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Hot mix asphalt (HMA) patching is the technique used to repair tar and chip roadways. In previous years, the patching on these roadways was performed by in-house Highway Operations staff. This patching is now performed by PMP contractors. A HMA patch is utilized to repair the damaged roadway area which tar and chip resurfacing cannot effectively repair, increase the pavement section thickness to provide additional structure and can be slightly sloped to ensure proper drainage.
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The PMP’s practice for notification includes notices, in the form of a door hanger, that are placed on each property that abuts the scheduled work. All residential properties that abut the road segments receive notices 2 days in advance of the planned work. This notice is sent for the purpose of informing the adjoining residents of the upcoming work so they understand how their property may be impacted or what kinds of travel delays may result. This notice also provides a point of contact should they have any questions or experience any issues. The segments that have no scheduled repairs do not receive notifications. On the day of construction, PMP uses temporary traffic control devices for a one lane road closure to warn residents and non-residents and the traveling public of construction activities per the Maryland Manual on Uniform Traffic Control Devices (MdMUTCD) standards.
The current procedure for driveway tie-ins depends on the material used to build the driveway apron. Asphalt driveways are milled or sawcut at a location to provide smooth transition when entering or exiting. The milled or sawcut tie-in provides a straight edge for the asphalt to prevent future peeling or cracking. Concrete driveways are more challenging. The current process uses a tack coat on the concrete and the asphalt is feathered in from the road edge to a location that allows smooth transition. Brick driveways are rare but are present in Frederick County. The tie-in for brick driveways involves milling the abutting asphalt edge and replacing during the overlay to match the existing brick elevation. A transition before and after the edge of the apron needs to also be milled. This tends to create a dip in the roadway and affects the finished ride quality of the new surface. PMP is currently exploring standard details to improve tie-ins to concrete and brick driveways.
Generally, roadways are not widened as part of a PMP contract. When the roadway is overlaid with 1-1/2” to 2” of HMA on top of the existing road, asphalt will roll off the edge giving the appearance that a thicker or wider section has been placed.
Shoulder drop-offs greater than 2” during patching or overlay of the roadway are DPW’s responsibility for shoulder back-up repair on all roadways, asphalt or tar and chip touched by the program. Roadways are backed-up in one of two ways. Lawn areas that are mowed by residents receive topsoil and turfgrass establishment. Non-lawn areas receive CR-6 stone or millings as shoulder back up repair.
Millings that are removed from the existing road during construction become the property of the contractor. DPW staff will direct any milling requests from a property owner to the attention of the contractor for possible coordination of obtaining millings.
There are three roadway surface types in Frederick County; HMA (hot mix asphalt), Tar and Chip and Gravel. There is a petition process in place to change a roadway in the Rural Roads Program from gravel to tar and chip. This process is currently in a moratorium until the new program is in place. There currently is not a process to change a roadway from tar and chip to asphalt. DPW will be working on a formal process (Standard Operating Procedure or SOP) to convert roadways to a new pavement type.
Hot mix asphalt (HMA) patching is a common technique used to repair tar and chip roadways when existing roadway conditions are in poor, fair, or satisfactory condition. When existing roadways are in poor condition, heavy patching using HMA and sometimes full reconstruction are needed. When a roadway is in fair or satisfactory condition, roadways are patched with HMA in areas experiencing distress. A tar and chip resurfacing is performed on roadways that are in good to excellent condition. Roadways are typically resurfaced on a 4-year to 7-year cycle based upon the roadway’s needs as described above. PMP evaluates tar and chip roadway conditions biennially. In previous years, the patching on these roadways was performed by in-house Highway Operations staff. Most all of this patching is now performed by PMP contractors. A HMA patch is utilized to repair the damaged roadway area which tar and chip resurfacing cannot effectively repair. HMA asphalt increases the pavement section and can be slightly sloped which provides additional support and proper drainage that prevents future cracking. A tar and chip wearing surface is applied at ¼” to 3/8” thickness uniformly over existing conditions and has very little structural value. A pavement section is a series of road construction layers with the goal of distributing vehicle loads over a larger area so that it will not exceed the bearing capacity of the subgrade. An asphalt pavement section consists of a soil subgrade, stone subbase, base asphalt and one to several layers of surface asphalt. The soil subgrade and stone subbase are susceptible to structural defects from water penetration. The layers of asphalt are used to provide the needed extra support and provide cross-sectional drainage. A tar and chip pavement section consists of a soil subgrade, stone subbase and layers of tar and chip. Once cracking distresses appear in the tar and chip layers, the support system is compromised and can quickly deteriorate. Patching with stone and tar and chip would provide a shorter lived repair that ultimately would worsen and settle between recommended treatments. Full reconstruction would then be required which is far more expensive than patching with HMA and applying the wearing course. This repair method is an industry standard practice for tar and chip roadways as a tar and chip wearing surface is then placed over the HMA patch.
PMP does not maintain gravel roadways. All concerns pertaining to gravel roadway maintenance can contact the Department of Highway Operations for resolution.
Per Resolution No. 02-23, The 2002 Rural Roads Program Resolution dated September 24, 2002, Exhibit A Item 4 Maintenance:
“A roadway designated as a rural road shall continue to be maintained by the County on a regular schedule, and in such a manner that safe public access continues to be afforded. These guidelines are intended only to pertain to the County-maintained rights of way, including, but not limited to, the travel way and any contiguous ditches. The County shall continue to maintain the road in a continuing, responsible, manner equal to the effort that existed at the time the road was adopted into the program.
Per the resolution, the roadways are being maintained on a regular schedule to afford safe public access within County-maintained rights of way equal to the effort that existed at the time the road was adopted. Maintenance improvements and reconstruction are permitted as necessary to retain the integrity of the roadway within normal bounds of regularly scheduled maintenance.