2013-08-14_HYDROLOGY - C1981022 - Laserfiche WebLink

Home Browse Search

To: Oxbow Mining LLC P.O. Box 535 Somerset, CO 81434 Submitted by: Jim Kiger Sample I.D.: 015B discharge Comments: Kept 4C till tested Date: August 1, 2013 No: ECA/OXBOW 14 -WET SAMPLE IDENTIFICATION Date Sampled: July 23 -27, 2013 Date Received: July 23 -27, 2013 Date Tested: July 23 -27, 2013 This letter is in response the the WET study which was done on discharge water from the Oxbow Mining Company, Elk Creek Mine. The discharge location is identified as 015B. This study was for a chronic WET test to be conducted using fathead minnows and Ceriodaphnia dubia (daphnids). The daphnids are very susceptible to high alkalinity. This was evidenced by the lethality of all daphnids within 24 hours when subjected to Oxbow water at a dilution of 100 %. The alkalinity range of this water was 1773 — 1922 mg/L. This alkalinity is substantially higher than the daphnids can tolerate. It is our opinion that the failure of the WET test was due solely to the high alkalinity as is evidenced by the survival of the daphnids in all other dilutions, equal to or greater than the control water. In addition, all other dilutions shows no significant difference on the reproduction statistic when compared to the control group. As this parameter is not one of contamination, as much as a natural occurrence, we would expect the same result with the daphnids if accelerated testing were to commence. Substitution of the daphnids with the Daphnia magna would fix the lethality issue, were the test requirement for acute testing. However, the Daphnia magna are not an acceptable species for use with a chronic test as their maturity rate is outside the 7 -day time period utilized for the chronic test and therefore, it would be impossible to measure reproduction using this species. Results submitted For Enviro -Chem Analytical, Inc. Liese K. Thompson Liese K. Thompson Lab Director