P.O. Box 1524
Carbondale, CO 81623
(970) 903-7561

MEMORANDUM
DATE:

Sept. 4, 2015

TO:
FROM:

April Long, City of Aspen Stormwater Manager; Rick Lofaro, Director, Roaring Fork Conservancy
Bill Hoblitzell, Lotic Hydrological, LLC

SUBJECT:

RE: Water quality sampling lab results, Grizzly flush event of August 10th

1. SUMMARY
Roaring Fork Conservancy (RFC) and City of Aspen (COA) requested that Lotic Hydrological (Lotic) review
analytical results from water sampling on the Roaring Fork River conducted by city staff on August 10th, 2015.
Lotic compared sampling results to applicable instream standards promulgated by the Colorado Water Quality
Control Division (WQCD) for several beneficial use classes of water defined in the state.
Results show acute exceedances of aquatic life standards for trace metals including total aluminum and total iron
at the two sites sampled; additional exceedances for dissolved copper and manganese potentially occurred, but the
data is insufficient for complete evaluation. Sediment samples from Grizzly Reservoir show enrichment in a
similar suite of trace metals as the water quality results.
According to Twin Lakes Reservoir and Canal personnel, at least 10-20 acre feet of water and sediment flushed
from Grizzly Reservoir into Lincoln Creek and the Roaring Fork River. Although the pulse of water lasted
approximately 12 hours in the downtown Aspen area, the duration and maximum value of elevated metals
exposure cannot be determined based on the available data. Samples were collected on the afternoon of the 13th,
several days after the initial flush.
The trace metals present in the Roaring Fork River from the Grizzly flushing event of August 10th have accumulated
in the sediments of Grizzly Reservoir due to human and natural contamination sources near the historic Ruby Mine
site in the upper Lincoln Creek valley. The reservoir presently receives metal-laden water from these abandoned
mine lands, which over time settles in bottom sediments and or moves into the Roaring Fork River and Twin Lakes
Transmountain Diversion tunnel in dissolved form. Under the present management regime for both the reservoir
and the public lands on which the Ruby site is located, build-up of metal-containing sediments will continue to
occur over time, with periodic releases likely to Lincoln Creek and the Roaring Fork River.

2. BACKGROUND INFORMATION
2.1 EVENT HISTORY
As detailed in newspaper accounts, a tree lodged in the outlet works of the Grizzly Reservoir sometime around or
after August 8th, triggering concerns by operators that a larger dam works failure might be triggered by imminent
precipitation forecasted for the area. Twin Lakes Reservoir and Canal staff made the decision to drain the reservoir
and began sending water east through the divide tunnel into Twin Lakes. After draining most of the reservoir, a

 remaining amount of water and sediment estimated at between 10 and 20 acre feet drained into Lincoln Creek and
subsequently the Roaring Fork River. The rapid addition of water and yellow-colored sediments into the Roaring
Fork was quickly noticed by area residents, triggering inquiries to the local officials and RFC. The pulse of water
moved downstream in the early hours of August 10th and passed through Aspen throughout the day (FIGURE 1).
Residual amounts of turbid water continued to move downstream of the next several days.
Figure 1. Hydrograph from USGS gauge 09074300 near Stillwater Road above Aspen

Grizzly flush event

2.2 GRIZZLY RESERVOIR AND MINING IMPACTS FROM RUBY TOWNSITE
Grizzly Reservoir is a primary collection point for the transmountain water diversion system operated by Twin
Lakes Reservoir and Canal Company. The 570 af reservoir impounds the combined waters of Grizzly and Lincoln
Creeks at an elevation of approximately 10,500 feet asl in order to divert it east under the continental divide for
use by Front Range municipalities and agriculture. Typical summer releases to Lincoln Creek may be as little as a
few cfs; the peak release volume during the flush approached 130 cfs for and lasted approximately 18 hrs.
The abandoned townsite of Ruby lies approximately 4 miles upstream of the reservoir on Lincoln Creek. Ruby mine
and associated sites produced silver and other ores in the late 19th century from pyritic rocks on the highlymineralized western flanks of Red Mountain and Garfield Peak. The majority of land around the townsite is
currently administered by the US Forest Service (USFS), although privately held mining claims still exist
throughout. When surface and groundwaters flow through mineralized geology such as pyrite-bearing rocks,
oxidation of the rock produces low (acidic) pH and the mobilization of heavy metals. This condition is referred to
as acid mine drainage (AMD) if it derives from human-impacted sources, or acid rock drainage (ARD) if it flows
from natural sources.
AMD and ARD have contaminated Lincoln Creek in the 4 mile reach between Ruby and Grizzly Reservoir for an
unknown period, likely since before the beginning of the town’s development but potentially exacerbated by
historic mining activities. USFS inventoried the abandoned mine lands in 1993 and documented degradation to
Lincoln Creek from natural acid rock springs in the area and from flowing adits which contained water of low pH
and elevated metals content (Renner, 2002). The report notes anecdotal evidence of water quality degradation
from landowners, including fish kills in Lincoln Creek and stream segments completely devoid of aquatic life, as
recently as the mid-1980s. Researchers documented very acidic pH and high concentrations of aluminum, copper,
iron, manganese, and zinc in waters flowing from springs and mine adits the Ruby area into Lincoln Creek (Renner,
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 2002). Some of this water bypasses the reservoir and flows directly downstream, while some is diverted to the
impoundment.
Once the metals-laden water enters the reservoir, the increased residence time and interactions with air, sunlight,
and lake substrate allow metals to precipitate from the water column, where they enrich the lake bottom
sediments. Some amount of metals remain dissolved and either exit the reservoir into the diversion system, or
proceed downstream into the Roaring Fork. Periodic water sampling above Aspen on the Roaring Fork near
Difficult Creek has sometimes identified elevated metals concentrations. These metals likely source from both
Lincoln Creek and other mining-impacted areas in the upper Roaring Fork watershed.
2.3 AQUATIC LIFE IMPACTS
While limited amounts of metals and trace elements are necessary as micronutrients for proper function and
health of most plants and animals, excessive concentrations may cause negative chronic (long-term) effects or
acute (immediate) toxicity in stream organisms like trout. Chronic effects include reproductive and developmental
abnormalities, while acute effects might include tissue damage and death. Many streams in Colorado are
chronically impaired by metals contamination from former hardrock mining sites, and sudden releases of toxic
metals-laden water from impoundments or inner workings at these sites have periodically caused fish kills in
extended river stretches during this century. While the Roaring Fork watershed contains numerous abandoned
mine lands, the region’s streams have been relatively spared of the extreme mining-caused degradation witnessed
in other watersheds such as the upper Animas, the Uncompahgre, the Blue, and Clear Creek.
2.4 CURRENT WORK
Upon receiving reports of visible coloring and high turbidity, area stakeholders endeavored to collect samples from
several locations. On April 13th, City of Aspen staff collected water samples from the Grizzly outlet to Lincoln Creek
and at Stillwater Drive, just upstream of downtown Aspen. Staff also collected a sediment sample from the nowempty Grizzly reservoir. Accutest Laboratories of Wheat Ridge, Colorado, analyzed samples for total recoverable
trace metals and trace elements

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 3. SAMPLE RESULTS
Sample results show elevated levels of aluminum, barium, copper, iron, manganese, and zinc (TABLE 1). Sediment
results also show enrichment by the same suite of elements. These parameters mirror those noted in Lincoln Creek
by Renner (2002) in the previous USFS assessment of Ruby.
Table 1. Sampling results from August 13th.

PARAMETER
Aluminum
Antimony
Arsenic
Barium
Beryllium
Cadmium
Calcium
Chromium
Cobalt
Copper
Iron
Lead
Magnesium
Manganese
Mercury
Nickel
Potassium
Selenium
Silver
Sodium
Thallium
Vanadium
Zinc

Water samples

Sediment sample

Site 1
Site 2
Grizzly outlet Stillwater Drive
concentration (μg/l)
11800
2700
<30
<30
<25
<25
258
49.4
<10
<10
<10
<10
20700
11200
<10
<10
6.6
<5.0
272
61.7
12900
2830
<50
<50
4230
2200
791
157
<0.10
<0.10
<30
<30
2990
1420
<50
<50
<30
<30
2010
2160
<10
<10
<10
<10
72.7
<30

Site
Grizzly Reservoir
Parameter concentration (mg/kg)
Aluminum
11800
Antimony
<5.0
Arsenic
10.1
Barium
724
Beryllium
<1.7
Cadmium
<1.7
Calcium
3510
Chromium
9.6
Cobalt
7.4
Copper
127
Iron
21400
Lead
32.1
Magnesium
3470
Manganese
686
Mercury
<0.13
Nickel
11.6
Potassium
4290
Selenium
<8.4
Silver
<5.0
Sodium
150
Thallium
<1.7
Vanadium
16.3
Zinc
152

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 Where applicable, Lotic compared sampling results to instream standards issued by the WQCD for the protection of
aquatic life and human health in the Roaring Fork watershed in segment COUCRF02, Mainstem of Roaring Fork
River from source to confluence with Hunter Creek (TABLE 2). The Clean Water Act directs that states identify
target water quality goals for rivers and streams known as ‘beneficial uses’. Chemical and narrative standards are
then set that are deemed to be protective of these uses. Nearly every stream in the Roaring Fork watershed is
classified for aquatic life use, meaning the stream is capable of sustaining a cold water fishery. Standards for
aquatic life use tend to be among the most-stringent water quality standards possible. The Roaring Fork is also
classified for Drinking Water Supply, and many communities in the valley source their water supply either directly
from the Roaring Fork or from nearby tributaries.
Some standards are assessed using dissolved concentrations of metals, while others are assessed using total
recoverable concentrations. Dissolved metals are only those which can pass through a 0.45 micron filter; total
metals include those that are entrained in longer colloidal molecules or sorbed to sediments and organic matter. It
is believed that dissolved metal are more biologically active, therefore many aquatic life standards are based
around those measures. Samples from August 13th were analyzed for total metals.
It is important to note that comparison to state standards is provided here solely to place observations from the
Grizzly flush event in the context of overall stream health. Exceedance of standards values does not comprise a
violation of state law or require direct regulatory action. Other issues such as the frequency, timing, and duration
of exceedance events all factor into the legal determination of stream impairment by WQCD. Many metals
standards are variable depending on the water hardness. Hardness is a measure of the combined amount of
dissolved calcium and magnesium present in a stream. Increasing water hardness decreases the toxicity of heavy
metals to organisms like trout, therefore water with higher hardness will also have a higher allowable
concentration of some individual metals before the standard is exceeded.
Water samples from the Grizzly outlet and Stillwater Drive exceeded standards for aluminum and iron. Because
only the total recoverable fraction was analyzed, the levels of copper, manganese, and zinc, could not be assessed
against aquatic life standards. However, based on the high results for total copper and manganese, this is a
potential likelihood that the dissolved fraction exceeded standards. Human health standards were not exceeded
for any of these parameters. Agricultural supply standards were exceeded for copper and manganese. Standards
do exist for the dissolved forms of all metals reported in Table 1, but to avoid confusion and potentially misleading
information, those standards are not included in Table 2 since only total recoverable metals were analyzed.

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 Table 2. Comparison of results to applicable water quality standards.
Exceedances are noted in red, while results below standards are green. Sample parameters of zero or below the
detection level of the lab’s analytical equipment (non-detects) are denoted by ‘nd’. All standards and sample results
are ppb, or μg/l and represent the acute standard where available for aquatic life use class, or the chronic standard
for all other classes.

1.

(1.3695*(log(hardness))-0.1158)

Aluminum uses a hardness-based equation to calculate the table value standard (TVS). For pH >= 7.0, e
(1.3695*(log(hardness))-0.1158)))
pH <= 7 use either 87 or e
, whichever is less.

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, for

 4. REVIEW AND DISCUSSION
The water and sediment pulse that came down the Roaring Fork from the flushing of Grizzly Reservoir contained
elevated levels of several dissolved metals including aluminum, copper, iron, manganese, and zinc. These metals
continually accumulate in the sediments of Grizzly Reservoir due to acid mine drainage from the Ruby Mine site
and natural acid rock drainage from the highly-mineralized geology in the mountainside above Ruby Mine.
City personnel were able to collect a limited number of samples at several locations. The metal-impacted water
experienced significant dilution in the time it was released to the time it reached Aspen due the mixing of cleaner
water with Lincoln Creek from the upper Roaring Fork and tributaries like Difficult Creek. This is evident by the
decrease in metals concentrations between the reservoir outlet sample and the sample from Stillwater Drive. Lab
analysis shows that concentrations of aluminum and iron in the river temporarily exceeded water quality
standards set by the state to protect aquatic life like fish and macroinvertebrates; concentrations of copper also
likely exceeded standards, but the amount of data is insufficient to say definitively.
The pulse was short-lived, passing through Aspen in approximately 24 hours. At this point, to the knowledge of
RFC, COA staff, and Lotic, no evidence of acute effects has been related by residents and professional fishing guides
who frequently work on this section of the river. Acute effects could have included fish kills or other evidence of
damage to tissues in stream organisms. Macroinvertebrate sampling at several long-term reference sites will occur
this month by City of Aspen contractors and may yield more information on potential chronic, or long-term,
impacts if any occurred.
However it is likely and hopeful that the short-duration of the event and dilution of the metal-impacted water by
tributaries as it moved downstream will not produce long-term effects. Aesthetic impacts such as rock staining
and deposition of colored sediment should improve over time as more water dilutes and flushes them
downstream.
Acid mine drainage and acid rock drainage from the abandoned mine lands and hillslopes near Ruby is an ongoing
condition which annually delivers a significant load of metals to Lincoln Creek and Grizzly Reservoir. Metals will
continue to sorb to sediments in the reservoir and river bottom, accumulating yearly in each layer of additional
sediment deposited during spring runoff and heavy precipitation events. Under the present management regime
for both the reservoir and the public lands on which the Ruby mine site is located, this build-up of metal-containing
sediments will continue to occur over time, with periodic releases to Lincoln Creek and the Roaring Fork River
remaining likely.

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 5. REFERENCES
Gardner-Smith, B. 2015, August 18. Progress made on Grizzly Reservoir Repairs. The AspenTimes. Online.
http://www.aspentimes.com/news/17773952-113/progress-made-on-grizzly-reservoir-repairs
Renner, S. 2002. Lincoln Creek water quality report. Report to the White River National Forest by the Colorado
Division of Minerals and Geology. Grand Junction, CO.

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