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10 its cost to determine if that combination of performance and TABLE 2 Typical pavement cost is acceptable. This information will also help compare dif- preventive maintenance treatments ferent alternatives for reaching similar objectives. If adequate 1. Bituminous-Surfaced Pavements information about treatment performance is not readily avail- Crack Filling/Crack Sealing able, agencies are strongly encouraged to generate preventive Fog Seals Slurry Seals maintenance treatment performance data based on their own Scrub Seals experience. In the interim, data required to perform certain Microsurfacing analysis may be obtained from other sources, such as "expert" Chip Seals Thin Overlay opinion or other agencies with comparable conditions. Ultrathin Friction Courses 2. Concrete-Surfaced Pavements Joint/Crack Sealing Customer Satisfaction Diamond Grinding Undersealing There is a growing emphasis in highway agencies to pur- Load Transfer Restoration sue actions that improve customer satisfaction. Some of the 3. Maintenance of Drainage Features attributes of interest to the traveling public include noise, roughness, absence from splash and spray, and traffic dis- ruptions from road repairs. Different treatments affect these cost of each treatment. Because the expected life estimates attributes in different ways, and an agency interested in improv- ing customer satisfaction will consider these factors in the reported in these tables are based on the use of the treatment treatment selection process. in both a preventive and reactive manner, there is a broad range for some of the reported lives. The costs also cover a wide range of applications and regional variations; users are encouraged to identify local, and more recent values for use Characteristics of Selected Treatments in the analysis. A list of pavement treatments that meet the definition of "preventive" maintenance is shown in Table 2; characteris- Overview of Treatments for tics of treatments for bituminous- and concrete-surfaced Bituminous-Surfaced Pavements pavements are presented in Tables 3 through 14 and mainte- nance of drainage features are shown in Table 15. This infor- With the exception of crack filling and crack sealing, mation includes estimates of the expected life and typical treatments described in this section consist of a thin, uniform TABLE 3 Characteristics of crack filling and crack sealing CRACK FILLING AND EVALUATION FACTORS CRACK SEALING Climate Traffic Conditions Addressed Contraindications Description: These treatments Treatment can Performance is not Functional/Other Structural failure (i.e., are intended primarily to prevent perform well in all significantly affected by extensive fatigue Longitudinal cracking the intrusion of moisture through climatic conditions. varying ADT or truck cracking or high existing cracks. Crack sealing However, sealants levels. Minor block cracking severity rutting) refers to a sealant operation that perform best in dryer Transverse cracking Extensive pavement addresses "working" cracks, i.e., and warmer deterioration, little those that open and close with environments that do Structural remaining life changes in temperature. It not undergo large Adds no structural benefit, typically implies high quality daily temperature but does reduce moisture materials and good preparation. changes. infiltration through cracks. Crack filling is for cracks that Only practical if the extent undergo little movement. Sealants of cracking is minimal and if used are typically thermo-plastic there is little to no structural (bituminous) materials that soften cracking. upon heating and harden upon cooling. Site Restrictions None. Construction Considerations Placement should be done during cool, dry weather conditions. Proper crack cleaning is essential to a good bond and maximum performance. Some agencies also use hot compressed air lance prior to sealing. Expected Life 2 to 6 years. Typical Costs $1.00 to $5.00 per linear m ($0.30 to $1.50 per linear ft) for crack sealing, including routing; $1.00 per linear m ($0.30 per linear ft) for crack filling. Costs are slightly higher for small jobs.

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11 TABLE 4 Characteristics of fog seals EVALUATION FACTORS FOG SEALS Climate Traffic Conditions Addressed Contraindications Description: Fog seals are Treatment performs well in Increased ADT or truck Functional/Other Structural failure (such placed primarily to seal the all climatic conditions. levels can increase surface Longitudinal, as significant fatigue pavement, inhibit raveling, Actual performance will wear, particularly in states transverse, and block cracking) enrich the hardened/ vary according to factors that permit studded tires. cracking (M) Flushing/bleeding (M) oxidized asphalt, and that affect weathering and Raveling/weathering Friction loss (M-H) provide some pavement raveling of bituminous (loose material must be Thermal cracking (H) edge-shoulder delineation. surfaces. removed) Fog seals are very light Asphalt aging, applications of a diluted oxidation and asphalt emulsion placed hardening directly on the pavement Moisture infiltration surface with no aggregate. Typical application rates Structural range from 0.23 to 0.45 liters per m2 (0.05 to 0.10 Adds no structural benefit, 2 gal per yd ). but can help reduce moisture infiltration through fatigue cracks (if their severity is low) Site Restrictions Not appropriate for surfaces with poor skid resistance, as it will lower the skid resistance even more. Construction Typically, a slow-setting emulsion is used which requires time to "break," the pavement is sometimes closed for 2 Considerations hours for curing before being re-opened to traffic. Expected Life 1 to 2 years when placed in a preventive maintenance mode. 2 Typical Costs $0.36 to $0.54 per m2 ($0.30 to $0.45 per yd ) of pavement surface area. Note: L, M, and H define level of distress (L for low, M for medium, and H for high). TABLE 5 Characteristics of slurry seals EVALUATION FACTORS SLURRY SEALS Climate Traffic Conditions Addressed Contraindications Description: A mixture of Treatment performs Performance in terms Functional/Other Structural failure well-graded aggregate (fine effectively in all of surface wear is Transverse, longitudinal and (such as significant sand and mineral filler) and climatic conditions. affected by increasing block cracking (L) fatigue cracking asphalt emulsion that is spread However, best ADT and truck traffic Raveling/weathering (loose and deep rutting) over the entire pavement performance occurs levels. material must be removed) Thermal cracking surface with either a squeegee in warm climates (H) with low daily Asphalt aging, oxidation and or spreader box attached to the Slurry mix properties Can accelerate the temperature changes. hardening back of a truck. It is effective (i.e., aggregate development of in sealing low-severity surface Friction loss quality, gradation and stripping in cracks, waterproofing the emulsion content) can Moisture infiltration susceptible HMA pavement surface, and be modified to pavements improving skid resistance at accommodate the Structural speeds below 64 km/h (30 higher traffic Adds no structural capacity; mph). Thickness is generally volumes. however, can temporarily seal less than 10 mm (0.4 in.). cracks (if severity is low) or serve as a rut-filler (if the ruts are not severe and are stable) Site Restrictions Pavement is often closed for several hours to allow the emulsion to cure. Construction Considerations Surface must be clean. Aggregates must be clean, angular, durable, well-graded, and uniform (prefer 100% crushed). Avoid placement in hot weather (potential flushing problems) and premature opening to traffic. Do not place when freezing temperatures are expected. Expected Life 3 to 5 years when placed in a preventive maintenance mode. 2 2 Typical Costs $0.84 to $1.14 per m ($0.70 to $1.00 per yd ). Additional Information Three slurry types with different aggregate gradations and application rates are used: Type I for lower traffic 2 2 2 2 volume (3.3 to 5.4 kg/m [6.1 to 10.0 lb/yd ]) Type II for heavy traffic (5.4 to 8.1 kg/m [10.0 to 15.0 lb/yd ]) 2 2 and Type III for irregular surfaced pavements (8.1 kg/m [15.0 lb/yd ]). Note: L, M, and H define level of distress (L for low, M for medium, and H for high).

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12 TABLE 6 Characteristics of scrub seals EVALUATION FACTORS SCRUB SEALS Climate Traffic Conditions Addressed Contraindications Description: A four-step Can be effective in all Good performance has Functional/Other Structural failure (such process intended to rejuvenate climates, but works been observed on lower- Transverse, longitudinal as significant fatigue the asphalt surface and to fill best in hot, arid volume roads (less than and block cracking (L) cracking) voids and surface cracks: climates. 7,500 ADT) Raveling/weathering Thermal cracking (H) (1) application of a layer of (loose material must be polymer-modified asphalt removed) emulsion that is broomed into the Moisture infiltration voids and cracks of the pavement, (2) application of sand Structural or small-sized aggregate, (3) a second application of polymer- Adds no structural capacity; modified asphalt (by brooming), however, can help seal cracks and (4) rolling with a pneumatic- (if severity is low) tired roller. Site Restrictions Do not apply on tight surfaces as this may reduce skid resistance of the pavement. Construction Considerations Surface must be clean; special equipment is required for brushing. Expected Life 1 to 3 years when placed in a preventive maintenance mode. 2 2 Typical Costs $0.90 to $1.49 per m ($0.75 to $1.25 per yd ). Additional Information Generally easy to apply and relatively inexpensive. Note: L, M, and H define level of distress (L for low, M for medium, and H for high). TABLE 7 Characteristics of microsurfacing EVALUATION FACTORS MICROSURFACING Climate Traffic Conditions Addressed Contraindications Description: Microsurfacing Effective in all Very successful on Functional/Other Structural failure (i.e., consists of a mixture of climate conditions. both low- and high- Longitudinal and transverse extensive fatigue polymer-modified emulsified However, best volume roadways. cracking (L) cracking) asphalt, mineral aggregate, performance occurs Raveling/weathering (loose Extensive pavement mineral filler, water, and in warm climates material must be removed) deterioration, little additives applied in a process with low daily remaining life Bleeding (L-M) similar to slurry seals. Used temperature changes. Thermal cracks (H) primarily to inhibit raveling May not set up Roughness (L) Friction loss Can accelerate the and oxidation of the pavement quickly if applied in development of surface. Also effective at cool climates. Moisture infiltration stripping in susceptible improving surface friction, and HMA pavements filling minor irregularities and Structural wheel ruts (up to 40 mm [1.6 Adds limited structural capacity. in.] deep) in one pass. Temporarily seals fatigue cracks (if severity is low) and can serve as a rut-filler (if the existing ruts are stable) Site Restrictions None. Construction Considerations Avoid placement in hot weather if there is potential for flushing problems. Placement in cool weather can lead to early raveling, not to be placed when freezing temperatures are expected. Expected Life 4 to 7 years when placed in a preventive maintenance mode. 2 2 Typical Costs $1.05 to $2.00 per m ($0.90 to $1.70 per yd ). Additional Information Typical mix proportions: 82 to 90% aggregate, 1.5 to 3.0% mineral filler, and 5.5 to 9.5% residual asphalt. Note: L, M, and H define level of distress (L for low, M for medium, and H for high). treatment applied to the pavement surface. If unsealed, the lay; they cover the pavement surface without a structural con- surface bituminous material loses volatiles as it is exposed tribution. Corrective measures, such as crack filling or crack to environmental forces, dries out, becomes brittle, begins to sealing, can also improve long-term performance by keeping lose aggregate (raveling), and cracks. Thin surfacings seal the pavement structure free from moisture infiltration, which the pavement surface slowing the aging process of the sur- otherwise could contribute to weakening the pavement. Addi- face materials. These surfacings range from a fog seal (an tional characteristics of each of these treatments are summa- asphalt emulsion without any aggregate) to a thin HMA over- rized in Tables 3 through 11.

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13 TABLE 8 Characteristics of chip seals EVALUATION FACTORS CHIP SEALS Climate Traffic Conditions Addressed Contraindications Description: Asphalt Treatment With proper design Functional/Other Structural failure (i.e., (commonly an emulsion) is performs well in and placement, chip Longitudinal, transverse and block extensive fatigue applied directly to the all climatic seals can perform cracking cracking and/or deep pavement surface (1.59 to 2.27 conditions. well on high-volume Raveling/weathering (loose rutting) L/m 2 [0.35 to 0.50 gal/yd2]) roads. surface material must be removed) Thermal cracking (H) followed by the application of However, use is Extensive pavement Friction loss aggregate chips (8 to 27 kg/m2 primarily limited to deterioration, little or [15 to 50 lb/yd2]), which are Roughness (L) lower-speed, lower- no remaining life then immediately rolled to volume roads Bleeding (L) Can accelerate the imbed chips (50 to 70 percent). because of the Moisture infiltration development of Application rates depend upon propensity for loose stripping in susceptible aggregate gradation and chips to crack Structural HMA pavements maximum size. Treatment windshields. Adds almost no structural capacity. seals pavement surface and However, effective at sealing fatigue improves friction. cracks (M) in comparison with other treatments. Site Restrictions High-speed, high-volume roadways are often avoided, although a number of approaches are being used to extend the applicability of these treatments. Construction Considerations Surface must be clean. Treatment should be placed during warm weather with chip spreader immediately behind asphalt distributor and rollers close behind the spreader. Approximately 2 hours required before roadway may be re-opened to normal speed traffic. Brushing is usually required to remove loose chips. Expected Life 4 to 7 years when placed in a preventive maintenance mode. 2 2 2 Typical Costs $0.90 to $1.08 per m ($0.75 to $0.90 per yd ) for a single application and $1.32 to $1.49 per m ($1.10 to $1.25 2 per yd ) for a double application. Additional Information A second chip seal may be placed to achieve improve performance. Total thickness may approach 25 mm (1 in.). Note: L, M, and H define level of distress (L for low, M for medium, and H for high). TABLE 9 Characteristics of thin hot-mix asphalt overlays THIN HOT-MIX EVALUATION FACTORS ASPHALT OVERLAYS Climate Traffic Conditions Addressed Contraindications Description: Plant-mixed Treatment performs Performance should not Functional/Other Structural failure (i.e., combinations of asphalt well in all climatic be affected by different Longitudinal and transverse fatigue cracking) cement and aggregate conditions. Actual ADT or percent trucks. cracking (L) Extensive pavement applied to the pavement in performance will vary Raveling/weathering (loose deterioration, little thicknesses between about according to factors Thin HMA overlays are surface material must be remaining life 19 and 38 mm (0.75 and that affect weathering not structural layers and removed) Thermal cracking (H) 1.50 in.). Dense-graded, and raveling of as such should not be Friction loss open-graded, and stone bituminous surfaces. subjected to strain from matrix mixes are used. Roughness loadings. Such layers Bleeding (L) may be subject to top- down cracking under Block cracking (L; may certain combinations of perform better with loadings, environmental additional milling) conditions, and pavement structures. Structural Rutting (assumes rutting has stopped; requires use of separate rut-fill application) Site Restrictions Edge-shoulder drop-off should be considered. Surface should be uniform to ensure uniform compaction. Construction Surface must be clean. A tack coat prior to overlay placement will help improve the bond to the existing surface. Considerations Thin HMA overlays dissipate heat rapidly and, therefore, depend upon minimum specified mix placement temperatures and timely compaction. Expected Life 7 to 10 years when placed in a preventive maintenance mode. 2 2 2 Typical Costs $2.09 to $2.39 per m ($1.75 to $2.00 per yd ) for dense-graded mixes; $1.50 to $1.70 per m ($1.25 to $1.42 per 2 yd ) for open-graded mixes. Additional Information While thin HMA overlays are considered a functional treatment, repetitive applications will impart some structural benefit to the pavement in the form of additional load-carrying capability. Note: L, M, and N define level of distress (L for low, M for medium, and H for high).

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14 TABLE 10 Characteristics of ultrathin friction courses ULTRATHIN FRICTION EVALUATION FACTORS COURSES Climate Traffic Conditions Addressed Contraindications Description: Relatively new Treatment should Capable of withstanding Functional/Other Structural failure (i.e., treatment in the U.S. Consists perform well in all high ADT volumes and Longitudinal, transverse and significant fatigue of a gap-graded, polymer- climatic conditions. truck traffic better than block cracking (L). Higher cracking and/or deep modified 10 to 20 mm (0.4 to other thin treatments. severities can be addressed rutting) 0.8 in.) HMA layer placed on with cold milling. Extensive pavement a tack coat formed by the Raveling/weathering (loose deterioration, little application of a heavy, surface material must be remaining life polymer-modified asphalt removed) Thermal cracking (H) emulsion. Treatment Friction loss (H) effectively addresses minor surface distresses and Roughness (L) increases surface friction. Bleeding (L) Structural Provides some increased capacity and retards fatigue cracking. Not suited for rutted pavements. Site Restrictions Ultrathin overlays should only be placed on structurally sound pavements. Localized structural problems should be repaired prior to overlay application. Construction Requires special paving equipment to place the mix and a license to apply it. Considerations Expected Life 7 to 10 years when placed in a preventive maintenance mode. 2 2 Typical Costs $3.00 to $3.59 per m ($2.50 to $3.00 per yd ), or about 50 percent more than thin, dense-graded HMA overlay. Additional Information A proprietary treatment is known in the U.S. as "Novachip." Note: L, M, and H define level of distress (L for low, M for medium, and H for high). TABLE 11 Characteristics of joint resealing and crack sealing JOINT RESEALING EVALUATION FACTORS AND CRACK SEALING Climate Traffic Conditions Addressed Contraindications Description: Resealing of Sealing of PCC Performance is not Functional/Other Different materials can be transverse joints and pavement joints and affected by Longitudinal and transverse expected to perform for sealing of cracks in PCC cracks performs well in different ADT or cracking (L) different durations. pavements is intended to all climatic conditions. percent trucks. Unsealed or partially sealed Material selection should minimize the infiltration of Sealant performance is Silicone sealants joints. be based on the expected surface water into the affected by that are not time until next treatment. underlying pavement environmental properly recessed structure and to prevent the conditions and the Structural are more likely to intrusion of performance of sealed fail in the No direct structural benefit, but incompressibles into the and unsealed pavement wheelpath. may reduce rate of structural joint. A range of materials structures probably deterioration. Sealing may also be including bituminous, varies within beneficial on a structurally failing silicone, and neoprene are environmental regions. pavement to prolong the time until used in designed rehabilitation. Crack sealing is not configurations. an effective method of repairing cracked slabs, but may be useful in preventing further deterioration. Site Restrictions Sealant reservoir should be clean and dry. Variable width reservoirs may cause a problem where backer rods are specified. Construction Sealant performance is dependent on many construction factors, including material type and placement geometry, Considerations and application in a clean and dry environment. Expected Life 7 to 8 years. Typical Costs $2.50 to $4.00 per linear m ($0.75 to $1.25 per linear ft) for hot-pour rubberized materials and from about $3.25 to $6.50 per linear m ($1.00 to $2.00 per linear ft) for silicone materials. Additional Information While the merits of joint sealing in new construction is currently being questioned, this debate has not extended to the merits of keeping existing pavements sealed. Note: L, M, and H define level of distress (L for low, M for medium, and H for high).

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15 TABLE 12 Characteristics of diamond grinding EVALUATION FACTORS DIAMOND GRINDING Climate Traffic Conditions Addressed Contraindications Description: Diamond Diamond grinding Diamond grinding Functional/Other Diamond grinding is not grinding is the removal of a performance is not performance may be Roughness appropriate if significant thin layer of concrete affected by climate. affected by traffic. Loss of skid faulting or other signs of (generally about 6.4 mm [0.25 However, if studded Grinding may be used to structural failure (such as in.]) from the surface of the snow tires or chains are remove faulting, which can pumping or corner breaks) pavement, using special used, surface wear may reoccur due to the Structural are present. equipment outfitted with a require more frequent continued application of Faulting series of closely spaced grinding to restore truck traffic. If grinding is Diamond grinding may not diamond saw blades. The friction. used to restore friction loss be appropriate if materials- major applications for caused by polishing of the related distresses are diamond grinding are to pavement surface due to present. remove surface irregularities vehicle traffic, heavy (most commonly joint volumes of traffic may faulting), to restore a smooth- Soft aggregate will wear cause the problem to much quicker and require riding surface, and to increase reoccur. pavement surface friction more frequent grinding. (14). Site Restrictions Disposal of the ground slurry should be addressed during project development. Construction Typically constructed with a moving lane closure with traffic operating in the adjacent lanes. Often used in Considerations conjunction with other restoration techniques such as after the completion of load-transfer restoration. Expected Life May reduce faulting for 8 to 10 years and roughness for at least 5 years. 2 2 Typical Costs Cost ranges from $1.50 to $6.50 per m ($1.25 to more than $7.00 per yd ) depending on the hardness of the aggregate. TABLE 13 Characteristics of undersealing EVALUATION FACTORS UNDERSEALING Climate Traffic Conditions Addressed Contraindications Description: Undersealing No studies are known to Performance is not known Functional/Other Significant faulting, or is the pressure insertion of a differentiate between the to be affected by different Anticipates the other signs of structural flowable material beneath a performance of levels of ADT or percent development of roughness failure (such as pumping, PCC slab to fill voids undersealing in different trucks. from faulting. mid-panel cracking, or between the slab and base, environmental corner breaks), suggest thereby reducing deflections conditions. structural failure requiring Structural and, consequently, more extensive deflection-related distresses Fills voids that, if left rehabilitation. such as pumping or faulting. unfilled, will lead to It is most often performed at faulting and other structural deterioration. Additional strategies, such areas where pumping and as dowel retrofitting, may loss of support occur, such as Performs best before faulting starts to develop. be required for pavements beneath transverse joints and without load transfer. deteriorated cracks. The voids being filled by this technique are generally less than 3 mm (0.12 in.) thick. Site Restrictions Voids must be identifiable and contained for undersealing to work. Construction Cement-fly ash grout is the most commonly used material, although asphalt has been used. Considerations Overfilling voids can contribute to worse problems than leaving them unfilled. Expected Life Performance has been extremely variable. Typical Costs Cost depends on the material used, the extent and size of the voids, and the size of the project. Cement-fly ash 2 2 grout undersealing ranges from about $1.08 to $1.20 per m ($0.90 to $1.00 per yd ), while asphalt undersealing 2 2 ranges from about $0.54 to $0.60 per m ($0.45 to $0.50 per yd ). Overview of Treatments used to anticipate and mitigate more serious deterioration. Ben- for Concrete-Surfaced Pavements efits of these treatments include reduced roughness, improved skid resistance, and protection against distresses accelerated by The preventive maintenance treatments for concrete-surfaced the presence of subsurface moisture (such as pumping, fault- pavements function in a different manner than those for bitu- ing, and corner breaks). Key characteristics of the concrete minous-surfaced pavements. The identified treatments can be pavement treatments are summarized in Tables 11 through 14.

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16 TABLE 14 Characteristics of load transfer restoration LOAD TRANSFER EVALUATION FACTORS RESTORATION Climate Traffic Conditions Addressed Contraindications Description: Load LTR has been used in The need for LTR Functional/Other Significant faulting, or transfer restoration (LTR) all climatic regions. increases with an Can prevent the development of a other signs of structural is the placement of load increased ADT and rough ride caused by faulting. failure (such as transfer devices across percent trucks. Low- pumping, mid-panel joints or cracks in an volume jointed cracking, or corner Structural existing jointed PCC concrete pavements that breaks). pavement to restore load are not doweled may Most effective on jointed concrete transfer at these locations. not need LTR. pavements that have poor load transfer at joints and/or transverse Pavements with little Poor load transfer can lead remaining life or to pumping, joint faulting, cracks but also have significant remaining structural life. The materials-related and corner breaks. distresses. optimum time to apply this technique is when the pavement is just beginning to show signs of structural distress, such as pumping and the onset of faulting. Site Restrictions Can be performed with a single lane closure. Construction Agencies have experimented with different retrofit patterns. Two to four bars per wheelpath is typical. Care must Considerations be given to the selection of the patch material and isolation of the joint. Often performed in conjunction with diamond grinding. Expected Life A minimum expected life is 9 to 10 years (15). However, many load-transfer restoration projects have been in place around 20 years with little or no distress present (Puerto Rico) (16). Typical Costs For production jobs, the typical costs are $25 to $35 per dowel. Additional Information Repetitive applications will impart some structural benefit to the pavement in the form of additional load-carrying capability. TABLE 15 Maintenance of drainage features MAINTENANCE OF EVALUATION FACTORS DRAINAGE FEATURES Climate Traffic Conditions Addressed Contraindications Description Maintenance of drainage features Drainage maintenance There are no The following activities are used as needed to is not limited by climate or traffic does not address specific contraindications for the improve or enhance the drainage capabilities of conditions. pavement condition. maintenance of drainage the existing pavement: However, timely features. Install/maintain reference markers at outlet maintenance of drainage locations. features helps to prevent the development of more Clear debris and vegetation at outlets and at serious deterioration. culverts. Inspect edge drain pipe using video equipment. Flush/rod edge drain system with high pressure equipment. Clean ditches and re-establish depths and grades. Restore cross slopes through milling or surface leveling (HMA pavements only). Regrade the shoulder to remove any buildup of dirt and debris. Clean closed drainage systems, including drainage inlets, catch basins, and manholes. Site Restrictions There are no site restrictions; this activity is performed entirely off the main roadway. Construction Considerations Drainage maintenance should be performed on a regular basis or whenever conditions warrant. Typical Costs Costs depend on activity and frequency. Additional Information The manner in which this activity is carried out varies widely among highway agencies. However, there is a far greater chance that the work will be completed if it is a programmed activity rather than one left for maintenance forces to do if all other activities have been completed.