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04/17/1995 15:49 303-782-0~ CDH WWCD WOCC PAGE 03 • r ~. Urad Wt,i•tewater Tr~atmaat Procse• Wastewater comes from four general sources at the Urad reclamation site. The first source ie the collection of seeps and subdraina along the toe of the 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, aubdraine, 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 to the treatment ponds. The third source is the aurficial drainage and seasonal runoff that ie collected between the Urad portal and the plug. This water is piped by gravity to the inlet of #1 Treatment Pond. The fourth source ie etormwater collected on top of the lower tailing impoundment. The quality of this source ie monitored and pumped to treatment as necessary. The treatment system is composed of a aeries of unlined ponds that reside on the lower tailing impoundment. A etxong base (sodium hydroxide or equivalent) is used to adjust the pH to precipitate dissolved metals, and a flocculant (Nalco 9710 or equivalent) is used to assist in settling. #1 and #2 treatment ponds comprise the basis for this chemical precipitation, and they can be used in series (either direction) or in parallel. If required, emergency treatment can be performed at the lower pump house pond. After treatment the water flows into the c:learwell 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 of this pond concentrated sulfuric acid (or equivalent) is added to adjust the pH to meet permit limitations. The final pond is called the clearwell; it aJ.lows for complete mixing of the acid to maintain a stable pH prior to 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 ae the reagent building and is located within the "~~ld Mill Building". Ten thousand gallons of sodium hydroxide soltation ie 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 ie used to convey chemicals to their respective deatination~e. The flocculant polymer ie stored in a 200 gallon tote and i.s flash mixed and carried to the ponds in buried, contained piping. The second building, which ie located near the j-well/clearwe:L1 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 flocculent. Installation of a four thousand gallon bulk acid storage tank in the "Old Mill Building" is nearly complete. The acid will then flow in a contained line from bulk storage to the acid building. other satellite building6 serve ancillary functions like housing pumps for supplying Carrier water or vaults for accessing buried piping.