Better surroundings

May 4, 2015

Idaho DOT makes enhancements to brine maker

The Idaho Transportation Department splits the state into six districts to make maintenance more manageable.

Each district can be vastly different from its counterparts in population, weather patterns and terrain. District 1 consists of the five northern-most counties and borders Washington, Montana and Canada. The district has approximately 1,600 lane-miles that cover farmland, mountains and national forests. 

The winters are at best unpredictable. Each year leaves you wondering if it will be dry and bitterly cold or relatively moderate with heavy snowstorms. The driest region in District 1, located south of Coeur d’Alene, receives an average 45 in. of snow. Lookout Pass, located on the Montana-Idaho border, gets the highest amount at 313 in. in an average winter. Despite these extremes in precipitation, the lowest average temperature is 24°F. Taking this information, the district does its best to find the most efficient, cost-effective ways to keep the roads safe for the traveling public.

Less shed, more swag

Management started looking into alternatives to magnesium chloride to find a more cost-effective deicer that would perform in the area. Salt brine seemed to have an acceptable temperature range, and while figuring cost, it was estimated that we could produce and deliver brine for $0.14/gal versus an average of $0.74/gal of magnesium chloride. After some research and a few visits to neighboring agencies that were using salt brine (there were not many in the Northwest), District 1 purchased a brine machine, plastic enclosure, concrete slab and plumbing for a bid price of $32,000. A 5,000-gal tank trailer also was purchased for $25,000 to deliver product across the district. The vegetation crew (two employees) was chosen to run the program due to their experience in plumbing and chemical application. In addition, this would utilize a crew that had no specific winter function and not diminish the road crews. In the 2006-07 winter season 375,000 gal was produced and used in the Coeur d’Alene area on a trial basis. The product performed better than expected, and the brine program was extended to the entire district.

The machine was set in a shed with a roof that opened with air-operated arms, complete with an air compressor, heaters, lights and electrical outlets. A backhoe with a clamshell bucket was used to transport the salt from the storage shed approximately 100 yd to the brine maker. 

Flaws in this system were almost immediately evident. While transporting the salt, about 5 lb was spilled out of the bucket resulting in approximately 6 tons of salt wasted per million gallons of brine produced. At a cost of around $100/ton, and the effect to the environment, this was unacceptable. Inside the shed we noticed that all equipment, outlets, heaters and lights were subject to an extreme amount of corrosion and needed to be replaced regularly. Also there was a problem with top loading the salt into the brine maker. Every time a load was dumped into the machine, the saturated brine level would rise to accommodate the salt being added to the tank. This rise in 26.4% brine would flow through the down tubes and skew the salinities because there was no adjustment to the freshwater valves, resulting in inconsistent percentages to the finished product.

In 2009, it was determined that the facility needed to be upgraded to meet the growing demand of 1.75 million gal/year and to address the issues mentioned previously. After careful deliberation and research, goals were established for the new facility: 

  • The facility should be attached to the storage building to eliminate salt lost during transport; 
  • A new, larger containment will be built attached to the brine building to collect spilled brine, hold up to eight 10,000-gal tanks and recycle the collected brine back into the brine machine; 
  • A system must be designed to mechanically stabilize salinities without the use of expensive computer-controlled devices or a new machine; 
  • All electrical outlets and accessories must be corrosion-resistant due to the high humidity and salt content; 
  • The parts used must be easily accessed, repaired and available
  • for replacement; 
  • The loading area should accommodate two trucks at a time and be easy to operate for all employees; and
  • The brine building will be designed with restroom facilities, office area, mechanical room and emergency wash station. State forces will be used whenever feasible to keep cost as low as possible.

District 1’s bridge and building crew started laying foundations for the new facility and concrete containment at the north end of the salt-storage building. To keep corrosion to a minimum, the brine room was separated from the office, mechanical room and restroom. All light fixtures were sealed in plastic, and all switches and outlets were placed in the office to limit their exposure to the corrosive environment. Radiant floor heating was installed instead of an overhead unit, again to keep the heaters from corroding. All exposed metal items are galvanized, painted or made of stainless steel. The walls were of wood construction, paneled in plywood and painted with an epoxy, waterproof paint so they could be washed with a hose and brush.

Outside, the containment was built with a 2% slope to the center so all rain and contaminated water drained into a grate that feeds into a sediment trap located in the loading area. This also is the collecting point for any brine spilled during loading. Attached to this drain is a supplemental drain in the brine room that collects any spilled material and all wash water used for cleaning. The sediment trap then drains into a 1,500-gal holding tank that can be pumped back into the brine machine to recycle all wastewater.

The next hurdle to overcome was stabilizing brine salinities. One option was purchasing a new machine with computer controls to monitor salinity, but these machines cost from $40,000 to $80,000 or more. It was decided to create a mechanical feed for the existing machine, which was already paid for. After some research into agricultural augers, a system was created using a 6-in. plastic auger in a PVC pipe. It was powered by a 5-hp electric-over-hydraulic pump with a variable-speed valve and attached to a spinner motor from a plow truck. By using this combination, all parts were easily obtainable, on-hand and relatively inexpensive. The auger was placed through the adjoining walls of the brine-maker and salt-storage buildings. A hopper was considered but omitted for maintenance purposes, as it would have to be hand-shoveled if a breakdown occurred. Instead, the auger was placed low to the floor, above ground. Salt was then placed on top of the auger with a loader. At full speed, the auger is capable of moving 6 tons of salt per hour to keep up with the machine’s 5,000-gal/hour production and only needs to be reloaded every 45 minutes.

In 2011, after operating for two years at a production rate of 3,200 gal/hour, the Varitech SB600 machine was upgraded with a 2-in. plumbing kit giving it a maximum capability of 5,000 gal/hour, depending on available water pressure. This upgrade reduced the number of man-hours required to fulfill growing demand of more than 2 million gal/year. 

In addition, a larger discharge pump was added to the machine to replace the stock unit. Brine discharge was routed through the ceiling of the brine building to top-load the brine storage tanks. The major advantages of this system were three-fold: all brine in the discharge line would drain back into the brine tank when the machine was turned off, so no liquid would leak into the ceiling; the plumbing was easy to access in the rafters of the building instead of being placed in concrete; and by filling one tank from the top, it was possible to fill all other tanks with gravity instead of routing the brine through the loading pumps. 

The final component was the two loading pumps. They were placed on each end of the loading platform 60 ft apart. A 10-hp electric motor connected to a 3-in. poly pump makes up each of the loading stations and can fill a 5,000-gal tank in less than 25 minutes. The suction line for all tanks run in a series, making the system capable of filling two trucks simultaneously from one tank or a combination of all tanks depending on which valves are open. Both trucks sit over a sloped loading pad that drains into the brine reclamation tank.

The results are astounding. The facility worked from day one and has performed flawlessly since then, as long as only kiln-dried salt is used. Production remains more than 2 million gal/year with only a two-person crew to produce the brine and coordinate the transportation. The total cost of the facility was less than $125,000. At a savings of $0.60/gal versus magnesium chloride, the new facility paid for itself in the first trial year where only 375,000 gal was produced. By looking at the process as a whole and utilizing on-hand materials and labor, District 1 was able to design a system that was cost effective, easy to use and maintain and also environmentally friendly. WM

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