orthwest Corrosion Engineering

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Oliver Hood
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1 January 27, 2015 N orthwest Corrosion Engineering Mr. William Davis, P.E. City of Bremerton 3027 Olympus Drive Bremerton, WA Warfield Road, Sedro-Woolley, WA Phone: (360) Fax: (360) SUBJECT: City of Bremerton Reservoir 10 North Mr. Davis, Northwest Corrosion Engineering completed an internal coatings evaluation for the City of Bremerton s Reservoir 10 North. Specific tasks conducted during this investigation included: 1. Evaluation of the general condition of the reservoirs interior coating 2. Coating thickness measurements at representative locations 3. Measuring the depth of any accessible noted pitting 4. Preparation of a report summarizing the results of our field inspection As the reservoir was filled during this evaluation, it was not possible to conduct an inspection of the submerged sidewall surfaces or floor. TEST RESULTS AND ANALYSIS Interior Visual Inspection The interior roof and visible sidewall surfaces were inspected using a raft inserted into the reservoir. The water level was approximately 6-feet below the surface of the roof. The roof has a slight slope towards the center and is supported using a series of I-beams and angle iron members that follow the contour of the roof. There are approximately 36 I-beam supports transitioning from the sidewall to the center of the reservoir. The beams are bolted to steel tabs welded to the reservoir sidewall; the I-beams are not welded to the roof plates. Angle iron members are connected to the beams and are positioned throughout the reservoir roof. A painter s rail transitions around the perimeter of the reservoir and is welded to the sidewalls. A single center column and crows nest assembly are used as a means to support the roof. A steel pipe inlet and half-circle overflow are welded to the sides of the reservoir. There is an interior ladder that extends to the bottom of the reservoir with a galvanized steel safety-climb rail connected to it. There is no visible means of corrosion control in the form of cathodic protection. Page 1 of 6

Roof lap sheets I-beam Angle iron Painters rail Reservoir Interior Interior Inspection The interior coating appears to consist of one or two layers of coal tar epoxy.

2 Roof lap sheets I-beam Angle iron Painters rail Reservoir Interior Interior Inspection The interior coating appears to consist of one or two layers of coal tar epoxy. Dry film thickness measurements recorded on the sidewalls ranged from 9 18 mils while coating thickness measurements on the beams were slightly higher at mils. The coating material can be easily scraped off using a razor knife. An estimated 15-20% of the visible interior coating is missing, exposing the underlying steel to the atmosphere. The roof surfaces are experiencing tuberculation, particularly at the nonseal welded lap joints. Typical tuberculation is the size of a quarter and exists on approximately 1% of the surface roof with a larger accumulation on the I-beams. The coating on the center standpipe is in generally good condition with no visible tuberculation. The painter s rail is experiencing coating losses on the upper and lower edges of the steel, but there was no visible metal deterioration. The fasteners used to support the beams appear to be in good condition with surface corrosion product accumulation. Page 2 of 6

Sidewall and beams Sidewall and beams Interior Corrosion Assessment The visible weld beads on the sidewall sheets are in good condition, there was no noted instances of

General surface corrosion was noted at all coating defect locations.

3 Sidewall and beams Sidewall and beams Interior Corrosion Assessment The visible weld beads on the sidewall sheets are in good condition, there was no noted instances of significant deterioration. In addition, there was no observed pitting greater than 1/16-inches deep on any of the exposed surfaced. General surface corrosion was noted at all coating defect locations. These areas include the edges of beams and angle iron, along the edges of the painter s rail, on the web and flange surfaces of the beams near the center of the reservoir, and at the roof overlap joints. Because the roof plates are not seal welded, crevices are created whereby the non-oxygenated locations within the crevice become anodic to the oxygen-saturated areas adjacent to the crevice. This results in corrosion within the crevice and subsequent build-up of iron oxide. Many of these overlap areas are greater than 0.5-inches which will make it difficult when conducting surface preparation operations. Gaps between roof plates and corrosion product build-up Page 3 of 6

4 The surfaces of the I-beam supports near the center of the reservoir are displaying significantly more coating loss than at other sites. Near complete coating loss on the beams was observed starting from the center of the reservoir and extending out a distance of feet. This has resulted in general surface corrosion at these locations; however there did not appear to be any significant loss of metal as is normally observed in the form of sharp beam edges and pitting damage. There are also large gaps between the top of the supporting equipment (beams and angle iron) and the roof plates. Gaps up to 1.5-inches were noted in many locations with larger gaps likely in unobserved sites. This condition will make surface preparation difficult in areas where the gaps between the beams and roof plates narrows. During our investigation, there was no observed mill scale accumulation on any of the exposed surfaces. However, it is likely that mill scale is present in areas that could not be inspected. As part of any surface preparation prior to the application of a new coating, all mill scale must be removed. Condition of beams near center of reservoir, significant coating loss and general surface corrosion Page 4 of 6

5 Typical condition of reservoir roof and beams Overflow and inlet, minor coating loss and rust staining on edges Page 5 of 6

6 CONCLUSIONS The following conclusions are based upon a visual inspection of the reservoir. 1. The coating on the interior of the 10 North reservoir appears to consist of one or two coats of coal tar epoxy ranging in thickness from 9 25 mils. 2. Approximately 15 20% of the visible surfaces have experienced coating loss. 3. At locations of coating loss, general surface corrosion and rust staining is present. 4. There was no noted deep pitting on the exposed metal. The welds appeared to be in good condition. 5. Larger than normal gaps exist between the roof beams and roof plates. As part of any abrasive blasting operations, angle nozzles are recommended to be used in order to remove as much corrosion product as possible. 6. The condition of the coating below the water surface level is unknown. RECOMMENDATIONS 1. The existing coal tar coating is nearing the end of its useful life. Accelerated coating loss with associated surface corrosion and rust staining can be expected. An additional 3 5 years of useful life can be expected from the existing coating system. 2. When the reservoir is drawn down for coating replacement or for routine maintenance, an inspection of the floor and wall surfaces should be made. 3. A new coating system should include surface preparation to white metal blast standards and the application of a three-coat system consisting of a zinc rich primer followed by an intermediate and topcoat of epoxy. Alternatively, if the use a cathodic protection system is desired, the submerged surfaces could be coated with two layers of epoxy without the application of a zinc primer. All non-submerged surfaces are still recommended to incorporate a zinc primer and two coats of epoxy. We appreciate the opportunity to assist you with this project. If you have any questions or would like any additional information, please do not hesitate to contact our office. Sincerely, Northwest Corrosion Engineering Jeremy Hailey, P.E. NACE Corrosion Specialist #5401 NACE Level 3 Coating Inspector # 5672 Page 6 of 6

SECTION SITE FURNISHINGS FOR CFCRT. 1. American Society for Testing and Materials (ASTM).

SECTION SITE FURNISHINGS FOR CFCRT. 1. American Society for Testing and Materials (ASTM). PART 1 - GENERAL 1.1 SECTION INCLUDES A. Benches. B. Trash receptacles. C. Bike storage. 1.2 REFERENCE STANDARDS A. Including but not limited to: 1. American Society for Testing and Materials (ASTM). 1.3