AGENDA #5c

 

MEMORANDUM

 

TO:                  Mayor and Town Council

 

FROM:            W. Calvin Horton, Town Manager

 

SUBJECT:       Response to Council Petition Explaining Differences between Repaving and Milling of Roads

 

DATE:             October 27, 2003

 

 

            At the meeting on September 22, 2003, a Council member asked that the Manager prepare a report distinguishing between street resurfacing and milling.

 

         BACKGROUND AND DISCUSSION

 

For purposes of this memorandum, the following definitions will apply:

 

• Resurfacing is the application of one to two inches of asphalt to streets to serve as the riding surface.

 

• Slurry seal involves the use of a combination of an emulsified asphalt and fine aggregate mixture to serve as a riding surface, and is a less costly option than resurfacing.

 

• Milling is a process in which pavement surfaces are machine ground after there have been several street overlays. This process assists in retention of gutters, thus assuring proper handling of stormwater.

 

The Town routinely has a street survey completed by the Institute for Transportation Research and Education (ITRE) to determine the priority of streets for various types of paving treatment.  We base the actual annual work program on such prioritized analysis of streets and the budget appropriation included in the annual adopted budget.

 

We have determined over the past several years that it is possible to obtain greater street maintenance efficiency through use of a combination of contract resurfacing and slurry seal.  For example, during the current fiscal year, we resurfaced 5.5 miles of streets and used slurry seal on an additional 2.5 mile of streets.

 

Resurfacing and application of slurry seal are alternative pavement treatment options. A traditional resurfacing treatment includes use of one to two inches of an asphalt riding surface.  Slurry seal is a less costly treatment that uses an emulsified asphalt and fine aggregate mixture applied to the riding surface of those streets whose riding surface is sound, but which are vulnerable to traffic and weather conditions.

 

The use of this less costly option is appropriate for those streets which are not structurally deteriorating and whose riding surfaces basically are sound.  Slurry seal extends the life of such streets and provides more efficient use of street maintenance funds.  In addition, it has the relative advantage of deferring the need for future milling caused by successive asphalt overlays.

 

We also use a process called “milling”, primarily in those instances in which the scheduled overlay would result in an insufficient gutter to properly handle the stormwater.  Milling is a process typically used to retain the gutter to insure proper drainage and consists of machine grinding of pavement surfaces after several street overlays.  On high volume streets, milling also improves adhesion of new surfaces on older surfaces, reducing slippage of asphalt and premature pavement failure.  In addition, it may be the most prudent option to remove the existing asphalt and sub-surface materials on those streets which need to be reconstructed in order to eliminate base problems and/or handle current traffic loading. The by-products from milling are used as base materials for street reconstruction; for conversion of dirt streets to paved ones; and for recycled pavement mixes.