According to the Camden County Road & Bridge administrator, the dust suppression solutions sprayed on a few county roads in western Camden County this summer were safe for application on roadways.
Area resident Laura Ethington Simpson expressed concern about the spraying near the Lake of the Ozarks and possible impacts to water quality. A private company sprayed the roads after being hired by some residents within Lazy Acres subdivision.
County R&B Administrator and Engineer Lee Schuman, PE, has now received Material Safety Data Sheets from the company, MLCR, for all products used in Lazy Acres and said the chloride solutions are safe. The county allows calcium or magnesium chloride solutions to be applied to roadways with private funding, but the company must be permitted and inspected, according to Schuman. The contractor had not done that prior to last summer’s work, but after being made aware of the requirements, they now appear to be working with the county to be in compliance.
According to Simpson, the company sprayed several times over the summer at different areas in the lakefront neighborhood of Lazy Acres, located in the vicinity of State Route FF in the Edwards area. Simpson said the liquid smelled “HORRID,” and was worried about rain washing it into the Lake of the Ozarks.
According to Schuman, previous road administrators did not require the contractor to acquire a permit, but Schuman felt the work should be documented.
Magnesium chloride and calcium chloride are salt solutions, commonly used for many years to control dust, according to a Missouri Department of Natural Resources Air Pollution Control Program fact sheet.
The DNR information states that salts, “have the side benefit of stabilizing the road surface resulting in reduced loss of gravel from the road surface and lower maintenance requirements. The two most common salts are calcium chloride and magnesium chloride.”
It adds, however, that these salts are harmful to many plants and some animal life without careful application to avoid contaminating the environment, citing application rates for calcium chloride from 0.2 to 1 gallon per square yard of road surface and from 0.25 to 0.5 gallon per square yard for magnesium chloride.
The DNR fact sheet explains that both salts work by absorbing moisture from the air, which wets the small particles in the gravel and keeps them out of the air.
“Heavy rains may leach the salt from the road resulting in loss of dust control when the road dries. Certain salt-treated surfaces may become slick during heavy rains. Salt is also corrosive to steel, but this is not a problem with normal application rates. During dry spells, magnesium chloride retains dust control better than calcium chloride because of a higher affinity for moisture.”
Calcium and magnesium chlorides may need to be reapplied once or twice a season, depending on the traffic and the amount of rainfall, according to DNR.
To select the optimum treatment, a soil analysis should be conducted to classify the road material. Some treatments are better suited to certain types of road material (i.e. clay content or amount of fines). Before undertaking a chemical dust suppression treatment, the road surface must be in proper shape, with particular attention paid to crowning the road for good drainage. In the case of lignin, this would be done when the chemical is applied.
At least one of the solutions used in Lazy Acres is believed to have contained lignin which is extracted from wood pulp and is considered another environmentally sustainable dust suppression agent for roads.
DNR’s Water Protection Program does not require a permit for application of road dust suppression chemicals if the following conditions are met:
•They are not applied within 300 feet of waters that have been identified as:
•A losing stream or water bodies listed in the Missouri Water Quality Standards (10CSR 20) as an outstanding national or state resource water.
•A lake or reservoir used for public drinking water supplies.
•Critical habitat for endangered species.
•A biocriteria reference stream.
•They are not applied within 100 feet of waters classified as L2 (major reservoir) or P (permanent flow) except for the Missouri and Mississippi rivers.
•They are not applied to a sinkhole or other direct conduit to ground water.
•They are not applied in such a manner that the department receives a complaint, and upon investigation, finds that the dust suppressant is causing a violation of general water quality criteria.
If a stream or lake is located near the site, MDNR recommends contacting its Water Protection Program to find out if applying chemicals should be avoided or if any other conditions may apply.