Analysis of health and environmental risks associated with Marcellus Shale development
The rapid growth of the shale gas industry has inspired questions concerning attendant apparent and potential short- and long-term health and environmental risks. My research examined three potential environmental and health risks.
(1) For the last half-century the Northeast natural gas market was supplied from major producing areas in Texas, the Gulf Coast, and Canada. Because radon has a short half-life of 3.8 days, the time required to transport the natural gas from these areas to the Northeast resulted in a low-radon product being delivered to homes. As the Northeast gas market transitions to locally-produced natural gas the potential for radioactive decay will diminish and the natural gas being delivered to homes will contain radon at higher levels. I assess the lung cancer risk for people living in homes with unvented gas cooking (approximately half of the homes in the Northeast) and heating appliances, which are in fewer homes. Data on the locally-produced natural gas radon concentration are limited, but for the modeling assumptions considered the radon exposure is predicted to be small compared to typical residential exposures, and additional annual population-level risk will likely be much less than the error in the estimate of annual radon-induced lung cancers. An excess lifetime lung cancer risk >10-4 is possible for high gas usage in poorly ventilated settings.
(2) High volume and locally-concentrated surface water withdrawals for Marcellus Shale development may pose a risk to water quality, aquatic and riparian ecosystems, and other uses of water resources. State environmental and interstate water authorities take different approaches to managing these water withdrawals. In the Upper Ohio River Basin, which covers the western third of Pennsylvania, the Department of Environmental Protection requires that all water used for shale gas development be covered by a water management plan. These plans stipulate the amount and timing of surface water withdrawals from each source as a function of annual stream flow statistics. Neighboring regulatory authorities and some environmental groups favor the use of monthly flow statistics instead, but implementation of these statistics in western Pennsylvania would require more data than are currently available. Because hydrologic data in the Upper Ohio River Basin are sparse, the use of the annual flow statistics is more likely than use of monthly flow statistics to prevent water withdrawals when aquatic ecosystems are under the greatest stress. The annual flow statistic might also result in fewer and smaller occurrences of computed ecodeficits under scenarios of development-related water demands in the future.
(3) Improperly abandoned and orphan gas wells threaten human health and safety as well as pollute the air and water. Pennsylvania currently requires production companies to post a bond to ensure environmental reclamation of non-productive well sites, but the cost of plugging horizontally drilled wells and reclaiming well pads is estimated to be at least a factor of 10 greater than the current well bonds. The economics of shale gas development favor transfer of assets from large entities to smaller ones. With the assets go the liabilities, and without a mechanism to prevent the new owners from assuming reclamation liabilities beyond their means, the economics favor default on well-plugging and site restoration obligations. In addition to increasing the bond amounts, individual well trust accounts are proposed based on a model from the coal industry. Pre- and delayed-funding options (a fee and severance tax, respectively) to pay for future reclamation are examined from the perspective of the taxpayer. The exposure of the taxpayer to these financial liabilities and to a future orphan well problem can be minimized with minimal impacts to the profitability of gas production regardless of which funding option is used.