Geology and water resources of the Harney Basin region, Oregon
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Water Supply Paper↗
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Geologic framework for the national assessment of carbon dioxide storage resources: Columbia Basin of Oregon, Washington, and Idaho, and the Western Oregon-Washington basins
The 2007 Energy Independence and Security Act (Public Law 110–140) directs the U.S. Geological Survey (USGS) to conduct a national assessment of potential geologic storage resources for carbon dioxide (CO 2 ). The methodology used by the USGS for the national CO 2 assessment follows that of previous USGS work. The methodology is non-economic and intended to be used at regional to subbasinal scales. This report identifies and contains geologic descriptions of three storage assessment units (SAUs) in Eocene and Oligocene sedimentary rocks within the Columbia, Puget, Willapa, Astoria, Nehalem, and Willamette Basins of Oregon, Washington, and Idaho, and focuses on the characteristics, specified in the methodology, that influence the potential CO 2 storage resource in those SAUs. Specific descriptions of the SAU boundaries as well as their sealing and reservoir units are included. Properties for each SAU, such as depth to top, gross thickness, porosity, permeability, groundwater quality, and structural reservoir traps, are provided to illustrate geologic factors critical to the assessment. The designated sealing unit in the Columbia Basin is tentatively chosen to be the ubiquitous and thick Miocene Columbia River Basalt Group. As a result of uncertainties regarding the seal integrity of the Columbia River Basalt Group, the SAUs were not quantitatively assessed. Figures in this report show SAU boundaries and cell maps of well penetrations through sealing units into the top of the storage formations. The cell maps show the number of penetrating wells within one square mile and are derived from interpretations of incompletely attributed well data, a digital compilation that is known not to include all drilling. The USGS does not expect to know the location of all wells and cannot guarantee the amount of drilling through specific formations in any given cell shown on the cell maps.
Idaho, Oregon, Washington↗
Database for the Geologic Map of Upper Eocene to Holocene Volcanic and Related Rocks of the Cascade Range, Oregon
Since 1979, Earth scientists of the Geothermal Research Program of the U.S. Geological Survey have carried out multidisciplinary research in the Cascade Range. The goal of this research is to understand the geology, tectonics, and hydrology of the Cascades in order to characterize and quantify geothermal resource potential. A major goal of the program is compilation of a comprehensive geologic map of the entire Cascade Range that incorporates modern field studies and that has a unified and internally consistent explanation. This map is one of three in a series that shows Cascade Range geology by fitting published and unpublished mapping into a province-wide scheme of rock units distinguished by composition and age; map sheets of the Cascade Range in Washington (Smith, 1993) and California will complete the series. The complete series forms a guide to exploration and evaluation of the geothermal resources of the Cascade Range and will be useful for studies of volcano hazards, volcanology, and tectonics. This digital release contains all the information used to produce the geologic map published as U.S. Geological Survey Geologic Investigations Series I-2569 (Sherrod and Smith, 2000). The main component of this digital release is a geologic map database prepared using ArcInfo GIS. This release also contains files to view or print the geologic map and accompanying descriptive pamphlet from I-2569.
Data Series↗
Estimating landslide losses - preliminary results of a seven-State pilot project
Introduction: In 2001, the U.S. Geological Survey Landslide Hazards Program provided funding for seven State geological surveys to report on the status of landslide investigation strategies in each of their States, and to suggest improved ways to approach the tracking of landslides, their effects, losses associated with the landslides, and hazard mitigation strategies. Each State was to provide a draft report suggesting innovative ways to track landslides, and to participate in subsequent workshops. A workshop was convened in June 2003 in Lincoln, Neb., to discuss the results and future strategies on how best to incorporate the seven pilot projects into one methodology that all of the 50 States could adopt. The seven individual reports produced by the State surveys are published here to put forth a forum for discussion of the varying methods of tracking landslides. The goal is to eventually adopt a single, universally applied methodology to track landslides that will provide a consistent framework for collecting data on landslide damage and economic impact. Participating States include: California (James Davis, Jack McMillan); Kentucky (Jim Cobb, John Kiefer, John Rockaway); Nebraska (Mark Kuzila, Duane Eversoll); Ohio (Thomas Berg, Jon Rockaway), Oregon (John Beaulieu, Yumei Wang, Renee Summers, Jon Hofmeister); Pennsylvania (Jay Parrish, Helen Delano); Utah (Richard Allis, Francis Ashland). The USGS personnel involved in the planning and meeting facilitation are Paula Gori, Peter Lyttle, and John Pallister. The general USGS strategy to address landslide loss reduction was developed with input from State geological surveys, the engineering-geology consulting community, and academic investigators. The strategy was reviewed by the National Research Council, 2004), is summarized in USGS Circular 1244 (Spiker and Gori, 2003) and is endorsed by the AASG. This pilot study, conducted by seven State geological surveys, examines the feasibility of collecting accurate and reliable information on economic losses associated with landslides. Each State survey examined the availability, distribution, and inherent uncertainties of economic loss data in their study areas. Their results provide the basis for identifying the most fruitful methods of collecting landslide loss data nationally, using methods that are consistent and provide common goals. These results can enhance and establish the future directions of scientific investigation priorities by convincingly documenting landslide risks and consequences that are universal throughout the 50 States. This report is organized as follows: A general summary of the pilot project history, goals, and preliminary conclusions from the Lincoln, Neb. workshop are presented first. Internet links are then provided for each State report, which appear on the internet in PDF format and which have been placed at the end of this open-file report. A reference section follows the reports, and, lastly, an Appendix of categories of landslide loss and sources of loss information is included for the reader's information. Please note: The Oregon Geological Survey has also submitted a preliminary report on indirect loss estimation methodology, which is also linked with the others. Each State report is unique and presented in the form in which it was submitted, having been independently peer reviewed by each respective State survey. As such, no universal 'style' or format has been adopted as there have been no decisions on which inventory methods will be recommended to the 50 states, as of this writing. The reports are presented here as information for decision makers, and for the record; although several reports provide recommendations on inventory methods that could be adopted nationwide, currently no decisions have been made on adopting a uniform methodology for the States.
Open-File Report↗
Large-scale fractures related to inception of the Yellowstone hotspot
During middle Miocene time, western North America was subject to flood-basalt volcanism, dike-swarm injection, and broad-scale fracturing and folding of the crust. We propose a simple model to account for these events and for a regional pattern of geologic and geophysical features. Aeromagnetic maps reveal some of the most important elements of this pattern, which are several narrow, arcuate anomalies, here referred to as the Northern Nevada rifts. These rifts extend hundreds of kilometers across Nevada and are likely caused by highly magnetic, middle Miocene mafic dikes. With the aid of filtering techniques, the anomalies can be traced into Oregon. Together with other geologic features, such as fold axes, dike swarms, and faults, they produce a spoke-like pattern fanning over 220° of arc that converges toward a point near the Oregon-Idaho border (lat ∼44°N ). A possible cause for this pattern is a point source of stress at the base of the crust related to the formation of the Yellowstone hotspot. The spoke-like pattern, however, does not persist at large distances from the emerging hotspot; several hundred kilometers to the south, the Northern Nevada rifts deviate significantly ( >30° ) from a radial trend. We show that a simple model-imposing a point source of stress at the base of the crust and a regional stress field aligned with the presumed middle Miocene stress direction-fits the observed fracture pattern. It thus accounts for both the radial pattern present near the nascent hotspot and the far-field pattern due to regional stresses.
Wyoming↗
A method for characterizing late-season low-flow regime in the upper Grand Ronde River Basin, Oregon
This report describes a method for estimating ecologically relevant low-flow metrics that quantify late‑season streamflow regime for ungaged sites in the upper Grande Ronde River Basin, Oregon. The analysis presented here focuses on sites sampled by the Columbia River Inter‑Tribal Fish Commission as part of their efforts to monitor habitat restoration to benefit spring Chinook salmon recovery in the basin. Streamflow data were provided by the U.S. Geological Survey and the Oregon Water Resources Department. Specific guidance was provided for selection of streamgages, development of probabilistic frequency distributions for annual 7-day low-flow events, and regionalization of the frequency curves based on multivariate analysis of watershed characteristics. Evaluation of the uncertainty associated with the various components of this protocol indicates that the results are reliable for the intended purpose of hydrologic classification to support ecological analysis of factors contributing to juvenile salmon success. They should not be considered suitable for more standard water-resource evaluations that require greater precision, especially those focused on management and forecasting of extreme low-flow conditions.
Oregon↗
Preliminary Results of Subsurface Exploration and Monitoring at the Johnson Creek Landslide, Lincoln County, Oregon
The Johnson Creek landslide is a translational, primarily bedrock landslide located along the Oregon coast about 5 km north of Newport. The landslide has damaged U.S. Highway 101 many times since construction of the highway and at least two geological and geotechnical investigations of the landslide have been performed by Oregon State agencies. In cooperation with the Oregon Department of Geology and Mineral Industries and the Oregon Department of Transportation, the U.S. Geological Survey upgraded landslide monitoring systems and installed additional monitoring devices at the landslide beginning in 2004. Monitoring devices at the landslide measured landslide displacement, rainfall, air temperature, shallow soil-water content, and ground-water temperature and pressure. The devices were connected to automatic dataloggers and read at one-hour and, more recently, 15-minute intervals. Monitoring results were periodically downloaded from the dataloggers using cellular telemetry. The purposes of this report are to describe and present preliminary monitoring data from November 19, 2004, to March 31, 2007.
Open-File Report↗
Groundwater simulation and management models for the upper Klamath Basin, Oregon and California
The upper Klamath Basin encompasses about 8,000 square miles, extending from the Cascade Range east to the Basin and Range geologic province in south-central Oregon and northern California. The geography of the basin is dominated by forested volcanic uplands separated by broad interior basins. Most of the interior basins once held broad shallow lakes and extensive wetlands, but most of these areas have been drained or otherwise modified and are now cultivated. Major parts of the interior basins are managed as wildlife refuges, primarily for migratory waterfowl. The permeable volcanic bedrock of the upper Klamath Basin hosts a substantial regional groundwater system that provides much of the flow to major streams and lakes that, in turn, provide water for wildlife habitat and are the principal source of irrigation water for the basin's agricultural economy. Increased allocation of surface water for endangered species in the past decade has resulted in increased groundwater pumping and growing interest in the use of groundwater for irrigation. The potential effects of increased groundwater pumping on groundwater levels and discharge to springs and streams has caused concern among groundwater users, wildlife and Tribal interests, and State and Federal resource managers. To provide information on the potential impacts of increased groundwater development and to aid in the development of a groundwater management strategy, the U.S. Geological Survey, in collaboration with the Oregon Water Resources Department and the Bureau of Reclamation, has developed a groundwater model that can simulate the response of the hydrologic system to these new stresses. The groundwater model was developed using the U.S. Geological Survey MODFLOW finite-difference modeling code and calibrated using inverse methods to transient conditions from 1989 through 2004 with quarterly stress periods. Groundwater recharge and agricultural and municipal pumping are specified for each stress period. All major streams and most major tributaries for which a substantial part of the flow comes from groundwater discharge are included in the model. Groundwater discharge to agricultural drains, evapotranspiration from aquifers in areas of shallow groundwater, and groundwater flow to and from adjacent basins also are simulated in key areas. The model has the capability to calculate the effects of pumping and other external stresses on groundwater levels, discharge to streams, and other boundary fluxes, such as discharge to drains. Historical data indicate that the groundwater system in the upper Klamath Basin fluctuates in response to decadal climate cycles, with groundwater levels and spring flows rising and declining in response to wet and dry periods. Data also show that groundwater levels fluctuate seasonally and interannually in response to groundwater pumping. The most prominent response is to the marked increase in groundwater pumping starting in 2001. The calibrated model is able to simulate observed decadal-scale climate-driven fluctuations in the groundwater system as well as observed shorter-term pumping-related fluctuations. Example model simulations show that the timing and location of the effects of groundwater pumping vary markedly depending on the pumping location. Pumping from wells close (within a few miles) to groundwater discharge features, such as springs, drains, and certain streams, can affect those features within weeks or months of the onset of pumping, and the impacts can be essentially fully manifested in several years. Simulations indicate that seasonal variations in pumping rates are buffered by the groundwater system, and peak impacts are closer to mean annual pumping rates than to instantaneous rates. Thus, pumping effects are, to a large degree, spread out over the entire year. When pumping locations are distant (more than several miles) from discharge features, the effects take many years or decades to fully impact those features, and much of the pumped water comes from groundwater storage over a broad geographic area even after two decades. Moreover, because the effects are spread out over a broad area, the impacts to individual features are much smaller than in the case of nearby pumping. Simulations show that the discharge features most affected by pumping in the area of the Bureau of Reclamation's Klamath Irrigation Project are agricultural drains, and impacts to other surface-water features are small in comparison. A groundwater management model was developed that uses techniques of constrained optimization along with the groundwater flow model to identify the optimal strategy to meet water user needs while not violating defined constraints on impacts to groundwater levels and streamflows. The coupled groundwater simulation-optimization models were formulated to help identify strategies to meet water demand in the upper Klamath Basin. The models maximize groundwater pumping while simultaneously keeping the detrimental impacts of pumping on groundwater levels and groundwater discharge within prescribed limits. Total groundwater withdrawals were calculated under alternative constraints for drawdown, reductions in groundwater discharge to surface water, and water demand to understand the potential benefits and limitations for groundwater development in the upper Klamath Basin. The simulation-optimization model for the upper Klamath Basin provides an improved understanding of how the groundwater and surface-water system responds to sustained groundwater pumping within the Bureau of Reclamation's Klamath Project. Optimization model results demonstrate that a certain amount of supplemental groundwater pumping can occur without exceeding defined limits on drawdown and stream capture. The results of the different applications of the model demonstrate the importance of identifying constraint limits in order to better define the amount and distribution of groundwater withdrawal that is sustainable.
Oregon;California↗
Noble gas isotopes in mineral springs and wells within the Cascadia forearc, Washington, Oregon, and California
Introduction This U.S. Geological Survey report presents laboratory analyses along with field notes for an exploratory study to document the relative abundance of noble gases in mineral springs and water wells within the Cascadia forearc of Washington, Oregon, and California (fig. 1). This report describes 14 samples collected in 2014 and 2015 and complements a previous report that describes 9 samples collected in 2012 and 2013 (McCrory and others, 2014b). Estimates of the depth to the underlying Juan de Fuca oceanic plate beneath sample sites are derived from the McCrory and others (2012) slab model. Some of the springs have been previously sampled for chemical analyses (Mariner and others, 2006), but none of the springs or wells currently has publicly available noble gas data. The helium and neon isotope values and ratios presented below are used to determine the sources and mixing history of these mineral and well waters (for example, McCrory and others, 2016).
California, Oregon, Washington↗
Evaluation of Approaches for Managing Nitrate Loading from On-Site Wastewater Systems near La Pine, Oregon
This report presents the results of a study by the U.S. Geological Survey, done in cooperation with the Oregon Department of Environmental Quality and Deschutes County, to develop a better understanding of the effects of nitrogen from on-site wastewater disposal systems on the quality of ground water near La Pine in southern Deschutes County and northern Klamath County, Oregon. Simulation models were used to test the conceptual understanding of the system and were coupled with optimization methods to develop the Nitrate Loading Management Model, a decision-support tool that can be used to efficiently evaluate alternative approaches for managing nitrate loading from on-site wastewater systems. The conceptual model of the system is based on geologic, hydrologic, and geochemical data collected for this study, as well as previous hydrogeologic and water quality studies and field testing of on-site wastewater systems in the area by other agencies. On-site wastewater systems are the only significant source of anthropogenic nitrogen to shallow ground water in the study area. Between 1960 and 2005 estimated nitrate loading from on-site wastewater systems increased from 3,900 to 91,000 pounds of nitrogen per year. When all remaining lots are developed (in 2019 at current building rates), nitrate loading is projected to reach nearly 150,000 pounds of nitrogen per year. Low recharge rates (2-3 inches per year) and ground-water flow velocities generally have limited the extent of nitrate occurrence to discrete plumes within 20-30 feet of the water table; however, hydraulic-gradient and age data indicate that, given sufficient time and additional loading, nitrate will migrate to depths where many domestic wells currently obtain water. In 2000, nitrate concentrations greater than 4 milligrams nitrogen per liter (mg N/L) were detected in 10 percent of domestic wells sampled by Oregon Department of Environmental Quality. Numerical simulation models were constructed at transect (2.4 square miles) and study-area (247 square miles) scales to test the conceptual model and evaluate processes controlling nitrate concentrations in ground water and potential ground-water discharge of nitrate to streams. Simulation of water-quality conditions for a projected future build-out (base) scenario in which all existing lots are developed using conventional on-site wastewater systems indicates that, at equilibrium, average nitrate concentrations near the water table will exceed 10 mg N/L over areas totaling 9,400 acres. Other scenarios were simulated where future nitrate loading was reduced using advanced treatment on-site systems and a development transfer program. Seven other scenarios were simulated with total nitrate loading reductions ranging from 15 to 94 percent; simulated reductions in the area where average nitrate concentrations near the water table exceed 10 mg N/L range from 22 to 99 percent at equilibrium. Simulations also show that the ground-water system responds slowly to changes in nitrate loading due to low recharge rates and ground-water flow velocity. Consequently, reductions in nitrate loading will not immediately reduce average nitrate concentrations and the average concentration in the aquifer will continue to increase for 25-50 years depending on the level and timing of loading reduction. The capacity of the ground-water system to receive on-site wastewater system effluent, which is related to the density of homes, presence of upgradient residential development, ground-water recharge rate, ground-water flow velocity, and thickness of the oxic part of the aquifer, varies within the study area. Optimization capability was added to the study-area simulation model and the combined simulation-optimization model was used to evaluate alternative approaches to management of nitrate loading from on-site wastewater systems to the shallow alluvial aquifer. The Nitrate Loading Management Model (NLMM) was formulated to find the minimum red
Scientific Investigations Report↗
Geologic implications of Paleozoic and Mesozoic paleontology and biostratigraphy, Blue Mountains province, Oregon and Idaho
This volume contains, besides the present review, seven papers on the biostratigraphy of pre-Tertiary rocks in the Blue Mountains province. Geologic implications of the faunal data are discussed in the context of terrane analyses. Most of the authors agree that the pre-Tertiary rocks of this province were formed in a complex island arc within a low-latitude faunal realm and subsequently moved northward and accreted to the North American continent. The use of different terrane names for parts of the Blue Mountains province by different authors may lead to some confusion. We suggest that future authors use the term "Blue Mountains island arc" for the pre-Tertiary province and, if there is a need for subdivision, that they use the terrane names proposed by Silberling and others (1984).
Idaho;Oregon;Washington↗
Tsunami Preparedness in Oregon (video)
Tsunamis are a constant threat to the coasts of our world. Although tsunamis are infrequent along the West coast of the United States, it is possible and necessary to prepare for potential tsunami hazards to minimize loss of life and property. Community awareness programs are important, as they strive to create an informed society by providing education and training. This video about tsunami preparedness in Oregon distinguishes between a local tsunami and a distant event and focus on the specific needs of this region. It offers guidelines for correct tsunami response and community preparedness from local emergency managers, first-responders, and leading experts on tsunami hazards and warnings, who have been working on ways of making the tsunami affected regions safer for the people and communities on a long-term basis. This video was produced by the US Geological Survey (USGS) in cooperation with Oregon Department of Geology and Mineral Industries (DOGAMI).
General Information Product↗
Database for the geologic map of Newberry Volcano, Deschutes, Klamath, and Lake Counties, Oregon
Newberry Volcano, one of the largest Quaternary volcanoes in the conterminous United States, is a broad shield-shaped volcano measuring 60 km north-south by 30 km east-west with a maximum elevation of more than 2 km. Newberry Volcano is the product of deposits from thousands of eruptions, including at least 25 in the past approximately 12,000 years (Holocene Epoch). Newberry Volcano has erupted as recently as 1,300 years ago, but isotopic ages indicate that the volcano began its growth as early as 0.6 million years ago. Such a long eruptive history and recent activity suggest that Newberry Volcano is likely to erupt in the future. This geologic map database of Newberry Volcano distinguishes rocks and deposits based on their composition, age, and lithology.
Oregon↗
Database for the geologic map of upper Eocene to Holocene volcanic and related rocks in the Cascade Range, Washington
This geospatial database for a geologic map of the Cascades Range in Washington state is one of a series of maps that shows Cascade Range geology by fitting published and unpublished mapping into a province-wide scheme of lithostratigraphic units. Geologic maps of the Eocene to Holocene Cascade Range in California and Oregon complete the series, providing a comprehensive geologic map of the entire Cascade Range that incorporates modern field studies and that has a unified and internally consistent explanantion. The complete series will be useful for regional studies of volcanic hazards, volcanology, and tectonics. Originally a project supported by the Geothermal Research Program of the U.S. Geological Survey, the maps emphasize Quaternary volcanic rocks, because large igneous-related hydrothermal systems that have high temperatures are associated with Quaternary volcanic fields. Rocks older than a few million years are also included on the maps as they help to unravel geologic puzzles of the present-day Cascade Range. The deeply eroded older volcanoes found in the Western Cascades physiographic subprovince are analogues of today's snow-covered shield volcanoes and stratovolcanoes. The fossil hydrothermal systems of the Eocene to Pliocene vents now exposed provide clues to processes active today beneath the Pleistocene and Holocene volcanic peaks along the present-day crest of the Cascade Range. Study of these older rocks can aid in developing models of geothermal systems. These rocks also give insight into the origins of volcanic-hosted mineral deposits and even to future volcanic hazards. This digital database contains information used to produce the geologic map published as Sheet 1 in U.S. Geological Survey Miscellaneous Investigations Series Map I-2005. (Sheet 2 of Map I-2005 shows sources of geologic data used in the compilation and is available separately). Sheet 1 of Map I-2005 shows the distribution and relations of volcanic and related rock units in the Cascade Range of Washington at a scale of 1:500,000. This digital release is produced from stable materials originally compiled at 1:250,000 scale that were used to publish Sheet 1. The database therefore contains more detailed geologic information than is portrayed on Sheet 1. This is most noticeable in the database as expanded polygons of surficial units and the presence of additional strands of concealed faults. No stable compilation materials exist for Sheet 1 at 1:500,000 scale. The main component of this digital release is a spatial database prepared using geographic information systems (GIS) applications. This release also contains links to files to view or print the map sheet, main report text, and accompanying mapping reference sheet from Map I-2005. For more information on volcanoes in the Cascade Range in Washington, Oregon, or California, please refer to the U.S. Geological Survey Volcano Hazards Program website.
Washington↗
Great Basin geoscience data base
This CD-ROM serves as the archive for 73 digital GIS data set for the Great Basin. The data sets cover Nevada, eastern California, southeastern Oregon, southern Idaho, and western Utah. Some of the data sets are incomplete for the total area. On the CD-ROM, the data are provided in three formats, a prototype Federal Data Exchange standard format, the ESRI PC ARCVIEW1 format for viewing the data, and the ESRI ARC/INFO export format. Extensive documentation is provided to describe the data, the sources, and data enhancements. The following data are provided. One group of coverages comes primarily from 1:2,000,000-scale National Atlas data and can be assembled for use as base maps. These various forms of topographic information. In addition, public land system data sets are provided from the 1:2,500,000-scale Geologic Map of the United States and 1:500,000-scale geologic maps of Nevada, Oregon, and Utah. Geochemical data from the National Uranium Resource Evaluation (NURE) program are provided for most of the Great Basin. Geophysical data are provided for most of the Great Basin, typically gridded data with a spacing of 1 km. The geophysical data sets include aeromagnetics, gravity, radiometric data, and several derivative products. The thematic data sets include geochronology, calderas, pluvial lakes, tectonic extension domains, distribution of pre-Cenozoic terranes, limonite anomalies, Landsat linear features, mineral sites, and Bureau of Land Management exploration and mining permits.
Data Series↗
The effects of calcium magnesium acetate (CMA) deicing material on the water quality of Bear Creek, Clackamas County, Oregon, 1999
This report presents the results of a study by the U.S. Geological Survey, done in cooperation with the Oregon Department of Transportation (ODOT), to evaluate the effects of the highway deicing material, calcium magnesium acetate (CMA), on the water quality of Bear Creek, in the Cascade Range of Oregon. ODOT began using CMA (an alternative deicer that has fewer adverse environmental effects than road salt) in the mid-1990s and began this study with the USGS to ensure that there were no unexpected effects on the water quality of Bear Creek. Streamflow, precipitation, dissolved oxygen, pH, specific conductance, and water temperature were measured continuously through the 1998?99 winter. There was no measurable effect of the application of CMA to Highway 26 on the biochemical oxygen demand (BOD), calcium concentration, or magnesium concentration of Bear Creek and its tributaries. BOD was small in all of the water samples, some of which were collected before CMA application, and some of which were collected after application. Five-day BOD values ranged from 0.1 milligrams per liter to 1.5 milligrams per liter, and 20-day BOD values ranged from 0.2 milligrams per liter to 2.0 milligrams per liter. Dissolved copper concentrations in a small tributary ditch on the north side of Highway 26 exceeded the U.S. Environmental Protection Agency aquatic life criteria on three occasions. These exceedances were probably not caused by the application of CMA because (1) one of the samples was a background sample (no recent CMA application), and (2) dissolved copper was not detected in Bear Creek water samples to which CMA was added during laboratory experiments.
Oregon↗
Geologic map of the Washougal quadrangle, Clark County, Washington, and Multnomah County, Oregon
The Washougal 7.5’ quadrangle spans the boundary between the Portland Basin and the Columbia River Gorge, approximately 30 km east of Portland, Oregon. The map area contains the westernmost portion of the Columbia River Gorge National Scenic area as well as the rapidly growing areas surrounding the Clark County, Washington, cities of Camas and Washougal. The Columbia River transects the map area, and two major tributaries, the Washougal River in Washington and the Sandy River in Oregon, also flow through the quadrangle. The Columbia, Washougal, and Sandy Rivers have all cut deep valleys through hilly uplands, exposing Oligocene volcanic bedrock in the north part of the map area and lava flows of the Miocene Columbia River Basalt Group in the western Columbia River Gorge. Elsewhere in the map area, these older rocks are buried beneath weakly consolidated to well-consolidated Neogene and younger basin-fill sedimentary rocks and Quaternary volcanic and sedimentary deposits. The Portland Basin is part of the Coastal Lowland that separates the Cascade Range from the Oregon Coast Range. The basin has been interpreted as a pull-apart basin located in the releasing stepover between two en echelon, northwest-striking, right-lateral fault zones. These fault zones are thought to reflect regional transpression, transtension, and dextral shear within the forearc in response to oblique subduction of the Pacific plate along the Cascadia Subduction Zone. The southwestern margin of the Portland Basin is a well-defined topographic break along the base of the Tualatin Mountains, an asymmetric anticlinal ridge that is bounded on its northeast flank by the Portland Hills Fault Zone, which is probably an active structure. The nature of the corresponding northeastern margin of the basin is less clear, but a series of poorly defined and partially buried dextral extensional structures has been hypothesized from topography, microseismicity, potential-field anomalies, and reconnaissance geologic mapping. This map is a contribution to a program designed to improve the geologic database for the Portland Basin region of the Pacific Northwest urban corridor, the densely populated Cascadia forearc region of western Washington and Oregon. Updated, more detailed information on the bedrock and surficial geology of the basin and its surrounding area will facilitate improved assessments of seismic risk, and resource availability in this rapidly growing region.
Oregon↗