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75 Beyond the survey and field removal of pavement markings, the research team also evaluated three other areas of interest to the research project. These areas, described in this chapter, are environmental and worker safety issues, temporary tape pavement markings, and masking of markings or blending of removed areas. The authors do not discuss the environmental aspects of temporary tape pavement markings or the masking or blending of removed areas. The environmental discussion is related only to the removal of pavement markings that are not removed by hand from the road surface. Environmental and Worker Safety Issues The section summarizes the environmental and worker safety impacts of pavement marking removal that need to be considered. Based on the removal technique used and the composition of the pavement markings removed, different regulations may need to be addressed for each removal proj- ect. Code of Federal Regulations (CFR) Title 40, Protection of the Environment, is the governing document for federal regulations concerning the environment. CFR Title 29, Labor, is the governing document for federal regulations concerning workers. Hazardous Waste Determination Under EPA hazardous waste regulations, the term generator is defined by 40 CFR 260.10 as follows: Generator means any person, by site, whose act or process produces hazardous waste identified or listed in part 261 of this chapter or whose act first causes a hazardous waste to become subject to regulation. In most cases, waste from activities associated with remov- ing pavement marking materials will be associated with a work site. Thus, each work site could constitute a separate generator location. For such waste generation, if hazardous waste is pro- duced in quantities of 220 lb or less in any month, the location would be considered a conditionally exempt small quantity generator (CESQG). A limited number of environmental rules apply to such generators. Conditionally Exempt Small Quantity Generator Require- ments. A CESQG may either treat or dispose of its hazardous waste in an on-site facility or ensure delivery to an offsite treat- ment, storage, or disposal facility. Regulation 40 CFR 261.5(b) states: . . . a conditionally exempt small quantity generatorâs hazardous wastes are not subject to regulation under parts 262 through 266, 268, and parts 270 and 124 of this chapter, and the notification requirements of section 3010 of RCRA, provided the generator complies with the [prescribed rules for managing the waste]. The hazardous wastes must be sent to a treatment, storage, and disposal facility (TSDF) located in the United States that is âpermitted, licensed, or registered by a State to manage munic- ipal or industrial solid wasteâ (40 CFR 261.5 (f)(3)). Most local industrial or municipal solid waste landfills can accept such waste. Such facilities typically have their own requirements for accepting certain wastes, including hazardous waste. Waste from Removal of Pavement Marking Materials. Waste resulting from removing pavement marking materials would include the chemicals and compounds found in the pavement marking materials as well as any compounds mixed with the pavement marking material. The additional waste products might include: â¢ Pavement (e.g., asphalt or concrete); â¢ Contaminants on the pavement surface, such as oil, grease, or heavy metals such as lead or chromium; and â¢ Material associated with the removal process, such as sand from sand blasting or water from high-pressure water blasting. C H A P T E R 6 Additional Areas of Study
76 Hazardous Waste. In order to determine whether a pave- ment marking removal waste stream is producing toxic haz- ardous waste, the responsible party should either test the waste using the Toxicity Characteristic Leaching Procedure (TCLP) described in 40 CFR 261.24, or apply knowledge of the waste stream to make this determination. As each waste stream is dif- ferent, this study cannot present a universal determination of all pavement marking waste streams with respect to the appli- cability of hazardous waste rules. In order to determine whether these solid wastes are hazardous, four lists must be checked, along with the definitions of characteristic hazardous wastes. F-List hazardous wastes are wastes from non-specific sources. They are listed under 40 CFR 261.31 (F-List). K-List wastes are hazardous wastes from specific sources, listed under 40 CFR 261.32. P-List and U-List hazardous wastes are from discarded chemical products. They are listed under 40 CFR 261.33. Char- acteristic hazardous wastes are defined under 40 CFR 261.21- 261.24. These are solid wastes that are hazardous due to ignitability, corrosivity, reactivity, or toxicity. Table 55 is a list of some of the chemicals contained in pavement mark- ing materials that are listed hazardous wastes. These include acetone, methanol, methyl methacrylate, and xylene. Toxic Substances Control Act The Toxic Substances Control Act (TSCA) provides a mech- anism for the EPA to identify, list, and categorize existing and new chemicals used in manufacturing and commerce. The primary purpose is to identify potentially dangerous products or uses that should be subject to federal control. The act also provides regulatory authority over polychlorinated biphenyls (PCBs), asbestos, radon, and lead. Section 8 of the TSCA requires the EPA to develop and main- tain an inventory of all chemicals, or categories of chemicals, manufactured or processed in the United States (the Chemical Substance Inventory). The initial list published in 1979 included approximately 55,000 chemicals in commerce. All chemicals not on the original inventory are considered new chemicals and are subject to the notification requirements of Section 5 of the TSCA. The list now totals more than 83,000 chemicals. It offers a valuable reference that complements material safety data sheet (MSDS) information. Much of the information contained in the TSCA database duplicates or supplements the information found on MSDS documents. Some MSDSs may refer to particular TSCA items, Chemicals from Representative Pavement Marking Material Safety Data Sheet Information Hazardous Waste? Hazard Listing & Applicable Regulation Acetone Yes F-003, 40 CFR 261.31 U-002, 40 CFR 261.33 Acrylated urethane No â Acrylic polymer(S) (trade secret) No â Alkyl glycidyl ether No â Barium sulfate No â Bisphenol-A-(epichlorhydrin) epoxy resin No â Dibenzoyl peroxide No â Dicyclohexyl phthalate No â Diethylenetriamine No â Diglycidyl ether of bisphenol No â 1,6-Diisocyanatohexane homopolymer No â Butyl methacrylate No â Hexamethylene diisocyanate No â 2-Ethyl hexyl acrylate No â Limestone No â 2-Ethylhexyl acrylate No â Methanol Yes F-003, 40 CFR 261.31 U-154, 40 CFR 261.33 Methyl methacrylate Yes U-162, 40 CFR 261.33 4-Nonylphenol No â Modified polyamine No â Polyurethane No â Silica (quartz/crystalline) No â Titanium dioxide No â 2,2,4-Trimethylpentane-1,3-diol monoisobutyrate No â Trimethylolpropane triacrylate No â Urethane acrylate No â Xylene Yes F-003, 40 CFR 261.31 U-239, 40 CFR 261.33 Table 55. Representative list of chemicals used in pavement marking materials.
77 and TSCA information can be useful when constructing a new MSDS document. Some MSDSs may contain code letters that are used in the TSCA Inventory to identify substances that are the subject of an EPA rule or order promulgated under TSCA, or to indicate a full or partial exemption from TSCA report- ing requirements. These codes are not required for an MSDS. The special flags used throughout the TSCA Inventory are intended to identify those substances on the inventory that are the subject of an EPA rule or order promulgated under TSCA, as well as to indicate the types of full or partial exemp- tions from TSCA reporting requirements. The following is a list of flags that are used (U.S. EPA 2011): â¢ Eâindicates a substance that is the subject of a Section 5(e) consent order under TSCA. â¢ Fâindicates a substance that is the subject of a Section 5(f) rule under TSCA. â¢ Nâindicates a polymeric substance that contains no free- radical initiator in its inventory name but is considered to cover the designated polymer made with any free-radical initiator regardless of the amount used. â¢ Pâindicates a commenced premanufacture notification (PMN) substance. â¢ Râindicates a substance that is the subject of a Section 6 risk management rule under TSCA. â¢ Sâindicates a substance that is identified in a proposed or final significant new uses rule. â¢ Tâindicates a substance that is the subject of a Section 4 test rule under TSCA. â¢ XUâindicates a substance exempt from reporting under the inventory update reporting rule, i.e., Partial Updating of the TSCA Inventory Data Base Production and Site Reports (40 CFR 710(C)). â¢ Y1âindicates an exempt polymer that has a number- average molecular weight of 1,000 or greater. â¢ Y2âindicates an exempt polymer that is a polyester and is made only from reactants included in a specified list of low-concern reactants that comprises one of the eligibility criteria for the exemption rule. Section 5 of the TSCA requires that a premanufacture notice be filed if a manufacturer plans to manufacture a product using a chemical not listed in the Chemical Substance Inven- tory. This would apply to pavement marking manufacturers using a new chemical for their product. (See http://www.epa. gov/oppt/newchems/index.htm). Clean Water Act The Clean Water Act (CWA) regulates discharges of pollut- ants from a point source into navigable waters. Such discharges are regulated under the EPAâs National Pollutant Discharge Elimination System (NPDES). Nonpoint sources of water pol- lution are also regulated under the CWA. The Nonpoint Source Management Program provides grant money for states, ter- ritories, and Native American tribes to support a variety of activities to control nonpoint sources of water pollution. These activities may include technical assistance, financial assistance, education, training, technology transfer, demonstration proj- ects, and monitoring. As a result of efforts by states and Indian tribes throughout the United States, many state departments of transportation have developed guidance to control nonpoint source water pollution associated with their construction and mainte- nance activities. A representative sample of these requirements follows. Alaska DOT & Public Facilities (AKDOT&PF 2005). The Alaska DOT&PF has published the Alaska Stormwater Pollution Prevention Plan Guide (effective January 14, 2005) to help contractors, consultants, and the public understand and comply with the requirements of the NPDES Stormwater Construction General Permit (CGP) for small and large con- struction sites. The guide covers site evaluation and assess- ment, best management practices for stormwater control, and requirements during construction and at the completion of the job. California DOT (Caltrans 2003). The Caltrans Storm- water Management Plan (CTSW-RT-02-008), May 2003, pro- vides guidance to reduce the discharge of pollutants associated with the stormwater drainage systems for highways and highway-related properties, facilities, and activities. These would include removal of pavement markings. Colorado DOT (CDOT 2011). As part of the permit that allows discharges from the roadway storm drain system, CDOT has several different programs in place to make sure the amount of pollutants being discharged is reduced; several of these programs include the following: â¢ Construction sites program: CDOT assures the adequate design, implementation, and maintenance of temporary best management practices (BMPs) at its construction sites. â¢ New development and redevelopment program: CDOT ensures that permanent BMPs are installed at appropriate construction sites to reduce the discharge of pollutants into stormwater after construction is complete. This program also provides for maintenance of the BMPs. â¢ Illicit discharges program: CDOT detects and removes illegal discharges to its storm drain system. CDOT has a permit from the Colorado Department of Public Health and the Environment to discharge stormwater from its storm drain system. The permit states that only storm- water (and a few other allowable discharges like landscape
78 irrigation overflow) can be discharged from CDOTâs storm drain system (CDOT 2008). â¢ Industrial facilities program: CDOT requires all facilities that discharge stormwater into CDOTâs storm drain sys- tem to obtain a specific authorization. The program pri- oritizes education to promote minimization of pollutants in the stormwater that the facilities are contributing to the system. CDOT also provides an Environmental Clearances Information Summary for permittees. â¢ Wet weather monitoring program: CDOT assesses wet weather impacts from highways and the performance of BMPs used to control stormwater discharges. Florida DOT, Florida Department of Environmental Pro- tection (FDEP 2011). Florida regulates stormwater associated with construction activities through the Florida Department of Environmental Protection under a general permit. The permit regulates stormwater discharge associated with large construc- tion activity, as defined in 40 CFR Part 122.26(b)(14)(x) and regulated pursuant to Section 402(p)(2) of the federal CWA. Stormwater discharge associated with small construction activ- ity, as defined in 40 CFR 122.26(b)(15), is regulated pursuant to Section 402(p)(6) of the CWA. The permit provides authoriza- tion to discharge stormwater associated with large and small construction activities to surface waters of the state, including through a Municipal Separate Storm Sewer System (MS4). Minnesota DOT (MnDOT 2011). The MS4 programs are required by the EPA and the Minnesota Pollution Con- trol Agency (MPCA) to reduce pollution from stormwater to surface waters and groundwater. Municipalities with popula- tions of 50,000 or greater and some smaller designated cities along with other public entities with significant stormwa- ter drainage systems such as universities, counties, or state transportation departments have been selected to have MS4 programs. MnDOT Metro is one of these designated MS4 programs. New York State DOT (NYSDOT 2003). The Memoran- dum of Understanding between the DOT and the Depart- ment of Environmental Conservation Regarding the SPDES [State Pollutant Discharge Elimination System] General Per- mit for Stormwater Discharges from Construction Activity, GP-02-01, 2003, provides requirements to control soil erosion, sediment, and pollutants on construction projects. Ohio Department of Transportation Stormwater Program (Ohio DOT 2011). âODOT created the Stormwater Manage- ment Program in response to being regulated as a Municipal Separate Storm Sewer System (MS4) under CWA require- ments administered by Ohio EPA [Environmental Protection Agency]. The Stormwater Management Program was designed to comply with NPDES stormwater permits issued by Ohio EPA, including the MS4 permit and statewide and watershed- specific construction stormwater permits.â Tennessee DOT (TDOT 2007). On May 10, 2007, the TDOT formally submitted the final Statewide Storm Water Management Plan (SSWMP) documents to the Tennessee Department of Environment and Conservation (TDEC). The SSWMP outlines the steps TDOT will take to implement ero- sion prevention and sediment control materials and practices for TDOT construction projects. The plan contains several documents, including: â¢ Program Rationale, Evaluations, and Recommendations for Erosion Prevention and Sediment Control Materials and Practices for TDOT Construction Projects. â¢ TDOT Environmental Division Mitigation Practices. â¢ TDOT Environmental Division Environmental Proce- dures ManualâUpdates. â¢ Manual for Management of Stormwater Discharges Asso- ciated with Construction Activities. â¢ Procedures for Providing Offsite Waste and Borrow on TDOT Construction Projects. â¢ Comprehensive Inspections Program. Texas DOT (TxDOT 2002). TxDOT published the Storm- water Management Guidelines for Construction Activities in July 2002. The guidelines are intended to prevent degradation of receiving waters, facilitate project construction and mini- mizing overall costs, and help TxDOT comply with federal, state, and local regulations. Virginia DOT (VDOT 2004) and Virginia Department of Environmental Quality (VDEQ 2004). Guidance Memo No. 04-2016, dated June 30, 2004, outlines the procedures that will be used to permit VDOT Virginia Pollutant Dis- charge Elimination System (VPDES) stormwater construc- tion projects. The VDOT Manual of Practice for Stormwater Management, dated November 2004, provides information regarding the management of stormwater at VDOT projects and facilities. Clean Air Act Air emissions regulated under the federal Clean Air Act (CAA) that may be associated with removing pavement mark- ings include particulate matter, lead, and volatile organic compounds (VOCs). Particulate matter is regulated under the National Ambient Air Quality Standards (NAAQSs). The NAAQSs regulate six criteria pollutants: carbon dioxide, lead, nitrogen oxide, PM10 (particulate matter smaller than, or equal to, 10 micrometers in diameter), PM2.5 (particulate matter smaller than or equal to 2.5 micrometers in diameter), ozone, and sulfur dioxide.
79 The limits include primary and secondary standards. Pri- mary standards set limits to protect public health, includ- ing the health of sensitive populations such as asthmatics, children, and the elderly. Secondary standards set limits to protect public welfare, including protection against visibil- ity impairment and damage to animals, crops, vegetation, and buildings. Under the CAA, as amended in 1990, each state must develop a plan describing how it will attain and maintain the NAAQSs. This plan is called the State Implementation Plan (SIP) and is required under Section 110 of the CAA (40 CFR Part 51, Subparts F & G). In general, the SIP is a collection of programs (monitoring, modeling, emission inventories, control strategies, etc.) and documents (policies and rules) that the state uses to attain and maintain the NAAQSs. A state must engage the public in approving its plan prior to sending it to the EPA for approval. The application and removal of traffic marking would be affected by SIPs under the NAAQSs. The applicability of these requirements are discussed in this section. Air QualityâParticulate Matter. Particulate matter may be produced when pavement markings are removed. During marking removal, particulates are most likely to be generated when dry blasting or grinding with sand, shot, or other hard materials as part of the removal process. The Clean Air Act requires the EPA to issue designations after the agency sets a new NAAQS or revises an existing standard. If an area does not meet the standard, the EPA formally designates the area as non-attainment (not meeting the standard). Once a non-attainment designation takes effect, the state and local governments have 3 years to develop implementa- tion plans outlining how the area will attain and maintain the standards by reducing air pollutant emissions contributing to fine particle concentrations. This can affect pavement mark- ing removal processes that generate particulates, such as dry blasting and grinding. The use of blasting or other removal procedures that produce particulate matter may be restricted in non-attainment areas. Air QualityâLead. The EPA strengthened the air qual- ity standards for lead on October 15, 2008, revising the level of the primary (health-based) standard from 1.5 micrograms per cubic meter (Âµg/m3) to 0.15 Âµg/m3, measured as total suspended particles (TSP). The agency revised the second- ary (welfare-based) standard to be identical to the primary standard. This change will affect the manner in which states con- trol ambient lead concentrations. State and local environ- mental regulatory agencies promulgate regulations directed toward meeting the EPA standard. Pavement markings may be affected if quantities near the regulatory levels are identi- fied in air emissions from removing them. Air QualityâMobile Sources. Under the National Emis- sion Standards for Hazardous Air Pollutants (NESHAPs), the EPA regulates activities such as paint stripping. However, pavement marking removal activities are not covered under the NESHAPs Paint Stripping and Miscellaneous Surface Coating Operations-Area Sources regulations. Regulation 40 CFR 63.11169 identifies the following three activities covered by these regulations: â¢ Paint stripping operations that involve the use of chemical strippers that contain methylene chloride (MeCl). â¢ Autobody refinishing operations that encompass motor vehicle and mobile equipment spray-applied surface coat- ing operations. â¢ Spray application of coatings containing compounds of chromium (Cr), lead (Pb), manganese (Mn), nickel (Ni), or cadmium (Cd). Further, the EPA does not intend to promulgate a Maxi- mum Achievable Control Technology (MACT) rule for major sources of paint stripping because applicable major source facilities have not been identified. Paint stripping operations currently performed are regulated under other NESHAP cat- egories such as wood furniture and aerospace. The source category will not be delisted because the EPA is required to consider area sources of paint stripping under its NESHAP rulemaking. Mobile source regulations under the CAA do not apply to pavement marking product removal. Air QualityâVolatile Organic Compounds. Certain organic compounds are readily emitted as gases from solids or liquids. These are known as VOCs. Some materials that emit VOCs include paints, lacquers, paint strippers, solvents, and pesticides. VOCs can be released during storage or use of these materials. VOCs are regulated under the NAAQSs. VOCs are important with respect to ground-level ozone (O3), which is typically created by a ground-level chemical reaction between oxides of nitrogen (NOx) and VOCs in the presence of sunlight. Pavement marking removal is subject to any VOC requirements in SIPs. The EPA Office of Air Quality Planning and Standards (OAQPS) has established several standard procedures for the preparation of SIP emission inventories. The Emission Inven- tory Improvement Programâs (EIIPâs) Area Sources Committee developed a guidance document on area sources. As part of this objective, the committee published a report that provided estimates of VOCs and hazardous air pollutants (HAPs) from traffic markings (Eastern Research Group 1997). The report provided information regarding estimated VOC emissions from various types of installed traffic markings. The VOC and HAP regulations would primarily affect the application and lifetime use of pavement markings. These regulations would apply to pavement marking removal operations only
80 to the extent that removal creates additional airborne sources of VOCs or HAPs. VOCs released from pavement marking material removal have not been identified as a significant source of VOCs. Subsequently, while it is possible that VOC requirements could be included in SIPs, it is unlikely that SIPs will include requirements on VOC emissions with regard to pavement marking removal. National Environmental Policy Act The National Environmental Policy Act (NEPA) became law in 1970. Among its provisions is the requirement for environmental reviews of all major federal actions. It was directed toward assuring that the federal government con- sidered potential impacts of its actions and decisions on the environment. NEPA requirements come into play when federal agencies are involved in funding, permitting, licensing, or making deci- sions that can affect the environment. The primary tools under NEPA are environmental assessments (EAs) and environmen- tal impact statements (EISs). These documents include pro- cesses that are designed to assess the likelihood of impacts from alternative courses of action. FHWA regulations, specifically 23 CFR 771âEnvironmental Impact and Related Procedures, address FHWA actions under NEPA. Regulation 23 CFR 771.101âPurpose states: This regulation prescribes the policies and procedures of the Federal Highway Administration (FHWA) and the Federal Transit Administration (FTA) for implementing the National Environmental Policy Act of 1969 as amended (NEPA), and supplements the NEPA regulation of the Council on Environ- mental Quality (CEQ), 40 CFR parts 1500 through 1508 (CEQ regulation). Together these regulations set forth all FHWA, FTA, and Department of Transportation (DOT) requirements under NEPA for the processing of highway and public trans- portation projects. This regulation also sets forth procedures to comply with 23 U.S.C. 109(h), 128, 138, 139, 325, 326, 327, and 49 U.S.C. 303, 5301(e), 5323(b), and 5324(b) and (c). Pavement marking removal would not typically be the cen- ter of a NEPA process. Regulation 23 CFR 771.117 sets forth the FHWA categorical exclusions under NEPA. The regula- tion states in part: (a) Categorical exclusions (CEs) are actions which meet the definition contained in 40 CFR 1508.4, and, based on past experience with similar actions, do not involve significant envi- ronmental impacts. They are actions which: do not induce sig- nificant impacts to planned growth or land use for the area; do not require the relocation of significant numbers of people; do not have a significant impact on any natural, cultural, recre- ational, historic or other resource; do not involve significant air, noise, or water quality impacts; do not have significant impacts on travel patterns; or do not otherwise, either individually or cumulatively, have any significant environmental impacts. (c) The following actions meet the criteria for CEs in the CEQ regulation (section 1508.4) and Â§ 771.117(a) of this regulation and normally do not require any further NEPA approvals by the Administration: 8. Installation of fencing, signs, pavement markings, small passenger shelters, traffic signals, and railroad warning devices where no substantial land acquisition or traffic disruption will occur. While this addresses the installation of pavement marking, the removal of pavement making is not specifically identified as a CE. Therefore, the applicability of NEPA to a project must be considered for each project based on the projectâs character- istics. This would be a function of the processes utilized. The presence of the marking material would have been a CE when installed. Therefore, the applicability of NEPA would focus on what other materials, equipment, or processes are necessary for the pavement marking removal, and their associated impacts. Health and Safety Requirements Some of the worker health and safety requirements associ- ated with pavement marking material removal are reviewed in this section. These include exposure to noise, lead, hexava- lent chromium, silica, and asbestos. Health and safety aspects that are standard to construction and maintenance activities such as interaction with heavy machinery and traffic are not discussed. Exposure to Lead Worker exposure to lead is regulated under 29 CFR 1926.62 et seq. Regulation 29 CFR 1926.62(c)(1) establishes a permis- sible exposure limit (PEL) for lead at a maximum of 50 Âµg/m3 of air averaged over an 8 hr period. The PEL is measured as a function of what a worker may breathe in. The standard applies to: â¢ Demolition or salvage of structures where lead or materials containing lead are present; â¢ Removal or encapsulation of materials containing lead; â¢ New construction, alteration, repair, or renovation of struc- tures, substrates, or portions thereof, that contain lead, or materials containing lead; â¢ Installation of products containing lead; â¢ Lead contamination/emergency cleanup; â¢ Transportation, disposal, storage, or containment of lead or materials containing lead on the site or location at which construction activities are performed; and â¢ Maintenance operations associated with the construction activities described in this paragraph. For activities covered by the lead standard, the employer is required to perform an assessment of the exposure to lead
81 by collecting personal samples representing a full shift of work. Exposure to lead during removal of pavement marking materials could occur, depending on the type of removal pro- cess used and the type of material being removed. The con- centrations would vary, depending on the type of material being removed, the location, weather conditions, and type of removal process employed. The only pavement marking materials known to contain lead are yellow markings, where lead chromate has been used as a pigment. Hexavalent Chromium Occupational Safety and Health Administration (OSHA) regulation 29 CFR 1910.1026 et seq. regulates worker expo- sure to chromium (VI) in all forms and compounds in general industry, except: 1910.1026(a)(4) Where the employer has objective data demonstrating that a material containing chromium or a specific process, operation, or activity involving chromium cannot release dusts, fumes, or mists of chromium (VI) in concentrations at or above 0.5 Âµg/m3 as an 8-hour time-weighted average (TWA) under any expected conditions of use. Exposure to chromium (VI) during removal of pavement marking materials could occur if present in the marking material, depending on the type of removal process used. The concentrations would vary, depending on the type of material being removed, the location, weather conditions, and type of removal process employed. The only pavement marking materials known to contain chromium are yellow markings where lead chromate has been used as a pigment. Exposure to Silica and Asbestos OSHA regulation 29 CFR 1926.55, Appendix A, establishes threshold limit values (TLVs) for airborne contaminants for construction activities. Values include TLVs for seven silica compounds and six silicates (with less than 1 percent crystal- line silica). OSHA regulation 29 CFR 1910.1001(c) establishes a worker exposure limit to airborne asbestos of 0.1 fiber per cubic centi- meter of air as an 8-hr time-weighted average. The regulation identifies monitoring and other requirements associated with ensuring that this standard is met. For working environments where workers may be exposed to a TLV for silica or an asbestos exposure limit, monitoring and worker protection measures may be required. With respect to pavement marking products, the area of focus would be remov- ing marking materials (including glass beads) that may con- tain silica. Some removal processes (e.g., blasting or grinding) can generate dust from the marking materials and pavement. Forms of sand blasting may also use abrasive materials that may contain silica that would also need to be considered in the TLV along with the removed marking material and any removed road surface material that may become airborne. Noise Applying and removing traffic markings may require noise protection for exposed workers. The OSHA requirements for noise control and hearing conservation are set forth in 29 CFR 1910.95, Occupational Noise Exposure. This regula- tion establishes permissible noise exposures for short time periods (Â¼ hr or less) up to a full 8-hr day. Noise levels that exceed the permissible noise exposure levels require hearing protection, noise reduction, and in certain instances, hearing conservation programs. Table 56 indicates the permissible noise levels established in 29 CFR 1910.95(b). Environmental, Health, and Safety Issues Related to Specific Pavement Marking Removal Procedures The general environmental health and safety issues of pave- ment marking removal are discussed in the previous section. This section will look specifically at how these issues relate to specific forms of removal on specific road surfaces. Worker safety issues and the impact from the marking material removed will be similar for all road surfaces. Grinding Environmental and Worker Safety Considerationsâ Asphalt and Seal Coat Surfaces. Grinding can be used for removal of all pavement marking materials on asphalt. Solid waste generated from the removal process would include the Table 56. Permissible noise exposures.1 Duration per Day, Hours Sound Level, dBA Slow Response 8 90 6 92 4 95 3 97 2 100 1 Â½ 102 1 105 Â½ 110 Â¼ or less 115 1 When the daily noise exposure is composed of two or more periods of noise exposure of different levels, their combined effect should be considered, rather than the individual effect of each. If the sum of the following fractionsâC1/T1+C2/ T2Cn/Tnâexceeds unity, then the mixed exposure should be considered to exceed the limit value. Cn indicates the total time of exposure at a specified noise level, and Tn indicates the total time of exposure permitted at that level. Exposure to impulsive or impact noise should not exceed 140 dB peak sound pressure level.
82 marking material, asphalt and oil, and other contaminants on the asphalt surface. Asphalt contains aliphatic hydrocarbons in addition to the mononuclear aromatics and polycyclic aro- matic hydrocarbon (PAH) mixtures found in both asphalt and tars (Irwin et al. 1997). Waste material resulting from grinding will be subject to hazardous waste determination if it is suspected the waste has hazardous constituents. The waste should either be tested using the TCLP, or knowledge of the waste stream should be applied to make this determination. The results of this deter- mination will dictate how the waste should be disposed. It is possible for asphalt waste to create a hazard to aquatic life due to the PAHs and alkyl PAHs in asphalt that can move into the aquatic ecosystem from the breakdown of asphalt. However, the effects of the low concentrations of these con- taminants associated with asphalt to aquatic life or waterfowl are unknown. Hazards to humans associated with asphalt include inhalation of compounds in heated or fresh asphalt as well as ingestion of PAHs entering the food chain as the result of breakdown of asphalt. Asphalt can lower contaminant leaching rates by binding contaminants in the asphalt matrix. The amount the leaching is lowered depends on the physical and chemical character- istics of the particular environment. Chemical and physical actions on the asphalt can break it down. Greases can soften asphalt, while xylene and toluene can diffuse through it. Under certain conditions, solvents and road salts can accelerate the breakdown of asphalt. As the asphalt road surface wears away, road dust and other erosion components are a potential source of PAHs in the sediments of urban waterways. Asphalt wear products may be responsible for some of the petroleum in urban runoff as well as for some of the PAHs found in the sediments of some urban lakes. The chemical constituents in the pavement markings will be reflected in the grinding waste. A projection of the poten- tial contaminants can be made by reviewing the constituents listed in the product MSDS. Grinding can expose workers to contaminants contained in the dust particles, including lead, chromium, silica, and asbestos. Noise exposure can also be a concern. Environmental ConsiderationsâPCC Surfaces. The concrete waste material produced from grinding pavement markings on PCC pavement has a low environmental impact. The most notable impact is a potential increase in pH in sur- rounding soil if waste material is mixed in it. The primary impacts will be from the chemicals in the marking materi- als and other contaminants on the roadway surface. Waste ma terial resulting from grinding on PCC pavement will be subject to hazardous waste determination. The waste should either be tested using the TCLP, or knowledge of the waste stream should be applied to make this determination. The results of this determination will dictate how the waste should be disposed of. High-Pressure Water Blasting Environmental ConsiderationsâAsphalt and Seal Coat Surfaces. The waste water produced from high-pressure water blasting will wear away some of the asphalt surface, along with removing the marking material. The asphalt waste will present the same environmental concerns as grinding, but in varying quantities, and will be combined with water. High- pressure water blasting will result in minimal airborne con- taminants. Noise exposure is a concern. Environmental ConsiderationsâPCC Surfaces. High- pressure water blasting is effective in removing the pavement marking material while removing very little of the PCC pave- ment. The primary impacts will be from the chemicals in the marking materials. A projection of the potential contami- nants can be made by reviewing the constituents listed in the product MSDS. Media Blasting (shot or glass) Environmental ConsiderationsâAsphalt or Seal Coat Surfaces. Environmental considerations for removing pave- ment markings with media blasting are similar to grinding. In addition to waste from the asphalt pavement and pavement marking, there will be waste material from the medium (shot or glass) being used, unless the medium is dry ice. Waste material resulting from media blasting on asphalt will be subject to haz- ardous waste determination. The waste should either be tested using the TCLP, or knowledge of the waste stream should be applied to make this determination. The results of this determi- nation will dictate how the waste should be disposed of. Media blasting can expose workers to contaminants contained in the dust particles, including lead, chromium, silica, and asbestos. Noise exposure can also be a concern. Environmental ConsiderationsâPCC Surfaces. The concrete waste produced from media blasting pavement markings on PCC pavement has a low environmental impact. The most notable impact is a potential increase in pH in sur- rounding soil if waste material is mixed in. The primary impacts will be from the chemicals in the marking materials and the medium itself. Waste material resulting from media blasting on PCC pavement will be subject to hazardous waste determination. The waste should either be tested using the TCLP, or knowledge of the waste stream should be applied to make this determination. The results of this determination will dictate how the waste should be disposed of.
83 Chemical System Chemical systems would only be used on paint. There are some paint systems designed specifically to be removed with a chemical system. Environmental ConsiderationsâAsphalt Surfaces. Chem ical systems can be used on asphalt but are less effec- tive on porous asphalt surfaces. An assessment of the envi- ronmental considerations should begin with a review of the MSDS for the chemical remover. Waste material will include chemicals from the remover, pavement marking material, and contaminants on the roadway surface. Waste material resulting from chemical removal on asphalt will be subject to hazardous waste determination. The waste should either be tested using the TCLP, or knowledge of the waste stream should be applied to make this determination. The results of this determination will dictate how the waste should be disposed of. Worker safety issues will center on handling the chemicals and exposure to waste material after removing the pavement marking. Environmental ConsiderationsâPCC Surfaces. As with use on asphalt, an assessment of the environmental considerations should begin with a review of the MSDS for the chemical remover. Waste material will include chemicals from the remover, pavement marking material, and contam- inants on the roadway surface. Waste material resulting from media blasting on PCC pavement will be subject to hazard- ous waste determination. The waste should either be tested using the TCLP, or knowledge of the waste stream should be applied to make this determination. The results of this deter- mination will dictate how the waste should be disposed of. Summary A summary of the environmental issues associated with the pavement marking removal methods under consider- ation is shown in Table 57. Recommended Best Practices for Management of Environmental and Worker Safety Issues The potential adverse impacts on the environment and on workers can be minimized by the application of BMPs. Best management practices for removal of pavement markings include the following: â¢ Selecting the appropriate removal method for the job (i.e., road surface, pavement marking, etc.). â¢ Assessing potential VOC, lead, chromium, silica, asbestos, or other chemical hazards and addressing such hazards in accordance with regulatory requirements. â¢ Developing a plan that manages: â the removal of waste products that complies with appli- cable environmental regulatory requirements, and â airborne particles, material spills, and disposal. A representative series of TCLP tests should be conducted on the waste products if there are questions that waste ma terial from any of the pavement marking application or removal processes may contain toxic wastes (as defined by EPA or state regulations). Worker exposure to lead, chromium, silica, or asbestos would be in the form of an inhalation hazard. This would Table 57. Summary of environmental issues related to removal techniques. Removal Techniques Hazardous Waste & TSCA CWA CAA NEPA Grinding Solid waste generated subject to regulation Water runoff from waste products subject to regulation Airborne material produced subject to regulation Site-specific determination of requirements High-Pressure Water Blasting Solid waste and wastewater generated subject to regulation Water runoff from waste products subject to regulation Limited air quality concerns Site-specific determination of requirements Media Blasting Solid waste generated subject to regulation Water runoff from waste products subject to regulation Airborne material produced subject to regulation Site-specific determination of requirements Chemical Removal* Solid and chemical waste generated subject to regulation Water runoff from waste products subject to regulation Limited air quality concerns Site-specific determination of requirements Combination Grinding & Chemical Removal Solid and chemical waste generated subject to regulation Water runoff from waste products subject to regulation Airborne material produced subject to regulation Site-specific determination of requirements *Chemical removal currently is only used on paint markings.
84 normally only occur during removal of material containing lead, chromium, silica, or asbestos. The following factors should be considered when assessing the potential lead or chromium exposure hazard: â¢ The amount of contaminant in the materials being removed. â¢ Whether the removal activity is being conducted in a con- fined area (such as a tunnel) or an open area. â¢ The type of removal process being used and its potential for creating an inhalation hazard for the contaminant. If there are concerns that the exposure limits for lead, chro- mium, silica, or asbestos might be approached, then OSHA procedures for sampling and monitoring the potential expo- sure should be followed. Temporary Tape Pavement Markings The masking of permanent markings using temporary tape markings or using temporary tape markings as a form of delineation have been identified as practices used in work zones. The durability of these markings and the remnants they leave behind when removed are key factors to consider when deciding to implement this type of marking. Tempo- rary tape pavement markings have frequently been included in AASHTOâs National Transportation Product Evaluation Program (NTPEP 2011). This program uses test decks around the country to evaluate pavement marking materials. Because of the quantity of data in the NTPEP database that is available for anyone to review, the research team elected to review the NTPEP data and use the results to further this study. These results allow for recommendations into the use of temporary tape markings and ways that the NTPEP data- base can be used to help identify the best materials for usage. NTPEP Database NTPEP DataMine 1.0 was used as the source of temporary tape pavement marking data (NTPEP 2011). All years with available temporary tape data at the time of the analysis were included in the evaluation (2000â2009). In total, there were 11 test decks that had temporary pavement marking materi- als installed on them. For temporary (removable and non- removable) tapes, the markings were evaluated monthly for 6 months. Every month, one longitudinal and one transverse stripe of each removable tape were removed for evaluation. The data evaluated in this report only looked at the longi- tudinal markings. The types of data collected during the evaluations included quantitative measures of reflectivity and color, subjective ratings of durability, and subjective ratings of remova bility, discernability, and other perfor- mance factors of the temporary tapes. The durability, color, and retroreflectivity of the temporary tape markings are an important aspect to consider when selecting the marking but are not discussed in this evaluation. This evaluation focused on the removability and discernability of these temporary tape markings. The subjective ratings during NTPEP evaluations are made by a team of trained raters. Pull-up tests are performed for test- ing removability, which is rated based on how many pieces have to be removed for complete removal (internal tape strength), how much effort is required to remove tape (adhesive bond), and presence of residual adhesive to road surface (tackiness). Subjective discernability ratings after removal are about the outline and image of remaining adhesive, dirt, etc., left on a road surface right after removal and 30 days after removal. The rating criteria as specified in the NTPEP best practices document are as follows (NTPEP 2005): The rating for internal tape strength with the rating scale 1â10 is as follows: â¢ 1âTape removed intact, in one piece. â¢ 3âTape removed in three to four pieces. â¢ 5âTape removed in five pieces. â¢ 7âTape removed in seven pieces. â¢ 10âTape only removed in very small fragments. The rating for adhesive bond with the rating scale 1â10 is as follows: â¢ 1âTape removed easily (potentially by one hand). â¢ 3âTape removed with moderate, two-handed effort. â¢ 5âTape removed with significant, two-handed effort, requiring multiple pulls. â¢ 9âTape removed only by exhausting, two-handed effort. â¢ 10âTape could not be removed from surface. The rating for tackiness with the rating scale 0â10 is as follows: â¢ 0âLeast adhesive remaining on the pavement surface. â¢ 10âMost adhesive remaining on the pavement surface. The rating for discernability after removal with the rating scale 0â10 is as follows: â¢ 0âNo discernible marking on road surface. â¢ 5â50 percent of marking (adhesive outline) left on road surface. â¢ 10â100 percent of marking left on road surface. NTPEP Evaluation The research team extracted all of the available data on the temporary pavement markings from the NTPEP DataMine
85 (NTPEP 2011). The data from each of the 11 test decks were combined to make one data set for each evaluation criteria. The data sets were further divided by road surface (asphalt or concrete) and by marking color (white, yellow, or black). The results of the evaluation showed that the white and yellow markings performed similarly, so only the white and black markings will be discussed. Each of the figures in this section plots the average rating of all the markings across all the test decks for the given evalu- ation period after installation in months. In addition to the average value, error bars representing, in total, one standard deviation are also included. The figures are differentiated by the given evaluation criteria, the given road surface, and the given marking color. Figure 46 provides the summary of the internal strength data for white markings on asphalt and concrete surfaces. The average strength ranged between 1.6 and 3.5 for the two sur- faces. On the asphalt surface, the average value increased as the marking aged, which actually indicates the marking broke up into more pieces as it was removed. There was no evident trend on the concrete surface. These data are useful in that it would be preferable to have a marking that removes in as few pieces as possible. Figure 47 provides the summary of the adhesive bond data for white markings on asphalt and concrete surfaces. The average adhesive bond ranged between 2.6 and 4.9 for the two surfaces. On the asphalt surface, the average value gener- ally increased as the marking aged, which indicates the mark- Figure 46. Internal strength, white pavement markings. 0 1 2 3 4 5 6 7 8 9 10 1 2 3 4 5 6 Ra ti ng Months After Application On Asphalt On Concrete Figure 47. Adhesive bond, white pavement markings. 0 1 2 3 4 5 6 7 8 9 10 1 2 3 4 5 6 Ra ti ng Months After Application On Asphalt On Concrete
86 ing was more difficult to pull up. There was no evident trend on the concrete surface, but the average values overall were higher than on the asphalt surface. These data are useful in that it would be preferable to have a marking that is easier to remove, but the trade-off may be durability. Figure 48 provides the summary of the tackiness data for white markings on asphalt and concrete surfaces. The average tackiness ranged between 2.0 and 3.6 for the two surfaces. On the asphalt surface, there was no trend as the marking aged. On the concrete surface, the trend was generally decreasing, indicating less adhesive remaining on the road surface as the marking aged. These data are useful in that it would be pref- erable to have a marking that leaves as little adhesive on the roadway as possible. Figure 49 provides the summary of the discernability data for white markings on asphalt and concrete surfaces imme- diately after removal. The average discernability imme- diately after removal on asphalt ranged between 3.5 and 6.2 and between 5.1 and 6.8 on concrete. In general, the longer the material was installed, the more discernible it was after removal. Overall, the discernability on concrete was higher than on asphalt immediately after removal. These data are useful in that it would be preferable to have a mark- ing that leaves the least discernible marking on the roadway after removal. Figure 50 provides the summary of the discernability data for white markings on asphalt and concrete surfaces 30 days after removal. The average discernability 30 days after removal on Figure 48. Tackiness, white pavement markings. 0 1 2 3 4 5 6 7 8 9 10 1 2 3 4 5 6 Ra ti ng Months After Application On Asphalt On Concrete Figure 49. Discernability after removal, white pavement markings. 0 1 2 3 4 5 6 7 8 9 10 1 2 3 4 5 6 Ra ti ng Months After Application On Asphalt On Concrete
87 asphalt ranged between 3.0 and 5.9, and between 4.1 and 7.9 on concrete. Overall, the discernability on concrete remained higher than on asphalt 30 days after removal. In general, the longer the material was installed, the more discernible the material was 30 days after removal. The 30 days after removal values on asphalt were lower than the immediately after removal values, and the decrease ranged from 0 to 2.0 rating points. The 30 days after removal values on concrete were lower than the values immediately after removal, and the decrease ranged from 0.3 to 1.3 rating points. The only excep- tion was the removal on the concrete 6 months after instal- lation. In the 30 days after removal evaluation, only about half of the products had data recorded compared to the data immediately after removal. This reduced data set may be the reason that the evaluation 30 days after removal resulted in a higher value than immediately after removal. These data are useful in that it would be preferable to have a marking that leaves the least discernible marking on the roadway 30 days after removal. Figure 51 provides the summary of the discernability data for black markings on asphalt and concrete surfaces imme- diately after removal. The average discernability on asphalt ranged between 5.1 and 7.4 immediately after removal, and on concrete, it ranged between 5.2 and 9.1 immediately after removal. In general, the removed markings were more dis- cernible on concrete than asphalt. Figure 50. Discernability 30 days after removal, white pavement markings. 0 1 2 3 4 5 6 7 8 9 10 1 2 3 4 5 6 Ra ti ng Months After Application On Asphalt On Concrete Figure 51. Discernability after removal, black pavement markings. 0 1 2 3 4 5 6 7 8 9 10 1 2 3 4 5 6 Ra ti ng Months After Application On Asphalt On Concrete
88 Figure 52 provides the summary of the discernability data for black markings on asphalt and concrete surfaces 30 days after removal. The average discernability ranged between 3.6 and 4.9 on asphalt 30 days after removal and between 5.3 and 7.2 on concrete 30 days after removal. On asphalt, the values 30 days after removal were lower than the values immediately after removal, and the decrease ranged from 0.7 to 3.8 rating points. On concrete, the values 30 days after removal were lower than the values immediately after removal, and the decrease ranged from â0.4 to 2.0 rating points. The increase at the 30-day evaluation period was due to some markings not being evaluated at the 30-day period. This was common for the white markings as well, but there were fewer black markings, so some missing data had a larger impact on the results. The information provided here is a summation of some of the information provided in the NTPEP database. Further exploration of the NTPEP database would allow for more specific information to be evaluated that may be beneficial to a particular set of conditions. Users should evaluate the tem- porary tapes they want to use to select the most durable, the least discernible, or a material that is the best combination of the two. In addition, other factors such as cost, color, and removability need to be taken into consideration. Masking of Markings and Blending of Removal Areas The masking of markings and blending of removal areas have been identified as practices used when conducting pave- ment marking removal. The durability and color-matching characteristics of the masking material that is applied over the marking are critical to being able to effectively remove (cover) the marking. In situations where a marking is removed, it may be advantageous to attempt to blend in the removal area with the surrounding pavement in order to reduce the confusion caused by scarring or changes in surface color or texture. Beyond masking markings or blending in removed areas, the entire road or lane width can be resurfaced to cover the markings that need to be removed. These areas of pavement marking removal are discussed in this section. Masking Markings Using Surface Treatments Surface treatments can be used as a method to cover mark- ings or to blend areas where markings have been removed. A surface treatment may just cover the area where the mark- ing is or cover the entire road surface. Surface treatments are typically used for rehabilitation and preservation of aging asphalt roadways. For PCC roadways, diamond grind- ing could be used across the entire traveled lane. Diamond grinding is typically used to correct surface irregularities or to improve surface friction. Diamond grinding on PCC typi- cally costs $1.70â$10.00/sq yd (Correa and Wong 2001). Any use of a surface treatment or full road width grinding to mask markings or to blend removed markings needs to consider the following: â¢ Are there changes in friction (skid) characteristics to the road surface? â¢ Will the treatment be an interim or final surface? â¢ If not covering the entire road width, will the treatment area match the surrounding roadway color and texture? Figure 52. Discernability 30 Days after removal, black pavement markings. 0 1 2 3 4 5 6 7 8 9 10 1 2 3 4 5 6 Ra ti ng Months After Application On Asphalt On Concrete
89 â¢ Will the underlying markings be removed or remain in place? â¢ Based on the expected service life of the surface treatment and markings left in place, could the markings begin to show through prior to installing a new road surface? Several of the more common surface treatment methods are discussed herein. The discussion includes the general nature of the surface treatments and how they can be used in conjunc- tion with the need to remove pavement markings or to blend removed areas. Estimated costs are also discussed so that the costs of covering the markings can be compared to removing the markings (Morian 2011, Wu et al. 2010, Yamada 1999). An advantage for all the surface treatments is that if they are used across the entire roadway or lane width, there will not be any color difference, and differences in surface characteristics will be minimal. The uniform color and surface texture of a new surface treatment will allow for improved delineation of the roadway and less confusion to drivers. Fog Seals. A fog seal is a light application of a diluted slow-setting asphalt emulsion to the surface of an aged pave- ment surface with no additional aggregate added. Fog seals are low cost and are used to seal and rejuvenate deteriorat- ing pavement surface. Fog seals are also used on new chip seal surfaces to reduce early stone loss. Fog seals were men- tioned in several surveys as a means to blend in removed areas with the surrounding pavement so that scarring is less evident. Fog seals would not be used to cover markings, per the MUTCD, but rather as a means of blending removed areas with the surrounding pavement. Literature showed costs at $0.45/sq yd (Yamada 1999), $1,029â211,579/lane-mi ($0.14â30.05/sq yd) (Wu et al. 2010), and $1,000â3,500/lane- mi ($0.14â0.50/sq yd) (Morian 2011). Slurry Seals. A slurry seal is a mixture of emulsified asphalt, water, well-graded fine aggregate, and mineral filler that has a creamy fluid-like appearance when applied. Slurry seals are used to fill existing pavement surface defects, to pro- vide a uniform surface, and to prevent moisture and air intru- sion. Slurry seals can also be used to improve or restore skid resistance. There are three basic aggregate gradations used in slurry seals: fine, general, and coarse. Literature showed costs at $1.20/sq yd (Yamada 1999), $26,505â32,542/lane-mi ($3.76â4.62/sq yd) (Wu et al. 2010), and $4,900â10,600/lane-mi ($0.70â1.51/sq yd) (Morian 2011). Microsurfacing. Microsurfacing is an advanced form of slurry seal that uses the same basic ingredients as slurry seals and combines them with advanced polymer additives. It is useful for sealing pavement surfaces and for providing improved friction characteristics. Literature showed costs at $1.50/sq yd (Yamada 1999), $19,463â32,698/lane-mi ($2.76â 4.64/sq yd) (Wu et al. 2010), and $1,000â34,100/lane-mi ($0.14/sq ydâ4.84/sq yd) with an average of $12,600/lane-mi ($1.79/sq yd) (Morian 2011). Chip or Sand Seal. Chip seals are also known as seal coat and are a thin protective wearing surface that is applied to a pavement or base course. The size or type of aggregate dis- tinguishes chip seal from sand seal. The aggregate for chip seal can be crushed stone, gravel, or slag; the aggregate for sand seal can be either natural sand or rock screenings. Chip seals are generally used to improve the skid resistance of pavement surfaces and to improve the surface seal by filling cracks and voids to prevent water intrusion. Many chip seals are often followed by a fog seal to help fill voids and to lock in any loose aggregate. Literature showed single chip seal costs at $1.20/sq yd (Yamada 1999), $6,732â145,976/lane-mile ($0.96â 20.70/sq yd) (Wu et al. 2010), and $3,900â12,300/lane-mile ($0.55â1.75/sq yd) with an average of $7,460/lane-mile ($1.06/ sq yd) (Morian 2011). Literature showed sand seal costs at $0.70/sq yd (Yamada 1999) and $4,900/lane-mile ($0.70/sq yd) (Morian 2011). Studies in Florida (Ellis et al. 2010, Ellis 2003) investigated pavement marking eradication alternatives that masked or covered pavement markings with an inexpensive surface treatment. The estimated installation costs were $0.47â1.15/lf ($1.03/sq yd) for a modified sand seal coat. This was assum- ing covering one travel lane and one marking. If multiple markings were covered, the unit costs would be even lower. While the study period with regard to durability was short, at 30 days, the method proved effective. Friction char- acteristics of the modified sand seal coat were deemed acceptable. Figure 53 shows an example of using a surface treatment to cover markings on an HMA road surface. The area of road was converted from two lanes in the same direction to a merge area before entering the realigned roadway. Images a and b were taken approximately 2 years after installation. The markings are mostly covered, but the surface treatment does not match the color of the surrounding road surface very well. The 2-ft width of the surface treatment may help reduce confusion due to the different colored surfaces. Images c and d were taken approximately 9 months after images a and b. The loss of the surface treatment material over time has exposed much of the marking below and reduced the color differen- tial between the surrounding road and the surface treatment. This area will now need to have the markings removed or a new surface treatment added. To avoid issues like this, a surface treatment that would last until the road was to be resurfaced should have been used, or the markings could have been removed and the areas blended with the surface treatment. Over time, any scarring or discoloration from the
90 removal would become less evident as the surface treatment wore away. Masking Markings Using Marking Materials In some instances where markings only need to be removed for a short period of time, it may be beneficial to just cover the markings instead of removing them. By covering the markings using a temporary removable tape, there will be no damage to the underlying road surface, and after removal of the tem- porary pavement marking, the original marking may still be usable. Based on the survey responses, black tape on asphalt surfaces is the most common form of temporary tape used to mask markings. The use of âremovable, non-reflective, pre- formed tape that is approximately the same color as the pave- ment surface may be used where markings need to be covered temporarilyâ is allowed by the MUTCD (FHWA 2009). Being that temporary marking tapes used for masking are typically only available in black, a major problem arises when the pavement surface is not black. The black marking will only work for newer asphalt road surfaces, not aged and faded asphalt or concrete. If the black masking material is used on a lighter-colored surface, the black marking will be notice- able and could be confusing and mistaken for delineation. A Figure 53. Surface treatment masking example. a) Surface treatment masking b) Close-up of marking and surrounding area c) 9 months later d) Close-up 9 months later
91 means of counteracting this would be to produce tapes of dif- fering shades to better match road surfaces. The smaller pro- duction quantities of these types would greatly increase the costs, but the results could be much better. Studies in Florida (Ellis et al. 2010, Ellis 2003) found that 8-inch wide tempo- rary black tape costs ranged between $1.83â1.97 installed per foot for small quantities. There is at least one effort underway to design a pavement marking tape that will be able to match the surface color of a roadway better. A mottling technique using shades of gray to better match colors is being developed. The technique is currently being developed by SBS Systems, LLC under Pat- ent Application #61/572,895. The concept if issued would be made available to all producers of pavement marking tapes. Figure 54 represents an image of some of the prototype mark- ings being developed. It is clearly evident that the marking in the middle much more closely matches the surfaceâs color than the standard black marking. According to the MUTCD, âPainting over existing pave- ment markings with black paint or spraying with asphalt shall not be accepted as a substitute for removal or oblitera- tionâ (FHWA 2009). The tape is allowable for temporary situ- ations where the underlying markings will be reused. It is not allowable, though, to paint or spray asphalt over a marking in a temporary (the underlying markings would no longer be usable) or permanent application. The concern is that the underlying marking will eventually wear through the cover- ing marking, resulting in a traffic hazard. In addition, the underlying marking wearing through the covering material may not match the road surface color adequately to start with or over time. Since road surfaces and marking materials dete- riorate at different rates, even a good initial color match may not last for long. Even though this technique is not acceptable according to the MUTCD, several instances of this occurring have been viewed around the country. Figure 55 shows a black non-tape marking material being used to permanently mask the underlying white material where lane lines were not placed in the proper location after a new road surface was installed. The color difference between the black marking and the asphalt road surface is very noticeable. Some of the white marking is also beginning to be exposed along the edges, which is a reason why the MUTCD does not allow this practice for permanent situations. Figure 1c showed both lane lines and a center gore area marking being covered by a black non-tape marking material. This is likely not a per- manent application due to the ongoing work that will likely include a new final surface layer. According to the MUTCD, this practice is not acceptable, but for a situation such as this, as long as the non-tape pavement markings are maintained, it should be allowable. Blending Removed Markings When markings are removed, the removed area may be dis- colored from the surrounding pavement and may also have different surface characteristics that reflect light differently than the rest of the surface. This discoloration and change in surface characteristics may result in confusing the removed area with an actual marking. To counteract this, the removed area could be blended into the surrounding pavement using surface treatments or other materials to match the color of the surface. Several surveys indicated the use of fog seals to blend marking removal with the surrounding surface on asphalt roadways. The fog seal could be used across the entire roadway so that as the fog seal ages, the entire road surface would remain the same color. The black color of the fog seal Figure 54. Various versions of preformed tape with a mottled color (SBS Systems 2011). Figure 55. Black marking material covering old marking.
92 would not be a viable option on concrete road surfaces. On concrete surfaces or asphalt surfaces where a fog seal is not viable, color-matching paint or mottling colors like the tape in the previous section would be viable options. There are currently no paint pavement marking systems that are specifically designed for color-matching road sur- faces. Black paint can be used by itself or blended with white paint until the color matches as best as possible. A solid color may also not match the road surface very well, as there are typically many colors in a road surface. Using a mottling technique with paints of different colors may yield the best color-matching results. Road surfaces and paints age at dif- ferent rates, so a good match initially may not be good for long, which is a drawback of blending in a small area around the marking. A small scale test was conducted as part of this research to see if mottling paint could produce a color-matching coating that reduced the discernability of the color difference between the removed area and the surrounding pavement. The con- crete surface that some of the markings were removed from was relatively dark, and after removal, a large color difference was evident. Two colors of paint representing colors within the pavement surface were produced in spray paint cans for ease of application in the test. The material sprayed was not a pavement marking paint, so its durability was unknown, but this was not a concern since it was for demonstration pur- poses. Standard pavement marking paint could be dyed in a similar fashion. The paints were sprayed in a mottled fashion along approximately 3 ft of the removed area. Figure 56 provides images of a removed marking area with and without blending. The removal method used was grinding, which caused the top surface of the concrete to appear much lighter in color than the surrounding surface (see Figure 56a). After using the two colors of paint to blend in the area, the color difference was much less noticeable (see Figure 56b). Though not perfectly blended in with the surrounding road surface, the blended area is much less noticeable than the area without blending. Figure 57 provides another set of images of a removed mark- ing area with and without blending. The removal method used was water blasting, which cleaned the top surface of the con- crete, resulting in a lighter-colored surface than the surround- ing surface (see Figure 57a). This color difference was not as great as it was for the grinding, but it was still very noticeable. After using the two colors of paint to blend in the area, the color difference was much less noticeable (see Figure 57b). Though not perfectly blended in with the surrounding road surface, the blended area is much less noticeable than the area without blending. Blending of removed areas using fog seals or color-matching paint, especially when mottled, can be an effective means to hide scarring or discoloration caused by pavement marking removal, at least in the short term. The long-term impacts depend on the durability of the materials used for blending, the difference in aging of the blending materials compared to the road surface, and the natural blending over time of the removed area with the surrounding area. b) With Blending a) Without Blending Figure 57. Water blasting on concrete, looking away from sun. a) Without Blending b) With Blending Figure 56. Grinding on concrete, looking away from sun.