Recent Developments in PICP Cleaning Present Owner Solutions & Contractor Business Opportunities

By Sheryl Jackson

Equipment Innovations Support Cost- and Time-Effective Restorative Maintenance

The puddles on this PICP indicate the start of surface clogging due to sediment in runoff received from adjacent impervious pavements. Why not clean them as well?

Permeable interlocking concrete pavement (PICP) reduces stormwater runoff volumes and rates, while filtering pollutants. PICP has an admirable track record in paying for itself by reducing or eliminating detention ponds. In older cities with combined sanitary and storm sewer system, PICP presents a cost-effective means to reducing flows to wastewater treatment plants and related processing costs.

However, when civil engineers, landscape architects, architects, and contractors recommend PICP, owners may resist as a result of their own or someone else’s experience with PICP clogging. In other cases, the owner won’t receive education on what’s required to clean PICP, or if received, doesn’t want to spend money for surface cleaning. These situations lead to lack of maintenance and clogging.

Besides sediment from vehicles, eroding asphalt surfaces present another asphalt sediment source. If not cleaned regularly, over years of neglect, sediment builds up in the PICP joints and bedding.

The notion of clogging means that water puddles on a PICP surface rather than infiltrating quickly. There may be some infiltration into the surface and base, but it is very slow. In many cases, water puddles in places on the surface, and then moves to another area that more rapidly infiltrates the stormwater.

The biggest factor effecting clogging is the area of contributing impervious pavement delivering sediment to the PICP. There are many projects with no contributing drainage area or CDA. They usually need little if any cleaning. In contrast, sediment from vehicles and especially deteriorating asphalt surfaces deliver small particles that enter the PICP joints and slow infiltration.

Owners don’t think of the PICP as a system, instead, they view it as “just another pavement” that requires little maintenance, says Matt Otero, chief operating officer at Designs by Stonescapes in Commerce City, Colorado. “There is a lack of education about how PICP works and why routine maintenance is important.” PICP is a drainage system that must be maintained the same way any other type of filtration system would, he says. “There should also be some thought put in to the design of surrounding landscape areas to minimize runoff debris.”

Inexpensive routine PICP maintenance includes brooms, leaf blowers, rotary brushes, and shop vacs. More expensive methods for larger areas involve using regenerative air machines that, like these other methods, remove loose dirt, leaves, and other debris from pavers and from the top of joints before it enters them via rain and tire traffic. This keeps the pavement infiltrating as designed with minimal replacement of joint aggregate. Unfortunately, most PICP and public agencies owners don’t follow a routine maintenance schedule. So when clogging occurs, more intensive restorative maintenance is required that involves removal and replacement of sediment and joint stone. This is a more costly, time-consuming process.

Before and after cleaning with the FX-20.

The Interlocking Concrete Pavement Institute (ICPI) members, staff, and other organizations have researched and witnessed demonstrations on the effectiveness of vacuum machines withdrawing sediment and aggregate from 3-inch deep (~80 mm), ~3/16-inch (5 mm) or larger width joints typical to many PICP projects. The majority of machines are effective, but a bit inefficient because they require several passes to remove these materials. Moreover, the sediment often binds the aggregate, making both difficult to withdraw. Fortunately, recent research and cleaning demonstrations have uncovered three innovative approaches to restoring infiltration of clogged PICP surfaces. These require only one pass over the pavement, regardless of joint size and depth.

At a demonstration in St. Louis, the TYPHOON on the right blows out sediment and soiled aggregate from the joints. A vac machine on the left picks up the withdrawn materials and sends them to a sewer truck.

“We install a lot of permeable pavers and offer maintenance agreements for them,” says Mr. Otero. “Unfortunately, by the time most customers ask for maintenance, the amount of sediment in the joints requires a restorative cleaning rather than simpler routine maintenance.” To handle larger, more complex jobs, he experimented with a variety of vacuums and vacuum trucks, but settled on a less expensive, more portable machine that can remove aggregate and debris from PICP joints in one pass.

A modified Ditch Witch FX-20 cleans PICP.

“I modified a Ditch Witch FX-20 that can be towed behind a pickup truck and be taken into areas that don’t accommodate larger equipment,” says Mr. Otero. College campuses that use PICP in common areas, walkways and patio areas, and small parking lots are two examples of areas that require access using a smaller vehicle. “The vacuum heads and hoses also work well in corners and up against walls where sediment accumulates.”

Before-and-after cleaning surface infiltration rates at a PICP manufacturing site in St. Louis. The infiltration rates were determined using ASTM C1781 Standard Test Method for Surface Infiltration Rate of Permeable Unit Pavement Systems.

Mr. Otero experimented with different sized vacuum heads that rendered different cleaning levels. “A 24-inch (600 mm) diameter vacuum head that pulls half of the joint material out works well for pavements that are less dirty. But a pavement that has gone five years with no cleaning requires a 6-inch (150 mm) head that pulls most of the joint material out,” he says. The equipment can easily be operated by a two-man crew with minimum training. In fact, he cross trains his employees to handle the restorative maintenance as well as installation to give him flexibility when scheduling work.

Moving from Colorado to Minnesota, the six-year effort to develop TYPHOON, a compressed air system to clean PICP and remove joint material, began with Steve Jones, inventor and president of Pave Tech, located near Minneapolis. He discovered effectiveness and simplicity of using compressed air without water to clean joints. “The compressed air blows the joint material out just as a water pressure based system, but there is no sloppy mess when using air and no loss of surface as one would get from water pressure washing.”

The TYPHOON has a rotating wand with nozzles that is attached to a large 115 HP air compressor that focuses controlled, high-pressure air in the joints to remove clogging sediment, debris, and aggregate. It is followed by the PAVEVAC, which is attached to a high-volume high-suction (27 in. or 675 mm of Hg) vac truck or trailer to complete cleaning the joints and surface by removing loosened debris and aggregate from the PICP surface. “A three-man crew can remove silt, debris, and joint material on 1,000 square feet (100 m2) in about an hour,” says Mr. Jones. “It takes us less than an hour to train someone to properly use the equipment.” Training includes how to work with air compressed at 200 psi (1.4 MPa), a truck-mounted vacuum exerting 27 inches (68 mm) of Hg suction, plus safe operation of hoses.

Badger Daylighting adapts their equipment with a high pressure spray and vac head that delivers sediment and soil aggregate to one of their trucks in San Antonio, Texas.

Moving to Calgary, Alberta, the home of Badger Daylighting offers its well-known excavation trucks across Canada and U.S. Known as Badgers or Badger Hydrovacs, they use high-pressure water and vacuum systems mounted on a truck to remove soil and expose buried infrastructure or prepare an area for future work. This daylighting method for utility lines practically eliminates risk of damaging pipes and wires and risk of worker injury associated with hydraulic excavation equipment.

Before-and-after cleaning test results using C1781 compared to a regenerative air machine demonstrates the potential for Badger equipment to clean clogged PICP. Regenerative air machines are useful for routine maintenance, i.e., keeping PICP from clogging.

The newest innovation for the company is a modification of the vacuum hose that can be used to clean PICP. “Specialized nozzles and cleaning techniques keep the water spray focused on the pavement to act as a high-powered carpet cleaner that removes stains, graffiti, and clogged joint material,” says Tim Reiber, vice president of sales and marketing for the company. “The pressure can be set to whatever level is needed, and the truck’s large tank can hold 1,500 to 1,800 gallons of water and 11 (cubic) yards of debris, which means a large area of pavement—200 to 300 linear feet—can be cleaned and joint material removed in an eight-hour day.”

PICP contractors who would like to offer PICP cleaning and maintenance services should evaluate equipment options carefully. They should keep in mind the size of projects they’d like to address and match equipment to them. Stormwater regulations are placing increased emphasis on inspection and maintenance. This provides a business opportunity for maintenance contracts. Developing such opportunities will involve pricing labor and equipment costs for cleaning a range of PICP areas with adjacent uses, landscaping, and pavements contributing runoff and debris.

Besides cleaning the joints, Badger’s high pressure spray also cleans the paver surfaces.

Mr. Otero focused on equipment to handle restorative maintenance informed by the type of permeable pavements he expected to maintain. Spending the time and money to build exactly what he needed was worthwhile, he says. “Not only does the maintenance service ensure ongoing performance of the permeable pavement, but general contractors like the fact that they don’t have to protect the pavement as they finish construction of an area,“ he says. “The ability to offer maintenance services to my installation customers, general contractors, and other PICP owners is a business decision to grow my business.”