Exhibit C - 2018 Inspection Report.pdf

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Technical Memorandum Technical Memorandum

To: Kurt Conger Northern Wasco County PUD

Project: McNary Turbine Maintenance

From: Grant Horeczy, SE/PE McMillen Jacobs Associates cc: Kyle DeSomber, Project Manager McMillen Jacobs Associates

Date: January 18, 2018 Job No.: 17-087

Subject: Baffle Structure and Draft Tube Gate Inspection Report

1.0 Introduction

The Northern Wasco County People’s Utility District (NWCPUD) retained McMillen Jacobs Associates (McMillen Jacobs) to conduct an inspection of the fish bypass and diffuser supply system at the McNary Dam Fishway. The inspection was performed to assess the condition of a baffle element that had moved from its held position, in a manner that was suggestive of a support failure. McMillen Jacobs personnel performed site visits during January, 2018, and the results of the visual inspection are included in this memorandum. This inspection report provides initial recommendations for the repair and strengthening of the damaged elements. The inspection of a draft tube gate was also performed in advance of a dewatering and maintenance plan during next year.

2.0 Baffle Structure

2.1 Site Inspection

The baffle structure was initially inspected by Grant Horeczy, S.E. and Joe Carson, M.E., of McMillen Jacobs on the morning of January 07, 2018. A subsequent, closer inspection was performed by Mr.

Horeczy on the morning of January 11, 2018. NWCPUD personnel were onsite assisting with the inspections. Conditions were overcast for both inspections and the structure was visible throughout the inspection periods. The inspection was limited to the baffle elements closest to the top of the vault, with elements at lower elevations unobservable. Water was not flowing into the structure during the time of the inspection.

2.2 Structure Description and Extent of Inspection

Baffles are used in the bypass structure to dissipate energy from flowing water. These baffles are located within a 20 ft x 30 ft wide rectangular concrete chamber, hereby described as a concrete vault. Water flows into the structure from South to North, at a high velocity and the baffling elements are used to slow the velocity of the water.

The baffle assembly comprises several elements, including two large welded steel box structures spanning in the transverse direction of the concrete vault (North-South). The box structures have an open top and

NWCPUD Baffle System and Gate – Site Inspection Inspection Report

Rev. No. 0/Jan 2018 2 McMillen Jacobs Associates bottom, allowing water to flow through the system as it dissipates kinetic energy. Within these welded box structures, a series of cylindrical elements are bolted to the inside face of the steel boxes, creating further obstruction to water flow and greater energy dissipation. In addition, long half-cylindrical steel members (baffle beams) are connected to the concrete walls of the vault to obstruct water flow along the East and West faces of the vault. As part of this assembly, long vertical steel pipes are also in place to help degas the turbulent water. The top of the baffle beams are at elevation 321.0, approximately 27 feet below the top of the concrete vault.

A large steel pipe is beneath each of the welded box structures. This structure was excluded from the inspection because it was difficult to observe, and because the portion of the structure that was observable did not show any signs of degradation or connection points that could have been weaker than the main pipe section.

2.3 Evaluation

2.3.1 Member Structural Performance

The baffle structures appear to be well-sized for the hydrodynamic loads applied, showing no permanent deformation or fractures. This includes the baffle beam that had had a catastrophic failure to its support, described in the following sections.

2.3.2 Coating System

The steel baffle elements are painted with an ivory color paint. Due to the hydraulic application of the member, the paint is anticipated to be either an epoxy or a polyurethane product. If it was applied with more than one coat, the paint was not applied in an alternating color scheme to indicate paint degradation (ie: different color coats).

The paint ranges from being relatively intact to being fully removed, as evidenced by the quantity of rust and the onset of early pitting. The amount of rusting is highly variable. Depending on the frequency of maintenance, the baffle system may be a good candidate for a thorough re-establishing of a paint system during the upcoming work planned.

2.3.3 Connections

Steel elements in the baffle assembly are bolted together. It has been reported to the inspection team that the bolts used to be carbon steel bolts, but that these bolts were replaced in the past with stainless steel bolts due to rusting out and catastrophic failure of the carbon bolts. Accordingly, during the inspection, no carbon steel bolts were noticed on the structure, and that all bolts were stainless steel. In addition, stainless threaded rods were used to connect those elements that are anchored to the concrete walls.

The South end of the half-cylindrical baffle element (baffle beam) connected to the East concrete wall was sheared completely from the face of the concrete wall. This event had the baffle beam collapse downward on one end until it landed on a lower baffle element, twisting one bolt on the remaining Bracket Support. At the time of the second inspection, the twisted bolt was replaced with a new bolt.

The Bracket Support that fell was recovered from a lower baffle element during the time the install of the

Rev. No. 0/Jan 2018 3 McMillen Jacobs Associates scaffolding and was available for inspection. The Brackets Supports are L 8 x 8 x 1 brackets, 1 ft 4 in. in length, with two connections going into the concrete wall. Unexpectedly, the fallen bracket appeared to have a better coating condition than the bracket that was still attached to the concrete wall.

Other than the support ledger issues on the East-wall, the bolted connections used to connect steel baffling elements inside the welded boxes were visually inspected. It was noticed that several bolt holes did not have bolts in place (missing bolts) and it is possible that these areas had a catastrophic failure of bolts similar to the failure of the anchor rods at the concrete wall. If so, the bolts would have failed by shear rupture driven by fatigue.

Another failure mode possibility is that the bolts did not rupture, but became loose and fell off the structure due to the vibrations imposed by the hydrodynamic load. However, it is noted that none of the surviving bolts showed any misalignment or distress or loosening.

It is possible that all of the “loose bolts” failed and all of the other bolts will survive indefinitely if the same hydrodynamic loading regime is applied. However, if the bolts failed in shear or fatigue instead, it is unknown if any of the existing bolts are near failure. Some of these bolts may be near failure even though they do not show any visible indication of being weakened or compromised.

2.4 Recommendations

It is understood that work will be performed to reattach the loose end of the collapsed baffle beam to the South concrete wall, re-establishing the connection with one similar to its original design and that a new design could be implemented in the following year.

2.4.1 Recoating

Annual monitoring of the paint system is recommended, with localized repair efforts to the coating system as necessary. The existing coating system is anticipated to require a complete recoat effort in the 5 to 10 year time frame.

In the past, the system that would be best suited for the baffles would be limited to a self-priming epoxy coat system, formulated for exterior and underwater use. The selection of a coat system would evaluate the advantages of polyamide epoxies with polyurethanes and polyamine epoxy systems to determine the optimal coating system. While epoxies are well-suited for hydraulic structures, epoxies that are exposed to ultraviolet rays for an extended period of time can exhibit “chalking”, or discoloring.

With the introduction of polysiloxane epoxies, it is possible to specify an epoxy product that will have ultraviolet protection superior to traditional epoxies. However, if an epoxy is adopted, it may require stiffening of the members since large vibrations can damage epoxy coating systems.

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2.4.2 Structural

2.4.2.1 Inspection of Uninspected (Lower) Baffles

The baffle beam is believed to have failed by a shear failure of threaded rods connecting the gusseted Bracket Support Ledger to the concrete wall. This occurred at the highest elevation of the baffle beams and failure at this location may be related to the baffle resisting the highest level of energy dissipation, with lower levels expected to have some “shelter” provided by upstream baffle elements. However, since the condition of the lower baffle elements are unknown, it is recommended to confirm the condition of lower baffling elements.

2.4.2.2 Inspection of Uninspected Uppermost Baffles

At the top baffle elevation, there are four similar connections. Since the system is symmetrical with respect to the incoming water, there is no geometric or hydraulic basis to conclude that the connection on the West-side baffle beam is not near failure. It is recommended to evaluate and potentially rehabilitate all similar baffle beams at the top elevation.

2.4.2.3 Install Intermediate Supports

It is recommended to connect each baffle beam at two intermediate locations. When used in conjunction with the end supports, the additional baffle beam supports will create a more rigid overall response to hydrodynamic loading, which should reduce the likelihood of resonance within the system. Additional supports would also spread the bearing loads to other connections, reducing the magnitude of loads any single connection would see, while providing redundancy to the system. It is also recommended to use four-bolt connections instead of the existing two-bolt connections to eliminate prying that could occur if a bracket is subject to pushing against the wall at the toe of the bracket angle.

2.4.2.4 Install Stronger Bolts

The material used for the existing bolts is not known, and the existing bolt grade should be verified if possible. An enhanced bolt material is expected to decrease the number of bolts failing during a given time period. Unless specified, bolt suppliers will normally supply for “316 SS bolts” a A193 B8 Class 1 material bolt, which has an ultimate tensile strength of 75 ksi. It is recommended to replace the missing bolts with ASTM A193 Grade 8M Class 2 material. This will provide a high strength material, which has an ultimate tensile strength of 110,000 psi for the diameter in discussion (a 47 percent increase in tensile strength). An alternative to adopting a stronger material, is to replace the bolts with in-kind material, acknowledging that a periodic effort to replace these connectors could be necessary.

2.4.2.5 Double-Nut Connections

It is also recommended to double-nut all bolts, as an effort to reduce the possibility of bolts becoming loose and rattling off under the hydrodynamic loads. If existing bolts are kept, and they do not have enough thread length to allow for a second nut, it may be advantageous to replace these bolts with new bolts that are longer.

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3.0 Draft Tube Gate

3.1 Introduction

The draft tube gate is in an area infrequently dewatered and the gate structure had not been inspected in over 10 years. McMillen Jacobs personnel, assisted by NWCPUD, inspected the gate structure on the morning of January 07, 2018. The sections below provide the observations and conclusions of that inspection.

3.2 Site Inspection

The draft tube gate structure was inspected by Grant Horeczy, S.E. and Joe Carson, M.E., of McMillen Jacobs on the morning of January 07, 2018. NWCPUD personnel were onsite assisting with the inspection. The location of the structure was sheltered from the elements. The gate was in its lowered position during the time of the inspection and was dry on both faces.

The inspection was limited by the access available during the window of inspection which did not allow for an up-close inspection of the downstream face of the gate. The upstream face of the gate was inspected up-close.

3.3 Structure Description

The gate is a steel gate manufactured by Rodney Hunt Company and described by drawings provided by NWCPUD, dated 05/1993 through to 02/1996. Conceptually, the gate is a smooth steel plate stiffened by horizontal wide-flange beam members along the downstream face of the gate. The vertical ends of the gate are similarly stiffened and made with rollers to lift and lower along guides at the side. When in its lifted position, the gate is held adjacent to a vertical face, keeping the upstream face clear of the water flow. According to the gate drawings, the gate is 13.5 ft tall, and will cover an opening that is 13.0 ft tall.

The width of the gate is approximately 20 ft wide and uses 7 wide-flange supporting elements to resist the hydrostatic force.

3.4 Evaluation

3.4.1 Downstream Face

An up-close inspection of the downstream face of the gate was not possible during the time of the inspection. However, with the use of binoculars the general characteristics of the gate was determined through the experience of the inspection team. The general quality of the welds and the surface with respect to damage and deterioration was assessed to the level discussed in this report.

There was no damage or permanent deformation observed indicative of a mechanically-imposed distress or overloading. Welds that were visible, had a smooth profile consistent with a quality of a well-performed original weld. Although the inspection effort was limited, highly visible weld defects, like undercutting or splatter, were not observed. The surface of the gate appeared to have some discoloration and texture that suggested that coating on the steel surfaces may have failed. However, it was not possible to get an in-depth assessment of the surface condition, because the surfaces observed were also likely dirty at the same time as they were exhibiting rust.

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3.4.2 Upstream Face

The upstream face was accessible through the draft tube. From that direction, in the lowered position, only the smooth outer face of the gate was observable. The bottom lip of the gate was not observable as it was sunken below the top of the draft tube lower surface. The surface of the gate was dirty, but could be inspected by wiping the mud away by hand and observing the surface.

The gate appeared to have an epoxy surface paint coating, typical of painted underwater hydraulic steel structures. The surface was smooth, unlike the pitted surfaces of the steel-lined draft tube (which were either uncoated, or had their coating removed over time).

3.5 Observations and Recommendations

3.5.1 Observations

During the inspection, a recent project was discussed which had the inspected structure assessed per a series of quality levels, ranging from “Level 1” (best condition) to “Level 5” (poorest condition). This project assessed the structural condition of stop logs that were over 60 years old and left in an exposed environment when not placed in water. Examples of each condition are provided in the Appendix to help illustrate the condition associated with each level.

Condition levels are presented in Table 1. These condition levels are provided as an aid for discussing the conditions of the observed gate.

Table 1. Condition Levels

Condition Level Description

1 The structural elements were in very good condition, and were expected to perform satisfactorily for an extended period of time, approximately 30 years or longer, without any substantial repair effort required. These areas would need to be observed and maintained as required, but the maintenance is anticipated to fall under the regime of a typical maintenance program and not require major overhauls of the system.

2 The structural elements were similar to Level 1, but had an aspect of their condition that may be a candidate for a relatively small repair effort to achieve Level 1. This was typically seen as an re-establishment of the coating system to its start-of-service level, to prevent any member from dropping to a Level 3 condition.

3 With extensive use expected over the immediate 10 years, these elements were expected to achieve 10 years of performance, but be in a near-failed condition at the end of the 10 years. The risks associated with failure would mandate that any element in a Level 3 condition would require more frequent inspections, and have it understood that it may deteriorate quicker than expected which could create maintenance or operational costs during the 10 year time frame. Replacement or re-construction was expected for all elements at Level 3 if these were to achieve 30 years of life.

4 An intermediate level between Level 3 and 5, which suggested that their condition would incur operational costs during the 10 year time frame.

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Condition Level Description

5 Elements that required replacement because they were damaged to the degree of exhibiting failure or having little reasonable expectation of survival during any significant time period of use.

Applying these concepts to the gate, the gate is consistent with a Level 2 condition.

None of the structure had the appearance of a structure that was broken or deforming permanently. While the specific condition of the surface coating system is unknown, large pits associated with pronounced rusting were not observed. It is expected that if these were present they would have produced shadows on the surface even if the structure was muddy.

3.5.2 Recommendations

3.5.2.1 Further Inspection

While the defects that defined condition levels 3 or worse were often the type that could be visibly identified, the inspection was not able to look at all locations and at close-proximity. The inspection performed could only see damage that would have made the clear case for a replacement or rehabilitation of the structure or its coating. Due to the general quality of the welds seen, it is anticipated that a close-up inspection would not trigger the need for non-destructive testing, but an authoritative dismissal on the need for non-destructive testing is not possible to do. This is because the welds at the ends of the structure were not visible, and that cracks in dry structures can only be observed on cleaned surfaces.

3.6 Conclusions

Nothing observed during the inspection would prevent the use of the gate for another year. With a future outage planned for next year, observations collected in this inspection may be useful in developing a plan for closer inspection of the gate during that time period. It is recommended to clean the gate and conduct a close inspection of the welds and members at that time.

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Photos

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Fig 1 – Baffle System, looking East from top of Concrete Vault

Fig 2 – Baffle System, looking Down towards East. Damaged baffle beam in view.

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Fig 3 – Baffle System, looking Down, towards West. Undamaged baffle beam in view.

Fig. 4 – Baffle System, looking Down (East). Damaged baffle beam in view. Note variable rusting.

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Fig. 5 – Baffle System and vertical Vent Pipes (Looking South-East).

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Fig. 6 – Baffle beam at North-West corner. Surviving support of damaged baffle beam end connections.

Fig. 7 – Baffle Beam connection – top view. Bolted connection between Support Bracket and Top Angle.

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Fig. 8 – Baffle Beam connection – Side View. Top flange of Support Bracket in view.

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Fig. 9 – Baffle Beam, looking South-East. Beam is angled due to failure of far end support.

Fig. 10 – Baffle Beam connection – Side View. Bottom Bracket in view. Note failed coating system.

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Fig. 11 – Recovered Support Bracket from damaged end of east Baffle Beam.

Fig. 12 – Concrete face at failed support of Baffle Beam. Note sheared bolts in wall.

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Fig. 13 – Sheared bolts at Concrete Wall.

Fig. 14 – Baffle Structure, view of side and top.

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Fig. 15 – Baffle Structure, side view, looking West. Note missing bolts.

Fig. 16 – Baffle Structure, looking West.

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Fig. 17 – Baffle Structure, looking West. Location with bolts in-place.

Fig. 18 – Baffle Structure, Interior Baffle Pipe connection to Box Structure.

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Fig. 19 – Vertical Vent Pipe.

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Fig. 20 – Vertical Vent Pipe connection to Concrete Wall.

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Fig. 21 – Bypass Gate, downstream face.

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Fig. 22 – Bypass Gate, downstream face.

Fig. 23 – Bypass Gate, Downstream Face. Stiffener flanges.

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Fig. 24 – Gate, Downstream Face, top of Gate.

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Appendix A

Examples of Condition Levels

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Fig. A1 – Example of Condition Level 1. Condition Levels are based on the criticality of the member/member element reviewed, in addition to the condition of the element.

Fig. A2 – Example of Condition Level 2 (coating system failure in progress).

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Fig. A3 – Example of Condition Level 3 (New rusting combined with previous pitting).

Fig. A4 – Example of Condition Level 4 (Extensive corrosion on a bearing point).

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Fig. A5 – Example of Condition Level 5 (Member is heavily corroded and deformed).

3.6 Conclusions