Road salt customers often have "large" storage facilities exceeding 3,000 tons. These are dwarfed by truly large regional distribution stockpiles operated by salt companies which can exceed 100,000 tons. The two types of facilities share a common need to manage the stored salt safely and in an environmentally protective manner (i.e. on an impermeable pad, under cover to prevent intrusion of rain and snow onto the stored salt).
In 1972 the Salt Institute developed the Sensible Salting Program. This program is directed at government agencies responsible for winter street and highway maintenance. It provides training in the proper storage and use of deicing salt with particular attention to application rates, spreader controls and equipment maintenance. As part of this program, the Salt Institute's Salt Storage Handbook provides recommendations for the environmentally sound design and operation of small salt storage facilities. The recommendations are intended for the type of salt storage facilities operated by state and local government agencies. These small storage piles typically contain 2,000 to 3,000 short tons and can usually be placed under structural cover without great difficulty.
The use of deicing salt is necessary to maintain high levels of winter safety and mobility on streets and highways throughout the North American snowbelt. Because its use is concentrated during the three months of winter, large storage piles must be maintained by salt producers at distribution sites. Adequate, strategically located storage facilities ensure prompt, reliable delivery of salt to winter maintenance agencies even during periods of very high demand created by unpredictable and severe winter weather conditions. Large distribution salt storage sites raise environmental concerns similar to those at smaller, government agency piles. Although many of the larger salt storage piles are operated in a way that minimizes environmentally harmful discharges, the Salt Institute saw a need to develop the following formalized, voluntary guidelines incorporating the best management practices of the salt industry for distribution stockpiles. These voluntary guidelines apply to Salt Institute member-companies, and their agents, with facilities in Canada or the United States.
In order to ensure that salt contained in storm water runoff from a salt storage site does not harm the environment, two fundamental requirements must be met. First, the stockpile must be situated on a low permeability pad and base to prevent downward seepage of brine to ground water. Second, either precipitation must be prevented from contacting the stockpiled salt or, as an alternative, storm water runoff from the stockpile must be contained and disposed of, reused or discharged in accordance with a regulatory permit. The Salt Institute Voluntary Storage Guidelines for Distribution Stockpiles require that the stockpile is covered at all times except when salt is added to the stockpile or loaded out for shipment. In addition to these requirements, the site must comply with all applicable federal, state and local environmental discharge regulations and permits. A containment system may be used to collect and hold all storm water runoff for disposal, reuse or discharge in an approved manner.
These voluntary guidelines are designed to minimize the potential impact of salt on the environment at large salt storage piles of the type found at salt distribution facilities. The following sections specify the minimum standards required by the Salt Institute for constructing or operating a distribution salt storage site.
Distribution stockpiles newly acquired as the result of major business acquisitions or new leases must immediately comply with all conditions specified in these guidelines, with the following exception. Newly-acquired stockpiles must within three years of the date of acquisition or lease comply with section I A, Pad design and construction requirements; and sections III C, Covering procedures for stockpiles or III D, Storm water containment for stockpiles.
I. PAD DESIGN
A. Design and construction requirements.
1. Site evaluation must include an examination of conditions such as topography, hydrology and soils to determine potential environmental impact on surface water and groundwater.
2. Site drainage systems must prevent contact between salt and storm water runoff from adjacent terrain.
3. Design and construction of subbase and pad must be adequate to ensure pad stability and proper drainage.
4. Pad size must be adequate to contain the quantity of salt that will be placed at the site and to provide maneuvering room for trucks, loaders and other equipment.
5. The subbase and pad must be constructed to achieve the lowest permeability consistent with current asphalt construction techniques.
II. STOCKPILE CONFIGURATION
A. Stockpile configuration is determined by several factors including site characteristics, equipment and unloading methods. Prevailing winds must be considered when building the pile to ensure that the working end of the pile, once open, will be at the downwind end.
1. Conical shaped pile.
a. Salt is placed on stockpile with a fixed overhead conveyor discharging at one point. Due to its shape, a conical pile cannot be covered effectively with flexible covering material. Use of conical piles is not recommended.
2. Windrow-shaped pile.
a. Salt is placed on stockpile with a movable stacking conveyor or clamshell-equipped crane. Constant width of the windrow must be maintained at all times.
b. Upon completion, the peak of the windrow should be leveled to a nominal width of ten feet with a small bulldozer, and the crown graded to a four- percent slope. The purpose of this action is to prevent water accumulation on top of the pile and to minimize unevenness that could contribute to wind turbulence and subsequent damage to the covering material.
3. Radial or kidney shaped pile.
a. See II.A.2 windrow shaped pile.
4. Sugarloaf shaped pile.
a. Salt is placed on stockpile by transporting it up onto the pile in dump trucks and/or rubber-tired front-end loaders. It is then leveled or pushed with a bulldozer to obtain the desired height, eliminate tire groves and consolidate the approach ramp. The stockpile crown must be graded to a minimum four percent slope.
III. BEST MANAGEMENT PRACTICES AND STORM WATER CONTROLS
A. Dust control/air emissions.
The facility must meet all applicable government regulatory standards and must take appropriate action to minimize generation of dust and other air emissions.
1. Control of air emissions must incorporate consideration of such factors as meteorological conditions, salt discharge methods and preventative measures.
2. The facility operator must conduct operations in a manner that is sensitive to other industrial, commercial, public and government facilities or residential areas adjacent to or near the salt storage site.
3. Dust suppression practices for conveyor discharges including self-unloaders, rail cars, screening stations, transfer points, and other material handling operations are:
a. Use an elephant trunk or spout when available.
b. Maintain the minimum feasible vertical distance between the end of the spout or conveyor and the highest point on the ground or stockpile.
c. Shield or enclose all transfer points on conveyor systems.
4. Clamshell, end-loader, truck, bulldozer or other equipment operations.
a. Ensure that crane or other equipment operators lower the clamshell or bucket to the minimum feasible distance from the pile before discharging a load of salt.
5. Salt spilled by arriving or departing trucks, railcars or other vehicles or vessels must be cleaned up promptly.
6. Salt must be loaded into trucks within the designated pad area and loads must not exceed the legal or physical capacity of the trailer or box.
7. Truck tailgates must be properly adjusted to avoid spillage and the tailgate apron must be swept clean if there is spillage.
8. All trucks must be tarped before leaving the site.
9. Roadways must be swept clean to minimize traffic-generated dust.
B. Noise control.
1. The need to operate must be balanced with the amount of noise generated.
a. All mobile equipment must have mufflers meeting design and manufacturing criteria consistent with intended use and must be in good operating condition.
b. Whenever possible, salt deliveries to the site and shipments to customers should be scheduled during normal working hours.
c. Truck access and routing into and out of the facility should follow a pre-designated route that has least impact on the neighborhood.
d. Back-up alarms should meet regulatory standards.
C. Covering procedures for stockpiles.
1. Distribution stockpiles are covered to ensure high quality of the salt and to prevent precipitation contact and discharge of storm water runoff from the storage pile. All stockpiles must be covered to prevent precipitation contact except when receiving salt, building the stockpile, or loading out to customers.
2. Types of covering include canvas, polyethylene films, fabrics made of synthetic fibers, and combinations of these materials used as complete covering systems.
a. Covering must be appropriate for the size and shape of the stockpile, and for the methods of receiving salt shipments and loading out to customers.
b. To minimize contact with precipitation, the stockpile must be covered in sections or stages as salt is added to the stockpile.
c. Seams must be watertight and resistant to damage in winds up to 69 miles per hour.
d. Cover retention systems must meet selection criteria consistent with intended use and must be installed in accordance with manufacturer's recommendations and operated in a manner that will ensure physical integrity of the cover.
e. Covering must be properly maintained to prevent precipitation from contacting the salt.
3. Methods of sealing the cover to the stockpile pad.
a. The perimeter of the stockpile cover must be sealed to the pad with ballast to prevent washout of salt from the toe of the stockpile. Ballast must be placed high enough on the sides of the stockpile to minimize slackness in the cover as salt shifts and flows beneath the cover down to the perimeter of the stockpile.
b. Salt must not be used as ballast because it will dissolve quickly when precipitation runoff from the cover flows to the perimeter of the stockpile.
c. Maintain complete perimeter cover ballast until the stockpile is exhausted.
4. Loading out for shipment.
a. Remove covering at the working face just high enough to load out the day's shipment. This will minimize moisture absorption by the salt and provide security to the cover if the wind direction shifts toward the working face.
b. The working face should be maintained perpendicular to the long axis of the pile by loading alternately left/right and right/left.
c. Avoid creating a horseshoe shaped working face that results from removing the center of the pile and leaving extended edges or aprons.
d. Chunks of salt that form as the crust of the pile breaks up must be crushed and blended into the pile and not allowed to accumulate.
e. Adequate covering material must remain at the lower edge or toe of the working face to permit maximum possible resealing of the edge of the cover when operations are completed for the day. However, care must be taken to avoid damage to covering material caused by cascading salt from the upper section of the working face.
f. The working face must be established and maintained at the downwind end of the stockpile whenever operationally feasible.
D. Storm water containment for stockpiles.
1. Earthen collection basins must be synthetically lined and holding tanks corrosion-protected to assure continued low permeability.
2. Capacity of storm water containment systems must be based on proper design principles incorporating historical precipitation event records and discharge frequency to assure adequate capacity, and must comply with all regulatory requirements.
E. Site maintenance
1. The facility must be maintained in a manner that will assure physical integrity consistent with original design criteria.
a. Regularly inspect pad, drainage, collection and other systems affecting potential discharge of storm water runoff from the site.
b. Perform preventive maintenance such as periodic resealing of the pad to ensure non-degradation of the low permeability of the pad and base. Expansion joints must be resealed when necessary.
c. Take other corrective action as needed to maintain storm water discharges at levels consistent with best management practices and/or discharge permits.
F. Permitting
1. All distribution stockpiles must obtain appropriate permits
a. Methods of discharge or disposal of storm water include discharge to surface waters, storm sewer, sanitary sewer or combined sewers, underground injection well, solar evaporation and recycle or reuse.
b. Each facility must monitor discharges and maintain appropriate records to ensure compliance with approved permit conditions and requirements of the Salt Institute Voluntary Salt Storage Guidelines for Distribution Stockpiles.
c. A written Pollution Prevention Plan, where required, must be prepared and implemented for each facility.
Training Program
The Institute makes available a training program for salt distribution facility personnel. These materials are available for free downloading. The PowerPoint presentation contains "speaker's notes" which are a script for trainers or the script can be downloaded separately.
Trainer's script (msword 78.00 kB)
PowerPoint presentation (vnd.ms-powerpoint 2.48 MB)
Note: Compass Minerals/North American Salt has an easy-to-use "stockpile calculator ."