They may ask for any site plans, specifications or bathymetric readings you may be able to email in for review. In order to understand timelines and lead times, they will want to know when you will need the turbidity barriers on site. They may ask what site requirements there are, or what engineering specs you have been asked to follow, if any. Let’s look at the criteria for selection in a little more detail.1. Water Body: Is the curtain going to be deployed into a river, lake, pond, stream, or in the ocean? The type of water is important for several reasons. If the barrier will be deployed in fresh water, galvanized components and standard materials should be acceptable for shorter term projects. However, if there are contaminants or if it will be used in salt or brackish water, certain compatibilities may need to be considered. Is the bottom silt? What depth? Sand, or rocky bottoms may also change anchoring strategies. The water body type should prompt additional questions about conditions where the curtain will be deployed.
2. Current: Your technical advisor is going to ask about water flow or the speed of the current where the barrier will be. What direction is the flow relative to the deployment area? Water speed is a significant factor in determining which type of turbidity barrier is required. Our team utilizes load-bearing calculation to help determine what forces will be present in your provided conditions. The velocity of the current in knots is measured against wind and wave measurements to help configure loading. The direction of flow determines the anchoring pattern that will hold the curtain in place. The velocity of the current contributes to the anchoring as well.
3. Waves: The velocity, frequency, type and size of the waves play an important part in curtain type selection. Typically, waves under two feet with moderate winds may allow the use of Triton Type 2 curtains. Faster water and waves of two feet or higher become a more highly engineered project. The load bearing for tension parameters with flotation (buoyancy), drape and weight are all considerations we take into account. The frequency is the timing between waves. As for the type, are they most often breaking waves? Swells? Rollers? All have a different impact on the way the barrier will behave in those conditions.
4. Wind: Wind speed, measured in knots, contributes to load bearing calculations as well, along with current direction, speed and wave height. Wind factors are considered for installation as well as performance and longevity in field.
5. Tides: Tidal water requires specific consideration for which type of curtain, and important accessories should be considered. If tidal swings are significant, then tidal compensators may be required as a sliding mechanism to help the barrier adjust to the varying water depths. In addition, barriers deployed in a tidal area often require more robust components, additional tension cables, and dual anchoring to keep the pre-determined curtain design stable against reversing currents. 6. Navigation: If the silt barrier will be placed in a body of water in which marine traffic is present, proper marine navigational LED lights, markers, reflectors and warning signs may be needed to help with visibility. In addition to adding proper safety accessories of this nature, the design or layout of the curtain may require adjustment and consideration for the flow of marine traffic. Often, curtain deployed in a high traffic zone cannot be stretched across a body of water, impeding traffic. A ‘baffle’ pattern may be suggested, where the silt barrier creates a number of ‘switchbacks’ for water to flow through and settle, but which also allows for the passage of boats.
7. Depth: Water depth and bottom conditions are important in determining the type of anchor that should be used. The Army Corps of Engineers recommends that silt curtain / turbidity barrier skirts remain 1’ (one foot) from the bottom surface at all times. In the tidal conditions above, considerations are made for accessories that can also help with the changing depth. Reefing lines can be purchased and installed during manufacture, which act as the cord on a sent of mini-blinds, furling and unfurling skirt according to different bottom depths. We can also make each section of curtain tailor-made for the area it will be deployed in, so that skirt depth ranges by section according to bathymetric readings of the bottom’s differing depths. Others choose standard sizing for the deepest depth required, then utilize factory-installed reefing lines to manually adjust curtain lengths to match varying depths. Reefing lines are recommended for skirts over 10’ in depth. The reefing lines make deployment, maintenance and removal much easier and more efficient. For skirt lengths over 10’ larger flotation is required.
8. Duration: If the water and site conditions warrant the use of lighter, small barrier types, the duration of the project may be another factor that may require a move to more robust components or fabrics. Most Type 1 projects require curtain that will be deployed for 6-12 months. Longer use will require review of project duration in conjunction with the other determining factors above.
9. Anchoring: Inarguably the single most important factor in the successful performance of any barrier project is proper anchor weight, frequency and positioning for the conditions. Whereas it is not a factor specific to choosing the type of curtain, the factors used to determine the right type of curtain – also determine the right kind of anchoring pattern, frequency and weight. Bottom type, depth, tide, current, wind, and marine traffic are just some of the factors to take into account. Our technical advisors can work with you to determine the proper anchoring required for selected barriers.
10. Accessories: Accessories may seem an afterthought, but the right accessories to match supplied product and conditions for use – can greatly reduce labor, wear, or damage to your silt barrier. Tow bridles help defray pulling force from a single point by evenly distributing forces along load-bearing components. Anchor kits are chosen to suit conditions and curtain types. Repair kits make in-field repairs possible, and fabrics and supplied materials should be compatible with site conditions and longevity requirements. Additional anchor points may need to be installed for applications where more aggressive anchoring is required. “T” connectors can be provided to join sections of curtain in particular patterns to create settling areas. Ground anchors can be provided for Type 1 curtain being deployed and anchored to shore or for in-water applications where depth considerations can be overcome. Hull connectors can be used to attach sections of barrier directly to a hull. Replacement connectors, spare sections, stainless steel components, zinc anodes and standoffs can also be supplied to suit the conditions of your site and the parameters of your project. Be sure to talk to our technical team to determine which accessories can make your job easier, less costly, and longer lasting!
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