Perchlorate Update
• Conflicting mandates and goals on both sides have led to polarization on issue. • State of current research into most susceptible population (e.g., pregnant females) is currently lacking, but on- going (National Academy of Sciences due later this year)
How much is too much and how stringent do standards have to be? • California EPA’s public health goal is now 6 ppb which includes a ten-fold margin of safety. • Of the 70 chemicals in California that have a public health goal, only four --- lead, nitrates, fluoride, and now perchlorate --- have a margin of safety set at ten fold.
• All others set at 100 – 1000 fold. • The difference is trying to set a limit to prevent a precursor to a health effect, rather than a direct health effect. • California will set its maximum contaminant level later this year/early next year.
If it’s not there, it’s not an issue • The good news is that levels are decreasing due to clean up and restoration. • The bad news; drought may dampen the effects of restoration and treated water after clean up is still releasing relatively amounts of perchlorate into the system.
Kerr McGee Control Strategy • Capture and treat at 3 locations; – On KMCC property – Midway between KMCC property and Las Vegas Wash – Near Las Vegas Wash • Current Status – On KMCC property: Source control achieved in 2001 (slurry wall and 22 extraction wells capture about 90% of mass flow or 890 pounds/day). – Between KMCC and LVW: 8 extraction wells capture an estimated 90-95% of mass flow (810 – 860 pounds/day) – Near LVW: Seep and 9 extraction wells capture 60-70% of mass flow (550 – 650 pounds/day).
• KMCC Water Treatment: A total of 100 gpm captured from the 3 areas using 15 ion exchange units. • Each unit is 99+% efficient and the treated water still contains 500 to 2000 ppb perchlorate before discharged back into LVW. • Controls in place remove 2300 – 2700 pounds of perchlorate/day.
• Treated water discharged into Las Vegas Wash is 80 to 330 times higher than California EPA’s public health goal of 6 ppb. • Still, this treatment/remediation is better than previous which was, basically, no treatment at all.
Perchlorate in Lake Pleasant and the CAP Canal
Winter 03/04 Fall 03 Summer 03 CAP2 Sampling_Period by Site Spring 03 Winter 02/03 Fall 02 Summer 02 Winter 03/04 Fall 03 Summer 03 CAP1 Spring 03 Winter 02/03 Fall 02 Summer 02 0 1 2 3 4 5 6 7 Mean(Perchlorate (ppb))
Winter 03/04 MGPLEC Fall 03 Summer 03 Spring 03 Winter 02/03 Sampling_Period by Site Fall 02 Summer 02 Winter 03/04 MGPLEB Fall 03 Summer 03 Spring 03 Winter 02/03 Fall 02 Summer 02 Winter 03/04 MGPLEA Fall 03 Summer 03 Spring 03 Winter 02/03 Fall 02 Summer 02 .0 1.0 2.0 3.0 4.0 Mean(Perchlorate (ppb))
Bivariate Fit of Depth_m By Perchlorate (ppb) 40 30 20 10 Depth_m 0 -10 -20 -30 -40 -50 1 2 3 4 Perchlorate (ppb) Linear Fit Linear Fit Depth_m = -14.54894 + 2.876356 Perchlorate (ppb) Summary of Fit RSquare 0.012189 RSquare Adj -0.01774 Root Mean Square Error 19.71044 Mean of Response -7.71143 Observations (or Sum Wgts) 35
Mean(Perchlorate (ppb)) 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 081602 A Downward Trend in 082102 111902 Pleasant? 112002 022703 052203 080503 112603 021004
Hopefully, control measures at the point source(s) will hasten the continued decline in perchlorate that we find in Arizona and throughout the West.
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