In early January, a storm named “Hercules” hit Plymouth County, bringing with it heavy snowfall, high winds, frigid temperatures, and coastal flooding. It was a moderate nor’easter by New England standards. However, what was different about Hercules was that three astronomical high tides occurred at the same time as the storm – what could be considered a fairly rare meteorological and oceanographic event.
As Hercules made its way toward Plymouth, we reached out to the NRC and suggested that the storm event could be a valuable opportunity for Entergy and/or NRC on-site inspectors to better assess flooding potential at Pilgrim. We are particularly concerned about flooding on the site now that Entergy is constructing a dry cask nuclear waste storage facility within a few hundred feet from the shore of Cape Cod Bay. We asked the NRC to collect observational notes and photo-document storm conditions at the Pilgrim site. Read our Dec. 30th blog about the storm and our letter to the NRC →
The NRC responded to our request on January 27th, and provided some useful information about flooding conditions during Hercules. Read the NRC’s full letter →
According to the NRC, “…resident inspectors and regional staff monitor approaching storms and assess plant impacts both during and after storm passage.” Prior to the storm, the NRC’s resident inspectors performed an “Adverse Weather” procedure, where they essentially walk the site and look for potential problems. They make sure cold weather protection features (e.g., space heaters, weatherized enclosures) are functioning properly.
During the storm, the NRC reports that the highest observed tide level (with waves) did not approach “design basis” conditions. An “unusual event” (or an event that would trigger an emergency level) is not reported until the water level reaches 13.5 ft above mean sea level (MSL). The water measurements are apparently taken in the circulating water intake bay. The highest water levels measured in the intake bay during the storm occurred with the Friday afternoon high tide (on Jan. 3rd), and were consistent with what was forecasted – 7-8 ft above MSL. However, due to the wave action on the site, some peaks occurred of up to 11.7 ft above MSL. The NRC reported that there were no impacts to equipment in the intake water bay, and no damage to the jetties occurred during Hercules.
Our challenge concerning the characterization of Pilgrim as a “dry site” was also addressed. The NRC stated that since the plant is built above maximum storm level, it falls within the definition of a dry site as defined by NRC. However, even if Pilgrim technically fits the NRC’s definition of a “dry site,” it is still concerning that a plant only a few feet outside the definition and not far from the shoreline can be characterized as “dry,” especially when another federal agency FEMA, has a 17 foot velocity flood zone established for the site–meaning a flood of some level with waves on top.
While we appreciate the NRC’s response and feel that we learned something from what they provided, we are still uneasy about the flooding potential at the site, most especially due to the lack of clarity about the datum that are used. A previous report, in reference to the circulating water intake bay that was also used for this storm, declared that “the vertical datum for this station is unknown” (April 2010 ERM Report). Seeing that the emergency level is 13.5 ft above MSL and tide levels peaked at 11.7 ft above MSL during this relatively moderate nor’easter, we feel that storm surges during a more intense storm has real potential to cause problems at the plant and the dry cask storage facility.
Climate change – and resulting sea level rise, now predicted at a six foot rise within the next century, and increasingly intense storms with extreme wind and wave velocity – is a very real problem facing our shoreline. As sea level in the Bay increases, the margin between “dry site” and emergency level will only continue to narrow at the Pilgrim site.
In the response letter, the NRC stated that Pilgrim will be required to reevaluate site specific flooding hazards and submit a report to the NRC before March 2015. We need to be engaged on this issue. Stay tuned! As we learn more, we will pass it on.
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