Brief summary of water quality and graphs by year for the Animas River

1. Map 1 showing select current sampling locations around Silverton. These locations are sampled by EPA and Colorado Riverwatch approximately monthly. Sample results are available on their websites.

a. A68 – on the Upper Animas River above the confluence with Cement Creek

b. CC48 – on Cement Creek above the confluence with the Upper Animas River

c. M34 – on Mineral Creek above the confluence with the Upper Animas River

d. A72 – on the Animas River downstream from Silverton and Cement and Mineral Creeks.

2. Map 2 showing select sampling locations in the Animas River Canyon below Silverton. These three locations were sampled by the Bonita Creek Mining District (BPMD) Community Action Group (CAG) approximately monthly from 2019 – 2024, and approximately quarterly since then.

a. A73RB – in the Animas River Canyon below the confluence with Elk Creek

b. A75Dcw – in the Animas River Canyon above the confluence with Crazy Woman Creek

c. A75Ba – in the Animas River Canyon below the confluence with Cascade Creek.

3. Graphs of historical water quality at location A72.

a. Figure 1 - A72 Dissolved Zinc from 1992 – 2024, summarized in 5-year increments

b. Figure 2 - A72 Dissolved Zinc concentration vs Dissolved Zinc TVS from 2020 – 2024.

4. Graphs of water quality at location A75Ba.

a. Figure 3 - A75Ba Dissolved Zinc vs Dissolved ZincChronic TVS

b. Figure 4 - A75Ba Total Aluminum vs Total Aluminum Chronic TVS

c. Figure 5 - A75Ba Dissolved Cadmium vs Dissolved Cadmium TVS

d. Figure 6 - A75Ba Total Iron vs Total Iron TVS

e. Figure 7 - A75Ba Total Lead vs Total Lead TVS.

Summary of Water Quality in Animas River

Surface water quality data for the Animas River watershed have been collected by multiple government agencies and other entities beginning in 1988. Thousands of samples have been collected from streams, tributaries, springs, seeps and adits. This includes more than 4,000 surface water samples from the Upper Animas River, and more than 1,000 surface water samples from both Cement Creek and Mineral Creek.

Map 1 shows select surface water sampling locations around Silverton. Surface water quality data collected at location A72 provide a good summary of water quality in the Upper Animas River from 1992 – 2024. Dissolved zinc is a major metal contaminant in the Animas River and a good indicator of water quality changes during this lengthy sampling period. The following graphs display dissolved zinc data.

Figure 1 – this graph of dissolved zinc (D_Zn) at A72 shows data for those years in 5 year increments. There does not appear to be much change in dissolved zinc over the time period, likely due to variations in seasonal flow volume as well as localized rainfall events that bring dissolved zinc into the stream.

Figure 2 - this graph shows dissolved zinc at A72 for the years 2020 – 2024 compared to the State of Colorado’schronic Table Value Standard (TVS) for dissolved zinc (D_Zn Chronic TVS). The TVS is a water quality limit set by the State to protect aquatic life, and is calculated based on the water hardness measured when the water sample is collected. The State has set both chronic (long-term) TVS and acute (short-term) TVS limits for dissolved zinc. In general, water quality is impaired when the D_Zn concentration exceeds the D_ZnChronic TVS. What does this graph show? First, this close-up of the data shows that dissolved zinc appears to be decreasing over time: note that the trend line for D_Zn slopes down from approximately 440 micrograms per liter(mg/l) to 240 mg/l in this time period. The D_Zn Chronic TVS trend line also slopes down from approximately 560 mg/l to approximately 480 mg/l. Second, during most of the year D_Zn is greater than D_Zn Chronic TVS, indicating that the Animas River is impaired for dissolved zinc. The only time the river is not impaired is during spring periods of high flow (note the red arrows).

Map 2 shows select surface water sampling locations in the Animas River Canyon. These locations were sampled by the CAG approximately monthly from late 2019 through 2024. Water samples from the furthest downstream location (A75Ba – below Cascade Creek) provide a good summary of changes in water quality in the Animas River Canyon. The following graphs report water quality for five metals that exceed their corresponding TVS: zinc, aluminum, cadmium, iron and lead.

Figure 3 – this graph shows D_Zn versus D_Zn Chronic TVS at A75Ba. It is comparable to the graph for location A72 in that D_Zn is decreasing over the time period, yet D_Zn exceeds the D_ZN Chronic TVS much of the year. The interesting difference is that the river is impaired (D_Zn is greater than D_Zn Chronic TVS) much of the year,,but meets the standard during the fall period of low flow.

Figure 4–this graph shows total aluminum (T_Al) versus total aluminum chronic TVS (T_Al Chronic TVS) at A75Ba. The trend line shows a minimal decrease in T_Al during this time period. Total aluminum generally exceeds the TVS from early spring through the summer, meaning the water quality is impaired for aluminum during that time period. T_Al is typically less than T_Al Chronic TVS during late summer low flow through winter base flow (note the red arrows).

Figure 5 – this graph shows dissolved cadmium (D_Cd) versus dissolved cadmium TVS (D_Cd TVS) at A75Ba. The trend line indicates that D_Cd has increased slightly during this time period. Dissolved cadmium generally exceeds the D_CdTVS from early spring through the fall low flow, meaning the water quality is impaired for cadmium during that time period. D_Cd is typically less than D_Cd TVS during late fall low flow through winter base flow (note the red arrows).

Figure 6 – this graph shows total iron (T_Fe) versus total iron TVS (T_Fe TVS) at A75Ba. The TVS for iron is not hardness dependent, thus the Fe_TVS is has constant value of 1,000 mg/l. In general, T_Fe exceeds the Fe_TVS during fall low flow through winter-early spring base flow, meaning the river is impaired for lead during that time period. The river meets the Fe_TVS only during spring/summer high flow volume.

Figure 7 – this graph shows total lead (T_Pb) versus total lead TVS (T_Pb TVS) at A75Ba. The trend line shows a decrease in total lead over the time period. Total lead exceeds the T_Pb TVS during the summer high flow volume, meaning the river is impaired for total lead during that time period. Interestingly, the graph also shows that dissolved lead (Dis_Pb) is not detected in the samples at any time during the sampling period. This indicates that, during summer high flow, lead in particulate form is mobilized in the drainage system to such a great extent that it impairs the water quality.

BY: David Palmer

Database Manager

Bonita Peak Mining District (BPMD) Community Action Group (CAG)