2012-05-03_REPORT - C1981014 (2)

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EFCI Southfield Mine — 2011 Annual Hydrology Report April 25, 2012 Loadout Area The Loadout and adjacent areas fall within the lower sections of the Oak and Chandler Creek drainages, both of which are tributary to the Arkansas River. Oak Creek is a perennial drainage above the municipal well field for the Town of Rockvale. Dependent on water demand and withdrawal levels for Rockvale, flows in Oak Creek below the well field in the 4.7 mile section above the Loadout area may be either perennial or ephemeral. In areas adjacent to the Loadout Area, flows in Oak Creek are frequently ephemeral, and Chandler Creek is considered an ephemeral creek (refer to Section 2.04.7 of the Southfield permit application for more details). EFCI monitors any stormwater runoff discharge from the two active sedimentation ponds, Ponds L -1 and L -2, in the Loadout Area. In the Loadout Area, the current surface water monitoring program includes the following monitoring stations: Station Location NPDES 001 W''NW1/4, Sec 17 NPDES 002 E%NE' /4, Sec 19 Designation Pond L- I (outfall to Chandler Creek) Pond L -2 (outfall to Oak Creek) Oak Creek monitoring locations were eliminated in accordance with approved Technical Revision No. 37. Oak Creek flow measurements made from 1998 through 2009, are presented for the two stream monitoring locations on Table 8. Stream flow data from previous years are documented in AHR's on tile at the Division. Historic field and laboratory water quality data (prior to 2010) for surface water monitoring stations on Oak Creek are provided in previous AHR submittals. The two Loadout area sedimentation ponds have historically held only a small amount of water, and have never discharged to the stream system. Similar to previous years, both ponds remained dry so there was no pond discharge during 2011. 2011 AHR text doc Page 17