Still another pothole and pavement repair alternative is spray injection patching, sometimes referred to as velocity feed patching. Loyed Woodland, The Pothole Medic, Brockton, MA, is a contractor who generates virtually 100% of sales through pothole and pavement repair. He says half his repair work is on commercial and industrial properties while the other half is on roads for municipalities. And he does it all from the cab of a Wildcat spray-injection patching machine he has tweaked over the years to better perform some of the things his clients demand.

"The industry has been repairing potholes the same way for 70 years," Woodland says. "Why would anyone continue to do that knowing how ineffective it is? Velocity speed patching (also known as spray-injection patching) is the wave of the future. There's no question about it in my mind. But there needs to be more education of how this equipment works for that to happen. That understanding, plus some of the tweaking we've done over the years, makes this approach the way to go when repairing potholes."

While spray-injection patching machines differ, they are available in tow-behind, truck-mounted, and stand alone vehicles. The process is similar on all equipment and involves air pressure blowing water and debris from a pothole, spraying a tack coat of binder on the insides and bottom of the hole, blowing asphalt and aggregate into the hole at 50 to 90 mph, velocity compacting from the bottom up, and then covering the patched area with a layer of aggregate. Pavement can be opened to traffic immediately.

Woodland owns one Wildcat spray patcher, which he bought in 1996. It requires only one person to operate on the road and two in commercial areas to sweep back in any material blown out "and to watch for pedestrians who are notorious for walking where they don't belong despite safety restrictions put up."

While he doesn't know how many repairs the machine made last year it did put down 550 tons of stone and more than 21,000 gallons of emulsion.

"That's a lot of work for one machine," he says.

He says the spray-injection technique was intended primarily for municipalities because it's the least invasive repair method, its cost-effectiveness, and most important the safest for the operator who is now seated in a climate controlled cab for more productivity. Woodland says he has accomplished nine consecutive months of patching on high- and low-speed roadways and commercial parking areas with zero failures. He says spray-injection machines also address the pre-mentioned perimeter settlement and create a true plane with a seamless patch creating a permanent repair.

"What most people don't do when they repair potholes is they don't address the perimeter problem and as it continues to be a pothole the perimeter problems prevent any pothole repair from being successful," Woodland says. "You repair the pothole but the traffic has a tremendous amount of impact on that repair and the pavement surrounding it.

Traffic puts pressure on the areas and produces a depression, which gives water a place to collect and the problem just continues. The spray injection method addresses the problem by repairing not only the pothole but the perimeter as well, leaving behind a new plane, a new surface and no depression."

He says he often conducts demonstrations for property managers and city officials and often ends up with contracts on the spot.

"Property managers like it because it's less inconvenient for them," he says. "Parking lot areas are closed for shorter times, traffic is disrupted less on roads, and there's a longer patch life. All these things combine to sell the process. The process also sells itself because people are really impressed when they see it work."

Woodland says spray-injection machines are the future of pothole and pavement repair largely because the machine, though it is expensive, can reduce the manpower needed on the job, repair more pavement quicker, expose workers to traffic less time, and disrupt traffic and the public less time. He says cities (and contractors) will be able to reduce their overhead by hiring fewer people to get the work done or can reallocate that labor to other jobs, improving productivity.

He says that while the spray-patching process has been around almost 40 years it hasn't taken hold because it needs to be tweaked (as he has done) and its operators need more training than is generally provided.

Woodland says operators need to better understand both the chemistry of emulsions and the electrical charges of the stone to use this process as effectively as possible.