TRANSMITTAL LETTER FOR BOARD MEETING OF DECEMBER 18, 2008
COMMITTEE ON MAINTENANCE AND OPERATIONS
Mr. Richard Lanyon, General Superintendent
Title
Report on the Use of De-Icing Salt and Water Quality Impacts
Body
Dear Sir:
The salting of roadways for the purpose of de-icing may result in sodium chloride migrating into adjacent soil and surface waters by means of water runoff and salt scatter. Sodium chloride has been identified to be the cause of a decrease in dissolved oxygen levels, an increase in acidity levels, an increase in conductivity, and a reduction in aquatic life diversity in adjacent surface waters. Measurable amounts of sodium chloride have also been detected in soil samples taken 200 feet from roadways. The source can be traced to the salting of roadways using applied concentration mixtures as low as 1/3 teaspoon of sodium chloride per 5 gallons of water. Even at this low concentration, damage to existing plant life occurs which may allow invasive salt tolerant species to thrive.
These adverse impacts of salt on the environment are confirmed by the total maximum daily loads (TMDLs) for Salt Creek and the West Branch of the DuPage River and the potential for stricter effluent limits for our two water reclamation plants (WRPs). Therefore, we are extending this concern to all WRPs because of our mission to protect the water environment.
Since our last report for the Board Meeting of May 17, 2007 regarding road salt and water quality, the WRPs have been installing proper storage facilities, limiting the rate of salt dispersion through ground speed dispensing controls, and developing a de-icing pilot program.
As of this date, the Stickney WRP has a proper storage facility for road salt. The Stickney WRP stores their salt in a salt dome. The Kirie WRP stores their salt on an impermeable concrete slab in a covered storage bin enclosed on three sides by concrete walls. Similarly, the North Side WRP stores their salt in a covered concrete storage bin enclosed by three walls. During the time that salt is not in use, the exposed sides of the Kirie and North Side WRP’s salt storage bin is covered with a tarp to prevent rain from percolating into the salt pile. The Calumet WRP has budgeted $110,000 for the installation of a salt dome in 2009. The Egan WRP has a contract (No. 08-777-11) in place for the installation of a bulk storage building. The total contract value for this facility is $214,506. Only one of the four bays of the storage building will be used for road salt. It is anticipated that the completion of construction will be in the spring of 2009.
At the Hanover Park WRP, a contractor plows and salts the roads. There is no bulk storage building at this plant because salt that is needed for the sidewalks is purchased in 50-pound bags, stored in the Hanover Park WRP’s storeroom and spread by Hanover Park staff. At the Lemont WRP, bagged salt for sidewalks is stored at the Calumet WRP’s storeroom, delivered to the Lemont WRP, and spread by Calumet staff as needed. Salt used for the roads is transported to the Lemont WRP by the truck that is used to plow and salt the roads. There is no need to store salt at the Lemont WRP.
Last winter, the Stickney WRP retrofitted two salt trucks with ground speed controls. In addition, they purchased a third truck that came with ground speed controls. The truck also has the capability of pre-wetting the salt before application. Kirie WRP’s salt truck is equipped with ground speed dispensing controls, and the Calumet WRP will purchase a salt truck with ground speed dispensing controls in 2009.
The May 17, 2007 Board Report stated that a pilot de-icing program would be implemented at the Egan WRP, however, it was later decided to establish the program at the North Side WRP. Although specific details of the pilot program are still being developed, the North Side WRP achieved a 33% reduction in salt usage this past winter due to the installation of ground speed controls and the use of pre-wetting spray units. The cost to install the additional equipment on the existing salt truck was $9,600. In addition, the North Side WRP experimented with the use of two pre-wetting agents to the salt prior to application: “Geo Melt,” a trade name for a pre-wetting agent including beet juice, and “Super Mix,” a pre-wetting agent including a mixture of beet juice, calcium chloride and brine. They have determined that “Super Mix” worked better than “Geo Melt.” This was corroborated by the City of Chicago and other surrounding municipalities that have had success using this pre-wetting agent. Findings, such as the above, will be incorporated into the de-icing pilot program.
Large consumers of road salt, such as municipalities, are given priority for delivery over those customers, including the District, that do not purchase a large quantity. In the past, salt deliveries were not made in a timely manner, thus delaying the application of salt to District roads and sidewalks, jeopardizing the safety of District staff and causing for use of larger quantities of salt. As seen above, this also forces the District to construct salt domes at the WRPs.
Due to the projected rising costs of road salt and diesel fuel and the unreliability of salt deliveries, the installation of additional ice control equipment and the use of alternative de-icing products may become more cost effective. Furthermore, the potential for reducing runoff pollution (sodium chloride) makes the above equipment and products a sensible choice in the District’s efforts to protect our water environment.
Respectfully Submitted, Osoth Jamjun, Chief of Maintenance & Operations, OJ:MPS:SO’C:AG:BML