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HomeMy WebLinkAboutWTR2702210_1Of;%t na` 1 (% WT(Z 22 -UUU'), Chicago Bridge & Iron Technical Services Company 601 W. 143rd Street Plainfield, Illinois 60544-8929 November 8 1996 rr•: ; �, Mailing Address: P. O. Box 9 Cngi nE e,rj ig Wit.. 1 Plainfield, Illinois 60544 0009 815 439 3100 The City of Renton FAX: 815 439 3130 Dept. of Planning/Building/Public Works Fourth Floor 200 Mill Avenue South Attn.: Mr. Tom Malphrus Re: Elevated Water Tank Inspection CBI Contract 961623 750,000 Gallon Spheroidal Elevated Water Storage Tank Original CBI Contract 8-0381 Attached please find one copy of the inspection report prepared by Mr. Terry S. Grill of our Plainfield, Illinois office. In general, the report indicates that the tank is in good condition. However, the inspector found general corrosion in the form of pitting through out the interior wetted surfaces and moderate corrosion was found in the hip course (#4 Plates) where the water line appears to fluctuate. We feel that this corrosion is not detrimental to the tank, but actions must be taken to arrest any further corrosion. Activating a Cathodic Protection System, and close monitoring of the paint system by a professional service are recommended means to keep the corrosion in check. However the paint system cannot replace the original metal as part of the structural membrane. Therefore if the monitoring reports that corrosion is progressing, the structural integrity of the tank could be in jeopardy and be detrimental to the life of the structure. Hence it is important that the new paint system be maintained and not be allowed to remain in service beyond its recommended life span. Below is a summary of the report and recommendations: Foundation The surface of the foundation piers were found to be in good condition. However material should be applied to prevent further cracking of the grout and corrosion to the metal. Also keep the top of the piers clear of debris, grass and weed overgrowth, and built-up of dirt. The top of piers should be a minimum of 6" above grade as recommended by AWWA. In Chicago Bridge & Iron Technical Services Company Tank Exterior The paint system on the exterior is in good condition on the riser and tank bottom. However isolated spots on the shell have cracking and peeling and the roof also shows signs of weathering. Some minor rust was seen on the tower rods and balcony, and the anchor bolts at the base plate intersection are rusting. "Touch-up" painting should be applied to areas like the anchor bolts and balcony soon. Since the exterior system as a whole is starting to break down, a full repainting should be scheduled for the near future. Tank Interior Wet The paint on the roof is in good condition. Only small amounts of rust was seen on the painters angles and lapped seams. The hip course (#4 plates) and equator course (#3 plates) have general corrosion all over and moderate corrosion in localized pitted areas. The moderate corrosion is familiar on elevated tanks and was found locally in elongated vertical strips up to 3/4" wide x 6' long. (See the attached drawing that maps the corrosion on the #4 plates.) The pitting appeared more concentrated in the center of the plates. Vertical weld seams appeared full and without pitting. The pitting was generally located about 6' above the equator which is at the low point of where the water line appeared to fluctuate. (See the attached Plate Stress Check.) Painters rails and stiffener angles had rusting, but it was more oxidation build-up than heavy pitting and the angles were in good shape. Our inspector noticed that the corrosion was mostly on the south side of the tank as the attached drawing reflects. One reasonable theory for this phenomena is that rectifiers on the anodes of the cathodic protection system may have failed in this quadrant. However this is hypothetical. Since the paint system is over 35 years old, there are too many variables that would contribute to the localized pitting and the general corrosion. The bottom bowl and head plates also have moderate corrosion with general pitting of about 0.02". The riser column has been sandblasted but we have presumed that it also had moderate corrosion. The attached plate stress check has one sample of calculated requirements for a point on the #4 plate. Overall, we feel that the corrosion is not detrimental to the structural integrity of the tank, and no operating restrictions to the specified capacity or head range is needed. We do recommend that the tank interior be repainted to prevent additional oxidation and metal loss. The locally pitted areas should be covered with Tnemic 63-1500 "Filler and Surfacer" or equal after application of the prime coat. We also recommend cathodic protection for the tank and the riser column. After the tank is placed back in service, the #4 plates must be visually examined at 24 month intervals to insure that the paint system and repairs are in good condition to keep additional corrosion in check. Tank Components The tank accessories appear in good condition and undamaged. Two tower rods have been hit by equipment but are only slightly bent. 2 In Chicago Bridge & Iron Technical Services Company The attached report sets forth the visual observation of CBI's inspectors during the inspection of the tank performed on September 16, 1996; however, it is expected that you will satisfy yourself as to the adequacy or accuracy of any information provided by CBI and take full responsibility to any decision you make as to the use of any of the information provided by CBI. CBI is not able to guarantee or represent that the tank and paint may not be subject to a condition or conditions which may not have been discovered by CBI's inspector but which may become evident during repairing, repainting and/or further use of the tank. CBI makes no warranty of any kind, expressed or implied, with respect to these services. If you have any questions concerning this report please contact the writer, John Julian or Terry Grill of our Plainfield office. Regards, Andrew K. Edenbum Terry S.Grill Engineering Coordinator Inspector 3 TANK INSPECTION REPORT Inspection Contract No. 961623 Original Contract No. 8-0381 Year Built 1960 Inspected By Terry Grill Date of Inspection 10/24/96 & 10/25/96 Location: Street 12"' Street NE Zone 565 City Present Owner City of Renton Original Owner City of Renton State/Province Washington DESCRIPTION OF TANK Type of tank © 750MG Spheroidal Column Supported Tank Capacity 750,000 Gallons Type Construction (Riveted, Welded) WELDED Number of Columns 8 Height 100'-0 BCL Type of Bottom Torus Type of Roof Spheroidal Number of Tower Panels Type of Columns (Laced or Tubular) Tubular Riser (Wet or Dry) Shell Ladder (Revolving or Fixed) Fixed Roof Ladder (Revolving or Fixed) Fixed FOUNDATION CONDITIONS 1. Are there any indications of foundation settlement? No If "yes" describe 2. Is concrete or grout chipped or cracked? Yes If "yes" describe Minor surface cracks in top of two column piers Grout loose under several column base plates but only about Y2" deep (local in nature only 2"-3" long) 3. Is soil around base of tank saturated with water or are there any indications of underground pipe leaks? No If `yes" describe Standing water was noticed around center riser but this condition was from rain ponding 4. Is soil eroded so that any part of the foundation is undermined or a large part left bare? No If "yes" describe 5. How far does the foundation extend out of the ground? (Column Piers) Several are flush with soil up to 12" proiection on others (lay of land) (Riser Pier 4 to 5 inches ) (Ring Wall NA © Put N/A by parts of this report that do not apply to type of tank being inspected. PRINTED IN USA GO 1036 (Page 1 of 9) REV APR 79 6. Does the tank have a valve pit? No Is the valve pit dry? N/A Are there any indications that the valve pit or floor slab have settled? Is the concrete of either cracked or chipped? N/A Describe, if required 7. Are foot elbows, etc. anchored to valve pit floor or floor slab with thrust blocks or anchor bolts? Underground Are there any indications any of the pipes have moved? No Describe, if required PAINT (HISTORY) General information about previous paintings (If available) 1. Dates of last painting: Inside 1960 (At Erection) Outside 1978 2. Surface preparations used: Inside Pickle & Prime in Shop - Spot Blast in field Outside 1978 Sandblast 3. Paint system or type paint used: Inside Zinc dust -Zinc oxide phenolic paint Outside 1978 Tnemec series 70 polyurethane 4. General comments concerning last or prior painting (Dates, type paints, etc. for previous systems) The exterior system is in good condition but there are several spots where the paint system is breaking down Interior has been sandblasted clean over about 85% of the total area: light to moderate corrosion was found through out the interior wetted surfaces TOWER 1. Are tower posts in line? Yes 2. Is riser or cylinder straight? Yes 3. Are tower rods and cylinder rods in good adjustment and well tuned? Yes 4. Are rods in good condition? Yes** (If rods are reduced in size, measure part and give dimensions N/A **Two rods have been hit by equipment working around the base of the tank forming slight bends but smooth deformation 5. Are tower rod pins, strut pins and cylinder rod pins or bolts in good condition? Yes IMPORTANT: If pins with cotters, are all cotter in place and well spread; If pins with nuts, are all nuts in place with threads burred or welded? PRINTED IN USA GO 1036 (Page 2 of 9) REV APR 79 6. Are struts in good condition? Yes 7. Are columns in good condition? Yes B. Are column connections in good condition? Yes 9. Is balcony floor in good condition? Yes (Rain water was ponding in several areas) but no damage noticed 10. Is balcony toe plate in good condition? Yes 11. Is balcony hand rail in good condition? Yes 12. Are balcony splices, supports and connections to tank in good condition? Yes Sections 1 to 12, if answer is "no" describe. Rust was noticed around the drain holes on the underside of the balcony - did not appear to be serious, Oust surface rust. City intends to repaint the exterior of the tank within two years and this corrosion will be arrested at that time. However if the city has any spot "touch-up" work scheduled for the exterior, this area should be attended to. 13. Has dirt accumulated on balcony floor? No If 'yes", to what depth Very small amount at flange to web 14. Are there any missing bolts or rivets in the tower or in the balcony handrail? No If "yes" describe General condition of protective coating on tower and balcony (Specify by column, rods, etc.) Good coverage, many areas of mildew on all tower components, top coat beginning to break down Some minor rust on tower rods where struck by equipment. Estimated percentage of coats in good condition: top coats 75% - 85% primer 90% PRINTED IN USA GO 1036 (Page 3 of 9) REV APR 79 ANCHORAGE 1. Are base plates in good condition? Yes 2. Are anchor bolts tight? Yes 3. Are anchor bolts and nuts in good condition? Yes (some rust was noticed) (If anchor bolts are reduced in size measure and report dimensions) Bolts are rusting at base plate intersection, not considered serious at time of inspection but must be cleaned and repainted soon 4. Are anchor bolts connections or chairs in good condition? Yes Sections 1 to 4, if answer "no", describe CONDITION OF STRUCTURE Describe parts of structure that contains pitting on outside surface. None noticed, iust minor rust found Give size of pits, number of pits per square foot, depth of pits, is pitting localized or general? CONDITION OF METAL AND PROTECTIVE COATING OUTSIDE Large riser cylinder Good appearance, but paint beginning to break down Estimated percentage in good condition: topcoats 85 - 90% primer Shaft N/A Estimated percentage in good condition: top coats N/A primer Bell N/A Estimated percentage in good condition: top coats N/A primer Bottom Good, metal is covered and protected Estimated percentage in good condition: top coats 90 - Shell Fair, paint is cracking and peeling in isolated spots: will need attention soon primer 95% Estimated percentage in good condition: top coats 75 - 85% primer 85 - 90% Roof Fair, paint beginning to show signs of weathering - will need attention soon Estimated percentage in good condition: top coats 80% primer CONDITION OF THE PROTECTIVE COATING AND METAL INSIDE Large Riser Cylinder Interior has been sandblasted to bare metal Is the cylinder pitted? Yes If `yes" describe No access: can only estimate No. of pits per sq. ft. Est. up to 50 Size of pits Up to Yz" & 3/n Dia. Depth of pits Up to 1/32" isolated up to 1/16" (Estimated) Is pitting localized or General? General could only view from top looking down with hand light (discussed condition with consultant that had accessed the area) PRINTED IN USA GO 1036 (Page 4 of 9) REV APR 79 Condition of protective coating None (had been sandblasted) Estimated percentage in good condition: top coats 0% primer 0% Shaft Is the shaft pitted? N/A If "yes" describe N/A No. of pits per sq. ft. N/A Size of pits N/A Depth of pits N/A Is pitting localized or General? N/A Condition of protective coating Estimated percentage in good condition: top coats N/A primer Bell Is the bell pitted? N/A If'yes" describe No. of pits per sq. ft. Size of pits Depth of pits Is pitting localized or General? Condition of protective coating Estimated percentage in good condition: top coats primer Bottom A Are the bowl plates pitted? Yes If `fires" describe No. of pits per sq ft 50 Size of pits �/e" to W Depth of pits .02" in general .06" isolated Is pitting localized or General? General Condition of protective coating None: has been sandblasted to bare metal Estimated percentage in good condition: top coats 0% primer 0% B Is the head plate pitted? Yes If `yes" describe Same as bowl plates No. of pits per sq. ft. Size of pits Depth of pits Is pitting localized or General? PRINTED IN USA GO 1036 (Page 5 of 9) REV APR 79 Condition of protective coating None: has been sandblasted to bare metal Estimated percentage in good condition: top coats 0% primer 0% Shell Is the shell pitted? Yes Ring No. (From Bottom) If `fires" describe #3pls and #4 pls see below No. Pits Size of Per Sq. Ft. Pits Depth of Pits #3 plates (Equator pis) 50 per Sq Ft Up to W x 6" long Up to .1" (Equator course has 16-#3pl x 1/z" thk between columns & 843P pl x 5/8" thk at post heads #4 plates (Hip pis) Elonaated corrosion uD to 3/a" wide x uD to 6ft Iona runnina vertically .06"in aeneral The corrosion found did not tend to be located around the HAZ where the #4's are welded together, but seemed to be more concentrated in the center part of the plates. Corrosion was found adiacent to the vertical weld seams, but the weld bead appeared full. This elongated corrosion was generally located about 6ft above the Equator and covered an area on the plates about 5ft wide x 6ft(average) high. 19 of the 28 - #4 plates are corroded as described above. Due to the limited access depth of corrosion could only be taken in areas where sandblast cleaning had been completed: a spot check was taken at one location that was not cleaned - measured depths were .05" in general with .0625" in isolated spots at this location. Is pitting localized or general? Appears to be located where the water level fluctuates Condition of corner weld: outside N/A inside Condition of protective coating About 85% of inside tank had been sandblasted to bare metal Estimated percentage in good condition: top coats N/A primer PRINTED IN USA GO 1036 (Page 6 of 9) REV APR 79 Roof/Structural A Roof (Below H.W.L.) Is the roof pitted? No If "yes" describe small amount of rust at painters angle Pits per sq. ft N/A Size of pits Depth of pits Is pitting localized or general? Condition of protective coating None (sandblasted) Estimated percentage in good condition: top coats B Roof (Above H.W.L.) primer Is the roof pitted? None noticed If `yes" describe small amount of rust at plate laps Pits per sq. ft Size of pits Depth of pits Is pitting localized or general? Condition of protective coating Sandblasted to bare metal Estimated percentage in good condition: top coats MISCELLANEOUS primer Is the tank equipped with a cathodic protection system? Yes If "yes" describe Installed in 1971 Manufacturer CathPro Is the system operating properly? Assume!�res" Center riser does not have anodes at this time, discussed this with customer and was told this will be corrected Was the tank emptied for the inspection? YES If not completely emptied, state how far down Is any portion of the vessel exterior covered by frost casing No If "yes" state which part Description of frost casing (a) Type (wood, aluminum, etc.) (b) Date installed (d) Condition (c) Is it properly supported? PRINTED IN USA GO 1036 (Page 7 of 9) REV APR 79 Are there any indications of leaks in the tank or riser? No If `yes" describe Are there any indications of leaks in the piping, expansion joint, etc. No Is the bottom covered with mud or scale? Yes If 'yes" to what depth? 2ft to 3ft deep in sandblast residue Is there any indication that mud or scale from the tank has entered the outlet? NO If the tank is riveted, state the condition of laps and rivets on outside of cylinder, bottom, shell and roof. N/A Have rivet heads been seal welded? N/A Describe any previous repairs to inside areas. State condition of various components in terms such as good, fair or poor condition, or state if accessory not applicable. ACCESSORIES NOT APPLICABLE Tank or Riser Manhole Good Column Ladder Good Shell Ladder Good Roof Ladder Good Roof Manhole Good Roof Vent or Finial Good Inside Tank Ladder Scale build up. Good otherwise Spider Rods N/A Painter `s Angle Good Overflow Good Riser Ladder N/A Heater Pie N/A Expansion Joint N/A Other Accessories N/A PRINTED IN USA GO 1036 (Page 8 of 9) REV APR 79 Bell Door or Bell MH N/A Bell Ladder N/A Pi ing Insulation N/A Condensate Platform N/A Shaft Ladder N/A Access Tube Manhole N/A Access Tube Ladder N/A Describe fully any of the above accessories which are not in good condition. If repair or replacement of any part is recommended, give complete description including location and extent of repairs recommended. Repairs made by Inspector None Recommended Repairs 1. Interior must be repainted to help prevent additional plate metal loss. 2. The top wetted plates (#4 pls-hip course) must be visually examined at 24 month intervals to insure the paint system is in good condition and repaired as required in order to prevent additional corrosion to the area. 3. The customer should have the Cathodic Protection supplier design and provide a string of anodes in the V-0 diameter 4. Column anchor bolts must be kept in good condition, the corrosion noticed at the time of the inspection is not a problem, but remedial action must be taken soon to renew the protective paint coating. Any gap between the bolt shaft and hole in base plate should be cleaned of debris and sealed with a good quality caulk to help prevent moisture retention which can accelerate corrosion to the area Note: Additional pages to be used if necessary Date 10/28/96 Signature of Inspector Terry Grill PRINTED IN USA GO 1036 (Page 9 of 9) REV APR 79 NORTH Ccw MEASURED .0625" IN GENERAL (1) MEASURED 08" # • 4 (.25) (28 PLS ARGUNU I 28 26 1 25 24 23 22 21 20 19 18 I7 1 1 15 14 13 12 II I0 8 7 6 5 3 2 I PAINTER'S ANGLE AROUND i J i 1 I I i 1 i i I i i I i SLOT CUTOUT AND REWELDED i TOTAL CIRCUMFERENCE i I _i AT EQUATOR i I I I I I (APPEARS FROM ERECTION) i ftl OI I I -- - , COL #1 C C I I COL 48 COL #7 COL #1 n Annro rni I PLAN OF ROOF I I COL #6 COL #5 I NY #3 P PL i #3 PL 113 PL #3 PL COL # 4 COL 43 COL 92 COL #1 POSITION LADDER OF INSIDE COLUMN TANK LADDER ON EXTERIOR 13P (.625) 8 PLS #3 (.5) 16 PLS PLATES (114) 28 AROUND BASIS IN CHECKING #4 PL CL AWWA D100-84 TCL SNOW LOAD = 25 PSF 1/4 A 300 r- Corrosion DEFINITIONS o T1 = Latitudinal Stress (psi) T D R2 = 19.5' T2 = Meridianal Stress (psi) LO e 26.93' HR = Horizontal Radius (ft) ' c X=13.75' , R1 = Normal Radius (ft) E_Q `° c G o_ R2 = Radius of Curvature (ft) 2.545' L _ _ _ HR = 32.158' _ _ P = Water Pressure (psf) #344 #3 PL Mtl = Metal Load (kips) Seam 1/2 WT= Water Load (kips) S = Snow Load (kips) Area & Volume Calculations AAoc = 111.71 SQ FT xAoc = 27.68 FT ABED = 4.71 SQ FT xBGD = 32.60 FT ABGDO = 53.77 SQ FT xBGDQ = 27.98 FT AADB = 53.23 SQ FT xADB = 26.93 FT VADB = 9007 CU FT VADCL = 18286 CU FT Total Volume of Water above B = 27293 CU FT Surface Area = 2*pi 2*19.5*sin 0.731�os 0+19.2691+ 13.75 19.5*0.7109 = 2478 SQ FT #4PLtoB 2 2 J 0.71089 Water Load WT = 27293 x 62.4/1000 = 1703 kips P = 10.275*62.4 = 641 psf Metal Load Roof Load = 19 kips Paint Rail = 1 kips Stiffeners = 2 kips #4 PL above B = 25 kips Mtl = 47 kips Snow Load S = 43.4 kips T2 = (R1)*(P - (Mtl + WT + S)*1000) = 1517 LBS/FT 2 pi*HR^2 T1 = R1*(P - (T2)/(R2)) = 19192 LBS/FT (GOVERNS) tREQ'D = 19192 = 0.107 in < (0.25-0.08 = 0.17 in) (OKAY) 12* 15000 SUBJECT OFFICE REFERENCE NO. Plate Stress Check PCB REVISION 961623 MADE BY CHKD BY MADE BY CHKD BY 750MG x 100' BCL Spheroidal TSG AKE SHT 1 OF Renton, WA DATE DATE DATE DATE 11/1/96 11/1/96 CITY OF RENTON HIGHLANDS REPAINTING PROJECT PREDESIGN ACTIVITIES Prepared by CH2M HILL August 1995 CONTENTS Page INTRODUCTION 1 BACKGROUND 2 SUMMARY OF FIELD TESTING 3 RELATED EXPERIENCE - MT. OLIVET REPAINTING PROJECT 7 COST OPINIONS 8 CONCLUSIONS 10 RECOMMENDATIONS 11 Appendix A. PHOTOGRAPHS INTRODUCTION This report documents the results of Task 1, Predesign Activities, for the Highlands water storage reservoir recoating project. The work in this task was performed to observe structural and existing coating conditions and to estimate costs for the recoating project. It was completed in accordance with City of Renton contract No. CAG-95-039, dated April 26, 1995. The work performed in this task included field observations and preparation of cost opinions. BACKGROUND The Highlands water storage reservoir is a 0.75-million-gallon (MG), elevated steel structure. It was constructed in 1959 in accordance with American Water Works Association (AWWA) standard D-100-52. According to the record drawings, the steel plate material was specified to be ASTM A 283-GR-C; the tank structural steel was specified to be ASTM A-7. Access to the tank is available through two manholes. One 24-inch diameter manhole is located on the top of the tank. A second 12-inch by 18-inch access manhole is located in the center standpipe at ground level. A review of the original tank construction documents (specifications) indicates that protective coatings were specified for the interior and exterior of the tank to provide corrosion protection. The original specifications indicated that the internal coating was to be a three - coat inorganic zinc coating. A vinyl coating system consisting of a primer and subsequent coats to achieve a 5 mil thickness was specified as an alternative to the inorganic zinc coating for the tank interior. A corrosion evaluation in 1970/1971 indicated that the internal coating was beginning to deteriorate. Rust and corrosion pits were forming at isolated locations on the tank walls where the coating had failed. In 1971, an impressed current cathodic protection system was installed to provide supplemental corrosion protection to submerged surfaces in the tank. In 1978, the tank exterior was recoated. This work consisted of sandblasting and application of an epoxy primer and polyurethane topcoat. The existing protective coating system inside the Highlands tank is at the end of its service life. This study was made to determine the remedial actions required to provide continued corrosion protection for the interior of the tank. In addition to the tank interior painting, safety modifications to the tank ladder and hatch (platforms and railings) were incorporated into this project. OA SUMlIARY OF FIELD OBSERVATIONS Field observations were made to verify the condition of the existing coating inside the tank, and to observe structural items to allow design of new safety platforms and railings. Preliminary structural observations were made during the week of June 2, 1995. Obser- vations of the ceiling plates and roof supporting structure were made during the weeks of June 19 and July 24, 1995. These observations were made from a raft when the tank was full. The results of these field observations are summarized in the following sections. Photographs were made to document the condition of the protective coating and structural steel in each of the areas described below. These photographs are included in Appendix A. Interior Protective Coating System Exposed steel surfaces were observed by raft around and above the area of typical water level fluctuation (approximately 12 feet below the access manhole). These observations indicate that the coating on the exposed surfaces of the ceiling has a gray color typical of inorganic zinc coatings. The coating on the submerged portion of the tank surfaces, where observed, had a tannish white appearance. The tannish white coating could be an inorganic zinc coating in which the zinc has dissolved due to water immersion, or it could be a vinyl coating. The protective coating system on the submerged metals that could be observed exhibited extensive blisters. The coating blisters are relatively small, but are medium dense to very dense depending on where they were observed on the ladder and the tank walls. The degree of blistering is best described as Blister Size No. 4, Medium Dense (ASTM D714-- Evaluating the Degree of Blistering of Paints). Where the coating was intact on the ceiling, wall, and ladder, it had relatively good adhesion. Where the coating has failed at the blisters, corrosion products (rust) have formed. Most of the rust nodules were hard and tightly adhering to the steel. Some metal loss had occurred under the tightly adhering rust, but active corrosion appeared to be minimal due to the operation of the cathodic protection system. The coating system on the access ladder, although blistered, was providing acceptable corrosion protection where it was observed. Some light rust was observed on the top 3 to 4 feet of the ladder and at the ladder connection point at the roof, little corrosion was observed on the submerged portion of the ladder. Where the coating had failed on the ladder, white calcareous deposits had formed from operation of the cathodic protection system. No significant pitting of the ladder was observed in the area exposed. k The coating on the ceiling plates was in fair condition (approximately 10 percent of the surface had surface rust beginning to show). Rust deposits were present around the edges of lapped ceiling plates, painters rail, angles, and other areas that are typically difficult to coat. The paint thickness was measured at a limited number of locations with a magnetic thickness gauge. The paint thickness ranged from 3 to 6 mils. Two samples of the existing protective coating were collected from inside the tank. One sample was obtained from the ceiling and one from the wall. Both samples were laboratory analyzed for metals that could affect removal by sandblasting and debris disposal. The results of these tests are summarized in Table 1. Table 1 Concentration of Metals in Paint Samples Aletal Concentration of Metals in Paint Sample from Overhead Steel (ppm) Concentration of Metals in Paint Sample from Wall Plate (ppm) Arsenic < 3 < 2.9 Barium 13 11 Cadmium 250 50 Chromium 4.6 19 Lead 1600 1300 Mercury < 0.99 < 0.98 Pit depth measurements were made at evaluate amount of localized reduction in wall thickness that had occurred because of corrosion under the rust deposits. The maximum pit depth measured was between 40 to 50 mils, located on the wall plates at an elevation approximately 12 feet below the hatch level. Generally, the pits were relatively shallow (less than 0.020 inch). Structural Observations Structural observations were made to evaluate safety improvements to the tank access system. The results of these observations are summarized below: The ladder from the ground to the catwalk is equipped with a safety cage and safety climb device. There are no intermediate rest platforms in the 100-foot ladder between the ground and catwalk; two intermediate rest platforms would greatly reduce fatigue and improve safety aspects of the climb to the catwalk. Cl The ladder terminates at an awkward and unsafe manner at the catwalk level. Photographs of the ladder termination were made, and existing ladders, railings, and catwalk dimensions were measured. Discussions with structural personnel, and subsequent discussions with the City maintenance staff, indicated that a ladder landing with grating and handrails placed over the existing catwalk railing would be the most effective method to improve access and safety at this location. The ladder from the catwalk to the top of the tank is curved and follows the geometry of the tank shell. A safety climb device will need to be installed on this ladder. There were some signs of localized corrosion on the interior ladder where it is terminated to the underside of the tank roof, but the ladder appeared to be in sound structural condition. No safety railing or other platform is present on the tank roof around the access manhole, vent, and aircraft warning lights. Exposed cathodic protection conduit is also present at the tank roof, terminating at a junction box between the access manhole and the tank vent. Observations and discussions with structural personnel and City maintenance staff indicated that handrailing alone would be sufficient improvement at this location. Since maintenance activity is minimal on the tank roof, it was determined that a grating -type platform would not be required. Cathodic Protection The cathodic protection anodes were observed inside the tank from the raft. The anodes appear to be in good condition and should provide several more years of service. When the reference electrode is removed as part of the interior repainting project, it should be observed to determine if it needs to be replaced. Exterior Protective Coating The exterior protective coating was observed during this task. The exterior protective coating is presently providing effective corrosion protection for the exterior surface of the tank. Active corrosion was observed at only one location --an area of approximately two square feet on the overflow pipe at the catwalk level. However, it was noted that the there are many areas, particularly on the tank bowl above the catwalk, where the topcoat is disbonding from the primer. This effect was observed with the manufacturer's representative of the existing protective coating (Tnemec). Paint samples were removed and laboratory analyzed by the manufacturer. We have not yet received a formal report from the protective coating manufacturer; it will be forwarded to the City when it is received. 5 It was also noted that mildew is growing on much of the tank exterior surfaces (primarily on the vertical surfaces) over a large percentage of the surface. The long-term presence of the mildew will eventually begin to degrade the protective coating system. The tank should be pressure washed to remove the mildew. The primer on the exterior surfaces of the Highlands tank appears to be in good condition and appears to have good adhesion to the tank steel. The existing protective coating was applied in 1978. The City should consider applying a new finish coat to this tank for the following reasons: • The existing coating is 17 years old • The amount of work required to touch-up damaged areas • The repair to damaged areas will result in adverse aesthetic conditions (spots) • The tank needs to be pressure washed, an item that would also be required as a surface preparation for a new finish coat The City should plan to apply a new finish coat to the tank exterior within the next two years. The protective coating (primer) will deteriorate without this work and result in the need to re -sandblast the tank sooner than would normally be required. M RELATED EXPERIENCE - MT. OLIVET TANK REPAINTING PROJECT The interior surfaces of the 3-MG Mt. Olivet ground level tank was recoated in 1991. Although this tank is a ground level tank and had a different coating than Highlands, both tanks were constructed within five years of one another and have been exposed to similar water conditions. Both tanks were provided with cathodic protection at the same time. The experiences during the Mt. Olivet tank repainting project that may affect the Highlands tank painting project are discussed below. • Pitting. Although pit depth measurements were obtained during the predesign, it was not practical to fully evaluate pitting until the tank was sandblasted and the primer was applied. An extra coat of paint, epoxy filler, and pit welding were considered for repairs at Mt. Olivet. An extra coat of paint was considered the most cost effective method for extending the service life of the protective coating at pits in the Mt. Olivet tank. The additional coat of paint was approved at a cost of $14,375. • Weld Protrusions. Rough weld protrusions were present throughout the tank where erection equipment was attached to the tank during construction. These protrusions were too large and rough to be effectively prepared or removed by sandblasting. Therefore, an additional item of work was approved to remove the weld protrusions by grinding. The additional cost for this work was $6,500. Both pitting and weld protrusions were observed in the Highlands tank. The pitting is relatively shallow in the areas observed; however, it will not be practical to fully evaluate the pitting until the tank has been dewatered, sandblasted and primed. Trowel -grade, potable water epoxy pit fillers are available for repairing pitted steel water tanks. One of these products was evaluated for the Mt. Olivet tank, but was rejected since the contractor's proposal was considered too expensive. Consideration should be given to including the epoxy pit filler in the contract documents for this project to be bid on a square foot basis. This will allow the City to select the filler option if it is deemed necessary without a significant change order. Weld protrusions were also observed inside the Highlands tank. However, they did not appear to be as rough or as large as those observed in the Mt. Olivet tank. However, it may be necessary to grind these areas. This work would best be accomplished on a negotiated force account with.ft.,w1 _wtor once the extent of the work is determined. Improvement projects on older water storage tanks may involve extra work that cannot be easily anticipated_ Therefore, the City should maintain a suitable contingency for this project to allow timely completion within the set budget. For example, the change order costs for Mt. Olivet were approximately 20 percent of the bid price. %I COST OPINIONS Cost opinions were developed for the proposed interior coating and structural modifications to the Highlands water storage tank. The cost opinions developed for this work are discussed in the following sections. Protective Coatings The presence of lead in the existing paint inside the Highlands tank can affect the cost of this project in two ways. First, sandblasting operations inside the tank, which is a confined space, can result in dust in the air that contains lead. If the lead content in the air inside the tank exceeds the action limit, the contractor must provide for worker safety in accordance with OSHA rule 1926.62. This would include, among other items, appropriate respiratory protection, personal protective clothing, on -site changing areas, hand -washing facilities, biological monitoring, and personnel training. Our recent project experience indicates that removal of protective coatings with approximately 1500 ppm lead in a confined space can result in exceeding the lead action level. The second factor that can impact the cost of the project is disposal of sandblast residue contaminated with lead. If the lead content of the sandblast residue exceeds the action level according to WAC 173-303-070, the residue must be treated and disposed of as a hazardous waste. Disposal of the waste as a hazardous waste will significantly increase the cost of the project. Since the existing paint contains lead, it is difficult to establish a single cost for this work. Therefore, cost opinions were developed for three alternatives and are summarized in Table 2. Table 2 Cost Estimates for Interior Tank Repainting (Excluding Structural) Alt. Description Cost Opinion 1 Repainting with no lead in air and no loead in sandblast residue $118,000 2 Repainting with lead in air, no lead in sandblast residue $135,000 3 j Repainting with lead in air, lead in sandblast residue $181, 000 The bid prices for this work may vary significantly due to the contractor's approach to sandblasting and their estimates for handling and disposing of spent sandblast material which contains lead. The disposal costs will vary based on the amount and type of material to be disposed and/or the disposer's perception of risk. One local painting contractor (Dunkin and Bush, Redmond, WA) experienced with lead paint removal projects was contacted for estimated costs to recoat the interior of the tank. The contractor was asked to estimate the costs of sandblasting all interior surfaces to bare metal, recoating the interior with a three coat polyamide epoxy paint system, and disposing of the sandblast residue. The contractor's estimated the cost for this work was $160,000 to $180,000. The estimate provided by the contractor included medical tests to ensure that workers are not over -exposed to lead. If the project is completed during the winter months (December, January, February), it is estimated that an additional $15,000 to $25,000 will be required to pay for heating/dehumidifying equipment within the tank. The City should include a contingency in the budget to provide for grinding, pit repairs or other minor structural repairs if they are required. The pits we observed were not deep enough to warrant repairs, but others may become apparent as the surface is sandblasted and closer observations are made. We suggest that the contract documents include provisions for pit repairs by force -account. Structural Additions The cost estimate for the structural additions to the Highlands water tank are estimated to be $25,000. All cost estimates prepared in this report are in 1995 dollars and include a 25 percent contingency. Sales tax is not included. They have been prepared for guidance in project evaluation and implementation from the information available at the time of the estimate. The final costs of the project will depend on actual labor and material costs, worker safety requirements, costs for disposal of hazardous waste (lead contaminated abrasive aggregate), productivity, competitive market conditions, final project scope and schedule, and other variable factors. The final project costs will vary from these estimates. Because of these factors, funding needs must be carefully reviewed prior to making specific financial decisions. 9 CONCLUSIONS Based on our observations and tests of the Highlands elevated water storage tank, we have concluded that: 1. The protective coating inside the tank has reached the end of its service life. The coating on the roof structure and ceiling plates is in fair condition. 2. The existing coating contains lead. When this coating material is removed by sandblasting, the operations may result in requirements for worker safety. The resulting sandblast residue may contain enough lead to require special handling and disposal. 3. The ladder inside the tank is in good condition. 4. The pitting of the tank walls may require some isolated repair by welding, to replace lost metal. This can be handled contractually by force account since the extent of welding repair will not be known until the tank is sandblasted. 5. The existing cathodic protection system is in good condition and should provide several more years of service. 10 RECOMMENDATIONS The existing coating inside the tank should be removed and replaced. The new coating system should consist of the following: • Surface Preparation: White -metal sandblast (SSPC SP-5). 1J c C� • Coating Type: Potable water approved polyamide epoxy. b °'�"� Loa�'�r`�2 • Number of Coats, Thickness: three coats, twelve mils dry film thickness (plus one stripe coat of all welds and edges of structural steel). Since pitting of the steel was observed inside the tank, an epoxy filler is recommended. After the tank has been sandblasted and primed, observations can be made to determine if and where the filler is required. The epoxy filler will be used where pits are found that have sharp edges. Pits with rounded edges, depending on pit depth, should be adequately protected by the specified coating at 12 mils. �a Provisiom should be inc d in the contract documents to ensure that the contractor " , C�C_ monitors and provides for worker safety in accordance with OSHA Rule 29 CFR 1926 WAC-296-155-176. If lead in the air exceeds action levels, the contractor must provide for worker safety as required by the regulations. Waste generated by paint removal operations, including paint chips from sandblasting, must be characterized for hazardous and dangerous waste constituents in accordance with applicable federal, state, and local regulations including 40 CFR 261 and 262 and WAC 173- 303-070. If it is determined that the waste is hazardous or dangerous waste, the Contractor must store, transport, and dispose of the waste in a manner that is in compliance with applicable federal, state, and local regulations. The Contractor must provide a copy of the waste determination analytical results and the final disposition of the waste shall be certified by the Contractor with a certificate of acceptance and hazardous or dangerous waste manifest, if applicable, from the disposal site. The City will have the right to approve or disapprove of the transportation and disposal methods and the disposal site selected by the Contractor. Structural modifications are recommended to improve access and worker safety on the elevated sections of the water storage tank. These modifications include installation of a platform at the catwalk, handrailing around the hatch at the top of the tank, and a safety climb device on the ladder between the catwalk and the tank roof hatch. The exterior of the tank should be recoated within the next two years. We anticipate that this work would consist of a pressure wash, spot repairs, and application of one or two finish coats. A nonskid surface should be provided under the roof access ladder and within the roof handrail area as part of this project. 11 The cathodic protection anodes and reference electrode should be reinstalled after the tank recoating is complete. However, the cathodic protection system should be turned off for at least one year (the paint warranty period). The system can re re -energized in the future when visual observations indicate it is needed. 12 HISTORY OF THE HIGHLANDS ELEVATED RESERVOIR (SUMMARY) 1959-60 The reservoir was constructed. 1969 The Reservoir was inspected on 3-2-69. At that time it was noted that the paint system on the interior of the reservoir had deteriorated considerably, particularly on the shell and bowl. However, there was very little evidence of corrosion damage to any area of steel. Recommendations included the installation of a cathodic protection system and repainting of the exterior of the reservoir within 12 months. 1971 Installation of cathodic protection: Anodes and associated equipment installed in August 1971. Rectifier installed in October 1971. System energized and adjusted 10-29-71. 1973 The cathodic protection system was inspected on 7-11-73. The system was found to be operating correctly. Anodes were discharging current properly and showed very little deterioration or metal loss. 1977 The cathodic protection system was inspected on 7-20-77. The system was found to be operating properly, providing adequate control of corrosion to the interior submerged surfaces. 1978 The exterior of the reservoir was painted in 1978. 1978 The cathodic protection system was inspected in 1978. The system was found to be operating. Recommendations were made to repair certain mechanical and electrical elements of the system. 1979 Repairs were made to the reservoir as per the recommendations made in the 1978 inspection report. 1985 The interior of the reservoir was inspected on 10-23-85. Corrosion was observed on the tank walls in the area of water fluctuation. The ceiling coating was found to be in good condition with some areas of rust around the support beams. The coating at the tank base near the stand pipe exhibited good adhesion and an acceptable coating thickness. No metal loss or pits were noted in this area. Calcareous deposits on the interior ladder indicated that it was receiving good corrosion protection. The cathodic protection system was inspected on 12-5-85. All components of the system were found to be functioning properly and the structure -to -water potentials indicated that the interior submerged surfaces of the tank were receiving adequate corrosion protection. Minor deterioration of the anodes was noted. The exterior coating was found to be in excellent condition with only minor areas of coating damage. 1995 Observations of the interior and exterior of the reservoir were made during the months of June and July of 1995. CITY OF RENTON PLANNING/BUILDING/PUBLIC WORKS MEMORANDUM DATE: November 28, 1994 TO: Lys Hornsby FROM: Tom Malphrus SUBJECT: History of the Highlands 565 Zone Elevated Reservoir I perused our files and pieced together the following history of the Highlands 565 Zone elevated reservoir. I have more specific information on hand, including information regarding the composition of the interior coating. 1960 The reservoir is constructed. The reservoir is accepted by the City of Renton on July 11, 1960. 1969 The interior and exterior of the reservoir is inspected by CH2M. C142M recommends the installation of a cathodic protection system and repainting of the exterior of the reservoir. CH2M also addresses reservoir downtime and water supply to the 565 zone during reservoir downtime. See report dated May 1969. 1971 A cathodic protection system is installed. The system is energized and adjusted on October 29, 1971. 1973 Survey of cathodic protection system by CH2M/Hi11. The system is found to be operating correctly. See report dated September 14, 1973. 1977 Inspection of the cathodic protection system by CH2M/Hi11 on July 20, 1977. System is found to be functioning properly. See report dated January 18, 1978. 1978 Report from CH2M/Hi1I dated January 4, 1978 regarding water supply options for the 565 zone when the reservoir is drained for exterior repainting. 1978 Exterior of reservoir is repainted summer of 1978. 1978 Inspection of cathodic protection system by Galka Associates August 26, 1978. System is operating. Galka Associates recommends repairs of certain mechanical and electrical elements of the system. See report dated November 30, 1978. 0, November 28, 1994 Page 2 1979 City crews perform repairs to cathodic protection system as recommended in Galka Associates report dated November 30, 1978. 1985 Inspection of interior of reservoir October 23, 1985 and cathodic protection system December 5, 1985 by CH2M/Hill. CH2M/Hill recommends replacement of interior coating within 5 to 7 years and a re -inspection of the interior coating within 2 years to monitor rate of deterioration.. The cathodic protection system is found to be functioning properly and capable of operating until the interior coating of the reservoir is replaced. See report dated December 13, 1985. 565res/thm