Public radiation dose from conventional gas-well produced water used as a pavement Deicer

Conventional oil and gas wells produce wastewater, or brine, that has a beneficial use as a road deicer. However, the brine also contains naturally occurring radium (Ra-226 and Ra-228). This work modeled radiation doses to an adult and a 15-year old receptor (the highest dose age group) from two scenarios. Scenario 1 considers exposures during recreational activities from deicer runoff to roadside soils following repeated deicer applications. Scenario 2 assumes that a residence with farming is built on soil having the same radiation content as the roadside soils in Scenario 1. Maximum detected Ra-226 and Ra-228 levels in brine samples taken from six conventional gas wells located in northern Ohio were used, along with conservative assumptions, to model annual whole-body doses. Accounting for Ra-226 and Ra-228 decay and assuming limited radium buildup in roadside soil, as supported by experimental and empirical evidence, modeled doses for an adult and 15-year old were predicted to reach an asymptote at approximately year 50 of 0.0077 and 0.012 millisieverts per year (mSv/yr), respectively, in Scenario 1 and 0.025 and 0.040 mSv/yr in Scenario 2. Assuming no limit on buildup and the northern Ohio average 30 brine applications per season, accumulated doses were predicted as 0.0010 mSv/yr for an adult and 0.0087 mSv/yr for a 15-year old, respectively, in Scenario 1 at year 50 and 0.19 and 0.30 mSv/yr in Scenario 2. These dose estimates are within the U.S. EPA and NRC standards of 0.25 to 1 mSv/yr for protecting the general public and well below the natural background dose. This analysis predicts that use of conventional gas-well brine as a road deicer is unlikely to pose an unacceptable radiation risk to the public. The analysis is sensitive to the level of radiation buildup in soils; more field studies on radium transport processes are warranted.