Laserfiche WebLink
I. Quantitative Impacts of Mining ~ <br />Surface Water <br />There are two USGS water monitoring sites on the Purgatoire which are of interest to this site: <br />Site 07124050 at Stonewall, Colorado on the Middle Fork and Site 07124200 at Madrid, <br />Colorado, on the main stem of the Purgatoire River. The Stonewall site is located approxi- <br />mately 4 miles upstream of New Elk while the Madrid site is located six miles downstream of <br />Golden Eagle. The Stonewall site gages the runoff from 52.1 square miles while the Madrid <br />site gages the runoff from approximately 505 square miles of watershed. Between these two <br />stations, numerous ephemeral streams join the river. <br />Records of runoff as measured at Stonewall were recorded from 1978 to 1981, while records <br />of runoff at Madrid are available from 1972 to present. During the period of record, flow at <br />Stonewall ranged from 2.8 to 522 cfs, while flow at Madrid ranged from 3.0 to 1640 cfs. <br />Figures 1 and 2 have plotted the minitnum monthly low flow for the two sites for 'the period <br />of record. It suggests that the minimum monthly low flow for Stonewall is 4 c1.'s and the <br />minimum monthly low flow at Madrid is 9 cfs, and that it occurs in January. [The monthly low <br />flow data at Madrid is higher than the 7 cfs originally extrapolated in the 1980 Waste, <br />Water and Land (WWL) Report.] • <br />Data collected by the operator between 1984 and 1993 at PRS-1, on the Middle Fork of the <br />Purgatoire above New Elk, shows a range of data from 3.17 to 116.2 cfs during instantaneous <br />monthly sampling (Table 1). The low flow value is correlative with data collected at :stonewall. <br />Data collected by the operator at PRS-3 on the North Fork of the Purgatoire below Golden Eagle <br />between 1984 and 1988 and in 1993 show a range of flow data from 4.97 to 172.4 cfs during <br />instantaneous monthly sampling (Basin Resources, 1994) (Table 2). <br />Specific conductance is inversely proportional to flow. Figure 3 notes a range of conductivity <br />at Stonewall from 112 to 418 umhos/cm for 77 and 7 cfs respectively. Figure 4 notes a range <br />of conductivity at Madrid from 270 to 590 umhos/cm for 155 and 9 cfs respectively. Data <br />collected by the operator at PRS-1, above New Elk on the Middle Fork of the Purgawire, show <br />a range of 179 to 610 umhos/cm at PRS-1 and 153 to 510 umhos/cm at PRS-3, below Golden <br />Eagle on the North Fork of the Purgatoire. (The conductivity of 930 umhos/cm acquired at <br />PRS-3 on December 28, 1992 was eliminated from consideration due to the poor t:orrelation <br />with the total dissolved solids value.) <br /> <br />1 <br />