Increased Arsenic in Drinking Water – A Pipeline Risk

    from Director of Science & Stewardship, Steve Tuorto, PhD.

Most of the PennEast pipeline’s proposed route through New Jersey will interact with Fractured Bedrock Aquifers that feed the region’s private and community drinking water wells[1]. These aquifer rock formations have naturally occurring arsenic in them, all interact with other arsenic-bearing bedrock layers of varying depths and to varying degrees, and have varying thicknesses of soil layers overlying them (see schematic of pipeline trench below).

Arsenic exists at a wide range of concentrations from rock formation to rock formation. The highest concentrations measured in New Jersey exist in the water-bearing rock formations (black & gray shales) that run through Hunterdon and Mercer counties[2]. The majority of the arsenic is trapped in a harmless form, abbreviated as “As+V”, within the rocks. However, under certain chemical conditions arsenic is converted into its soluble toxic form, “As+III”, and is likely to end up in your drinking water[2,3].

The National Ground Water Association recommends that private well owners test their drinking water annually for at least bacteria, nitrates, and any other contaminants that are known to be of concern for your area.

The arsenic is trapped in the ground by either being part of a rock compound (such as pyrite), or by binding to other materials such as iron or aluminum metals in the presence of oxygen, or to sulfides in the absence of oxygen. There are several main conditions that can increase the amount of As+V in the bedrock that turns into As+III.

Events that increase toxic arsenic release:

Removal of Oxygen – If all of the oxygen is removed from a system that once had oxygen (changing it to what we call “reducing” conditions), As+V is more readily changed into As+III, and any As+III that is attached to iron and aluminum compounds will be released.

High pH – If the pH of an environment becomes more basic (or less acidic), for example higher than 8-8.5, As+III gets released from rocks and binding sites.

Growth of Arsenic-Releasing Bacteria – Certain types of bacteria that grow in the absence of oxygen, but in the presence of organic matter under reducing conditions speed up the conversion of As+V to As+III, and other types use up the iron compounds, releasing the As+III that is bound to them. This is all done as part of their natural metabolism.

Addition of Oxygen – If oxygen is suddenly made available to a system that did not have oxygen before, (changing it to what we call “oxidizing” conditions), any of the As+III bound to sulfides will be released.

Installation of the pipeline will involve excavating the soils, blasting through the bedrock and fractured rock aquifer, and backfilling the mixed layers around the laid pipe. As shown in the schematic of the pipeline trench bed after installation, during wet periods (such as spring), runoff water will infiltrate the backfilled trench at much higher rates than undisturbed soils and solid bedrock. This runoff will flush sediment, organic matter and any pollutants that occur in your area to mix with the blasted arsenic-bearing rock fragments at the bottom of the trench. Air breathing bacteria will begin to grow and will utilize all of the oxygen up very rapidly. This results in the reduced condition that creates more As+III and releases existing As+III from iron-like metal materials. This is also the condition that will cause the As+III releasing bacteria to grow.

Schematic of a pipeline trench excavated/blasted through overlying soil & rock formations.  

In addition, the “cathodic shield” (shown as a red circle in the image) is an electrically conductive coating placed around the surface of the pipeline to prevent corrosion.  The shield not only produces heat which can speed up both the chemical and bacterial reactions discussed above, but can also significantly increase the pH of the soils around the trench to range from 9-13 (very basic) [4]. The cumulative effects of all of these processes is a bio-chemical soup in the trench bed around the pipeline, that has the potential to increase the amount of toxic arsenic that can leach into the fractured rock aquifers at many times its natural levels.

During dry periods, these processes will slow and arsenic will become concentrated on the binding sites associated with the iron-like materials. Once there is a wet period, runoff water will once again refill the trench bed with oxygen and water, flushing the accumulated arsenic into the surrounding groundwater, and starting the process all over again. To make matters worse, the blasting necessary to create the trench is likely to increase the flow of water from the trench into the aquifer, change the flow regimes in unpredictable ways, and change the composition of constituents in the water other than arsenic [5].  Examples of these are any other contaminant of concern in your area, such as radon or boron, but also include more typical salt or nutrient contaminants such as nitrogen, chlorine, and bromine compounds.

The proposed pipeline route is along highly variable topography, and the depth and combination of soil and rock formations vary as well. The processes described are highly complex, and made more complicated by large variations in the regions hydrology. There are many studies showing that human disturbances to soils and sediments increase leaching of arsenic into water in this type of environment [6,7], but the fact is that no relevant studies have been done to gauge to what extent this area would be impacted by a pipeline construction. PennEast is not doing the required environmental impact studies, but claims that such events are possible and that they will deal with them (and the many other damages to the environment) as they occur.

You will not know whether or not your drinking water contains arsenic in it until you are already drinking it, and will need to test your water frequently to know if the levels change.


  1. RE:Draft Environmental Impact Statement (DEIS) for the Proposed PennEast Pipeline Project (Pennsylvania, New Jersey) (FERC Docket No. CP15-558-000). Lindy Nelson, Regional Environmental Officer – USGS. Sep. 20, 2016. (
  2. Arsenic in New Jersey’s Groundwater. Prepared by Michael Serfes. NJ Geological Survey Circular. 2004. (
  3. How Does Arsenic Get Into the Groundwater. University of Maine – Geology Dep. (
  4. Coatings used in conjunction with cathodic protection – Shielding vs non-shielding pipeline coatings. Norsworthy, R. No. 4017. In 17th International Corrosion Congress, NACE International. 2009. (
  5. Impact of blasting on groundwater composition in a fracture in Canada’s underground research laboratory. Gascoyne, M. & Thomas, D.A. J. of Geophysical Research: Solid Earth. V 102. 1997. (
  6. Contributions of arsenic from bed sediments to water in the Wallkill River, Northwestern New Jersey. Barringer JL, Haussmann N, Sutley SJ, Sanzolone RF, Garbarino JR, Johnson AH, et al. Geol Soc Am annual meeting and exposition Philadelphia PA 22–25 October 2006.
  7. Biogeochemical environments of streambed-sediment pore waters with and without arsenic enrichment in a sedimentary rock terrain, New Jersey Piedmont. Mumford AC, Barringer JL, Reilly PA, Eberl DD, Blum AE, Young LY. ci Total Environ (2014),

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Steve Tuorto is the Director of Science and Stewardship at the Stony Brook-Millstone Watershed Association.  Steve has been studying geochemistry, environmental science, ecology, and oceanography for over 17 years.