REV13940 - Laserfiche WebLink

Home Browse Search

<~COLORADO DEPARTMENT OF PUBL`iEALTH AND THE ENVIRONMENT, Wat~uality Control Division Rationale -Page 2, Permit No. CO-00041467 .~ Wastewater comes from jour general sources at the Urad reclamation site. The first source is the collection of seeps and subdrains along the toe ojthe dam of the upper tailing impoundment (Urad 002). This water is piped by gravity to the treatment ponds. The second source is the collection of seeps, subdrains and the original decant line along the toe of the dam of the lower tailing impoundment (Urad 003). This water is contained in the lower pump pond and is pumped !o the treatmem ponds. The third source is the surficial drainage and seasonal runoff that is collected between the Urad portal and the plug. This water is piped by gravity to the inlet of 111 Treatment Pond. The fourth source is stormwater collected on top of the lower tailing impoundment. The quality of this source is monitored and pumped to treatment as necessary. The treatment system is composed of a series of unlined ponds that reside on the lower tailing impoundment. A strong base (sodium hydroxide or equivalent) is used to adjust the pH to precipitate dissolved metals, and a flocculent (Nalco 9710 or equivalent) is used to assist in settling. A'1 and k2 treatment ponds comprise the basis for this chemical precipitation, and they can be used in series (either direction) or in parallel. Ij required, emergency treatment can be performed at the lower pump house pond. After treatment the water flows into the clearwell system which is physically divided into two ponds. The first of these ponds is called the j-well; it allows for clarification (final polishing). At the end ajthis pond, concentrated sulfuric acid (or equivalent) is added to adjust the pH to meet permit limitations. The final pond is called the clearwe[l; it allows for complete mixing of the acid to maintain a stable pH prior ro discharge into Woods Creek (Urad 004). The purpose of the unlined ponds is to allow leakage of high pH water through the tailing impoundment and provide some in-situ treatment of metals within the tailing area itself. There are two main buildings used for the addition of chemicals at the Urad site. The Largest of these buildings is known as the reagent building and is located within the "Old Mi[! Building ". Ten thousand gallons of sodium hydroxide solution is stored in this facility. Injection pumps deliver caustic to the ponds in buried, contained lines (pipe within a pipe). A carrier stream of clean (Woods Creek) water or treated process water is used to convey chemicals to their respective destinations. The flocculent polymer is stored in a 200 gallon tote and is Jlash mixed and carried to the ponds in buried, contained piping. The second building, which is located near the j-well/clearwe[1 dike, presently has a large tote of acid that supplies small dosing pumps for acid injection into a carrier system similar to that of the caustic and flocculem. Installation of a jour thousand gallon bulk acid storage tank in the "Old Mill Building" is nearly complete. The acid will then flow in a contained fine from bulk storage to the acid building. Other satellite buildings serve ancillary functions like housing pumps for supplying carrier water or vaults for accessing buried piping. Removal ojprecipitate sludge will need to be done when the ponds are not covered with ice. Cunenr plans cal[ for dredging the ponds and pumping the nonhazardous sludge through the bulkhead of the conveyor gallery and into the inactive Urad Mine. Core drill holes linking the Urad mine workings with the Henderson mine workings will allow the water ro decant to Henderson treatment.