Friday, February 06, 2015

NIBW Update: another likely carcinogen in Scottsdale's drinking water

This is going to be a Scottsdale-focused non-political post, but since I live in the North Indian Bend Wash Superfund (NIBW) site, it kind of grabbed my attention.  So I'm exercising a little blogger's privilege here... :)

Earlier today, the EPA's Community Involvement Coordinator for the NIBW sent out an email to the members of the Community Involvement Group of the NIBW. 

From that email (their emphasis) -

We are issuing this update as part of EPA’s regular practice to keep the community informed of EPA’s ongoing oversight of the North Indian Bend Wash (NIBW) Superfund Site remedy.  This update addresses the recent finding of low levels of 1,4-dioxane in groundwater within the NIBW Superfund site.  Although 1,4-dioxane is detected in groundwater, tap water remains safe to drink.


The City’s data indicates 1,4-dioxane was detected within the North Indian Bend Wash Superfund site.  In all previous sampling, 1,4-dioxane had not been detected or was detected below health-based screening levels in effect at the time of sampling. 

At the NIBW site, air stripping and liquid phase granular activated carbon treatment are used to treat trichloroethylene (TCE) and tetrachloroethylene (PCE), which are the NIBW primary chemicals of concern.  These systems do not effectively remove 1,4-dioxane.

Because health-based screening levels have changed and the treatment systems in place at NIBW are not effective at removing 1,4-dioxane, EPA asked the City to remove one well from its groundwater pumping system while EPA, ADEQ, the City, and NIBW Participating Companies evaluate the data. 
As noted above, at EPA’s request the City of Scottsdale has stopped extracting water from well 75A, pending further investigation.  At this time, the suspension of pumping from this well can be sustained without jeopardizing the continuing success of the NIBW Site remedy.

In addition to the samples collected in January 2015, groundwater samples will be collected throughout the NIBW Superfund site to determine if 1,4-dioxane is detected other than in the area of well 75A, and, if so, at what depths and concentrations.

When the additional sample results are available, EPA toxicologists will review all of the data and provide recommendations for appropriate next steps.
EPA will provide updates to the CIG as new NIBW information and data are available.  In the meantime, please feel free to contact us if there are questions.

Background on 1,4-dioxane - 

EPA information here.

Agency for Toxic Substances and Disease Registry (part of the US Department of Health and Human Services) info here.

FDA info here.

California State Water Resources Control Board info here.

Summary:  It's toxic, and it may cause cancer.  While the assurances regarding the level of dioxane contamination seem genuine, the fact that current remediation efforts in the NIBW are ineffective in regard to it is worrisome.  This is a situation worth keeping an eye on.

Background on the NIBW -

The history of the site began with the discovery of groundwater and soil contamination in 1981, mostly of VOCs (Volatile Organic Compounds) attributed to the disposal of industrial waste. 

The entire site covers approximately 13 square miles of Tempe and South Scottsdale, with Pima/Price Road serving as the eastern border, Scottsdale/Rural Road as the western border, Apache Boulevard as the southern border, and Chaparral Road as the northern border.  The NIBW/SIBW split occurs at the Salt River, north of Rio Salado Parkway in Tempe.

EPA's North Indian Bend Wash Superfund (NIBW) site info page

City of Scottsdale's NIBW page

A National Academies of Science report on the human health risks of TCE here (there are a *lot* of reports on this; just type "TCE" into any search engine)

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