Prior_Report_-_West_Tank_-_Redacted_0001.pdf

West Tank

Report No. 14077-FOR-02-1

Prepared For:

National Park Service 1849 C Street NW

Washington, DC 20240

9/25/2019

STATEMENT OF LIMITATION

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

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

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

Report Prepared by:

Report Reviewed by: Technical Director NACE CIP Level 3 #050

TABLE OF CONTENTS

INTRODUCTION

APPLICABLE STANDARDS

EXECUTIVE SUMMARY

OBSERVATIONS

RECOMMENDATIONS

APPENDIX I

Photographs

GLOSSARY OF TERMS

National Park Service West Tank 14077-FOR-02-1 1

INTRODUCTION

On September 25, 2019 CorrTech representatives, performed a corrosion and structural assessment of the exterior and interior of a drinking water storage tank for National Park Service. The inspection was conducted to establish the current condition of the tank's coatings and steel/concrete substrate. The tank inspected included:

110,000 Gallon West Fusion Tank

For applicable standards used in this inspection, please see below.

The interior of the reservoir was inspected with the TankRover remotely operated vehicle, while full. The TankRover is the only piece of equipment like it in the United States and was developed by CorrTech. By using the TankRover the interior of the tank was inspected with no special preparation, confined space entry, no additional disinfection and no downtime.

The TankRover is equipped with a surface-cleaning tool used to remove loose rust or debris in order to view the potential metal loss under the coating. The unit has high-powered thrusters, which are used to maneuver throughout the tank and are used to wash away bottom sediment for observations. Video is recorded with audio narration on site with digital stills captured for the report.

The TankRover and all tether were prepared for the inspection by disinfecting equipment with a 200 ppm chlorine spray in accordance with AWWA C652-11.

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

The objectives of the assessment were to:

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

2. Assess condition of any protective coatings present

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

4. Review sanitary protection equipment

5. Provide recommendations for rehabilitation.

APPLICABLE STANDARDS

AWWA C652, AWWA Standard for Disinfection of Water-Storage Facilities AWWA D103, AWWA Standard for Factory Bolted Steel Tanks for Water Storage AWWA D101, AWWA Standard for Inspection of Finished Water Storage Tanks AWWA M42, AWWA Tank Guidance Manual, Steel Water Storage Tanks

National Park Service West Tank 14077-FOR-02-1 2

EXECUTIVE SUMMARY

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

Active corrosion is beginning to form on plate edges and under some bolt caps. Installation of a sacrificial cathodic protection system would prevent metal loss on the submerged steel and preserve the life of the existing coating.

Based on water industry vulnerability assessments tank ladders should be no closer than 16-ft above grade and should be fitted with a locking guard. Installing an 8-ft ladder guard is advised for security to the tank. The roof hatch cover should also be fitted with a padlock.

A safety climb system should be installed on any ladder that is 20-ft long or more. For new fixed ladders erected on or after November 19, 2018, the employer must equip the ladder with a ladder safety or personal fall arrest system (1910.28(b)(9)(i)(B)). Installing a cable type safety climb system will keep your tank current with OSHA standards and the device is less tiring to use than a notch railed type device.

Tank floor sediment was removed as part of this inspection.

Tank should be re-inspected in 2024.

National Park Service West Tank 14077-FOR-02-1 3

Tank Data

TANK DATA FOR West Tank

Site Information Fencing In Place:

Yes Locks on Gates: Yes

Address: Park Rd, Gustavus AK Vault Lock in Place: N/A

Tank Information Tank Name: West Tank Tank Diameter: 25-ft

Tank Height: 29-ft Tank Capacity:

110,000 Gallons

Previous Cleaning Date: 2014

Previous Inspect. Date: 2014 Previous Coating Application: N/A

Foundation Height: 0-in - 6-in Adequate Drainage:

NO Chime Plate Size: N/A

# of Anchors: 16 Anchor Bolt Diameter: 1.25 Chair Thickness .75-in

Anchor Chair Dimensions: 7-in x 4-in

Shell Manhole # of Manholes 1 Diameter: 32-in

Ladder Height from Ground: 6-ft Safety Cage: YES

Anti-Climb Lock : N/A Climbing Safety System Style: N/A

Rung to Rung Dim: 11-in Distance from Shell: 7-in Width: 19-in

Overflow Diameter: UNK Air Gap UNK Overflow Protection UNK

Screen Condition: UNK Screen Type:

UNK Splash Pad UNK

Roof Hatch Dimensions: 24-in Sanitary Neck 2-in

# of Hatches: 1 Hatch Cover Overlap

1-in Lock No

Roof Vent Style: Mushroom Diameter: 18-in

Cap to Roof Distance:

3-in Screen Condition:

Intact Type: Fine

Roof Handrail Hts Top Rail: 44-in Mid Rail: 22-in Toe Kick Plate:

4-in

Interior Sediment Depth: 1/8-in to pile of 1-in Sediment Coverage: Evenly dispersed

Inlet/Outlet Pipe: Separate Sediment Ring:

Yes

Interior Ladder Climbing Safety System: No Style: N/A

Columns: NO Column Number: N/A Interior Column Style

N/A

National Park Service West Tank 14077-FOR-02-1 4

OBSERVATIONS

Photos provided in the report were created from a digital camera and interior pictures were captured in digital format from the interior video. The interior images are as clear as our printed technology will allow. The copies in the report provide a reference for our comments. Keep in mind that for underwater video snaps, the video provides the greatest detail and should be viewed as part of the report.

Narration on the video is done in the field and some of the comments may be different than the written report.

INTERIOR

Roof Structure

Roof is a bolted fused glass structure with external galvanized rafters. No structural deficiencies were noted.

Roof Coating

No corrosion or mechanical damage was noted on the glass fused plates. Corrosion was noted on a few small spots of the plate edges where caulking has shrunk back or was delaminated.

Shell Coating

Shell plates are in good condition; no corrosion was noted on the plates. Mild sediment staining was seen on the shell. Corrosion has formed around bolt heads and plate edges.

Columns

No columns are installed on the interior of the tank.

Floor Structure

No structural deficiencies were noted on the floor of the tank. Nut caps are missing on several floor bolts.

Sediment

Sediment was evenly spread across the floor with a depth of approximately 1/8th of an inch with slightly deep piles in the center 1-in deep.

Floor Coating

Floor coating is intact, corrosion was noted on several floor bolts.

Piping

A interior overflow pipe runs from above the fluctuation zone through the floor of the tank.

National Park Service West Tank 14077-FOR-02-1 5

Damage was noted on the brackets holding it to the shell. Damage is likely due to ice impact.

The tank has a raised inlet pipe extending approximately halfway up the shell. The outlet pipe has a sediment ring installed and there is also a drain located on the floor.

EXTERIOR

Foundation

No major cracking or spalls were noted on the foundation of the tank. The chime is recessed into the foundation allowing water to pool. The anchor bolts are not fully engaged and flush to the chair tops.

Manholes

The manhole does not show any signs of leaking. Minor corrosion was noted around the edge of the manhole.

Ladder

Ladder is in good condition. No anti-climb or safety climb is installed on the tank.

Overflow

The overflow is internal; the discharge area could not be located by the utility personnel.

Shell Structure

Shell is in good condition. None of the nut caps are left on the shell of the tank or the roof.

Caulking is weathering leaving some exposed edges on the plate

Shell Coating

Minor bio-staining was noted on the shell of the tank. The tank is fused glass so no chalking and no mechanical damage was noted.

Roof Hatch

The roof hatch is in good condition with tight gasket seal. The hatch is not locked.

Roof Vent

Vent is in good condition and has coarse and fine mesh screen installed.

Hand Rails

An upper shell balcony is installed on the tank, railings appear to be in good condition.

Roof Structure

Roof structure is in good condition. External rafters look to be in good condition, no corrosion or structural damage was noted

National Park Service West Tank 14077-FOR-02-1 6

Roof Coating

Roof coating is in good condition. Minor bio-staining was noted and debris from nearby trees.

Caulking on the roof seams is weathering exposing edges of the plates in some areas.

RECOMMENDATIONS

Sacrificial Cathodic Protection Installation of a sacrificial cathodic protection system would prevent metal loss on the submerged steel and preserve the life of the existing coating. Cathodic protection system will not protect the above water and roof surfaces of the tank. Generally this type of system involves the use of high purity magnesium anodes properly distributed to provide corrosion protection levels to all surfaces. Anode systems can be designed to last 5-15 years. Applicable Standard:

• AWWA Standard D106-Newest Sacrificial Anode Cathodic Protection Systems

Locking Ladder Guard Based on water industry vulnerability assessments tank ladders should be no closer than 16-ft above grade and should be fitted with a locking guard. Installing an 8-ft ladder guard is advised for security to the tank. The most vulnerable location on the tank for vandalism is the roof.

Unwanted access to the roof can be prevented by installing a ladder guard.

Ladder Safety Climb A safety climb system should be installed on any ladder that is 20-ft long or more. For new fixed ladders erected on or after November 19, 2018, the employer must equip the ladder with a ladder safety or personal fall arrest system (1910.28(b)(9)(i)(B)). Installing a cable type safety climb system will keep your tank current with OSHA standards and the device is less tiring to use than a notch railed type device. It is not recommended to use these devices on internal underwater ladders. Underwater galvanic corrosion is caused between the cable and tank making the safety device unsafe after a few years.

Tank should be re-inspected in 2024.

Appendix I: Photographs

01 Overview of the tank

02 Overview of the tank

03 Shell ladder with safety cage and balcony system

04 Lower shell manhole

05 Foundation and tank shell

06 Missing nut caps and bio staining on tank

07 Anchor system with loose nuts

08 Caulked Seams in good condition

09 Tank information plate

10 Roof access hatch

11 Roof vent

12 Exterior support structures

13 Intact fine mesh screen on the roof vent

14 Shell ladder to platform transition

15 Interior roof and shell with the vent opening

16 Interior roof with the central plate

17 Interior overflow pipe

00:45 - Interior roof and shell

1:44 - Interior overflow pipe and the roof access hatch

2:13 - Interior central roof plate

3:35 - Roof vent opening and floating nut cap

5:12 - Bent bracket holding the overflow pipe

5:49 - Corrosion forming on bolt heads

7:58 - Raised inlet pipe

9:32 - Corrosion forming on bolt heads

11:03 - Interior view of the lower shell manhole

11:44 - Pipes entering through the floor of the tank

12:08 - Raised inlet pipe and outlet pipe with a sediment ring installed

12:16 - Drain pipe and raised overflow pipe

12:45 - Corrosion on bolt heads

15:15 - Sediment layer prior to cleaning

Cleaning the sediment off the floor

Sediment prior to cleaning

GLOSSARY OF TERMS FOR STEEL/CONCRETE TANKS

Adhesion- State in which two surfaces are held together by interfacial forces which may consist off valence forces or interlocking action or both

Aggregate- Granular material, such as sand, gravel, crushed stone, crushed hydraulic-cement concrete, or iron blast-furnace slag used with a hydraulic cementing medium to produce either concrete or mortar.

Bugholes- Small regular or irregular cavities, usually not exceeding 15 mm in diameter, resulting from entrapment of air bubbles in the surface of formed concrete during placement and compaction.

Cathodic Protection - The use of a sacrificial metal or energized substance to polarize the structures surfaces and prevents corrosion.

Chalking - The degradation of a paint binders when exposed to ultra-violet light which creates a loose residue on the surface.

Chemical Attack- Decomposition of a coating or concrete due to the action of a chemical.

Chime- Portion of tank floor plate that extends outside the tank shell and rests on top of the foundation.

Contraction Joint- Formed, sawed, or tooled groove in a concrete structure to create a weakened plane and regulate the location of cracking resulting

Corrosion Cell - A concentrated localized site of accelerated corrosion that creates pitting.

Disbondment- The loss of adhesion between a coating and the substrate.

Dry Film Thickness - Total thickness of a paint film when completely cured.

Efflorescence- A white crystalline or powdery deposit on the surface of concrete. Efflorescence results from leaching of lime or calcium hydroxide out of a permeable concrete mass over time by water, followed by reaction with carbon dioxide and acidic pollutants.

Finish- The texture of a concrete surface after compaction and finishing operations have been performed.

Finial Vent - The central roof vent on top of a water tank.

Grout- A plastic mixture of cementitious materials and water used as a filler for cracks, or other void spaces, in concrete surfaces to be coated.

Holiday - A hole or void in a protective coating that may be invisible to the unaided eye that extends to the substrate.

Honey Comb- Voids left in concrete due to failure of the mortar to effectively fill the spaces among coarse aggregate particles.

Hydraulic, Hydrostatic Pressure- A force exerted on the concrete/coating interface due to the level of the ground water.

Isolation Joint- A separation between adjoining parts of a concrete structure

Joint Sealant- Compressible material used to exclude water and solid foreign materials from joints.

Lap Joint Seam- Overlapping seam between roof plates that is open and un-welded on the interior.

Laitance- A thin, weak brittle layer of cement and aggregate fines on a concrete surface. The amount of laitance is influenced by the degree of working or the amount of water in the concrete.

Lead Abatement - The removal of a lead bearing paint system.

Lead Encapsulation - The covering over of a lead based paint by applying a compatible topcoat.

Osmotic Blister - Raised coating area created by build up of fluid under the coating. Fluid moves through coating in response to water/solvent concentrations between coating and tank water.

Osmotic Pressure- A force exerted on the concrete /coating interface through the capillaries in the concrete due to a moisture differential across the coating.

Overflow Weir Box- internal or external box that captures water above the operating height of the tank and directs it to an overflow pipe.

Pack Rust/Crevice Corrosion- Advanced form of steel corrosion that forms visible layers of oxidized steel swollen larger than the original steel plate thickness, usually found between steel plates or surfaces.

Pinholes- Film defect characterized by small pore-like flaws in a coating which extend entirely through the applied film and have the general appearance of pinpricks, fine holes, or voids when viewed by reflected light.

Plastic Cracking or Shrinkage- Cracking that occurs in the surface of fresh concrete soon after it is placed and while it is still plastic, Porosity- The ratio usually expressed as a percentage, of the volume of voids in a material to the total volume of the material, including the voids.

Reflective Cracking-Cracking that develops in a coating directly over a dynamic crack in concrete.

Rigging plug- Thread steel nipple welded to a tank roof for the purposes of rigging painting cables. Usually sealed with a threaded plug when no in use.

ROV - Remotely operated vehicle, underwater inspection device "TankRover" by CorrTech

Screen Mesh- Number of openings per linear inch of screen.

Silt - Material that accumulates in the bottom of a water tank originating from treatment by products, raw water particles and distribution system debris.

Silt Stop- Solid cylinder installed on a floor inlet or outlet pipe to extend the pipe above the floor. Pipe prevents floor sediment from being stirred up or sucked out of the tank during flow.

Static Cracks- A crack in the concrete surface whose width does not change.

GLOSSARY OF TERMS FOR STEEL/CONCRETE TANKS

Stich or Skip Weld- Method of welding two pieces of steel together with intermittent short sections of weld bead.

Leaves open lap joints along the unwelded sections.

Tubercle - Domed shaped buildup of corrosion products over an active corrosion site. Promotes metal loss through pitting due to differential oxygen concentrations.

Ultrasonic Measurement - The use of high frequency sound waves passed through a material to measure the time required to return. The time required to pass through the material is correlated to the speed of sound in the substrate to yield an actual thickness at a specific location.

Vapor Barrier- Waterproof membrane placed under concrete floor slabs that are placed on grade.