Documentales completos en español Megaestructuras Sorprendentes Destructor de Presas TVE2

The Demolition of Marmot Dam: A Complex Engineering Challenge

Overview of the Marmot Dam Project

• The Marmot Dam, located in Oregon's Cascade Mountains, has been generating electricity from the Sandy River for nearly a century but is now considered outdated and obstructive to migratory fish.

• General Electric has decided to dismantle the dam and replace it with renewable energy sources like wind power, presenting significant engineering challenges.

• The demolition project is described as an experiment, involving a top-tier team including explosive engineers, scientists, and meteorologists.

Challenges in Dismantling the Dam

• The Marmot Dam stands five stories tall and spans nearly 60 meters wide; its removal requires careful planning due to its size and construction materials (22,000 tons of concrete and 90,000 kg of reinforced steel).

• To safely demolish the dam, a temporary dike will be constructed to divert river flow and create a dry work area before explosives are used for demolition.

Environmental Considerations

• After removing the dam, there is a major challenge in clearing 16 million tons of accumulated sediment that could block fish passage even after the dam is gone.

• Salmon populations have dramatically declined from 20,000 to about 5,000 due to various factors; their life cycle involves migrating back upstream to spawn after maturing in the ocean.

Timing and Execution Constraints

• The timing of the dam removal must coincide with low water levels in order to minimize impact on salmon migration; contractors face tight deadlines with only four months allocated for completion.

• Work must be conducted intensively—six or seven days per week—to meet project timelines while ensuring minimal disruption to local wildlife.

Construction Techniques

• The first phase involves constructing an upstream gravel and clay structure known as an ataguía (dike), which will contain river flow during demolition operations.

• This dike will be built atop five layers of sediment; pumps will extract water from sediments to stabilize this protective structure while allowing heavy machinery access across it.

Risk Management Strategies

• Maintaining control over water levels during construction is critical; any failure could lead to catastrophic flooding in work areas.

• The team faces risks associated with seasonal rainstorms that can significantly increase river flow beyond what temporary structures can handle.

Sediment Removal Concerns

• Gordon Grant evaluates potential issues related to sediment release once the dam is removed; loose sediments may obstruct fish pathways or bury salmon eggs.

Demolition of Marmot Dam: A Bold Plan

Overview of the Project

• General Electric has devised an ambitious plan to remove sediment from behind the Marmot Dam in a single operation, a method untested at this scale.

• Researchers from the University of Minnesota's Center for Land Surface Dynamics are tasked with creating a 13-meter model of the dam and surrounding river to simulate the demolition process.

Model Construction and Testing

• The model incorporates precise laser measurements, including sediment types like gravel and sand, ensuring accurate representation.

• The goal is to validate Portland General Electric's plan to flush out sediments post-dam removal using controlled river flow during autumn storms.

Challenges in Execution

• Controlling river flow with machinery poses significant risks; researchers aim to learn how to manage this dynamic through their miniature dam model.

• Initial tests involve simulating storm conditions while managing water flow, which will be more complex in real-life scenarios.

Real-Time Simulation Insights

• The team can manipulate water flow in their model but acknowledges that field teams will face unpredictable natural conditions.

• As water flows through the channel created by the model, it begins eroding simulated sediments effectively.

Concerns About Scale and Timing

• Questions arise regarding how well scaled models translate into real-world timing; factors like rainfall amount and flood depth complicate predictions.

• Researchers will introduce variations over weeks to refine their understanding of necessary water flow dynamics for effective sediment removal.

The Demolition Process Begins

Historical Context of Marmot Dam

• The second week of demolition marks a significant transition as workers expose the nearly century-old structure built in 1913.

• Historical accounts highlight that construction relied heavily on manual labor and local materials, showcasing engineering feats of that era.

Emotional Impact on Workers

• Veteran workers express mixed feelings about demolishing a structure they helped maintain; personal connections complicate professional duties.

Technical Preparations for Demolition

• Experts prepare for controlled explosions aimed at safely dismantling sections of the dam while minimizing risk during operations.

Execution Strategy for Controlled Blasting

• Demolition involves multiple phases with careful calculations determining blast locations and explosive quantities needed per section.

Environmental Considerations During Demolition

Salmon Rescue and Dam Demolition

The Impact of the Dam on Salmon Migration

• With the river separated from the dam, the salmon ladder is no longer functional and will be demolished, leaving summer salmon trapped in a pool after traveling thousands of kilometers to spawn.

• Doc Kramer, an expert in fish from Portland General Electric, describes the process as a "fish rodeo," where many people chase jumping fish with nets to safely return them to water.

Demolition Preparations

• As time runs out for the trapped salmon, Jerry's blasting team prepares explosives using a specific recipe: 1100 kg of ammonium nitrate and 680 kg of high-quality dynamite.

• The team ensures that all explosives are correctly placed and checked multiple times before proceeding with detonation preparations.

The Historic Blast

• Representatives from various sectors gather at a viewpoint to witness the demolition, emphasizing safety and precision in their plans.

• Jerry oversees final checks; they aim for complete destruction of concrete blocks during the explosion to facilitate removal.

Execution of Demolition

• Countdown begins as Peggy Fowler, president of General Electric, prepares for the blast. After months of preparation, Marmot Dam is about to be demolished.

• A total of 321 tons of explosives successfully remove the top layer of the dam structure.

Cleanup Operations Post-Demolition

• Following initial explosions, excavators and trucks work quickly to clear debris for further demolitions while aiming to recycle valuable materials like steel and concrete.

• Pneumatic hammers break down remnants from explosions; heavy machinery operates with precision under Scott Sorsa’s supervision.

Recycling Efforts

• Trucks transport debris for recycling; concrete is processed into smaller pieces suitable for road construction while metal is sent to a steel rolling mill.

• At Qashqai Steel Rolling Mill, scrap metal undergoes melting in an electric arc furnace powered by hydroelectricity sufficient for 50,000 homes.

Environmental Monitoring During Demolition

• As summer progresses, General Electric continuously monitors river health ensuring that upstream demolition does not harm fragile ecosystems.

Historical Context of Marmot Dam

• Built nearly a century ago for electricity generation from Sandy River water diverted through complex channels and tunnels leading to Roslyn Lake which stores enough water for power generation.

Demolition of the Marmot Dam: A New Era in Hydropower?

The Historical Context and Current Changes

• The absence of aerial photography did not hinder the creation of efficient systems for water capture and electricity generation, which were marvels of their time. However, times have changed significantly.

• General Electric plans to dismantle the entire hydrological system, replacing it with alternative energy sources, marking the end of an era.

Demolition Progress and Challenges

• John Esler, head of operations, expresses satisfaction with demolition progress; concrete and steel removal will take two more weeks before awaiting autumn rains to wash away sediment.

• The demolition reveals 16 billion kilograms of sediment behind the dam, creating a barrier that salmon cannot jump over due to its height.

• Corsa's critical role involves inspecting the cofferdam for leaks; any small issue could lead to significant problems if not addressed promptly.

Weather Dependency and Strategic Planning

• Scott is confident in maintaining site safety until a storm arrives that can effectively wash sediments downstream; they are working against time until October 15th.

• Despite calm river conditions now, past experiences show how quickly situations can change; caution is advised as river currents can become powerful unexpectedly.

Final Stages of Demolition

• After four months of work on Marmot Dam, teams have successfully removed much concrete and steel. They await a "perfect storm" to complete sediment removal during this final phase.

• Researchers from the University of Minnesota confirm that Portland General Electric's plan could succeed by controlling floodwaters through a specific opening in the cofferdam.

Critical Decision-Making Under Uncertainty

• Tim Leer emphasizes that choosing when to open a breach in the cofferdam is crucial; there’s only one chance to do it right during an impending storm.

• The project presents high stakes as timing decisions must be made carefully based on weather predictions—there’s no room for error once action is taken.

Meteorological Challenges Ahead

• National Weather Service tracks an early storm front; unusual weather patterns complicate predictions for rainfall intensity necessary for effective sediment displacement.

• Understanding whether sufficient rain will fall in a sensitive area like Sandy River poses challenges due to rapid changes in water levels following storms.

Risk Management Strategies

• Water levels are dangerously close to exceeding what the cofferdam can handle. If they rise too high without intervention, it could jeopardize equipment and control measures needed for sediment management.

• Project leaders face tough choices: either wait out current conditions or risk losing control by prematurely opening outlets in anticipation of stronger storms ahead.

Emergency Rescue Plan for Endangered Salmon

Overview of the Situation

• The movement of sediments during flooding is unpredictable, complicating rescue efforts. General Electric has an emergency plan to save vulnerable fish 29 kilometers downstream.

Salmon Rescue Mission

• Biologists from Oregon's Department of Fish and Wildlife are involved in a mission to collect 20 pairs of endangered fall Chinook salmon as part of the emergency plan.

• The eggs of these protected salmon could suffocate if sediment deposits occur in the river, prompting their transfer to Sandy hatchery for artificial fertilization.

Crisis Development

• A storm front causes significant flooding, pushing the dam to its capacity with a flow rate reaching 1900 cubic feet per second (54 cubic meters per second).

• This flow rate is critical; exceeding it could lead to dam failure, raising concerns about structural integrity.

Structural Concerns and Challenges

• A bridge near the diversion channel is sinking by 30 centimeters, jeopardizing access for machinery needed for rescue operations.

• With the guide isolated and machinery inaccessible, time becomes a crucial factor as conditions worsen.

Weather Forecast and Urgency

• Meteorologist Andy Landin reports a new storm front that could escalate water levels significantly by evening.

• The forecast predicts river levels rising to 2500 cubic feet per second, necessitating immediate action on the emergency plan.

Implementation of Emergency Measures

• Heavy machinery cannot be used due to bridge instability; workers must improvise using lighter equipment like forklifts.

• Workers face risks while attempting to extract pumps from the dam before water begins penetrating its structure.

Final Stages of Operation

• As pumps are disconnected, there’s urgency in assessing dam integrity; seven pumps remain at risk as river levels continue rising.

• With each passing minute weakening the structure further, Gordon Grand arrives to evaluate whether laboratory models can predict real-world outcomes effectively.

The Final Phase of the River Project

Opening the Breach

• The last phase involves cutting through the dam, allowing water to flow. This moment signifies a critical transition where human control diminishes, and nature takes over.

• The diversion channel acts as a safety valve, regulating water flow. However, once blocked by the team, it will unleash powerful forces.

Team Dynamics and Concerns

• Mark Burnett expresses concern about the stability of the ground beneath him while operating heavy machinery. There is an underlying tension regarding potential collapse.

• Workers are instructed to close the drainage channel quickly, increasing water flow over the dam significantly.

Critical Flow and Geological Impact

• As water reaches critical flow—akin to breaking the sound barrier—it begins to erode sediment with immense force, marking a pivotal geological event.

• After opening the channel, sediment starts collapsing rapidly; this moment is described as one of intense difficulty for the team.

Observing Nature's Power

• The collapse transforms sediments into a torrent of gravel and sand. A remarkable canyon forms as nature reclaims its path.

• Two hours post-opening, river flows return to their original course where a dam once stood. The sound resembles that of a waterfall—a spectacular natural phenomenon.

Reflection on Success and Recovery

• By dawn after completion, all traces of human intervention have vanished overnight; it’s as if nature has erased any memory of the dam.

• In just 18 hours since breaching, approximately 98 thousand tons of sediment have been washed away. The area is set to become a national wildlife reserve.

Signs of Ecological Restoration