In February 2007 the City of Durham contracted MACTEC Engineering and Consulting, Inc of Beltsville, Maryland to conduct a pavement condition survey for streets maintained by the City of Durham. Download the PDF file with the results of that survey including the recommended method of repair.
This report presents the Pavement Condition Survey results and analyzes the maintenance needs for the City of Durham’s (City) street system. MACTEC Engineering and Consulting, Inc. (MACTEC) conducted the visual survey of the streets maintained by the City following the approach developed by the Institute for Transportation Research and Education (ITRE). Pavement condition surveys were performed by MACTEC survey crews between February 26 and April 13, 2007. The results from this survey were used to determine maintenance needs and estimate their costs.
A total of approximately 651.74 centerline miles (6,913 pavement sections) of asphalt surfaced pavements were included in our survey. This corresponds to an increase of 24.6 centerline miles, from 627.14 miles, since the last survey in 2004. The City’s street system is predominantly defined as Class A (low volume) roads which accounts for 88.7 percent of the system roads. The remaining 11.3 percent of the system is defined as Class B (high volume) roads. Curb and gutter has been constructed on most of the streets in the City. Approximately 19.8 percent of the system has no curb and gutter, 79.2 percent has curb and gutter on both sides of the street and 1.0 percent has it on one side only.
Pavement condition survey results are the basis for developing maintenance needs. The condition survey methods developed by ITRE are used to visually collect pavement distress data which are further used to compute the Pavement Condition Rating (PCR) value for each section. The predominant distress types collected are alligator cracking (the most critical pavement distress), raveling, patching and block/transverse cracking.
Approximately 34 percent of the street system was noted as having some level of alligator cracking, 49 percent of the street system was found to be raveled, 38 percent of the street system has patching, and 34 percent of the street system has block/transverse cracking. Occurrences of reflective cracking, rutting, bleeding, and ride quality were also noted. The weighted average PCR value of the City’s street system in 2007 is 71, representing a "Fair" overall condition. In comparison, the 2004 survey had a weighted average PCR value of 79, also representing a "Fair" overall condition.
The analysis indicates 60.2 percent (392.48 miles) of the streets in the City need some level of maintenance with a total repair cost of approximately $22.5 million for routine maintenance and plant mix resurfacing. This represents an average of $34,483 per mile for the entire street system. This figure has drastically increased since the last survey in 2004 when the average cost per mile was $16,455. Pavement condition deterioration (average PCR decrease from 79 in 2004 to 71 in 2007) and material unit cost hike (asphalt tonnage increase from $36 in 2004 to $61 in 2007) are the major contributing factors to the cost per mile increase. It should be noted that this cost estimate is for pavement repair only. Additional costs can be incurred for drainage improvements, administration, utility adjustments, milling, work zone traffic control, and other items. Please note that these costs are variable and can increase the total project cost significantly.
Skin patching is used to fill depressions, in which case the patch could be as thick as three to four inches. A skin patch differs from removal and replacement because existing asphalt is not removed during skin patching. This type of repair should only be used when there is no base failure, to correct drainage. Skin patch is also used to isolate asphalt that is Spaulding (loose and rough) usually to extend the life of the asphalt (3-10 years), improve appearance or stop water penetration.
Resurface (also known as overlay, retop, or recap) is to apply a new layer of asphalt (usually 1.5 inches to 2 inches) over existing pavement.
Full Depth Patch is basically a pothole that needs its sub base repaired.
Short Overlay is a thin layer of asphalt similar to resurfacing but for a small area.
Crack Pouring is simply filling in the cracks.