating on the exterior side is in good condition and requires only touchup painting in small areas where corrosion is present.

Tank Roof: The tank roof plating is in good condition with adequate plate thickness. Paint blisters on the exterior side of the plating are present to a small degree and will require repair as well as a small number of fillet welds that are defective. The underside of the roof plating is rusted and apparently was never painted. A new coating system is recommended for the underside of the roof deck plating.

The tank channel roof rafters are in good condition as well as the supporting wide flange beams with no visible deterioration or deflection. The only remedial repair work required is replacement of the single roof rafter that became disconnected and fell to the tank floor below. A light coating of rust covers the roof rafters and supporting beams. A new coating system would be appropriate for these items. The steel channel columns supporting the roof beams as well the foundation at the base of each column are in good condition. Remedial work on the roof support columns is not required. Leak Detection System: A leak detection system should be installed to monitor the integrity of the tank bottom between interior tank inspections. This system can be either intermittent or continuous monitoring devices that are either portable or permanently installed. Cathodic Protection System: A new cathodic protection system should be installed in order to adequately protect both tanks and the associated piping in the Piti Tank Farm.


1.0 INTRODUCTION

1.1 Background Guam Power Authority (GPA) owns two bulk fuel storage tanks, 1935 and 1934, located in Piti Tank Farm in the Municipality of Piti between the Atlantis Submarine pier and the former Navy Power unit on the Piti Channel. These tanks are used to supply fuel to the Cabras and the Tanguisson Power Plant located adjacent to the tank farm. GPA has contracted the operation of the two-tank facility to Peterra Inc. The tanks and associated infrastructure was completed in 1976 by the United States Military and resides on compacted coral limestone fill with no previous history of hydrocarbon contamination. The operations at the site include the storage of fuel oil, transfer of fuel oil into and out of the facility, and the processing of oily water. The tanks have been in service continually since construction was completed except for a period of time while the facility was transferred from military to civilian control. The type of fuel stored in these two tanks is Fuel Oil #6, or Bunker Fuel C. Fuel Oil #6 is a mixture of petroleum distillate hydrocarbons and has a boiling point greater than 400 degrees Fahrenheit. This fuel is commonly broken into two categories depending on the relative levels of sulfur contained in the fuel. High sulfur fuel, also known as sour fuel, is more corrosive and often has increased sulfur levels in stack emissions. The second type fuel is low sulfur fuel also known as sweet fuel. Both of these fuels are used at the Power Plants. Previously both of these fuels were mixed between the two fuel storage tanks on site. This practice was stopped some years before and Tank 1935 is now used to store the high sulfur fuel. These tanks have not been drained and inspected prior to this report so a base line of corrosion cannot be established. In addition, no construction records or record drawings for the tanks could be located.

In February 2001 the United States Environmental Protection Agency (USEPA) Region IX issued a Unilateral Administrative Order For Piti Tank Farm to GPA to “perform abatement activities necessary to address conditions that may present an imminent and substantial endangerment”. These abatement activities “require integrity inspections, maintenance, installation of leak detection and repair of cathodic protection.” Due to continued operations at the Power Plants, one tank is to be inspected at a time. PSC Industrial Services Group is the contactor that has been retained by GPA to drain and clean the tank. Winzler & Kelly Consulting Engineers has been retained to perform the tank inspection. This report is the result of the integrity testing and inspection of Tank 1935 in accordance with the Scope of Work issued in Appendix A of the Administrative Order. This Scope of Work is included within this report in Appendix A.

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1.2 Site Description The two bulk storage tanks at the Piti Tank Farm, each have a capacity of approximately 254,000 barrels each. They are supplied by a 24” above ground pipeline that is interconnected to the U.S. Navy and Shell Tank farms. The supply line terminates with a double gate valve at Tank 1935 and a single gate valve at Tank 1934. Discharge from the tanks is through a 12” pipeline with a gate valve at the tank discharge port. This piping is connected to a pump manifold that distributes fuel to GPA Cabras and Tanguisson Power Plants. The oil-water separator (OWS) consists of a partially buried cast-in-place concrete tank with three interior sections. The wood and tin cover was placed over the tanks to keep out rain and other objects, but this was removed by the cleaning Contractor. The system is connected to each bulk storage tank with a 3” or 4” discharge line. The OWS is also connected to the 12” tank discharge piping; the interconnection includes an in-line filter. This system is not functioning and the electrical controllers are missing and in-line pumps and/or motors have been removed. Three above ground truck trailer tanks are nearby and connected to the OWS but stand empty. There is also a collection sump on the berm by the entry road for truck discharge of waste oil to the OWS. 1.3 Inspection Description

Tank 1935 was drained of fuel and cleaned in accordance with the “Tank Cleanout Work Plan” dated September 2003 and developed for the sludge removing and cleaning of both Tank 1934 and Tank 1935 by PSC Industrial Group. The contractor remained on site to assist in the inspection by providing compressed air, scaffolding in the interior of the tank and general support tasks. The tank inspection was conducted in accordance with the “Work Plan For Life Extension and Refurbishment of the GPA Bulk Storage Tanks 1934 & 1935 for the Piti Fuel Tank Farm, Guam” dated April 2003. Winzler & Kelly personnel conducted the structural evaluations, tank bottom leak evaluations and tank inspections in accordance with American Petroleum Institute (API) reference standard 653. CONCECO/MATCOR personnel conducted the ultrasonic thickness measurements, coating thickness, pit depth readings, cathodic protection evaluation and leak detection evaluation. Prudencio R. Balagtas & Associates performed the tank level survey. All tank inspections and evaluations were conducted in accordance with API Standard 653 “Tank Inspection, Repair, Alteration, and Reconstruction”. The results of this inspection are presented in this report.

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2.0 TANK BOTTOM INSPECTION

2.1 Tank Bottom Plating The tank bottom plating was found to be in fair condition. There was evidence of pitting on the floor plates and a visual inspection found that no through pitting had occurred. There was no remaining evidence of a coating system on the floor and a scale of corrosion product had formed over the plates. This scale was removed by power grinding at the locations used for ultrasonic thickness and pit depth measurements. In one location a roof rafter had become dislodged by an unknown event and fell to the floor. The impact of this rafter produced an indentation on plate number 94 but did not appear to puncture the plate. There are four water sumps located on the tank floor. These sumps are to collect water and then discharge it through the nozzles located on the shell. These sumps are 58 inches in diameter and about three feet deep. A six-inch pipe rises out of the sumps and connects to the discharge nozzle. These sumps were visually inspected and appear solid and the welds appear sound. In some areas the bottom plating does not slope uniformly to the sumps resulting in small amounts of water ponding on the tank bottom. A large number of plates were not bearing on compacted fill below the tank, and exhibited a springing characteristic when walked upon. These areas were discovered by feeling the movements of the plate when walked upon. When the tank is operational and full of fuel this condition should be eliminated.

The ultrasonic thickness measurements were obtained using a Panametrics Model 26DL PLUS ultrasonic thickness meter. These instruments utilize a "pulse-echo to echo" circuit wherein a short duration electrical pulse excites a piezoelectric transducer. This meter is capable of reading steel plate thickness without removal of coatings. The transducer emits ultra high frequency sound waves that are transmitted to the test material through a couplant such as glycerin, water, or oil that is placed between the test material surface and the transducer. Sound waves pass through the test material and reflect back through the material from the opposite face. The transducer receiver converts the sound wave to electrical pulses. The time (t) for sound travel is the total time between pulse and echo minus the transducer delay time.

The material thickness (y) is determined by the following equation:

y = Vt/2

where V is the velocity of sound through the material. The velocity of sound through low carbon steel is generally consistent and can be verified and programmed into the gauges using specially manufactured, steel calibration blocks traceable to NBS standards.

4


Approximately 800 readings were taken and the results are uniform over the tank bottom. The general thickness of the plates is 0.3125” or 5/16”. No thickness readings were below the API 653 minimum allowable 0.1” thickness requirements. See Table 1 for a listing of the plate bottom thickness readings. The pit depths were taken on the on the floor plates using a pit depth gauge. A pit depth gauge is a mechanical gauge that measures the difference between the bottom of a pit and the surrounding plate. Pitting varies over the bottom of the tank and on some plates, large numbers of pits have been observed. Two pit readings were taken for each of the large plates and one on the smaller plates. Only three measured pits were deeper than 0.200 inches with the deepest at a depth of 0.216 inches. The results of these measurements are in Table 2. 2.1.1 Bottom Plate Fillet Weld A visual inspection was conducted on all of the bottom plate lap joint fillet welds, the sump welds to the bottom plating, and the interior and exterior perimeter shell-to-bottom welds. There was no evidence of corrosion or cracks in the welds. The welds appeared to be intact and solid. In addition to the visual inspection of the lap joint fillet welds, a vacuum box was used to test all the plate lap welds. The rectangular vacuum box is approximately 4 inches high by 8 inches wide by 2.5 feet long. The top of the vacuum box contains a Plexiglas window for observing the length of the weld being tested. The bottom of the vacuum box is open with a one-inch rubber gasket around its perimeter. The weld to be investigated is coated with a liquid containing soap and the vacuum box is then centered on this length of weld and held firmly in place. Compressed air is then used to create a vacuum. A negative pressure of at least 15 psi was held for approximately 15 seconds over each section of weld. The weld was viewed through the glass window for the formation of an air bubble that would indicate a hole in the weld. All of the plate lap joint fillet welds were carefully tested with the vacuum box. The only welds on the bottom plate that could not be tested were those in the vicinity of some column supports and at the sumps. These areas were inspected visually. Thirteen (13) leaks were detected on the bottom plate lap joint fillet welds. These leak locations are shown on Figure 3.0 “Bottom Plate Layout”.

2.1.2 Shell-to-Bottom Plate Fillet Weld The interior shell-to-bottom plate fillet weld was tested for the full tank circumference with a corner vacuum box. The testing procedure used is the same as that on the bottom

5


plate lap joint fillet welds. Nine (9) leaks were detected on the shell-to-bottom plate fillet weld. The location of the leaks is shown on Figure 3.0 “Bottom Plate Layout”.

3.0 TANK SHELL INSPECTION

3.1 Tank Shell The tank shell is in good condition. There is no evidence of buckling or deformation of the shell. The exterior surface of the shell has surface rust in some areas, as did the wind girder, stairwell and level gauge. This rust did not appear to be significant or have caused pitting. The thickness of the coating was measured with a thin film thickness gauge to determine the suitability of the existing paint or coating. The results are included in Table 1. The thickness of each shell plate was measured by an ultrasonic thickness gauge. The first three courses were measured from the ground and the top course was measured from the roof. Thickness readings on the two middle courses were taken from the stairway. These plate thickness values are in Table 1. The average of the 22 measurements taken on the bottom shell course was 1.153 inches and the lowest reading was 1.112 inches. No precise previous information is available for shell plate thickness to determine original shell thickness or shell deterioration rates. A calculation for the minimum thickness required by API 653 for the shell bottom course is provided in Appendix B. The minimum allowable thickness of the bottom shell course was calculated to be one inch (tmin = 1.00 inches). All measurements on the base course exceeded this thickness. The thickness of each measurement on the shell plate is shown in Figure 6.0. 3.2 Tank Shell Appurtenances

Several different types of appurtenances are attached to the tank shell. Each component was visually inspected for soundness of welds and signs of corrosion. The results of this investigation on the following components are as follows. 3.2.1 Manholes

There are four manholes or entrance points, see Figure 4.0 for the locations. These consist of a 48-inch diameter circular entrance with a doubler plate stiffener on the shell plate. The manhole protrudes from the plane of the shell with a spool piece and has a flanged cover with approximately 35 – ¾” bolts. The contractor indicated that using an impact air powered wrench each bolt was removed on three of the entrances. Each manhole was in good condition with only minor corrosion at points where the coating had failed.

6


3.2.2 Access Openings There is one access opening through the tank shell that consists of a doubler plate bolted over an opening, see Figure 4.0 for the location. This opening is approximately 57 inches tall and 170 inches wide with 160 – ¾” bolts. The connection between the doubler plate and the tank shell does exhibit some seepage of tank product.

3.2.3 Overflow Vents There are eight overflow vents around the perimeter of the tank. The overflow vents consist of a funnel inside the tank that is at the maximum liquid level within the tank. This funnel reduces to an eight-inch pipe that then protrudes out the tank at the top shell plate course and then runs to within a foot of the ground terminating at a 22.5 degree bend. These overflows are designed to relieve interior pressure that could occur due to overfilling. One of these overflow vents is the lowest of the vents and is designed to discharge product first. This vent is connected to above ground piping through a gate valve and is connected to the tank discharge piping. This vent to piping connection is exhibiting seepage and has formed a pool of product on the pavement.

3.2.4 Pipe Nozzles There are five pipe nozzle connections protruding from the base course of the shell. These nozzles are approximately six inches in diameter terminating at a gate valve and a blind flange. Each nozzle is in good condition with minor corrosion due to point failures of the coating system.

3.2.5 Stairway

One stairway extends up the side of the tank to provide access to the roof. A small platform is located at the top of the stairway and is level with the tank roof. The stairway consists of metal grate steps welded to the tank shell and metal handrails welded to the steps. The stairway and platform are in fair condition with minor corrosion due to point failures of the coating system. In addition, several welds have failed on the railing and stair grates resulting in an unstable stairway. 3.2.6 Liquid Level Sensor

One liquid level sensor is located on the exterior side of the tank in the middle of a vertical black coating stripe. The level sensor was manufactured by Varco International and is not operational. The sensor is attached from the roof of the tank to hang a float in the interior of the tank. This roof attachment is broken allowing for water to enter from the resulting hole. Several of the level support hangers exhibit minor corrosion due to point failures of the coating system.

7


3.2.7 Wind Girders

Two wind girders or shell stiffeners are located near the top of the tank and extend for the entire circumference of the tank. These girders consist of L6x6x3/4 angles spaced vertically at 6’-3” and are welded to the top portion of the tank shell. Welded plate stiffeners help support the angles. The wind girders were inspected from the tank stairway. The welds appear sound and intact. The coating system in some locations is peeling from the steel and minor corrosion is present.

4.0 TANK ROOF INSPECTION

4.1 Roof Plating The tank roof plating is in good condition. An exterior visual inspection indicated that the plate lap welds are intact and sound. There is no indication of corrosion or weld discontinuity. The weld was also found to be intact at the circumference where the roof plates are welded to the angle stiffener that extends around the tank perimeter. The only exceptions were at two locations, measuring a total of approximately 2 feet, where the weld will require repair. Surface rust and small blisters are evident on the roof plates in some areas. These defects do not affect the integrity of the roof plating and are easily repaired. Twenty four tank roof plating thickness measurements were taken around the perimeter of the roof, twenty thickness measurements were taken on a 50 foot radius and six thickness measurements were taken on a 10 foot radius. The average thickness of the roof plating was 0.255 inches with a minimum reading of 0.228 inches. This corresponds with an as-built thickness of 0.25 inches. The minimum thickness reading exceeds the API 653 minimum requirement of 0.09 inches in any 100 square inches, and is therefore acceptable.

The tank roofs do not have perimeter handrails as required by current criteria. Handrails only occur at the top of the access stairway and extend approximately 6 feet either side of the stairway platform. One handrail is loose and will require re-welding. A visual inspection was conducted on the underside of the roof plating from a moveable scaffold positioned at four locations in the tank interior. The bottom of the roof plating appears to be unpainted and is covered by a thin coating of rust throughout. The roof plating is not welded to the supporting roof rafters.

8


4.2 Roof top Appurtenances Several different types of appurtenances are attached to the tank roof. Each component was visually inspected for soundness of welds and signs of corrosion. The results of this investigation on the following components are as follows. 4.2.1 Gooseneck Vents

There are eight gooseneck vents located around the perimeter of the tank. These vents prevent rain from entering while ensuring adequate airflow through the zone above the product level and the tank roof. These vents are in good condition with corrosion evident where the peripheral roof vents penetrate the roof. In addition several of the bolts attaching the vents have significant corrosion.


There are four access openings in the roof of the tank. These openings are approximately 42 inches in diameter and have approximately 35 – ¾” bolts attaching a blind flange. The condition of these access openings is fair with corrosion evident where the peripheral roof vents penetrate the roof. In addition, several of the bolts attaching the access openings have significant corrosion.

4.2.3 Sampling Port

There is one six-inch diameter sampling port near the stairway landing. This access port is for sampling and manual level sensing. The access port is in good condition but is missing a cover or cap.

4.3 Roof Support Framing The roof plating is supported by roof rafters radiating from the roof center. See Figure 2.0 for the roof-framing plan. The rafters are supported by roof beams, which are in turn supported by standard API columns. Each column terminates at a steel member foundation at the tank bottom. The column support foundation is not welded to the bottom plate. Plate clips welded to the tank bottom prevent lateral movement of the column foundation. A movable scaffold was erected inside the tank and used to inspect the roof plating and framing. The scaffold was positioned at the center column and then subsequently moved to an inner column, outer column and then located at the tank shell adjacent to a roof vent opening, The rafters and beams are in good condition with no indications of deterioration or loss of metal. The rafters and beams have a light coating of rust and there is no evidence that they were ever painted. The bolted connection of the roof beam to the column top is

9


slighted rusted but intact with all nuts visible and in good condition. A single rafter, between the inner and outer support beams became dislodged and fell to the tank bottom below. A dent was formed in the plating but the plate was not punctured. It is assumed that lack of adequate bearing length at one end coupled with a seismic event is the cause for this incident. The rafters are held in position with L2x2x3/16 angles welded to each rafter at midspan. The fillet weld on several of these spacers failed causing the angle to fall to the tank floor. These were collected by the contractor and stored. It appears that these angles were used to maintain the spacing between the rafters during initial installation of the roof plating. The roof support columns, consisting of channels welded together, are in good condition with no evidence of corrosion or horizontal deflection. The supporting channel foundation at each column location is also in good condition. The upper 10 feet of the columns have a slight coating of rust. The remainder of the column and also the support foundation appear to be coated.

5.0 TANK IN-PLANE LEVEL SURVEY

A survey was conducted to analyze the type of settlement that has occurred. No prior survey has been conducted to establish a rate or progression of settlement occurring. This information is however able to detect the magnitude of the existing out of plane alignment. The survey was conducted in accordance with API 653 Appendix C “Evaluation of Tank Bottom Settlement”.

On March 4, 2004, Prudencio R. Balagtas & Associates preformed a level survey around the exterior perimeter of the tank. Three temporary benchmarks were created and nineteen elevations were read at equal intervals around the tank. The outer “shelf” created by the shell-to-bottom connection was used for the survey. The datum used for the survey elevations is GGTN U.S.O. (GGN 2068) with elevation = 11.88’ Mean Sea Level (MSL). The results of this survey are included in Appendix C. The results indicate that there has been little to no differential settlement of the tank bottom. The average difference in elevations between the 32 feet intervals around the tank is 0.018 feet or 0.22 inches with a maximum difference of 0.058 feet or 0.70 inches. The average settlement corresponds to a slope of 0.056% slope between points. The magnitude of settlement is insignificant and no further analysis has been performed.

10


6.0 CATHODIC PROTECTION EVALUATION

In August of 1999 a survey of the cathodic protection system and electrical continuity testing was performed at the tank farm and pump station, including the tank bottoms. The results of the survey indicated that the structure-to-soil potential values, with the portable reference electrode located in the soil above the pipe or adjacent to the tank, met or exceeded minimum protection levels as established by NACE RP-0169-96. One of the criteria is satisfied where there is a negative potential of at least 850 mV, with the cathodic protection applied, and consideration given to IR drop. The potential is measured with respect to a copper-copper sulfate reference electrode contacting the electrolyte (soil).

The electrical continuity testing and the cathodic protection survey at the subject facility showed that all piping and both above ground storage tanks (ASTs) at the tank farm area were electrically continuous with one another and therefore with the four rectifiers. The four rectifiers include the GPA rectifier located at the delivery pumps near the tank farm, the GPA rectifier at Marine Drive, the Shell Oil and the US Navy rectifiers at the GORCO tie-in. The GPA rectifier located at the delivery pumps was not providing adequate cathodic protection current. The rectifier components were aged and weathered, but the rectifier was found to be operable when connected to a temporary anode ground bed. This indicated that either there was a break in the anode cable or that the anodes were depleted. The three rectifiers that were operating were providing sufficient cathodic protection current to meet the NACE criteria. Unfortunately, the three rectifiers are owned and/or operated by others; therefore there is no control over their continued operation and maintenance. Should these rectifiers malfunction, cathodic protection current would not be provided to the buried structures at the Piti tank farm and these buried structures would be subject to corrosion damage.

7.0 LEAK DETECTION EVALUATION

Tank 1935, when built, did not include a leak detection system to determine if the tank bottom was leaking fuel product. Currently the tank does not have a mechanism to accurately monitor fuel seepage into the ground and relies on visual inspection of the exterior only.

8.0 RECOMMENDATIONS

The following are recommended repairs and improvements for Tank1935 as a result of the inspection and evaluations noted above. The primary goal is to achieve a sound level of operation to allow continued service until the next scheduled inspection. The cost for the tank repairs is dependant on the scope of the repairs selected. The estimated cost for each recommended repair and improvement is included in Table 3.

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8.1 Tank Bottom The defective welds found in the tank bottom, should be repaired by air-arc gouging of the weld and re-welding the fillet weld for both the bottom plate lap joint welds and the interior bottom-to-shell connection weld. There are 22 locations where these repairs are required. Significant scale is present on the tank bottom. This scale will have to be removed to determine the extent of the pitting repairs and to more accurately quantify the number of deep pits that will require rewelding and where doubler plates may be required over an extensively pitted area. The deepest pits should be filled with weld and made flush with the top of the plate. Any doubler plate that is required should be fully welded to the tank bottom plates. The dent in the floor, where the rafter, fell should be repaired by placing a doubler plate over the damaged area and fillet welding the plate to seal the edges. Once the repairs have been completed, a new coating system should be applied to the tank bottom. 8.2 Tank Shell The coating of the tank shell exterior is of sufficient thickness to protect the metal where the coating has not been compromised due to the presence of small areas of corrosion. These areas should be cleaned and recoated in an effort to halt the corrosion progression. They are identified by either a blister of rust or rust streaking from rain-washing the oxidized metal down the shell. In addition, the wind girders on the shell have flaking paint on the underside and will need to be recoated. It is not anticipated that the shell exterior will require additional coating. A new coating system should be applied to the tank shell interior. The existing scale and remnants of a previous coating should be removed and the entire surface cleaned to bare metal prior to application of the new coating system. 8.3 Tank Roof

The coating of the topside roof plating is adequate and a new coating system is not required. Small areas of corrosion in the form of rust blisters are present and will require cleaning and recoating. Two welds, at the tank roof perimeter, approximately two feet long will need to be air-arc gouged and re-welded. The roof rafter that fell from the roof will need to be replaced and re-welded at each end to the supporting beams.

12


A new coating system should be applied to the roof rafters, underside of the roof plating, and the top 10 feet of the support columns after these items have been sand blasted to bare metal. 8.4 Appurtenances 8.4.1 Tank Roof

The access openings and gooseneck vents will need to be wire brushed or sand blasted to bare metal and then recoated. Approximately 1/3 of the bolts will need to be replaced due to progressive corrosion. In addition, one access opening cover will need to be replaced due to advanced corrosion intruding laterally into the plate. The cover on the sampling port adjacent to the stairway platform is missing and a new one is required.

8.4.2 Tank Shell

One ground strap that electrically connects the tank shell to the earth below the tank is broken and will need to be replaced.

The large bolted access opening on the tank shell appears to have some product leakage at some of the bolts. It did not appear that a gasket to seal the area had been installed. A gasket for sealing the area should be installed and the bolts retightened. The tank is filled through a 24-inch diameter pipe that has two exterior gate valves. These gate valves appear to have product leaking from the rising stems. These valves should be reviewed in order to determine if seals have been compromised or if the fuel spillage is due to valve maintenance activities only. The piping connecting the lowest overflow vent has a return line looped into above ground piping to collect the overfill volume of product. This overflow vent is connected to the pipeline through a reducer fitting and a gate valve. This connection is leaking and should be examined to determine the appropriate repair or replacement strategy.

8.5 Cathodic Protection System

In order to ensure that the buried structures in the pump station receive adequate protection, it is recommended that a new impressed current ground bed be designed and installed for the rectifier at the GPA Delivery Pump area so that it may again operate as designed. The recommended design life of the anode ground bed is at least 20 years. As the existing rectifier is showing signs of age, it is also recommended that the rectifier be replaced with a new air cooled rectifier, in order to ensure that the system will continue to operate for at least 20 years, to coincide with the design life of the ground bed. The existing negative cable to the buried structure was found to be reusable.

13


The effectiveness of testing the cathodic protection levels of the bottoms of tanks is dependent on reference electrode placement. These above ground storage tanks were constructed on a 6.7-foot thick layer of compacted fill. When the cathodic protection system was tested, the reference electrode was placed in contact with the soil, near the edge of the tank bottom, around the circumference of the tank. The potential values measured with a reference cell at the tank edge represent the level of protection for those areas at the outer periphery of the tank, close to the reference electrode. Potentials measured at the outer perimeter of the tank are not necessarily representative of those nearer to the center of the tank. At present there is no means for measurement of these values, and since the tank bottom is more than 200 feet in diameter, there is greater concern for achieving adequate protection than for a smaller diameter tank. Installation of a slotted plastic monitoring pipe under the tanks would permit the use of a portable reference electrode to measure the protection levels across the entire tank bottom.

It is anticipated that the steel plates near the center of the tank bottom may be difficult to protect, since the bottom is uncoated and the outer portions of the tank bottom may be receiving most of the cathodic protection current. It is recommended that anodes be installed the tank, in order to ensure full cathodic protection coverage. Installing a cathodic protection system and permanent reference electrodes underneath the tank, would ensure that the entire tank bottom was receiving adequate cathodic protection current. When installing a cathodic protection system under an existing tank, a horizontal boring method is commonly used for the placement of the anodes and the permanent reference electrodes. The anodes recommended for use in this application are mixed metal oxide, impressed current, linear anodes that are factory packaged with coke backfill in a flexible galvanized steel housing. The anodes come with a pull ring on one end, and are easily pulled through a horizontally drilled hole.

Tank Nos. 1934 and 1935, which are 200-foot diameter, would require four horizontal bores at an approximate 10 foot depth: three for the anodes, and one for portable reference electrodes. An anode junction box for the anode cables and reference electrode cables would be installed on or near the side of each tank. The anode header cable from each junction box and the structure negative lead from each tank would be routed below grade to the air-cooled rectifiers in the new electrical room. The two cathodic protection systems would operate independently. Each system would be designed for a service life of 20 years.

Electrical isolation of the structures at the pump station site should be maintained from buried piping located outside the pump station. This practice enables the project cathodic protection current to be applied to the structures at the site and reduces current being applied to foreign structures. The pump station should be electrically isolated from the piping outside of the tank farm, as well as the supply pipeline. This would limit the potential demand on the cathodic protection systems to the tank structures and piping at the site. Provision of electrical isolation should be accomplished by the installation of insulating flange kits. The insulating flange kits should be installed above grade, whenever possible.

14


After repairs are complete and the cathodic protection systems are energized, monthly monitoring should be done by operations staff to confirm that the rectifiers are operating. This should include checking of the panel meters on the rectifier, which indicates DC voltage and current. Blank forms should be included as part of the report to be submitted upon completion of recommendations. These monthly readings should be kept on file for future records. 8.6 Leak Detection System

As installation of leak detection equipment is being considered for both of the tanks at the site, CONCECO/MATCOR investigated what types of systems are commercially available and which could be installed to monitor the tanks at the Piti Tank Farm. The following information was gathered during the investigation.

It has been assumed that the equipment would be required for detection of small leaks, as large leaks would be discovered by the tank operators. The following is a description of two feasible methods for detection of leaks in existing tanks. 8.6.1 Intermittent Monitoring with Portable Sensor

Hydrocarbon sensors, like all sensors, have a limited range, and in order to monitor one quadrant of a 200-foot diameter tank, the sensor would have to be inserted 50 feet into a slotted sampling pipe that goes under the tank. With the current technology the sensor probes required to detect fuel oil no. 6 do not provide an instantaneous “go”/“no-go” signal. The sensor probe must first stabilize and come to temperature equilibrium before it can sample the vapor. If the probe has been sitting in a warm car, it will take 15 minutes or more before it reaches the lower temperature of the sampling port pipe. The sensors that emit a digital signal send information regarding the hydrocarbon level faster than sensors that emit an analog signal to the data logger, which in turn the data logger must process the analog data. A typical sampling time would be five minutes. Regardless of how fast the information regarding the hydrocarbon level is provided, that level must be seen in its context. There is often some prior level of contamination in tank farms in general. That background contamination level must be taken into account, so that the current level sensed does not give a false alarm. The alarm threshold must be adjusted to be above the background level. Determination of the background contamination level, if any, requires that readings be taken over a period of days or weeks. The background hydrocarbon level is typically dynamic, influenced by temperature and height of the water table. For example, any background contamination level is likely to be higher during the rainy season. An early morning reading may show a different reading than one taken in the afternoon. On a daily basis (or a weekly basis) the readings would need to be taken at the same time of the day.

The use of Intermittent Monitoring using a Portable Sensor would require two horizontal bores or four diagonal bores, installed below the existing 200-foot diameter tank. A

15


slotted well screen pipe with 20 percent perforation would be installed in each bore hole, with a sweeping 90 degree PVC elbow and riser at each end of the horizontal bore. The above grade end of each pipe would be equipped with a screw-off cap. The technician would remove the cap, insert a portable probe approximately 50 feet horizontally, through the pipe using a push rod, and then wait until the probe reaches equilibrium. The technician would then record a 5-minute sample with the data logger-monitor. After the end of the sample period, the technician would remove the probe, replace the cap on the pipe, performing the sampling a total of four times under each tank.

One such portable system would be the Petrosense ® PHA-100+ hydrocarbon analyzer manufactured by FCI Environmental, Inc. The PHA-100 uses an analog, fiber optic chemical sensor that is built into a portable analyzer.

The cost of the PHA-100+ analyzer, one additional probe, one calibration kit, and installation of the boreholes and PVC, would be approximately $65,000 for the first tank. The cost for the second tank, which would require only the installation of the boreholes and PVC, would be approximately $30,000. 8.6.2 Continuous Monitoring with Permanent Sensors Continuous Monitoring with Permanent Sensors would require two horizontal bores, beneath the existing 200-foot diameter tank. A slotted well screen pipe with 20 percent perforation would be installed in each bore hole, with a sweeping 90 degree PVC elbow and riser at each end, as described for the previous system. Four sensors would be permanently installed, two in each pipe. The two sensor cables would be routed to the junction box. One end of the pipe would be capped and the other end would be equipped with a junction box. The cables would be routed from the junction box to the computerized hardware, located inside an electrical room. The hardware would require a continuous 110 or 220 volts AC electrical supply. The system could be supplemented with a small wind generator, about the size of a weather vane.

One such system would use DHP-485 digital hydrocarbon probes and the CMS-5000 continuous monitoring logger, manufactured by FCI Environmental, Inc. The probe is a fiber optic chemical sensor that can respond reversibly to increasing or decreasing levels of hydrocarbons. Trends in the level of any contamination can be seen over time, through continuous monitoring. The probes are capable of sensing new leaks, even in the presence of old contamination. As an example, if product has leaked from the tank through any of the cracked welds on the floor found during the 2004 inspection, the CMS-5000 system is capable of baseline adjustment. With four probes installed at a 3 foot depth under a 200 foot diameter tank, on a pad material of standard sand and pea gravel, the system would be able to detect a leakage rate of 0.2 gallons per hour within 30 days. However, as drilling through the 6.7 foot layer of compacted fill, underneath the tank, may be difficult if the maximum diameter of the aggregate exceeds several inches; the horizontal bore may need to be deeper than 3 feet. At a 10-foot installation depth the probes would take longer than 30 days to detect a leakage rate of 0.2 gallons per hour.

16


The system has a backup battery and can continue to function on the battery backup for up to 7 days. After a power failure, the system will automatically restart.

The cost of installing two bores, piping, four CMS-485 sensors and the CMS-5000 data logger would be approximately $125,000 for the first tank. The second tank could use the same data logger; so the cost for the second tank would be approximately $85,000.

Coordination would be required with the installation of the leak detection system and design of the cathodic protection systems for the tank bottoms, so that there is no interference with the installation of the horizontal bores for the cathodic protection system. The CMS-485 probe cannot be installed in the same pipe as the anodes. If an anode comes in direct contact and touches a probe, the probe would become damaged. If the horizontal boring for both the leak detection system and the cathodic protection system is performed at the same time, there could be additional cost savings. 8.7 Tank Inspection Program

It is recommended that the Guam Power Authority establish a Tank Inspection Program. Inspections should be preformed every ten years unless subsequent inspection information can be used to justify a longer period. This tank should be drained, cleaned and inspected in ten years to re-evaluate the condition of the tank interior. At this inspection time, rates of corrosion can be determined, remaining life of the tank bottom can be reassessed and the structural integrity can be recorded. A regular external inspection regiment should be established to aid in the inspection scope and intervals. This should be comprised of two types of inspections: routine in service inspections and external inspections. Owner/operator personnel knowledgeable of the storage facility operations, the tank and the characteristics of the product stored should preform routine in-service inspections at least every month. The external inspections should be preformed at least every five years by an authorized inspector. The scope of the external inspections should be established using API 653 as a guide and at a minimum the checklists in Appendix C should be used. All existing tank information including, external and internal inspection reports and tank service records should be maintained in one location or Tank1935 File. This File will contain all information known concerning the operation and maintenance of this tank and will provide future inspectors the background information to accurately access the integrity of the tank.

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TABLE 1

Table 1Ultrasonic Thickness MeasurementsGPA Bulk Fuel Storage Tank 1935

March 2004

Location Plate # ID #

Plate Thickness

(inch)

Coating Thickness

(mils)Wall, Course 1 1 0001 1.153 11Wall, Course 1 2 0004 1.155 12Wall, Course 1 3 0007 1.153 8Wall, Course 1 4 0010 1.172 16Wall, Course 1 5 0013 1.146 10Wall, Course 1 6 0016 1.156 14Wall, Course 1 7 0019 1.112 7Wall, Course 1 8 0022 1.166 13Wall, Course 1 9 0025 - -Wall, Course 1 10 0028 1.134 11Wall, Course 1 11 0031 1.148 16Wall, Course 1 11 0031 1.156 15Wall, Course 1 12 0034 1.166 15Wall, Course 1 13 0037 1.160 14Wall, Course 1 14 0040 1.175 14Wall, Course 1 15 0043 1.162 14Wall, Course 1 16 0046 1.151 13Wall, Course 1 17 0049 1.138 11Wall, Course 1 18 0052 1.168 14Wall, Course 1 19 0055 1.148 15Wall, Course 1 20 0058 1.161 14Wall, Course 1 21 0061 1.129 11Wall, Course 2 1 0002 0.828 -Wall, Course 2 2 0005 0.830 -Wall, Course 2 3 0008 0.875 -Wall, Course 2 3 0011 0.897 -Wall, Course 2 4 0014 0.871 -Wall, Course 2 5 0017 0.874 -Wall, Course 2 6 0020 0.830 -Wall, Course 2 8 0023 0.831 -Wall, Course 2 9 0026 0.830 -Wall, Course 2 10 0029 0.894 -Wall, Course 2 11 0032 0.806 -Wall, Course 2 12 0035 0.896 -

Table1 UT -Tank 1935 Page 1 of 29


March 2004


Plate Thickness

(inch)

Coating Thickness

(mils)Wall, Course 2 13 0038 0.831 -Wall, Course 2 14 0041 0.831 -Wall, Course 2 15 0044 0.903 -Wall, Course 2 16 0047 0.830 -Wall, Course 2 17 0050 0.830 -Wall, Course 2 18 0053 0.832 -Wall, Course 2 19 0056 0.832 -Wall, Course 2 20 0059 0.901 -Wall, Course 2 21 0062 0.899 -Wall, Course 3 1 0003 0.723 -Wall, Course 3 2 0006 0.872 -Wall, Course 3 3 0009 0.769 -Wall, Course 3 4 0012 0.728 -Wall, Course 3 5 0015 0.727 -Wall, Course 3 6 0018 0.710 -Wall, Course 3 7 0021 0.739 -Wall, Course 3 8 0024 0.803 -Wall, Course 3 9 0027 0.723 -Wall, Course 3 10 0030 0.735 -Wall, Course 3 11 0033 0.833 -Wall, Course 3 12 0036 0.736 -Wall, Course 3 13 0039 0.832 -Wall, Course 3 14 0042 0.738 -Wall, Course 3 15 0045 0.777 -Wall, Course 3 16 0048 0.768 -Wall, Course 3 17 0051 0.726 -Wall, Course 3 17 0054 0.831 -Wall, Course 3 18 0057 0.807 -Wall, Course 3 19 0060 0.733 -Wall, Course 3 20 0063 0.831 -Wall, Course 4 7 0064 0.545 -Wall, Course 5 6 0065 0.315 -Wall, Course 5 7 0066 0.395 -Wall, Course 6 1 - 0.290 -



March 2004


Plate Thickness

(inch)

Coating Thickness

(mils)Wall, Course 6 2 - 0.298 -Wall, Course 6 3 - 0.289 -Wall, Course 6 4 - 0.314 -Wall, Course 6 5 - 0.298 -Wall, Course 6 6 - 0.316 -Wall, Course 6 7 - 0.314 -Wall, Course 6 8 - 0.299 -Wall, Course 6 9 - 0.307 -Wall, Course 6 10 - 0.320 -Wall, Course 6 11 - 0.313 -Wall, Course 6 12 - 0.300 -Wall, Course 6 13 - 0.307 -Wall, Course 6 14 - 0.313 -Wall, Course 6 15 - 0.314 -Wall, Course 6 16 - 0.312 -Wall, Course 6 17 - 0.312 -Wall, Course 6 18 - 0.314 -Wall, Course 6 19 - 0.306 -Wall, Course 6 19 - 0.304 -Wall, Course 6 20 - 0.308 -Roof (10' Radius from Center) 137 1 0.259 -Roof (10' Radius from Center) 138 2 0.254 16Roof (10' Radius from Center) 125 3 0.259 -Roof (10' Radius from Center) 116 4 0.255 -Roof (10' Radius from Center) 115 5 0.254 -Roof (10' Radius from Center) 126 6 0.256 -Roof (along man hole) 126 6 0.257 -Roof 104 - - 10Roof 170 - - 13Roof 181 - - 10Roof (50' Radius from Center) 200 7 0.254 -Roof (50' Radius from Center) 201 8 0.262 -Roof (50' Radius from Center) 189 9 0.278 -Roof (50' Radius from Center) 182 10 0.251 -



March 2004


Plate Thickness

(inch)

Coating Thickness

(mils)Roof (50' Radius from Center) 167 11 0.261 -Roof (50' Radius from Center) 160 12 0.257 -Roof (50' Radius from Center) 145 13 0.259 -Roof (50' Radius from Center) 140 14 0.257 -Roof (50' Radius from Center) 123 15 0.261 -Roof (50' Radius from Center) 118 16 0.247 -Roof (50' Radius from Center) 101 17 0.267 -Roof (50' Radius from Center) 95 18 0.264 -Roof (50' Radius from Center) 80 19 0.265 -Roof (50' Radius from Center) 74 20 0.253 -Roof (50' Radius from Center) 60 21 0.257 -Roof (50' Radius from Center) 51 22 0.268 -Roof (50' Radius from Center) 52 23 0.256 -Roof (50' Radius from Center) 62 24 0.253 -Roof (50' Radius from Center) 70 25 0.258 -Roof (50' Radius from Center) 84 26 0.261 -Roof (50' Radius from Center) 91 27 0.250 -Roof (50' Radius from Center) 106 28 0.261 -Roof (50' Radius from Center) 113 29 0.261 -Roof (50' Radius from Center) 128 30 0.228 -Roof (50' Radius from Center) 135 31 0.252 -Roof (50' Radius from Center) 150 32 0.254 -Roof (50' Radius from Center) 156 33 0.258 -Roof (50' Radius from Center) 171 34 0.259 -Roof (50' Radius from Center) 178 35 0.245 -Roof (50' Radius from Center) 191 36 0.254 -Roof 4 - - 13Roof 11 - - 11Roof 28 - - 10Roof 42 - - 12Roof 58 - - 12Roof 90 - - 13Roof 99 - - 15Roof 131 - - 13



March 2004


Plate Thickness

(inch)

Coating Thickness

(mils)Roof 141 - - 16Roof 181 - - 10Roof 198 - - 15Roof 208 - - 13Roof 216 - - 12Roof 233 - - 15Roof 241 - - 18Roof (99' Radius from Center) 249 37 0.250 -Roof (99' Radius from Center) 246 38 0.248 -Roof (99' Radius from Center) 243 39 0.252 -Roof (99' Radius from Center) 239 40 0.251 -Roof (99' Radius from Center) 237 41 0.244 -Roof (99' Radius from Center) 206 42 0.235 -Roof (along man hole) 206 43 0.250 -Roof (99' Radius from Center) 164 44 0.263 -Roof (99' Radius from Center) 121 45 0.254 -Roof (99' Radius from Center) 77 46 0.261 -Roof (99' Radius from Center) 47 47 0.254 -Roof (99' Radius from Center) 21 48 0.248 -Roof (along man hole) 21 49 0.257 -Roof (99' Radius from Center) 2 50 0.249 -Roof (99' Radius from Center) 6 51 0.254 -Roof (99' Radius from Center) 10 52 0.247 -Roof (99' Radius from Center) 14 53 0.251 -Roof (99' Radius from Center) 29 54 0.251 -Roof (99' Radius from Center) 45 55 0.254 -Roof (99' Radius from Center) 66 56 0.247 -Roof (99' Radius from Center) 109 57 0.254 -Roof (99' Radius from Center) 154 58 0.247 -Roof (99' Radius from Center) 195 59 0.260 -Roof (99' Radius from Center) 230 60 0.236 -Roof (along man hole) 232 61 0.258 -Roof (along man hole) 232 62 0.254 -Floor 1 01001 0.257 NA



March 2004


Plate Thickness

(inch)

Coating Thickness

(mils)Floor 1 02001 0.271 NAFloor 1 03001 0.292 NAFloor 1 04001 0.293 NAFloor 2 01002 0.297 NAFloor 2 02002 0.313 NAFloor 2 03002 0.344 NAFloor 2 04002 0.298 NAFloor 3 01003 0.266 NAFloor 3 02003 0.342 NAFloor 3 03003 0.326 NAFloor 3 04003 0.292 NAFloor 3A - 0.322 NAFloor 3A - 0.273 NAFloor 3A - 0.332 NAFloor 3A - 0.322 NAFloor 4 01004 0.322 NAFloor 4 02004 0.254 NAFloor 4 03004 0.311 NAFloor 4 04004 0.292 NAFloor 5 01005 0.332 NAFloor 5 02005 0.241 NAFloor 5 03005 0.317 NAFloor 5 04005 0.303 NAFloor 6 01006 0.366 NAFloor 6 02006 0.313 NAFloor 6 03006 0.280 NAFloor 6 04006 0.289 NAFloor 7 01007 0.322 NAFloor 7 02007 0.327 NAFloor 7 03007 0.254 NAFloor 7 04007 0.322 NAFloor 8 01008 0.254 NAFloor 8 02008 0.329 NAFloor 8 03008 0.290 NA



March 2004


Plate Thickness

(inch)

Coating Thickness

(mils)Floor 8 04008 0.317 NAFloor 9 01009 0.256 NAFloor 9 02009 0.264 NAFloor 9 03009 0.304 NAFloor 9 04009 0.289 NAFloor 10 01010 0.291 NAFloor 10 02010 0.317 NAFloor 10 03010 0.309 NAFloor 10 04010 0.319 NAFloor 11 01011 0.301 NAFloor 11 02011 0.281 NAFloor 11 03011 0.230 NAFloor 11 04011 0.269 NAFloor 12 01012 0.329 NAFloor 12 02012 0.318 NAFloor 12 03012 0.312 NAFloor 12 04012 0.315 NAFloor 13 01013 0.334 NAFloor 13 02013 0.315 NAFloor 13 03013 0.318 NAFloor 13 04013 0.320 NAFloor 14 01014 0.294 NAFloor 14 02014 0.299 NAFloor 14 03014 0.302 NAFloor 14 04014 0.319 NAFloor 15 01015 0.365 NAFloor 15 02015 0.327 NAFloor 15 03015 0.291 NAFloor 15 04015 0.333 NAFloor 16 01016 0.298 NAFloor 16 02016 0.272 NAFloor 16 03016 0.290 NAFloor 16 04016 0.317 NAFloor 17 01017 0.291 NA



March 2004


Plate Thickness

(inch)

Coating Thickness




March 2004


Plate Thickness

(inch)

Coating Thickness




March 2004


Plate Thickness

(inch)

Coating Thickness




March 2004


Plate Thickness

(inch)

Coating Thickness




March 2004


Plate Thickness

(inch)

Coating Thickness




March 2004


Plate Thickness

(inch)

Coating Thickness




March 2004


Plate Thickness

(inch)

Coating Thickness




March 2004


Plate Thickness

(inch)

Coating Thickness

(mils)Floor 76 04076 0.322 NAFloor 77 01077 0.303 NAFloor 77 02077 0.301 NAFloor 77 03077 0.314 NAFloor 77 04077 0.325 NAFloor 78 01078 0.316 NAFloor 78 02078 0.317 NAFloor 78 03078 0.314 NAFloor 78 04078 0.331 NAFloor 79 01079 0.314 NAFloor 79 02079 0.315 NAFloor 79 03079 0.316 NAFloor 79 04079 0.280 NAFloor 80 01080 0.286 NAFloor 80 02080 0.318 NAFloor 80 03080 0.318 NAFloor 80 04080 0.317 NAFloor 81 01081 0.275 NAFloor 81 02081 0.257 NAFloor 81 03081 0.320 NAFloor 81 04081 --.-- NAFloor 82 01082 0.313 NAFloor 82 02082 0.303 NAFloor 82 03082 0.321 NAFloor 82 04082 0.306 NAFloor 83 01083 0.311 NAFloor 83 02083 0.345 NAFloor 83 03083 0.304 NAFloor 83 04083 --.-- NAFloor 84 01084 0.312 NAFloor 84 02084 0.310 NAFloor 84 03084 0.307 NAFloor 84 04084 0.317 NAFloor 85 01085 0.318 NA



March 2004


Plate Thickness

(inch)

Coating Thickness

(mils)Floor 85 02085 0.265 NAFloor 85 03085 0.329 NAFloor 85 04085 --.-- NAFloor 86 01086 0.308 NAFloor 86 02086 0.310 NAFloor 86 03086 0.332 NAFloor 86 04086 0.302 NAFloor 87 01087 0.309 NAFloor 87 02087 0.310 NAFloor 87 03087 0.310 NAFloor 87 04087 0.319 NAFloor 88 01088 0.320 NAFloor 88 02088 0.310 NAFloor 88 03088 0.311 NAFloor 88 04088 0.316 NAFloor 89 01089 0.326 NAFloor 89 02089 0.315 NAFloor 89 03089 0.313 NAFloor 89 04089 0.324 NAFloor 90 01090 0.315 NAFloor 90 02090 0.309 NAFloor 90 03090 0.313 NAFloor 90 04090 0.325 NAFloor 91 01091 0.301 NAFloor 91 02091 0.302 NAFloor 91 03091 0.303 NAFloor 91 04091 0.307 NAFloor 92 01092 0.329 NAFloor 92 02092 0.330 NAFloor 92 03092 0.326 NAFloor 92 04092 0.316 NAFloor 93 01093 0.306 NAFloor 93 02093 0.307 NAFloor 93 03093 0.307 NA



March 2004


Plate Thickness

(inch)

Coating Thickness

(mils)Floor 93 04093 0.334 NAFloor 94 01094 0.312 NAFloor 94 02094 0.305 NAFloor 94 03094 0.313 NAFloor 94 04094 0.318 NAFloor 95 01095 0.323 NAFloor 95 02095 0.334 NAFloor 95 03095 0.315 NAFloor 95 04095 0.305 NAFloor 96 01096 0.314 NAFloor 96 02096 0.321 NAFloor 96 03096 0.334 NAFloor 96 04096 0.330 NAFloor 97 01097 0.315 NAFloor 97 02097 0.315 NAFloor 97 03097 0.314 NAFloor 97 04097 0.324 NAFloor 98 01098 0.327 NAFloor 98 02098 0.319 NAFloor 98 03098 0.320 NAFloor 98 04098 0.319 NAFloor 99 01099 --.-- NAFloor 99 02099 --.-- NAFloor 99 03099 --.-- NAFloor 99 04099 --.-- NAFloor 100 01100 --.-- NAFloor 100 02100 --.-- NAFloor 100 03100 --.-- NAFloor 100 04100 0.315 NAFloor 101 01101 0.310 NAFloor 101 02101 0.316 NAFloor 101 03101 0.323 NAFloor 101 04101 0.315 NAFloor 102 01102 0.316 NA



March 2004


Plate Thickness

(inch)

Coating Thickness




March 2004


Plate Thickness

(inch)

Coating Thickness




March 2004


Plate Thickness

(inch)

Coating Thickness




March 2004


Plate Thickness

(inch)

Coating Thickness




March 2004


Plate Thickness

(inch)

Coating Thickness




March 2004


Plate Thickness

(inch)

Coating Thickness




March 2004


Plate Thickness

(inch)

Coating Thickness




March 2004


Plate Thickness

(inch)

Coating Thickness




March 2004


Plate Thickness

(inch)

Coating Thickness




March 2004


Plate Thickness

(inch)

Coating Thickness




March 2004


Plate Thickness

(inch)

Coating Thickness

(mils)Floor 187 02187 0.303 NAFloor 187 03187 0.313 NAFloor 187 04187 0.314 NAFloor 188 01188 0.323 NAFloor 188 02188 0.309 NAFloor 188 03188 0.326 NAFloor 188 04188 0.325 NAFloor 189 01189 0.302 NAFloor 189 02189 0.314 NAFloor 189 03189 0.310 NAFloor 189 04189 0.265 NAFloor 190 01190 0.311 NAFloor 190 02190 0.316 NAFloor 190 03190 0.316 NAFloor 190 04190 0.307 NAFloor 191 - 0.317 NAFloor 191 - 0.316 NAFloor 191 - 0.319 NAFloor 191 - 0.321 NAFloor 191A 01191 0.310 NAFloor 191A 02191 0.312 NAFloor 191A 03191 0.329 NAFloor 191A 04191 0.298 NAFloor 192 01192 0.295 NAFloor 192 02192 0.312 NAFloor 192 03192 0.316 NAFloor 192 04192 0.325 NAFloor 193 01193 0.311 NAFloor 193 02193 0.208 NAFloor 193 03193 0.312 NAFloor 193 04193 0.317 NAFloor 194 01194 0.316 NAFloor 194 02194 0.324 NAFloor 194 03194 0.319 NA



March 2004


Plate Thickness

(inch)

Coating Thickness

(mils)Floor 194 04194 0.317 NAFloor 195 01195 0.320 NAFloor 195 02195 0.317 NAFloor 195 03195 0.329 NAFloor 195 04195 --.-- NAFloor 196 01196 0.311 NAFloor 196 02196 0.314 NAFloor 196 03196 0.313 NAFloor 196 04196 0.310 NAFloor 197 01197 0.313 NAFloor 197 02197 0.307 NAFloor 197 03197 0.309 NAFloor 197 04197 0.339 NAFloor 198 01198 0.297 NAFloor 198 02198 0.296 NAFloor 198 03198 0.312 NAFloor 198 04198 0.302 NASupport Column - middle web (Center) - - 0.304 -Support Column - middle web (Middle) - - 0.341 -Support Column - middle web (Outer) - - 0.346 -

LocationMinimum

(inch)Maximum

(inch)Average

(inch)

Apparent Nominal

(inch)Loss * (inch) % Loss *

Wall. Course 1 0.723 1.172 0.934 1.125 0.402 35.7%Wall, Course 2 0.726 1.166 0.925 0.875 0.149 17.0%Wall, Course 3 0.710 1.175 0.919 0.8125 0.103 12.6%Wall, Course 4 0.545 0.545 0.545 0.5625 0.018 3.1%Wall, Course 5 0.315 0.395 0.355 0.375 0.060 16.0%Wall, Course 6 0.289 0.320 0.307 0.3125 0.024 7.5%Floor 0.208 0.366 0.311 0.3125 0.105 33.4%Roof 0.228 0.278 0.255 0.250 0.022 8.8%* When reviewing the loss data the reader should note the permissible minimum tolerance for steel plate was 0.010 inch (ASTM-A6). The calculated thickness losses have not been adjusted for thickness tolerances.

Summary of Ultrasonic Thickness Measurements


TABLE 2

Table 2Corrosion Pit Depths

GPA Bulk Fuel Storage Tank 1935March 2004

LocationPlate

#

Upper End of

Plate, Pit Depth (inch)

Lower End of Plate Pit, Depth (inch)

Nominal Thickness

(inch)

Remaining Thickness at Typical

Pit on Upper End

of Plate (inch)


Pit on Lower End

of Plate (inch)

Upper End of Plate

Percentage Loss (inch)

Lower End of Plate


Floor 1 0.040 0.075 0.3125 0.2725 0.238 12.8% 24.0%Floor 2 0.054 0.061 0.3125 0.2585 0.252 17.3% 19.5%Floor 3 0.117 0.082 0.3125 0.1955 0.231 37.4% 26.2%Floor 3A 0.054 0.062 0.3125 0.2585 0.251 17.3% 19.8%Floor 4 0.060 0.054 0.3125 0.2525 0.259 19.2% 17.3%Floor 5 0.068 0.074 0.3125 0.2445 0.239 21.8% 23.7%Floor 6 0.030 0.060 0.3125 0.2825 0.253 9.6% 19.2%Floor 7 0.040 - 0.3125 0.2725 - 12.8% -Floor 8 0.052 - 0.3125 0.2605 - 16.6% -Floor 9 0.044 - 0.3125 0.2685 - 14.1% -Floor 10 0.061 - 0.3125 0.2515 - 19.5% -Floor 11 0.035 - 0.3125 0.2775 - 11.2% -Floor 12 0.045 0.052 0.3125 0.2675 0.261 14.4% 16.6%Floor 13 0.095 0.105 0.3125 0.2175 0.208 30.4% 33.6%Floor 14 0.064 0.092 0.3125 0.2485 0.221 20.5% 29.4%Floor 15 0.069 0.074 0.3125 0.2435 0.239 22.1% 23.7%Floor 16 0.094 0.115 0.3125 0.2185 0.198 30.1% 36.8%Floor 17 0.070 0.132 0.3125 0.2425 0.181 22.4% 42.2%Floor 18 0.056 0.073 0.3125 0.2565 0.240 17.9% 23.4%Floor 19 0.049 0.036 0.3125 0.2635 0.277 15.7% 11.5%Floor 20 0.050 0.062 0.3125 0.2625 0.251 16.0% 19.8%Floor 21 0.052 - 0.3125 0.2605 - 16.6% -Floor 22 0.033 - 0.3125 0.2795 - 10.6% -Floor 23 0.030 - 0.3125 0.2825 - 9.6% -Floor 24 0.040 - 0.3125 0.2725 - 12.8% -Floor 25 0.051 - 0.3125 0.2615 - 16.3% -Floor 26 0.135 - 0.3125 0.1775 - 43.2% -Floor 27 0.132 0.038 0.3125 0.1805 0.275 42.2% 12.2%Floor 28 0.044 0.061 0.3125 0.2685 0.252 14.1% 19.5%Floor 29 0.062 0.048 0.3125 0.2505 0.265 19.8% 15.4%Floor 30 0.060 0.047 0.3125 0.2525 0.266 19.2% 15.0%Floor 31 0.062 0.120 0.3125 0.2505 0.193 19.8% 38.4%Floor 32 0.037 0.044 0.3125 0.2755 0.269 11.8% 14.1%Floor 33 0.035 0.053 0.3125 0.2775 0.260 11.2% 17.0%

Table2 Pit Depths -Tank 1935 Page 1 of 7



LocationPlate

#

Upper End of



Nominal Thickness

(inch)


Pit on Upper End

of Plate (inch)


Pit on Lower End

of Plate (inch)

Upper End of Plate


Lower End of Plate


Floor 34 0.042 0.036 0.3125 0.2705 0.277 13.4% 11.5%Floor 35 0.056 0.091 0.3125 0.2565 0.222 17.9% 29.1%Floor 36 0.086 0.125 0.3125 0.2265 0.188 27.5% 40.0%Floor 37 0.062 0.060 0.3125 0.2505 0.253 19.8% 19.2%Floor 38 0.049 0.069 0.3125 0.2635 0.244 15.7% 22.1%Floor 39 0.065 0.070 0.3125 0.2475 0.243 20.8% 22.4%Floor 40 0.083 0.065 0.3125 0.2295 0.248 26.6% 20.8%Floor 41 0.072 0.069 0.3125 0.2405 0.244 23.0% 22.1%Floor 42 0.097 0.072 0.3125 0.2155 0.241 31.0% 23.0%Floor 43 0.102 0.078 0.3125 0.2105 0.235 32.6% 25.0%Floor 44 0.110 0.112 0.3125 0.2025 0.201 35.2% 35.8%Floor 45 0.056 - 0.3125 0.2565 - 17.9% -Floor 46 0.060 - 0.3125 0.2525 - 19.2% -Floor 47 0.067 - 0.3125 0.2455 - 21.4% -Floor 48 0.030 - 0.3125 0.2825 - 9.6% -Floor 49 0.059 - 0.3125 0.2535 - 18.9% -Floor 50 0.049 - 0.3125 0.2635 - 15.7% -Floor 51 0.026 - 0.3125 0.2865 - 8.3% -Floor 52 0.039 - 0.3125 0.2735 - 12.5% -Floor 53 0.048 - 0.3125 0.2645 - 15.4% -Floor 54 0.049 - 0.3125 0.2635 - 15.7% -Floor 55 0.120 0.049 0.3125 0.1925 0.264 38.4% 15.7%Floor 56 0.045 0.061 0.3125 0.2675 0.252 14.4% 19.5%Floor 57 0.052 0.051 0.3125 0.2605 0.262 16.6% 16.3%Floor 58 0.082 0.015 0.3125 0.2305 0.298 26.2% 4.8%Floor 59 0.084 0.062 0.3125 0.2285 0.251 26.9% 19.8%Floor 60 0.120 0.100 0.3125 0.1925 0.213 38.4% 32.0%Floor 61 0.090 0.078 0.3125 0.2225 0.235 28.8% 25.0%Floor 62 0.078 0.027 0.3125 0.2345 0.286 25.0% 8.6%Floor 63 0.052 0.042 0.3125 0.2605 0.271 16.6% 13.4%Floor 64 0.066 0.032 0.3125 0.2465 0.281 21.1% 10.2%Floor 65 0.036 0.095 0.3125 0.2765 0.218 11.5% 30.4%Floor 66 0.025 0.138 0.3125 0.2875 0.175 8.0% 44.2%Floor 67 0.044 0.026 0.3125 0.2685 0.287 14.1% 8.3%




LocationPlate

#

Upper End of



Nominal Thickness

(inch)


Pit on Upper End

of Plate (inch)


Pit on Lower End

of Plate (inch)

Upper End of Plate


Lower End of Plate


Floor 68 0.130 0.023 0.3125 0.1825 0.290 41.6% 7.4%Floor 69 0.132 0.037 0.3125 0.1805 0.276 42.2% 11.8%Floor 70 0.095 0.055 0.3125 0.2175 0.258 30.4% 17.6%Floor 71 0.062 0.068 0.3125 0.2505 0.245 19.8% 21.8%Floor 72 0.065 0.041 0.3125 0.2475 0.272 20.8% 13.1%Floor 73 0.094 0.074 0.3125 0.2185 0.239 30.1% 23.7%Floor 74 0.032 0.032 0.3125 0.2805 0.281 10.2% 10.2%Floor 75 0.120 0.014 0.3125 0.1925 0.299 38.4% 4.3%Floor 76 0.050 0.019 0.3125 0.2625 0.294 16.0% 6.1%Floor 77 0.070 0.037 0.3125 0.2425 0.276 22.4% 11.8%Floor 78 0.102 - 0.3125 0.2105 - 32.6% -Floor 79 0.138 0.160 0.3125 0.1745 0.153 44.2% 51.2%Floor 80 0.053 - 0.3125 0.2595 - 17.0% -Floor 81 0.170 - 0.3125 0.1425 - 54.4% -Floor 82 0.165 - 0.3125 0.1475 - 52.8% -Floor 83 0.064 - 0.3125 0.2485 - 20.5% -Floor 84 0.085 - 0.3125 0.2275 - 27.2% -Floor 85 0.048 - 0.3125 0.2645 - 15.4% -Floor 86 0.034 - 0.3125 0.2785 - 10.9% -Floor 87 0.047 0.032 0.3125 0.2655 0.281 15.0% 10.2%Floor 88 0.067 0.065 0.3125 0.2455 0.248 21.4% 20.8%Floor 89 0.031 0.032 0.3125 0.2815 0.281 9.9% 10.2%Floor 90 0.030 0.080 0.3125 0.2825 0.233 9.6% 25.6%Floor 91 0.040 0.052 0.3125 0.2725 0.261 12.8% 16.6%Floor 92 0.027 0.024 0.3125 0.2855 0.289 8.6% 7.7%Floor 93 0.041 0.030 0.3125 0.2715 0.283 13.1% 9.6%Floor 94 0.108 0.084 0.3125 0.2045 0.229 34.6% 26.9%Floor 95 0.112 0.087 0.3125 0.2005 0.226 35.8% 27.8%Floor 96 0.130 0.095 0.3125 0.1825 0.218 41.6% 30.4%Floor 97 0.052 0.130 0.3125 0.2605 0.183 16.6% 41.6%Floor 98 0.088 0.075 0.3125 0.2245 0.238 28.2% 24.0%Floor 99 0.132 0.170 0.3125 0.1805 0.143 42.2% 54.4%Floor 100 0.123 0.100 0.3125 0.1895 0.213 39.4% 32.0%Floor 101 0.129 0.112 0.3125 0.1835 0.201 41.3% 35.8%




LocationPlate

#

Upper End of



Nominal Thickness

(inch)


Pit on Upper End

of Plate (inch)


Pit on Lower End

of Plate (inch)

Upper End of Plate


Lower End of Plate


Floor 102 0.131 0.216 0.3125 0.1815 0.097 41.9% 69.1%Floor 103 0.149 0.210 0.3125 0.1635 0.103 47.7% 67.2%Floor 104 0.065 0.152 0.3125 0.2475 0.161 20.8% 48.6%Floor 105 0.065 0.096 0.3125 0.2475 0.217 20.8% 30.7%Floor 106 0.095 0.078 0.3125 0.2175 0.235 30.4% 25.0%Floor 107 0.070 0.086 0.3125 0.2425 0.227 22.4% 27.5%Floor 108** 0.108 0.211 0.3125 0.2045 0.102 34.6% 67.5%Floor 109 0.095 0.195 0.3125 0.2175 0.118 30.4% 62.4%Floor 110 0.173 0.195 0.3125 0.1395 0.118 55.4% 62.4%Floor 111 0.102 0.151 0.3125 0.2105 0.162 32.6% 48.3%Floor 112 0.141 0.084 0.3125 0.1715 0.229 45.1% 26.9%Floor 113 0.058 - 0.3125 0.2545 - 18.6% -Floor 114 0.060 - 0.3125 0.2525 - 19.2% -Floor 115 0.064 - 0.3125 0.2485 - 20.5% -Floor 116 0.058 - 0.3125 0.2545 - 18.6% -Floor 117 0.067 - 0.3125 0.2455 - 21.4% -Floor 118 0.030 - 0.3125 0.2825 - 9.6% -Floor 119 0.061 - 0.3125 0.2515 - 19.5% -Floor 120 0.038 - 0.3125 0.2745 - 12.2% -Floor 121 0.062 - 0.3125 0.2505 - 19.8% -Floor 122 0.108 0.080 0.3125 0.2045 0.233 34.6% 25.6%Floor 123 0.053 0.056 0.3125 0.2595 0.257 17.0% 17.9%Floor 124 0.180 0.045 0.3125 0.1325 0.268 57.6% 14.4%Floor 125 0.092 0.077 0.3125 0.2205 0.236 29.4% 24.6%Floor 126 0.087 0.090 0.3125 0.2255 0.223 27.8% 28.8%Floor 127 0.098 0.060 0.3125 0.2145 0.253 31.4% 19.2%Floor 128 0.047 0.082 0.3125 0.2655 0.231 15.0% 26.2%Floor 129 0.099 0.115 0.3125 0.2135 0.198 31.7% 36.8%Floor 130 0.084 0.058 0.3125 0.2285 0.255 26.9% 18.6%Floor 131 0.060 0.091 0.3125 0.2525 0.222 19.2% 29.1%Floor 132 0.106 0.052 0.3125 0.2065 0.261 33.9% 16.6%Floor 133 0.130 0.118 0.3125 0.1825 0.195 41.6% 37.8%Floor 134 0.095 0.118 0.3125 0.2175 0.195 30.4% 37.8%Floor 135 0.098 0.077 0.3125 0.2145 0.236 31.4% 24.6%




LocationPlate

#

Upper End of



Nominal Thickness

(inch)


Pit on Upper End

of Plate (inch)


Pit on Lower End

of Plate (inch)

Upper End of Plate


Lower End of Plate


Floor 136 0.110 0.040 0.3125 0.2025 0.273 35.2% 12.8%Floor 137 0.091 0.084 0.3125 0.2215 0.229 29.1% 26.9%Floor 138 0.105 0.070 0.3125 0.2075 0.243 33.6% 22.4%Floor 139 0.087 0.087 0.3125 0.2255 0.226 27.8% 27.8%Floor 140 0.070 0.135 0.3125 0.2425 0.178 22.4% 43.2%Floor 141 0.082 0.135 0.3125 0.2305 0.178 26.2% 43.2%Floor 142 0.075 0.059 0.3125 0.2375 0.254 24.0% 18.9%Floor 143 0.072 0.064 0.3125 0.2405 0.249 23.0% 20.5%Floor 144 0.048 0.095 0.3125 0.2645 0.218 15.4% 30.4%Floor 145 0.039 - 0.3125 0.2735 - 12.5% -Floor 146 0.070 - 0.3125 0.2425 - 22.4% -Floor 147 0.089 - 0.3125 0.2235 - 28.5% -Floor 148 0.035 - 0.3125 0.2775 - 11.2% -Floor 149 0.042 - 0.3125 0.2705 - 13.4% -Floor 150 0.080 - 0.3125 0.2325 - 25.6% -Floor 151 0.068 - 0.3125 0.2445 - 21.8% -Floor 152 0.040 - 0.3125 0.2725 - 12.8% -Floor 153 0.038 - 0.3125 0.2745 - 12.2% -Floor 154 0.055 - 0.3125 0.2575 - 17.6% -Floor 155 0.040 - 0.3125 0.2725 - 12.8% -Floor 156 0.080 0.050 0.3125 0.2325 0.263 25.6% 16.0%Floor 157 0.098 0.068 0.3125 0.2145 0.245 31.4% 21.8%Floor 158 0.130 0.049 0.3125 0.1825 0.264 41.6% 15.7%Floor 159 0.118 0.039 0.3125 0.1945 0.274 37.8% 12.5%Floor 160 0.064 0.095 0.3125 0.2485 0.218 20.5% 30.4%Floor 161 0.092 0.100 0.3125 0.2205 0.213 29.4% 32.0%Floor 162 0.077 0.093 0.3125 0.2355 0.220 24.6% 29.8%Floor 163 0.042 0.085 0.3125 0.2705 0.228 13.4% 27.2%Floor 164 0.059 0.066 0.3125 0.2535 0.247 18.9% 21.1%Floor 165 0.038 0.107 0.3125 0.2745 0.206 12.2% 34.2%Floor 166 0.084 0.088 0.3125 0.2285 0.225 26.9% 28.2%Floor 167 0.160 0.105 0.3125 0.1525 0.208 51.2% 33.6%Floor 168 0.096 0.100 0.3125 0.2165 0.213 30.7% 32.0%Floor 169 0.158 0.110 0.3125 0.1545 0.203 50.6% 35.2%




LocationPlate

#

Upper End of



Nominal Thickness

(inch)


Pit on Upper End

of Plate (inch)


Pit on Lower End

of Plate (inch)

Upper End of Plate


Lower End of Plate


Floor 170 0.088 0.097 0.3125 0.2245 0.216 28.2% 31.0%Floor 171 0.083 0.094 0.3125 0.2295 0.219 26.6% 30.1%Floor 172 0.080 - 0.3125 0.2325 - 25.6% -Floor 173 0.032 - 0.3125 0.2805 - 10.2% -Floor 174 0.047 - 0.3125 0.2655 - 15.0% -Floor 175 0.062 - 0.3125 0.2505 - 19.8% -Floor 176 0.071 - 0.3125 0.2415 - 22.7% -Floor 177 0.060 - 0.3125 0.2525 - 19.2% -Floor 178 0.067 - 0.3125 0.2455 - 21.4% -Floor 179 0.043 0.112 0.3125 0.2695 0.201 13.8% 35.8%Floor 180 0.082 0.096 0.3125 0.2305 0.217 26.2% 30.7%Floor 181 0.104 0.066 0.3125 0.2085 0.247 33.3% 21.1%Floor 182 0.063 0.039 0.3125 0.2495 0.274 20.2% 12.5%Floor 183 0.084 - 0.3125 0.2285 - 26.9% -Floor 184 0.072 - 0.3125 0.2405 - 23.0% -Floor 185 0.072 0.088 0.3125 0.2405 0.225 23.0% 28.2%Floor 186 0.090 0.110 0.3125 0.2225 0.203 28.8% 35.2%Floor 187 0.105 0.064 0.3125 0.2075 0.249 33.6% 20.5%Floor 188 0.036 - 0.3125 0.2765 - 11.5% -Floor 189 0.095 - 0.3125 0.2175 - 30.4% -Floor 190 0.091 - 0.3125 0.2215 - 29.1% -Floor 191 0.080 - 0.3125 0.2325 - 25.6% -Floor 191A 0.088 - 0.3125 0.2245 - 28.2% -Floor 192 0.059 - 0.3125 0.2535 - 18.9% -Floor 193 0.112 - 0.3125 0.2005 - 35.8% -Floor 194 0.103 - 0.3125 0.2095 - 33.0% -Floor 195 0.030 0.099 0.3125 0.2825 0.214 9.6% 31.7%Floor 196 0.060 - 0.3125 0.2525 - 19.2% -Floor 197 0.112 - 0.3125 0.2005 - 35.8% -Floor 198 0.048 - 0.3125 0.2645 - 15.4% -




LocationPlate

#

Upper End of



Nominal Thickness

(inch)


Pit on Upper End

of Plate (inch)


Pit on Lower End

of Plate (inch)

Upper End of Plate


Lower End of Plate


Pit Depth (inch)

Remaining Plate

Thickness* (inch)

Percentage Loss *

0.014 0.299 4.3%

0.216 0.097 69.1%

0.077 0.235 24.7%0.3125

*

**

When reviewing the loss data the reader should note the permissible minimum tolerance for 5/16 inch plates was 0.010 inch (ASTM-A6). The calculated thickness losses have not been adjusted for thickness tolerances.

On Floor Plate 108 there was 5 inches wide by 11 inches long by 1 inch deep indentation caused by fallen cross member.

Minimum Pit Depth (inch)Maximum Pit Depth (inch)Average Pit Depth (inch)

Nominal (inch)


TABLE 3

File: GPA Fuel Tank 1935 Cost Est.xlsDate: April 5,2004Job No. 01405108By AJD

GPA FUEL TANK 1935 REPAIRSItem Item DescriptionNo. Quantity Unit Unit Cost Cost Unit Cost Cost Unit Cost

1 Repair defective fillet welds on tank bottom 30 LF 4.50 135 65.00 1950 69.50 2,085

2 Weld deep pits in tank bottom plates 200 EA 1.25 250 65.00 13,000 66.25 13,250

3 Install Doubler plates at heavily pitted areas 300 SF 4.50 1,350 65.00 19,500 69.50 20,850

4 Provide new Roof Rafter 36 LF 1.00 36 65.00 2,340 66.00 2,376

5 Weld repair - Tank Roof 3 LF 3.75 11 100.00 300 103.75 311

6 Paint touch-up Tank Exterior 200 SF 3.25 650 4.50 900 7.75 1,550

7 Sandblast and coat tank bottom 31,416 SF 1.75 54,978 3.09 96,981 4.84 151,959

8 Sandblast and coat interior tank shell 30,159 SF 1.75 52,779 2.65 79,801 4.40 132,580

9 Sandblast and coat underside of roof plating, roof 57,841 SF 1.95 112,790 5.65 326,803 7.60 439,593rafters and upper portion of roof support columns

10 Cathodic Protection 1 LS 1.00 48,000 1.00 48,000 96,000 96,000

Leak Detection (two options)11a Intermittent Montoring w/ Portable Sensor 1 LS 1.00 32,500 1.00 32,500 65,000 65,000

11b Continuous Monitoring w/ Permanent Sensors* 1 LS 1.00 62,500 1.00 62,500 125,000 125,000

* Used for Summing Costs TOTAL 985,555

Total Estimated Cost (Rounded) $986,000

forCOST ESTIMATE

CostQuantities Materials Labor Estimated Total Cost

FIGURES

APPENDIX A

APPENDIX B


MINIMUM THICKNESS CALCULATION

For

Bottom Shell Ring

(No As-Built Drawings Available)

Per API 653 “Tank Inspection, Repair, Alteration, and Reconstruction” Section 4.3.3 “Minimum Thickness Calculation for Welded Tank Shell”

SEDGHt )1(6.2

min−

=

Where:

tmin = the minimum acceptable thickness in (in) D = nominal diameter of tank in (ft) H = height from the bottom of the shell course to the maximum

liquid level in (ft) G = highest specific gravity of the contents S = maximum allowable stress in (lbf/in2) use smaller of 0.80Y or 0.429T Y = specified minimum yield strength of the plate;

use 30,000 (lbf/in2) if not known T = minimum tensile strength of the plate; use 55,000 (lbf/in2) if not known E = Original joint efficiency for the tank approx. 1.0 For: D = 200’ H = 46’-6” or 46.50’ G = 1.0 S =(0.8x30,000) = 24,000(lbf/in2) or (0.429x55,000) = 23,595(lbf/in2) E = 1.0

0.1*595,230.1*200*)150.46(*6.2

min−

=t

tmin = 1.00 inches

APPENDIX C

APPENDIX D

View of Piti Channel from Tank 1935 Roof

Tank 1935

Tank 1935

Tank 1935

Defects Located in Shell-to-Bottom Fillet Weld

Defect Located on Bottom Plate Lap Joint Fillet Weld

Typical Pit on Bottom Plate

Floor Sump

Interior Beam/Column Connection at Roof

Interior Column Support Foundation

Center Column Support Connection at Roof

Overflow Drain and Vent

Exterior Shell-to-Bottom Fillet Weld

24-Inch Inlet Pipe and Gate Valves

Access Opening on Tank Shell

Overflow Vent Piping Connection Leak

Roof Area at Stairway Landing

Typical Paint Blister on Roof

Gooseneck Vent

Roof Access Port

Taking Ultrasonic Thickness Measurements on Tank Shell

Tank 1935 Ventilation

Tank 1935 Manhole Entrance

Rafter That Fell From Roof

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Tank 1935 Evaluation - Guam Power Authority

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