Laserfiche WebLink
Memo to J. StevensiB. Humphries <br />November 7, 1995 - BMRI's Response/TR015 <br />Page 2 <br />not believe that measurement of groundwater quality at depth, i.e., at the water table, beneath the <br />tailings facility and collection pond would yield the best information to identify and monitor the <br />potential for water quality degradation potentially resulting from these facilities." If you believe <br />the fluid that may leak from the tailings facility or collection pond will migrate downward, then the <br />aquifer beneath those stnrctures would yield the best and earliest information to identify and <br />monitor water quality. Apparently, as will be noted below, BMRI has another theory about Fluid <br />migration. <br />BMRI outlines the background information of their theory on pages 3, 4 and 5. I agree with <br />BMRI's description of the Santa Fe formation (from boreholes M-3 and M-5), but disagree with <br />their contention that, due to the "interbedded nature of the formation, and the lack of a significant <br />water source above these unsaturated materials, it is highly unlikely that any fluids escaping the <br />tailings facility and/or collection pond would mach the groundwater table directly beneath these <br />facilities." It is further stated in the last paragraph on page 3 "This is related to not only the lack <br />of a water source to drive fluid, but also the preferential flow paths that exist in the thin layers of <br />coarse material located in the upper portion of the Santa Fe formation should fluid movement be <br />initiated." And that "These two factors are instrumental in developing the most apprmpriate means <br />to evaluate water quality impacts from these facilities." <br />Is it possible that BMRI believes that a "lack of water source" means there are no leaks in the <br />facilities? Paragraph 3 of page 4 states that, based on the EPA's "Leak Detection Rule", SRK <br />estimated a total volume of seepage of 474 gallons per year. This is an extremely gmall amount <br />of leakage for a facility of this size but, as will be presented below, even this amount of leakage <br />could adversely impact groundwater. <br />BMRI feels it is important to understand the concept of fluid migration in the Vadose zone, and I <br />agree with the definition presented in paragraph I of page 4, but would add that even though it is <br />a two-phase flow (air and water), the arr is generally removed from the system when it becomes <br />fully saturated. <br />I agree with the first four sentences of paragraph 2 on page 4, but disagree with the given example <br />in the rest of the paragraph. BMRI speaks of the preferential flow paths within the thin layers of <br />coarse material and yet discounts this data by saying a 32,600,000-gallon leak over tfie 200-arm <br />tailings facility would only saturate the top 10 feet of the soil profile. <br />With only a 1.3-gallon per day leak, a vertical preferential flow path (fracture) could direct the <br />contaminated water to the Santa Fe aquifer within a short time (less than a year). It would take <br />less than 300 gallons of fluid to saturate a 1' X 1' X 140' column of soil which would overcome <br />specific retention and initiate flow through the medium. <br />In the last paragraph on page 4, BMRI states that even if "specific retention was exceeded" (the <br />porous portion of the soils become saturated), "potential fluid loss from the tailings facility and <br />collection pond is likely to migrate vertically until it encounters the more permeable, coarse <br />