I have many serious concerns about high volume horizontal hydrofracturing in tight shale formations. This article will focus on the cumulative effects of this process on drinking water and specifically on the repeated fracturing of each well over its productive life. Although there has been considerable experience with hydrofracturing in conventional oil and gas fields for many years, the process currently used in tight shale formations is relatively new and very different. Hydrofracturing in conventional fields, if carried out, is generally performed either upon initial completion of a well or as a means of secondary recovery late in the life of the well. In tight shale formations, the process is usually carried out at relatively higher pressures in dense shales of low porosity. This should be done upon initial well completion and then repeated several times over the life of the well due to rapid decline rates. Experience with this type of large-scale tight shale hydrofracturing is only about ten years old, so only a few of these wells have been fractured more than once. However, all of these wells will need to be fractured numerous times at increasingly shorter intervals due to rapid decline rates. At this time, we simply do not know how many times the process will be attempted or what the cumulative effect of this repeated hydrofracturing will be. (This is one of the shortcomings of the EPA study that you asked speakers to identify during the hearings in Binghamton, New York.) Each successive hydrofracturing of a well will extend the fracture zone further of the horizontal wellbore. In areas like New York and Pennsylvania, where there are many natural cracks, each successive use of the process increases...... middle of paper ...... proven facilities before each hydrofracturing procedure begins . Require periodic subsidence checks above each wellbore and cessation of further hydrofracturing if subsidence is detected. It should be understood that the above is not exhaustive and additional precautions should be taken into account. However, none of these precautions, individually or in combination, will entirely eliminate the risks associated with this process. Additionally, it should be noted that this article is limited to the impact of the process on drinking water. A similar assessment should be made on the cumulative risk of air pollution from the process. In summary, it is essential that EPA, in its studies, consider that hydrofracturing will occur repeatedly in each well and ensure that the true cumulative risks of this activity are properly addressed.