|Roadway preparation is the systematic excavation of roadway areas that have failed which are planned to be eventually replaced by a reconstructed roadway section in preparation of either an asphalt overlay or a slurry resurfacing project. Affected areas are usually identified, marked in the field by inspectors and may be surface treated or patched with a modified seal between March 1st and July 1st each year. These areas vary in size from a 4’ by 4’ section up to a full street width.
Each year, since 1998, prior to the onset of the paving season the Department forwarded the listing of planned overlay improvements and the preliminary scheduling for distribution to the Commissioners of St. Mary's County and for release to the press. For planned Asphalt overlay projects, individual notices are posted by the contractor, at each residence and prior to mobilization, advising them of the program process and timing. In addition, the utility companies are also made aware of the roads that will be affected (ie. METCOM water valves and sanitary manhole tops need to be adjusted both during and following the application of certain overlay treatments). For County construction projects, please view our Asphalt Overlay Program Listing.
Sealing of large cracks in asphalt pavement, and “tying together” pavement sections containing alligator cracking with rubberized asphalt. The purpose of this activity is to prevent moisture damage to the sub-grade. This activity may also be scheduled in preparation for surface treatment and asphalt overlay.
Worn, deteriorated roads with potholes, severe cracking, heavy rutting that traps water and causes hydroplaning and slick surfaces (polished aggregate) with reduced skid resistance often require immediate attention. Milling offers an Pavement Milling economical tool for removing failed pavement so new overlays will last longer, ride smoother and perform better. Existing surface mix buildup is mechanically removed which minimizes the possibility of rutting and provides a better bonding surface for new paving material, thus extending the life of the surface. By removing old layers of pavement to a desired depth using specialized equipment, the surface is restored free of bumps, ruts, wash-boarding and other cross-sectional imperfections. The finished texture surface will immediately support traffic while awaiting the final overlay. Milling also saves on the need to adjust inlet grates and replace curb and gutter. By keeping the full height of the original curbing the drainage capacity in the gutter pan is maintained which precludes the potential spread of storm-water runoff into the travel-way.
Installing a tack coat and an asphalt overlay fabric (to old pavements) before re-paving can add years to roadways, parking lots and airport runways. This measure has proven to be a cost effective method of retarding reflective cracking by providing a barrier to reduce moisture penetration to the sub-grade, and at the same time reducing the fatigue life of the pavement structure. These fabrics are durable, flexible, easy to handle and install, have excellent resistance to de-lamination, absorb / dissipate stresses in the pavement, reduce water infiltration, reflective and fatigue cracking.
Full-Depth Asphalt Patching
It is used to repair all types of localized pavement distress that extends below the roadway surface. Examples include potholes, alligator cracking, upheaval, and shoving. Patches can be a temporary repair or a more permanent integral part of the pavement system. Cold mix is exclusively used for temporary and emergency patching at a current cost of $80 to $90 per ton. Hot mix asphalt plant mixes with asphalt cement and graded aggregates may be obtained from vendors at a cost of between $26 and $29 per ton. The materials may be delivered to the job site or directly to the Department.
Each lift of the patch must be compacted thoroughly. Excluding major pavement failure, typically a depth of three (3) inches is considered sufficient for a full depth patch. Approximately $300,000 in pothole /pavement patching is performed on an annual basis. Machine patching unit prices are currently estimated at between $1.67 and $1.85 per square yard for surface treated and modified seal roads and full depth asphalt patching at $78 per ton ($17.33 per square yard).
An annual problem on shoulders is that of build-up of material along the edge of the paving. This can occur from not cleaning the shoulders after winter operations. Anti-skid material gets shoved to the side of the road by traffic action and catches dust and dirt. Vegetation then grows in this excess material, further slowing the flow of water off the pavement edge and holding back more sediment. The water flowing along the edge of the pavement seeps into the base, which can result in the loss of pavement strength and eventual break up of the surface as vehicles travel near the edge. Therefore, in preparation of surface treatment / asphalt overlay operations and shoulder widening / adjusting projects, between 50-70 miles of roadways have the shoulder areas, immediately adjacent to the travel-way, mechanically cut back using the loader and removed to improve surface drainage. This operation must be performed in the spring, usually between March 1st and May 1st , and prior to the commencement of the overlay contracts to avoid delay in the contracts. In addition, the ground is soft and damp which assists with dust control and minimization of residential complaints.
Wedge and Level (¼ Crown Removal)
Pavement irregularities, unequal settlement and surface defects can be corrected through “leveling” operations, which can return the roadways to a safer and more acceptable section. The process provides surface consistency, improves ride ability, safety and surface drainage of the wearing surface. The correction of pavement sections is also important to the success of snow removal and ice control operations. Steep cross slopes are undesirable because of the tendency of vehicles to drift and skid laterally toward the low edge of pavement which becomes a major safety concern for drivers during inclement weather conditions. Many existing older roadways have a parabolic shaped cross-section, an atypical/steep cross slope or may require super-elevation adjustments. Super-elevated roadway sections are routinely checked for adequacy by the Department using a ball bank indicator to ensure the correct rate and/or posted speed is in place.
The “wedge”-shaped piece needed to create the proper cross-section can be accomplished through the addition of pavement or the use of shoulder machine(s), depending on the severity of the area being adjusted. Older surface treated roads typically require the addition of base asphalt to perform the necessary “wedging” while the asphalt roadways rely on applications of surface (SN) asphalt to achieve the proper grade. The “wedging” operations result in the removal of the unsatisfactory section (¼ crown removal) and may be performed in conjunction with minor widening projects and prior to scheduled pavement overlays to prevent raveling. Although some overlap of pavement is required beyond the repaired section, ¼ crown removal does not always involve the addition of pavement to the centerline but does often require shoulder and ditch adjustments along the affected portions of roadway. Adequate cross slopes also offset problems associated with rutting. Approximately three (3) miles of ¼ crown removal is performed annually to improve the typical sections of existing County-maintained roadways which ultimately helps reduce the overall costs of maintenance. The resulting improved cross-section should provide a smooth straight-edged appearance.