Spring is finally here! For many homeowners it’s time to gear up for those summer home maintenance projects. We’re all fully aware that moisture and sunlight combined with general wear and tear take a toll on the useful life of our homes. Maintenance such as roofing, painting, replacing a section of siding, or installing new rain gutters are tasks that we all dread, but we gladly do anyway because we know in the long run it’s cheaper to perform these activities on a regular basis than to ignore them and face costlier repairs later.

Coincidently, these very same elements that threaten our homes are also the leading causes for road surface failure. While we all dread the inconvenience of road closures and traffic delays caused by road maintenance activities, the reality is they are essential to maintaining the condition of our road system for the same financial reason as performing regular maintenance on our homes.

Throughout the spring and summer, the City of Lewiston, Public Works Department Street Maintenance Division will once again be working on several maintenance projects citywide as part of the Annual Street Preservation Project. Approximately 23 miles of Lewiston streets will receive chip seal or cold mix overlay applications. Many of these will also have some form of patching or crack seal work performed prior to seal coat or overlay.

Descriptions of various maintenance activities planned for 2008 have been included below. These descriptions are general in nature and solely intended to give the traveling public an idea of what to expect when they encounter each activity.

Quality Patching

More commonly known as full depth patching, this activity utilizes the method of removing and replacing areas of damaged or fatigued asphalt pavement where the majority of a particular road surface is in relatively good condition and only localized repairs are needed. Quality patching is considered a localized structural repair that can be done as a stand-alone repair or in conjunction with other maintenance activities such as chip sealing or road surface overlaying.

Damaged areas to be removed are cut out and squared with either a pavement saw or grinder. The old asphalt, and in some instances, road base material is removed with a skid steer loader or backhoe (dependent upon how much material is to be removed). If hot mix asphalt is to be used as the replacement material, a “tack coat” of liquid asphalt is sprayed onto the bottom and edges of the repair area to provide a watertight seal between the new patch and old road surface. New asphalt mix is placed into the repair area to a depth that can be compacted level with the surrounding road surface. The material is then raked and compacted using a plate compactor or steel drum roller.

Quality patching is performed by both the Street Maintenance Division and private contractors hired by the City of Lewiston. Operations conducted by the City are typically performed by a four-man crew, but can at times require more people dependent upon physical location, size of repair areas, and the amount of traffic control required for each project. Contractors determine crew sizes for patching operations performed by contract.

Traffic lane closures are almost always needed for quality patch activities. Traffic channelization, flaggers or a combination of both will be used to move traffic through the work zone. If several repairs are to be done at once, total road closure may be necessary. In these instances, detour routes will be used to guide traffic around the work zone.

Crack Sealing

This activity employs the use of hot rubberized asphalt to fill open cracks in asphalt pavement where the majority of a particular road surface is in relatively good condition and only transverse, longitudinal, or block cracking is present. Crack sealing can be done as a stand-alone repair or in conjunction with other maintenance activities such as quality patching or chip sealing.

The machine used to perform this activity is a trailer-mounted unit that carries a melting pot (used to heat and liquefy the fill material), pump and material applicator wand, and an air compressor. Typical operation consists of one man walking in front of the machine using compressed air to dislodge dirt and debris trapped inside cracks in preparation for filling. Two other crewmembers walk behind the machine injecting hot rubberized asphalt into prepared cracks and striking off any excess fill material level with the existing road surface. In some instances, a third person may be utilized at the rear of the machine to apply a detaching agent over the freshly filled cracks. This sometimes becomes necessary if the operation is moving faster than the rubberized material can cure.

Crack sealing is performed by Street Maintenance Division personnel using a minimum of six people, but can at times require more dependent upon how much cracking is present or how extensive of traffic control plan is required.

Traffic lane closures are almost always needed for crack sealing activities. Traffic channelization, flaggers or a combination of both will be used to move traffic through the work zone.

Chip Sealing

Chip sealing is a maintenance activity that utilizes a thin layer of liquid asphalt to seal the pavement surface followed by an application of aggregate cover coat material to provide a sturdy wear course too extend the life of the seal. Typically, the City of Lewiston maintains a seven-year sealing schedule for all asphalt pavements within the right-of-way. Application can be applied on pavements that exhibit no visible defects and have simply arrived at their position in the seven-year cycle or on pavements where the majority of a road surface is considered serviceable and only fine cracking or minor defects exist. Chip sealing can be performed as a stand-alone activity or in conjunction with other maintenance activities such as crack sealing, quality patching, or pavement grinding.

Prior to application of a chip seal, road surfaces must be cleaned to ensure a proper bond is established between the old road surface and new seal. Weeds growing through the asphalt surface are removed and street sweepers are utilized to pickup dirt and debris.

An asphalt distributor truck is used to apply a thin layer of hot liquid asphalt onto the old road surface followed by a chip spreader unit which applies a cover coat material of ⅜” to ½” aggregate. Rubber tired rollers bring up the rear of the operation pushing cover coat material down into the liquid asphalt layer so it can become embedded. The seal is left to cure for a minimum of forty-eight hours, after which excess aggregate is picked up with sweepers.

During the curing process chip seals remain tender. Cover coat material can easily be dislodged, or separated, from the asphalt layer by traffic traveling at high rates of speed, spinning tires, skidding at stops, or performing sharp turns. These sorts of traffic movements adversely affect the safety and performance of chip seals. Dislodged aggregate can be picked up by tires and flung at other motorists resulting in property damage. It can also reduce the amount of wear surface on the seal shortening its effective life. Motorists are asked to please use slower speeds and adhere to reduced posted speed limits when traveling on fresh chip seal projects.

All chip sealing and related traffic control operations are currently conducted by private contractors hired by the City of Lewiston. It is up to the contractor to determine crew size and the amount of equipment needed for this activity.

Traffic lane closures are always necessary for chip sealing activities. Traffic channelization, flaggers or a combination of both will be used to move traffic through the work zone. Dependent upon location and circumstances surrounding specific projects, total road closure may be necessary. In these instances detour routes will be used to guide traffic around the work zone.

Cold Mix Overlay

More commonly known as road mix overlay, this repair involves the application of a two to three-inch depth asphalt mix mat followed by a bituminous surface treatment (BST seal). This activity is chosen for asphalt pavements on low to moderate volume roads for surfaces that exhibit a high degree of pavement failure and are in need of structural improvement. Cold mix overlay can be performed as a stand-alone repair or in conjunction with other activities such as quality patching and pavement grinding.

Pavement surfaces require proper preparation before the new asphalt overlay can be applied. Surface areas where total base failure has occurred must be removed and replaced, weeds are sprayed in early spring, shoulders on surfaces that don’t have curbs are graded, humped and shoved areas of pavement are leveled by use of a pavement grinder, overhanging trees and shrubbery are cut back to allow room for paving equipment to operate, and the surface is cleaned with street sweepers.

Actual paving operations are performed in two courses, a thin ½” to ¾” pre-level course to fill irregularities in the old surface and the two to three-inch riding course. Application of both is basically the same. Dump trucks deliver asphalt mix paving material to the paver which in turn applies the material to a desired depth. Initial breakdown and compaction of the mix is accomplished by a steel drum roller. Two rubber tired rollers are utilized for final compaction efforts. Once the riding course has been compacted, the road is returned to traffic and allowed to cure for a period of time after which a BST seal is applied.

Cold mix asphalt material is a slow curing mix that can take between two to three weeks after application to setup (harden). During this period the cold mix material is very tender and can easily be displaced by aggressive traffic movements such as spinning tires, skidding at stops, or performing sharp turns. Movements such as these can adversely affect the ride and performance of cold mix overlays. Motorists are asked to avoid these types of movements when traveling on fresh overlays.

In late August, crews return to apply a BST seal over all surfaces that received cold mix overlay during June and July. Road surfaces are once again cleaned to ensure a proper bond is established between the overlay surface and the BST seal. An asphalt distributor truck is used to apply a thin layer of hot liquid asphalt on the new cold mix surface followed by a chip spreader unit which applies a cover coat material of ½” to ⅝” minus aggregate. Rubber tired rollers bring up the rear of the operation pushing cover coat material down into the liquid asphalt layer so it can become embedded. The cover coat material used contains manufactured fines that can create dust. Approximately twenty-four hours after application a diluted dust coat material is applied over travel lanes by distributor truck to reduce dust emissions from the seal. Sweeping of excess cover coat material begins directly after all roads have been sealed. Sweeping is performed in the same order as roads were sealed and can take between two to three weeks to complete.

All cold mix overlay, BST seal, and related traffic control operations are currently conducted by the Street Maintenance Division. Ten full-time and seven seasonal positions are utilized during these efforts.

Total road closure is a necessity. Residents living within the work zone are asked to park on adjoining streets while overlay work is in progress. This is a matter of safety for the traveling public and our crew. If you should find yourself blocked inside a work area, please ask one of the crewmembers for assistance. They can help you navigate safely out of the area.

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