Short course for UNIVERSIDAD NACIONAL DE INGENIERIA January 26-29, 2016
Planning and Design for Rehabilitation of Rivers Using Large Wood Metodología para Reforestar Ríos Degradados por Actividades Humanas usando Técnicas de Bioingeniería
11.0 Considerations for implementation
Course overview Day I (Jan 26)--Foundational topics • Review of information resources (design handbooks and spreadsheets) for large wood • Is wood appropriate for your site?—criteria for screening (Planning) • Three design approaches • Key issues for large wood design
Day 2 (Jan 27)—Designing large wood structures • Case study I—Little Topashaw Creek, Mississippi • Design life for wood structures/selection of design event or condition
Day 3 (Jan 28)—Risk, uncertainty and construction • Sensitivity and Monte Carlo analyses
• Constructability assessment • Case study II—Trinity River, California • Monitoring
Day 4 (Jan 29)--Field trip
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• Introductions
• Types of wood structures • Findings of recent research on drag and lift coefficients • “Road testing” selected design spreadsheets
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• Sources of LW • Protection of harvested LW while moving and installing • Protection for existing LW and riparian features • Equipment types, sizes, access • Scheduling (seasons, hydrologic events) • Ramps and roads • Safety plans and considerations
Photo courtesy Natural Systems Design
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Subject your design to a constructability assessment
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• Safety for construction personnel • Permits and agreements • Constraints due to existing infrastructure and utilities • Material availability • Equipment availability and capability • Site and staging area access for various types and sizes of equipment • Labor requirements
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Constructability Issues
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• Dewatering requirements and trafficability for equipment • Sequencing and seasonal restrictions that include, but are not limited to, these: • Optimal periods for material sourcing • Trafficability properties associated with wet or frozen soils • Migratory/breeding period constraints • Turbidity control and in-water work windows • Flooding and site dewatering issues
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More Constructability Issues
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More Constructability Issues • Limiting impact zones by working from banks, platforms, or gravel bars • Using special equipment • Avoiding sensitive soils and vegetation
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• Measures to protect habitat and water quality, such as these:
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Wood material transport options
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• Scheduling implementation events and obtaining required permits. • Informing landowners and other stakeholders/ • Securing site access and easements • Locating utilities • Confirming sources and quality of large wood, plant materials, and other materials. • Prebid meeting • Contractor selection • Contract type
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Steps in Project Implementation
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Options for contractual arrangements • Fixed price • Cost reimbursement • strong accounting for time, materials, equipment
• Equipment rental • Project owner/agency assumes all responsibility for outcomes
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• highly detailed plans and specs
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• Mobilization and demobilization • Pollution and erosion control • Removal of structures (if necessary) • Site preparation (haul roads/staging areas) • Large wood sources and harvesting • Large wood transport
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Typical Specifications
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• • • • • •
Excavation Fill Quality Control Large wood placement Site closure and cleanup Revegetation
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More on Typical Specifications
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• A wood sourcing plan should be developed during design • Sourcing plan should specify harvest locations and equipment, hauling and loading equipment, and stockpile or staging locations • Wood sourcing may be secured through a different contract • Offsite sourcing is challenging and may require a timber harvest plan or environmental compliance documents. Soils and invasive species a concern
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Wood sourcing options
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• • • • • •
Construction oversight Dewatering and diversion Excavation Wood placement Securing Wood Finish work
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Key Elements of Construction
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• • • • • • •
Barrier installation Fish removal Excavation Large wood placement Sediment and turbidity control Rewatering Re-engaging isolated work zones and putting the design feature “on-line” with the active river
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Sequencing Plan
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• Working in dry conditions • Working in wet, but controlled conditions and • Working in existing (wet) conditions, not controlled
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Water Management
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• Rerouting of the stream through a bypass channel • Blocking flows upstream and bypassing water through pipes using pumps or a gravity system • Isolating a portion of the site using cofferdams or pushup dikes
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Dewatering and Diversion
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• • • • • • •
Construction of Push-Up Berms Sand Bagging Water Filled or “Aqua Barriers” Highway Traffic Barriers Turbidity Curtains Pumps Gravity Bypass
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Turbidity Control Techniques
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• • • • • •
Depth of Excavation Site Hydrology Existing Soils Backfill Location of Equipment Existing Vegetation
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Excavation for LW placement
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• • • •
Native alluvium Imported rock Rock collars Dolosse
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Ballast Options for Large Wood Structures
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Driving piles Courtesy T. Abbe, Natural Systems Design
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Courtesy D. Bandrowski, Yurok Tribe
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• Recall emphasis in early parts of this course on resiliency and sustainability • Revegetation may determine ultimate success or failure • Revegetation requires a much different mindset than other types of construction engineering
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Revegetation
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Planting willow cuttings in sandbars
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• Even the best planning and design can be entirely negated by shoddy construction work. • A variety of contractual arrangements are available for procuring implementation services. Because construction contracts often result in litigation and distribution of risk varies with the type of contract, personnel involved in implementation should seek legal counsel and review of contracting arrangements. • Maintaining a daily log is an important part of implementation project management. The log should include photos from fixed points and notes regarding materials, equipment, personnel, and conversations with contractors. • A wood sourcing plan should be developed during project design to allow adequate lead time.
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Key points regarding implementation
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More key points • Substantial regional variations exist in requirements for mitigating project impacts on water quality (turbidity), aquatic habitat, and fish or other organisms. Temporary crossing structures are sometimes used to reduce heavy equipment impacts on streambeds. • Key construction steps include excavation, wood placement, and securing wood. Risks may be reduced by careful selection of appropriate equipment and methods for each step. • Large wood projects are complex from a safety management standpoint because they combine potential hazards incurred by logging, construction, amphibious operations, and non-ideal weather conditions. It is advisable to require Job Hazard Analyses for each phase of work and a site-specific safety plan. • The effects of a large wood project will often be temporary without some level of adjustment, adaptive management, or maintenance.
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• Water management is a key issue in implementation. Available approaches may be categorized as working in the dry conditions, working in wet but controlled conditions, and working in uncontrolled wet conditions. Working in the dry requires dewatering or diversion.
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