Spatial determinations of the metal loads in Wightman Fork can be used to identify potential source areas to the stream. In September 1997, a chloride tracer-injection study was done concurrently with synoptic water-quality sampling in Wightman Fork near the Summitville Mine site. Discharge was determined and metal concentrations at 38 sites were used to generate mass-load profiles for dissolved aluminum, copper, iron, manganese, and zinc. The U.S. Environmental Protection Agency had previously identified these metals as contaminants of concern. Metal loads increased substantially in Wightman Fork near the Summitville Mine. A large increase occurred along a 60-meter reach that is north of the North Waste Dump and generally corresponds to a region of radial faults. Metal loading from this reach was equivalent to 50 percent or more of the dissolved aluminum, copper, iron, manganese, and zinc load upstream from the outfall of the Summitville Water Treatment Facility (SWTF). Overall, sources along the entire reach upstream from the SWTF were equivalent to 15 percent of the iron, 33 percent of the copper and manganese, 58 percent of the zinc, and 66 percent of the aluminum load leaving the mine site. The largest increases in metal loading to Wightman Fork occurred as a result of inflow from Cropsy Creek. Aluminum, iron, manganese, and zinc loads from Cropsy Creek were equivalent to about 40 percent of the specific metal load leaving the mine site. Copper, iron, and manganese loads from Cropsy Creek were nearly as large or larger than the load from sources upstream from the SWTF.

Colorado↗

USGS2001

Diurnal variations in metal concentrations in the Alamosa River and Wightman Fork, southwestern Colorado, 1995-97

A comprehensive sampling network was implemented in the Alamosa River Basin from 1995 to 1997 to address data gaps identified as part of the ecological risk assessment of the Summitville Superfund site. Aluminum, copper, iron, and zinc were identified as the constituents of concern for the risk assessment. Water-quality samples were collected at six sites on the Alamosa River and Wightman Fork by automatic samplers. Several discrete (instantaneous) samples were collected over 24 hours at each site during periods of high diurnal variations in streamflow (May through September). The discrete samples were analyzed individually and duplicate samples were composited to produce a single sample that represented the daily-mean concentration. The diurnal variations in concentration with respect to the theoretical daily-mean concentration (maximum minus minimum divided by daily mean) are presented. Diurnal metal concentrations were highly variable in the Alamosa River and Wightman Fork. The concentration of a metal at a single site could change by several hundred percent during one diurnal cycle. The largest percent change in metal concentrations was observed for aluminum and iron. Zinc concentrations varied the least of the four metals. No discernible or predictable pattern was indicated in the timing of the daily mean, maximum, or minimum concentrations. The percentage of discrete sample concentrations that varied from the daily-mean concentration by thresholds of plus or minus 10, 25, and 50 percent was evaluated. Between 50 and 75 percent of discrete-sample concentrations varied from the daily-mean concentration by more than plus or minus 10 percent. The percentage of samples exceeding given thresholds generally was smaller during the summer period than the snowmelt period. Sampling strategies are critical to accurately define variability in constituent concentration, and conversely, understanding constituent variability is important in determining appropriate sampling strategies. During nonsteady-state periods, considerable errors in estimates of daily-mean concentration are possible if based on one discrete sample. Flow-weighting multiple discrete samples collected over a diurnal cycle provides a better estimate of daily-mean concentrations during nonsteady-state periods.

Colorado↗

USGS2001

Characterization of water quality in selected tributaries of the Alamosa River, southwestern Colorado, including comparisons to instream water-quality standards and toxicological reference values, 1995-97

A comprehensive water-quality sampling network was implemented by the U.S. Geological Survey from 1995 through 1997 at 12 tributary sites to the Alamosa River. The network was designed to address data gaps identified in the initial ecological risk assessment of the Summitville Superfund site. Tributaries draining hydrothermally altered areas had higher median values for nearly all measured properties and constituents than tributaries draining unaltered areas. Colorado instream standards for pH, copper, iron, and zinc were in attainment at most tributary sites. Instream standards for pH and chronic aquatic-life standards for iron were not attained in Jasper Creek. Toxicological reference values were most often exceeded at Iron Creek, Alum Creek, Bitter Creek, Wightman Fork, and Burnt Creek. These tributaries all drain hydrothermally altered areas.

Colorado↗

USGS2001

Assessment of water quality, road runoff, and bulk atmospheric deposition, Guanella Pass area, Clear Creek and Park counties, Colorado, water years 1995-97

The Guanella Pass road, located about 40 miles west of Denver, Colorado, between the towns of Georgetown and Grant, has been designated a scenic byway and is being considered for reconstruction. The purpose of this report is to present an assessment of hydrologic and water-quality conditions in the Guanella Pass area and provide baseline data for evaluation of the effects of the proposed road reconstruction. The data were collected during water years 1995-97 (October 1, 1995, to September 30, 1997). Based on Colorado water-quality standards, current surface-water quality near Guanella Pass road was generally acceptable for specified use classifications of recreation, water supply, agriculture, and aquatic life. Streams had small concentrations of dissolved solids, nutrients, trace elements, and suspended sediment. An exception was upper Geneva Creek, which was acidic and had relatively large concentrations of iron, zinc, and other trace elements related to acid-sulfate weathering. Concentrations of many water-quality constituents, especially particle-related phases and suspended sediment, increased during peak snowmelt and rainstorm events and decreased to prerunoff concentrations at the end of runoff periods. Some dissolved (filtered) trace-element loads in Geneva Creek decreased during rainstorms when total recoverable loads remained generally static or increased, indicating a phase change that might be explained by adsorption of trace elements to suspended sediment during storm runoff. Total recoverable iron and dissolved zinc exceeded Colorado stream-water-quality standards most frequently. Exceedances for iron generally occurred during periods of high suspended-sediment transport in several streams. Zinc standards were exceeded in about one-half the samples collected in Geneva Creek 1.5 miles upstream from Grant. Lake-water quality was generally similar to that of area streams. Nitrogen and phosphorus ratios calculated for Clear and Duck Lakes indicated that phytoplankton in the lakes were probably phosphorus-limited. Measures of trophic status (secchi depth, total phosphorus, and chlorophyll- a ) indicated that Duck and Clear Lakes were oligotrophic in 1997. Ground water had relatively low specific conductance (range 24 to 584 microsiemens per centimeter) and did not exceed U.S. Environmental Protection Agency drinking-water standards, except for samples collected from a single well, which exceeded the Proposed Maximum Contaminant Level for uranium. Runoff from the Guanella Pass road enters streams through surface channels connected to culverts and roadside ditches. Fifty-six percent of the total number of culvert and roadside-ditch drainage features on the Guanella Pass road showed evidence of recent surface runoff connection to an adjacent stream. Road runoff is generated during snowmelt and during summer rainstorms. At a road cross-drain culvert monitored continuously for discharge (water years 1996-97), most runoff (77 to 96 percent) was a result of snowmelt, and runoff from the road preceded the basinwide peak streamflow, resulting in sediment and water-quality constituent inputs to the stream when the stream’s capacity for dilution of the road runoff was low. Specific conductance of road-runoff samples ranged from 14 to 468 microsiemens per centimeter. Major-ion composition of some samples indicated effects from deicing salt (sodium chloride) and dust inhibitor (magnesium chloride) applied to sections of the road, but changes in the stream concentrations that might be attributed to the runoff were brief and relatively small. Nutrients were commonly measured in road-runoff samples at larger concentrations than in streamflow. Concentrations of nitrate and ammonia, especially during rainfall-generated road runoff, were more similar to the concentrations in precipitation than to the concentrations in stream water. Concentrations of ammonia plus organic nitrogen (total as N) (range less than 0.2 to 24 milligrams per liter) and total phosphorus (range 0.024 to 7.2 milligrams per liter) in road runoff were generally large in snowmelt and rainstorm samples and were related to abundant particulate organic material and suspended sediment in the road runoff. Trace-element data indicated that total recoverable trace-element concentrations in road runoff were substantially larger (by several times) than dissolved trace-element concentrations, indicating that most trace elements were particulate. Most of the stream trace-element standards would not likely be exceeded as a result of road-runoff constituents discharged into streams because the standards apply primarily to dissolved-phase (filtered) constituents, and the predominant phase associated with Guanella Pass road runoff is particulate. The suspended-sediment concentrations in snowmelt-generated road runoff ranged from 66 to 7,360 milligrams per liter. Rainstorm-runoff concentrations ranged from 34 to 38,800 milligrams per liter. The sediment was primarily fine grained, which facilitated transport of the sediment. The median percentage of silt and clay (finer than 0.062 millimeter) in road-runoff samples analyzed for size fractions was greater than 90 percent for snowmelt samples and 88 percent for rainstorm samples. Dilution of estimated road runoff to South Clear Creek upstream from Naylor Creek as a result of snowmelt on the road in early May (prior to peak watershed streamflows) ranged from approximately 10 to 100 times. During peak snowmelt in the watershed (early June), dilution of road runoff was estimated to be greater than 1,000 times. Dilution factors for late-summer-rainstorm road runoff were in the range of 10 to 500 times. Given the large concentrations of suspended sediment in road runoff, the potential water-quality effects of road runoff could be substantial during the low streamflows of early snowmelt and late summer base flow (low dilution capacity) but inconsequential during high streamflows (high dilution capacity). The median bulk deposition rate of filterable solids is probably related to dust deposition from roads. The median deposition rate at sites near unpaved roads was 105 times the median rate at an undisturbed reference site (located at least 500 feet away from a road), and the rate at sites near paved roads was 3 times the undisturbed reference site median rate. During August to September 1997, bulk atmospheric deposition directly on the active channel of a reach of Geneva Creek was estimated to be 1.7 tons, or about 1 percent of the estimated 165 tons of suspended sediment transported past the nearby stream-monitoring site near Grant during the same period. The estimate of 1.7 tons indicates little potential effect from direct settling of bulk atmospheric solids on suspended-sediment transport in Geneva Creek, a stream that closely parallels the Guanella Pass road.

Colorado↗

USGS2001

Summary of water-quality data, October 1987 through September 1997, for Fountain and Monument Creeks, El Paso and Pueblo counties, Colorado

Fountain and Monument Creeks, which drain parts of El Paso and Pueblo Counties in Colorado, have been sampled systematically by the U.S. Geological Survey for many years to obtain records of water-quality properties and constituents; the data are stored in the National Water Inventory System. Statistical summaries of these data indicate that they have spatial and temporal trends. Comparison of water-quality data to in-stream regulatory standards, some of which were calculated in this report, indicate that some exceedances are widespread in the system and that some occur locally. Nonparametric tests to quantitatively detect monotonic trends in water-quality data indicate that many water-quality properties and constituents do not have significant monotonic trends; detected trends were mostly downward.

Colorado↗