Ci Ci City of Virginia Beach City of Virginia Beach f Vi f Vi i i B i i B h h Uranium Mining Impact Study Uranium Mining Impact Study Uranium Mining Impact Study Uranium Mining Impact Study City Council Briefing City Council Briefing February 1 2011 February 1 2011 February 1, 2011 February 1, 2011
Kerr Dam Mouth of Kerr Reservoir
The Lake Gaston Water Transfer: The Lake Gaston Water Transfer: Roanoke River Basin to Virginia Beach R R Roanoke River Basin to Virginia Beach k Ri k Ri B B i i Vi Vi i i B i i B h h
Task and Task and Purpose of the Study as a d as a d u pose o t e Study Purpose of the Study u pose o t e Study � Model Model and estimate the water quality impacts Model and estimate the water quality impacts Model and estimate the water quality impacts and estimate the water quality impacts from a storm from a storm ‐ based breach of a uranium mill based breach of a uranium mill tailings confinement structure, which results in tailings confinement structure tailings confinement structure which results in tailings confinement structure, which results in which results in a a large large release of mill release of mill tailings downstream to tailings downstream to the Banister or Roanoke rivers the Banister or Roanoke rivers � Provide the results to the National Academy of Provide the results to the National Academy of y Sciences Uranium Mining Committee for Sciences Uranium Mining Committee for consideration as part of its study due Dec 2011 consideration as part of its study due Dec 2011
Study Qualifiers Study Qualifiers y � The study is simulating a rare event that The study is simulating a rare event that regulations are supposed to prevent regulations are supposed to prevent l l i i d d � The The model does not address the issue of model does not address the issue of whether there will be a catastrophe whether there will be a catastrophe – it it only only simulates the simulates the outcome if one simulates the simulates the outcome if one outcome if one did occur outcome if one did occur did occur did occur � In order to deliver a credible product in the In order to deliver a credible product in the time frame provided and within the time frame provided and within the f f d d d d d d h h h h resources allotted, certain assumptions and resources allotted, certain assumptions and concessions concessions were made were made
Model Scenarios Model Scenarios � Roanoke Roanoke River Basin, Dan River Basin and River Basin, Dan River Basin and B Banister River Basin from headwaters to Banister River Basin from B i t i t Ri Ri B B i f i f h h headwaters to Kerr d d t t t t K Kerr Dam Dam � 10 10 10 10 ‐ yr yr, 100 , 100 ‐ 100 100 ‐ yr, and 500 yr, and 500 ‐ yr floods were d 500 d 500 yr floods were modeled, fl fl d d modeled, d l d d l d as well as “sunny as well as “sunny ‐ day” failures day” failures � After After each Aft Aft each flood, a h fl fl flood, a typical year with normal d d typical year with normal t t i i l l ith ith l l flows flows was was appended appended to judge long to judge long ‐ term term effects effects � Confinement cell dam heights: C Confinement cell dam heights: 5, 15, 30 & 50 C fi fi t t ll d ll d h i ht h i ht 5, 15, 30 & 50 m 5 15 30 & 50 5 15 30 & 50 m � Radioactivity of tailings Radioactivity of tailings – RAD1 (lower) and RAD1 (lower) and RAD2 (hi h RAD2 (hi h RAD2 (higher) RAD2 (higher) ) )
Aftermath of a Tailings Release Aftermath of a Tailings Release g � Tailings separate into Tailings separate into particulate particulate and and dissolved dissolved components components � Most of the particulates tend Most of the particulates tend to remain above to remain above Kerr Dam Kerr Dam – in in the reservoir, the reservoir, river river bed and bed and flood flood plain sediments plain sediments � The dissolved contaminants move downstream The dissolved contaminants move downstream with the water with the water and flow into Kerr Reservoir and flow into Kerr Reservoir and then into Lake Gaston and then into Lake Gaston d th d th i t L k G i t L k G t t � Ultimately, most dissolved contaminants flow Ultimately, most dissolved contaminants flow downstream downstream ‐ d d t t ‐ out of the two reservoirs out of the two reservoirs t f th t t f th t i i
Particulate vs Dissolved Contaminants
Impacts Above Kerr Dam Impacts Above Kerr Dam p � Significant radioactive Significant radioactive sediments in the river bed, sediments in the river bed, flood plain and flood plain and reservoir flood plain and flood plain and reservoir reservoir reservoir � Radioactivity in Radioactivity in the water column the water column is initially is initially very very high, but high, but declines high, but high, but declines declines as the particulates settle and the declines as the particulates settle and the as the particulates settle and the as the particulates settle and the dissolved dissolved contaminants contaminants flow flow downstream downstream � Radioactivity Radioactivity of the sediments remains high on a y of the sediments remains high on a g long long ‐ term term basis basis � High flows High flows re re ‐ suspend a portion of the settled suspend a portion of the settled particulates and particulates and move them move them incrementally to Kerr incrementally to Kerr � Most particulates Most particulates will remain in the flood plain, will remain in the flood plain, river bottom, river bottom, or Kerr Reservoir b or Kerr Reservoir
Water Quality Impacts in Kerr Reservoir Water Quality Impacts in Kerr Reservoir � Radioactivity in Radioactivity in the water column the water column 10 10 – 20 times 20 times greater greater than g g than SDWA MCL’s accumulates SDWA MCL’s accumulates in Kerr in Kerr Reservoir over a period of Reservoir over a period of months months � With normal inflows, contaminants in Kerr settle � With normal inflows, contaminants in Kerr settle With normal inflows, contaminants in Kerr settle With normal inflows, contaminants in Kerr settle out or are flushed out or are flushed from from the water column into the water column into Lake Gaston in roughly two to six months Lake Gaston in roughly two to six months Lake Gaston in roughly two to six months Lake Gaston in roughly two to six months � In time, contaminants would flow out of Gaston In time, contaminants would flow out of Gaston � Flushing time is very Fl Fl Flushing time is very dependent upon the hi hi ti ti i i d dependent upon the d d d t t th th magnitude and timing of stream flows after a magnitude and timing of stream flows after a t ili t ili tailings release tailings release l l
Radioactivity Concentration in the Water Column from Radium ‐ 226 and Thorium ‐ 230 Banister + Dam 15m + CSW3 50% + HYD2 1% + GSC1 + RAD2 50 Ci/L) 45 oncentration (p 40 35 30 Node 286 ‐ At Mouth of Kerr Reservoir 25 Node 397 ‐ At Kerr Dam Radioactivity Co MCL for Combined Radium ‐ 226 and 228 20 15 10 5 R 0 0 50 100 150 200 250 300 350 400 Time (Day) Radioactivity Concentration in the Water Column from Radium ‐ 226 and Thorium ‐ 230 Roanoke + Dam 15m + CSW3 50% + HYD2 1% + GSC1 + RAD2 Roanoke+ Dam 15m + CSW3 50% + HYD2 1% + GSC1 + RAD2 100 ration (pCi/L) 90 80 70 activity Concentr 60 Node 311 ‐ At Mouth of Kerr Reservoir Node 420 ‐ At Kerr Dam 50 MCL for Combined Radium ‐ 226 and 228 40 30 Radioa 20 20 10 0 0 50 100 150 200 250 300 350 400 Time (Day)
Model Limitations Model Limitations – Flushing Time Flushing Time � Kerr Reservoir was modeled as a large, one Kerr Reservoir was modeled as a large, one ‐ di dimensional channel – a giant river dimensional channel di i i l h l h l l a giant river i i i i � Reasonable during flood periods. During normal Reasonable during flood periods. During normal and drought periods, Kerr Reservoir will act and drought periods, Kerr Reservoir will act more like a lake more like a lake � Dissolved contaminants will experience mixing, Dissolved contaminants will experience mixing, dispersion, stagnation. May add to flushing time dispersion, stagnation. May add to flushing time p p , , g g y y g g � Lake Gaston has a volume equal to about half of Lake Gaston has a volume equal to about half of Kerr Reservoir which will add to flushing time Kerr Reservoir which will add to flushing time Kerr Reservoir which will add to flushing time Kerr Reservoir which will add to flushing time
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