0071-2858-MTDC: Adit Discharge Summary for the Elkhorn and Charter Oak Mines, MT: The Charter Oak Mine continued

[photo] Toxic pond near the Charter Oak adit.

Figure 3—The Charter Oak adit and the recorder installed about 50
feet downstream. The pond is very toxic. Water from the
pond eventually runs into the creek below.

[image] Graph showing peak times for discharge at the Charter Oak Mine.

Figure 4—Discharge peaked at the Charter Oak lower adit from
April to June 1999. These data suggest that the recharge
area for this adit is localized

Field parameters such as temperature, pH (acidity), and specific conductivity generally show seasonal trends (figures 5a, 5b and 5c). Water temperature, for example, follows a seasonal trend, with diurnal fluctuations. In early February 1999, the discharge stream around the temperature probe froze completely, as indicated by the negative values. Overall, water quality appears to be best just before the spring melt and poorest during higher flows. The data are shown in table 1.

[image] Graph showing fluctuation in temperature at the Charter Oak Mine.

Figure 5a—The greatest fluctuation in temperature (figure 5a),
pH (figure 5b), and specific conductivity (figure 5c) at the
Charter Oak Mine coincided with seasonal changes in discharge;
the higher the discharge, the higher the pH, and the
lower the specific conductivity.

[image] Graph showing fluctuations in pH at the Charter Oak Mine.

Figure 5b—Fluctuations in pH at the Charter Oak Mine
from July 1998 to June 2000.

[image] Graph showing fluctuations in specific conductivity at the Charter Oak Mine.

Figure 5c—Fluctuations in specific conductivity at the Charter
Oak Mine from July 1998 to June 2000.

Table 1—The concentration of metals in the adit discharge at the Charter Oak Mine varied during different seasons.
Sample Date	pH	Fe (mg/L)	SO4 (mg/L)	Al (mg/L)	As (mg/L)	Cd (mg/L)	Cu (mg/L)	Ni (mg/L)	Zn (mg/L)	Pb (mg/L)
6/6/1995	2.88	51.5	500	1541	4568	35.1	369	9.2	68	353
11/23/1998	2.93	31.5	433	2109	1450	28.5	287	21.7	34	2810
11/24/1998	3.01	76.6	502.9	2270	7210	34.6	555	8.8	145	3520
6/28/1999	2.7	136	764.7	3790	13000	69.6	1170	13.4	210	6680
8/30/1999	2.9	64.8	531.9	221	4170	45.1	608	14.1	84	4370
10/6/1999	2.87	45.4	469.5	2620	2340	36.3	454	11.6	53	3440
10/7/1999	2.85	37.6	431.9	2490	1670	33.3	419	11.7	40	3230

In the Charter Oak adit we discovered that the ground-water recharge and discharge system is localized in nature and could easily be controlled by ground source control methods. The water quality fluctuated throughout the year. A treatment process that was based on a single measurement at this site would probably have failed.