Agenda #7d | Street Maintenance Services

AGENDA #7d

BUDGET WORKING PAPER

TO: W. Calvin Horton, Town Manager

FROM: Bill Letteri, Public Works Director

SUBJECT: Street Maintenance Services

DATE: March 8, 2006

PURPOSE

This paper defines our funding request for pavement preservation activities performed by contract and provides a brief description of each technique.

BACKGROUND AND DISCUSSION

Each year we use a mix of alternative methods for street maintenance. The following discussion presents definitions of various methods for street maintenance.

The information provided presents summaries relative to the streets tentatively scheduled for maintenance and the type of maintenance proposed. The recommendations are based on a bi-annual street survey by an engineering firm in conjunction with the Institute for Transportation Research and Education (ITRE) and by an annual follow-up staff analysis of all streets within the Town.

The Institute for Traffic Research and Education survey reflects comparative pavement conditions among localities state wide. The “Similar Size Municipalities” ratings represent the weighted average ratings of two municipalities similar in size to the Town of Chapel Hill in the number of miles of pavement. The “Overall Average” is a weighted average of all 14 municipalities, excluding the Town of Chapel Hill. The most recent data for this study is FY 2004-05.

As can be seen from the following table, the Town of Chapel Hill compares favorably to other municipalities throughout the state in terms of overall condition of streets.

Condition	Two Town of Chapel Rating	Fourteen Similar Size (miles) Hill*	Cities Overall Municipalities**	Average***




Very Good	91-100	74.7%	70.5%	56.8%

Good	81-90	17.4%	10.3%	13.7%

Fair	66-80	6.2%	10.7%	14.0%

Poor	51-65	1.2%	4.5%	7.7%

Very Poor	0-50	0.5%	3.9%	7.7%

* Fiscal Year 2004-05 is most recent (data received 01/2005); next scheduled survey is in fiscal year 2006-07.

** Represents weighted average ratings of two other similar size municipalities surveyed over the past two years in terms of miles of streets maintained.

*** Represents weighted average ratings of all (excluding TCH) 14 municipalities surveyed since March 2003.

The base budget request for street maintenance work next year includes the following amounts shown by category of work. We believe the requested budget would basically maintain our overall favorable ITRE ratings and meet our current basic needs.

M and R Streets

Street Resurfacing	$378,000

Milling	$ 60,000

Slurry Seal	$ 40,000

Fog Seal	$ 20,000

Total	$498,000

Resurfacing

Our tentative list is for resurfacing about six miles of streets with an average pavement age of 17.5 years since the last traditional overlay. We have provided the list of streets under consideration for a traditional overlay and slurry seal to the Planning Department for review with the Transportation Board and the Bicycle and Pedestrian Advisory Board.

A traditional overlay is one of several preventive maintenance activities to keep pavement, under normal conditions of traffic and normal forces of nature, as nearly as possible in its original constructed condition. Such maintenance is necessary because all pavements eventually will weaken due to stress.

Resurfacing treatments vary in terms of overlays used. Surface deficiencies can benefit from relatively thin resurfacing, while structural problems may require thicker overlays based on pavement properties and traffic loadings. Overlays should be used on stable pavements with a sound base, but have a surface which exhibits minor surface distress such as cracking, rutting, raveling and roughness. An overlay will add structural support to the riding surface, but should not be used on pavements showing structural distress. The service life for an overlay is typically 8 to 14 years.

Milling

Milling is a process used to retain the gutter to insure proper drainage and consists of machine grinding of pavement surfaces near gutters after several street overlays. Milling also improves adhesion of new surfaces on older surfaces, reducing slippage of asphalt and premature pavement failure. We started using some of our annual street maintenance budget for milling in 1998. Since that time, we have been able to constantly re-establish flow capacity through our gutters.

Slurry Seal

While use of asphalt overlays has been our traditional approach to restore deteriorating street pavements, it is cost effective for some streets to use an alternative known as slurry seal. This option consists of use of an emulsified asphalt and fine aggregate mixture applied to the riding surface of those streets having a sound riding surface, but are vulnerable to traffic and weather conditions. Such treatment seals and fills cracks in street surfaces and corrects crumbling and oxidizing pavement.

The use of this less costly option is appropriate for those streets which are not structurally deteriorating and which have riding surfaces that are basically sound. Slurry seal extends the life of such streets and provides a 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. The service life for a slurry seal is typically 4 to 7 years. The funding level requested for fiscal year 2006-07 will permit slurry seal on an estimated 1.5 miles of streets.

Fog Seal

Fog seal is an application of a liquid agent that contains the same petroleum oils present in a pavement's asphalt cement used to "glue" and hold together the various sized aggregates present in the pavement. These oils are baked out of the asphalt pavement through the pavement's constant exposure to the sun's UV rays and heat.

This type of seal should be applied on nearly new pavements (no more than five years old) that are structurally sound and in good to excellent condition. Properly applied on a regular basis (approximately every three to five years), this application should aid in keeping the pavement surface sealed and in good condition, helping to avoid more costly repairs and/or overlays. This type of seal is most commonly used on lower speed streets, such as residential streets and minor arterial. The funding level requested for fiscal year 2006-07 will permit the application of a fog seal on an estimated two miles of streets.

Crack Pouring

This process involves cleaning and sealing existing cracks in the pavement resulting from pavement shrinkage. This will stop water from penetrating into the sub-base, creating more expensive pavement failures. Crack pouring is widely recognized as a very cost-effective expenditure of funds. The service life for crack pouring is typically 3 to 5 years. Given the relatively small need at this time no funding is requested in fiscal year 2006-07.

Reconstruction

This relatively costly process involves replacement of sub-grade and/or base materials prior to installation of any new riding surface. A separate budget working paper discusses this alternative and the budget request.

Patching

Skin patching consists of application of tack coat adhesive on a pavement surface, followed by a thin layer of hot asphalt. Full depth patching consists of repair of a localized base or sub-grade failure under bituminous surfaces by excavation and replacement of unsatisfactory material and wearing surface.

SUMMARY

The above discussion presents the various methods we use each year to maintain and preserve a sound local street system. One of the benefits of such a mix is an increase in the overall useful life of many streets prior to use of more expensive options such as resurfacing or reconstruction. We note that our practices have been favorably reviewed by MAXIMUS. Also, ITRE has found repeatedly that the Town’s streets compare highly favorably throughout the state. In their level of service study dated January 2002, they noted that the Town of Chapel Hill has been “very aggressive in its use of the ITRE-pavement management system method as a means of managing its pavements.”