Vermont Health Department monitors newly contaminated wells at Vermont Yankee

first_imgIn the past month, three groundwater monitoring wells that previously tested negative for tritium have now been shown to be contaminated. All three wells ‘ GZ-23S, GZ-6 and GZ-24S ‘ are north of the underground plume of tritium-contaminated groundwater that the Health Department has been monitoring for the past 13 months. GZ-23S is much closer to the plume, as it is currently defined, compared to GZ-6 and GZ-24S. GZ-23S is approximately on a line between GZ-12 and GZ-13, two sites that have both yielded samples positive for tritium over the last several months. ( Vermont Yankee Groundwater Well Map )These newest results could be evidence that the original plume is broadening from north to south along the river, or that there are other sources responsible for tritium contamination. Vermont Yankee is investigating nearby plant structures, systems and components to determine the source. Northstar Vermont Yankee,The Vermont Department of Health received laboratory data late last week from Entergy Vermont Yankee that indicates samples from groundwater monitoring well GZ-23S tested positive for low levels of tritium. Vermont Yankee’s lower limit of detection (LLD) for tritium is in the range of 670 to 700 picocuries per liter (pCi/L). The test results for the samples collected from GZ-23S during the week of January 24 were 714 and 721 pCi/L. The only sample from GZ-23S that the Health Department Laboratory has received and analyzed so far was taken on December 6 ‘ tritium was not detected in that sample. Vermont Yankee officials also noted that they are plotting all of the underground utilities that run through the plume from the Advanced Off-Gas (AOG) building area. This will help in evaluating whether these structures and components could act as conduits of tritium from the AOG plume into the area sampled by wells GZ-24S and GZ-6. Vermont Yankee officials have verified that they have made provisions to keep the river’s edge site free from winter ice that could prevent testing, and that they plan to sample the COB well again in February.   Groundwater ExtractionAccording to Vermont Yankee, as of February 3 approximately 317,000 gallons of tritium-contaminated groundwater has been pumped out of the ground to date, with approximately 9,700 of those gallons extracted since the re-start of that process on December 30, 2010. Sampling ProvisionsThe Health Department has been urging Vermont Yankee to sample river water at the river’s edge near the centerline of the AOG plume. Groundwater Monitoring Well ResultsThe results that follow are as reported by Vermont Yankee for tritium on February 3, 2011. In addition, Vermont Yankee has been reporting sample results every day to the Health Department since February 1, 2011.As of this report, 11 of the 31 groundwater monitoring wells are testing positive for tritium. With the exception of wells GZ-23S, GZ-6 and GZ-24S, the trend over the past several months has been that tritium concentrations in groundwater near plant structures, systems and components are decreasing. Trends for wells GZ-14 and GZ-22D, the two extraction sites, are trending downward as expected. Trends for GZ-23S, GZ-6 and GZ-24S, as described above, have remained relatively stable over the past two weeks. For this week, only GZ-15 had an increased tritium concentration compared to the last sample date.To date, gamma spectroscopy and special analyses for hard-to-detect radionuclides have not identified any other nuclear power plant-related radioactive materials in groundwater, drinking water or river water.GZ-1: GZ-2: GZ-3: 108,000 on 1/31/11, down from 121,275 on 1/24/11GZ-4: 70,000 on 1/31/11, down from 78,555 on 1/24/11GZ-5: GZ-6: GZ-7: 3,117 on 1/31/11, down from 3,474 on 1/4/11GZ-8: No sample; dry wellGZ-9: GZ-10: GZ-11: GZ-12S: 1,877 on 1/31/11, down from 3,268 on 1/17/11GZ-12D: 114,962 on 1/31/11, down from 130,857 on 1/17/11GZ-13S: GZ-13D: 880 on 1/31/11, down from 1,095 on 1/4/11GZ-14S: 334,136 on 1/31/11, down from 442,149 on 1/10/11GZ-14D: GZ-15: 144,700 on 1/26/11, up from 141,585 on 1/4/11GZ-16: GZ-17: GZ-18S: GZ-18D: GZ-19S: GZ-19D: GZ-20: GZ-21: 6,853 on 1/31/11, down from 8,673 on 1/17/11GZ-22D: 354,906 on 1/31/11, down from 398,557 on 1/17/11GZ-23S: GZ-24S: 4,857 on 2/3/11, down from 8,139 on 1/26/11GZ-25S: GZ-26S: GZ-27S: Source: Vermont Department of Health 2.7.2011 Vermont Yankee officials noted that the soils near GZ-24S and GZ-6 are of very low permeability. This means groundwater moves slowly through the soils. State officials will get further hydrogeological information at a technical briefing scheduled for February 10. The Departments of Health and Environmental Conservation have recommended for some time that samples be frequently obtained from the Construction Office Building (COB) well. Regular sampling will help determine the tritium concentration in this former drinking water well, which is 360 feet deep into bedrock, and help to better understand if other deep water sources could become contaminated. Groundwater Source InvestigationIn a teleconference on February 3, Vermont Yankee noted that it had completed pressure testing of two piping runs suspected as possible sources of new leaks. These are two of five piping runs that are high on the list of possible sources near GZ-24S. In fact, the well was sited at this location to monitor these particular piping runs. Pressure testing indicated that these two piping runs do not appear to be leaking. Preparations are underway to pressure test the other three piping runs. All of these five piping runs are drain lines for systems that normally carry gases. This means that less liquid travels through them. It also means that the concentration of other radioactive materials like cobalt-60, cesium-137 and strontium-90 (Co-60, Cs-137 and Sr-90) should be lower as compared to liquid processing lines. Vermont Yankee officials noted, however, that the concentration of tritium in these drain lines is similar to that of systems that process predominantly liquids with concentrations of about 3 million pCi/L. The Health Department Laboratory will continue to perform additional analyses on well samples from this new investigation area.last_img read more