Preliminary Study Does Not Find Heavy Metal Pollution in Nosara River Water

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In May of 2015, The Voice of Guanacaste took a sample of the Chinese produced cement used in the Nosara dike, Sinocem, and sent it to Lambda, the accredited chemical laboratory, to find out if the amount of heavy metals contained in the cement is normal.

The results show that the levels of arsenic, cadmium, lead, chromium and mercury are normal, and below the levels permitted in Costa Rica for use in hydraulic dams.

This means that the cement imported from China meets national and international requirements. The dike in Nosara was the first to use this imported product.

The Voice decided to take samples of the cement used to build the last phase of the dike due to the concern expressed by several Nosara residents about the “questionable” cement quality and its possible effect on the environment and human health.

Also, a study that was done on February 16th by the Federated College of Engineers and Architects, in which they indicate that there are flaws in the dike such as loosening materials and cement blocks falling onto the riverbank. However, the National Emergency Commission,  institution that financed the $2 million project, classified the CFIA report as being “not very serious and subjective” and stated that the dike has not lost its usefulness.

Tests Do Not Show Contamination of Drinking Water

Bags of Sinocem cement spread along the Nosara river with left over cement inside.

Although the cement quality results showed normal levels of heavy metals, the cement itself is not the only thing that determines the quality of the dike.

According to chemical engineer Rafael Amon from Lambda laboratory, the element that determines the strength and quality of the dike is the mortar mixture used to bind the cement.

If the mortar was not made well, the dike could release a greater amount of cement into the river, and if it does not dissolve naturally, this could possibly affect the environment.

“Two drops of gasoline falling into a sewer is not the same as spilling a jar-full,” Amon illustrated.

This newspaper took two water samples: one from the mouth of the Nosara River and one from a handmade well in the community of Santa Marta. The results were negative for contamination, although a single test is insufficient to assert this finding broadly and definitively.

The samples were taken during October of 2015, the month in which the Nosara River has a higher flow rate. It is important to clarify that the rains last year were 40% less than normal, as reported by the National Meteorological Institute.

The handmade well chosen for taking the sample is in the community of Santa Marta. It is 10 meters deep and has been used for more than 20 years by a local family that lives next to the Nosara River. Before taking the sample, the water was left running for 5 minutes.

The Voice asked UCR’s Environmental Pollution Research Center to analyze the amount of heavy metals in the water.

The results of both samples—the ones from the mouth of the river and from the well— show that heavy metals such as arsenic, cadmium, lead and chromium are below the maximum values permitted. Therefore, there was no risk of contamination at that time.

Biologist Victor Arias Mora specified that to ensure there is no contamination that would have  negative effects on the environment and the people who consume this water, two more studies should be done, one when the river flow is almost dry and another when it is at its maximum.

Arias explained that, among several factors, the amount of heavy metals dissolving in the water would depend on the flow rate of the river—the amount of water present— and the strength of its current. When the river has more water and a stronger current, and therefore a lower presence of metals, there is less possibility of contamination.

The Voice of Guanacaste will be conducting more follow-up studies.