Failure to maintain a pavement system on a routine basis can erode its lifecycle. Shopping center owners expect their parking lots to last a long time, but most also realize that they have a role in making that happen. The lifecycle of a parking lot generally ranges from 20 to 30 years, according to some experts, who add that within that time frame, there most likely will be at least one complete resurfacing or overlay.
"Proper maintenance and sequenced resurfacing can extend lot life beyond 20 years," says John Stuckey, vice president of property management for The Skinner & Broadbent Co., Indian-apolis.
Alan Curtis, president of CHEC Consultants Inc., a Redding, Calif.-based civil engineering company that specializes in pavements, estimates a lifecycle of 30 to 40 years, with a major rehabilitation of the lot at around 17 to 22 years. The key to a longer lifecycle, he says, is to have a well-built lot with a reasonably good design that is properly maintained through the years. Curtis works with such shopping center developers as San Diego-based TrizecHahn Centers, Chicago-based Urban Retail Properties Co. and Chattanooga, Tenn.-based CBL & Associates Properties Inc.
Stuckey also emphasizes the importance of the original construction of the lot. How well it is installed, along with the foundation and the specification of materials, play a major role in how long one will last, he says.
If there is a problem with the original construction or structure of the lot, it will generally show up in the first four to five years or even sooner, says Thomas R. Zimmer, principal of Zimmer Consultants Inc., an Oak Brook, Ill.-based civil engineering firm that specializes in pavement construction and management. His company works with such shopping center clients as Indianapolis-based Simon DeBartolo Group Inc., Chicago-based General Growth Properties Inc., Atlanta-based ERE Yarmouth and Newton, Mass.-based WellsPark Group.
Some of the signs of structural damage, Zimmer says, include depressions in the lot; rutting; and alligatoring, otherwise known as fatigue cracking. Traffic is the primary culprit in these types of problems, which start under the surface and rise to the top.
"Weight [on a pavement] can cause havoc," adds Lisa Whitney, vice president of property management for West Hartford, Conn.-based Konover Management Corp.
As a result, she says, developers generally customize their lots to traffic loads in order to avoid some of these problems. High-traffic areas such as truck loading and unloading areas and driving lanes require a thicker asphalt than parking areas do.
However, traffic load is not the only major cause of parking lot failure. Environment is an equal partner, causing a variety of surface problems. Block cracking, weak edges and water infiltration are all end results of the combination of sunlight and water on a pavement, Zimmer says, adding that these problems start on the surface and work their way to the bottom.
"Water infiltration is the biggest danger," Whitney adds. "It substantially decreases the lifecycle [of the pavement]." In order to prevent water from entering the system, it is critical that cracks be filled, and edges and drainage be kept in check, she says.
The best way to keep the lot in check and ensure that it remains in tip-top shape is with a planned maintenance program, Curtis says, describing pavement maintenance as taking care of surface problems by crack sealing, filling potholes and seal coating.
He distinguishes maintenance from parking lot rehabilitation by saying that pavement maintenance does not add strength back to the pavement system, while rehabilitation work, such as asphalt overlays, does.
Experts emphasize the urgency of sealing cracks and filling potholes in order to prevent further damage. In cold-weather climates, "immediate, temporary repair [should be done] to minimize damage from the winter," Stuckey adds. Then, once a year, he says, damaged sections should be repaired, or cut and replaced.
Weather does create problems in some cases, but parking lots are usually designed to fit the climate in which they are located. The biggest weather-related concern is freeze/thaw cycles, the experts explain. Pavement problems occur in the lot where water has gotten under the surface, has frozen and then expands. The more freeze/thaw cycles there are, the worse for the lot, Stuckey says.
Regardles of weather conditions, pavement will age. As it ages, the surface of the lot will become rough. Zimmer says this condition, known as raveling, generally happens three to four years after initial construction of the parking lot and every four years after that. When it does occur, he says, it is a good idea to apply a seal coat.
Zimmer estimates that the costs for parking lot preventive maintenance, which includes patching, crack sealing, seal coating and striping, range between 14 cents per sq. ft. to 16 cents per sq. ft. on a four-year preventive maintenance cycle. For more extensive work, in a four-year rehabilitation cycle, he estimates a cost of 60 cents per sq. ft. to 65 cents per sq. ft. for a simple overlay and up to $1 per sq. ft. for a more complex project.
Stuckey, who also talks generally about costs, says his estimates range up to 8 cents per sq. ft. annually to maintain a parking lot in the first eight to 10 years of its life. That cost increases to 12 cents per sq. ft. to 20 cents per sq. ft. after eight to 10 years when the company is beginning to phase in a resurfacing project, he says.
Common-area maintenance charges are expected to cover parking lot maintenance and rehabilitation, Stuckey says, adding that, as a result, overlays and other major repairs oftentimes are phased in.
Additional costs associated with parking lot maintenance come into play depending on who does the work: an in-house staff or an outside contractor. Whitney of Konover says her company generally handles all parking lot maintenance issues, as does Skinner & Broadbent, unless there are some unusual or unexplicable problems.
Other developers, such as CBL & Associates Properties Inc., solicit help more often from pavement consultants and local paving contractors. Don Sewell, director of mall operations for CBL, says he calls CHEC Consultants on occasion to inspect a shopping center parking lot as well as develop a maintenance plan for it.
Curtis of CHEC Consultants says development companies generally have someone in-house who handles routine parking lot maintenance such as filling potholes and sealing cracks. But on major projects such as overlays and other problem lots, a consulting/civil engineering company might be brought on board.
"Engineering costs generally are 3 percent to 5 percent of the construction cost," Curtis says, adding that on a project that is expected to cost $100,000, it might make sense to spend $3,000 to $5,000 on a specialist in the field.
There is no fountain of youth for parking lots; time is not on their side. Maintenance is the only hedge owners have against the costly alternative of total parking lot replacement.
MADVAC Quebec, Canada-based MADVAC litter collection vehicles can pick up cigarette butts, paper, bottles, cans and cups from parking lots and decks. The vehicles collect litter through a vacuum process, eliminating the need for hand collection. A full range of machines and accessories is available.
C&J Parking Lot Sweeping Warren, Mich.-based C&J Parking Lot Sweeping serves the southeastern Michigan market with 17 sweeper trucks. The fully insured company offers immediate free estimates and personal service. One-time cleanups, monthly contracts and hourly rates are available.
Trusco Manufacturing Co. With the Trueline Striper from Ocala, Fla.-based Trusco Manufacturing Co., owners can stripe their own parking lots or decks. A free demonstration video is available.
LSI Industries Inc. The Augusta(TM) lighting fixture from Cincinnati-based LSI Industries Inc. features glare-free illumination and durability. Its clear, ribbed, prismatic refractor is manufactured to provide more uniform ceiling brightness, thereby improving overall visibility within an enclosed parking garage. LSI also manufactures the Challenger(TM) lighting fixture. With its single size housing, the Challenger(TM) accepts both 400 Watt and 1000 Watt Reduced Envelope lamps and features both horizontal and vertical lamp orientations as well as a variety of reflectors to meet lighting requirements.
Tensar Earth Technologies Inc. Spectra(R) Pavement Systems from Atlanta-based Tensar Earth Technologies Inc. reinforce the parking lot subgrade. Structural geogrids are designed to increase the pavement durability and to reduce the number of potholes, ruts and cracks.
High Concrete Structures Inc. Denver, Pa.-based High Concrete Structures Inc. engineers, manufactures and erects precast concrete for multi-level parking structures. The company's new 15-foot-wide double tee reduces the number of tees and connections needed. Concrete can be cast in virtually any color, form or texture and erected year-round.
PRT-Group BCR2000 Rejuvenator/Sealer from Sharon Hill, Pa.-based PRT-GROUP is a one-step chemical process that rejuvenates asphalt pavement. A non-coaltar seal coat, it is applied with specialized equipment and has a black finish.
McCue Corp. The Ex-Ten Cart Management System from Salem, Mass.-based McCue Corp. provides shelter for carts and customers. It is available in eight configurations and a wide variety of colors. The modular-designed system uses water as ballast, which eliminates the need to drill holes in the parking lot. ChildZone PLUS utilizes an Ex-Ten system and several nearby parking spaces to create a special zone for shoppers with small children.
Unistress Corp. Pittsfield, Mass.-based Unistress Corp. specializes in the design, production and construction of precast/prestressed structural concrete. The company also offers design/build construction services.
MPS Corp. Pittsburgh-based MPS Corp. offers a range of design/build services for parking structures. These include consulting, site analysis, design, engineering, construction, restoration, financing and operations. The company works with developers, hospitals, universities, municipalities and architects throughout the United States.
Asphaltic Concrete (AC): Plant-mixed asphaltic concrete, well graded, crushed aggregate with a smooth surface texture.
Block cracks: Block cracks are interconnecting cracks that form a pattern much like giant fatigue cracks. They are actually combined severe, non-load associated longitudinal and transverse cracks that have intersected to form large pavement blocks, 3 feet to 10 feet across.
Bonding failures: Bonding failures of asphalt pavements are usually in the form of slippage, which is the lack of bond between two layers of surfacing causing cracks in the upper layer; or spalling, which is the lack of bond between two layers causing the "flaking" or "loss" of the top surfacing.
Crack sealing: Crack sealing can be used for two different reasons in pavement maintenance. One is a treatment to seal the cracks in order to prevent moisture intrusion into the pavement. The other is preparatory work to other treatments, such as overlays or the use of fabric.
Digouts: Digouts are localized pavement repairs to correct structural deficiencies. The pavement is saw-cut in rectangular patterns, and all material within the rectangle is removed and replaced.
Fabric: In pavement terminology, fabric refers to a crack-retardant fabric membrane that is placed on the surface of an existing pavement under a new overlay or a soil stabilization fabric (geotextile) that is placed over unsuitable soils.
Fatigue cracks: Fatigue cracks are commonly called "alligator" cracks because they resemble the lines on alligator skin. They are almost always a maximum of 8 inches apart but can be as small as 1 inch. They are almost always present in an interconnected group. You will seldom see fatigue cracking in parking stalls. Fatigue cracking is a direct result of excessive bending of the pavement surface under load.
Flushing: Flushing on asphalt pavements appears as a smooth, shiny surface in the wheel path of a main drive area of a parking lot. It is a result of an over-asphalted, possibly unstable, asphalt concrete mix. If a pavement is going to experience flushing, it usually happens within the first year of use.
Inter-layer: Any material placed on the surface of an existing pavement and sandwiched under a new pavement layer.
Overlay: The placement of asphaltic concrete mix over an existing alphaltic concrete or portland cement concrete surface.
Potholes: Potholes are a severe manifestation of pavement fatigue cracking that results in a total loss of asphalt concrete surfacing in a localized area, creating a hole in the road. It is not uncommon to have a pothole extend through or into the aggregate base.
Raveling: Raveling is the loss of aggregate from the asphalt concrete pavement surface as a result of an abrading action of vehicle wheels. It usually requires the presence of water. Raveling will appear as a rough texture on the pavement surface, or craters in the surface left as the coarse aggregate pops out of the surface.
Rutting: Rutting is a depression of the pavement in the wheel path. It usually is continuous throughout a pavement but sometimes occurs only in the outside wheel path or wheel path most susceptible to water intrusion. Rutting is structural failure due to excessive loading for that pavement structural section.
Seal coats: Seal coats or maintenance seals are generic terms for any of a number of surface coatings such as coal tar, filled asphaltic sealers, Gilsonite seals, etc., all aimed at protecting against moisture intrusion and raveling.
Source: Pavement Maintenance Practices Manual