Laserfiche WebLink
~i <br /> <br />the south dike of the old pond and from decant chimney <br />outlets in the old pond. These discharges er.ceed EPA <br />• e::fisting source standards for zinc and pH. <br />The discharge from the old pond should qualify as an <br />er.isting source and could be permitted. However it would be <br />necessary to pretreat the effluent to reduce the zinc <br />concentration and raise the pH. "Neutralize and Settle" <br />methods should be adequate. The resumption of operation of <br />the new pond may qualify it as a new source for which no <br />discharges are permitted. Therefore it will be necessary to <br />seal the new pond to prevent leakage into the underlying <br />ground water. <br />RECOMMENDATIONS <br />The breached portions of the dike of the seepage retention <br />pond south of the old pond and the west dike of the Phase <br />III & IV Er.pansion ponds should be repaired and protected <br />from flood waters by riprap ar gabions. The former is <br />necessary to provide a means of impounding the contaminated <br />water currently discharging from under the old pond. The <br />latter is necessary to prevent the comingling of pond <br />seepage water with the Animas River. In addition, the <br />repaired Phase IV E>:pansion pond could serve as the overflow <br />impoundment for the decant pond during periods of e>:cessive <br />• precipitation. The outfalls should be routed as shown on <br />Figure No.l, with the decant pond discharging into the Phase <br />IV pond, which in turn discharges into the seepage pond. The <br />derelict equipment left in the pond by previous operators <br />should be removed and properly disposed of. A Corps of <br />Engineers 6redge and Fill (section 404) Permit will be <br />necessary as the area meets wetlands criteria. Given the <br />scope and purpose of the work, this permit should be <br />obtained with little difficulty. <br />The inner faces of all di4;es, where impoundment of tailings <br />liquors is contemplated, should be sealed with bentonite or <br />other suitable membrane. <br />Monitor wells nos. 1 and 16 which are presently in <br />accessible should be repaired or replaced to provide ground <br />water monitoring sites east of the ponds. <br />A monitoring program conforming to that discussed in the <br />section titled "Recommended Monitoring Program" should be <br />intitiated after having obtained input from the Water <br />Quality Control Commission (WQCC) regarding the proposed <br />program. <br />• -2- <br /> <br />