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Surface Treatment

The Department of Public Works & Transportation began using surface treatment to improve deteriorated roadway surfaces which have resulted in lower maintenance costs. The treatment is flexible, has waterproofing qualities and adds about three (3) to five (5) years to the pavement life, depending on the volume of traffic. In addition, this treatment corrects surface raveling and oxidation of old pavements. Surface treatment is typically used to seal small cracks, improve skid resistance and to provide a new "wearing" surface on our non-arterial streets. A double surface treatment may also be used to convert a gravel road to a paved road which helps reduce maintenance costs on roads where traffic volumes quickly cause the gravel to "washboard" and pothole as well as providing a nearly dust-free driving surface. The Department of Public Works & Transportation was using the surface treatment process since 1985 and discontinued it for a Modified Surface Treatment in 2003, due to the amount of residential complaints received.

Pavement Preparation

It is the contractor's responsibility to sweep and remove any soil, sod or debris from the area of the roadway surface to be treated. Areas that are large enough may be patched using a spreader box. Any roadway in St. Mary's County in need of maintenance patching may be identified by the Inspector and performed under this contract. The calendar 2001 unit price for machine patching (using No. 7 or 8 crushed stone aggregate and CRS-2 bitumen) is $.60 per square yard.


Typically, the work should be performed between May 1 and June 30, but may be extended due to weather conditions. Construction shall not be started during rain, the threat of rain, fog or if the surface to be treated is wet. The completion of berm removal and pavement patching and prep work operations ($20-$50,000) are also funded under this program and completed in the Spring. Current unit pricing for the bid for single surface treatment is $1.85 per square yard. This program typically applies #7 (larger diameter) stone on lower volume previously surface treated roadways and #8 (smaller diameter) stone on higher volume and/or previously asphalt overlaid roadways. This particular maintenance effort will cover an average of three (3) to four (4) miles of roadways per day. The most common complaint from residents is the "loose" stone experienced after the overlay operations have been completed.

Control of "Loose" Stones

It is the contractor's responsibility to sweep and remove any soil, sod or debris from the area of the roadway surface to be treated. After a road has been surface treated, the contractor may be directed by the County inspectors to clean, sweep and remove loose stone along the treated roadways and at intersections with-in seventy-two (72) hours after placement via the use of broom truck(s). The Department has modified its bid documents to require the contractor to remove loose stones for a period of up to two (2) weeks to reduce the number of residential complaints. The work must be completed to the satisfaction of the Inspector. Both of these items are considered incidental to the contract and are not additional pay items. In order to address the raveling of stones throughout the subsequent weeks and remainder of the year, the County Highways vacuum truck is also utilized. Overlay may not begin if the temperature is below 60 degrees Fahrenheit, if there is a threat of rain or if the surface to be treated is wet.

Cape Seal

It is often that a surface treatment is subsequently slurried (cape sealed) or overlaid with asphalt the following year(s). Cape Seals are used where a chip seal is too rough and requires a smooth finish, for example in residential streets. In instances where cracking is a problem a chip seal can alleviate cracking and the slurry can provide the smooth and hard wearing surface. The addition of a slurry capping not only makes the surface smooth but locks the aggregate of the chip seal in place eliminating stone loss. A cape seal can last longer, can treat cracks, is smoother than a chip seal, more durable than a slurry and could last as long as ten (10) years depending on traffic volumes.