2014-08-01_REPORT - C1981014 - Laserfiche WebLink

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EFCI Southfield Mine — 2013 Annual Hydrology Report August 1, 2014 Surface water monitoring of mine creek sites is conducted on a semi - annual basis, typically in the second and fourth quarters of the monitoring year. Field and laboratory analysis data for surface water monitoring stations are summarized in the following discussions. Stream flow measurements since 2000 are provided in Table 8; field and laboratory data for the reporting period are included in Appendix B. Monitoring data provided on Table 8 indicate dry creek beds prevailed at the approved monitoring points at Newlin Creek, Magpie Creek and Second Alkali Creek when monitoring was conducted in May and December. These conditions are consistent with those found in recent years during the same time periods. Spring snowmelt runoff, and to a limited extent, summer thundershowers, have produced streamflow in Newlin Creek throughout the life of the mine. In 2013, EFCI conducted additional monitoring during these circumstances at locations along Newlin Creek including the Florence water reservoir (above the Mountain Park), and at the Thompson Ranch road crossing culvert. Springtime monitoring was done on April 5, 12, 19, and 24, then on May 10, 17, and 29. It was noted that the upland snow pack was minimal, and early spring rains were sparse. No flow was observed at any locations during the dates noted. Later in the year and following thunderstorm events, EFCI performed additional monitoring of Newlin Creek looking for flow or evidence of flow. Thundershowers in mid July produced about 3/8 inch flow of very muddy water at the Thompson ranch road culvert, and no evidence flow was observed at the lower monitoring point (NC -1), noted 7/15/13.. A heavy rain shower in early August resulted in no flow observed in the creek, noted 8/9/13. Monitoring after light to heavy intermittent rains in mid September documented approximately 1/4 inch of flow at the Thompson ranch road culvert, and evidence of a short duration flow at the lower monitoring point, though the flow had ceased, noted 9/12/13. Observations at upper Newlin Creek in the Mountain Park area and upper monitoring point (NC -2) on 9/13/13 indicated no flow in the streambed. Conditions noted of roads and ditches in the Mountain Park area indicated significant erosion consistent with heavy rainfall. Historic field and laboratory water quality data for the surface water monitoring stations on Newlin, Magpie, and Second Alkali Creeks are summarized in Tables 9, 10, 11,12 and 13. Ongoing monitoring of surface flows for Newlin, Magpie, and Second Alkali Creeks provides for identification and evaluation of any future changes in water quality that may result from mining and related activities. The same trends of the surface water quantity and quality as monitored during previous years continued during the report period of 2013. 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). 2018AHR.doc Page 18