Reducing Brine Runoff from Salt Storage Facilities

Written by Dwain Thomas

During a recent investigation of brine runoff from road salt storage facilities, it was concluded that in situations where brine is contaminating groundwater, the problems could be alleviated with changes to the operational procedures used for handling the salt. Eliminating snow and rain contact with salt at the site would not only prevent most cases of aquifer contamination, but likely would actually begin to clean up the groundwater near these sites.

The method, commonly called the "do nothing" approach, is more accurately termed "in-situ cleanup", and is becoming increasingly more common with the shrinking budgets encountered today by most municipalities, public works departments, and other public agencies. This type of cleanup is especially fitting considering the U.S. Environmental Protection Agency (EPA) does not regulate salt, nor include it in the National Pollutant Discharge Elimination System (NPDES) classifications. Use of valuable funds is therefore more appropriately reserved for more pernicious chemical contaminants.

Better management of salt reduces contact with all types of precipitation since the salt is immediately cleaned up and returned to the pile. This, in turn, reduces brine runoff, brine concentration, and the resulting contamination to nearby groundwater.

Brine runoff is dramatically reduced if:

• All roof runoff is captured via gutter and pipe, and the outlet is located away from the operations pad

• Roofs over salt piles are in good repair

• Any weep holes in the building walls are plugged

• The door frame is blocked at the bottom so that any moisture is trapped inside the building, rather than draining out (try polymer-composite lumber cut to fit)

• Any cracks and potholes in the operations pad are fixed as though they were highway patches, and the entire asphalt pad inside and outside the building is sealed

Salt that is delivered in the off season should be received dry. If possible, deliver the material directly into the storage building. Ten-inch-diameter grain augers cost less than $7000, and may last three years. Then they can be discarded. This is a much less expensive approach than installing special conveyors.

If the "dump and push" method of loading the building is used, the pad should then be thoroughly swept and vacuumed, with the collected solids being thrown on the salt pile. Several companies make inexpensive walk-behind vacuum sweepers, and some can be obtained with corrosion-resistant hoppers. Do not unload salt if it is windy, or rain is falling. Never wash the pad at any time since it simply forces brine run-off..

The scattered salt from outbound distribution loading miscues must be scraped back into the salt building between vehicle loading. Sweeping is even better. This will prevent snowfall from contacting it and, later, taking it away from the pad as run-off.

Where sites are already configured to capture brine, the captured brine can be pumped inexpensively into double-wall plastic tanks from the capture sump. After being brought to full strength, the brine should be routed to pre-wet outbound salt loads. The solids that settle out in the beginning of the brine recapture process should be returned to the salt pile, minus large rocks. The pump should be corrosion-resistant. Bringing brine to full strength can be accomplished with salt and stock tanks, or with prefabricated brine equipment.

Where the site is configured so that the brine is not collected, the snow that comes into contact with the pad during salting operations should be scooped up and added to outbound loads. Experience will tell approximately how many buckets of snow should be added to each load of salt.

Salt distribution trucks should be manually cleaned after the last load. This should be performed over the pad, and all solids returned to the building. The most cost-effective method of cleaning is to reduce the solids as much as possible, then take the vehicles to a commercial truck wash if one is close enough. If that is not the case, the vehicles may be washed at a maintenance facility that does not store salt. This lightens the brine load from the other facility. The relative strength of the brine from the washing operation is less, and the solution will either enter a wastewater collection system, or be very diluted, and intermittent.

Store the distribution boxes on a pad, preferably one that routes precipitation to the collection system. If the boxes are stored under cover, this is not necessary, so long as the boxes are not washed or rinsed on the rack.

After the final truck is cleaned, sweep and vacuum the pad free of any remaining salt resting on the rough pavement surface. None of this material must leave the pad, except on a salt truck load. After the final load of a salt distribution operation, the pad must be thoroughly swept, and all solids and slush thrown on the salt pile in the building. It may be swept again after it dries, but never washed or rinsed.

The most inexpensive option for brine mitigation might appear to be disposal through connection to a sanitary sewer system. This option, however, has the other consideration that it would still be necessary to incur additional construction costs for the pad and curbs, which would be needed to collect, settle, and route the brine. Sanitary disposal of brine just moves the salt eventually into a river or stream to contaminate aquifers downstream, since the treatment plant's biological processes do not remove the salt from the waste stream. The brine in the influent is passed through the system and discharged in the effluent at full weight (pounds of salt in equals pounds of salt out). Discussions with wastewater treatment plant operators have revealed that many are reluctant to accept brine due to the presence of salt and cyanide (from the anti-caking agent).

Finally, do not give mere lip service to a salt cleanup policy. The supervisor, superintendent, and/ or manager must make visits to the sites, even when there are difficult situations elsewhere. Testing of the pad, the runoff, or nearby wells will reveal if the policy change is effective, and if more severe and costly modifications will be necessary. A simple routine is to watch the surrounding drainage channels for discoloration and residue.

About the Author: Dwain Thomas, P.E., is with Blackburn Architects in Indianapolis. For more information contact him at: 3500 DePauw Boulevard, Suite 1090, Indianapolis, IN 46268: Tel. 317-875-5500; Fax. 317-875-0544.