2008-09-04_HYDROLOGY - M2007044 - Laserfiche WebLink

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Effluent Limitation Exceedances June 2008 Parameter Limit Type Effluent Analytical Limitation Result Selenium 30-day average 20 mg/L 21 mg/L WET Test Ceriodaphnia 100% 75% lethality WET Test Pimephales 100% 25% lethality It should be noted that only 100,000 gallons of water were treated in June 2008. This is well below the permitted discharge volume of 900,000 gallons (based on the 0.03 mgd permit limit over 30 days). One exceedance occurred for selenium of the 30-day average effluent limitation. In mid- June, prior to treatment, treated water was pumped from the sedimentation tank to the untreated water tank for cleaning operations. Some sediment was transferred with the water which may have caused resuspension of previously precipitated selenium. Energy Fuels believes this is a isolated event and that selenium will come back down to levels below effluent limitations during the treatment process. Energy Fuels is collecting additional selenium level information during the July discharge event to further examine the effectiveness of the current treatment process. It should be noted that the duplicate sample of the June 24 discharge sample, collected and analyzed by a third parry per BLM compliance stipulations, indicated that selenium was at 19.6 ug/L, below the effluent limitation. Two Whole Effluent Toxicity (WET) Test exceedances occurred during the June discharge event. Bench scale chemistry from the WET Test indicates that low Dissolved Oxygen (DO) levels in the discharge samples was the likely cause of failure. Chemical Oxygen Demand (COD) was high (56 mg/L) when the June 24 discharge sample was collected but dropped significantly as discharge progressed and was lower (14 mg/L) during the June 26 sample. The WET Test data indicates that the large majority of the species died in the sample collected on June 24 and that dissolved oxygen levels improved throughout the test. Energy Fuels believes that the water transfer discussed above contributed to the high COD and low DO levels in the initial stages of discharge. Energy Fuels has commenced with a Preliminary Toxicity Investigation (PTI) to look into the cause of WET Test failure. The PTI was discussed in a letter to your office dated July 22, 2008. Total Suspended Solids (TSS) levels have been brought down significantly from earlier months when it ranged from an average of 14 to 64 mg/L to less than 10 mg/L in June. Energy Fuels attributes this to completion of the underground mine sump and addition of flocculent that occurred in early June. Fracrg Fuck, Inc. 44 Union Blvd, Suite 600 ?hw-w.ei?erg}1'uGls.cor?2 Lakewood, Colorado 80268 Phone: 303-9-14-21 0 Fax: 303-974-2141