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MTDC Portable Vehicle Washer Interim Report

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Initial Field Testing

From August 6 through 9, 2002, the prototype vehicle washer was set up and operated at the Cathedral Fire camp near Darby, MT. The vehicle washer was set up at the Deer Creek trailhead about 1 1/2 miles from the fire camp on the Bitterroot National Forest. A contract vehicle-washing system was also set up and operating nearby.

The vehicle-washing system was set up on a level spot at the trailhead. All the used water ran down to one corner of the barrier and was pumped into the settling tanks (figure 4). The one drawback of the location was that vehicles could not drive through the washing station. Instead, they had to drive forward onto the mat and back out. This presented problems when other vehicles were lined up and had not left enough room for the vehicles being washed to turn around and leave.

The camp philosophy was that all vehicles would be washed before entering the forest on the first day. Vehicles were not washed afterward so long as they were traveling between the fire and fire camp. All vehicles were to be washed before leaving camp during the fire camp's demobilization. The intent was to wash vehicles during the fire's demobilization, from August 7 to 9.

A total of 74 vehicles were washed. The vehicles included cars, pickup trucks, sport utility vehicles, hotshot crew vehicles, fire engines, and a school bus. The wash water supply tank had to be refilled three times (about 175 gallons per refill).


The washing system did an excellent job. It took about 2 to 3 minutes to wash a standard pickup truck, sport utility vehicle, or car. Hotshot crew vehicles, fire engines, or tankers took about a minute or so longer. The contractor needed about 10 minutes per vehicle to wash them. The contractor had a very-high-pressure washing system (3,000 pounds per square inch) that used hot water. He had no containment system. All the used water and debris was left at the site.

The MTDC undercarriage washer did an excellent job, as evidenced by the amount of dirt and "dirty" water was being used to wash the vehicles, they appeared clean after drying and were mud free. After returning to the center, we found that the settling tanks had a lot of sediment in the bottom and it was difficult to drain them. It is recommended that tanks be partially drained daily to remove sediment, preferably early in the morning after the sediment has settled overnight.

Filter Analysis

Photo of a filter with seeds and debris trapped in it.
Figure 9--filters collected noxious weed seeds and other debris from the wash water.

The filters used on the last day of testing were kept for analysis. About 40 vehicles were washed that day. The filters were backflushed with water to remove all the particulate, seeds, and debris that had collected on them (figure 9). This material was sent to the Montana State Seed Testing Laboratory in the Department of Plant Sciences at Montana State University, Bozeman, MT.

The laboratory's results indicated that the following seeds were collected in the 20-micron filter:

  • Bluebunch wheatgrass (Pseudoroegneria spicata)
  • Bluegrass (Poa spp.)
  • Crested Wheatgrass (Agropyron spp.)
  • Orchardgrass (Dactylis glomerata)
  • Reed Canarygrass (Phalaris arundicacea)
  • Sedge (Carex athrostachya)

No seeds were found in the 5-micron filter.


The initial testing of the vehicle washer proved that the overall concept of the prototype washer was sound. Vehicles were washed in about 2 to 3 minutes, depending on the vehicle's size and the amount of dirt on it. The undercarriage washer did a good job. All of the mechanical components (pumps, tanks, nozzles, and generators) performed as planned. The filters collected seeds of various sizes and species.

Some items need to be addressed before the design of the vehicle-washing system is completed.

Undercarriage Washer--The system's location at the test site required vehicles to drive over the undercarriage washer twice--once when driving onto and once when backing off of the mat. Two washings appeared to do a good job in removing dirt and debris underneath a vehicle. Ideally, the mat would be located where vehicles could "drive through." This would allow only one undercarriage washing, which may not be enough for a thorough cleaning. To address this issue, a second undercarriage washer could be placed on the opposite end of the mat to ensure that the underside would be washed twice.

Photo of the sump pump used in the field test showing the debris that clogged the pump. Inset picture of the filter sock created to trap debris.
Figure 10--The sump pump that drew water from the mat clogged periodically with debris such as pine needles, twigs, and grass. A filter sock was fabricated to prevent debris from entering the sump pump.

The overall effectiveness of the undercarriage sprayer needs to be addressed. MTDC is developing a method to determine whether the undercarriage sprayer is providing complete coverage and whether the sprayer is effective in the areas it covers. One method could involve covering the bottom of a vehicle with a fluorescent dye and then driving the vehicle over the undercarriage washer. Photographs of the vehicle's undercarriage could be taken using a fluorescent light to show the location of any remaining dye.

The center is also investigating using water from the high-pressure pump rather than an electrical motor to drive the oscillating mechanism for the underbody washer. This change would eliminate the need for the electrical motor, flex shaft, and motor control, reducing the cost.

Sump Pumps--The sump pump used to pump the water from the mat clogged occasionally because of pine needles and other debris. To solve this problem, MTDC designed and fabricated a filter sock to be slipped over the sump pump, keeping any large debris from entering the pump (figure 10).

Ramp--A small piece of 2- by 6-inch steel channel was used to protect the hoses and flexible drive shaft when vehicles drove onto the mat. A piece of conveyor belting was placed over the channel to make it easier for vehicles to drive over it. However, a more permanent solution should be developed and fabricated before the next test.

Petroleum Products--Small amounts of petroleum products may come off vehicles during washing. Oil-absorbent pads may be placed in the settling tank overflow barrel to collect all petroleum products as they float to the surface. The pads can then be disposed of according to local regulations.

Drawings and Operator's Manual--Fabrication drawings and equipment specifications will be developed soon after the system's design is final. These materials will allow districts and contractors to build their own washers. An operator's manual will be developed that addresses setup, operations, maintenance, and cleanup.

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Updated: 4/14/2014
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