A single link to the first track to allow the export script to build the search page
  • Tuesday, May 1, 2018
  • Tuesday, May 1, 2018

    1A: Conference Theme - Sustainability

    BENEFITS OF USING EXISTING DAMS FOR FLOOD MITIGATION IN THE MOODNA CREEK WATERSHED, ORANGE COUNTY, NY

    Tuesday May 01, 2018 1:30 PM - Tuesday May 01, 2018 3:00 PM

    • Allan Estivalet, Dams and Water Resources Group Lead ;
    • Gregory Shaffer, Senior Project Engineer ;
    • Michelle Bowen, Water Resources Engineer

    This paper presents the benefits of adapting existing dams and reservoirs to mitigate flooding and the methodology for quantifying those benefits. For communities facing flooding risks, this approach can be more cost effective than constructing new flood control infrastructure. Leveraging flood mitigation funding to rehabilitate and upgrade existing dams also reduces dam failure risks and protects the benefits provided by impounded reservoirs.

    Hurricane Irene hit the East Coast in late August 2011, causing extensive flooding and resulting in millions of dollars in damages. The New York Rising Community Reconstruction Program is a $700 million planning and implementation program that provides rebuilding and resiliency assistance to communities severely damaged by Hurricane Irene. As part of this program, WSP assisted several communities in the development of a drainage master plan to accurately understand flooding risks and propose mitigation measures.

    To model local flood risks, WSP developed an integrated hydrologic and hydraulic model. This model used an innovative 1D/2D approach coupled with GIS resources and incorporated climate change projections to assess future flood risk. The model enabled the identification and analysis of the best flood mitigation projects. As part of this process, our team identified the existing reservoirs that could be used most effectively to alleviate downstream flooding. Engineering assessments were performed for 12 identified dams to determine modifications to maximize each reservoir’s storage capacity. Proposed solutions included dam rehabilitation, spillway and dam crest modifications, flood control gates, and remediation of low level outlets. In addition to structural changes, our hydraulic model was used to develop operational procedures that will maximize flood mitigation benefits.

    Our team used a robust financial analysis to evaluate the costs and benefits of different dam modification projects. Financial analysis allows communities to prioritize spending under intense fiscal constraints. The methods used are outlined in detail in this paper.

    BENEFITS OF USING EXISTING DAMS FOR FLOOD MITIGATION IN THE MOODNA CREEK WATERSHED, ORANGE COUNTY, NY

    Ecosystem Considerations in Dam Safety Inspection and O&M

    Tuesday May 01, 2018 1:30 PM - Tuesday May 01, 2018 3:00 PM

    • Jonathan Keeling, Stantec Consulting Services Inc. ;
    • Benjamin Webster, Stantec

    Field inspections are an essential part of a dam safety program. The inspections serve as the foundation for proper surveillance of a dam and provide a baseline visual assessment of the structure’s overall condition. Operation and/or maintenance actions taken as a result of these inspections, however, can have direct or indirect impacts to the ecosystem around the dam, including wetlands, critical wildlife habitat, and threatened/endangered species. For those dams associated with recreational usage (e.g. park lands), these actions can also have negative effects on the area’s viewshed (sightlines) and indirectly affect the public’s enjoyment of the benefits provided by the dam. This is particularly true in situations where urban planners working with growing population areas are looking to maximize use of valuable greenspace to provide future benefits. In many situations ponds, lakes or reservoirs, and the dams used to create these features, form the primary component of these greenspaces. Traditional maintenance techniques used for dams may not be appropriate in these situations and require modification or development of alternate procedures to balance addressing critical dam safety issues with the surrounding natural environment.

    Alternative inspection techniques and composition of inspection team (e.g. inclusion of aquatic biologists, ecologists) will be reviewed from past experience, with a focus on lessons learned. In addition, perspectives and practices from private dam owners (including flood control authorities and conversation districts) will be presented and discussed. Finally, case studies and past experience will be used to illustrate successful integration of environmental considerations with operation and maintenance activities at dams.

    Ecosystem Considerations in Dam Safety Inspection and O&M

    The Many Lives of The Hillsborough River Dam, Tampa, FL

    Tuesday May 01, 2018 1:30 PM - Tuesday May 01, 2018 3:00 PM

    • John Rañon, City of Tampa ;
    • Stewart Vaghti, Gannett Fleming, Inc. ;
    • Tom Burke, Southwest Florida Water Management District

    If the value of a dam is quantified by the number of resurrections, then the Hillsborough River Dam is valuable indeed. The original timber crib dam was constructed in 1897 to support a booming cigar business in the growing City of Tampa, Florida. The dam survived sabotage attempts in 1898 and 1916, an overtopping failure in 1933, and severe flooding in 1960. The demand for hydroelectric power during the dam’s early years and water for the vibrant Tampa community was enough for the dam to be rebuilt and improved over the years. The dam currently supports the David L. Tippin Water Treatment Facility which produces about 80 million gallons per day (MGD). A 2006 legal settlement about the dam’s impacts on downstream habitat set the stage for an expanded recovery program using fresh water to hydrate the river’s lower reach. Releases now mandated by state statute, are intended to lower salinity levels on native fishes and invertebrates that inhabit the river segment between estuarine and freshwater communities.

    In 2016, the City of Tampa and the Southwest Florida Water Management District (SWFWMD), partners in the Lower Hillsborough River Recovery program, moved forward to replace a temporary pumping system that transferred water from the Hillsborough Reservoir to the base of the dam. Three options were studied: modifying the existing radial gate control system for more precise flow control; a siphon over the crest of the dam; and a new low flow slide gate. The City and SWFWMD opted to proceed with a new 16-inch by 24-inch stainless steel slide gate with an outlet conduit that penetrates the existing concrete gravity dam.

    This paper discusses the dam’s resilient history and the current slide gate design intended to meet environmental objectives while continuing the dam’s legacy as a valuable resource to the Tampa community

    The Many Lives of The Hillsborough River Dam, Tampa, FL

    An Evaluation of the Capacity of Coastal Spillways under Projected Sea Level Rise and Storm Surge Conditions

    Tuesday May 01, 2018 1:30 PM - Tuesday May 01, 2018 3:00 PM

    • Mark Wilsnack, South Florida Water Management District ;
    • Lichun Zhang, South Florida Water Management District

    The South Florida Water Management District (SFWMD) is currently evaluating flood protection Levels of Service (LOS) for selected watersheds within Miami-Dade County, Florida. Among the basins recently studied is the C-7 watershed, which drains to tide through coastal spillway S-27. It appears that the original design of S-27 did not consider sea levels that are as high as those currently observed or projected to occur in the future. Consequently, its operation is sometimes challenging, especially during high tides. In fact, under high tail water conditions induced by high tides, the structure’s gates may close more than once a day to prevent the reverse flow of salt water through S-27. Using a methodology developed by Cadavid et al. (2015), an evaluation of the hydraulic capacity of S-27 under various sea level and storm surge conditions was performed by Zhang (2017). The results indicate that the discharge capacity of S-27 is sensitive to sea level and storm surge. Decreases in capacity due to rising sea level and storm surge are highly salient for both current and projected future sea levels. Moreover, under current sea level conditions, the results of the analysis suggest that S-27 will not be able to pass any flow during the peak of a storm surge with a recurrence interval of 5 years or greater. Under projected future sea level conditions, it was found that the structure will have no capacity during the peak of any storm surge with a recurrence interval of two years or more.

    An Evaluation of the Capacity of Coastal Spillways under Projected Sea Level Rise and Storm Surge Conditions

    1B: Earthquakes - Concrete I

    ANALYSIS OF PERFORMANCE BASED TESTING OF LOWER BAKER DAM

    Tuesday May 01, 2018 1:30 PM - Tuesday May 01, 2018 3:00 PM

    • Gurinderbir Sooch, Hatch ;
    • Dan Curtis, Hatch ;
    • Larry Nuss, Nuss Engineering, LLC ;
    • Will Hultman, Shannon and Wilson Ltd. ;
    • Nabil Dbailo, Puget Sound Energy

    A detailed assessment of Lower Baker Dam was performed for seismic and PMF loading conditions. A nonlinear 3D finite element model was developed and the analysis was performed using the explicit finite element LS-DYNA. The dam-foundation interaction was modeled in detail including foundation mass, non-reflecting boundaries and deconvoluted earthquake ground motions. The dam was constructed in the 1920’s with unique construction sequencing i.e., raising the central portion well ahead of the abutment blocks resulting in unusual contraction joint geometry. Performance based testing performed by others was used to establish the structure response to loading supplied by a Cold Gas Thruster and under ambient conditions. The results of performance based testing were used to calibrate the model as little information was available on dam concrete and foundation material properties. The model calibration was performed in the frequency domain whereby the computed structure response was compared to its measured response. The seismic analysis was performed with three earthquake return periods i.e., 1 in 2500, 5000 and 10000. The result from the seismic analysis are used in the risk assessment which is summarized herein.

    ANALYSIS OF PERFORMANCE BASED TESTING OF LOWER BAKER DAM

    Williams Fork Dam; Methods to Better Understand Seismic Behavior

    Tuesday May 01, 2018 1:30 PM - Tuesday May 01, 2018 3:00 PM

    • Aimee Corn, Gannett Fleming ;
    • Guy Lund, Gannett Fleming ;
    • Alex Walsh, Gannett Fleming ;
    • Erin Gleason, Denver Water ;
    • Darren Brinker, Denver Water

    Advancements in earthquake understanding over the last few decades have shown engineers that the seismic hazard in Colorado is significantly higher than originally thought. As a result, the seismic loads for Williams Fork Dam have more than tripled since the project was completed in 1959. Traditional stability evaluations have focused on the behavior of the structure for standards based seismic hazards, such as the maximum credible earthquake (MCE). Over the last few decades’ dam owners have seen hydrologic and seismic loads change (usually increased), primarily due to enhanced engineering understanding of the hazards. Many times, the previous studies become nullified and the owner finds themselves paying for new, costly, revised studies.

    Williams Fork Dam is a concrete arch dam located on the Williams Fork River approximately two miles south of Parshall, CO and is owned and operated by Denver Water. The original dam consisted of a curved concrete gravity structure, completed in the 1930s. The upper 15 to 45 feet of the original dam was removed to provide the foundation for the arch section. In 1959 the variable thickness and radius concrete arch was constructed.

    Since the estimated magnitude of the seismic hazard at the dam has tripled the design load, current guidelines require a revised structural stability analysis. Structural studies used three-dimensional linear and non-linear finite element models to evaluate the behavior of the dam. These studies evaluated the dam's behavior for seismic events simulating the MCE. This paper explores techniques to understand the behavior of the linear model for a range of seismic events prior to performing the non-linear analysis. 

    Williams Fork Dam; Methods to Better Understand Seismic Behavior

    NEW INSIGHTS INTO SEISMIC DESIGN AND SAFETY EVALUATION OF DAM APPURTENANT STRUCTURES AND EQUIPMENT

    Tuesday May 01, 2018 1:30 PM - Tuesday May 01, 2018 3:00 PM

    • Najib Bouaanani, Polytechnique Montreal (Canada)

    Appropriate evaluation of seismic demands along the height of a dam is crucial for the seismic design and safety evaluation of the structure itself, as well as critical appurtenant systems and safety-sensitive equipment. Indeed, amplification of seismic demands in dams may cause significant damage, eg. Koyna dam (India), Hsingfengkiang buttress dam (China). In other events, if damage to the dam itself remained marginal, supported equipment and appurtenant structures were severely affected by amplified ground motions, which induced offset or cracking of elements such as walls, parapets, or bridge girders. This paper presents an extensive investigation of seismic demands in concrete dams for the evaluation of seismic performance and vulnerability of safety-critical appurtenant structures, eg. bridges, control unit buildings, spillway support structures, gates, hoist bridges, power supply units, and lifting equipment. Practicing engineers are usually faced with the selection of most appropriate assumptions without prior knowledge of their relative impacts on seismic design and safety evaluation. Well-informed choices are however crucial considering the critical importance and seismic vulnerability that may be associated with dam-supported appurtenant structures. The approach and results presented in this paper will feed such informed choices through several case studies. The influence of several assumptions on the earthquake response of appurtenant systems and equipment will be illustrated. For instance: (i) to what extent should the geometries of the dam and reservoir be modeled in detail? (ii) how do the characteristics of ground motions affect the results? (iii) what is the impact of vertical accelerations and when could they be ignored? (iv) when do added-masses provide acceptable results and when should water compressibility effects be included? (v) should reservoir bottom wave absorption be considered? (vi) when should 3D effects be included? 

    NEW INSIGHTS INTO SEISMIC DESIGN AND SAFETY EVALUATION OF DAM APPURTENANT STRUCTURES AND EQUIPMENT

    Gross Dam - Raising Sigma to the 10,000 Year Return Period

    Tuesday May 01, 2018 1:30 PM - Tuesday May 01, 2018 3:00 PM

    • Dina Hunt, Gannett Fleming ;
    • Christine Weber, Stantec

    Gross Dam was completed in 1954, but the full configuration was not built as the design and construction envisioned a future raise. More than 63 years later the future is becoming reality with plans to have the new 131 foot raise completed around 2025.

    The field of seismic hazard has grown quite rapidly since the initial design of Gross Dam, and continues to evolve as earthquakes occur and faults are investigated. A current seismic hazard study was completed for Gross Dam, which is situated near the boundary between the Southern Rocky Mountains Province to the west and the Great Plains Province to the east. These two seismotectonic provinces represent very contrasting regions of tectonic activity, seismicity, and crustal properties. Highlights of the current probabilistic and deterministic seismic hazard assessment include the use of both the NGA West 2 and 2013 EPRI ground motion models. A design response spectrum, including magnitude, distance and epsilon, was deterministically developed for the Southern Rocky Mountain areal source zone.

    Gross Dam - Raising Sigma to the 10,000 Year Return Period

    1C: Oroville Dam Spillway Incident

    EROSION PROTECTION FOR THE EMERGANCY SPILLWAY AT OROVILLE DAM

    Tuesday May 01, 2018 1:30 PM - Tuesday May 01, 2018 3:00 PM

    • Brett K. Manier, Drill Tech Drilling & Shoring, Inc. ;
    • Franz-Werner Gerressen, BAUER Maschienn GmbH

    Abstract

    During two days of use in February 2017, the rock at the unlined Emergency Spillway at the Oroville Dam eroded as deep as 40’ and endangered the dam, forcing the evacuation of almost 200,000 people downstream of the dam.

    To prevent erosion of the rock during future use of the Emergency Spillway, a 1450’ long secant pile wall was installed. The secant wall consists of 605ea 36-in diameter piles ranging in depth from 40’ to 95’.

    Drilling started in weathered rock at the ground surface and all piles were socketed at least 20’ into fresh granitic rocks with strengths up to 50,000psi. Some of the fresh rock sockets are over 50’ in depth.

    The secant piles were installed through the weathered rock by augers and core barrels mounted on large rotary drill rigs. The fresh rock was drilled with 36-inch down hole hammers.

    Work is anticipated to be complete by 12/31/17

    The paper/presentation will focus on the unique conditions and related challenges. The installation of the secant wall will be described, as well in terms of construction technique and related equipment solutions.

    EROSION PROTECTION FOR THE EMERGANCY SPILLWAY AT OROVILLE DAM

    The Oroville Dam Crisis: Warning and Human Response

    Tuesday May 01, 2018 1:30 PM - Tuesday May 01, 2018 3:00 PM

    • Jason Needham, US Army Corps of Engineers ;
    • Dennis Mileti, Professor Emeritus, University of Colorado, Boulder ;
    • John Sorensen, Oak Ridge National Laboratory (Retired)

    On February 7, 2017, project staff detected erosion on the primary service spillway for Oroville Dam in northern California, causing an elevated concern for the safety of downstream communities.  The situation seemed stable until continued heavy rains resulted in the flow of water over the emergency spillway. On February 12, erosion below the emergency spillway was observed.  At 4:21 PM on February 12, the Butte County Sheriff issued an evacuation order for “low levels of Oroville and downstream areas”. Local emergency managers downstream followed with evacuation warnings. This papers will present final results of research, sponsored by the U.S. Army Corp of Engineers, on warnings and evacuation during the Oroville event.  This investigation is part of a research program designed to collect and analyze data on: 1) The timing of the decisions to order public evacuation warnings including the flow of information between the scientists monitoring the hazard and local officials. 2) The method and timing of the dissemination of those warnings including the diffusion or warning by various communication channels. 3) The interpretation and response of the public to those warnings, including the timing of protective action decisions.  The findings from this studies will be incorporated into risk assessment methods used in to inform dam and levee safety investment decisions.

    The Oroville Dam Crisis: Warning and Human Response

    Emergency Response Monitoring for Oroville Spillway

    Tuesday May 01, 2018 1:30 PM - Tuesday May 01, 2018 3:00 PM

    • Kayla Ranney, HDR ;
    • Jaime Lubeck, HDR ;
    • Daniel Osmun, HDR ;
    • Olivia Virgadamo, California Department of Water Resources, Division of O&M, Dam Safety Branch

    Beginning in February 2017, continuous emergency monitoring of the Oroville spillway was performed in a joint effort between the Department of Water Resources’ (DWR’s) Dam Safety Branch and HDR as part of the overall emergency response. Monitoring included visual assessments of site conditions and data collection at various frequencies performed by teams of inspectors and engineers. Continuous data analysis and reporting was also performed. Throughout the emergency monitoring period, it was important to monitor for any change to the spillway chute. Emergency situations like the unexpected damage to the spillway chute, combined with increased rainfall and reservoir levels, shows the need for dam safety engineers to have the ability to evaluate potential risks and respond quickly with recommendations to minimize the potential for further damage. This paper provides an overview of the progression of emergency response monitoring, staffing, reporting, and data analysis throughout the duration of the emergency period. Additionally, lessons learned and procedures to consider in future emergency situations from the Oroville spillway incident are discussed.

    Although there are many different aspects of the Oroville spillway incident, this paper will focus only on emergency response monitoring performed by DWR and HDR between February and May 2017.

    Emergency Response Monitoring for Oroville Spillway

    1D: Tailings Dams and CCR

    Conclusions from evaluation of tailings dam incidents

    Tuesday May 01, 2018 1:30 PM - Tuesday May 01, 2018 3:00 PM

    • Clint Strachan, Stantec ;
    • Brenna Van, Stantec

    This paper summarizes a review of tailings dam incidents, and examines the key constituents contributing to the causes and consequences of these incidents. Comparisons are drawn with water-storage dams, and conclusions are presented on reducing the potential for future incidents.

    The tailings dam incident review includes data compiled from available on-line sources and previous incident publications (including the US Society on Dams, International Commission on Large Dams, and the United Nations Environmental Programme). The incident data (from 1900 through 2016) was evaluated and classified for dam characteristics, dam height, and operating conditions.

    The type of incidents (ranging from a minor release with subsequent repair and reuse to a dam breach and tailings release), are compared with history, dam height, dam characteristics, and reported incident cause. The results demonstrate that both ponded and interstitial water are contributing factors in the causes and consequences of these incidents.

    Managing ponded water and saturated conditions in the tailings are key factors, so that the probability for overtopping the dam, occurrence of seepage and piping, and unacceptable dam slope stability are reduced. The likelihood of downstream consequences would also be reduced by transition of the tailings from a saturated deposit with low shear strength and a resulting high potential for downstream flow to an unsaturated deposit with higher shear strength and no potential for flow.

    Conclusions from evaluation of tailings dam incidents

    USSD Workshop Summary: Lessons Learned from Recent Tailings Dam Failures and Path Forward

    Tuesday May 01, 2018 1:30 PM - Tuesday May 01, 2018 3:00 PM

    • Robert Snow, D'Appolonia Engineering ;
    • Amanda Adams, MWH now part of Stantec ;
    • Gregory Hebeler, Golder Associates, Inc. ;
    • Phillip Crouse, MWH now part of Stantec

    Recent tailing storage dam and coal combustion residual impoundment failures have cast a negative light on the mining and power generation industries in the US and around the world. Proper design, operation and regulation of these waste facilities is vital to maintain the public safety of the surrounding communities. Understanding the causes of these recent failures and examining lessons learned from previous historic failures is crucial to adequately respond to public safety and environmental impact concerns. During a two day workshop in September 2017, USSD brought together a diverse group of consultants, owners, dam safety officials, and regulators to discuss the causes of these recent failures and consider lessons learned with a focus on changes that could be implemented in the areas of design, regulation, and operation. New approaches and applications are being considered, such as alternative tailing disposal technologies. Regulatory changes being considered or implemented include prescriptive requirements (e.g., maximum slopes) and greater oversight such as independent technical review panels. Operational changes include consideration of risk based approaches (e.g., Failure Modes and Effects Analysis), critical controls and governance programs.

    The authors will summarize the workshop and present the findings, observations, and recommendations for a path forward based on the input from workshop participants.

    USSD Workshop Summary: Lessons Learned from Recent Tailings Dam Failures and Path Forward

    When a CCR Impoundment is Not a Tailings Dams

    Tuesday May 01, 2018 1:30 PM - Tuesday May 01, 2018 3:00 PM

    • Robert Bachus, Geosyntec Consultants ;
    • Robert Snow, D'Appolonia Engineering

    The 2014 tailings dam failure at the Mt. Polley mine in Canada bears striking resemblance to the 2008 coal combustion residual (CCR) dredge cell failure at the Kingston Fossil plant in Tennessee. Both facilities were constructed and operated as tailings dams. While many CCR ponds contain tailings-like materials (i.e., sluiced fly ash and bottom ash), the construction of many CCR impoundments more resemble homogeneous earthfill dams, not tailing dams. However, as many of the old CCR ponds are being closed in-place and the containment dikes partially removed, the properties of the impounded materials (i.e., the “tailings”) must be considered by designers and regulators. This paper and presentation will highlight the various techniques used to construct CCR impoundments and draw similarities and differences to their mining counterparts…tailings dams. The authors will also introduce the engineering properties of CCR materials and the important role of the water retained in the impoundment when considering long-term final closure options.

    When a CCR Impoundment is Not a Tailings Dams

    NUMERICAL ANALYSIS OF DISPLACEMENTS IN THE POST-EXPLOITATION PERIOD OF TAILINGS DAMS WITH A COMBINED CONSTRUCTION METHOD

    Tuesday May 01, 2018 1:30 PM - Tuesday May 01, 2018 3:00 PM

    • Ljupcho Petkovski, University “Sts Cyril and Methodius ;
    • Stevcho Mitovski, University “Sts Cyril and Methodius

    The similarities between the tailings dams and the embankment dams for water storage have contributed a great number of procedures and techniques in the design, construction and maintenance of the conventional dams, to be applied to tailings dams.However, the numerous reports of collapses of the tailings dams in the last three decades, all over the World, indicate that the structural, (static and dynamic), filtration, hydrological and hydraulic safety were not controlled with the same rigor and carefulness - as for the embankment dams. This fact, in part, results from the long-term construction of the tailings dams, where as a building material is used sand obtained by separating of the waste material from floatation process during the exploitation of the mine.In this paper are presented results from the static analysis of the hydro tailings Topolnica, on the river Topolnica, in the east part of Republic of Macedonia. It is a tailings dam with a combination of downstream (in the first phase) and upstream ( in the second phase) method of construction, with total height from the crest to to downstream toe of the dam of 141.2 m.

    NUMERICAL ANALYSIS OF DISPLACEMENTS IN THE POST-EXPLOITATION PERIOD OF TAILINGS DAMS WITH A COMBINED CONSTRUCTION METHOD

    Argonaut Dam Remediation

    Tuesday May 01, 2018 1:30 PM - Tuesday May 01, 2018 3:00 PM

    • Richard Millet, AECOM ;
    • Rekha Nanduri, AECOM ;
    • Nick Plath, AECOM ;
    • Tami Trearse, DTSC

    The California Department of Toxic Substances Control (DTSC)—not normally in the dam safety business—is addressing the stability of the 100 year-old, 45 foot-high Eastman Barrel Arch Dam. Argonaut Dam near Jackson, California, was built to contain tailing waste from nearby gold mining and processing. By the early 1920s, tailing had completely filled the dam’s storage capacity with very soft (less than one blow per foot standard penetration test) tailings with high concentrations of arsenic, lead, and mercury. During DTSC environmental review of the now abandoned mining operation, the United States Army Corps of Engineers (USACE) performed a failure mode analysis of the dam. Although severely weathered, statically the dam met modern safety stability criteria. However, under seismic loading with the potentially liquefiable tailing loading the dam’s arches, stability criteria were not met. A failure of the dam would release the contaminated tailings as a “mud” flow into a downstream urban area.

    Consequently, DTSC and their consultant, AECOM, have undertaken a design to stabilize Argonaut Dam. This paper reviews three remediation alternatives considered and AECOM’s recommendation of a unique and economical composite stabilization design, utilizing both cellular concrete infilling of the arches in conjunction with a drained downstream embankment.

    Argonaut Dam Remediation

    1E: Embankment Dams I

    Selecting a Geomembrane System for a Lined Embankment Dam and Reservoir Project

    Tuesday May 01, 2018 1:30 PM - Tuesday May 01, 2018 3:00 PM

    • Chad Hoover, Gannett Fleming, Inc. ;
    • Paul Schweiger, Gannett Fleming, Inc. ;
    • Trent Dreese, Gannett Fleming, Inc ;
    • Cari Beenenga, Gannett Fleming, Inc. ;
    • Anthony Nokovich, American Water

    Several geomembrane systems are available for use at reservoir and dam projects.  Choosing the right system is not always a straight forward decision.  Selecting a geomembrane is site and project specific, and must consider many factors including: the exposure conditions, installation configuration, intended purpose of the facility, operation and maintenance performance criteria, material availability, project size, service life of the facility, and owner preferences. This paper provides a summary of currently available geomembrane systems used to line embankment dams and reservoirs, discusses their general properties, and presents a screening process to help designers and owners select a geomembrane for different types of dam and reservoir projects. 

    The selection of the geomembrane for two recent upland pumped-storage projects are presented including the rehabilitation of the Tampa Bay Reservoir in Florida, and the construction of the new Bel Air Reservoir in Maryland.   A different geomembrane was selected for each project.  Nine different geomembrane systems are presented and described with their performance on similar existing projects.  The geomembrane systems were evaluated based on appearance, history of performance, constructability, water tightness, strength, durability, and cost. The cost evaluation included a life-cycle cost analysis. Lessons learned from the evaluation of the geomembrane systems for the Tampa Bay Reservoir and Bel Air reservoir projects will be shared.

    Selecting a Geomembrane System for a Lined Embankment Dam and Reservoir Project

    Raw Water Storage Impoundment on Critical Path for Savannah Harbor Expansion Project

    Tuesday May 01, 2018 1:30 PM - Tuesday May 01, 2018 3:00 PM

    • Stephen Whiteside, CDM Smith ;
    • Danielle Neamtu, CDM Smith ;
    • Shayne Wood, CDM Smith ;
    • Robert Nagel, CDM Smith ;
    • Nathan Bryan, U. S. Army Corps of Engineers, Savannah District

    Construction has begun on the Savannah Harbor Expansion Project (SHEP) that will deepen the outer harbor to 49 feet at mean low water and the Savannah River channel to 47 feet. The City of Savannah operates a water supply intake on Abercorn Creek approximately two river miles from the confluence with the Savannah River. From the intake, raw water is piped 7.25 miles to a treatment facility in Port Wentworth, GA.

    Based on previous project studies, the proposed deepening of Savannah Harbor will increase salinity and chloride concentrations in Abercorn Creek. Distribution pipeline corrosion, including lead and copper in residential plumbing and certain industrial processes, are sensitive to elevated chloride concentrations. Based on the feasibility study performed by CDM Smith, a new raw water storage impoundment was determined to be the best option to provide water with lower chloride concentrations during high-chloride events at the intake.

    As Engineer of Record for the U. S. Army Corps of Engineers Savannah District, CDM Smith designed the 97-million-gallon (MG) reservoir. The project includes a 26-foot-high four-sided embankment with an HDPE liner for raw water storage, four 500-HP vertical turbine “can” style pumps, powdered activated carbon injection system, and approximately 1,500 feet of piping. The overall capacity of the transfer pump station is 63 MGD. CDM Smith performed a dam breach analysis, and the wetlands, endangered species, and cultural resource investigations.

    The reservoir site had several challenges that needed to be addressed in the design, including soft surficial clay layers and shallow groundwater. The design included geotechnical instrumentation to monitor the performance of the dam during and after construction. The embankment design includes multiple seepage control measures. The USACE resident engineers and geotechnical engineer are currently overseeing the construction and the instrumentation monitoring. Construction is scheduled to be complete in summer 2018.

    Raw Water Storage Impoundment on Critical Path for Savannah Harbor Expansion Project

    Defect Seepage Modeling

    Tuesday May 01, 2018 1:30 PM - Tuesday May 01, 2018 3:00 PM

    • Michael McCaffrey, WSP ;
    • Kevin Finn, WSP ;
    • Paul Shiers, WSP ;
    • Peter Bouchie, WSP

    Seepage and a cloudy water discharge was historically observed at the downstream toe of the North Embankment of Brookfield Renewable’s Chilhowee Dam, located on the Little Tennessee River, in Tallassee, TN.  The 75 foot high and 300 foot long North Embankment has an upstream sloping thin clay core, with multiple upstream and downstream filters protecting the core, and rockfill shells protecting the filters.  A series of subsurface investigations were performed, and identified an area of soft clay at the contact between the clay core and the concrete non-overflow structure, extending along the upstream face of the dam.  This paper describes the seepage modeling that was completed by WSP, on behalf of the owner, to quantify the volume of seepage that would be expected through the embankment, accounting for the apparent deficiencies near the abutment tie-in area.  The sensitivity analysis, including comparing the calculated flow through the embankment to the flow that would be expected through a structure of similar geometry without defect areas, is discussed, along the with considerations that were included within the Seep/W model to accurately model and predict the level of flow through the section.  The seepage model was used to accurately predict flow through the embankment during the eventual reservoir drawdown, as construction was performed to repair the embankment, and after the completion of repair work as the reservoir was raised to normal pool levels.

    Defect Seepage Modeling

    Bel Air Impoundment - Do All Dams Need A Drain?

    Tuesday May 01, 2018 1:30 PM - Tuesday May 01, 2018 3:00 PM

    • Joanna Scrafford, Gannett Fleming, Inc. ;
    • Cari Beenenga, Gannett Fleming, Inc. ;
    • John Roche, MDE Dam Safety Division ;
    • Anthony Nokovich, American Water

    Maryland American Water is constructing an off-stream raw water storage impoundment adjacent to Winters Run, in Harford County, Maryland. The purpose of the Bel Air Impoundment is to provide the company with a reliable raw water supply source when water from other sources in the Bel Air system is not sufficient to meet demand.

    The 90-million-gallon pump-storage facility will consist of an earthfill dam embankment and impoundment, a riser structure, a water transmission pipeline, an intake structure and pumping station. The length of the embankment is 2,025 feet with a maximum height of about 61 feet. The impoundment bottom and upstream slopes of the embankment will be lined with an impervious bituminous membrane, placed directly on earth. The impoundment will have a surface area of 11.2 acres at normal pool. The Bel Air Impoundment is the largest new dam construction to be permitted in Maryland in approximately 30 years.

    Seepage analyses assuming conservative permeability parameters were completed to evaluate seepage flows in the embankment in case a liner imperfection would be of such magnitude that steady state conditions within the embankment develop. The calculated rate of seepage was considered low enough that an internal drain was not originally recommended; however, the Dam Safety Division of Maryland Department of Environment (MDE) recommended a toe drain be constructed in accordance with typical dam design practice.

    This paper presents aspects of the geotechnical analysis and design of the impoundment facility components, which include stability of the earthen embankment and geomembrane liner, filter diaphragm, and riser structure foundation.

    Bel Air Impoundment - Do All Dams Need A Drain?

    2A: Reservoir Sediment Management

    Review of the Reservoir Sedimentation Information (RSI) Database and Inventory of Known Sediment Issues at USACE Reservoirs

    Tuesday May 01, 2018 3:30 PM - Tuesday May 01, 2018 5:30 PM

    • Paul Boyd, US Army Corps of Engineers ;
    • Bryan Baker, US Army Corps of Engineers ;
    • Rachel Schultz, US Army Corps of Engineers

    Since 2014, the US Army Corps of Engineers' Response to Climate Change Program has been compiling sediment surveys for the over 400 reservoir projects in the Civil Works Inventory. The historical surveys have been centralized in a database and reviewed by districts for accuracy. In 2017, an additional project was initiated to determine the scope of known sedimentation impacts at these reservoirs. This second project, completed by the Corps' Regional Sediment Management (RSM) Program, inventories sediment issues and concerns at each reservoir, ongoing studies, and past and current actions taken to mitigate sedimentation impacts. This is the first comprehensive review of sedimentation impact at Corps reservoirs. Discussion will include an overview of the database, a summary of the most common sedimentation issues at reservoirs, and a review of the few sediment management actions being undertaken.

    Review of the Reservoir Sedimentation Information (RSI) Database and Inventory of Known Sediment Issues at USACE Reservoirs

    A Comparison of Reservoir Storage Capacity and Sediment Depletion

    Tuesday May 01, 2018 3:30 PM - Tuesday May 01, 2018 5:30 PM

    • Paul Boyd, US Army Corps of Engineers ;
    • Benjamin Ream, USACE Omaha District ;
    • Lawrence Morong, USACE Omaha District

    Abstract for the special track on reservoir sedimentation and sediment management:

    Reservoir storage capacity is a critical component of hydrologic dam safety analysis. Sediment depletion can have significant consequences on available storage. USACE Omaha District has been measuring reservoir storage and sediment depletion rates at many reservoirs within the District boundaries. In 2016, different survey methods consisting of single beam and multibeam hydrographic surveys, sediment range topographic surveys, and LiDAR surveys were performed at three reservoirs near Denver, CO. Sediment storage computations were performed using the data with the legacy sediment range method and GIS. The results of the different survey methods were compared to evaluate methods, cost, and variance between methods. Variation between methods was also evaluated based on reservoir pool zone, vegetation, and several other factors. Recommendations were developed for future reservoir survey and computation methodology within Omaha District.

    A Comparison of Reservoir Storage Capacity and Sediment Depletion

    Sediment Dredging of Reservoirs for Long-Term Sustainable Management

    Tuesday May 01, 2018 3:30 PM - Tuesday May 01, 2018 5:30 PM

    • Timothy Randle, U.S. Bureau of Reclamation ;
    • Stanley Ekren, Great Lakes Dredge & Dock Company, LLC ;
    • William Hanson, Great Lakes Dredge & Dock Company, LLC ;
    • Robert Ramsdell, Great Lakes Dredge & Dock Company, LLC

    The nation’s 90,000 dams and reservoirs are filling with sediment over time and sustainable sediment management solutions are needed to help preserve the water storage capacity. This capacity is critical for ensuring the stability and resiliency of water and energy supplies, flood risk management, and natural infrastructure (the networks of land and water that provide services to people) for much of the country. Dredging of sediment from reservoirs is one option for recovering or maintaining reservoir storage capacity, especially in cases where the reservoir cannot be drawn down for sediment management purposes. Recovery of water storage capacity lost to past decades of sedimentation would be most economically viable for small reservoirs where dredged sediment could be delivered to nearby disposal areas. Beneficial uses may offset some of the costs.

    Past decades of sedimentation would likely have to be accepted in large reservoirs, but a long-term program could be employed to maintain existing storage capacity by annually dredging the inflowing reservoir sediments. A long-term dredging program would likely have to deliver dredged sediments to the downstream river channel where they would have been naturally transported without the dam and reservoir.

    The design of a reservoir dredging program would have to consider the specific location and topography, sedimentation volume and grain size, reservoir depths, disposition of the dredged sediment, slurry pipeline length and alignment, permits, mobilization, and power for the dredge and pumps. The cost of dredging would have to be compared with the cost of other sediment management options, the cost of eventually losing the reservoir benefits, and the cost of dam decommissioning in the absence of sediment management.

    Sediment Dredging of Reservoirs for Long-Term Sustainable Management

    Three-Dimensional Evaluation of Bathymetric Change and Sediment Infill in a Hydropower Reservoir.

    Tuesday May 01, 2018 3:30 PM - Tuesday May 01, 2018 5:30 PM

    • Mark Velleux, HDR ;
    • James Hallden, HDR ;
    • Ruta Rugabandana, HDR ;
    • James Fitzpatrick, HDR

    Conowingo Dam is the last in a series of three hydropower dams on the Susquehanna River and located 10 miles upstream of Chesapeake Bay. Conowingo Pond, the reservoir behind the Dam, is the last impoundment before the River reaches the Bay. As part of efforts to assess water quality impacts, resource agencies hypothesized that sediment infill and corresponding bathymetric changes over time have altered sediment (and nutrient) transport through the Pond and have increased the potential for sediments to be scoured and exported to the Bay during high flow events. A three-dimensional hydrodynamic, hydrothermal, and sediment transport model was developed to simulate conditions for an 18-year period: 1997-2014. Emphasis was placed on Tropical Storm Lee in 2011 and other events because of concerns that changing bathymetric conditions within the Pond could increase sediment and nutrient export to Chesapeake Bay. The hydrodynamic model was forced using hourly flows and was evaluated using near-continuous water surface elevation measurements. The hydrothermal model was forced with a customized suite of regional and site-specific meteorological and thermal discharge data and was evaluated using data from a network of 19 stations where water temperature was regularly measured during 2010. Sediment transport model results were in close agreement with measured suspended sediment concentrations (SSC) and spatial patterns of measured bathymetric changes over time. Model results were subject to peer review and demonstrated that sediment transport within the Pond has not been altered as was hypothesized and that the potential for future scour has not appreciably changed.

    Three-Dimensional Evaluation of Bathymetric Change and Sediment Infill in a Hydropower Reservoir.

    2B: Earthquakes - Concrete II

    PREDICTING DAM RESPONSE TO SEISMIC LOADING CONDITIONS USING PERFORMANCE BASED TESTING

    Tuesday May 01, 2018 3:30 PM - Tuesday May 01, 2018 5:30 PM

    • Maggie Gelber, Harvey Mudd College

    PREDICTING DAM RESPONSE TO SEISMIC LOADING CONDITIONS USING PERFORMANCE BASED TESTING

    Margaret Gelber[1]

    Kristin Lie[2]

    Casey Gardner[3]

    Ziyad Duron, PhD[4]

    Larry Nuss, PE[5]

    Michael Likavec, PE[6]

    ABSTRACT

    Traditional seismic analyses of large concrete dams employ the use of sophisticated numerical models which are often not validated with experimental data. This paper presents a novel method of predicting dam response using the results of Performance Based Testing (PBT) which can be used to validate numerical models. The predicted response to an earthquake can provide owners with insights into a dam’s current state and its vulnerabilities during hazard loading conditions. This prediction is created by convolving the dam’s dynamic characteristics with the Shock Response Spectrum (SRS) of an earthquake over the entire seismic hazard range and accounts for three-dimensional behavior in the dam. The process is computationally efficient and can be repeated for any number of seismic events, even thousands, thereby creating a tool for identifying vulnerabilities of the dam to specific seismic loading characteristics.  The technique is applied to the ongoing evaluation of a large concrete dam, and several Intensity Measures (IMs) are used to characterize each earthquake used in the predictions. Various trends of the dam’s predicted response as a function of the IMs are calculated that provide insight into the dam’s overall performance that can monitor and track a dam’s condition over time.

    [1] De Pietro Fellow, Department of Engineering, Harvey Mudd College, Claremont, Ca. 91711, mgelber@g.hmc.edu

    [2] De Pietro Fellow, Department of Engineering, Harvey Mudd College, Claremont, Ca. 91711, klie@g.hmc.edu

    [3] De Pietro Fellow, Department of Engineering, Harvey Mudd College, Claremont, Ca. 91711, cgardner@g.hmc.edu

    [4] Jude and Eileen Professor of Engineering, Harvey Mudd College, Claremont, Ca. 91711, ziyad.duron@gmail.com

    [5] Principal, Nuss Engineering, LLC, Highlands Ranch, Co. 80129, Larry.K.Nuss@NussEngineering.com

    [6] Dam Safety Engineer, Puget Sound Energy, Michael.Likavec@pse.com

    PREDICTING DAM RESPONSE TO SEISMIC LOADING CONDITIONS USING PERFORMANCE BASED TESTING

    A SYSTEMS-BASED CHARACTERIZATION OF FOUNDATION INTERACTION EFFECTS IN CONCRETE DAMS

    Tuesday May 01, 2018 3:30 PM - Tuesday May 01, 2018 5:30 PM

    • Kristin Lie, Harvey Mudd College

    A SYSTEMS-BASED CHARACTERIZATION OF FOUNDATION INTERACTION EFFECTS IN CONCRETE DAMS

    Kristin Lie[1]

    Casey Gardner[2]

    Margaret Gelber[3]

    Ziyad Duron, PhD[4]

    Larry Nuss, PE[5]

    Michael Likavec, PE[6]

    ABSTRACT

    Performance Based Testing of concrete dams offers insight into their dynamic characteristics and provides information on their condition. The traditional method of predicting interaction effects between a dam and its foundation uses Finite Element Modeling to approximate the dynamic characteristics at the interface. This paper details a systems-based experimental approach to evaluate the dynamics of a concrete dam-foundation interface. Transient responses to an impulse load are acquired along the dam-foundation interface (DFI) and on the downstream face of the dam. These responses are analyzed in the frequency domain and a DFI curve is developed by determining the frequency response function between any set of input points and an output point. This method is highly versatile and can be adapted to adjust the dam’s predicted modal behavior over the frequency range of interest. Additionally, the relative contributions of resonant modes can be adjusted to model the dam’s damage states during a seismic event. The application of the DFI to an ongoing evaluation of a large concrete arch dam is presented.

    [1] De Pietro Fellow, Department of Engineering, Harvey Mudd College, Claremont, Ca. 91711, klie@g.hmc.edu

    [2] De Pietro Fellow, Department of Engineering, Harvey Mudd College, Claremont, Ca. 91711, cgardner@g.hmc.edu

    [3] De Pietro Fellow, Department of Engineering, Harvey Mudd College, Claremont, Ca. 91711, mgelber@g.hmc.edu

    [4] Jude and Eileen Professor of Engineering, Harvey Mudd College, Claremont, Ca. 91711, ziyad.duron@gmail.com

    [5] Principal, Nuss Engineering, LLC, Highlands Ranch, Co. 80129, Larry.K.Nuss@NussEngineering.com

    [6] Dam Safety Engineer, Puget Sound Energy, Michael.Likavec@pse.com

    A SYSTEMS-BASED CHARACTERIZATION OF FOUNDATION INTERACTION EFFECTS IN CONCRETE DAMS

    Direct FE Method for Nonlinear Earthquake Analysis of Concrete Dams: Simplification, Modeling and Practical Implementation

    Tuesday May 01, 2018 3:30 PM - Tuesday May 01, 2018 5:30 PM

    • Arnkjell Loekke, Norwegian University of Science and Technology ;
    • Anil Chopra, University of California, Berkeley

    Seismic risk analysis of concrete dams and design improvements to reduce risk require dynamic analysis procedures that include all factors known to be significant in earthquake response of dams. A direct FE method for nonlinear analysis of concrete dams that considers all such factors has recently been presented. This procedure overcomes the limitations of "standard" FE analysis, which often does not consider rigorously the semi-unbounded extent of the foundation rock and impounded water, nor an earthquake excitation consistent with the control ground motion defined at the ground surface.

    While the direct FE method is simple enough to be implemented with any commercial FE code without modifying the source code, it involves a substantial amount of data transfer and "book-keeping" to set up and store effective earthquake forces to be applied to the model boundaries. This paper will present several simplifications to the direct FE method that drastically reduces these book-keeping requirements without noticeable loss of accuracy, thus making its practical implementation much more attractive. Results of example analyses will be presented to demonstrate the accuracy and effectiveness of the simplified implementation.

    Damping in numerical models should be consistent with the damping "measured" at concrete dams during forced vibration tests and small earthquake events. Such measured values reflects the total energy dissipation in the system: material damping in the concrete and foundation rock, radiation damping in the semi-unbounded foundation and fluid domains, and absorption of hydrodynamic pressure waves in sediments at the reservoir boundaries. In contrast, damping in most numerical models is controlled by specifying only the material damping in the concrete and rock, which is inherently difficult to determine experimentally. A discussion on the proper selection of damping values, and why the practice of "blindly" specifying 5% viscous damping should be abandoned, will be presented.

    Direct FE Method for Nonlinear Earthquake Analysis of Concrete Dams: Simplification, Modeling and Practical Implementation

    Considerations Regarding Analysis Parameters for Two-Dimensional Nonlinear Seismic Response Analysis of a Concrete Gravity Dam

    Tuesday May 01, 2018 3:30 PM - Tuesday May 01, 2018 5:30 PM

    • Osmar Penner, BC Hydro ;
    • Jeff Yathon, BC Hydro ;
    • Brent Bergman, BC Hydro ;
    • Mina Shahbazi, BC Hydro ;
    • Soheil Razavi-Darbar, BC Hydro ;
    • David Queen, BC Hydro

    Previous research has demonstrated the influence of reservoir-foundation-structure (RFS) interaction on the dynamic response of concrete gravity dams, but this interaction has been difficult to capture in time domain analysis  using finite element (FE) implementations in traditional codes. The authors previously demonstrated a novel approach to capturing RFS interaction in the time domain using the analysis code LS-DYNA, with earthquake excitation applied by the effective seismic input method (ESIM) and perfectly matched layers (PML) used to represent the semi-infinite nature of the foundation and reservoir domains.


    This paper examines the sensitivity of the nonlinear seismic response of a concrete gravity dam to analysis parameters, based on 2D dynamic FE analysis using the ESIM/PML approach. The response is characterized in terms of the sliding displacement along concrete lift joints in the dam body. The effects of numerous parameters on the computed response are explored, including the height and stiffness of the dam section used in the analysis; the number, location, and slope of lift joints included in the model; and the initial bond strength, frictional resistance, and pore pressure at the lift joints. The effect of post-tensioned anchors on the seismic response is investigated. The findings illustrate the uncertainty associated with key parameters, and highlight the importance of developing a strong rationale at the onset of a project to set defensible parameter ranges.

    Considerations Regarding Analysis Parameters for Two-Dimensional Nonlinear Seismic Response Analysis of a Concrete Gravity Dam

    Nonlinear Seismic Analysis of an Arch Dam

    Tuesday May 01, 2018 3:30 PM - Tuesday May 01, 2018 5:30 PM

    • Gurinderbir Sooch, Hatch ;
    • Dan Curtis, Hatch ;
    • Toby Brewer, Tacoma Power

    A nonlinear seismic analysis of an arch dam under intense earthquake has been performed. A 3D finite element model was developed and the non-linear analysis was performed using the explicit finite element program LS-DYNA. The 3D finite element model includes the effects of dam-foundation-reservoir interactions. The non-linear concrete model was used to identify a curved failure plane in the dam. The non-linear concrete model has a serious drawback in that when cracking occurs during the earthquake, the element stiffness reduces substantially even when the crack is closed. Hence the post-cracking behavior simulated by the non-linear concrete is very conservative when used in a seismic analysis. Therefore, a work-around was developed whereby the failure surface identified using the concrete model was idealized with surface concrete elements which maintained friction strength in its cracked state. The results of the improved analysis are presented.  

    Nonlinear Seismic Analysis of an Arch Dam

    2C: Construction - River Diversions

    Addressing Site Specific Challenges by Staged Construction of the Red Rock Hydroelectric Project

    Tuesday May 01, 2018 3:30 PM - Tuesday May 01, 2018 5:30 PM

    • Rachael Bisnett, Stantec ;
    • Thomas Andrews, Stantec ;
    • Nathaniel Grossmann, Stantec

    Design and construction of the Red Rock Hydroelectric Project presents several unique challenges, particularly those related to the very confined work area, large reservoir water surface elevation and spillway release fluctuations, unbalanced soil loading associated with the dam’s steep slopes, the requirement that all work be carried out with no impact to the USACE’s water control and reservoir operations, and the prime importance of maintaining the integrity of the existing dam.

    As a mitigation measure for many of the construction challenges, Stantec (previously MWH) developed construction sequence drawings to prescribe the staged construction of the project. The construction sequence considered the project’s identified construction challenges and staged the upstream and downstream work in a manner that maintains dam safety throughout construction. A total of nine discrete construction stages were specified for the upstream work and seven stages were specified for the downstream work. The construction sequence was developed and coordinated with the design of the cofferdams, braced excavations, and other temporary structures that were required to construct the permanent works.

    Addressing Site Specific Challenges by Staged Construction of the Red Rock Hydroelectric Project

    Cellular cofferdams as permanent hydropower dam structures

    Tuesday May 01, 2018 3:30 PM - Tuesday May 01, 2018 5:30 PM

    • Simon Heru Prassetyo, Colorado School of Mines ;
    • Marte Gutierrez, Colorado School of Mines

    This paper presents the results of a comprehensive study on the potential use of cellular cofferdams as basis for the design and construction of water retaining structures to sustainably and cost-effectively harness hydropower. Previously, cellular cofferdams have been widely used mainly as temporary water exclusion devices to permit dry construction of in-water structures such as dams, locks, bridge footings and piers, and hydroelectric power plants. Design and construction requirements for cellular cofferdams are less stringent than for hydropower dams. To make cellular cofferdams suitable for permanent hydropower use, different design concepts that utilize cellular cofferdams as the main or core element of the water-retaining dam structure are proposed. One particular key design concept is the so-called “dry construction technique” in which the granular fill in cofferdam cells and the downstream berm are permanently kept dry in contrast to the wet construction technique for temporary use of cellular cofferdams. The viability of the proposed permanent cellular cofferdam design concepts is demonstrated using well-established structural and geotechnical design procedures and computational modeling. The improved performance of the proposed design concepts, particularly in combination with the dry construction technique, show cellular cofferdams have the potential to be used as basis for the construction of permanent hydropower dam structures that are versatile, with less impact on the environment, and will cost less to build than conventional hydropower dams.

    Cellular cofferdams as permanent hydropower dam structures

    NOT GIVING UP HOPE – THIRD TIME’S THE CHARM WITH HOPE MILLS DAM

    Tuesday May 01, 2018 3:30 PM - Tuesday May 01, 2018 5:30 PM

    • Corey Schaal, Schnabel Engineering ;
    • Mark Landis, Schnabel Engineering ;
    • Aaron Collins, Schnabel Engineering

    The original Hope Mills Dam, located in southeastern North Carolina, was constructed in the late 1830s to provide power to four nearby cotton mills.  The dam was breached and rebuilt between 1923 and 1924.  The second dam overtopped in 2003.  A third dam was constructed five years later, but in 2010, it failed as well.  The design-build team, which was selected in 2014, elected to remove the remains of the 2008 structure and build a new dam and labyrinth spillway.  The foundation was excavated to firm natural soils.  A slurry seepage cut-off wall was installed beneath the labyrinth structure and across the earth tie-outs, and the embankment sections contain a low-permeability core consisting of both natural cohesive soils and less cohesive soils blended with bentonite.  Use of on-site resources was emphasized to meet project and budget goals, including the mixed-in-place slurry wall, concrete rubble from demolition of the old spillway for access roads and wave protection, screened borrow material from the reservoir, and reclaimed core material.  Because all stream flows are channeled through a narrow corridor just downstream of the structure, stream diversion phasing proved to be challenging.  During construction, the storms that pummeled the southeast U.S. in September/October 2016 generated events estimated to be equal to the 100-year flood and, 10 days later, the 500-year flood at the site.

    NOT GIVING UP HOPE – THIRD TIME’S THE CHARM WITH HOPE MILLS DAM

    The Life and Death of TED (the temporary embankment dam at the new Folsom Dam auxiliary spillway)

    Tuesday May 01, 2018 3:30 PM - Tuesday May 01, 2018 5:30 PM

    • Jeffrey Wisniewski, HDR ;
    • Jeffrey Allen, HDR

    Schedule constraints and agency objectives compelled innovative design and sequencing for the construction of the new auxiliary spillway at Folsom Dam in Folsom, California. Originally anticipated to be complete in 2015, an inter-agency task force (comprising representatives from USACE, USBR, DWR and SAFCA) was convened in 2011 when the expected completion date was pushed to 2021 or later. Construction sequencing alternatives and acquisition strategies were evaluated to balance construction risk and project objectives, including completion by the start of the 2017-2018 wet season to expedite delivery of the project’s flood risk management and dam safety benefits. 

    Overlapping two construction contracts (approx. $600 million in combined value) on the same project site and utilizing an “in-the-wet” excavation approach of the existing rock plug dam, consisting of terrestrial and underwater blasting and dredging techniques, was determined to be the best opportunity to realize the project’s flood protection benefits four years earlier. An engineered, instrumented temporary embankment dam (TED)—incorporating an approximately 1,200-foot-long, 100-foot-deep secant pile seepage cutoff wall—was designed and constructed to facilitate simultaneous construction of the control structure (already underway) and excavation of the upstream approach channel. TED would maintain all dam safety criteria until the control structure was functional—removing the control structure from critical path—while also positioning the project for the potential upside of lower than average water levels. 

    The paper will describe dynamic and challenging agency objectives and their impacts on project decisions, alternatives evaluations and considerations, design and construction of TED and its performance as a key project feature, contractor innovation, subsequent cofferdams constructed to further advance dry excavation (including a seepage event that triggered the first filling of the new control structure), and the effects of a historic drought on the project.

    The Life and Death of TED (the temporary embankment dam at the new Folsom Dam auxiliary spillway)

    Design and Construction of the New Folsom Dam Auxiliary Spillway Approach Channel

    Tuesday May 01, 2018 3:30 PM - Tuesday May 01, 2018 5:30 PM

    • Erik Newman, AECOM ;
    • Michael Forrest, AECOM ;
    • Michael O'Sullivan, COWI ;
    • Kylan Kegel, US Army Corps of Engineers ;
    • Kenneth Pattermann, US Army Corps of Engineers ;
    • Jeffrey Wisniewski, HDR

    The Folsom Dam Auxiliary Spillway Joint Federal Project was undertaken to increase the spillway capacity of Folsom Reservoir in order to meet the demands imposed by an updated assessment of the probable maximum flood.  The auxiliary spillway consists of an approach channel from the reservoir, a control structure, and a spillway chute and stilling basin that discharge spillway flows into the American River downstream of the existing spillway. Staged construction allowed the spillway to be completed without impacting operation of Folsom Reservoir.

    A cofferdam including a temporary embankment and seepage cutoff wall reduced construction risk but required excavation in-the-wet. Consideration of rock slope stability and hydraulic performance was required in developing the grading of the approach channel, the adjacent reservoir shoreline, and geometry of the approach walls upstream of the gated control structure.  Slope protection was designed for the erodible materials taking into account flow velocities during operation of the emergency spillway as well as wind and wave effects.

    Excavation of the approach channel was planned to be a combination of excavation in-the-dry and marine work from barges, with the relative quantities of each depending on reservoir level during construction.  Low lake levels during construction resulted in the majority of the hard-rock excavation occurring in the dry, with only a small amount of excavation and cleanup of the final surface needing to be performed from barges.  Placement of the erosion protection on the slope also benefited from the low lake levels as well as from a construction technique that allowed for top-down placement as the excavation progressed instead of from the bottom up after the excavation was complete.

    Substantial completion of the project was achieved in late 2016 with final site restoration and commissioning activities extending into 2018.

    Design and Construction of the New Folsom Dam Auxiliary Spillway Approach Channel

    Ensuring Dam Safety without a Spillway during Construction at Anderson Dam

    Tuesday May 01, 2018 3:30 PM - Tuesday May 01, 2018 5:30 PM

    • Chuck Anderson, Schaaf & Wheeler ;
    • Brian Gettinger, Black & Veatch ;
    • Jack Xu, Santa Clara Valley Water District ;
    • Victor Gutierrez, Santa Clara Valley Water District ;
    • Emily Schwartz, Black & Veatch

    Although built and operated solely for water supply, Anderson Reservoir provides significant flood protection benefits along Coyote Creek to the Cities of Milpitas, Morgan Hill and San Jose, California. The Anderson Dam Seismic Retrofit Project (ADSRP) will require the removal and replacement of the entire earth fill shell material and the majority of the clay core to ensure seismic stability. During construction the spillway will not be operable and all inflow into the reservoir must be diverted through a diversion tunnel with downstream flow control.

    Managing California’s wet and dry seasonal weather patterns, ensuring the interim embankment is not overtopped during construction, and reducing downstream impacts along Coyote Creek without use of a spillway require a thorough analysis of potential storm events and their impact on the reservoir during construction. Additionally, as the embankment must be replaced in-place, construction of a large cofferdam is not practical.

    Because most historical rainfall and runoff records are relatively limited, a stochastic model can be applied to better estimate the reliability of a reservoir. From a historical record at a precipitation gage, a Markov Chain Monte Carlo approach can be applied to develop an extended, realistic time series that preserves gage statistics. When combined with a calibrated rainfall-runoff routing model, this stochastic approach provides the basis for reliability assessment of Anderson’s interim dam and outlet structure and the creation of operating rule curves for winter construction.

    Ensuring Dam Safety without a Spillway during Construction at Anderson Dam

    2D: Foundations

    Mosul Dam -- An Epoch in the Making

    Tuesday May 01, 2018 3:30 PM - Tuesday May 01, 2018 5:30 PM

    • Dave Paul, U.S. Army Corps of Engineers ;
    • Juan Vargas, AECOM ;
    • Nagesh Malyala, AECOM ;
    • NatishAhmed Abdallah, Iraq Ministry of Water Resources

    Mosul dam, a 3.2 km earth fill dam, located in Northern Iraq is one of the largest multi-purpose dams in the Middle-East. The dam is located on extremely problematic geologic foundation that is karstic in nature and has potential to erode due to the presence of dissolvable gypsum layers. The gypsum could dissolve and form interconnecting openings in the foundation that could compromised the stability of the dam. This issue has been addressed by maintenance grouting over the years. However, the deteriorating foundation of the dam poses a risk that if not addressed immediately, could result in catastrophic loss of life, economic damage, and geopolitical instability. The use of modern day grouting practices and technology is essential to address the problem in the essence of time.

    This paper discusses the technology, grout mixes, grouting methodology, equipment, computer-based monitoring systems, currently in use. The paper also discusses how technology is being used to address the aggressive schedules, production and intensity of the grouting effort and socio-political conditions.

    Mosul Dam -- An Epoch in the Making

    Mosul Dam Grounting: Listening to the Telltale Signs of the Ground

    Tuesday May 01, 2018 3:30 PM - Tuesday May 01, 2018 5:30 PM

    • Dave Paul, U.S. Army Corps of Engineers ;
    • Matt Sheskier, U.S. Army Corps of Engineers ;
    • Juan Vargas, AECOM ;
    • Nagesh Malyala, AECOM

    Mosul dam is one of the largest multi-purpose dams in the Middle-East. The dam provides the much needed water resource to Iraq and addresses its water and irrigation supply, flood risk management, hydro power generation, recreation and environmental benefits.   The 3.2 km earth fill dam is located on problematic geologic foundation is posing extremely high risk to the population, economy and water resources of Iraq, needing immediate action to reduce the risk.

    The foundation of the dam consists of the multiple layers of gypsum/anhydrite that are soluble in nature. Dissolution of these layers could result in stoping of the embankment material into the foundation and pose significant dam safety risk. Maintenance grouting has been undertaken since the construction of the dam, from the 3 meter wide grouting gallery at the base of the dam along the centerline.

    The current grouting operation has thrown wide range of challenges due to the problematic geologic foundation. The highly broken F-Bed layers posed significant threat to keep the grout holes open. Multiple layers of Gypsum/Anhydrite are found at varying depths along the foundation. The vuggy limestone/marl layer present over the Gypsum/Anhydrite varied in thickness along the dam and exhibited different characteristics.

    The current technical paper discusses the section by section based grouting approach implemented based on the how the foundation manifested the characteristics of geology and philosophy behind the chosen approach.

    Mosul Dam Grounting: Listening to the Telltale Signs of the Ground

    Final Results of 3D Geologic Modeling at Boundary Dam: from Abutment Stability to Rock Block Stabilization

    Tuesday May 01, 2018 3:30 PM - Tuesday May 01, 2018 5:30 PM

    • Robert Cannon, Schnabel Engineering ;
    • Fred Snider, Schnabel Engineering ;
    • Kimberly Pate, Seattle City Light ;
    • Andre Ball, Seattle City Light ;
    • J.Hawkins Gagnon, Schnabel Engineering

    Seattle City Light’s Boundary Dam is a 340-foot high double curvature concrete arch in a steep, narrow canyon in northeastern Washington founded on Metaline Limestone. Original site explorations included over 100 borings, 700 packer tests, and several adits to support design and construction of the dam, large underground powerhouse, the forebay, penstocks, draft tubes and extensive access and diversion tunnels. Recent work at the dam includes laser scanning of both aboveground and underground areas, development of high-resolution point clouds, and LiDAR imaging of the dam and entire reservoir.

    Rock bolting of large potential slide blocks and underground excavations was completed during construction and later. However, continued concerns over the stability of the steep rock face on the right abutment and the lack of an integrated understanding of the site geology prompted development of a computer-based, 3D geologic model. The model integrates the recent point cloud data with all the original exploratory borings, geologic maps, and information gleaned from an extensive library of construction photographs.

    The model allows clear 3D visualization of the spatial relationship of the rock types, through-going joint planes, topography, and the numerous project excavations and constructed features. The right abutment was given specific attention, and the geometries and possible release planes for large, potentially removable blocks near the dam were well defined in the 3D geologic model. The visualizations and associated stability analyses demonstrated little risk to the dam. However, the work did lead to concerns regarding the stability of a bridge from the dam face to a pier founded on the right abutment. Field work, updating the 3D model, and stability analyses led to the decision to stabilize the pier foundation with cable lashing and anchors. This project clearly demonstrates the value of a 3D geologic model as a visualization, interpretive and communications tool.

    Final Results of 3D Geologic Modeling at Boundary Dam: from Abutment Stability to Rock Block Stabilization

    A Comparison of Barrier Wall Types and Methods for Controlling Seepage through Embankment Dams and Levees

    Tuesday May 01, 2018 3:30 PM - Tuesday May 01, 2018 5:30 PM

    • Joseph Kula, Arcadis ;
    • Gianfranco Di Cicco, GDConsulting, LLC ;
    • Timothy Newton, Arcadis

    Uncontrolled seepage is a common problem associated with many existing embankment dams and levees, resulting in high pore pressures and seepage forces that can lead to internal erosion or "piping" through the embankment or foundation, uplift at the dam or levee’s downstream toe, and slope instability. Low-permeability barriers are one important technique for remediating uncontrolled seepage. This paper discusses the history of barrier wall construction and the current state of the practice, and compares the various types of barrier walls and construction techniques.

    Barrier walls are typically used to reduce seepage quantities, gradients, and piezometric pressures downstream of the wall. There are a variety of methods available for construction of barrier walls, each with applications and conditions for which they are best suited and with advantages and disadvantages. Current barrier wall construction methods can generally be divided into four broad categories:

    • Continuous barrier walls: Soil-bentonite, cement bentonite, and soil-cement-bentonite slurry walls (or slurry trench).
    • Element barrier walls: Rectangular overlapping panels excavated using various excavation techniques and secant pile walls consisting of overlapping circular elements.
    • Mixed-in-place barrier walls: Soil mixing methods and jet grouting techniques.
    • Grouted barriers: Grout curtains techniques.

    This paper describes the current construction techniques used for barrier wall construction, and how a range of factors influence the selection process when evaluating the most appropriate methodology for a given site. These influencing factors include but are not limited to: topography, geology and foundation conditions, embankment materials, seepage characteristics, depth of required remediation, and project logistics/accessibility. The conditions favoring the various methods are discussed as well as the advantages and disadvantages of each method in terms of applicability to site conditions, effective remediation depth, durability, efficiency, dam safety requirements, constructability, quality control, long-term risks, environmental considerations, permitting concerns and relative cost.

    A Comparison of Barrier Wall Types and Methods for Controlling Seepage through Embankment Dams and Levees

    Large slope and foundation stability problems of three dams

    Tuesday May 01, 2018 3:30 PM - Tuesday May 01, 2018 5:30 PM

    • Camilo Marulanda, INGETEC

    This article presents three case histories were large slope instabilities problems occurred during construction of two concrete and one rockfill dam. A brief summary of the origin of  metamorphic rocks and the presence of shear or gouge zones in these rocks is presented. These shear zones represent weaknesses of the rock mass and depart substantially from the traditionally evaluation of joints and discontinuities, turning eventually into failure surfaces that govern the stability conditions of surface works. The effect these weak zones inflict into the metamorphic rock mass, especially to schist, causing significant slope stability problems, is illustrated through three case histories of hydroelectric projects. The presence of such defects in the rock mass, detected and analyzed by means of exploratory holes drilled from the surface, can be hardly anticipated during the design stage. The difficulty can be associated with the unpredictable location, dip direction and geotechnical characteristics within the rock mass. In addition their disguise during the drilling processes when the clay infill is washed away by the drill water, making their recognition and field collection of samples for laboratory testing even more difficult. Special care in terms of geotechnical characterization of these geologic features must be taken through: 1) direct exploration –such as galleries–, 2) the elaboration and interpretation of adequate geological models and corresponding sensitivity analyses of shear strength parameters of the established failure surfaces and 3) sound decision making and implementation of stabilization measures based on engineering judgment.

    Large slope and foundation stability problems of three dams

    CHALLENGES & LEARNINGS IN EXECUTION OF SPILLWAY FLIP-BUCKET-A CASE STUDY OF KOLDAM HEP

    Tuesday May 01, 2018 3:30 PM - Tuesday May 01, 2018 5:30 PM

    • Vinod Kumar Mauriya, NTPC LIMITED (GOVT OF INDIA E/P) ;
    • Prashant Narayan Gaur, NTPC LIMITED (GOVT OF INDIA E/P)

    The Koldam HPP(4x200MW) located on river Satluj, utilizes a drop of about 140 meters by constructing a 167 m high rock & gravel fill Dam with impervious central clay core and having surface power station at the toe of the dam, housing 4 vertical Francis turbines of 200 MW each. During execution of the project, at Flip-bucket location of Spillway, the black carbonaceous slate was encountered. This was not suitable for founding the Spillway Flip-bucket. Mid-course correction was necessitated to ensure the structure meets its intended purpose for the designed life. The objective of the present paper is to present the case study of the challenges encountered with learning's due to geological changes/ surprises and design modifications done in Spillway Flip-bucket and associated structures during execution stage.

    Detailed geological investigations have been performed during execution. Only the coring done with a triple barrel tube has given an acceptable core recovery. The results have shown that the black carbonaceous slate/ basic dyke contact is located at El. 534 on the left bank of the chute. With regard to the geology encountered, the design of flip bucket was revised by shifting the flip bucket by approximately 32m downstream from the initial location. The black carbonaceous slates was excavated upto 5m depth and backfilled the same with concrete so that the chute slab at this location can be founded on this backfill concrete. Due to relocation of flip bucket during execution of spillway, modifications in associated plunge pool structure also necessitated and accordingly the same was also redesigned.

    In spite of the various challenges & surprises encountered during execution of the Spillway Flip-bucket, the construction of the same was successfully done and structure has efficiently performed during operation.

    CHALLENGES & LEARNINGS IN EXECUTION OF SPILLWAY FLIP-BUCKET-A CASE STUDY OF KOLDAM HEP

    Comparison of Measuring Effective Grouting Pressures

    Tuesday May 01, 2018 3:30 PM - Tuesday May 01, 2018 5:30 PM

    • Dmitri Ivanov, Advanced Construction Techniques ;
    • Michael Xu, Advanced Construction Techniques

    The development of down-the-hole tools that are able to monitor injection pressures has evolved in the last several years. The primary utilization of this new technology is related to pressure grouting of earthen dams and levees. Measuring pressure at the point of injection, has successfully mitigated hydraulic fracturing of embankments and rock zones. During the Exploratory Drilling and Grouting Program at the USACE Rough River Dam, effective injection pressure was monitored both at the collar of the hole, as well as, at the point of injection.

    This paper will compare two methods of calculating effective injection pressures while grouting. The first method, in use for a long time, measures pressure at the collar of the hole, and establishes effective injection pressure through a series of calculations, such as dynamic line losses. The second method, used with the development of down-the-hole tools, measures injection pressure directly at point of injection. This paper will, furthermore, compare how accurately dynamic line losses can be related to the determination of effective grouting pressures.

    A number of preliminary results, suggest that one of the key advantages of measuring down-the-hole pressure is eliminating false refusals. False refusals occur when line losses at thicker viscosity grout mixes contribute a greater effect on the effective pressure calculation than during line loss testing at the beginning of the project. This paper will summarize all the findings of the injection data collected and make recommendations related to pressure grouting with this point of injection technology.

    Comparison of Measuring Effective Grouting Pressures

    2E: Dam Safety I

    Using Semi-Quantitative Risk Assessment to Allow Safe Storage in a Reservoir

    Tuesday May 01, 2018 3:30 PM - Tuesday May 01, 2018 5:30 PM

    • Jessie Drayton, AECOM ;
    • Warren Wade, Fort Carson Directorate of Public Works ;
    • Andrew Barry, USACE Omaha District ;
    • Don Poulter, AECOM

    An earthen embankment dam with an uncontrolled earth cut spillway is classified as large and high hazard due to downstream population at risk for both state and federal criteria. However, due to concerns about inadequate spillway capacity and seepage through the abutments, the reservoir has been operated with a zero storage restriction since April 2014. A Semi-Quantitative Risk Assessment approach was utilized to identify risk driving potential failure modes at the dam and compare possible risk reduction measures in order to reduce the risk at the dam and lift the zero storage restriction. This paper will discuss the key findings of the study as follows:

    • Issues driving the risk at the dam include seepage through the dam abutments, inadequate emergency spillway capacity to pass the design flood, and downstream land development.
    • Two measures were developed by the team to address overtopping and nine measures were developed to address internal erosion into the abutments. Utilizing combinations of the measures, nine Alternative Risk Management plans were evaluated and compared to select one preferred plan.

    Using Semi-Quantitative Risk Assessment to Allow Safe Storage in a Reservoir

    Remote Sensing Inventory of Previously Undocumented Dams

    Tuesday May 01, 2018 3:30 PM - Tuesday May 01, 2018 5:30 PM

    • Dan Schmutz, Greenman-Pedersen, Inc. ;
    • Danny Goodding, Greenman-Pedersen, Inc. ;
    • Valerie Hrabal, Greenman-Pedersen, Inc. ;
    • Art Sengupta, Florida Department of Environmental Protection

    The Florida Department of Environmental Protection (FDEP) Dam Safety Program plays a vital role in preventing loss of life and property damage due to dam failures by maintaining an accurate database of over 1,200 non-federal dams located in Florida. This database, containing information about each dam’s location, size, and other technical data, is continually updated to include previously undocumented dams. The current availability of high-resolution Digital Elevation Models and digital aerial orthoimagery covering most of Florida provides an excellent opportunity to perform rapid, cost-effective dam inventories. Greenman-Pedersen, Inc. (GPI) assisted the FDEP with detecting and gathering basic inventory data on dams occurring within the 16 counties of the Southwest Florida Water Management District and within 10 counties of the St. Johns River Water Management District. GPI identified previously-unknown dams for a more than 17,000 square-mile area of peninsular Florida. This update was accomplished by reviewing readily-available topographic data, digital databases, and digital aerial orthoimagery in the ArcGIS environment. GPI conducted on-screen visual assessments of each of the 3,073 water bodies larger than 20 acres represented in the National Hydrography Dataset (and their downstream drainageways) using hydro-flattened DEMs prepared from LiDAR data. DEMs were symbolized to highlight rapid elevation changes between adjacent lakes and along associated streams and canals. Previously-known dams represented as point locations encountered during the search were assessed for spatial location accuracy using orthoimagery. A total of 183 previously-unknown dams of various types were documented, including: salinity barriers, concrete fixed weirs, earthen berms, and operable structures. Key attributes were estimated remotely using GIS methods, including: latitude, longitude, dam crest elevation, dam shape, impounded surface area, and maximum storage volume. Deliverables were provided in ESRI geodatabase and shapefile formats, with appropriate metadata.

    Remote Sensing Inventory of Previously Undocumented Dams

    Evaluating Leakage Through the Rock-Filled Juranah Dam

    Tuesday May 01, 2018 3:30 PM - Tuesday May 01, 2018 5:30 PM

    • Kirk Lowery, Arcadis, U.S, Inc.

    The Juranah reservoir is an earthen embankment located near Wadi Fatima about 25 kilometers northeast of the City of Makkah, Saudi Arabia. The reservoir is approximately 350 meters by 150 meters at the higher perimeter elevations. The embankment was built in a natural land construction and has a capacity of approximately 600,000 cubic meters. The top elevation for the water surface is 469 m and the lowest storage elevation is at elevation 443 m. The dam was originally constructed in 1977 using the sand and rock extracted on the upland side of the reservoir. A roof composed of two rows of 8 concrete columns were founded in the existing base rock of the reservoir and beneath the earthen embankment in 1983.

    The reservoir is covered with 10 centimeters of asphalt and a 2.5-millimeter (mm) High Density Polyethylene liner. Water discharges through a 2,000-mm pipeline that is housed in a tunnel located beneath the dam. Since the construction of the reservoir, leakage through the dam has been noted and several projects have been completed in unsuccessful attempts to stop the leakage. The National Water Company contracted with EC Harris Saudi Arabia International LLC, an Arcadis Company, to recommend alternatives to stop the leakage.

    After reviewing previous reports, inspecting the dam and reservoir, testing the HDPE liners, geophysically testing the existing dam, and evaluating the earthen dam’s and roof’s structural capability, Arcadis determined leakage occurs from the existing columns on the dam’s interior slope then conveys across the top of the tunnel to the exterior slopes. Cracking of asphalt around the columns placed within the dam has been speculated to have occurred due to settlement of the combined embankment and roof loads, and exacerbated by water flow along the seepage path.

    Evaluating Leakage Through the Rock-Filled Juranah Dam

    Risk Informed Design of Large Concrete (RCC) Dams in High Seismic Hazard Region

    Tuesday May 01, 2018 3:30 PM - Tuesday May 01, 2018 5:30 PM

    • Keith Moen, HDR Engineering, Inc. ;
    • Dan Osmun, HDR Engineering, Inc. ;
    • Farzad Abedzadeh, HDR Engineering, Inc. ;
    • Scott Anderson, HDR Engineering, Inc.

    Over the past 20 years, the seismic hazard associated with the Cascadia Subduction Zone (CSZ) located off the coasts of Oregon, Washington, and the northern part of California has been extensively studied and characterized. These studies have shown the potential for M9 earthquakes generating very strong ground motions (peak ground acceleration’s – pga’s in excess of 1.2 to 1.5 g’s) and nearly unprecedented durations of strong ground shaking (200 to 400 seconds). Major existing dams and potential new dams in the region must be designed to withstand the seismic hazard associated with the CSZ. This paper will review the risk informed designs underway for three new concrete gravity (RCC) dams that are located in the CSZ hazard region. These dams range from 100 to over 340-feet high and will store strategic water supplies. The three dams are under the jurisdiction of the State of Washington, the State of Oregon, and the U.S. Bureau of Reclamation. A risk informed and tiered basis of design has been developed in order to meet appropriate Federal and state dam safety guidelines while minimizing total project costs and risks. A comprehensive appraisal level risk analysis has been performed on one of these projects to verify that he tiered basis of design is acceptable according to Federal Public Protection Guidelines.

    Risk Informed Design of Large Concrete (RCC) Dams in High Seismic Hazard Region

    Balancing Risk and Resource Values at Grama Dam & Comanche Dam

    Tuesday May 01, 2018 3:30 PM - Tuesday May 01, 2018 5:30 PM

    • Andrea Fasen, W. W. Wheeler & Associates, Inc. ;
    • Steve Jamieson, W. W. Wheeler & Associates, Inc. ;
    • Todd Lewis, W. W. Wheeler & Associates, Inc. ;
    • Brad Iarossi, U.S. Fish & Wildlife Service, Dam Bridge and Seismic Safety Branch ;
    • Christine Mugele, W. W. Wheeler & Associates, Inc. ;
    • Audrey Coy, U.S. Fish & Wildlife Service, Dam, Bridge, and Seismic Safety Branch

    Grama Dam and Comanche Dam are located on the Wichita Mountains Wildlife Refuge in southwestern Oklahoma.  Both dams were constructed by the Civilian Conservation Corps in 1936 and 1934, respectively.  Grama Dam is a 43-foot-high, zoned embankment dam and Comanche Dam is a 38-foot-high, concrete gravity dam located one mile downstream of Grama Dam.  Currently, both are classified as high hazard dams owned and operated by the U.S. Fish & Wildlife Service (FWS).

    This paper provides a brief history of the construction and subsequent modifications of the dams based on the evolution of federal dam safety policy and analysis tools since the 1970s.  Current federal dam safety policies were tested in 2015 when a near-PMP event occurred in some areas of the Refuge, prompting the owner’s decision to consider further risk and hazard reduction measures at the dams while balancing resource values with the cost of risk reduction measures. Reservoir resource values at Grama Dam and Comanche Dam include wildlife habitat, fire protection and downstream floodplain management.  The paper also briefly describes the advanced HEC-HMS hydrologic modeling, two-dimensional HEC-RAS hydraulic modeling and GIS post-processing techniques used to simulate and evaluate the effects of the alternative risk reduction measures considered.  A simple decision support model was developed and used by the FWS to determine the preferred alternative for dam modifications that best balanced the resource values provided by the reservoirs with the proposed risk reduction modifications. The preferred alternative was selected by the FWS early in 2018.

     

    Balancing Risk and Resource Values at Grama Dam & Comanche Dam

    South Bay Seismic Retrofits: Project Updates

    Tuesday May 01, 2018 3:30 PM - Tuesday May 01, 2018 5:30 PM

    • Megan Puncke, Black & Veatch ;
    • Patrick Allen, Black & Veatch ;
    • Victor Gutierrez, Santa Clara Valley Water District ;
    • Bal Ganjoo, Santa Clara Valley Water District

    The Santa Clara Valley Water District (District) provides the supply of clean, safe water, flood protection and stewardship of streams on behalf of Santa Clara County’s 1.9 million residents. The District operates 10 reservoirs, which were constructed from the 1930s to the 1950s, primarily to provide water supply for the region. The District’s total storage capacity of their reservoirs is approximately 170,000 acre-feet.

    In addition to water supply these reservoirs provide some flood protection to downstream communities as well as recreational facilities for the public. Seismic stability evaluations of several of the District’s dams were initiated as part of the District’s Dam Safety Plan issued in 2005. During the seismic stability evaluations, three of the dams were found to be seismically deficient: Anderson Dam, Calero Dam, and Guadalupe Dam. As such, the District put in place water level restrictions at each of these dams, which reduced the District’s overall water storage capacity by approximately 25%. Seismic Retrofit Projects were initiated in 2012 for each dam.

    The planning phases for each project are complete and design is on-going for the selected design alternatives, with construction currently planned to start in 2020. This paper will discuss the major project components, and the current project status and schedule for each of these major infrastructure projects.

    South Bay Seismic Retrofits: Project Updates

    2F: Levees I

    Characterizing the Reliability of Earthen Levees using System Response Curves Derived from Uncertainty Analysis of Geotechnical Simulation Models

    Tuesday May 01, 2018 3:30 PM - Tuesday May 01, 2018 5:30 PM

    • Martin Schultz, Environmental Laboratory, Engineer Research and Development Center, US Army Corps of Engineers ;
    • Fred Tracy, Information Technology Laboratory, Engineer Research and Development Center, US Army Corps of Engineers ;
    • Ghada Ellithy, Geotechnical and Structures Laboratory, Engineer Research and Development Center, US Army Corps of Engineers ;
    • Danny Harrelson, Geotechnical and Structures Laboratory, Engineer Research and Development Center, US Army Corps of Engineers ;
    • Jodi Ryder, Environmental Laboratory, Engineer Research and Development Center, US Army Corps of Engineers ;
    • Maureen Corcoran, Geotechnical and Structures Laboratory, Engineer Research and Development Center, US Army Corps of Engineers

    System response curves (SRCs) are functions that describe the probability that a structure will satisfy predetermined criteria for being in a failure state given a load on the system. SRCs are valuable tools for characterizing and communicating information about structural reliability. This presentation will describe how SRCs for underseepage, through-seepage, and slope stability have been derived from uncertainty analysis of two models, SEEP2D-HPC and SLOPE2D-HPC. SEEP2D-HPC is a steady-state finite element model for seepage analysis designed to run on the Engineer Research and Development Center’s (ERDC’s) high performance computer (HPC). SLOPE2D-HPC locates the circular failure surface and performs slope stability analysis using the simplified Bishop method. Parameters describing soil properties, such as hydraulic conductivity and strength parameters, are treated as uncertain variables while the geometry of each two-dimensional levee section is held constant. The SRCs are derived from an efficient Monte Carlo simulation procedure. The potential uses of SRCs will also be discussed. SRCs can be used to provide an objective and quantitative assessment of structural reliability, can serve as inputs to flood risk models, and are important components of probabilistic models to support asset management decisions.

    Characterizing the Reliability of Earthen Levees using System Response Curves Derived from Uncertainty Analysis of Geotechnical Simulation Models

    Critical Pool Level for Drawdown Analysis of Earth Embankment Dams

    Tuesday May 01, 2018 3:30 PM - Tuesday May 01, 2018 5:30 PM

    • Krishna Shadakopan, Arcadis ;
    • Joseph Kula, Arcadis

    Rapid drawdown is one of the critical loading conditions that should be evaluated for dam safety requirements. For earth embankment dams, this loading condition becomes critical when a submerged slope experiences rapid reduction/loss of external water support while pore-water pressures within the embankment remain high. There are two commonly used approaches in practice to evaluate the drawdown slope stability even though some aspects of these methods have concerns or limitations and are still researchable: single-stage method generally with drained strength parameters; multi-stage method with drained/undrained strength parameters. With both methods, stability analyses are typically performed assuming the post-drawdown pool level either at the low-level outlet or at the upstream toe as appropriate. It should be noted that a drawdown pool reduces not only external water support but also vertical driving force due to the weight of water. As such, the critical drawdown pool level, which would yield the lowest factor of safety, might differ from the traditional assumption of drawdown pool at the low-level outlet or at the upstream toe. Therefore, in order to investigate the variation of factor of safety with the drawdown pool levels and the critical drawdown pool level, a series of Slope/W analyses were performed with typical sections of an earthfill embankment. Both single-stage and multi-stage methods were used with the results presented in this paper. This study concludes that the traditional assumption of drawdown pool at the low-level outlet or at upstream toe, may not always represent the critical scenario. The analyses also showed that the critical drawdown pool level varies with embankment geometry and characteristics of embankment/foundation soils. Thus, it would be more appropriate to evaluate the drawdown stability and associated lowest factor of safety thru additional analyses performed with varying drawdown pool levels.

    Keywords: Rapid Drawdown, Critical Pool Level, Dam Safety, and Stability

    Critical Pool Level for Drawdown Analysis of Earth Embankment Dams

    Reliability Underseepage Assessment of Levees Incorporating Geomorphic Features

    Tuesday May 01, 2018 3:30 PM - Tuesday May 01, 2018 5:30 PM

    • Lourdes Polanco Boulware, Utah State University ;
    • John Rice, Utah State University

    Levee foundations along meandering rivers are often modeled in seepage analyses with simplified models that allow for use of simplified reliability methods. Due to the complex geomorphic environment that is often encountered in the fluvial environment and curvature alignment, levee foundation geometry can range from simple to very complex. Geomorphic features in the soil layers underlying a structure often have a significant effect on the underseepage behavior and the potential for initiating internal erosion. Based on the hypothesis that levee underseepage susceptibility comes from localized subsurface geomorphic features that interrupt the characteristic profile along that levee reach, methodology has been developed that assesses the hydraulic effect of geomorphic features in levee underseepage reliability. The methodology consists of a response surface-Monte Carlo analysis that takes into account the uncertainty in the subsurface geometry and soil properties in assessing the seepage regime associated with the feature. The method utilizes three-dimensional steady-state finite-element underseepage analyses to develop a response surface representing the relationship between soil properties and the three-dimensional levee foundation. The response surface then serves as the driving function for reliability analyses by means of Monte Carlo simulation analyses, resulting in cumulative probability functions for either hydraulic exit gradient or factor of safety against heave. These computed probability functions represent an assessment of conditional probability of initiation of internal erosion. Results can be adjusted for curvature effects when needed. The analysis of a crevasse-splay, an abandoned channel, and a meander scroll feature found in the Sacramento River (east side) levee system in California are presented as application examples.

    Reliability Underseepage Assessment of Levees Incorporating Geomorphic Features

    Parametric Study of Levee Saturation for Undrained Rapid Drawdown Analysis

    Tuesday May 01, 2018 3:30 PM - Tuesday May 01, 2018 5:30 PM

    • Kalie Poston, Tennessee Tech University ;
    • Prince Turkson, Tennessee Tech University ;
    • Daniel VandenBerge, Tennessee Tech University

    As infrastructure continues to age and natural disasters highlight weaknesses in this infrastructure, there has been an increased focus to analyze levees for rapid drawdown (RDD) failure; however, practitioners are lacking the guidance to do so.  Geotechnical engineers have typically used multistage undrained methods to analysis the RDD condition in dams.  In order to analyze the RDD condition for a levee with multistage undrained methods, the likely saturated zone within the levee must be determined, followed by the shear strength for both the saturated and unsaturated zones.  The saturated zone can be estimated using transient seepage analysis.  However, as there are more than 100,000 miles of levees in the United States alone, it is impractical to perform transient seepage analyses for multiple flood scenarios along every levee reach.  Taking into account the considerable extent of levee reaches and the variance in material properties, levee geometry, and flood scenarios that may be experienced, it would be beneficial to have a quick and simple method to determine the approximate extent of the saturated zone within a levee at the end of a flood (i.e., the start of drawdown).  In support of this broader goal, a chart-based method is presented that can be used to quickly estimate the saturated zone in a levee following a flood based on the soil properties, flood hydrograph, and levee geometry.  This saturated zone can then be used as a starting point for undrained RDD analysis.

    Parametric Study of Levee Saturation for Undrained Rapid Drawdown Analysis

    Transient SEEP2D for Finite Element Seepage Modeling of Levees with Enhanced Features

    Tuesday May 01, 2018 3:30 PM - Tuesday May 01, 2018 5:30 PM

    • Fred Tracy, Information Technology Laboratory, Engineer Research and Development Center, US Army Corps of Engineers ;
    • Lucas Walshire, ERDC, Vicksburg, MS ;
    • Maureen Corcoran, Geotechnical and Structures Laboratory, Engineer Research and Development Center, US Army Corps of Engineers

    SEEP2D is a steady-state finite element program in the Groundwater Modeling System that has been used extensively by practicing engineers all over the world. A transient version of SEEP2D has been developed and will be described in this paper. Transient SEEP2D features include (1) the ability to model hysteresis in soils in the unsaturated zone, (2) the ability to write to a file certain output variables at specified times, and (3) the ability to predict the time needed to achieve a given percentage of the output variables’ respective steady-state values. These output variables include (a) a saturation coefficient that varies between 0 and 1 which measures how saturated the levee is, (b) total head at specified nodes, (c) vertical exit gradient at specified node pairs, (d) flow rate through the landside boundary, and (e) position of the phreatic surface at specified x coordinates. Results from a sample levee will be shown to illustrate the features in transient SEEP2D, and the advanced features of the saturation coefficient, the time to achieve a given percentage of steady state, and hysteresis will be given detailed explanation.

    Transient SEEP2D for Finite Element Seepage Modeling of Levees with Enhanced Features

    Poster Session

    Flood Risk Management during a Dam Safety Modification

    Tuesday May 01, 2018 5:30 PM - Tuesday May 01, 2018 7:30 PM

    • D. Wade Anderson, P.E., U.S. Army Corps of Engineers, Tulsa District ;
    • Kathryn White, P.E., U.S. Army Corps of Engineers, Southwestern Division, Dam Safety Production Center ;
    • Bobby Van Cleave, P.E., U.S. Army Corps of Engineers, Southwestern Division, Dam Safety Production Center ;
    • Daniel Morales, P.E., U.S. Army Corps of Engineers, Southwestern Division, Dam Safety Production Center

    Modifying existing dams offers many challenges. Some of which are quite different than building a new dam. The ability of the dam to continue to support it's authorized purposes and the risk of poor performance due to these operations during the construction of the modification often influence the decision on the features of the modification or sequencing of the modification.  Some considerations include:  

    Risk from High Water During Construction,

    Flood Water Management during Construction,

    Continued Operations to meet all Purposes,

    Impacts of High Water on Construction, and

    Surveillance & Monitoring

     

    Potential Impacts to construction include:

    Pool Restrictions or Operational Changes,

    Construction/Contract Sequencing,

    Cofferdams,

    Dewatering/Unwatering,

    Haul Roads,

    Borrow Areas,

    Surveillance & Monitoring, and

    Delays/Suspension of Construction Work

     

    The Southwestern Division of USACE has completed or is completing major dam safety modifications on four projects. The operational and flood risk management decisions, designs, construction requirements, and construction sequencing will be presented for each of these projects.

    Flood Risk Management during a Dam Safety Modification

    Consequence Assessment to Support the Mactaquac Dam Safety Risk Analysis

    Tuesday May 01, 2018 5:30 PM - Tuesday May 01, 2018 7:30 PM

    • Michael Crouch, Research Triangle Institute (RTI) International

    Research Triangle Institute (RTI) International was tasked with performing a series of US Army Corps of Engineers (USACE) Hydrologic Engineering Center Flood Impact Assessment (HEC-FIA) simulations to assess the potential for consequence downstream of Mactaquac Dam for an overtopping dam breach. The consequence assessment supports a dam safety risk assessment that is currently being conducted by Stantec and RAC Consultants to ensure that the dam meets Canadian Dam Safety (CDA) guidelines. The HEC-FIA program is a standalone module that uses HEC-RAS output along with a multitude of Geographic Information System (GIS) layers to compute potential consequences, including life loss that may occur during flood events. The poster will focus on the required inputs and detail factors that influence life loss results including interviews with downstream emergency management officials and the interview’s importance in determining warning dissemination and the population’s mobilization out of the flood hazard area. Calibration of the model’s life loss computation to the historic flood of record will be covered. In addition, RTI has proposed to develop life loss and economic consequences results using the recently released HEC-LifeSim software to support the next phase of the risk assessment. The poster will also focus on the differences in the two model approaches and touch on the uncertainty capabilities within HEC-LifeSim.

    Consequence Assessment to Support the Mactaquac Dam Safety Risk Analysis

    Suspended-Sediment-Concentration Measurement and Freeze-Core Sediment Sampling: Development, Design and Evaluation Testing of two Innovative Techniques

    Tuesday May 01, 2018 5:30 PM - Tuesday May 01, 2018 7:30 PM

    • Yannick Dück $lastName ;
    • Christian Jokiel $lastName

    Studies on reservoir sedimentation are indispensable in the field of water resources management for a number of reasons, such as the loss of storage volume or ecological aspects. Obviously the knowledge of both, the quantity and the quality characteristics of the sediment trapped in a reservoir is the key to develop and implement suitable counter measures for reservoir restoration. Working on various reservoir restoration projects we found that although a wide range of sediment sampling devices exist there still seems to be a lack of reliable, economic viable and robust sediment data acquisition techniques.

    In this paper, we describe the advantages and disadvantages of state-of-the-art technologies for suspended-sediment concentration (SSC) measurement as well as sediment sampling techniques. Based on this research, we developed, built and tested innovative techniques to significantly reduce time, workload and costs for sediment data assessment. As a result a simple and robust technique to measure suspended-sediment concentration (DENSE) and a device to take undisturbed sediment samples were developed and successfully applied.

    The DENSE (DENsiemeter for Semi-continuous SSC Measurements) is an innovative and patented measurement device to evaluate the SSC, based on the automatic measurement of a water sediment sample’s density. Laboratory experiments proved that the DENSE is a reliable device for SSC measurement at high concentration values (up to 40 g/L) with an accuracy of 0.33 g/L.

    For sediment sampling, a simple and robust freeze corer, which freezes the sediment inside of a double-walled pipe, was developed. Laboratory and field experiments have been carried out to quantify the disturbance and shortening of the sediment during penetration and to evaluate the effect of the change in temperature during the coring process.

    Within this paper both innovative devices will be presented in detail (design, installation, verification) and their application in various field studies.

    Suspended-Sediment-Concentration Measurement and Freeze-Core Sediment Sampling: Development, Design and Evaluation Testing of two Innovative Techniques

    OPTIMIZATION OF HYDRAULIC STRUCTURE INSPECTION INTERVALS USING REINFORCEMENT LEARNING: PART I - OVERVIEW

    Tuesday May 01, 2018 5:30 PM - Tuesday May 01, 2018 7:30 PM

    • Travis Ford, HDR

    Appurtenant hydraulic steel structures such as spillway gates are subject to deterioration over time. Similar asset deterioration occurs on construction equipment, vehicles, bridges and building components. This paper extends the use of Markov Decision Processes (MDP) for hydraulic steel structures and adds partial observability. The primary intent of this paper is to determine whether an optimum policy for inspection intervals and maintenance for spillway gates could be approximated by a Partially Observable Markov Decision Process (POMDP). This work is a follow-on to the Master of Science Report work performed in 2017 at University of Colorado by Travis Ford, P.E. This is the first overview paper of a series exploring features of the POMDP modeling.

    This work explores the application of algorithms born in the artificial intelligence (AI) industry applied to hydraulic steel structure asset management. Specifically, the use of a Partially Observable Markov Decision Process applied to deterioration of radial (Tainter) gates on dams. POMDP’s are a fundamental process in the reinforcement learning branch of AI. Recent advances in computing power and algorithms has provided better tools to solve large infrastructure problems. The fundamentals include structural inspection, structural deterioration, maintenance activities, maintenance intervals, and condition states. Optimizing inspection intervals depends on much more than just the condition of the structure.

    The primary conclusions of this research includes: Regional deterioration, Spike in cracking damage between 1945 and 1960 due to advent of welding, economy of scale for inspection and retrofit, tradeoff between inspection methods, strategies for structure longevity, sensitivity with discount factors, and cost vs. risk tradeoff. A few of these will be highlighted here with follow-up discussion in future publications.

    OPTIMIZATION OF HYDRAULIC STRUCTURE INSPECTION INTERVALS USING REINFORCEMENT LEARNING: PART I - OVERVIEW

    Ring Levee Certification Case Study – A Complex Hydrologic and Hydraulic Approach to Interior Drainage

    Tuesday May 01, 2018 5:30 PM - Tuesday May 01, 2018 7:30 PM

    • Brandon Hilbrich, HDR ;
    • Nate Dalager, HDR

    The City of Pembina (City), North Dakota, is located at the confluence of the Pembina River and Red River of the North (Red River), and is surrounded by a ring levee which has historically provided protection against flooding. The flood protection system was designed by the U.S. Army Corps of Engineers (USACE) and construction was completed in August 1976. Following completion of the levee system, the City was protected from the 1-percent-annual-change (1% AC) flood as reflected by the Federal Emergency Management Agency (FEMA) Flood Insurance Rate Maps (FIRMs) and is currently designated as a Zone X (Area Protected by a Levee).

    In 2009 FEMA notified the City of its intent to require levee certification documentation within two years to maintain its status as a community removed from the floodplain and protected by a levee system. During this two year period, the levee system was labeled as a Provisionally Accredited Levee (PAL). In the years following the receipt of that letter, the City has taken measures to address the system deficiencies and document compliance with 44 CFR 65.10.

    HDR has been working for the City for the last 7 years to complete a Letter of Map Revision (LOMR), a Levee Recertification package, and revising the interior floodplain mapping associated with coincident flood and rainfall events. 

    The interior floodplain remapping effort provided an opportunity to re-evaluate interior drainage from a holistic approach incorporating full dynamic two-dimensional modeling to more accurately simulate the interaction between surface storage, subsurface drainage systems, and the pumping system. This presentation will discuss the modeling approach used to update the interior flood mapping limits, discuss differences to the original 1971 interior drainage analysis, and summarize major changes in results based on a more detailed approach using the best available data.

    Ring Levee Certification Case Study – A Complex Hydrologic and Hydraulic Approach to Interior Drainage

    Best Practices for Soil Drilling, Sampling, and Logging of Borehole Subsurface Explorations

    Tuesday May 01, 2018 5:30 PM - Tuesday May 01, 2018 7:30 PM

    • Richard Keizer, GEI Consultants, Inc. ;
    • Emilie Singleton, GEI Consultants, Inc. ;
    • Robert Jaeger, GEI Consultants, Inc.

    Soil drilling, sampling, and logging of subsurface explorations are time consuming, expensive, and critical in developing a thorough understanding of subsurface conditions in geotechnical engineering. Understanding and implementing best practices in soil drilling, sampling, and logging is important to obtain high-quality data and boring logs. However, there is large variability in the practice of soil drilling, sampling, and logging amongst engineers. Often, recent engineering graduates with little to no logging experience are tasked with logging borings and important details can be missed.

    This paper documents suggested best practices for activities before, during, and after soil drilling, sampling, and logging of borehole subsurface explorations. Specifically, this paper covers the following topics: (1) communication with the project manager, necessary parties responsible for site access, and the drillers; (2) applicable government agency requirements for an exploration program; (3) documentation and communication points that should occur onsite before drilling begins; and (4) details to document during drilling and sampling operations, as well as key documentation and review practices upon completion of drilling and logging.

     

    Best Practices for Soil Drilling, Sampling, and Logging of Borehole Subsurface Explorations

    Influence Factors on Discharge Capacity of PVDs for Improving Weak Foundations of Dam

    Tuesday May 01, 2018 5:30 PM - Tuesday May 01, 2018 7:30 PM

    • Jintae Lee, WA State Department of Ecology, Dam Safety Office ;
    • Dongwook Kim, Incheon National University, Department of Civil and Environmental Engineering

    Prefabricated vertical drain (PVD) method is one of the representative and commonly used ground improvement techniques to accelerate the consolidation settlement of weak foundation soils on construction site. The main purpose of this study is to investigate the influence factors on discharge capacity of PVDs for improving weak foundation soils of dam. A series of discharge capacity tests in laboratory was conducted using different types and geometries of PVDs in regards to lateral pressures, hydraulic gradients, elapsed times, and deformation of drains. Four different types of drain samples were selected among PVDs generally used in the field. Cylindrical consolidation tests with PVDs were also conducted. In this study, finite differential method (FDM) was adopted in order to solve two-dimensional consolidation and compare the numerical analysis with test results. The soil disturbed zone around the vertical drain caused by PVD installation was considered for parameter study on the smear zone and transition zone. The discharge capacity of PVD is dependent on the shape of core, tensile strength of filter, lateral pressure, deformation of drain sample, and elapsed time. For the accurate measurement of discharge capacity in laboratory, it is recommended to use PVD surrounded by clayey soils to simulate similar field condition. In addition, continuous measurement of discharge capacity is required because the discharge capacity is highly dependent on the elapsed time. Consolidation time with drains was about four to five times faster than that without drains. From the numerical analysis, it is shown that the degree of consolidation considerably decreased due to the development of both smear zone and transition zone. The consolidation time is highly affected by the variation of smear zone rather than that of transition zone of weak foundations.

    Influence Factors on Discharge Capacity of PVDs for Improving Weak Foundations of Dam

    Indian Lake Dam Rehabilitation - Not Your Ordinary Labyrinth Spillway Design

    Tuesday May 01, 2018 5:30 PM - Tuesday May 01, 2018 7:30 PM

    • Frederick Lux III, Stantec Consulting Services, Inc. ;
    • Rob Kirkbride, PE, Stantec Consulting Services Inc. ;
    • Mark Seidelmann, PE, Stantec Consulting Services Inc. ;
    • Eric Reeves, PE, Stantec Consulting Services Inc. ;
    • Brandon McNeal, PE, Stantec Consulting Services Inc. ;
    • Greg Smith, Stantec Consulting Services Inc.

    The Indian Lake Dam, owned by Ohio DNR and located near Lakeview in western Ohio, creates Indian Lake, the principal feature in Indian Lake State Park. The 150+ year old, canal system dam needed rehabilitation to address inadequate spillway capacity, severe concrete deterioration of the 700-foot-long ogee concrete spillway, and seepage at the embankment toe.  The embankment seepage was addressed with a toe drain and flatter downstream slope.  The primary focus of this paper will be the replacement of the ogee spillway with a two-stage, 701.5-foot-wide labyrinth spillway.

    Current hydraulic design of labyrinth spillways follows the Crookston method (2012), which was used initially for this project.  The method was modified for the special conditions and constraints imposed on the spillway design including:

    • No change in downstream discharge rating curve was mandated up to the 100-year flood per State requirements.
    • High tail water on the spillway due to a road bridge immediately downstream causing early submergence of the labyrinth spillway.
    • Relatively flat topography surrounding the lake limiting the available head for the spillway.
    • Redirection of flow exiting the 701.5-foot-wide labyrinth into a 160-foot-wide bridge opening.
    • Assessment of a historic dam considering refurbishment or replacement of the spillway.
    • Working in a disturbed foundation from the old spillway construction.
    • Construction considerations regarding crest shape, length and elevation of the two stage weir, overflow considerations to mitigate noise and vibration on the downstream apexes, concrete mix and temperature issues, and erosion control and shaping of the downstream channel.
    • Cofferdam considerations and sequencing.

    Indian Lake Dam Rehabilitation - Not Your Ordinary Labyrinth Spillway Design

    THE EVOLUTION OF FOUNDATION MAPPING TECHNIQUES

    Tuesday May 01, 2018 5:30 PM - Tuesday May 01, 2018 7:30 PM

    • Rafael Morales, US- Army Corps of Engineers - Jacksonville District

    Since the 1990's, foundation mapping within the Jacksonville District, U.S. Army Corps of Engineers (SAJ), has evolved in both collecting and data processing techniques. The level of detail needed from mapping varies from project to project and with each progressive event, technology has allowed for improved efficiencies and products. SAJ, along with the Community of Practice, have embraced technology, such as the use of Unmanned Aerial Vehicles (UAV’s) and advanced software to obtain the information necessary for a successful project.

    SAJ has been involved with foundation mapping for large concrete and RCC dams that started with the classical mapping by crews with hand drawn maps capturing every change in geology along with concurrent strikes and dips that were digitized into Microstation. Mapping then developed into the use of photogrammetry which reduced the time mapping and increased accuracy but was time consuming taking the photos from an extension pole. With the onset of UAV technology, foundation mapping has become even more efficient. Mapping is still ground truthed with the geology identified, however, the use of a UAV to photograph takes only minutes. Post–processing utilizing survey data, creates a geospatially referenced mosaic that can be uploaded into SIMDAMS. SAJ has utilized UAV technology at the HHD mega-dam project for culvert replacement foundation mapping and at the C-44 reservoir construction project foundation mapping where approximately 10 miles of foundation is being mapped for embankment dam construction.

    THE EVOLUTION OF FOUNDATION MAPPING TECHNIQUES

    ENHANCING DAM SAFETY IN THE CITY OF DALLAS

    Tuesday May 01, 2018 5:30 PM - Tuesday May 01, 2018 7:30 PM

    • Jason Vazquez, Arcadis ;
    • Kimberlie Brashear, Dallas Water Utilities ;
    • Gail Charles, Arcadis ;
    • Kimberly Dewailly, Trinity Watershed Management

    Agencies responsible for water resources face formidable water management challenges, including protecting against flood risks, safeguarding a healthy water supply, and developing and maintaining water conveyance and transport systems. The City of Dallas owns and operates 24 dams that serve the public by impounding water supplies and storing flood waters, while also providing recreational and environmental benefits. The dams are operated and maintained by the Dallas Water Utilities (DWU), Trinity Watershed Management (TWM), and the Park and Recreation (Parks) departments. The Texas Commission on Environmental Quality (TCEQ) regulates the safe and reliable operation of non-federal dams in the State, and classifies dams based on size and the potential for downstream flood impacts from dam operations.

    The City’s dam safety program is managed by a combination of operations, engineering and management staff throughout city departments. The City departments must also coordinate regularly with external agencies including the U.S. Army Corps of Engineers (USACE) and the U.S. Geological Survey (USGS).

    The City engaged Arcadis to perform a comprehensive assessment of their current dam safety programs with respect to State regulations for high hazard dams in Texas as an investment in their infrastructure and water supply management resiliency. The project involved performing dam inspections, generating detailed inspection reports with prioritized recommendations, updating the O&M manuals, classroom and field training, updating the Emergency Action Plans (EAPs) and conducting exercises to improve response coordination using the GIS-based tool developed for evaluating potential inundation areas.

    This paper discusses how the project improved resiliency though streamlining the dam safety program to more effectively manage City assets. Interdepartmental communication was promoted in an attempt to improve the City’s Community Rating System (CRS) score, as administered by the Federal Emergency Management Agency (FEMA), and to clarify responsibilities for the City’s dam safety program.

    ENHANCING DAM SAFETY IN THE CITY OF DALLAS