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Chapter 7
Bridge Maintenance
7.4. Bridge Painting/Coating/Sealing and Containment Stewardship Practices

Bridge painting/coating/sealing covers all protective and preventative maintenance activities designed to prevent deterioration of structure components. Components made of non-weathering steel are generally painted with a multicoat paint system to protect the steel from rust and corrosion. Bridges painted prior to 1975 typically used lead, chromium, or cadmium pigmented paints, which if removed must be removed according to strict EPA and OSHA guidelines and disposed of as a hazardous waste.

The 1990s saw great increases in the costs and complexity associated with steel bridge maintenance painting. While a low-tech, least cost approach to combating corrosion and deteriorating aesthetics prevailed as recently as 15 years ago, the increasing age of the infrastructure, increasing needs for immediate maintenance, over the past few years, environmental regulations have become the single most influential force affecting the bridge painting industry; specifically, the regulations regarding the VOC content of protective coatings and the environmental and worker health and safety regulations associated with the removal of lead-containing paint have had a significant impact on the bridge painting industry. [N]

Table 16 : Regulations Impacting the Bridge Painting Industry

Impacting Regulation

Effect on Coating Operations

OSHA; CFR 29 1926.62, Lead in Construction

Establishes guidelines for protection and monitoring of workers removing lead paint from bridges. Requires lead training and monitoring for workers.

EPA; Resource Conservation and Recovery Act (RCRA )

Regulates the handling, storage, and disposal of lead (and other heavy metals ) containing waste. Can increase the cost of disposal of waste from bridge paint removal by 10 times.

EPA; Comprehensive Environmental Response Compensation and Liability Act (CERCLA or Superfund )

Assigns ownership of and responsibility for hazardous waste to the generator "into perpetuity."

EPA; Clean Water Act

Regulates discharge of materials into waterways.

EPA; Clean Air Act Amendments

Mandates restrictions on allowable volatile-organic- compound (VOC ) content of paints and coatings. Regulates discharge of dust into air from bridge painting

The impact of regulatory compliance has spurred a shift in focus to achieving long-term effectiveness for the dollars spent, both to maximize the return on DOT investment and minimize environmental impacts. A number of FHWA research projects with regard to bridge coatings have addressed the life-cycle cost issue in detail. Research on the removal of lead-containing paint considered the relative cost increases associated with changing regulations that deal with removal and handling of hazardous debris during bridge maintenance painting operations. Research on environmentally compliant materials and testing of low volatile-organic-compound (VOC) coating systems focused on the relative cost/benefit of the durability of various paint systems based on performance data and relative costs of material and application. Materials testing projects - such as those on Performance of Alternative Materials in the Environment, Comparison of Laboratory Testing Methods for Bridge Coatings, and Environmentally Acceptable Materials for the Corrosion Protection of Steel Bridges - have had a direct influence on regulatory development and the development of measures for compliance by bridge owners. These projects provided critical, long-term performance data for many new, environmentally compliant bridge paint materials and provided justification for bridge owners to move away from technologically old, lead-containing paints to new, more durable formulations that contain little or no toxic pigments and significantly less solvent. A project on Issues Impacting Bridge Painting, performed an extensive life-cycle versus initial-cost analysis for various bridge painting scenarios and presented results in a spreadsheet program, to facilitate comparison of the various maintenance painting options based on a life-cycle cost analysis. The projects Performance of Alternative Coatings in the Environment (PACE), Environmentally Acceptable Materials for the Corrosion Protection of Steel Bridges, Effects of Surface Contaminants on Coating Life, Maintenance Painting of Steel Bridges, Issues Impacting Bridge Painting, Methodology for Evaluation of Corrosion Control Coatings, and Comparison of Laboratory Testing Methods for Bridge Coatings have had aspects that addressed the need for higher quality and shorter term coating-durability data. Common findings of these programs with respect to cost considerations were: [N]

  1. The relative cost of paint material is almost always insignificant when viewed in terms of the overall cost of the bridge maintenance job; and
  2. The advantage in the relative durability of the better coating systems often far outweighs the nominally increased cost of these materials at the time of application. In general, for moderately to severely corrosive environments, the most durable options in the coating material and in the surface preparation system will be the optimum choices from a life-cycle cost standpoint.

 

7.4.1 Guidance and Specifications for Bridge Painting, Coatings, and Removal

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Some states routinely involve state and federal environmental regulators in bridge painting design to help them satisfy the regulations. This has reduced compliance problems, cost increases associated with contractor force account work, and time delays; however, environmental regulators look for transportation agencies to come to them with good bridge painting plans and specifications. They are often reluctant to suggest specific methods and techniques, because it could compromise their regulatory role in the event of pollution problems. The FHWA website, allows searches of specific state highway agency specifications using key words such as paint, coatings, and recycling. The site has a discussion feature to facilitate questions. Also, the FHWA users guide and spreadsheet Cost Effective Alternate Methods for Steel Bridge Paint System Maintenance-Cost Model Users Guide (FHWA Contract No. DTFH61-97-C-00026) can be used to evaluate cost effective bridge painting approaches. DOTs often use multiple factors such as adhesion test results, structure life, maintenance needs, layers of coatings, costs, and available funding to make bridge painting program decisions.

The FHWA Publication No. FHWA-RD-94-100, Lead-Containing Paint Removal, Containment, and Disposal, provides information on the environmental and health regulations affecting the removal of lead-containing paints from steel bridges and includes a guide for waste reduction, control and disposal of the hazardous material generated by bridge paint removal operations. NCHRP Synthesis 251: Lead-based Paint Removal for Steel Highway Bridges and NCHRP 257: Maintenance Issues and Alternate Corrosion Protection Methods for Exposed Bridge Steel are earlier publications that remain valuable resources. Society for Protective Coatings (SSPC) Guide 6 (Containment design) and SSPC Guide 7 (Environmental monitoring) contain state-of-the-art guidance.

Missouri DOT Lead Paint Recycling

The Missouri Department of Transportation (MoDOT) maintains 7,138 bridges throughout the state of Missouri . Many of those bridges require lead paint removal and disposal prior to repainting. To safely accomplish this, the department contains and recycles the lead-paint waste through a lead-acid battery recycler. The lead is recovered in the smelting process and the steel grit or silica sand used as blast material and steel drums provide a substitute for fluxing agents used in the process. This has resulted in the complete recycling of hundreds of tons of former waste and saved valuable landfill space.

In 1996, MoDOT purchased two abrasive recycler systems. The abrasive recycler removed the lead paint from the steel grit by vacuum washes and magnetic separators. This reduced the amount of blast residue about 80 percent. In recent years, water blasting of bridge paint has greatly expanded and further reduced the amount of blast material sent to the smelters by 99 percent. In water-blasting, the water is recycled through a filter that removes the paint chips and the water is reused and at the end of the project, safely discharged to a permitted wastewater treatment facility. The paint sludge is recycled at a smelter.

MoDOT recommends the following practices when selecting a recycling company: [N]

  • Always check operating permits and qualifications of a prospective recycler.
  • Check their history and ask a lot of questions about past problems.
  • Review the environmental agency's files for any problems.
  • If the files are sealed, find out why, and if you do not get a satisfactory response, reconsider that company as a prospect to be your recycler.
  • Get a list of present and previous customers and talk to them about the company.
  • Most importantly, visit their facility and get a tour of their operation.

 

7.4.2 Metallizing

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As a result of life cycle cost analyses, a few states have begun to explore metallizing as a coating option. Metallizing is a term used to describe thermal sprayed metal coatings. For corrosion control coatings on steel structures, metallizing refers to the thermal spraying of zinc or aluminum alloys as a coating directly onto steel surfaces. The coatings are created by using a heat source (either flame or electric-arc) to melt the metal which is supplied as a wire or in powder form. An airstream sprays the molten metal onto the steel surface in a thin film. Once the metal strikes the steel it resolidifies to become a solid coating. Metallized coatings provide corrosion protection to steel by sacrificial and barrier protection. The coating itself provides a barrier between the environment and the steel surface, especially when applied in combination with conventional sealers as topcoats. Due to the electrochemical reaction between steel and zinc or aluminum in an aqueous and salt-contaminated environment, these coatings tend to "sacrifice" themselves to protect the steel at the site of any damage in the coating. This sacrificial protection is similar to the protection provided by zinc-rich primers or galvanizing. According to the Turner Fairbank Research Center, metallizing has been reported to be highly effective in numerous research projects and in observation of historical applications. [N] Many reports have proclaimed that a metallized structure will last 25 to 40 years with no need for maintenance touch-up. This greater life expectancy and higher effectiveness brings a higher initial cost, but a potentially lower long term cost. A project recently completed by the Illinois Department of Transportation (IDOT) incorporated metallizing technology as an experimental feature. For this project, the structural steel was metallized in the shop then transported and erected in the field. There have been several bridge rehabilitation projects around the country which have had metallizing done in the field on existing steel, but only a few have been completely metallized in the shop. The production rates, cost concerns, logistics, handling and construction issues were examined in this study in order to assist in determining the feasibility of and issues involved in using metallizing in shop applications. The project was considered successful and equipment advances enabled metallizing to be done much faster than in the past. The project illustrated that under life-cycle costing, metallizing can be advantageous despite its cost, on this project, of $9.18 per square foot versus $2.00-$2.50 per square foot for painting. [N]

 

7.4.3 Overcoating
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As an alternative to removal, some toxic based paint is in a condition that permits an overcoating of paint to effectively contain the toxic material and protect the steel. Critical variables which determine the success or failure of an overcoating job include: the condition of the existing paint, the extent of corrosion on the substrate, the level of surface cleanliness achieved, and the environment of exposure. A recently completed FHWA-sponsored study of various overcoating materials applied to bridge structures in various parts of the country resulted in the following general results: [N]

  • Multicoat systems, overall, performed better than single coat systems, with three coat systems showing generally better performance than two coat systems. This result is thought to be directly related to the occurrence of pinholes during brush application of maintenance coating materials; however, it shows a measurable benefit of the application of multiple coats in a realistic scenario. Other studies have shown similar results.
  • Coating materials performing well in the study were three-coat moisture-cured urethane systems, and three-coat epoxy based systems using a penetrating low-viscosity sealer as a primer. In addition, two separate three-coat low-VOC alkyd systems performed well. Of the single coat systems, the coatings based on calcium-sulfonate alkyd resins did best. Similar generic results have been found by other investigators.
  • In general, coatings that did well at any one test site did well at all four, diverse test sites (indicating some measure of surface tolerance, or "overcoating acceptability" for specific paint materials). Those materials that failed badly and early at any one site generally failed at more than one site. This would lend support to the use of patch tests as screening for acceptability of a particular overcoating material on a particular structure.
  • In the subject testing, failures were of two varieties, 1) early coating disbondment due to incompatibility of the overcoating material with the existing paint, and 2) rust through of the newly applied overcoating material at areas where the coating is over bare steel or existing rust.

The performance of a newly applied overcoating is highly dependent upon the condition of the existing coating over which it is applied. Overcoating over existing aged paints that are often brittle and loosely adherent can pose risks of early failure and large scale disbondment. The applied overcoat applies added stress by adding physical weight to the existing coating, shrinkage during drying, different expansion and contraction rates between two different paint systems with ambient temperature cycles, and softening of the existing coating due to solvents in the overcoat. The following steps can minimize this risk: [N]

  1. Prior to deciding to overcoat a particular structure, assess the condition of the existing steel and paint system. Condition can include extent and distribution of rusting, and adhesion. The extent of metal loss due to corrosion and the extent and distribution of paint breakdown are important in determining the scope of the work required to clean and overcoat the structure. Paint failure confined to specific definable areas is easier to clean and overcoat than general paint failure over the entire structure. Adhesion should be assessed using either standard test methods (ASTM D4541 or D3359) or by attempting to cut and lift the coating with a knife blade. If the coating lifts easily or crumbles at the tip of the knife blade, then application of overcoating paints should be considered high risk.
  2. Conduct a representative patch test of the new material over the existing material using representative maintenance painting practices. Allow this patch to weather several seasons and assess the compatibility of the systems. Research has shown that reasonably good performance is achievable with various different overcoating materials. A patch test will help eliminate coatings grossly incompatible with the existing paint on the structure.
  3. Where possible, consider using coatings similar to those currently on the bridge. Some investigators have seen good results from the application of newer, but generically similar alkyd coatings over older existing alkyd coatings. Some of the older technology coatings may present a compromise in overall durability when compared to newer coating materials, but in a maintenance mode, the compatibility of these materials is a definite advantage.

After the existing paint has been sampled and a plan of action developed for an appropriate paint system, spot painting can be performed by maintenance staff using the following guidelines: [N]

  • If the paint has not been proven to be lead/chromium/cadmium free, treat it as if it were hazardous and brief personnel accordingly (refer to OSHA pamphlet 3126).
  • Personnel removing the paint should wear coveralls, gloves, goggles, and a certified, properly fitting respirator for protection.
  • Ensure a containment system is arranged to catch and retain all the paint removed.
  • Apply an approved chemical paint remover on the desired area and allow it to stand.
  • Remove the paint with hand tools or scrapers that do no not cause the paint particles to become airborne.
  • Dispose of hazardous paint at the nearest district headquarters yard at the hazardous waste site in the area marked for toxic paint. Inform district personnel.
  • Prepare and clean the now paint-free surface and repaint the area with an approved paint.
  • Ensure that personnel do not eat, drink or smoke until they are finished and have washed and properly disposed of all contaminated tools and clothing.
  • Cracks in any bridge component should be evaluated and corrective action taken. A crack in any steel component must be promptly reported to the Bridge Engineer and corrected per recommendation. Cracks in wood or concrete should be evaluated first and then cleaned and sealed with an appropriate crack sealant. Larger cracks in concrete should be sealed with polymer or epoxy based sealants. Small shrinkage cracks and all concrete surfaces where the concrete is not a specialized or high density concrete such as latex modified or silica fume concrete should be treated with a silane based sealant.

Painting operations generate dust, solvent fumes, and noise. Every effort should be made to minimize the impact of these operations on the surrounding community.

Inspecting the Structure and Preparing Equipment

  • Inspect the structure paying particular attention to areas of localized rust because these are the areas that have shown to be prone to premature coating failure. Extra effort should be made to ensure that both the proper degree of surface preparation and the proper coating thickness are achieved in these areas. The presence of mill scale under the existing paint indicates a potential need for additional surface preparation. If mill scale is observed and abrasive blasting is not specified, the project Engineer should be notified since abrasive blasting may be required.
  • Inventory, inspect, and calibrate the equipment.

Surface Preparation

Proper surface preparation and proper paint application are the two most important factors needed in a high quality job that will avoid peeling paint and future environmental contamination. It has been estimated that 75 percent to 80 percent of all premature coating failures are caused, partially or completely, by deficient surface preparation and/or coating application. [N] Cleanliness is essential since the presence of oil, grease, dust, or soil prevent the paint from bonding. Mill scale, rust, and the existing paint may increase the chance of failure of the new coating. Clean surfaces must have an appropriate anchor pattern (surface roughness). This roughness helps the new paint to mechanically bond to the surface, promoting adhesion.

The Society for Protective Coatings (SSPC) has developed a nomenclature for the different types of surface preparation methods. Best practices for each are noted in a bulleted list following description of the SP level practice. FHWA has two studies that speak to this issue. [N] [N]

Hand Cleaning

SP-1 - SP-1 denotes "solvent" cleaning and can refer to solvent wiping, water washing, or steam cleaning. The surface is cleaned to remove oil, grease, etc. This must be done prior to ALL other cleaning operations as some final surface preparation methods will actually force the contaminants into the steel, which can lead to poor bonding and premature failure.

  • Clean, lint-free rags and clean solvent should be used to avoid the spreading of contaminants.
  • Once the contaminants have been visibly removed, a final wiping should be done with clean rags and solvent.
  • Workers should wear goggles, protective clothing, rubber gloves, and petroleum jelly on exposed body parts and should be equipped with appropriate respirators to avoid hazardous fumes.
  • Benzene and carbon tetrachloride are poisonous and should not be used as solvents and neither should materials with low flash points such as gasoline, methyl-ethyl ketone (MEK), and acetone. Consult the Materials Safety Data Sheet to determine the specific hazards and protection procedures to be followed for the solvent being used.

SP-2 - SP-2 denotes hand tool cleaning. Hand tools are used to remove loose mill scale, loose rust, loose or otherwise defective paint, weld flux, slag, and spatter. This is done by brushing, sanding, chipping, or scraping the surface. Tools used include wire, fiber, or bristle brushes, sandpaper, steel wool, hand scrapers, chisels, or chipping hammers. Tightly adhering rust, mill scale, and paint are allowed to remain. This method is generally confined to small areas.

  • Verify that the level of cleanliness noted in SP-1 has been achieved. Pay particular attention to the problem areas such as the top side of bottom flanges, the backside of nuts and bolts, the interior of box beams, and those areas where climbing is difficult and access is limited.

SP-3 - SP-3 denotes power tool cleaning. This is very similar to SP-2 except that power tools are used instead, thus making this a more viable and efficient cleaning method for larger areas.

  • Check that the power tools have not placed any oil or grease back onto the surface. If they did, the surface should be re-cleaned per SP-1.
  • Paint, rust, or millscale that can be removed with a hand scraper should not remain after a proper SP-3 surface preparation. A "dull putty knife" can be used to assess the acceptability of the surface.

SP-11 - SP-11 denotes power tool cleaning to bare metal. This method uses power tools to remove ALL paint, rust, and millscale and to roughen the surface to promote paint adhesion. SP-11 offers performance advantages over SP-2 and SP-3, which result in an irregular surface of bare steel, rusted steel, mill scale, and paint but it tends to be quite expensive because of the labor involved.

Blast Cleaning

Blast cleaning is the most effective method for surface preparation is blast cleaning. Blast cleaning is broken down into four levels according to the desired condition of the base metal. Blast cleaning does not get rid of oil and grease, which is done by solvent cleaning.

There are many types of abrasive on the market. Recyclable abrasives have gained popularity in recent years because their use can reduce waste handling and disposal by 90 percent.

Blasting Using Recyclable Abrasive

In this system the abrasive is accumulated after usage, cleaned, and reused more than one time. Recyclable abrasives must be hard and durable. Thus metallic material is typically used, and typically requires special equipment to collect, classify, separate, and convey collected waste residue. Also, since the abrasive is harder, contractors must pay close attention to abrasive gradation to keep a cleaned surface profile within acceptable ranges. A contractor must closely monitor the separation process. It is important to completely remove all fine material from abrasives. If the abrasive is improperly or incompletely cleaned, dust concentrations within the containment can be adversely affected.

Several methods are available in the industry to filter discharged air from the system. Often systems using water for blasting or water filters to remove particulates are not acceptable as the water then becomes another different waste for disposal; however, MDSHA uses a pressurized filter system to remove particles from bridge cleaning waste water. The Golden Gate Bridge Authority in the San Francisco Bay area uses filters to remove particles from bridge painting waste water.

As with all open blasting operations, the recycled abrasive method must be fully contained. Costs associated with recyclable abrasive include additional equipment and increased initial abrasive costs. This is offset by increased cleaned surface area per unit of abrasive (some times up to 100 cycles) and reduced volume of waste produced.

The Missouri DOT has developed a model recycling program for abrasive lead blast. MoDOT no longer does abrasive blasting with Department forces; the agency has tried to create incentives for contractors to develop cost saving techniques and technologies for recycling its abrasives. All MoDOT bridge painting waste containing lead collected by Department crews is taken to lead smelter for recycling.

Closed Abrasive (Vacuum ) Blasting

Closed abrasive blasting or vacuum blasting allows dust, abrasive, and paint debris to be vacuumed simultaneously with the blasting operation. Debris is separated for disposal and the abrasive is returned for reuse. Typically, hard metallic abrasives are used for this system.

Vacuum blasting equipment is expensive; however, both worker exposure to dust and environmental emissions can be minimized if operations are conducted properly. Special Provisions may allow vacuum blasting to be conducted without requiring full containment. Once again, systems that uses water or water filters cannot be used. Vacuum blasting is limited by its reduced production rate and operational problems cleaning edges and irregular surfaces. To be completely effective, the whole nozzle assembly must be sealed against a surface to maintain proper suction for the vacuum operation.

Figure 15 : Shrouded Power Tools


Shrouded Power Tools

Shrouded power tool technology has proven an effective engineering control that effectively prepares structural steel for new coatings, while simultaneously controlling all emissions in excess of 99.5 percent. On the Woodrow Wilson Bridge outside of the District of Columbia, this eliminated the need for containment and respirators and reduced the potential for lead poisoning to the environment or workers in the first place. These DOE, EPA, OSHA, and HUD-tested and approved tools utilize a mechanical, air-driven process that cleans surfaces to a bare substrate, while a High Efficiency Particulate Air (HEPA) filtered vacuum collection unit, the VAC-PAC, simultaneously captures dust and debris and transports it into an on-board 55-gallon drum. The Pentek system offers a fully integrated deleading system that removes, collects, drums, and seals the waste in a single step process for safe disposal. The shrouded power tools allow the workers to prepare the structural steel to a bare metal finish comparable to a Steel Structures Painting Council SP 6 specification, Commercial Blast Cleaning. Pneumatic-powered rotary scalers and needle guns are being operated simultaneously--the former for the rapid deleading of large, flat surfaces and the latter with adjustable shrouds and pivoting head for access to hard-to-reach areas, such as around bolts and angles, or in corners. Fifty-foot vacuum hoses attached to the tools convey all removed dust and debris down to the HEPA-filtered vacuum and waste collection unit, which is stationed on the deck of a barge below. The 100 percent mechanical coatings removal system minimizes the amount of waste for disposal, as well as the degree of the owner's liability and disposal costs, by adding nothing to the waste stream and collecting only the dust and debris of the coating itself. A typical lead abatement project employing Pentek's system deposits 2,500 square feet of surface in a single waste drum. An independent company conducted air quality monitoring for the project with personal sampling and high volume environmental monitors, which were placed strategically at the site. Two separate air readings with the high volume environmental monitors were conducted six weeks apart, one on land and one on the barge. The efficiency of the dustless power tool system was verified by air sampling results of two to three micrograms per cubic meter, far below both OSHA's Permissible Exposure Limit of 50 micrograms per cubic meter and the action level of 30 micrograms per cubic meter per eight-hour exposure limits. [N]

SP Levels of Blast Cleaning and Associated Practices to Avoid Current and Future Environmental Impacts

The following methods are presented in order of ascending cleanliness (i.e., SP-5 is most clean):

SP-5 - SP-5 denotes white metal blast cleaning. This level of cleaning is costly and is rarely specified for use on bridges.

  • The resulting surface should be free of oil, grease, dirt, rust, mill scale, all paint, and foreign matter leaving only a uniform grey-white color.

SP-6 - SP-6 denotes commercial blast cleaning.

  • The resulting surface should be free of oil, grease, dirt, all rust, mill scale, paint, and foreign matter (except for slight shadows, streaks, or discolorations caused by rust stains, mill scale stains, and tight residue of previous coatings).
  • At least two-thirds of each 150-cm² (9 in² ) area must be free of all visible residue and the remainder limited to those discolorations just mentioned.

SP-7 - SP-7 denotes brush off blast cleaning.

  • The resulting surface should be free of oil, grease, dirt, loose mill scale, loose rust, and loose coatings, retaining only tightly bonded mill scale, sound rust, and previous coatings.

SP-10 - SP-10 denotes near-white blast cleaning.

  • The resulting surface should be free of oil, grease, dirt, rust, mill scale, paint, and any foreign matter (leaving only slight stains from rust and mill scale).
  • At least 95 percent of each 150-cm² (9 in² ) area should be free of all visible residue with the remainder limited to slight discoloration.

SP-12 - SP-12 is the standard for pressurized water blasting.

The most common surface preparation specified for bridge use is SP-6, which requires SP-1. When repainting an existing structure, the Specifications may call for SP-2 or SP-3 in areas of limited accessibility. Recent research indicates SP-10 may be more cost effective than SP-6, particularly in more corrosive environments. Inspection should verify that both the proper level of cleanliness and the proper anchor pattern have been achieved.

Blasting operations require that several additional checks occur. The contractor's equipment and material must be checked along with the resulting anchor pattern.

  • Inspection of the Abrasive - The contractor will select the abrasive to be used based on the specified anchor pattern. The chosen abrasive should be free of toxic heavy metals such as lead, chromium, and cadmium and should not contain any free silica (sand) either. A sieve analysis from the abrasive supplier should be requested prior to delivery of the first load of abrasive.

    Once the abrasive is on site, obtain a sample of the stored abrasive material. It should be stored in a dry environment and should be clean, uniform, and free of any sign of moisture. To check, drop some of it into deionized water and shake. Watch for a film of grease or oil indicating the presence of contaminants. Keep a small sample of abrasive from each subsequent delivery. This will allow for a future analysis in the event that changes occur in the anchor pattern.
  • Inspection of the Air Supply - This is necessary to ensure that the air supply is not introducing neither contaminants that will be embedded in the steel nor oil or water into the system. Inspect the air compressor for contaminants. The compressor should have moisture and oil traps on all lines. Shut off the flow of abrasive. Place a white blotter cloth in the air flow. It should be placed approximately 0.6m (24 inches) from an outlet downstream from the oil separator and moisture traps. Let free air flow for two minutes. Check for visible contaminants in the air flow; if there are any, corrective action is needed. This test should be repeated every four hours or more frequently when the humidity is high.
  • Blasting Pressure - The blasting pressure should be at least 620 kPa (90 psi); any less than this can result in a lower anchor pattern and in slower production. However, jobs that use recyclable steel grit often use higher pressures. All high pressure air supplies and devices should be gauged for easy reading. For blasting, the critical pressure is located at the end of the blast nozzle. This pressure will be lower than that measured at the air supply due to loss in the hose. Hence, limiting the length of air hose is often a critical factor in the efficiency of a blasting operation. A pressure needle gage may be used at the nozzle to measure the true blast pressure.
  • Inspection of SP-6 and SP-10 - Once again, verify that the level of cleanliness noted above has been achieved including the referenced problem areas. The individual DOT Specification may provide a set of visual standards from either the National Association of Corrosion Engineers (NACE) or the Society for Protective Coatings (SSPC) to aid in this effort. Interpretation of the visual standards can take some discretion as well as some practice. Both SP-6 and SP-10 standards require the removal of ALL paint, rust, and mill scale. The only difference is in the amount of staining allowable on the bare steel surface.
  • Inspection of the Anchor Pattern - The anchor pattern needs to be checked to ensure that proper paint adhesion will occur. Profile inspection requires the use of a micrometer and replica impression tape. Comparison coupons can be used for a qualitative visual comparison of the profile.

Monitoring

Air and soil monitoring are becoming more common on lead removal jobs. Monitoring protocols differ, and there is no current consensus on what should be done in this area. FHWA's study tour on Bridge Maintenance Coatings Environmental and Worker Protection Practices reportedly uncovered no requirement or specification for environmental air monitoring for sources other than stationary sources, and bridges are not considered stationary sources; environmental air monitoring requirements for abrasive blasting of lead-containing paint from bridges and other structures were not encountered in the United States or Europe, despite increasing ambient monitoring for total lead in dust and particulate size (PM10) in this country. Nevertheless, many state DOTs, as well as numerous city and local authorities require environmental air quality monitoring for abrasive blasting operations as part of their specifications and policies. [N] FHWA's study notes that current FHWA research could lead to "more reasonable and applicable protocols for environmental monitoring during bridge-painting operations." [N]

FHWA's study found that soil lead level monitoring before, during, and after the project is usually required. The Swiss have noted that as much as 70 micrograms of lead per m 2 per day may be deposited during movement and teardown of containment systems. Allowable levels of total lead in soils were found to be as low as 50 ppm. Some states are requiring pre- and post-job soil monitoring for lead contamination, but the requirement is not universal. Characterizing the contamination level of soils surrounding bridge job sites and especially the specific source of lead in any one location is difficult at best. Field monitoring and research is currently underway to attempt to better define appropriate soil-sampling protocols. [N]

  • Soil sampling near and under containments is generally a good idea from a liability standpoint. Check for signs of surrounding ground or water contamination.
  • Air monitoring becomes more important if sensitive public access is nearby.

 

7.4.4 Paint Selection, Storage, Handling, and Mixing
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  • Use paints with maximum useful lifetimes, where toxicity is acceptable, not lowest cost, to maximize the time between repainting.
  • Verify that the paint has not exceeded its shelf life. Shelf life is the length of time, from date of manufacture, that a paint will remain usable when stored in its can. Consequences of exceeding the shelf life include: gelling, odor, changes in viscosity, formation of lumps, pigment settling, and color and liquid separation.
    • Check the date printed on the can with the shelf life to make sure the paint has not "expired." Some suppliers use a special code on the can which contains the date of manufacture. It may be necessary to call the supplier to read the code and assure that paint is fresh. Two-component paint systems often have a different shelf life for each component.
    • If the contractor desires to use this material that has exceeded its shelf life, he/she may submit a sample to the manufacturer's laboratory for analysis and possible re-certification. The contractor should not be allowed to use the material in question until written certification is received from the manufacturer.
  • Follow good storage practices and verify that the paint is not stored in areas subject to temperatures beyond the recommended limits. Going beyond the acceptable temperature range can cause changes in viscosity and shelf life. Water-based paint will spoil when stored below freezing. Solvent-based paint, on the other hand, may gel or become flammable or explosive when stored at high temperatures.
    • The contractor's storage site should be monitored with a high/low thermometer. Contractors often like to store the paint on site in a trailer. This is generally not a good idea because these trailers tend to get very hot during the summer and have limited ventilation. Paint should be stored in a climate-controlled environment.
    • Each lot of paint should be stored together.
    • Two-component systems should be stored close to each other, but be distinguishable from one another.
    • If the paint will be stored over several months, the cans should be inverted at monthly intervals to avoid excessive settlement and ease future mixing.
    • When opening the paint, the oldest paint should be used first. Look for signs of aging listed under shelf life.
    • Note the required temperature range for proper storage. Adherence to the temperature requirements noted on the Product Data Sheet is essential.
  • Verify that pot life has not been exceeded. Pot life refers to the length of time a paint is useful after its original package has been opened or, for two-component systems, the length of time after it has been mixed. Pot life is temperature dependent. The pot life on the Product Data Sheet is generally for 21 C (70°F). Contact the manufacturer for additional pot life information if the paint has been stored in temperatures outside of this general range. Exceeding the pot life can result in sagging of the fresh paint along with poor performance attributable to film porosity and/or poor paint adhesion. Two-component paints tend to become unworkable at or beyond their pot life.
  • Ensure proper mixing and use of thinner. Different paints have different mixing requirements. The instructions on the Product Data Sheet should be strictly followed. Thinner is a liquid added to the paint at the time of application to modify its viscosity. The Product Data Sheet will indicate the specific type and maximum amount of thinner to be used.
    • Upon opening the can, check the surface of the paint for "skinning over" of the paint. Any skin should be removed prior to mixing.
    • All paint must be thoroughly mixed in a clean container.
    • Check the bottom of the original can for evidence of unmixed pigment.
    • For two-component paints, verify that they are mixed in the proper proportion. The mixing operation should be witnessed and documented.
    • Unused paint that will be used the next day should not be left in buckets or spray pots. It should be placed in a container and re-mixed prior to use.
    • Thinner should be used only to achieve optimum viscosity for proper application and is not always necessary. Do not exceed recommended maximum use.
    • Witness and document each and any addition of thinner. Adding too much thinner can prevent proper application thickness and cure of the paint and may result in the mixture exceeding acceptable limits for volatile organic compounds (VOCs).
  • Verify drying and curing times. Drying time refers to the length of time a coating is sensitive to local damage. Curing time refers to the length of time it takes for a paint to reach structural integrity and be ready for service. The drying schedule on the Product Data Sheet will show how long it takes until the paint is dry to the touch, dry to tack free, and dry to recoat. Dry to the touch implies the paint won't collect dust; tack-free implies the paint does not feel sticky and can be handled without damage; dry to recoat implies the time needed to dry until the next coat of paint can be applied. Drying times vary significantly with temperature. This is particularly important in determining when the next coat of paint can be applied. Recoating before enough time has passed can seriously affect the curing and integrity of the layer being overcoated. Some paints, particularly two-component paints, have a maximum time to re-coat as well. Exceeding this could jeopardize the adherence of the top coat.
    • After painting, inform the contractor of the estimated time that should be allowed for the paint to cure. Do not allow another coat to be put on until the appropriate amount of time has elapsed per the existing weather conditions.
  • Carry out storing, mixing and cleaning operations on land.
  • Transport paint and materials to and from job sites in containers with secure lids and tied down to the transport vehicle.
  • Do not transfer or load paint near storm drain inlets or watercourses.
  • Test and inspect spray equipment prior to starting to paint. Tighten all hoses and connections and do not overfill paint container.
  • Plug nearby storm drain inlets prior to starting painting where there is significant risk of a spill reaching storm drains. Remove plugs when job is completed.
  • Cover nearby storm drain inlets prior to starting work if sand blasting is used to remove paint.
  • Perform work on a maintenance traveler or platform, or use suspended netting or tarps to capture paint, rust, paint removing agents, or other materials, to prevent discharge of materials to surface waters if the bridge crosses a watercourse. If sanding, use a sander with a vacuum filter bag.
  • Capture all clean-up water, and dispose of properly.
  • Recycle paint when possible (e.g. paint may be used for graffiti removal activities). Dispose of unused paint at an appropriate household hazardous waste facility.
  • Keep all materials securely locked up, to avoid vandalism and accidental spills into the watercourse. [N]
  • Hold a pre-painting meeting with the contractor, addressing the following issues. Minutes should be kept and a copy should be given to all meeting participants, documenting understandings and any agreements reached. [N]
    • The nature of the work and its effects on the surroundings, including possible mitigation measures.
    • Contractor's method of operation, including equipment and personnel.
    • Contractor's schedule. Discuss weather-related concerns.
    • Contractor's job-specific worker health and safety plan (if lead paint is present).
    • Proper storage of material and equipment.
    • Location of recycling and dust collection and storage equipment.
    • Inspector safety, including provision of safe access and safety from lead contamination.
    • Inspection and measurement procedures, including control points.
    • Identification and treatment of inaccessible areas.
    • Product Data Sheets and Materials Safety Data Sheets for all relevant materials.
    • Visual standards to be met. Discuss contractor's preparation of field reference sections.

 

7.4.5 Containment and Use of Enclosures
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Lead was a common component of industrial paints until the 1980s, and many of the steel bridges in the highway system are still coated with paint that contains up to 50 percent lead by weight. High lead-containing primers can often be identified by their red or bright orange color. However, not all red and orange paints contain lead, and some paints of different colors can contain a significant amount of lead. Lead is hazardous to humans if it is inhaled or ingested and a relatively small amount of ingested or inhaled lead dust can elevate a person's blood lead level. Proper respiratory protection should be worn to protect against lead hazards. "Proper" protection consists of either air-fed, positive pressure respirator hoods (as worn by abrasive blasters), or negative pressure, filter-cartridge respirators. Filters should be color-coded bright pink for fine dust particulate (i.e., HEPA filters). The required level of respiratory protection depends on the concentration of lead in the breathing air, and on the amount of time the worker is exposed. For most short-term inspections of jobsites without ongoing blasting, or outside of containments, a half-mask with appropriate HEPA cartridge is enough. However, while inside of containments during or immediately after abrasive blasting, an air supplied hood is likely to be required.

A containment system, or enclosure, is needed to prevent both lead and other debris generated during surface preparation activities from entering the environment and to facilitate its gathering and disposal. Enclosures are generally made up of combinations of cover panels, scaffolds, supports, screens, and tarps. The complexity of any given enclosure will vary depending on the method of paint removal being employed and the degree of surface preparation that is specified. For a simple scraping operation ground-covering tarps may be sufficient while for a blasting operation, the enclosure could be a designed structure with a negative pressure ventilation system.

Containments for abrasive blast (and other paint removal) operations are designed to protect the surrounding environment and the public from debris (flying abrasive) and potentially hazardous material (lead-containing dust) during a paint removal operation. In addition, these containment structures are intended to help contain and collect the lead-containing debris for proper treatment and disposal.

As the use of containments for paint removal jobs has become more common over the past several years, the design of containment structures has evolved. Currently, there are standard features of each containment method, but in large part, containments are custom-designed for each bridge job. The standard features are described in detail in the "SSPC Guide 6 - Containment." This guide is not all inclusive, but it is the industry standard for description and classification of paint removal containments. In addition, several States have their own classification systems, but most of them are somewhat similar to those in the SSPC Guide 6.

It is important to remember that the purpose of a containment is to do a conscientious, "state-of-the-practice" job in containing and collecting debris. With appropriate specifications, and designs, and a cooperative effort between the owner and contractor, very near 100 percent containment and collection of debris can be approached.

Containment of abrasive blast jobs involving lead are mandatory because the law requires collection of the hazardous waste. While there is no specific rule governing the "fugitive emissions" of lead-containing dust, this dust can be controlled by designing and maintaining the containment and ventilation system properly.

Bridge maintenance involves the installation of safety nets, tarps, enclosures, barges or other means to catch paint chips and removed debris, water and abrasive blasting to remove old paint, rust, grease etc., application of rust inhibitors, primer paint (zinc, aluminum or lead), mid-coat paint (epoxy, vinyl or lead) and final coat (epoxy, polyurethane, vinyl or lead). All of these activities and products are detrimental to aquatic life in the stream below and need to be prevented from reaching the stream.

Components of a Containment System

Containment System Structure - Containments can be scaffolded from the ground or rigged to hang from the bridge structure. The key issues to consider are structural integrity under wind load, abrasive waster load, and dynamic loads on the bridge. Access, air movement, and visibility should also be considered.

  • Use custom built enclosures to confine and capture the abrasives, old paint chips and paint where possible.
  • Erect shrouds around working areas and suspending nets and tarps below bridges to catch debris from abrasive removal of old paint and over-spray from painting, where wind conditions permit. The work area should be clearly distinguishable from the surroundings.
  • Anchor tarps to barges below and enclosing the bridge above to confine debris, where the bridge deck is not too far above water level. Using barges and booms to capture fugitive floating paint chips and debris netting is not adequate.
  • Tarps should be overlapped with seams fastened and should be in good condition and free of holes.
  • During blasting operations with negative pressure, the tarps should have a concave inward appearance. They should never appear to bulge during blasting.
  • The containment should be tightly sealed to prevent any dust from escaping. Continually evaluate and/or perform field checks on the effectiveness of any containment. Watch for signs of dust escaping the containment and/or dust being discharged from exhaust system. Check the ground around the containment.
  • The containment must also be able to support workers, construction loads, spent abrasive loads and wind load without placing undue stress on the bridge.
  • The containment should be constructed in accordance with the approved plan.
  • Use vacuum or suction shrouds on blast heads to capture grit and old paint where possible.

Ventilation - For work inside an enclosure air movement is necessary to avoid a build-up of dust. High dust concentrations impair visibility and increase hazardous exposure levels to workers. Without ventilation, workers and inspectors will not be able to see within minutes of blasting commencing. Ventilation also reduces the concentration of lead-dust in the work environment and makes clean up operations prior to painting easier.

Check for air movement with an anemometer, or get a rough idea of the amount of airflow by using a smoke bomb. Air movement is dependent upon the capacity of dust collectors, the volume of air input by makeup fans and blast nozzles, and interferences to airflow caused by the bridge structure itself. Ventilation ducting efficiency depends on the duct diameter and length, and on minimizing the number of sharp bends in the duct.

Location of dust collectors - Airborne emissions are often highest adjacent to dust collectors. While emissions should be minimized, they are unavoidable.

  • Dust collectors should be located in areas where emissions will have minimal effect on sensitive surrounding environmental or public areas.
  • Dust collectors should be operated at the rated capacity or at a capacity consistent with the ventilation design of the containment system.

Lighting - Proper lighting is often neglected. Inadequate lighting poses obvious safety concerns as it makes proper surface preparation and painting almost impossible.

The potential for escaped lead-contaminated air emissions during blasting operations also warrants the usage by abatement workers of full facepiece respirators operating in positive-pressure mode. Shrouded power tool technology has proven an effective engineering control that effectively prepares structural steel for new coatings, while simultaneously controlling all emissions in excess of 99.5 percent. In other words, the need for containment and respirators is eliminated or drastically reduced by preventing the potential for lead poisoning to the environment or workers in the first place.

 

7.4.6 Paint Application and Spraying Practices
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Once the proper level of surface preparation has been achieved and the quality of the coating system has been verified, the contractor is ready to paint. To prevent "rust-back" of the cleaned surface, the first coat of paint (primer) should be applied as soon as possible (within a few hours) after blast cleaning. Painting should begin at a practical time to avoid weather changes that could cause significant changes in the surface condition of the steel, i.e. nightfall.

Painting just before the onset of poor weather is not advisable. The current and expected weather, along with the curing time of the paint being used, should be considered prior to beginning the application process. To ensure that the paint is applied and allowed to dry and cure under reasonable environmental conditions, the following environmental conditions should be followed every four hours:

  • Temperature - The Specification will place limits on the ambient temperature to ensure proper curing. Most Specifications will require the temperature to be between 4 C or 10 C and 38 C (40 or 50°F and 100°F).
  • Relative Humidity - Again, due to of curing requirements, the Specification will limit the maximum permissible relative humidity, which is commonly limited to 85 percent.
  • Dew Point - Using the relative humidity, determine the dew point. The temperature of the steel should be at least 3 C (5°F) higher than the dew point. This "dew point spread" is used to ensure that no moisture is present on the steel prior to paint application.
  • Surface Temperature - The surface temperature of the steel should not exceed 52°C (125°F) during the painting process, and, again, it should be at least 3°C (5°F) higher than the dew point.
  • Wind - Heavy winds can cause problems. Airborne overspray, for example, may be carried onto adjacent houses, cars, etc. and can result in premature drying of the paint. If heavy winds are present, it may be best to delay the painting operation or to restrict spray application.

 

7.4.7 Debris Storage
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The disposal of equipment and materials used to remove existing paint is also expensive. The waste must be placed in storage containers approved by the EPA. The contractor had two options for removing and handling the existing paint. Each option is designed to either make the removed material nonhazardous or reduce the amount of hazardous material generated; depending on the removal technology used, the waste is used as a recycled material or placed in a hazardous-waste landfill after being treated. [N]

DOTs should and generally do require all waste generated during removal operations to be sampled and analyzed by the contractor and submitted to a laboratory for Toxic Characteristic Leaching Procedure Testing (TCLP) for eight environmentally regulated heavy metals typically found in paint and abrasive wastes. Paint debris is classified as hazardous due to the characteristic of toxicity, if after testing by TCLP, the leachate contains any of the elements in the concentrations equal to or greater listed levels. Other elements, chemicals, and characteristics can also cause a material to be hazardous as defined in 40 CFR 261, so best practice requires that: [N]

  • No other waste be mixed with paint waste generated during the cleaning process.
  • Accumulated wastes shall not be removed from the temporary storage area without proper documentation.
  • For all projects involving the removal of paint wastes, some form of manifesting is required.
  • Recycling (off-site) or proper disposal of hazardous abrasive-blast media and use of approved haulers to transfer the contained waste to authorized treatment and/or disposal facilities
  • The production of hazardous paint-removal waste should be minimized by the use of recyclable abrasive and the waste generated should be treated by effective methods to ensure its stability in waste containment sites. [N]

Lead-contaminated paint waste can be classified as hazardous material. As such, it is subject to strict disposal requirements. The contractor may wish to temporarily store barrels containing this waste on site prior to hauling them to an approved disposal site.

  • If the barrels are stored on site, regulations restrict such storage to 90 days. Some entities, such as New York City Transit, voluntarily limit temporary storage of hazardous wastes to 45 days, instead of the allowable 90 days. [N]
  • Barrels should be clearly marked as containing hazardous waste.
  • The barrels should be stored in a location inaccessible to the public, and they should also be in a location where they are not at risk of being hit by traffic.

The SSPC publication, SSPC 96-06, ISBN 1-889060-02-X, Guidelines for Cost-Effective Lead Paint Removal-Final Report includes information about waste testing and disposal. Also, it describes how Kansas DOT has placed bridge painting waste in concrete blocks.

 

7.4.8 Quality Assurance and Public Outreach Programs
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In 2001, Illinois' Department of Transportation (IDOT) revised its overall painting policy along with its environmental and containment specifications for all repainting maintenance. The most significant change in the specifications was related to quality control and quality assurance responsibilities. [N] The Kentucky Transportation Cabinet has also been a national leader in the development of a quality assurance for bridge painting and maintenance.

As a proactive quality assurance measure, the Indiana Department of Transportation outline for bridge painting pre-bid meetings, Specification & Pre-Bid Conference Content Review, is used by the Indiana DOT environmental and safety professionals to make pre-bid conference presentations. The outline helps InDOT staff ensure that important environmental and safety topics are always presented at these conferences.

Public outreach programs have become a part of bridge painting and lead removal projects. The Port Authority of New York City provides a good example program.

 

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Continue to Section 8.1 »
 
Table of Contents
 
Chapter 7
Bridge Maintenance
7.1 Preventative Bridge Maintenance Practices
7.2 Avoiding and Minimizing Impacts to Fish and Wildlife
7.3 Enhancements to Bridges and Stream Access
7.4 Bridge Painting/Coating/Sealing and Containment Stewardship Practices
   
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