• Inherent and Maximum Microbiological Activity in Smith Lake : Project Completion Report

      Burton, S. (University of Alaska; Institute of Water Resources, 1968)
      POPULAR ABSTRACT: Bacterial populations were examined in a sub-Arctic lake to augment the understanding of the flow of organic material and other nutrients through these waters. Several micro-organisms were isolated, capable of converting atmospheric nitrogen into biologically available forms. Also organisms capable of removing organic materials at very low temperatures, psychrophiles, were isolated. Enzymes from these unusual organisms were examined to determine what allows these unusual activity at low temperatures. The activities of these enzymes were not found to be unusual.
    • Initial Permafrost Engineering Research In Alaska

      Cysewski, Margaret Hope; Shur, Yuri (2013)
      Past permafrost engineering research and projects can aid modern permafrost engineering. The knowledge base of lessons learned among engineers is important, especially between generations of engineers, so history does not repeat itself Uncovering the history of permafrost engineering, and its compilation, summarization, and analysis, is beneficial for the Alaskan engineering community. This master's thesis is devoted to the early years of permafrost engineering in Alaska with projects carried out from the Gold Rush era to shortly after WWII. The projects include: thawing technology developed by gold miners, Alaska Highway road design and construction with its influence, and early comprehensive research by the Permafrost Division of the U.S. Army Corps of Engineers' St. Paul District, particularly the development of the test site, the Fairbanks Research Area, along Farmers Loop Road. Each of these projects has been successfully adapted to modern practices, laying the foundation of permafrost engineering.
    • Institute of Northern Engineering 2006 Annual Report

      University of Alaska Fairbanks, Institute of Northern Engineering; Rohr, Melanie (INE Publications, University of Alaska Fairbanks, 2006)
    • Integrated experimental and computer modeling approach to understand permafrost thaw subsidence induced oil well instability for Alaska North Slope oil wells

      Suryawanshi, Saurabh Sheshrao; Patil, Shirish; Dandekar, Abhijit; Bray, Matthew; Khataniar, Santanu (2016-05)
      Hydrocarbon reservoirs in the Arctic region of Alaska have been developed by various oil and gas producers for several years. Most of them are overlain by massive layers of permafrost soils which extend to a thickness of up to 2300 feet. Production and injection wells in such regions have experienced design and operational challenges due to heat loss from the wellbore and subsequent thawing of the permafrost soils. Thawing is a phase change of ice to water resulting in volumetric reduction of the frozen soil due to pore space contraction and segregated ice thaw, causing a major problem of thaw subsidence. Thaw subsidence affects the stability of the well, causing buckling and structural distress along the length of the wellbore within the thaw susceptible permafrost zones, thus damaging the well casing. Two different experimental approaches, one-dimensional consolidation and three-dimensional physical scale test, were employed to study thaw subsidence mechanisms in three different types of soils; namely, clay, silt and sand. The main objective of these experiments was to understand the well-soil system and the changes occurring within it with time, which will further increase knowledge of the interaction between the wellbore and the soil in Arctic regions during progressive thaw. Due to a lack of data and information, several areas were selected for multiple experimental approaches, including lateral pressure development, soil strain and strain within well casing, to study the frictional effects along the wellbore and pore-pressure response within the soil. Along with the experimental work, two different models were built in COMSOL Multiphysics™. The first model focused on thermal analysis of the thawing and refreezing behavior of ice-rich permafrost for drilling and production operations, while the second model focused on mechanical analysis, to study and understand the generation of the vertical and horizontal loads and stress-strain characteristics of the ice-rich permafrost. Simulations focused mainly on obtaining data for lateral pressure development, well stress-strain and temperature.
    • The integrated hydrologic and societal impacts of a warming climate in Interior Alaska

      Jones, Charles E.; Kielland, Knut; Hinzman, Larry; Kane, Douglas; Prakash, Anupma; Schneider, William (2014-12)
      In this dissertation, interdisciplinary research methods were used to examine how changes in hydrology associated with climate affect Alaskans. Partnerships were established with residents of Fairbanks and Tanana to develop scientific investigations relevant to rural Alaskans. In chapter 2, local knowledge was incorporated into scientific models to identify a socialecological threshold used to model potential driftwood harvest from the Yukon River. Anecdotal evidence and subsistence calendar records were combined with scientific data to model the harvest rates of driftwood. Modeling results estimate that between 1980 and 2010 hydrologic factors alone were responsible for a 29% decrease in the annual wood harvest, which approximately balanced a 23% reduction in wood demand due to a decline in number of households. The community's installation of wood-fired boilers in 2007 created a threshold increase (76%) in wood demand that is not met by driftwood harvest. Modeling of climatic scenarios illustrates that increased hydrologic variability decreases driftwood harvest and increases the financial or temporal costs for subsistence users. In chapter 3, increased groundwater flow related to permafrost degradation was hypothesized to be affect river ice thickness in sloughs of the Tanana River. A physically-based, numerical model was developed to examine the importance of permafrost degradation in explaining unfrozen river conditions in the winter. Results indicated that ice melt is amplified by increasing groundwater upwelling rates, groundwater temperatures, and snowfall. Modeling results also suggest that permafrost degradation could be a valid explanation of the phenomenon, but does not address the potential drivers (e.g. warming climate, forest fire, etc.) of the permafrost warming. In chapter 4, remote sensing techniques were hypothesized to be useful for mapping dangerous ice conditions on the Tanana River in interior Alaska. Unsupervised classification of high-resolution satellite imagery was used to identify and map open water and degraded ice conditions on the Tanana River. Ninety-five percent of the total river channel surface was classified as "safe" for river travel, while 4% of the channel was mapped as having degraded ice and 0.6% of the channel was classified as open water (overall accuracy of 73%). This research demonstrates that the classification of high-resolution satellite images can be useful for mapping hazardous ice for recreational, transportation, or industrial applications in northern climates. These results are applicable to communities throughout the North. For people that rely upon subsistence activities, increased variability in climate cycles can have substantial financial, cultural, recreational, or even mortal consequences. This research demonstrates how collaborations between scientists and local stakeholders can create tools that help to assess the impacts of increased environmental variability (such as flooding) or to detect or predict unsafe conditions (such as thin or unpredictable ice cover). Based upon this research, I conclude that regional-scale adaptations and technological advances (such as modeling and remote sensing tools) may help to alleviate the effects of environmental variability associated by climate.
    • Intelligent platform management interface protocol security

      Clayton, Syler W.; Hay, Brian; Nance, Kara; Genetti, Jon (2014-04)
      The Intelligent Platform Management Interface (IPMI) is a protocol that allows administrators to manage servers remotely. Hardware vendors including Dell, HP, Supermicro, IBM, Lenovo, Fujitsu and Oracle support IPMI though a Baseboard Management Controller (BMC) which can either be integrated into the motherboard or purchased as a pluggable module. The BMC runs silently alongside other components of the server and provides a lower level of hardware access than the Operating System (OS). This allows support for features like power cycling the server, mounting virtual media and accessing a remote console. The failure of BMC vendors to produce a more secure product, along with the inherent flaws of the IPMI protocol, increases the need for these systems' security capabilities to be evaluated. The IPMI protocol and various vendor implementations of the BMC has been the subject of recent scrutiny, and initial investigation has raised concerns about the security properties of these components. This project focuses on evaluating specific IPMI supported hardware and software setup in an environment modeled to simulate real use, for the explicit purpose of evaluating the security of the system. This project presents: several methods by which unprivileged users can gain remote access to the system, a list of best practices for proper configuration, a guide to clearing configuration settings before decommission, and a basic Metasploit module to scan for BMC related services.
    • Intelligent traffic monitoring and control system

      Ch, Nabil Al Nahin; Raskovic, Dejan; Thorsen, Denise; Hatfield, Michael (2019-08)
      This thesis presents an intelligent system for monitoring and controlling traffic by sensing vehicles' attributes and using communication between vehicles and roadside infrastructures. The goal of this system is to improve the safety of the commuters and help the drivers in making better decisions by providing them with additional information about the traffic conditions. A prototype system consisting of a roadside unit (RSU) and an on-board unit (OBU) was developed to test the functionalities of the proposed system. The RSU consists of sensors for detecting vehicles and estimating their attributes and a radio for communicating with the OBU. The OBU also has a radio for communication purpose. Afterward, a vehicle was used to test the functionalities of the system and the communication between OBU and RSU was evaluated by emulating the presence of a vehicle. A protocol for exchanging messages between the RSU and the OBU was developed to support effective communication. The efficiency of the communication process was further improved by varying the transmission range of different messages. A format for the message was proposed to convey all the necessary information efficiently. The process of collecting vehicle data, processing them and extracting useful information from the data was discussed here along with some limitations of the proposed system.
    • Internet based data collection and monitoring for wireless sensor networks

      Revuri, Venkatramana Reddy (2007-05)
      The omnipresence of the Internet and the advances in integrated circuit technologies has expanded the potential modes of communication and data collection. Adding Internet capabilities to any electronic device greatly extends the device's user interface, allowing the user to remotely configure and monitor the device over the network through the embedded web server. The embedded web server is expected to establish two-way communication and serve dynamic web pages using very limited resources. We adapted an existing embedded web server to allow remote control and monitoring of wireless sensor networks (WSN). This required establishing an interface to the WSN and developing firmware and user programs to communicate with the remote client. An interactive and flexible web-based user management interface is developed to allow the two-way interaction between the remote user and the wireless sensor network. The embedded server generates email alerts to the administrator about critical issues in the WSN, provides secure access to the WSN control modules, etc. Two embedded web servers are developed using different hardware platforms. The first solution is a low cost, energy efficient solution with somewhat limited functionality. The other uses a more powerful microcontroller-based platform and implements a fully-functional, dynamic web server with multiple web pages.
    • Investigation and development of a mathematical model for the oxidation of cyanide in the INCO SO₂/O₂ process

      Oleson, James L. (2003-12)
      The purpose of this study was to develop a mathematical model to describe the oxidation of cyanide with SO₂ as proposed in the INCO process. This research employed a direct method for measuring the change in cyanide concentration with respect to time as affected by varying concentrations of SO₂ and copper and pH. This model may be applicable in determining optimum conditions in a process well known and used in the mining industry.
    • An investigation into the cold heavy oil production with sand process using synthetic cores and designed experiments

      Narayan, Arya; Awoleke, Obadare; Ahmadi, Mohabbat; Hanks, Catherine; Liu, Jenny (2016-05)
      This study deals with the development of a methodology for making low compressive strength cores used in an experimental investigation of the Cold Heavy Oil Production with Sand (CHOPS) process. An experimental setup was designed and built to investigate the effect of rock compressive strength as well as flow parameters, such as oil viscosity, net and total confining pressure, and injection rate, on core permeability. The approach was to optimize the value of a response variable by changing the values of the affecting factors. Sand blends were prepared by varying the ratios of aggregate, cementing material and water to prepare synthetic cores. An experimental unit was built to simulate wormhole propagation during the CHOPS process, where oil, at an ambient temperature, was injected into 2-inch × 4-inch cores at varying rates of 0.5–10 ml/min under differential confining pressures of 500 and 1000 psia. The pressure drop across the core was monitored and recorded throughout the process. When non-swelling clay is used as a cementing material compared with actual cement to make synthetic core, the compressive strength of the samples falls dramatically by 64%. Two factors were considered in the coreflood experiments: Oil Viscosity (370 and 690 cp) and Injection Rates (0.5 and 3 ml/min) at a net confining pressure of 500 psia, below the compressive strength of the core. It is hypothesized that injecting oil of different viscosities at different rates affects the internal structure of the core in different ways (there is fluid-rock interaction) and thus, at lower pore volumes of injection, the permeability of the core for high viscosity oil is almost 11.2% greater than for low viscosity oil. Also, design of experiment approach was used and regression model was developed for permeability of core based on values recorded at specific pore volumes injected for different injection rates and oil viscosities. It was found that at a constant confining pressure for all rates and at lower pore volumes injected, 99.8% of the variance in permeability can be explained by oil viscosity, injection rate and their interaction. At higher pore volumes injected, the variance in permeability that can be explained by oil viscosity, the injection rate and their interaction is only 40.63%.
    • Investigation of a tensile cycloidal rotor and cam cyclic pitching mechanism

      Elfering, Kelsey H. (2012-08)
      A cycloidal rotor is characterized by an airfoil span parallel to the axis of rotation. A tensile cycloidal rotor places the airfoils under tensile forces only, thereby attempting to utilize the inertial forces on the rotor to minimize airfoil deflection and overall weight. A prototype rotor was built that meets the micro air vehicle (MAV) size constraint of 15.24 centimeters (6 inches). A new cam path design was used as a pitching mechanism, which reduced overall design weight and mechanical power requirements, and allowed for curved flat plate airfoils and angled airfoil structural supports. The cycloidal rotor was designed to pitch on both sides of the airfoils in an effort to reduce the axial force that was previously observed in mechanisms that pitch straight airfoils using an offset four bar linkage on only one side. The radial and axial strains were measured to determine the forces on the rotor, and compared well with a finite element simulation. The power-to-thrust ratio increased with RPM, which is in contradiction with theoretical rotor predictions. This indicated there are likely inefficiencies due to friction, which is supported by the measured non-zero power requirement at zero RPM.
    • Investigation of Alternative Deicers for Snow and Ice Control

      Fay, Laura; Akin, Michelle (Center for Environmentally Sustainable Transportation in Cold Climates, 2018-03-15)
      This technical report presents the findings of the laboratory analysis of potassium succinate (KSu) as a roadway deicer. Laboratory analysis included modified SHRP ice-melting testing, a differential scanning calorimetry (DSC) thermogram, and friction measurements to quantify performance. The overall results indicate that the performance of KSu is similar to that of NaCl at improving friction on roadways during snow and ice conditions. The results of DSC suggest that KSu can be applied as a roadway deicer at -5°C (23°F) and above. However, KSu does not function as a deicer at colder temperatures where salt brine will work (the generally agreed upon lowest working temperature for salt brine is 15°F [-9.5°C]). The results of the laboratory testing show that KSu functions as a roadway deicer with slightly lower ice-melting rates than salt brine. The ice-melting rates, DSC, and friction performance testing of KSu show that the product performs as a deicer at warmer temperatures than salt brine, with slightly less ice-melting capacity and similar friction performance. Based on these and previous results showing lack of corrosion in metals, equipment, and pavements from use of KSu and similar BOD of KSu to potassium acetates, KSu appears to be a viable option as a roadway deicer at temperatures at or above -5°C (23°F). Use of KSu as a roadway deicer may be focused in areas where there are concerns about impacts to infrastructure, equipment, or pavements, such as on bridges, elevated roadways, in parking garages, or on newer concrete pavements. Potential concerns with the use of KSu as a roadway deicer are its price, lack of full-scale manufacturing of KSu at this time, and the BOD exerted by the product. Additional testing to fully quantify the environmental impacts of KSu on soil, water, flora, and fauna is recommended. If water quality and BOD are of concern, application of this product is not recommended in large quantities and during times of low water flow.
    • Investigation of an ozone-filter system for color and iron removal at low temperatures

      Smith, Daniel W.; Hargesheimer, John M. (University of Alaska, Institute of Water Resources, 1975-10)
      The application of ozonation as a disinfectant and as a treatment process for both water and wastewater has been increasing in recent years. The study of ozone application to Arctic and subarctic waters, which are normally at low temperatures, has been limited. Many portions of the Alaskan Arctic and subarctic are plagued with waters which exceed the 1962 Drinking Water Standards for one or more parameters. The iron content and color of the water are among the most common offenders. This project was directed toward the examination of a method for water treatment utilizing ozone to meet the iron and color limits for drinking water. The three principle objectives of the project were: (1) to examine the effect of ozone on several known qualities of water, (2) to examine the effect of ozone on representative samples of surface and ground water, and (3) to develop a laboratory scale system for iron and color removal utilizing ozone followed by sand filtration.
    • Investigation of CO₂ sequestration options for Alaskan North Slope with emphasis on enhanced oil recovery

      Patil, Santosh Bramhadev (2006-08)
      Carbon dioxide (CO₂), the main component of greenhouse gases, is released into the atmosphere primarily by combustion of fossil fuels like coal and oil. Due to a conspicuous lack of any CO₂ sequestration studies for Alaskan North Slope (ANS), the study of CO₂ sequestration options will open new avenues for CO₂ disposal options, such as viscous oil reservoirs and coal seams, on the ANS. This study focuses on the investigation of CO₂ storage options by screening ANS oil pools amenable to enhanced oil recovery, evaluating phase behavior of viscous oil and CO₂ mixture, and simulating enhanced oil recovery by CO₂ flooding, and migration of CO₂ in saline aquifer. Phase behavior studies revealed that CO₂ gas was partially miscible with West Sak, at the pressure closer to the reservoir pressure. Compositional simulation of CO₂ flooding for a five-spot West Sak reservoir pattern showed an increase in percent recovery with an increase in pore volume injected, but at the expense of an early breakthrough. Sensitivity analysis of CO₂ flooding project was found to be strongly dependent on the variables such as oil price and discount rate. Investigation of supercritical CO₂ injection in saline formation didn't increase temperature in the permafrost region.
    • Investigation of phase behavior and reservoir fluid properties in support of enhanced oil recovery of Alaska North Slope (ANS) viscous oils

      Alurkar, Kaustubh D. (2007-12)
      Declining light oil production on Alaska North Slope (ANS) has attracted oil producers to develop viscous oil resources of ANS that range between 20 to 25 billion barrels. These oils are viscous, flow sluggishly in the formations, and are difficult to transport through unconsolidated formations and are hard to produce by conventional methods. Viscous oil recovery entails neatly designed enhanced oil recovery processes and the success of these processes is critically dependent on accurate knowledge of phase behavior and fluid properties of these oils under variety of pressure and temperature conditions. An experimental study was conducted to quantify the phase behavior and physical properties of viscous oils from ANS. The oil samples were compositionally characterized by simulated distillation technique, constant composition expansion and differential liberation tests were conducted on these samples. Experimentally studied phase behavior and reservoir fluid properties were modeled by using the Peng-Robinson Equation-of-State (EOS). The Peng-Robinson EOS was tuned with experimental data to predict the phase behavior, accurately. Widely used corresponding state viscosity model predictions deteriorate when applied to heavy oil systems due to use of ultra-light methane as a reference compound. Therefore, a semi empirical approach (Lindeloff model) was adopted for modeling the viscosity behavior. Viscosity behavior of degassed ANS viscous oils was correlated to their temperature and molecular weight. Integration of this correlation into the Lindeloff model resulted in accurate viscosity predictions for viscous oils under reservoir conditions.
    • Investigation of thermal regimes of lakes used for water supply and examination of drinking water system in Kotzebue, Alaska

      Bendlova, Tereza; Arp, Christopher D.; Duffy, Lawrence K.; Schnabel, William E.; Barnes, David L. (2012-08)
      Many villages in Arctic Alaska rely on lakes for water supply, such as the Alaskan City of Kotzebue, and these lakes may be sensitive to climate variability and change, particularly thermal regimes and corresponding effects on water quality. Thus, I initiated a study of water supply lakes in Kotzebue to collect data for developing a model to hindcast summer thermal regimes. Surface (Tws) and bed (Twb) temperature data collected from two water supply lakes and two control lakes from June 22nd-August 28th 2011 showed a similar pattern in relation to air temperature (Ta) and solar radiation with more frequent stratification in the deeper lakes. The average Tws for all lakes during this period was 14.5°C, which was 3.4°C higher than Ta for the same period. I modeled Tws from 1985 to 2010 using Ta, and theoretical clear-sky solar radiation (TCSR) to analyze interannual variability, trends, and provide a baseline dataset. Similar to patterns in Ta for this period, I found no trend in mean Tws for the main lake used for water supply (Devil's Lake), but considerable variation ranging from 12.2°C in 2000 to 19.2°C in 2004. My analysis suggests that 44% of years during this 25 year period maximum daily Tws surpassed 20°C for at least one day. This hindcasted dataset can provide water supply managers in Kotzebue and other Arctic villages with a record of past conditions and a model for how lakes may respond to future climate change and variability that could impact water quality.
    • Investigations of lightweight aggregates in Alaska

      Heiner, L.E.; Loskamp, A.N. (University of Alaska Mineral Industry Research Laboratory, 1966)
      Increased construction costs coupled with the current large demand for aggregate materials prompted an investigation by the Mineral Industry Research Laboratory to find deposits of shale suitable for the manufacture of lightweight aggregate near the cities of Anchorage and Fairbanks.
    • Iron in Surface and Subsurface Waters, Grizzly Bar, Southeastern Alaska

      Hoskin, Charles M.; Slatt, Roger M. (University of Alaska, Institute of Water Resources, 1972-08)
      Atomic absorption spectrophotometric measurements for total iron were made on 69 samples of water from 8 different environments in an outwash fan built by meltwater streams from the retreating Norris Glacier on granodiorite bedrock. Norris Glacier ice contained no iron (3 samples), a subglacial stream contained 5.5 ppm Fe (1 sample), and a meltwater lake fronting Norris Glacier contained 0.7 ppm Fe (3 samples). Iron content of ground water from outwash ranged between 0.0 and 17.0 ppm (6 samples); surface streams fed by emergent ground water on the fan periphery contained 0.0 to 0.2 ppm Fe (13 samples). Taku Inlet waters contained 6.4 ppm Fe (3 samples). Subsurface water from an intertidal mud flat contained between 0.0 and 27.0, X 5.9, ppm Fe (31 samples). Surface and subsurface water from a bog and associated stream contained 1 ppm Fe (12 samples). Little exchangeable Fe was found. In situ measurements in water for Eh showed large positive values (+0.30 to +0.50 volts) and pH was slightly alkaline. The single most important source of iron was vermiculitized biotite. Iron was transported in water in the particulate state, except in outwash ground water where particulate Fe+3 was reduced to dissolved Fe+2. Iron deposits of Fe(OH)3 were found near the top of the outwash water table.
    • Juvenile Fish Passage Through Culverts in Alaska: A Field Study

      Kane, Douglas L.; Belke, Charles E.; Gieck, Robert E.; Mclean, Robert F. (2000-06)
      In the past, culvert design where fish passage was considered generally has been based on the weakest-swimming adult fish in a river system. It has also been recognized for some time that juvenile fish are very active throughout the year, moving upstream and downstream in response to a number of environmental factors. In Alaska, many natal and nonnatal streams in southcentral and southeastern Alaska support both Chinook (Oncorhynchus tschawytscha (Walbaum)) and Coho (Oncorhynchus kisutch (Walbaum)) for one to three years, respectively, before they emigrate to sea. Are we restricting desirable habitat for these juvenile salmonids with hydraulic structures such as culverts? Unfortunately we have little information on either the behavior of juveniles in the vicinity of hydraulic structures or their swimming abilities. The objective of this study was to examine the behavior of juveniles when attempting to ascend a culvert. It was hypothesized that vertical obstacles or high velocity of opposing flow may prevent juvenile fish from moving upstream. It was also hypothesized that they would determine and take the path of least resistance to optimize their chances of successfully ascending a culvert. Four culverts were selected for intensive study regarding juvenile fish passage: Beaver and Soldotna Creeks on Kenai Peninsula and No-name and Pass Creek Tributary on Prince of Wales Island. It was postulated that fish are motivated to move upstream to obtain food if they can establish its presence. We used salmon eggs as an attractive food source both to initially capture the juveniles and then to motivate them to ascend the culvert for possible recapture. Juvenile fish were captured in a baited minnow trap and stained with a dye. They were released downstream of the culvert while the food source was placed upstream in a minnow trap. We supplemented our visual observations with underwater video cameras. We made numerous hydrologic and hydraulic measurements at each site. Although we attempted to select culverts that would prove to be quite challenging to juvenile fish passage, in three of the culverts selected, juvenile fish, of the full range of the fork length initially captured, succeeded in ascending through the culvert. For the fourth culvert, some larger juvenile fish succeeded in ascending the culvert, but not the smaller of each fish type. It was clearly established that juvenile fish were motivated to move upstream to obtain food. In the Beaver Creek culvert, fish used the large corrugations to their advantage when ascending the culverts. The Pass Creek Tributary culvert had corrugations too small for fish to utilize. No-name Creek appeared to present not problems for juvenile fish for the water levels at the time of the visit as they small along the bottom on the centerline of the culvert. In general, observations of fish attempting to move upstream through the culvert revealed that they swam very close to the culvert wall, and in the case of high velocities (Beaver Creek and Pass Creed Tributary) they swam near the surface along the sidewall where velocities are reduced. It is obvious that the juvenile fish are attempting to minimize power output and energy expenditure by taking the path of least resistance. Although not quantitavely proven, it appears that as long as fish make some headway in their upstream movement they are content. The rationale for this conclusion is that fish do not know what they may encounter upstream so they attempt to conserve as much power and energy as possible while still moving forward. They generally do so by seeking out the lowest velocities in the cross-section. In areas of steep velocity gradients along the wall (where the areal extent of low velocities is limited), it is clear in our videotapes that fish have problems maintaining their position and preferred orientation. It is apparent from our observations that because of their small size, juvenile fish are hindered by turbulence and that this area needs more study.