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Research about Denver, Colorado

Source-linked reports with geographic coverage including Denver, Colorado.

At least 37 records · Page 2Linked to original sources
USGS2008

Metals fate and transport modelling in streams and watersheds: state of the science and USEPA workshop review

Metals pollution in surface waters from point and non-point sources (NPS) is a widespread problem in the United States and worldwide (Lofts et al. , 2007; USEPA, 2007). In the western United States, metals associated with acid mine drainage (AMD) from hardrock mines in mountainous areas impact aquatic ecosystems and human health (USEPA, 1997a; Caruso and Ward, 1998; Church et al. , 2007). Metals fate and transport modelling in streams and watersheds is sometimes needed for assessment and restoration of surface waters, including mining-impacted streams (Runkel and Kimball, 2002; Caruso, 2003; Velleux et al. , 2006). The Water Quality Analysis Simulation Program (WASP; Wool et al. , 2001), developed by the US Environmental Protection Agency (USEPA), is an example of a model used for such analyses. Other approaches exist and appropriate model selection depends on site characteristics, data availability and modelling objectives. However, there are a wide range of assumptions, input parameters, data requirements and gaps, and calibration and validation issues that must be addressed by model developers, users and decision makers. Despite substantial work on model development, their successful application has been more limited because they are not often used by decision makers for stream and watershed assessment and restoration. Bringing together scientists, model developers, users and decision makers should stimulate the development of appropriate models and improve the applicability of their results. To address these issues, the USEPA Office of Research and Development and Region 8 (Colorado, Montana, North Dakota, South Dakota, Utah and Wyoming) hosted a workshop in Denver, Colorado on February 13–14, 2007. The workshop brought together approximately 35 experts from government, academia and consulting to address the state of the art for modelling metals fate and transport, knowledge gaps and future directions in metals modelling. It focused on modelling metals in high-altitude streams, rivers and watersheds impacted by mine waste that are common in the western United States and require remediation. For example, there are over 100 000 abandoned or inactive mining sites across the United States, encompassing over 500 000 acres of land that may eventually require characterization and remediation, including the possible application of stream or watershed metals fate and transport modelling (USEPA, 1997a). This article provides a general overview of the state of the science on modelling metals fate and transport in streams and watersheds, including a review of presentations and discussions at the USEPA workshop. It builds on previous summaries of metals fate and transport models in aquatic systems, including USEPA (1997b, 2007), Allen (2002), Paquin et al. (2003), Nordstrom (2004) and Maest et al. (2005).

Colorado↗
USGS2005

Hydraulic and geochemical performance of a permeable reactive barrier containing zero-valent iron, Denver Federal Center

The hydraulic and geochemical performance of a 366 m long permeable reactive barrier (PRB) at the Denver Federal Center, Denver, Colorado, was evaluated. The funnel and gate system, which was installed in 1996 to intercept and remediate ground water contaminated with chlorinated aliphatic hydrocarbons (CAHs), contained four 12.2 m wide gates filled with zero‐valent iron. Ground water mounding on the upgradient side of the PRB resulted in a tenfold increase in the hydraulic gradient and ground water velocity through the gates compared to areas of the aquifer unaffected by the PRB. Water balance calculations for April 1997 indicate that about 75 % of the ground water moving toward the PRB from upgradient areas moved through the gates. The rest of the water either accumulated on the upgradient side of the PRB or bypassed the PRB. Chemical data from monitoring wells screened down‐gradient, beneath, and at the ends of the PRB indicate that contaminants had not bypassed the PRB, except in a few isolated areas. Greater than 99 % of the CAH mass entering the gates was retained by the iron. Fifty‐one percent of the CAH carbon entering one gate was accounted for in dissolved C 1 and C 2 hydrocarbons, primarily ethane and ethene, which indicates that CAHs may adsorb to the iron prior to being dehalogenated. Treated water exiting the gates displaced contaminated ground water at a distance of at least 3 m downgradient from the PRB by the end of 1997. Measurements of dissolved inorganic ions in one gate indicate that calcite and siderite precipitation in the gate could reduce gate porosity by about 0.35 % per year. Results from this study indicate that funnel and gate systems containing zero‐valent iron can effectively treat ground water contaminated with CAHs. However, the hydrologic impacts of the PRB on the flow system need to be fully understood to prevent contaminants from bypassing the PRB.

Colorado↗
USGS2002

Lead isotopic analyses of selected soil samples from the USEPA Vasquez Blvd.-I-70 study area, Denver, CO

Large amounts of arsenic contamination, in excess of 2000 ppm, have been found in some residential surface soils in northern Denver, Colorado (USEPA, 1999). Associated with the arsenic are elevated levels of metals such as lead, cadmium and mercury. Potential sources of this contamination include waste from smelters in the area and commercial herbicide containing arsenic trioxide and lead arsenate (USEPA, 1999). As a part of the U.S. Environmental Protection Agency’s Vasquez Boulevard-I-70 Project (VBI70 project; USEPA, 1999), lead isotopic analyses of selected soil samples, smelter waste, and a commercial herbicide and a commercial lead arsenate pesticide have been performed in order to constrain the possible sources of elevated lead, and by proxy arsenic, found in these residential soils. The isotopes of lead can be used as a natural tracer in determining sources of contaminants in soils and stream sediments (e.g. Church and others, 1997; Fey and others, 1999; Unruh and others, 2000). The element lead (Pb) consists of four naturally occurring and stable isotopes, 204Pb, 206Pb, 207Pb, and 208Pb. Three of these, 206Pb, 207Pb, and 208Pb are radiogenic decay products of naturally occurring 238U, 235U, and 232Th, respectively. Owing to variations among the U/Pb and Th/Pb elemental abundance ratios among different types of geologic materials, variations in the relative abundances of the Pb isotopes are produced among different materials during geologic time. In order for the Pb isotope method to be useful for determining possible contaminant sources, two important criteria must be met (e.g. Church and others 1997): (1) It must be possible to obtain and measure the Pb isotopic compositions in all potential contaminant sources and in uncontaminated material and (2) the Pb isotopic compositions of the potential contaminant sources must be distinctly different from one another and from uncontaminated background. Variations among the Pb isotopic ratios in selected samples can be correlated with potential sources of Pb with known isotopic compositions in order to determine the relative contribution of Pb from a specific source to the sample. The purpose of this study is to use Pb isotopic data obtained from a selected subset of samples to determine the Pb isotopic signatures of uncontaminated soils as well as those of potential sources of contamination. The data will eventually be used in conjunction with other geochemical data to help determine which source or sources of contamination are most likely responsible for the elevated arsenic levels in the residential soils.

Colorado↗
USGS2000

Magnetic and GPR surveys of a former munitions foundry site at the Denver Federal Center

We made magnetometer and ground penetrating radar (GPR) surveys over part of the foundation of a World War II-era foundry located on the Denver Federal Center. The site contains a number of highly magnetic source bodies, concrete foundation walls, and underground openings, buried under a clay cap. The cap is several feet thick and has a conductivity of about 35 mS/m, making the features underneath it a poor target for conventional GPR. Indeed, the raw data look unlike typical GPR data, but rather show reverberation (?) bands under sidewalks and other shallow buried sources. Using a newly-written computer package, we made plan maps of the GPR response at different time slices. The sliced GPR data did not outline buried foundry foundations, as we had hoped it might. The resulting plan maps of the sliced data show sidewalks and other blobby features, some of which correspond to magnetometer highs.

Colorado↗
USGS1999

Health status and relative exposure of mule deer and white-tailed deer to soil contaminants at the rocky mountain arsenal

We evaluated the health of 18 radio-collared deer [13 mule deer ( Odocoileus hemionus ) and 5 white-tailed deer ( O. virginianus )] from the Rocky Mountain Arsenal, near Denver, Colorado, USA, a Superfund site contaminated with a variety of materials, including organochlorine pesticides, metals, and nerve gas production by-products. Radio-collared deer were tracked for 1 to 3 years (1989–1992) to identify relative exposure to contaminants based on telemetry locations plotted on grid maps depicting known soil contaminant concentrations. At the end of the study, all animals were in fair or good body condition at the time of necropsy. Mean ages of mule deer and white-tailed deer were 7.4 (range 4–12) and 10.6 years (range 5–17), respectively. At necropsy, tissues were collected from the deer for serology, histopathology, and analysis for eight chlorinated hydrocarbons and two metals. Detectable residues of mercury were found in the kidneys of 10 deer (range 0.055–0.096 μg/g), dieldrin was found in fat ( n = 9) (range 0.02–0.72 μg/g), liver ( n = 4) (range 0.017–0.12 μg/g), and brain ( n = 1, 0.018 μg/g), and DDE was found in the muscle of one animal (0.02 μg/g). Relative exposure estimates derived from telemetry and soil contamination data were correlated with tissue levels of dieldrin ( p < 0.001) and mercury ( p = 0.05). Two mule deer had severe testicular atrophy, and one of these animals also had antler deformities. The prevalence of antibodies against epizootic hemorrhagic disease serotype 2 was 85%.

Colorado↗
USGS1998

Science for watershed decisions on abandoned mine lands; review of preliminary results, Denver, Colorado, February 4-5, 1998

From the Preface: There are thousands of abandoned or inactive mines on or adjacent to public lands administered by the U.S. Forest Service, Bureau of Land Management, and National Park Service. Mine wastes from many of these abandoned mines adversely affect resources on public lands. In 1995, an interdepartmental work group within the Federal government developed a strategy to address remediation of the many abandoned mines on public lands. This strategy is based on using a watershed approach to address the abandoned mine lands (AML) problem. The USGS, working closely with the Federal land-management agencies (FLMAs), is key for the success of this watershed approach. In support of this watershed approach, the USGS developed an AML Initiative with pilot studies in the Boulder River in Montana and the Animas River in Colorado. The goal of these studies is to design and implement a reliable strategy that will supply the scientific information to the FLMAs so that land managers can develop efficient and cost-effective remediation of AML. The symposium 'Science for Watershed Decisions on Abandoned Mine Lands: Review of Preliminary Results' held in Denver, Colorado, on February 4-5, 1998, provided the FLMAs a first look at the techniques, data, and interpretations being generated by the USGS pilot studies. This multidisciplined effort already is proving very valuable to land managers in making science-based AML cleanup decisions and will continue to be of increasing value as additional and more complete information is obtained. Ongoing interaction between scientists and land managers is essential to insure the efficient continuation and success of AML cleanup efforts.

Colorado↗
USGS1992

Effects of weather and soil characteristics on temporal variations in soil-gas radon concentrations

Concentrations of radon-222 in soil gas measured over about 1 yr at a monitoring site in Denver, Colorado, vary by as much as an order of magnitude seasonally and as much as severalfold in response to changes in weather. The primary weather factors that influence soil-gas radon concentrations are precipitation and barometric pressure. Soil characteristics are important in determining the magnitude and extent of the soil’s response to weather changes. The soil at the study site is clay rich and develops desiccation cracks upon drying that increase the soil’s permeability and enhance gas transport and removal of radon from the soil. A capping effect caused by frozen or unfrozen soil moisture is a primary mechanism for preventing radon loss to the atmosphere.

Colorado↗
USGS1988

QED

Explore the source record for details and available documents.

Colorado↗
USGS1987

Water-quality assessment of Arvada Reservoir, Denver metropolitan area, Colorado

Water quality data were collected from Arvada Reservoir, Colorado, and from its major inflows, Ralston Creek and Croke Canal, to assess the water quality of the reservoir, to evaluate the effect of water from various sources on the reservoir, and to estimate the trophic state of the reservoir. Data were collected at five sites in Arvada Reservoir, one site in Ralston Creek, and two sites in Croke Canal. The study began in June 1983 (just before filling in May 1984) and continued through September 1985. The reservoir was thermally stratified on most sampling dates from April through September. Dissolved-oxygen concentrations ranged from 0 to 12.0 milligrams per liter, and the reservoir was anaerobic below the 10-meter depth during most of the summer. Secchi-disk-depth measurements ranged from 0.9 to 5.5 meters and generally increased during the study period, possibly because of decreases in nonalgal turbidity after the reservoir was filled. Water from the reservoir generally is of suitable quality for a raw-water-supply source and for maintenance of aquatic life. Total-nitrogen and total-phosphorus concentrations were small, and both were growth-limiting factors in the reservoir. The phytoplankton community was diverse, and the most dominant taxa were diatoms. Phytoplankton densities ranged from 1,400 to 29,000 cells per millimeter, and chlorophyll alpha concentrations ranged from 0.0 to 20.4 micrograms per liter. (USGS)

Colorado↗
USGS1985

Hydraulic gradient control for groundwater contaminant removal

The Rocky Mountain Arsenal near Denver, Colorado, U.S.A., is used as a realistic setting for a hypothetical test of a procedure that plans the hydraulic stabilization and removal of a groundwater contaminant plume. A two-stage planning procedure successfully selects the best wells and their optimal pumping/recharge schedules to contain the plume while a well or system of wells within the plume removes the contaminated water. In stage I, a combined groundwater flow and solute transport model is used to simulate contaminant removal under an assumed velocity field. The result is the approximated plume boundary location as a function of time. In stage II, a linear program, which includes a groundwater flow model as part of the set of constraints, determines the optimal well selection and their optimal pumping/recharge schedules by minimizing total pumping and recharge. The simulation—management model eliminates wells far from the plume perimeter and activates wells near the perimeter as the plume decreases in size. This successfully stablizes the hydraulic gradient during aquifer cleanup.

Colorado↗
USGS1985

A summary of urban runoff studies in the Denver Metropolitan area, Colorado

The Denver metropolitan area has been the subject of urban-runoff studies for several years. The first studies, started in about 1968, usually were concerned only with the quantity of urban runoff. In 1974, studies were begun that included both quantity and quality of urban runoff. In 1979, Denver was selected as one of the cities to be included in the Nationwide Urban Runoff Program. The Denver study was called the Denver Regional Urban Runoff Program and was a cooperative study between the Denver Regional Council of Governments and the U.S. Geological Survey. This report presents the major conclusions of the pre-Denver Regional Urban Runoff Program studies and a summary of the various elements of the Denver Regional Urban Runoff Program. The report summarizes and references urban-runoff studies in the Denver metropolitan area and is a reference guide for planners and other persons interested in urban runoff.

Colorado↗
USGS1983

Well yields and chemical quality of water from water-table aquifers in the greater Denver area, Front Range urban corridor, Colorado

Knowledge of the well yields and chemical quality of water from water-table aquifers is useful to State and local officials in making decisions on land use and in locating water supplies in the rapidly urbanizing greater Denver are. This report presents the results of a 2-year investigation to obtain this knowledge and to relate the results to urban planning in the greater Denver area. The report is one of a series of geologic and hydrologic reports prepared by the U.S. Geological Survey to demonstrate the usefulness of Earth-science information in urban planning.

Colorado↗
USGS1983

Depth to the water table (1976-1977) in the Greater Denver area, Front Range urban corridor, Colorado

Knowledge of the depth to the water table is useful to State and local officials in making decisions on land use in the rapidly urbanizing greater Denver are. This report presents the results of a 2-year investigation to determine the depth to the water table, water-table fluctuations and trends, and to relate the results of the investigation to urban planning in the greater Denver area. The report is one of a series of geologic and hydrologic reports prepared by the U.S. Geological Survey to demonstrate the usefulness of Earth-science information in urban planning.

Colorado↗
USGS1979

Vegetation in the greater Denver area, Front Range urban corridor, Colorado

Vegetation is one of our most valuable renewable resources; it is the primary producer of organic matter on which all nongreen organisms are dependent for energy, construction materials, aesthetic enjoyment, and other necessities of life. In order to secure the greatest possible returns from the utilization of the different types of vegetation, people need to know what species are present, the ecological processes in which they are involved, and the ways in which they are arranged in the landscape. This vegetation map is designed to help persons in a wide variety of activities to secure that information.

Colorado↗