Bubbler Info - ProjNet BI 10914669.pdf

CENWO-EDD-A 14-22 July 2022

MEMORANDUM THRU CENWO-XXX-X

SUBJECT: Garrison Dam, Spillway Bubbler System Nozzle Inspection and Clean-Out, Missouri River, Riverdale, North Dakota

1. PURPOSE AND SCOPE OF DIVING INSPECTION

The purpose of the inspection was to assess and document the deficiencies of the spillway bubbler system to determine the level of repair work required to bring the system back to an operational state. Based on the assessed conditions, the bubbler system repair scope of work is to be developed and included into the Spillway Approach Dredge and Gate Bubbler/Heater System Restoration contract.

The work performed by the Vicksburg dive team consisted of clearing the sediment surrounding bubbler nozzles using an air inducting device, verifying and video recording of physical conditions of the nozzles and cleanout plugs, and clean-out of the piping system when deemed necessary and able to do so.

2. DIVING OPERATION

The diving work on site was performed on 14th thru 18th July 2022. In general, the daily diving operation involved placing and anchoring the silt curtain to spillway piers to contain the sediment, performing air inducting operation to remove the sediment surrounding the nozzles and attempting to purge the system piping after removal of the cleanout plugs. Daily diving safety checks including audio communications, breathing air level, and on-site supervision during the diving operation were managed by the diving crews. It shall be noted that due to high wind weather conditions beginning 19th July and concerning depths of sediment and buried debris (large rocks and trees), the dive team was unable to continue the diving operation. Therefore, the findings and recommendations stated herein are based on the conditions documented between the gate # 1 and gate #13.

3. SPECIFIC FINDINGS

a. NOZZLE VIDEO RECODING

i. On the first and second day of diving, the divers attempted to video record the physical appearance of nozzles after inducting air into the area to clear the sediment.

ii. The diver was able to video record a few nozzles associated with gate # 1 thru gate

#4 until the turbidity of water became an issue.

iii. No additional attempts after the first and second day were made to video record the nozzles due to poor visibility the diver faced under water.

iv. The divers stated that the current nozzle configurations match the record drawings which do not appear to be designed with endcaps or plugs (see photo 1)

b. SEDIMENT COVERAGE

i. The sediment was not as deep toward gate #1 as compared to the opposite end of the spillway as expected (the actual sediment was about 1ft -2ft deeper than the sonar readings documented by Garrison staff). Near gate #18, there was approximately 6 ft of sediment above the bubbler nozzles.

ii. In general, after removing the sediment using the air inductor, the sediment filled back into the area in a short period of time (It depended on sediment depth at each gate, but usually 1ft of sediment or more settled back above the nozzles where the sediment was removed the previous day and/or within an hour or two after the air inducting in some cases).

iii. In addition to sediment getting deeper towards the plan east side, the debris was larger such as rock and trees were found to be buried under the sediment (gate #12 and #13 where the diving operation stopped). The diver attempted to clear the debris for three (3) hours but was unsuccessful to reach the nozzles.

iv. Due to the safety concerns, weather conditions, and significantly reduced effectiveness of the air inducting operation, the diving operation was not continued past the gate #13.

c. NOZZLE INTEGRITY

i. There have been a few nozzles at each gate and pier with restricted or no flow even after clearing sediment surrounding nozzles.

ii. The nozzles that were not appropriately working seemed to have plugged holes.

iii. The divers attempted to clean out the nozzle holes using welding rod and were able to restore relatively full flow conditions (numerous nozzles plugged back and/or silted back later discharging minimal to no air bubbles).

iv. Predominantly, the debris came out of the piping system and nozzles included sands, coals, and mud. In some cases, what appeared to be rust flakes or built-up scales were also seen, which led the team to conclude some internal piping corrosion is present.

v. The nozzles that had been cleaned and operational in the previous day were found to be plugged again the next day having no or restricted flow.

vi. Attempts were not made to unbolt the nozzle flanges due to concerns of other foreign materials such as coal, sand, and organic debris making its way into the bubbler piping which could have worsen the blockage.

vii. The divers reported that there were no signs of physical damage, corrosion, or zebra mussels on the nozzles and flange bolts.

viii. During the inspection, a nozzle on the east pier of gate #17 was seen with excessive air flow. The diver inducted air into the area and found two loose bolts on the flange that caused the significant air loss thru the ¼ inch gap between the flange and the wall. Bolts were tightened and the leak was mitigated at approximately at 4 pm on 18th July.

d. COMPRESSOR SYSTEM AND PIPING

i. There two air cooled compressors (Gardner Denver) equipped with compressed air filter and dryer (Deltech). No additional air receiver (accumulator tank) was in the building unless the air dryer vessels act as the accumulator.

ii. The air compressors had considerable oil leaks in many joints and seals. These units were manufactured in 1999 which have exceeded a typical useful service life of 10- 15 years.

iii. The main compressed air header piping in the control building is carbon steel and presumably the header piping along the spillway walkway is also carbon steel (not visually verified due to the insulation and jacket materials). Some amount of surface rust was seen on the main header piping exterior.

iv. It appeared that each bubbler system piping that branches off the carbon steel main header is copper including embedded sections.

4. RECOMMENDATIONS

a. Perform high pressure water jetting of each bubbler branch line to clear out the rust flakes, fine layer of silt, sand, and built-up corrosive deposits in the piping. Prior consultation with vendors will be necessary regarding efficacy and feasibility of water jetting operation due to the embedded copper tubing and fitting configurations to prevent eroding transition fittings or damaging concrete.

b. Replace the current nozzles with a modified design that would allow a periodic system purging without the diving operation. This will be accomplished by adjusting the current nozzle design to allow installation of a check valve in the end of the nozzle tip. Such check valves will have adjustable or fixed higher cracking pressure (ex. 50 psi) setting spring loaded poppet to allow the normal bubbler operation at low pressure (20 psi-30 psi) and purging the system piping at higher pressure (above cracking pressure) when necessary. All cleanout plugs also can be replaced with this type of check valves to assist purging the piping system.

See Appendix A for product example.

c. Operate the bubbler systems periodically for a short period of time to keep the sediment or other foreign materials out and away from the nozzle holes (preferably all year long if practical but will need reliable compressor systems to run continuously).

d. Perform borescope inspection of embedded sections of the bubbler piping to identify condition of bubbler system piping. An optical instrument such as flex tubed camera will be used for this type of inspection. Wire brushing the accessible sections of branch lines in attempt to remove internal build up may be required.

e. Consider using the cleanout plugs as a temporary bubbler system when the main nozzle is not operational (The air pressure will need to be significantly reduced for the subject section of piping due to larger opening at each cleanout (1”) or cleanout plugs with hole drilled in center).

f. Consider Installing point of use filters on branch air lines if inspections identify internal air piping corrosion.

5. SUMMARIZED TABLE (NOZZLE CONDITION)

This table presents the nozzle flow conditions observed after the divers attempted to clean the air discharge.

Gate #/Pier # Non-operational Operational Gate 1 and pier 3 3rd from the right All others Gate 2 and pier 4 1st on the right All others Gate 3 and pier 5 N/A All working Gate 4 and pier 6 N/A All working Gate 5 and pier 7 N/A All working Gate 6 and pier 8 N/A All working Gate 7 and pier 9 N/A All working Gate 8 and pier 10 Pier 10 All working Gate 9 and pier 11 Pier 11 All others Gate 10 and pier 12 N/A All working Gate 11 and pier 13 N/A All working Gate 12 and pier 14 N/A N/A Gate 13 and pier 15 N/A N/A

6. PHOTOS

photo 1. Overview of spillway upstream side photo 2. Typical nozzle conditions (no corrosion or physical damage shown) photo from the diver’s video recording photo 3. Air inducting in operation photo 4. 1” Cleanout plug photo 5. 1” Cleanout plug photo 6. 1” Cleanout plug photo 7. Coals floated up during air inducting operation photo 8.Silt curtain between piers containing the sediment photo 9. Control building housing the bubbler system compressors photo 10. Oil leaks around the compressors photo 11. Compressed air dryer vessels and filter behind the unit photo 12. Carbon steel compressed air main piping between the compressors and the dryer photo 13. 1” gate valve (top), pressure gauge, and needle valve (bottom) onc1” compressed air branch line

Appendix A

Adjustable cracking pressure check valve

Product Information

SA.SL.ACV002.E.3366

ADJUSTABLE CHECK VALVE

1/4” & 1/2" NPT

3 – 600 Psig

S E

R

IE

S A

C V

Description Compact one piece body, adjustable check/relief valves are available in Brass or 316 Stainless Steel. Available in 1/4" and 1/2" NPT with a wide selection of seal materials.

Series ACV valves can be ordered factory “preset and locked” in crack pressures up to 600 Psig. All valves are 100% factory tested and available cleaned & packaged for Oxygen service.

Features

• Compact One Piece Body Construction

• Working Pressures to 3000 Psig (206 bar)

• Adjustable Cracking Pressures from 3 to 600 Psig (0.2 bar to 41.3 bar)

• Fully retained O-Ring Seal

• Full Back Pressure Rating

• Factory Presetting Available

• 100% Factory Tested for Leakage, Crack and Reseal

Performance

Technical Data

Cracking Pressure Ranges:

3 to 20 Psig (0.2 to 1.4 bar) 20 to 65 Psig (1.4 to 4.5 bar) 65 to 175 Psig (4.5 to 12.1 bar) 175 to 350 Psig (12.1 to 24.1 bar) 350 to 600 Psig (24.1 to 41.3 bar) Maximum Pressure: 3000 Psig @ 100°F (206 bar @ 40°C) Temperature Rating: -80°F to 450°F (-65°C to 232°C)

(based on seal selection, see ordering information)

Materials of Construction

Component Valve Body Material

Brass Stainless Steel Body, Poppet, Seat

Locking Screw, Adjustment Screw, Pressure Locking Screw

Brass, ASTM B16

316 SS,

ASTM A479

Spring 302 SS, ASTM A313

O-Ring Seal1 Buna-N Viton™ 1 Lubricated with Krytox™

SA.SL.ACV002.E.3366

SERIES ACV

ADJUSTABLE CHECK VALVE

Dimensions

Model Code Connection Inlet & Outlet

Dimensions A Hex Cv

ACV-4P 1/4" Male NPT 1.62” 9/16” 0.35

ACV-4FF 1/4" Female NPT 2.98” 3/4"

ACV-8P 1/2” Male NPT 2.56” 7/8” 1.20

Flow tested in accordance with ISA S75.21 with air. Restrictions in the inlet or outlet piping may reduce flow. NPT Threads per ASME B1.20.1.

Ordering Information

PROPER COMPONENT SELECTION – When specifying a component, the total system design must be considered to ensure safe and trouble-free performance.

Intended component function, materials compatibility, pressure ratings, installation, environment and maintenance are the responsibility of the system designer.

www.generant.com

1865 Route 23 South PO Box 768 Butler, New Jersey 07405 973.838.6500 Fax 973.838.4888

Following pictures are spillway gates. Bubbler nozzles are below the 2nd construction joint near the ground