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Extras din - Impact Assessment of Natural Gas Production in the New York City Water Supply Watershed
- Final Impact Assessment Report, 2009 realizat de Departamentul de Protectia Mediului New York.
Sper ca d-l primar din Tg Bujor stie un pic de engleza. Raportul are 100 de pagini si daca dl primar si dl Kolbay doresc sa-l rasfoiasca il pot gasi pe internet in format pdf.

4.5 Surface (pagina 36 din studiul de impact)
Spills Accidental spills, leaks, and releases associated with natural gas well drilling and fracturing activities have resulted in hundreds of documented groundwater and surface water contamination incidents across the country. Surface spills can be a relatively common occurrence at well sites because the drilling and fracturing process involves transfer of large volumes of fluids between trucks, tanks, wells, pits, etc., often at high flow rates and pressures, substantially increasing the likelihood of a spill due to human error, equipment failure, or accident. Surface spills in the NYC watershed may be categorized as resulting in either acute or chronic impacts based on proximity to streams and reservoirs. Acute spills are considered here to include accidental or intentional chemical releases that occur adjacent to or in a stream or reservoir. Chronic spills are considered to occur at the well site or beyond the immediate vicinity of a stream or reservoir.

Related Precedent (pagina 45 din studiu de impact)
The migration of fracking chemicals and/or poor quality formation water into overlying groundwater, watershed streams, reservoirs, and directly into tunnels is a reasonably foreseeable risk. The failures postulated above are not theoretical: they have occurred, at least with respect to impacts on streams and groundwater.
A well-documented case occurred in Garfield County, Colorado in 2004 where natural gas was observed bubbling into the stream bed of West Divide Creek. In addition to natural gas, water sample analyses indicated ground water concentrations of benzene exceeded 200 micrograms per liter and surface water concentrations of benzene
exceeded 90 micrograms per liter – 90 times the NYSDEC Part 703 water quality limit for discharge of benzene to surface waters. Operator errors, in conjunction with the existence of a network of faults and fractures, led to significant quantities of formation fluids migrating vertically nearly 4,000 feet and horizontally over 2,000 feet, surfacing as a seep in West Divide Creek. It should be noted that the vertical separation between the Marcellus Shale and the West Delaware Tunnel ranges between 3000 and 5500 feet, well within the vertical distance seen in this incident in Garfield County, Colorado. Clearly there is a very real potential for methane migration from the Marcellus shale to the City water supply tunnels. Although remedial casings installed in the well reportedly reduced seepage, the resulting benzene plume has required remediation since 2004. Subsequent hydrogeologic studies have found that ambient groundwater concentrations of methane and other contaminants increased regionally as gas drilling activity progressed, and attributed the increase to inadequate casing or grouting in gas wells and naturally occurring fractures. Groundwater contamination from drilling in the Marcellus shale formation was reported in early 2009 in Dimock, PA, where methane migrated thousands of feet from the production formation, contaminating the fresh-water aquifer and resulting in at least one explosion at the surface. Migrating methane gas has reportedly affected over a dozen water supply wells within a nine square
mile area. The explosion was due to methane collecting in a water well vault. Pennsylvania Department of Environmental Protection has since required additional ventilation, installed gas detectors and taken water wells with high methane levels offline at impacted homes to reduce explosion hazards. At this time the root cause remains under investigation and a definitive subsurface pathway is not known. This case is of particular concern since the terrain and geology in Pennsylvania is very similar to that of the NYC watershed: Dimock is only 35 miles from Deposit, NY and the Cannonsville Reservoir Dam.